Salmonella

Mutat Res, 2001 Feb 20, 490(2), 131 - 9
Oxidative mutagenesis of doxorubicin-Fe(III) complex; Kostoryz EL et al.; Doxorubicin has a high affinity for inorganic iron, Fe(III), and has potential to form doxorubicin-Fe(III) complexes in biological systems . Indirect involvement of iron has been substantiated in the oxidative mutagenicity of doxorubicin . In this study, however, direct involvement of Fe(III) was evaluated in mutagenicity studies with the doxorubicin-Fe(III) complex . The Salmonella mutagenicity assay with strain TA102 was used with a pre-incubation step . The highest mutagenicity of doxorubicin-Fe(III) complex was observed at the dose of 2.5nmol/plate of the complex . The S9-mix decreased this highest mutagenicity but increased the number of revertants at a higher dose of 10nmol/plate of the complex . On the other hand, the mutagenicity of the doxorubicin-Fe(III) complex at the doses of 0.25, 0.5, 1 and 2nmol/plate was enhanced about twice by the addition of glutathione plus H(2)O(2) . This enhanced mutagenicity as well as of the complex itself, the complex plus glutathione, and the complex plus H(2)O(2) were reduced by the addition of ADR-529, an Fe(III) chelator, and potassium iodide, a hydroxyl radical scavenger . These results indicate that doxorubicin-Fe(III) complex exert the mutagenicity through oxidative DNA damage and that Fe(III) is a required element in the mutagenesis of doxorubicin.

Rev Inst Med Trop Sao Paulo, 2001 Mar-Apr, 43(2), 67 - 74
Pyogenic abscesses and parasitic diseases; Lambertucci JR et al.; Parasitic diseases which during their course in the host switch the immune system from a T helper 1 to a T helper 2 response may be detrimental to the host, contributing to granuloma formation, eosinophilia, hyper-IgE, and increased susceptibility to bacterial and fungal infections . Patients and animals with acute schistosomiasis and hyper-IgE in their serum develop pyogenic liver abscess in the presence of bacteremia caused by Staphylococcus aureus . The Salmonella-S . mansoni association has also been well documented . The association of tropical pyomyositis (pyogenic muscle abscess) and pyogenic liver abscess with Toxocara infection has recently been described in the same context . In tropical countries that may be an interesting explanation for the great morbidity of bacterial diseases . If the association of parasitic infections and pyogenic abscesses and/or fungal diseases are confirmed, there will be a strong case in favor of universal treatment for parasitic diseases to prevent or decrease the morbidity of superinfection with bacteria and fungi.

J Nutr, 2001 May, 131(5), 1452 - 8
Elevated iron status increases bacterial invasion and survival and alters cytokine/chemokine mRNA expression in Caco-2 human intestinal cells; Foster SL et al.; Iron status affects both microbial growth and immune function . Mammalian iron homeostasis is maintained primarily by regulating the absorption of the micronutrient in the proximal small intestine . The iron concentration of the enterocyte can fluctuate widely in response to both dietary and whole body iron status, as well as in response to infections . The possibility that an enterocyte with an elevated iron concentration is more susceptible to invasion by enteric pathogens is not known . Therefore, we examined the impact of enterocyte iron status on the invasion and survival of an enteric pathogen, as well as on the levels of several cytokine and chemokine mRNAs by the host cell . The enterocyte-like Caco-2 human intestinal cell line and Salmonella enteritidis served as the models to examine the effect of iron on the host-parasite interaction . Iron status of Caco-2 cells was altered by incubation in serum-free medium supplemented with varying levels of iron . Elevated iron status of Caco-2 cells increased the efficiency of the invasion and the number of bacteria surviving in the intracellular environment . Caco-2 cells constitutively expressed transforming growth factor-beta1, interleukin-8, monocyte chemotactic protein-1, tumor necrosis factor-alpha and interleukin-1beta, and infection with S . enteritidis increased the relative quantities of all cytokine/chemokine mRNAs except interleukin-1beta . Elevated iron status of Caco-2 cells decreased the levels of cytokine/chemokine mRNAs by 25-45% in uninfected cells . In contrast, bacterial infection was associated with a 21-95% increase in cytokine/chemokine mRNAs levels in Caco-2 cells with higher iron concentration compared with infected cells with lower iron concentration . These data support the hypothesis that elevated enterocyte iron status increases susceptibility to infection and exacerbates the mucosal inflammatory response initiated by microbial invasion by increasing cytokine/chemokine expression.

J Nutr, 2001 May, 131(5), 1433 - 7
Alanyl-glutamine dipeptide does not affect hemodynamics despite a greater increase in myocardial heat shock protein 72 immunoreactivity in endotoxemic sheep; Scharte M et al.; The possible beneficial effect of supplemental glutamine (Gln) in critically ill patients has been suggested to be mediated by the induction of the cytoprotective heat shock proteins (HSP)32 and HSP72 . There is evidence that HSP72 and HSP32 have opposite effects on the hemodynamic situation during endotoxemia . Therefore, the effect of Gln supplementation on the cardiovascular system is not clear . We investigated the effect of alanyl-Gln (Ala-Gln) dipeptide on cardiovascular function in healthy and endotoxemic sheep . Ten sheep catheterized for chronic studies received Ala-Gln 700 mg/(kg x d) {equal to 470 mg/(kg x d)Gln} on 4 consecutive days, and 10 sheep received NaCl (9 g/L) as the control solution . On d 4, four sheep of each group were killed and myocardial samples were taken for immunohistochemistry . The remaining sheep received a continuous infusion of endotoxin {Salmonella typhosa, 10 ng/(kg x min)} . Hemodynamic parameters were measured before application of Ala-Gln or the control solution, and during endotoxemia . Myocardial HSP72 immunoreactivity was determined by immunohistochemistry . After 24 h of endotoxemia, the sheep exhibited a hyperdynamic circulation . No difference was found in the hemodynamic parameters between treatment and control group . Ala-Gln treated sheep had a greater increase in myocardial HSP72 immunoreactivity compared with controls after (P < 0.05) but not before endotoxemia . In summary, Ala-Gln increased HSP72 immunoreactivity after endotoxemia, but did not alter hemodynamic parameters . Thus, Ala-Gln supplementation does not seem to aggravate the hyperdynamic circulation in endotoxemic shock.

Infection, 2001 Mar-Apr, 29(2), 103 - 6
Salmonella encephalopathy with seizure and frontal intermittent rhythmic delta activity; Uysal H et al.; A 54-year-old woman was admitted to our clinic with frequent convulsions . Subsequently she developed a toxic look, rigidity, confusion and severe encephalopathy . Salmonella typhii was isolated from the blood cultures and she was diagnosed with Salmonella encephalopathy . The prominent electrophysiological finding was the frontal intermittent rhythmic delta activity (FIRDA) in electroencephalograph (EEG) . After treatment EEG revealed normal activity . The presence of FIRDA is not a specific finding but this kind of EEG change has not been reported before . Diffuse encephalopathy due to endotoxins might be the reason . We propose that S . typhii encephalopathy was the cause of FIRDA which is a sign of diffuse encephalopathy.

Food Addit Contam, 2001 Apr, 18(4), 329 - 41
Genotoxicity testing of extracts from aflatoxin-contaminated peanut meal, following chemical decontamination; Hoogenboom LA et al.; One of the most important concerns in the decontamination of aflatoxin-containing feed commodities is the safety of the products for food-producing animals and for human consumption of products derived from these animals . A new method, based on the use of florisil and C18 solid phase extraction columns, was developed for the preparation of extracts from decontaminated peanut meal, which allowed testing with in vitro genotoxicity assays without interference of the residual aflatoxin B1 . Recovery of degradation products in the extracts was evaluated by the use of radiolabelled {14C}-aflatoxin B1 (AFB1) added to naturally-contaminated peanut meal (3.5 mg AFB1/kg) . The meal was treated by a small-scale version of an industrial decontamination process based on ammoniation . Following decontamination, more than 90% of the label could not be extracted from the meal . AFB1 accounted for about 10% of the radiolabel present in the extractable fraction, indicating a total AFB1 reduction of more than 99% . Decontamination of the meal by a number of other small- and industrial-scale ammonia-based processes resulted in similar efficiencies . Application of the extraction procedure resulted in AFB1-rich and AFB1-poor fractions, the latter containing half of the extractable decontamination products but less than 1% of the residual AFB1 . Testing in the Salmonella/microsome mutagenicity assay (TA 100, with S9-mix) of the original crude extracts and AFB1-rich fractions prepared from non-treated and decontaminated meal, showed the positive results expected from the AFB1 contents as determined by HPLC analysis . Analysis and testing of the AFB1-poor fractions showed that the various decontamination processes not only resulted in a successful degradation of AFB1 but also did not produce other potent mutagenic compounds . Slight positive results obtained with these extracts were similar for the untreated and treated meals and may be due to unknown compounds originally present in the meal . Results obtained with an unscheduled DNA synthesis (UDS) and Comet assay with rat hepatocytes supported this conclusion . Positive results obtained with the micronucleus assay, using immortalized mouse hepatocytes (GKB), did not clearly reflect the mycotoxin levels and require further examination . It is concluded that the newly developed extraction procedure yields highly reproducible fractions and hence is very suitable for examining the possible formation of less potent degradation products of aflatoxins in short-term genotoxicity tests.

J Med Microbiol, 2001 May, 50(5), 415 - 20
An attempt to identify the evolutionary origin of a novel serotype of Salmonella enterica isolated from harbour porpoises; Old DC et al.; The isolation since 1991 of a new serotype of Salmonella enterica (antigenic formula 4,12:a:-) from harbour porpoises (Phocoena phocoena) at post-mortem examination raised the question of its evolutionary origin . Representative strains of S . enterica serotype 4,12:a:- and strains of eight other serotypes of serogroup 04 with phase-1 flagellar antigen H 'a' were examined by EcoRI ribotyping, IS200 fingerprinting and PCR-based profiling . Statistical analysis of results of multiple typing showed that strains of Salmonella serotype 4,12:a:- were genetically distant from those of antigenically similar salmonella serotypes, none of which seemed likely to be the progenitor of the 'porpoise' serotype.

Vestn Ross Akad Med Nauk, 2001, (2), 21 - 5
{Immunosuppressive effects of pathogenic gram-negative bacteria}; Vorob'ev AA et al.; The review deals with the Immunosuppressive effects of virulent gram-negative bacteria (Salmonella, Shigela, Pseudomonas aeruginosa), with the importance of these effects for the bacteria to survive in the infected body . The above bacteria affect the immunity system in a different way, yet have common features . They are characterized by the occurrence of endotoxin shock, by the suppression of the phagocytic system and cell-mediated immunity . A significant role in suppressing a cellular immune response is played by the lipopolysaccharide of virulent bacteria that greatly differs from that of nonvirulent strains . The immunosuppressive activity of the bacteria and their lipopolysaccharide is closely related to their virulent properties.

Vet Microbiol, 2001 Jun 6, 80(3), 267 - 74
Monitoring of transmission of Salmonella enterica serovars in pigs using bacteriological and serological detection methods; van Winsen RL et al.; The standard method to detect Salmonella positive pigs is bacteriological examination of the faeces, but in recent years the use of Salmonella-ELISA's have become available to screen pigs for serological evidence of infection . This study was conducted to monitor the transmission of five different Salmonella enterica serovars (S . Typhimurium, S . Brandenburg, S . Panama, S . Livingstone, and S . Goldcoast) in fattening pigs and to test the feasibility of Salmonella-ELISA, using seeder pigs as a mode of transmission . Serovar dependence in transmission was observed . The Salmonella-ELISA proved to be useful to detect S . Typhimurium and S . Brandenburg in herds but was of limited value to demonstrate S . Livingstone, S . Goldcoast, and S . Panama.

Vet Microbiol, 2001 Jun 6, 80(3), 235 - 45
The SEF14 fimbrial antigen of Salmonella enterica serovar Enteritidis is encoded within a pathogenicity islet; Collighan RJ et al.; The DNA sequence of the chromosomal gene cluster encoding the SEF14 fimbriae of Salmonella enterica serovar Enteritidis was determined . Five contiguous open reading frames, sefABCDE, were identified . The sefE gene shared significant homology with araC-like positive regulators . Serovar-associated virulence plasmid (SAP) genes orf7,8,9 and pefI were identified immediately adjacent to the sef operon . The pefI gene encoded a putative regulator of the Plasmid-encoded fimbrial antigen (PEF) expression . The entire sef--pef region, flanked by two IS-like elements, was inserted adjacent to leuX that encoded a transfer RNA molecule . The organisation of this region was suggestive of a classic pathogenicity islet . Southern hybridisation confirmed two copies of the SAP derived orf7,8,9 and pefI region in S . Enteritidis, one in the chromosome and one on the SAP . Of other group D Salmonella, only S . Blegdam and S . Moscow harboured both chromosomal and plasmid copies of pefI--orf9 region although polymorphism was evident.

Mutat Res, 2001 May 9, 476(1-2), 133 - 7
SAR modeling of genotoxic phenomena: the effect of supplementation with physiological chemicals; Rosenkranz HS et al.; Structure-activity relationship (SAR) modeling of toxicological phenomena is optimal when the ratio of toxicants to non-toxicants included in the model is unity . Frequently, however, the experimental data available are enriched with toxicants, this appears to be especially true for genotoxicity data sets . It is demonstrated herein, using a Salmonella mutagenicity data set, that when there is a paucity of non-toxicants, the learning set may be augmented with physiological chemicals on the assumption that they are non-genotoxic.

FEMS Immunol Med Microbiol, 2001 Apr, 30(3), 203 - 8
Flagellin expressed by live Salmonella vaccine strains induces distinct antibody responses following delivery via systemic or mucosal immunization routes; Sbrogio-Almeida ME et al.; Salmonella flagellin, expressed as flagella in live attenuated vaccine strains, elicits distinct systemic (IgG) and secreted (IgA) antibody responses in mice following delivery via mucosal (nasal/oral) or parenteral (intraperitoneal (i.p.)) immunization routes . Reduced flagellin-specific antibodies were detected either systemically or locally following delivery of flagellated derivatives of aroA Salmonella enterica serovar Dublin SL1438 via the nasal route, the most effective mucosal site for activation of immune responses in mice . In contrast, flagellin represents the most potent Salmonella antigen for the generation of specific serum antibody (IgG) responses following i.p . inoculations . The distinct immunogenic properties of Salmonella flagellin could not be ascribed to deficient colonization, reduced invasive ability or loss of the flagellin expression by the flagellated vaccine strains.

Int Microbiol, 2000 Dec, 3(4), 225 - 9
Detection of Salmonella in food samples by the combination of immunomagnetic separation and PCR assay; Jenikova G et al.; A combination of immunomagnetic separation and polymerase chain reaction (IMS-PCR) was used to detect Salmonella in food samples . Pre-enrichment of samples was combined with filtration through a membrane for the removal of food debris . The IMS-PCR assay combines selective extraction of bacteria by specific antibodies with primer specific PCR amplification that enables to detect Salmonella in non-fatty food samples in 24 h . In comparison with conventional cultural methods, the IMS-PCR is a rapid and specific method . Combined with filtration bags, it partially reduces the negative effects of the food matrix and allows the quick detection of Salmonella cells . The shortened protocols for Salmonella spp . detection described here can improve considerably current methodologies.

Neurosurgery, 2001 May, 48(5), 1152 - 6
Mycotic aneurysm of the carotid bifurcation in the neck: case report and review of the literature; Nader R et al.; OBJECTIVE AND IMPORTANCE: Mycotic aneurysms of the extracranial carotid artery are rare and difficult to diagnose . A search of the world literature published since 1966 reveals at least six cases of mycotic carotid aneurysms due to a Salmonella septicemia . We present an exceptional case of mycotic pseudoaneurysm of the bifurcation of the carotid artery due to Salmonella septicemia and discuss the pathogenesis as well as various aspects of the diagnosis and surgical management . CLINICAL PRESENTATION: A 68-year-old man presented in Poland with Salmonella sepsis; 1 month later, he was admitted to the emergency department of the Sir Mortimer B . Davis-Jewish General Hospital in Montreal with a bulky and pulsatile right cervical mass . An angiogram and a computed tomographic scan revealed a voluminous and partially thrombosed aneurysm the size of a tangerine originating from the posterior aspect of the carotid junction . INTERVENTION: Balloon trapping was attempted at the Montreal Neurological Hospital . Subsequently, the patient developed a significant neurological deficit, which was quickly reversed by the administration of hypertensive, hypervolemic, and hemodilution therapy . Thereafter, the pseudoaneurysm was resected surgically, and the internal and external carotid arteries were sacrificed . Pathological examination of the excised specimen of the carotid junction revealed a pseudoaneurysm . Bacterial culture of the lesion showed growth of Salmonella . CONCLUSION: The postoperative course was satisfactory except for laryngeal paralysis due to involvement of the vagus nerve . Four months later, a computed tomographic scan showed only small lacunae in both centra semiovale.

J Biomater Sci Polym Ed, 2001, 12(1), 89 - 105
Quantum mechanical quantitative structure activity relationships to avoid mutagenicity in dental monomers; Yourtee D et al.; The objective of this study was to identify through quantum mechanical quantitative structure activity relationships (Q-QSARs) chemical structures in dental monomers that influence their mutagenicity . AMPAC, a semiempirical computer program that provides quantum mechanical information for chemical structures, was applied to three series of reference chemicals: a set of methacrylates, a set of aromatic and a set of aliphatic epoxy compounds . QSAR models were developed using this chemical information together with mutagenicity data (Salmonella TA 100, Ames Test) . CODESSA, a QSAR program that calculates quantum chemical descriptors from information generated by AMPAC and statistically matches these descriptors with observed biological properties was used . QSARs were developed which had r2 values exceeding 0.90 for each study series . These QSARs were used to accurately predict the mutagenicity of BISGMA . a monomer commonly used in dentistry, and two epoxy monomers with developing use in dentistry, GY-281 and UVR-6105 . The Q-QSAR quantum mechanical descriptors correctly predicted the level of mutagenicity for all three compounds . The descriptors in the correlation equation pointed to components of structure that may contribute to mutagenesis . The QSARs also provided 'dose windows' for testing mutagenicity, circumventing the need for extensive dose exploration in the laboratory . The Q-QSAR method promises an approach for biomaterials scientists to predict and avoid mutagenicity from the chemicals used in new biomaterial designs.

An Esp Pediatr, 2001 May, 54(5), 510 - 2
{Reactive arthritis shortly after Streptococcus b-hemolyticus type A and Salmonella type B infection}; Gomez Carrasco J et al.; We report the case of a girl aged 2 years and 8 months with monoarticular arthritis of the knee . Onset and outcome were slow . The child had suffered uncomplicated pharyngitis and a diarrheal process 1 and 2 weeks respectively prior to developing the disease . Additional data suggested the presence of reactive arthritis after Streptococcus infection . Salmonella was also detected in the feces . Unlike rheumatic fever, post-streptococcus reactive arthritis does not follow Jones' criteria and the clinical course is slow . Because gastrointestinal infection with both Streptococcus and Salmonella occurred simultaneously, the interaction between both agents, each of which alone can cause reactive arthritis, might have produced a synergic action in our patient.

South Med J, 2001 Apr, 94(4), 435 - 7
Soft tissue and cartilage infection by Salmonella oranienburg in a healthy girl; Porcalla AR et al.; Focal extraintestinal infections from nontyphoid salmonellae have increased in incidence during the past decade . Typically, they are manifested as either osteomyelitis or meningitis as a complication of either bacteremia or enteric fever . Isolated salmonellal soft tissue infections, however, are rare and occur mostly in adults with chronic underlying conditions such as human immunodeficiency virus (HIV) infection, diabetes mellitus, and cell-mediated immunity defects . We report a case of an otherwise healthy adolescent who was exposed to a guinea pig with a skin mass . She subsequently had an isolated soft tissue infection with cartilaginous involvement of the anterior chest wall due to Salmonella enterica serogroup C1 (bioserotype oranienburg).

South Med J, 2001 Apr, 94(4), 427 - 8
Endocarditis due to Salmonella; Flannery MT et al.; We present a case of endocarditis caused by Salmonella in a patient with newly diagnosed diabetes and preexisting rheumatic heart disease . Despite sterilization of the blood with a fluoroquinolone and a third-generation cephalosporin, the patient required surgical intervention.

Avian Dis, 2001 Jan-Mar, 45(1), 195 - 200
Comparison of Salmonella isolation rates in different types of egg-layer hen houses in Chiba, Japan; Matsumoto A et al.; This study investigated the differences in Salmonella isolation rates in environmental samples taken from several types of hen houses in Chiba, Japan . In addition, for the detailed epidemiologic survey, environmental samples, hens, and rodents were collected from Salmonella-contaminated windowless houses on three farms . As a result, Salmonella was isolated from four (80%) of five farms with windowless hen houses; Salmonella enteritidis was isolated from a single windowless house . In contrast, only one serotype of Salmonella was isolated from 1 (6.7%) of 15 farms with open hen houses . In the S . enteritidis-contaminated windowless hen house, the isolation rates of S . enteritidis as compared with the other serotypes were 90.9% of environments, 94.1% of hens, and 86.4% of roof rats (Rattus rattus) that resided in the environments . In reference to the phage type (PT) of these isolates, PT1 was detected in environments and roof rats, and PT9 was detected in both these samples and in hens . Thus, the Salmonella isolation rate in hen houses seems to be associated with whether the premises are windowless or open . Moreover, roof rats appear to be the most important vectors in the spread of S . enteritidis in the windowless hen house because the S . enteritidis PTs coincide with each other.

EMBO J, 2001 May 1, 20(9), 2131 - 9
Cooperation between actin-binding proteins of invasive Salmonella: SipA potentiates SipC nucleation and bundling of actin; McGhie EJ et al.; Pathogen-induced remodelling of the host cell actin cytoskeleton drives internalization of invasive Salmonella by non-phagocytic intestinal epithelial cells . Two Salmonella actin-binding proteins are involved in internalization: SipC is essential for the process, while SipA enhances its efficiency . Using purified SipC and SipA proteins in in vitro assays of actin dynamics and F-actin bundling, we demonstrate that SipA stimulates substantially SipC-mediated nucleation of actin polymerization . SipA additionally enhances SipC-mediated F-actin bundling, and SipC-SipA collaboration generates stable networks of F-actin bundles . The data show that bacterial SipC and SipA cooperate to direct efficient modulation of actin dynamics, independently of host cell proteins . The ability of SipA to enhance SipC-induced reorganization of the actin cytoskeleton in vivo was confirmed using semi-permeabilized cultured mammalian cells.

Environ Sci Technol, 2001 Apr 15, 35(8), 1630 - 6
Evaluation of methods for predicting the toxicity of polycyclic aromatic hydrocarbon mixtures; Reeves WR et al.; Risk assessments of polycyclic aromatic hydrocarbon mixtures are hindered by a lack of reliable information on the potency of both mixtures and their individual components . This paper examines methods for approximating the toxicity of polycyclic aromatic hydrocarbon (PAH) mixtures . PAHs were isolated from a coal tar and then separated by ring number using HPLC . Five fractions (A-E) were generated, each possessing a unique composition and expected potency . The toxicity of each fraction was measured in the Salmonella/mutagenicity assay and the Chick Embryo Screening Test (CHEST) . Their abilities to induce ethoxyresorufin-O-deethylase and to inhibit gap junction intercellular communication in rat liver Clone 9 cells were also measured . In the Salmonella/mutagenicity assay, fractions were predicted to have potencies in the order C > D > E > B > A . Toxic equivalency factors (TEFs) for fractions A-E were in the order E > or = D > C > B > A . TEF values were 20,652, 20,929, 441, 306, and 74.1 micrograms of BaP equiv/g, respectively . A lack of agreement between assay-predicted potencies and chemical analysis-predicted potencies was observed with other assays and other methods of calculation . The results demonstrate the limitations of using a single method to predict the toxicity of a complex PAH mixture.

J Mol Biol, 2001 Apr 27, 308(2), 221 - 9
Flagellin polymerisation control by a cytosolic export chaperone; Auvray F et al.; Assembly of the long helical filament of the bacterial flagellum requires polymerisation of ca 20,000 flagellin (FliC) monomeric subunits into the growing structure extending from the cell surface . Here, we show that export of Salmonella flagellin is facilitated specifically by a cytosolic protein, FliS, and that FliS binds to the FliC C-terminal helical domain, which contributes to stabilisation of flagellin subunit interactions during polymerisation . Stable complexes of FliS with flagellin were assembled efficiently in vitro, apparently by FliS homodimers binding to FliC monomers . The data suggest that FliS acts as a substrate-specific chaperone, preventing premature interaction of newly synthesised flagellin subunits in the cytosol . Compatible with this view, FliS was able to prevent in vitro polymerisation of FliC into filaments .

J Clin Microbiol, 2001 May, 39(5), 1871 - 6
Detection of salmonellae in chicken feces by a combination of tetrathionate broth enrichment, capillary PCR, and capillary gel electrophoresis; Carli KT et al.; This report describes a rapid detection procedure for salmonellae from chicken feces by the combination of tetrathionate primary enrichment (preenrichment {PE})-bacterial lysis-capillary PCR and capillary gel electrophoresis . Pure Salmonella enterica serovar Enteritidis 64K was reisolated and detected by capillary PCR after buffered peptone water and nutrient broth, tetrathionate broth base Hajna (TTBH), and tetrathionate broth (TTB) preenrichments . When the same culture was mixed with intestinal homogenate, bacteriological reisolation and capillary PCR detection was achieved only by TTBH and TTB preenrichments . Capillary gel electrophoresis revealed that a Salmonella genus-specific 281-bp PCR product was detected when Salmonella strains but not non-Salmonella strains were tested . The detection limit of capillary PCR with whole-cell DNA extracted from pure Salmonella enterica serovars Enteritidis 64K, Typhimurium LT2-CIP60-62, and Gallinarum 64K was 3, 3, and 9 CFU ml(-1), respectively . The detection limit of capillary PCR from whole-cell DNA extracted from intestinal homogenate artificially contaminated with the same three strains was 3, 3, and 7 CFU ml(-1), respectively . We compared the results of the capillary PCR and bacteriological examination from the natural samples . Thirty-five of 53 naturally contaminated samples produced a specific PCR product . In 9 of the 35 PCR-positive samples, Salmonella could not be detected bacteriologically either by PE or a primary and delayed secondary enrichment (DSE) combination . In the 18 PCR-negative samples, 4 samples were found to harbor Salmonella by both PE and DSE and 14 samples were positive after DSE . Fifty-three additional intestinal homogenate samples, which were negative by their PE and DSE in bacteriological examination, were found to be also negative by their PCRs . The total time required to detect Salmonella with the capillary PCR method we used was approximately 20 h . If samples are from clinically diseased birds, the total time for PCR and detection is reduced to 2 h since the 18-h PE is not required . These results indicate that TTB enrichment, bacterial lysis, and genus-specific capillary PCR combined with capillary gel electrophoresis constitute a sensitive and selective procedure which has the potential to rapidly identify Salmonella-infected flocks.

J Bacteriol, 2001 May, 183(10), 3089 - 97
Aspartic peptide hydrolases in Salmonella enterica serovar typhimurium; Larsen RA et al.; Two well-characterized enzymes in Salmonella enterica serovar Typhimurium and Escherichia coli are able to hydrolyze N-terminal aspartyl (Asp) dipeptides: peptidase B, a broad-specificity aminopeptidase, and peptidase E, an Asp-specific dipeptidase . A serovar Typhimurium strain lacking both of these enzymes, however, can still utilize most N-terminal Asp dipeptides as sources of amino acids, and extracts of such a strain contain additional enzymatic activities able to hydrolyze Asp dipeptides . Here we report two such activities from extracts of pepB pepE mutant strains of serovar Typhimurium identified by their ability to hydrolyze Asp-Leu . Although each of these activities hydrolyzes Asp-Leu at a measurable rate, the preferred substrates for both are N-terminal isoAsp peptides . One of the activities is a previously characterized isoAsp dipeptidase from E . coli, the product of the iadA gene . The other is the product of the serovar Typhimurium homolog of E . coli ybiK, a gene of previously unknown function . This gene product is a member of the N-terminal nucleophile structural family of amidohydrolases . Like most other members of this family, the mature enzyme is generated from a precursor protein by proteolytic cleavage and the active enzyme is a heterotetramer . Based on its ability to hydrolyze an N-terminal isoAsp tripeptide as well as isoAsp dipeptides, the enzyme appears to be an isoAsp aminopeptidase, and we propose that the gene encoding it be designated iaaA (isoAsp aminopeptidase) . A strain lacking both IadA and IaaA in addition to peptidase B and peptidase E has been constructed . This strain utilizes Asp-Leu as a leucine source, and extracts of this strain contain at least one additional, as-yet-uncharacterized, peptidase able to cleave Asp dipeptides.

J AOAC Int, 2001 Mar-Apr, 84(2), 416 - 29
TECRA Unique test for rapid detection of Salmonella in food: collaborative study; Hughes D et al.; The TECRA Unique Salmonella test uses the principle of immunoenrichment to allow rapid detection of Salmonellae in food . A collaborative study was conducted to compare the TECRA Salmonella Unique test with the reference culture method given in the U.S . Food and Drug Administration's Bacteriological Analytical Manual . Three food types (milk powder, pepper, and soy flour) were analyzed in Australia and 2 food types (milk chocolate and dried egg) were analyzed in the United States . Forty-one collaborators participated in the study . For each of the 5 foods at each of the 3 levels, a comparison showed no significant differences (p > or = 0.05) in the proportion of positive test samples for Unique and that for the reference method using the Chi-square test for independence with continuity correction.

Int J Food Microbiol, 2001 Apr 11, 65(1-2), 55 - 62
PulseNet standardized protocol for subtyping Listeria monocytogenes by macrorestriction and pulsed-field gel electrophoresis; Graves LM et al.; PulseNet is a national network of pubic health and food regulatory laboratories established in the US to detect clusters of foodborne disease and respond quickly to foodborne outbreak investigations . PulseNet laboratories currently subtype Escherichia coli O157:H7, non-typhoidal Salmonella, and Shigella isolates by a highly standardized 1-day pulsed-field gel electrophoresis (PFGE), and exchange normalized DNA "fingerprint" patterns via the Internet . We describe a standardized molecular subtyping protocol for subtyping Listeria monocytogenes that was recently added to PulseNet . The subtyping can be completed within 30 h from the time a pure culture of the bacteria is obtained.

N Engl J Med, 2001 Apr 26, 344(17), 1263 - 9
The efficacy of a Salmonella typhi Vi conjugate vaccine in two-to-five-year-old children; Lin FY et al.; BACKGROUND: Typhoid fever is common in developing countries . The licensed typhoid vaccines confer only about 70 percent immunity, do not protect young children, and are not used for routine vaccination . A newly devised conjugate of the capsular polysaccharide of Salmonella typhi, Vi, bound to nontoxic recombinant Pseudomonas aeruginosa exotoxin A (rEPA), has enhanced immunogenicity in adults and in children 5 to 14 years old and has elicited a booster response in children 2 to 4 years old . METHODS: In a double-blind, randomized trial, we evaluated the safety, immunogenicity, and efficacy of the Vi-rEPA vaccine in children two to five years old in 16 communes in Dong Thap Province, Vietnam . Each of the 11,091 children received two injections six weeks apart of either Vi-rEPA or a saline placebo . Cases of typhoid, diagnosed by the isolation of S . typhi from blood cultures after 3 or more days of fever (a temperature of 37.5 degrees C or higher), were identified by active surveillance over a period of 27 months . We estimated efficacy by comparing the attack rate of typhoid in the vaccine group with that in the placebo group . RESULTS: S . typhi was isolated from 4 of the 5525 children who were fully vaccinated with Vi-rEPA and from 47 of the 5566 children who received both injections of placebo (efficacy, 91.5 percent; 95 percent confidence interval, 77.1 to 96.6; P<0.001) . Among the 771 children who received only one injection, there was 1 case of typhoid in the vaccine group and 8 cases in the placebo group . Cases were distributed evenly among all age groups and throughout the study period . No serious adverse reactions were observed . In all 36 children studied four weeks after the second injection of the vaccine, levels of serum IgG Vi antibodies had increased by a factor of 10 or more . CONCLUSIONS: The Vi-rEPA conjugate typhoid vaccine is safe and immunogenic and has more than 90 percent efficacy in children two to five years old . The antibody responses and the efficacy suggest that this vaccine should be at least as protective in persons who are more than five years old.

Proc Natl Acad Sci U S A, 2001 May 8, 98(10), 5850 - 5 Epub 2001 Apr 24.
Host microarray analysis reveals a role for the Salmonella response regulator phoP in human macrophage cell death; Detweiler CS et al.; Bacterial pathogens manipulate host cells to promote pathogen survival and dissemination . We used a 22,571 human cDNA microarray to identify host pathways that are affected by the Salmonella enterica subspecies typhimurium phoP gene, a transcription factor required for virulence, by comparing the expression profiles of human monocytic tissue culture cells infected with either the wild-type bacteria or a phoPTn10 mutant strain . Both wild-type and phoPTn10 bacteria induced a common set of genes, many of which are proinflammatory . Differentially expressed genes included those that affect host cell death, suggesting that the phoP regulatory system controls bacterial genes that alter macrophage survival . Subsequent experiments showed that the phoPTn10 mutant strain is defective for killing both cultured and primary human macrophages but is able to replicate intracellularly . These experiments indicate that phoP plays a role in Salmonella-induced human macrophage cell death.

Mutagenesis, 2001 May, 16(3), 183 - 7
Micronucleus induction and chromosomal aberration of 1- and 3-nitroazabenzo{a}pyrene and their N-oxides; Sera N et al.; Nitro-azabenzo{a}pyrenes, 1- or 3-nitro-azabenzo{a}pyrene and their N-oxides are nitrated derivatives of azabenzo{a} pyrene (ABP) containing nitrogen in the 6-position of benzo{a}pyrene (B{a}P) . The nitro-ABP-N-oxides (ABPOs) were formed by reaction of ABP with excess HNO(3) . These derivatives were noteworthy as potent mutagens for Salmonella strains, and were present in fine particles of diesel particulates . In this study, micronucleus induction in mice and chromosomal aberrations due to means of Chinese hamster lung fibroblast (CHL) cells were investigated to determine genotoxicity in order to define the relationship with the mutagenic potency of these derivatives . The induction of micronucleus polychromatic erythrocytes (MNPCEs) was dependent on the dose response of 10-40 mg for 3-N-6-ABP, and of 10-40 mg for 1-N-6-ABP, and in addition, 1- and 3-N-6-ABPOs markedly induced MNPCEs in a dose range of 10-400 mg and from 1 to 80 mg, respectively, when the compound was intraperitoneally administrated in two mice at each dose . The results show that of the four compounds, 3-N-6-ABPO demonstrated a marked increase in MNPCES: On the other hand, chromosomal aberrations of the four compounds were investigated by the duplicate tests using CHLS: The results after a 48 h treatment induced aberrations of the chromatid type, chromatid breaks and exchanges for 1- and 3-N-6-ABP, and mainly chromatid exchanges for 1- and 3-N-6-ABPO . The frequency of chromosomal aberrations associated with nitro substitution on the ABPO structure . Chromosomal aberrations of nitro derivatives of ABPO substituted at the 3-position on the structure were more potent than those at the 1-postion . N-oxide derivatives have been found to be reduced to anion radicals much more easily than azaB{a}P and its nitro derivatives . This suggests that the electrochemical reduction of the chemicals plays an important role in the metabolic activation of nitrated B{a}P derivatives.

Microbiology, 2001 May, 147(Pt 5), 1087 - 94
Endotoxic properties of lipid A from Comamonas testosteroni; Tanamoto K et al.; The lipid A from Comamonas testosteroni has been isolated and its complete chemical structure determined {Iida, T., Haishima, Y., Tanaka, A., Nishijima, K., Saito, S . & Tanamoto, K . (1996) . Eur J Biochem 237, 468-475} . In this work, the relationship between its chemical structure and biological activity was studied . The lipid A was highly homogeneous chemically and was characterized by the relatively short chain length (C(10)) of the 3-hydroxy fatty acid components directly bound to the glucosamine disaccharide backbone by either amide or ester linkages . The lipid A exhibited endotoxic activity in all of the assay systems tested (mitogenicity in mouse spleen cells; induction of tumour necrosis factor alpha release from both mouse peritoneal macrophages and mouse macrophage-like cell line J774-1, as well as from the human monocytic cell line THP-1; induction of nitric oxide release from J774-1 cells; Limulus gelation activity and lethal toxicity in galactosamine-sensitized mice) to the same extent as did 'Salmonella minnesota' lipid A or Escherichia coli LPS used as controls . The strong endotoxic activity of the C . testosteroni lipid A indicates that the composition of 3-hydroxydecanoic acid is not responsible for the low endotoxicity of the lipid A observed in members of the genus Rhodopseudomonas, as has previously been suggested . Furthermore, both the lack of a second acylation of the 3-hydroxy fatty acid attached at the 3' position, and the substitution of the hydroxyl group of the 3-hydroxy fatty acid attached at position 2, do not affect the manifestation of endotoxic activity or species specificity.

Biochemistry, 2001 May 1, 40(17), 5144 - 50
Enthalpic barriers to the hydrophobic binding of oligosaccharides to phage P22 tailspike protein; Baxa U et al.; The structural thermodynamics of the recognition of complex carbohydrates by proteins are not well understood . The recognition of O-antigen polysaccharide by phage P22 tailspike protein is a highly suitable model for advancing knowledge in this field . The binding to octa- and dodecasaccharides derived from Salmonella enteritidis O-antigen was studied by isothermal titration calorimetry and stopped-flow spectrofluorimetry . At room temperature, the binding reaction is enthalpically driven with an unfavorable change in entropy . A large change of -1.8 +/- 0.2 kJ mol(-1) K(-1) in heat capacity suggests that the hydrophobic effect and water reorganization contribute substantially to complex formation . As expected from the large heat-capacity change, we found enthalpy-entropy compensation . The calorimetrically measured binding enthalpies were identical within error to van't Hoff enthalpies determined from fluorescence titrations . Binding kinetics were determined at temperatures ranging from 10 to 30 degrees C . The second-order association rate constant varied from 1 x 10(5) M(-1) s(-1) for dodecasaccharide at 10 degrees C to 7 x 10(5) M(-1) s(-1) for octasaccharide at 30 degrees C . The first-order dissociation rate constants ranged from 0.2 to 3.8 s(-1) . The Arrhenius activation energies were close to 50 and 100 kJ mol(-1) for the association and dissociation reactions, respectively, indicating mainly enthalpic barriers . Despite the fact that this system is quite complex due to the flexibility of the saccharide, both the thermodynamic and kinetic data are compatible with a simple one-step binding model.

J Biol Chem, 2001 Jun 29, 276(26), 23607 - 15 Epub 2001 Apr 20.
SopE acts as an Rab5-specific nucleotide exchange factor and recruits non-prenylated Rab5 on Salmonella-containing phagosomes to promote fusion with early endosomes; Mukherjee K et al.; Rab-GTPase regulates the fusion between two specific vesicles . It is well documented that, for their biological function, Rab proteins need to be prenylated for attachment to the vesicle membrane . In contrast, we showed in the present investigation that SopE, a type III secretory protein of Salmonella, translocates onto Salmonella-containing phagosomes (LSP) and mediates the recruitment of non-prenylated Rab5 (Rab5:DeltaC4) on LSP in GTP form . Simultaneously, SopE present in infected cell cytosol acts as an Rab5-specific exchange factor and converts the inactive Rab-GDP to the GTP form . The non-prenylated Rab5 subsequently promoted efficient fusion of LSP with early endosomes . This is the first demonstration that a prenylation-deficient Rab protein retains biological activity and can promote vesicle fusion, if it is recruited on the membrane by some other method.

Asian Pac J Allergy Immunol, 2000 Dec, 18(4), 209 - 14
Nitric oxide production by murine spleen cells stimulated with Porphyromonas gingivalis-derived lipopolysaccharide; Sosroseno W; The aim of the present study was to determine whether Porphyromonas gingivalis-lipopolysaccharide (Pg-LPS) may stimulate nitric oxide (NO) production by murine spleen cells . Spleen cells derived from Balb/c mice were cultured in the presence of Pg-LPS or LPS from Salmonella Typhosa . The cell were also cultured in the presence of Pg-LPS with or without L-arginine, L-arginine plus NG-monomethyl-L-arginine (NMMA), or IFN-gamma . Furthermore, the plastic non-adherent spleen cells were stimulated with Pg-LPS and L-arginine . The results showed that Pg-LPS failed to stimulate splenic NO production by themselves . Exogenous L-arginine or IFN-gamma up-regulated the NO production of Pg-LPS-stimulated spleen cells, but the stimulatory effects of L-arginine were completely blocked by NMMA . It was also demonstrated that in the presence of Pg-LPS and L-arginine, splenic macrophages were the cellular source of NO . These results suggest, therefore, that P . gingivalis-LPS may induce murine splenic macrophages to produce NO in a L-arginine and an IFN-gamma-dependent mechanism.

Arthritis Rheum, 2001 Apr, 44(4), 931 - 9
Expression of host defense scavenger receptors in spondylarthropathy; Seta N et al.; OBJECTIVE: Reactive arthritis (ReA) is postulated to be caused by a defective host defense against gram-negative bacteria . HLA-B27 could play a role in this process, but does not account for the many HLA-B27 negative patients . The objective of this study was to test the expression of 3 macrophage scavenger receptors (SRs) that are responsible for innate immunity against gram-negative bacteria: SR class A type I (SR-AI), SR-AII, and the macrophage receptor with collagenous structure (MARCO) . We postulate that defects in such receptors might also contribute to the host risk factors that increase the predisposition to ReA and perhaps other subtypes of spondylarthropathy (SpA) . METHODS: Peripheral blood, synovial fluid, and synovial tissue samples were obtained from patients with recent Salmonella infection, ReA, other SpA, and rheumatoid arthritis (RA) . The expression of SRs receptors was assessed by semiquantitative reverse transcriptase-polymerase chain reaction . RESULTS: Evaluation of the peripheral blood mononuclear cells (PBMC) from 4 patients who were recently infected with Salmonella, showed that PBMC from 2 patients who developed ReA expressed positive levels of MARCO, while PBMC from 2 patients who recovered from infection without sequelae did not . The synovial fluid mononuclear cells (SFMC) from some ReA patients expressed MARCO, but the levels were only moderate . The level of MARCO in the SFMC from the SpA patient group was low . In marked contrast, MARCO expression was high in almost all samples of RA SFMC . These findings also extended to synovial tissues . CONCLUSION: Expression of the host defense gene MARCO was susceptible to modulation, not only during infections, but also in the inflammatory arthritis conditions RA and SpA . MARCO is a variable to be considered as a candidate factor that might contribute to ReA.

Pediatr Surg Int, 2001 Mar, 17(2-3), 215 - 7
Cecal perforation presenting as abdominal-wall necrotizing fasciitis; Sy ED et al.; The preoperative diagnosis of a cecal perforation associated with Salmonella infection as a cause of abdominal-wall necrotizing fasciitis (AWNF) is clinically difficult . Computed tomography of the abdomen is helpful, and can detect the combined presence of a pneumoscrotum and pneumoperitoneum . Its presence indicates a patent processus vaginalis, which acts as the primary route for the spread of the intra-abdominal infectious process into the abdominal wall . An exploratory laparotomy should be done to confirm the presence of intra-abdominal pathology in order to avoid delayed treatment.

Blood, 2001 May 1, 97(9), 2688 - 94
Missense mutation of the interleukin-12 receptor beta1 chain-encoding gene is associated with impaired immunity against Mycobacterium avium complex infection; Sakai T et al.; Interleukin-12 (IL-12) plays an important role in the production of interferon gamma (IFN-gamma) and is essential for protection against intracellular pathogens such as Mycobacterium and Salmonella . A 31-year-old man had disseminated Mycobacterium avium complex (MAC) infection . The production of IFN-gamma by peripheral blood mononuclear cells stimulated with phytohemagglutinin (PHA-PBMCs) was found severely impaired (40.7 pg/mL compared with 833 +/- 289 pg/mL for the patient's and healthy subjects' (n = 3) PHA- PBMCs, respectively), and the patient's PHA-PBMCs completely lacked surface IL-12 receptor beta1 (IL-12Rbeta1) chain . The IL-12Rbeta1 gene transcript in his PHA-PBMCs had an R213W substitution in each allele . Family history showed that both parents were heterozygotes in the R213W substitution . Transfection of a human embryonal kidney cell line 293 (HEKC293) with wild-type IL-12Rbeta1wt gene led to cell surface IL-12Rbeta1 expression; however, no expression was seen in HEKC293 transfected with the mutated IL-12Rbeta1R213W gene . The IL-12Rbeta1 gene transcript, but no IL-12Rbeta1 protein, was detected in PHA-PBMCs and T cells, suggesting a post-translational event(s), most likely a shortened turnover of the protein . The R213W substitution was not detected in the cells of 32 healthy persons or of 25 patients with tuberculosis or MAC infection . Six amino acid substitutions (Q214R, M365T, G378R, H438Y, A525T, and G594E) were identified, but the incidences of such substitutions were not significantly different between the groups . The Q214R substitution is reportedly linked to IL-12Rbeta1 deficiency; however, the study showed that 19 and 10 of 57 Japanese and 6 and 4 of 33 healthy white persons were heterozygous and homozygous for Arg-214, respectively, suggesting that the Q214R substitution represents a polymorphism and is not related to IL-12Rbeta1 deficiency but that the R213W substitution is responsible for IL-12Rbeta1 deficiency.

Food Chem Toxicol, 2001 May, 39(5), 499 - 505
Effect of pyrolysis temperature on the mutagenicity of tobacco smoke condensate; White JL et al.; Tobacco smoke aerosols with fewer mutagens in the particulate fraction may present reduced risk to the smoker . The objective of this study was to test the hypothesis that the temperature at which tobacco is pyrolyzed or combusted can affect the mutagenicity of the particulate fraction of the smoke aerosol . Tobacco smoke aerosol was generated under precisely controlled temperature conditions from 250 to 550 degrees C by heating compressed tobacco tablets in air . The tobacco aerosols generated had a cigarette smoke-like appearance and aroma . The tobacco smoke aerosol was passed through a Cambridge filter pad to collect the particulate fraction, termed the smoke condensate . Although condensates of tobacco smoke and whole cigarette mainstream smoke share many of the same chemical components, there are physical and chemical differences between the two complex mixtures . The condensates from smoke aerosols prepared at different temperatures were assayed in the Ames Salmonella microsome test with metabolic activation by rat liver S9 using tester strains TA98 and TA100 . Tobacco smoke condensates were not detectably mutagenic in strain TA98 when the tobacco smoke aerosol was generated at temperatures below 400 degrees C . Above 400 degrees C, condensates were mutagenic in strain TA98 . Similarly, condensates prepared from tobacco smoke aerosols generated at temperatures below 475 degrees C were not detectably mutagenic in strain TA100 . In contrast, tobacco tablets heated to temperatures of 475 degrees C or greater generated smoke aerosol that was detectably mutagenic as measured in TA100 . Therefore, heating and pyrolyzing tobacco at temperatures below those found in tobacco burning cigarettes reduces the mutagenicity of the smoke condensate . Highly mutagenic heterocyclic amines derived from the pyrolysis of tobacco leaf protein may be important contributors to the high temperature production of tobacco smoke Ames Salmonella mutagens . The relevance of these findings regarding cancer risk in humans is difficult to assess because of the lack of a direct correlation between mutagenicity in the Ames Salmonella test and carcinogenicity.

Vaccine, 2001 Apr 30, 19(23-24), 3277 - 84
Vaccination with the glycoprotein D gene of pseudorabies virus delivered by nonpathogenic Escherichia coli elicits protective immune responses; Shiau AL et al.; Attenuated intracellular bacteria, such as Salmonella and Shigella, have been exploited to act as gene delivery vectors . In this study, we report that nonpathogenic, live Escherichia coli can be used for the delivery of DNA vaccines in vivo, leading to generation of immune responses against plasmid-encoded foreign antigens . The pseudorabies virus (PrV) DNA vaccine carrying the glycoprotein D (gD) gene delivered by E . coli was able to induce protective immune responses in mice against a lethal PrV challenge . Co-delivery of E . coli carrying plasmid DNA encoding prothymosin alpha enhanced cellular immune responses to the PrV DNA vaccine delivered by E . coli . Our results suggest that nonpathogenic E . coli may be used as a vector for DNA vaccines in veterinary uses.

Prev Vet Med, 2001 May 1, 49(3-4), 175 - 90
Estimation of animal-level prevalence from pooled samples in animal production; Evers EG et al.; Often, the prevalence of an infection in the animal-production sector is determined at the group level . The prevalence at animal level (p) gives more-precise information on the infection status of the sector . This paper shows that pooled-sample data together with mathematical models allow for estimation of p . For this, model assumptions have to be made on the variation of p between groups separated in space and/or time . Formulas were derived for four models that were based on different assumptions . Model 1 assumed that p has the same value for all groups . Models 2-4 assumed that some of the groups were not infected . In addition, model 2 assumed that p has the same value for all infected groups; model 3 assumed that for an infected group, p is equal to either p(1) or p(2); and model 4 assumed that p was Beta distributed among infected groups . The models were applied to data sets on Salmonella infection in broiler flocks, including serotype data dominated by S . Hadar and S . Paratyphi B, var . Java . Based on likelihood-ratio tests, models 3 and 4 consistently fitted significantly better to the data . The applicability of model 4 is numerically bounded, related to the shape of the Beta distribution of p . Model calculations show that flock-level prevalence of Salmonella is much higher after than before slaughter . This difference (which possibly is related to different types of samples) is much smaller at the animal level . An important result of the estimation of p is that it in turn allows for an estimation of the proportion of false-negative groups--which is important in estimating the effect of veterinary or public-health measures.

J Wildl Dis, 2001 Apr, 37(2), 229 - 38
Salmonelliasis in wildlife from Queensland; Thomas AD et al.; During a 20 yr period (1978 to 1998), 233 isolates of Salmonella spp . were cultured from 179 wildlife animals (representing 25 species), 32 crocodile (Crocodylus porosus) eggs and six crocodile nesting sites, and represented 59 different serotypes . Salmonella serotype Virchow, the major serotype infecting humans in north Queensland, (Australia) was common in macropodids, but was not found in reptiles and was isolated only once from cane toads (Bufo marinus) . Investigations of human cases of salmonellosis should include simultaneous studies on wild and domestic animals in contact with the case.

Microb Drug Resist, 2001 Spring, 7(1), 13 - 21
Variation in clonality and antibiotic-resistance genes among multiresistant Salmonella enterica serotype typhimurium phage-type U302 (MR U302) from humans, animals, and foods; Walker RA et al.; Since 1990 multiresistant (MR) Salmonella enterica serotype Typhimurium definitive phage-type (DT) 104 (MR DT104) and closely related phage types have emerged as a worldwide health problem in humans and food animals . In this study the presence of the blaCARB-2 (ampicillin), cmlA (chloramphenicol), aadA2 (streptomycin/spectinomycin), sul1 (sulphonamide), and tetG (tetracycline) resistance genes in isolates of one such phage type, U302, have been determined . In addition blaTEM primers have been used for the detection of TEM-type beta-lactamases . Isolates have also been characterized by plasmid profile and pulsed field gel electrophoresis (PFGE) . Thirty-three of 39 isolates were positive for blaCARB-2, cmlA, aadA2, sul1 and tetG, four for blaTEM, aadA2 and sul1, one for aadA2 and sul1, and one for blaTEM only . blaTEM-mediated ampicillin resistance was transferred to Escherichia coli K12 from three isolates along with other resistance markers, including resistance to chloramphenicol, streptomycin, spectinomycin, sulphonamides, and tetracyclines . Strains carried up to 6 plasmids and 34 plasmid profiles were identified . Although the majority of strains (33/39) produced a PFGE profile identical to that predominant in MR DT104, six different patterns were generated demonstrating the presence of various clones within MR U302 . The results show that the majority of the MR U302 strains studied possessed the same antibiotic resistance genes as MR DT104 . However, isolates with distinctive PFGE patterns can have different mechanisms of resistance to ampicillin, chloramphenicol, streptomycin, sulphonamides, and tetracyclines . Such resistance genes may be borne on transmissible plasmids.

Int J Med Microbiol, 2001 Mar, 290(8), 707 - 18
Virulence in the chick model and stress tolerance of Salmonella enterica serovar Orion var . 15+; La Ragione RM et al.; Three Salmonella enterica serovar Orion var . 15+ isolates of distinct provenance were tested for survival in various stress assays . All were less able to survive desiccation than a virulent S . Enteritidis strain, with levels of survival similar to a rpoS mutant of the S . Enteritidis strain, whereas one isolate (F3720) was significantly more acid tolerant . The S . Orion var . 15+ isolates were motile by flagellae and elaborated type-1 and curli-like fimbriae; surface organelles that are considered virulence determinants in Salmonella pathogenesis . Each adhered and invaded HEp-2 tissue culture cells with similar proficiency to the S . Enteritidis control but were significantly less virulent than S . Enteritidis in the one-day-old and seven-day-old chick model . Given an oral dose of 1 x 10(3) cfu to one-day-old chicken, S . Orion var . 15+ isolates colonised 25% of liver and spleens examined at 24 h whereas S . Enteritidis colonised 100% of organs by the same with the same dose . Given an oral dose of 1 x 10(7) cfu at seven-day old, S . Orion var . 15+ failed to colonise livers and spleens in any bird examined at 24 h whereas S . Enteritidis colonised 50% of organs by the same with the same dose . Based on the number of internal organs colonised, one of the three S . Orion var . 15+ isolates tested (strain F3720) was significantly more invasive than the other two (B1 and B7) . Also, strain F3720 was shed less than either B1 or B7 supporting the concept that there may be an inverse relationship between the ability to colonise deep tissues and to persist in the gut . These data are discussed in the light that S . Orion var . 15+ is associated with sporadic outbreaks of human infection rather than epidemics.

Scand J Immunol, 2001 May, 53(5), 437 - 42
Vaccination against Helicobacter pylori in non-human primate models and humans; Lee CK; Several vaccination studies have been performed in monkeys and humans testing the feasibility of prophylactic and therapeutic immunizations against Helicobacter pylori . The monkey studies showed that immune responses were induced by oral vaccination with the mucosal adjuvant LT (Escherichia coli heat-labile enterotoxin), parenteral administration with a cationic lipid adjuvant, and by mucosal priming followed by parenteral boosts . Both prophylactic and therapeutic activities were demonstrated in monkeys, providing a strong impetus for human vaccine trials . Preliminary studies in humans were undertaken in order to identify a tolerable dose of LT adjuvant or to test the effectiveness of mutant atoxic LT adjuvants . The results from these preliminary studies suggest that native LT causes diarrhoea at doses required for adjuvanticity while a mutant LT does not . In one study in which infected human subjects were vaccinated with orally administered urease antigen with native LT, there was a modest reduction in the level of H . pylori gastric colonization . A second clinical study employing H . pylori whole cell antigen and a mutant LT in infected subjects showed immune responses and although the subjects remained infected, the study was not designed to measure reduction in H . pylori colonization . Recombinant Salmonella expressing urease and other H . pylori antigens have been effective in mice (see accompanying Frontlines Topic Review by John O . Nedrud {1}), but monkey studies are not possible because of host range restriction . Human trials of parenteral immunization, mucosal immunization with mutant LT and live Salmonella vectors are needed to fully assess the ability of vaccines to prevent or treat H . pylori infections.

J Appl Microbiol, 2001 Apr, 90(4), 494 - 507
Antimicrobial properties of phenolic compounds from berries; Puupponen-Pimia R et al.; AIMS: To investigate the antimicrobial properties of phenolic compounds present in Finnish berries against probiotic bacteria and other intestinal bacteria, including pathogenic species . METHODS AND RESULTS: Antimicrobial activity of pure phenolic compounds representing flavonoids and phenolic acids, and eight extracts from common Finnish berries, was measured against selected Gram-positive and Gram-negative bacterial species, including probiotic bacteria and the intestinal pathogen Salmonella . Antimicrobial activity was screened by an agar diffusion method and bacterial growth was measured in liquid culture as a more accurate assay . Myricetin inhibited the growth of all lactic acid bacteria derived from the human gastrointestinal tract flora but it did not affect the Salmonella strain . In general, berry extracts inhibited the growth of Gram-negative but not Gram-positive bacteria . These variations may reflect differences in cell surface structures between Gram-negative and Gram-positive bacteria . Cloudberry, raspberry and strawberry extracts were strong inhibitors of Salmonella . Sea buckthorn berry and blackcurrant showed the least activity against Gram-negative bacteria . CONCLUSION: Different bacterial species exhibit different sensitivities towards phenolics . SIGNIFICANCE AND IMPACT OF THE STUDY: These properties can be utilized in functional food development and in food preservative purposes.

J Food Prot, 2001 Apr, 64(4), 542 - 5
Incidence of Salmonella in five Swedish slaughterhouses; Thorberg BM et al.; Five Swedish slaughterhouses where pig slaughter takes place were sampled and tested for Salmonella . Each slaughterhouse was visited six times, and sampling was done repeatedly at specific points in the slaughter line during the day . Both sampling of pork carcasses and the slaughterhouse environment was done . This study was part of a larger European project, entitled Salmonella in Pork (Salinpork), with the aim of identifying specific risk points or risk factors associated with Salmonella contamination that contribute to health hazards for humans . During the study, a total of 3,388 samples from the five slaughterhouses were collected and cultured for Salmonella . All of the samples were culture negative for Salmonella.

J Food Prot, 2001 Apr, 64(4), 442 - 50
Evaluation of volatile chemical treatments for lethality to Salmonella on alfalfa seeds and sprouts; Weissinger WR et al.; A study was done to evaluate natural volatile compounds for their ability to kill Salmonella on alfalfa seeds and sprouts . Acetic acid, allyl isothiocyanate (AIT), trans-anethole, carvacrol, cinnamic aldehyde, eugenol, linalool, methyl jasmonate, and thymol were examined for inhibitory and lethal activity against Salmonella by exposing inoculated alfalfa seeds to compounds (1,000 mg/liter of air) for 1, 3, and 7 h at 60 degrees C . Only acetic acid, cinnamic aldehyde, and thymol caused significant reductions in Salmonella populations (>3 log10 CFU/g) compared with the control (1.9 log10 CFU/g) after treatment for 7 h . Treatment of seeds at 50 degrees C for 12 h with acetic acid (100 and 300 mg/liter of air) and thymol or cinnamic aldehyde (600 mg/liter of air) significantly reduced Salmonella populations on seeds (>1.7 log10 CFU/g) without affecting germination percentage . Treatment of seeds at 50 degrees C with AIT (100 and 300 mg/liter of air) and cinnamic aldehyde or thymol (200 mg/liter of air) did not significantly reduce populations compared with the control . Seed germination percentage was largely unaffected by treatment with gaseous acetic acid, AIT, cinnamic aldehyde, or thymol for up to 12 h at 50 degrees C . The number of Salmonella on seeds treated at 70 degrees C for 80 min with acetic acid (100 and 300 mg/liter of air), AIT (100 mg/liter of air), and cinnamic aldehyde and thymol (600 mg/liter of air) at water activity (a(w)) 0.66 was not significantly different than the number inactivated on seeds at a(w) 0.49 . Acetic acid at 200 and 500 mg/liter of air reduced an initial population of 7.50 log10 CFU/g of alfalfa sprouts by 2.33 and 5.72 log10 CFU/g, respectively, within 4 days at 10 degrees C . whereas AIT at 200 and 500 mg/liter of air reduced populations to undetectable levels; however, both treatments caused deterioration in sensory quality . Treatment of sprouts with 1 or 2 mg of AIT per liter of air adversely affected sensory quality but did not reduce Salmonella populations after 11 days of exposure at 10 degrees C.

Apoptosis, 2000 Dec, 5(6), 509 - 14
Protection of apoptotic cell death by protein A; Ray PK et al.; The word "Apoptosis" or pragrammed cell death is described as the ultimate end of multiple cellular events converging from numerous initiating events to the ultimate death of a cell or organism . Several processes, such as initiation of death signals at the plasma membrane, expression of pro-apoptotic oncoproteins, activation of death proteases, endonucleases etc., that ultimately coalesce to a common irreversible execution phase, lead to cell demise . Counteracting the death signals are cell survival factors . A balance between the cell death and cell survival factors plays a major role in the decision making process as to whether a cell should die or must live . It is, therefore, hypothesized that if the balance can be shifted in favor of cell survival, one might be able to arrest the aging process, save the injured cells or else if the balance is shifted toward cell-kill it might help destroy tumors and other undesirable cells . Protein A (PA) of Staphylococcus aureus has been found to have multifarious biological response modifying properties . It has been shown to possess anti-tumor, antitoxic, anti-parasitic and antifungal activities . It also acts as a potent immunostimulator . PA can protect bone marrow progenitor cells from zidovudin(AZT)-induced apoptosis and can stimulate immunocyte proliferation, thereby helping to replenish/restore the depleted hematopoietic cell pool . Such ability to replenish hematopoietic cells is a common property of PA observed against a number of toxic drugs/chemicals, such as cyclophosphamide, benzene, aflatoxin, salmonella endotoxin, etc . Interestingly, it was further demonstrated in our laboratory that PA can selectively kill tumor cells without affecting normal cells of the host . A search for the mechanisms of PA action revealed that this bacterial protein could shift the balance between pro- and anti-apoptotic proteins in favor of survival in normal cells, but in favor of cell death in tumor cells at a particular dose level . This unique property of PA suggests that controlled use of such type of Biological Response Modifier might help in controlling both cell growth and death phenomena.

Trends Microbiol, 2001 Mar, 9(3), 137 - 44
Bacteriophage-bacteriophage interactions in the evolution of pathogenic bacteria; Boyd EF et al.; Many bacteriophages carry virulence genes encoding proteins that play a major role in bacterial pathogenesis . Recently, investigators have identified bacteriophage-bacteriophage interactions in the bacterial host cell that also contribute significantly to the virulence of bacterial pathogens . The relationships between the bacteriophages pertain to one bacteriophage providing a helper function for another, unrelated bacteriophage in the host cell . Accordingly, these interactions can involve the mobilization of bacteriophage DNA by another bacteriophage, for example in Escherichia coli, Vibrio coli and Staphylococcus aureus; the host receptor for one bacteriophage being encoded by another, as found in V . cholerae; and the presence of one bacteriophage potentiating the virulence properties of another bacteriophage, as found in V . cholerae and Salmonella enterica.

Antimicrob Agents Chemother, 2001 May, 45(5), 1337 - 42
Synergy of histone-derived peptides of coho salmon with lysozyme and flounder pleurocidin; Patrzykat A et al.; Recent research has identified endogenous cationic antimicrobial peptides as important factors in the innate immunity of many organisms, including fish . It is known that antimicrobial activity, as well as lysozyme activity, can be induced in coho salmon (Oncorhynchus kisutch) mucus after exposure of the fish to infectious agents . Since lysozyme alone does not have antimicrobial activity against Vibrio anguillarum and Aeromonas salmonicida, a four-step protein purification protocol was used to isolate and identify antibacterial fractions from bacterially challenged coho salmon mucus and blood . The purification consisted of extraction with hot acetic acid, extraction and concentration on a C(18) cartridge, gel filtration, and reverse-phase chromatography on a C(18) column . N-terminal amino acid sequence analyses revealed that both the blood and the mucus antimicrobial fractions demonstrated identity with the N terminus of trout H1 histone . Mass spectroscopic analysis indicated the presence of the entire histone, as well as fragments thereof, including a 26-amino-acid N-terminal segment . These fractions inhibited the growth of antibiotic-supersuscptible Salmonella enterica serovar Typhimurium, as well as A . salmonicida and V . anguillarum . Synthetic peptides identical to the N-terminally acetylated or C-terminally amidated 26-amino-acid fragment were inactive in antimicrobial assays, but they potentiated the antimicrobial activities of the flounder peptide pleurocidin, lysozyme, and crude lysozyme-containing extracts from coho salmon . The peptides bound specifically to anionic lipid monolayers . However, synergy with pleurocidin did not appear to occur at the cell membrane level . The synergistic activities of inducible histone peptides indicate that they play an important role in the first line of salmon defenses against infectious pathogens and that while some histone fragments may have direct antimicrobial effects, others improve existing defenses.

Saudi Med J, 2001 Feb, 22(2), 129 - 32
Serogroups and antimicrobial susceptibility of non-typhoidal salmonellas in children; Al-Zamil FA et al.; OBJECTIVE: To update knowledge regarding the pattern of Serogroups and antimicrobial susceptibility of Salmonellas causing gastroenteritis in children at the King Khalid University Hospital in Riyadh, Saudi Arabia during the period of 1st April 1996 to 30th September 1999 . METHODS: The case records of 416 children, from whom Salmonella species were isolated from stool cultures between April 1996 and September 1999 were reviewed . The isolates and susceptibility of these Salmonella were carried out accordingly to standard microbiological methods . RESULTS: During a period of 3 and 1/2 years a total of 412 non-typhoidal Salmonellas were isolated from stool cultures of 416 children who presented to King Khalid University Hospital complaining of gastroenteritis . The majority of these children (70%) belonged to the age group 0-4 years . Eighty seven percent of the Salmonella isolates were Serogroup D1, B and C1 . The Serogroups and antimicrobial susceptibility of these Salmonellas differed from those previously reported from this country and other parts of the world . CONCLUSION: Salmonella gastroenteritis is an important clinical condition in infants and children in the Kingdom of Saudi Arabia . Salmonella Serogroups D1, B and C predominate as causative agents of this condition . Most of the salmonella serogroups isolated in this study were highly susceptible to commonly used antimicrobial agents but ampicillin showed a rising resistance pattern . This may make it unsuitable therapy for Salmonella gastroenteritis.

Biochemistry, 2001 Mar 27, 40(12), 3700 - 9
Kinetic and mutagenic characterization of the chromosomally encoded Salmonella enterica AAC(6')-Iy aminoglycoside N-acetyltransferase; Magnet S et al.; The chromosomally encoded aminoglycoside N-acetyltransferase, AAC(6')-Iy, from Salmonella enterica confers resistance toward a number of aminoglycoside antibiotics . The structural gene was cloned and expressed and the purified enzyme existed in solution as a dimer of ca . 17 000 Da monomers . Acetyl-CoA was the preferred acyl donor, and most therapeutically important aminoglycosides were substrates for acetylation . Exceptions are those aminoglycosides that possess a 6'-hydroxyl substituent (e.g., lividomycin) . Thus, the enzyme exhibited regioselective and exclusive acetyltransferase activity to 6'-amine-containing aminoglycosides . The enzyme exhibited Michaelis-Menten kinetics for some aminoglycoside substrates but "substrate activation" with others . Kinetic studies supported a random kinetic mechanism for the enzyme . The enzyme was inactivated by iodoacetamide in a biphasic manner, with half of the activity being lost rapidly and the other half more slowly . Tobramycin, but not acetyl-CoA, protected against inactivation . Each of the three cysteine residues (C70, C109, C145) in the wild-type enzyme were carboxamidomethylated by iodoacetamide . Cysteine 109 in AAC(6')-Iy is conserved in 12 AAC(6') enzyme sequences of the major class I subfamily . Surprisingly, mutation of this residue to alanine neither abolished activity nor altered the biphasic inactivation by iodoacetamide . The maximum velocity and V/K values for a number of aminoglycosides were elevated in this single mutant, and the kinetic behavior of substrates exhibiting linear vs nonlinear kinetics was reversed . Cysteine 70 in AAC(6')-Iy is either a cysteine or a threonine residue in all 12 AAC(6') enzymes of the major class I subfamily . The double mutant, C109A/C70A, was not inactivated by iodoacetamide . The double mutant exhibited large increases in the K(m) values for both acetyl-CoA and aminoglycoside substrates, and all aminoglycoside substrates exhibited Michaelis-Menten kinetics . Solvent kinetic isotope effects on V/K were normal for the WT enzyme and inverse for the double mutant . We discuss a chemical mechanism and the likely rate-limiting steps for both the wild-type and mutant forms of the enzyme.

Poult Sci, 2001 Apr, 80(4), 515 - 21
Thermal inactivation of Salmonella senftenberg and Listeria innocua in ground chicken breast patties processed in an air convection oven; Murphy RY et al.; Ground chicken breast patties were thermally processed in a lab-scale air convection oven at air temperatures of 163, 177, 190, 204, or 218 C to final patty center temperatures of 50, 55, 60, 65, 70, 75, or 80 C . The cooking time increased with increasing product temperature and decreased with increasing oven air temperature . Prior to thermal processing, approximately 7 log10(cfu/g) of Salmonella senftenberg and Listeria innocua were inoculated into the chicken patties . Survival of S . senftenberg and L . innocua decreased with increasing patty temperature . After the patties were processed to a final center temperature of 70 to 80 C, 1 to 4 log10 (cfu/g) of S . senftenberg and 3 to 5 log10(cfu/g) of L . innocua were detected in the cooked patties . A significant difference in the thermal inactivation of S . senftenberg and L . innocua was obtained between the chicken patties cooked in an air convection oven and the patties cooked in a water bath . More surviving S . senftenberg and L . innocua were found in the patties cooked in an air convection oven than in the patties cooked in a water bath.

Eur J Epidemiol, 2000, 16(9), 861 - 8
A review of the Salmonellosis surveillance systems in Italy: evolution during the course of time within the international framework; Scuderi G; This paper focuses on the history of the two systems that have been adopted in Italy for the surveillance of Salmonellosis and describes their respective characteristics . Both systems have been subsequently modified: (1) The National Laboratory-based Surveillance System (NLSS) which was created in 1967 for Enteropathogenic Bacteria and subsequently, in 1992, became part of the European computerised Laboratory-based Surveillance System of Salmonellae isolates, the SALM-NET (Salmonella network); (2) The National Infectious Disease Reporting System (NIDRS) which was set up in the 1930s, revised in 1990 and has been used, since 1994, along with the Infectious Disease Informative System (IDIS) . The results obtained with the different surveillance systems are presented: (1) The number of isolates from the laboratory surveillance from 1973 to 1997 are described . Total Salmonellae isolates have a slope with an increasing trend from 4372 isolates in 1973 to 15,041 isolates in 1988 drastically dropping to 5479 isolates in 1990 and increasing again to 13,596 isolates in 1993 . Attention is given particularly to the epidemiology of S . enteritidis in Italy which increased progressively since 1982 (225 isolates) to 5435 isolates in 1994 . S . typhimurium showed a slightly increasing trend in the period 1973-1988 (from 1694 to 3383 isolates) then decreased for reaching again previous levels . S . typhi showed a marked reduction from 573 isolates in 1973 to 33 isolates in 1996 . On the contrary, other less frequent serotypes increased . (2) The number of cases of Salmonellosis reported during 1971-1997 are also presented . Other Infections by Salmonellae increased from 12,516 cases in 1976 (renamed Non Typhoidal Salmonellosis in 1990) to more than 20,000 cases in 1992 . The number of cases of Typhoid Fever and Infections by S . paratyphi are also described . Particular attention has to be paid to the parallel trends of Salmonellosis using both surveillance systems: number of isolates and number of cases, particularly comparing Other Infections by Salmonellae and total Salmonellae isolates: after the 1992-1993 peak, an initial decrease was observed.

Turk J Pediatr, 2001 Jan-Mar, 43(1), 85 - 7
Sepsis and multiple brain abscesses caused by Salmonella paratyphi B in an infant: successful treatment with sulbactam-ampicillin and surgical drainage; Yildiran A et al.; Abscess formation by Salmonella species is an uncommon but significant manifestation of salmonellosis, because this type of infection has high morbidity and mortality rates and is a potential nosocomial hazard . In infants, history of consumption of contaminated water should be especially quired . We report a case who had sepsis and multiple brain abscesses due to Salmonella paratyphi B and who responded to sulbactam-ampicillin (SAM) therapy . Sulbactam-ampicillin combination may be preferable due to its immunomodulator effect.

EMBO J, 2001 Apr 17, 20(8), 1840 - 9
Expression of microbial virulence proteins in Saccharomyces cerevisiae models mammalian infection; Lesser CF et al.; Bacterial virulence proteins that are translocated into eukaryotic cells were expressed in Saccharomyces cerevisiae to model human infection . The subcellular localization patterns of these proteins in yeast paralleled those previously observed during mammalian infection, including localization to the nucleus and plasma membrane . Localization of Salmonella SspA in yeast provided the first evidence that SspA interacts with actin in living cells . In many cases, expression of the bacterial virulence proteins conferred genetically exploitable growth phenotypes . In this way, Yersinia YopE toxicity was demonstrated to be linked to its Rho GTPase activating protein activity . YopE blocked polarization of the yeast cytoskeleton and cell cycle progression, while SspA altered polarity and inhibited depolymerization of the actin cytoskeleton . These activities are consistent with previously proposed or demonstrated effects on higher eukaryotes and provide new insights into the roles of these proteins in pathogenesis: SspA in directing formation of membrane ruffles and YopE in arresting cell division . Thus, study of bacterial virulence proteins in yeast is a powerful system to determine functions of these proteins, probe eukaryotic cellular processes and model mammalian infection.

Vet Microbiol, 2001 May 21, 80(2), 171 - 84
Salmonella seroprevalence at the population and herd level in pigs in The Netherlands; van der Wolf PJ et al.; The aim of this study was to provide baseline data on the population and herd Salmonella seroprevalence in sows and finishers . For the population estimates in 1996 and 1999 and the herd prevalences for sows and gilts, blood samples from swine vesicular disease (SVD) and pseudorabies monitoring programmes were used and tested in an indirect Salmonella enzyme-linked immunosorbent assay (ELISA) . The herd prevalence for finishers was determined using blood samples collected at two slaughterhouses.The population prevalence for finishers in 1996 and 1999 was 23.7 and 24.5%, respectively, and for sows 40.5 and 60.4%, respectively . The prevalence in free range (FR) finishers was significantly higher (44.6%) than in intensively housed finishers in 1999, identifying a hazard group for possible extra pork and pork product contamination . Of 406 finishing herds, 9% were completely seronegative for Salmonella (cut-off OD%>10) . Of these 406 finishing herds, 69.7% had Salmonella-status I (low prevalence), 21.7% status II (moderate prevalence) and 8.6% status III (high prevalence) (cut-off OD%>40) . In 46 multiplying sow herds, 20 breeding sow herds and 20 matching replacement gilt herds, the average herd prevalences were 54, 44.4 and 19.3%, respectively . Two gilt herds were completely seronegative . The prevalence in the gilt herds was never higher than in the matching breeding sow herds . Agreement on methodology and calibration of ELISA tests would make these results comparable between countries and is a prerequisite for a co-ordinated and integrated program to reduce Salmonella in pork in the European Union.

Vet Microbiol, 2001 May 21, 80(2), 139 - 48
Typing of Salmonella enterica subsp . enterica serovar Mbandaka isolates; Hoszowski A et al.; Recently, Salmonella enterica subsp . enterica serovar Mbandaka (S . Mbandaka) has gained some importance in the epidemiology of salmonellosis in Poland . Since biotyping, resistance typing, and plasmid profiling were insufficient for strain differentiation, genome macrorestriction by means of pulse-field gel electrophoresis (PFGE) was applied and proved to be the method of choice in S . Mbandaka epidemiological studies . XbaI and BcuI macrorestriction produced 15 and 14 pulse-field profiles (PFP), respectively, but in the case of each enzyme one profile was prevalent . When macrorestriction profiles were combined, a total 24 patterns were found . Based on the similarity of the profiles, four clonal lineages were identified . One clonal lineage contained the majority of poultry, feed and human isolates . Poultry was concluded to be an important source of S . Mbandaka for humans in Poland . Complementary use of various typing techniques improved efficacy of epidemiological studies giving possibility to subdivide S . Mbandaka into 35 types and the index of discrimination reached 0.947.

Biochemistry, 2001 Apr 17, 40(15), 4703 - 13
In vitro conversion of propionate to pyruvate by Salmonella enterica enzymes: 2-methylcitrate dehydratase (PrpD) and aconitase Enzymes catalyze the conversion of 2-methylcitrate to 2-methylisocitrate; Horswill AR et al.; Salmonella enterica serovar Typhimurium LT2 catabolizes propionate through the 2-methylcitric acid cycle, but the identity of the enzymes catalyzing the conversion of 2-methylcitrate into 2-methylisocitrate is unclear . This work shows that the prpD gene of the prpBCDE operon of this bacterium encodes a protein with 2-methylcitrate dehydratase enzyme activity . Homogeneous PrpD enzyme did not contain an iron-sulfur center, displayed no requirements for metal cations or reducing agents for activity, and did not catalyze the hydration of 2-methyl-cis-aconitate to 2-methylisocitrate . It was concluded that the gene encoding the 2-methyl-cis-aconitate hydratase enzyme is encoded outside the prpBCDE operon . Computer analysis of bacterial genome databases identified the presence of orthologues of the acnA gene (encodes aconitase A) in a number of putative prp operons . Homogeneous AcnA protein of S . enterica had strong aconitase activity and catalyzed the hydration of the 2-methyl-cis-aconitate to yield 2-methylisocitrate . The purification of this enzyme allows the complete reconstitution of the 2-methylcitric acid cycle in vitro using homogeneous preparations of the PrpE, PrpC, PrpD, AcnA, and PrpB enzymes . However, inactivation of the acnA gene did not block growth of S . enterica on propionate as carbon and energy source . The existence of a redundant aconitase activity (encoded by acnB) was postulated to be responsible for the lack of a phenotype in acnA mutant strains . Consistent with this hypothesis, homogeneous AcnB protein of S . enterica also had strong aconitase activity and catalyzed the conversion of 2-methyl-cis-aconitate into 2-methylisocitrate . To address the involvement of AcnB in propionate catabolism, an acnA and acnB double mutant was constructed, and this mutant strain cannot grow on propionate even when supplemented with glutamate . The phenotype of this double mutant indicates that the aconitase enzymes are required for the 2-methylcitric acid cycle during propionate catabolism.

Int J Food Microbiol, 2001 Mar 20, 64(3), 401 - 5
Survival of Escherichia coli O157:H7 and Salmonella on chill-stored vacuum or carbon dioxide packaged primal beef cuts; Dykes GA et al.; The ability of two Escherichia coli O157:H7 strains (E27, a cattle isolate, and B6-914 gfp-91, a fluorescent marker strain) and two Salmonella serotypes (S . typhimurium and S . brandenberg) to survive on chilled preservatively packaged primal beef cuts was examined . Each of the strains was inoculated separately at two dilution levels (10(3) and 10(5) cfu g(-1)) onto 500 g beef steaks, packaged under vacuum or 100% carbon dioxide, and stored, with uninoculated controls, for 6 weeks at - 1.5 degrees C, then for 2 weeks at 4 degrees C . Bacterial numbers were determined by dilution and incubation at 37 degrees C for 24 h on either Sorbitol McConkey Agar or Xylose Lysine Desoxycholate Agar for E . coli O157:H7 and Salmonella samples, respectively . Counts were corrected for background growth and their accuracy checked using immunological tests . Fluorescent E . coli O157:H7 B6-914 gfp-91 was also counted under ultra-violet light . No significant changes in numbers of the E . coli O157:H7 or Salmonella strains occurred during storage at either - 1.5 or 4 degrees C packaged under either vacuum or carbon dioxide . The ability of these pathogens to survive standard preservative packaging conditions is different from that reported from their generic counterparts and therefore a cause for public health concern.

Int J Food Microbiol, 2001 Mar 20, 64(3), 395 - 9
Detection of Salmonella enteritidis in shell and liquid eggs using enrichment and plating; Hara-Kudo Y et al.; Detection methods using various enrichment and plating media and immunoconcentration for Salmonella enteritidis in shell and liquid eggs were evaluated . For liquid egg samples naturally contaminated with S . enteritidis, pre-enrichment in 225 ml of buffered peptone water with cysteine followed by selective enrichment in 10 ml of tetrathionate broth was the superior, resulting in the detection of S . enteritidis in all samples on six of the seven types of selective agar substrate investigated . This enrichment procedure also enabled detection of S . enteritidis in most of artificially inoculated shell egg and pasteurized liquid egg samples.

Int J Food Microbiol, 2001 Mar 20, 64(3), 387 - 93
Evaluation of motility enrichment on modified semi-solid Rappaport-Vassiladis medium (MSRV) for the detection of Salmonella in foods; Worcman-Barnink D et al.; The detection and identification of Salmonella spp . is still troublesome and time consuming to the food industry . Employing the modified semi-solid Rappaport-Vassiliadis medium (MSRV), presumptive results for Salmonella can be obtained in 48 h, representing an interesting alternative to the standard methods . The specificity and sensitivity of the MSRV method were evaluated in this research . The efficiency of this method was also compared with the methodology recommended by the US Food and Drug Administration (FDA) using bismuth sulfite agar, XLT4 agar and Rambach agar . A total of 146 food samples comprised of 41 chicken thighs, 35 Brazilian fresh pork sausages, 35 samples of cocoa powder and/or granulated cocoa and 35 samples of grated fresh coconut, were examined . Overall, the rapid method (direct + indirect) and the standard culture detected 96.1% and 84.6% of the positive samples, respectively . No Salmonella was detected in the coconut or cocoa samples by any of the methods . Eighteen (43.9%) chicken thigh samples were contaminated with the microorganism . The rapid method (direct + indirect) and the standard culture detected 94.4% and 88.9% of these, respectively . Salmonella was detected in eight (22.8%) fresh pork sausage samples . The MSRV method detected Salmonella in all eight samples, while the standard gave positive results in six (75%) . When compared with the standard method, the indirect method showed 86.4% sensitivity and 96.8% specificity, while the direct MSRV showed a sensitivity of 71.4% and specificity of 99.2% . Combined, both MSRV methods showed 95.5% sensitivity and 96.8% specificity . The MSRV medium also reduces the time necessary for the isolation of Salmonella from foods.

Int J Food Microbiol, 2001 Mar 20, 64(3), 237 - 45
Characterization of south african isolates of Salmonella enteritidis by phage typing, numerical analysis of RAPD-PCR banding patterns and plasmid profiles; Mare L et al.; Eleven of the 33 strains of Salmonella enteritidis (S.E.) included in this study belonged to phage type 34 . Six strains belonged to phage type 14, six strains to phage type 4 and four strains to phage type 7 . The remaining six strains belonged to phage types 35, 1, 24var (a variation of phage type 24), 9a, 1b and an unknown phage type . The majority of S.E . phage type 34 strains (eight of the 11) grouped at R2 > or =0.45 into one RAPD-PCR cluster with two strains of phage types 4, a strain of phage type 24var and a strain of phage type 9a, indicating that they consist of a genetically heterogeneous collection of strains . Two of the remaining three phage type 34 strains grouped into two different clusters, well separated from the other phage type 34 strains . One strain of phage type 34 was genetically diverse and did not cluster with any of the strains included in this study . Three of the phage type 14 strains grouped into cluster 11 at R2 > or =0.72, suggesting that they are genetically closely related . However, the remaining three strains of phage type 14 grouped into two separate clusters . Strains of phage types 7, 35, and 1 grouped in one cluster at R2 > or = 0.55 . Our results clearly indicated that S.E . strains of the same phage type are not always genetically related . On the other hand, strains of a high genetic relatedness classified as different phage types . No specific plasmid profile could be linked to any of the phage types . Based on results obtained by LD50 virulence tests, strains containing the 38 MDa plasmid are more virulent compared to strains which do not contain the plasmid.

Inflammation, 2001 Feb, 25(1), 7 - 15
Differential activation of signal transduction pathways mediating phagocytosis, oxidative burst, and degranulation by chicken heterophils in response to stimulation with opsonized Salmonella enteritidis; Kogut MH et al.; The activation of signal transduction pathways is required for the expression of functional enhancement of cellular activities . In the present studies, initial attempts were made to identify the signal transduction factors involved in activating phagocytosis, generation of an oxidative burst, and degranulation by heterophils isolated from neonatal chickens in response to opsonized Salmonella enteritidis (opsonized SE) . Peripheral blood heterophils were isolated and exposed to known inhibitors of signal transduction pathways for either 20 min (staurosporin, genistein, or verapamil) or 120 min (pertussis toxin) at 39 degrees C . The cells were then stimulated for 30 min at 39 degrees C with opsonized SE . Phagocytosis, luminol-dependent chemoluminescence (LDCL), and beta-D glucuronidase release were then evaluated in vitro . The G-protein inhibitor pertussin toxin markedly inhibited (>80%) phagocytosis of opsonized SE . Both the protein kinase inhibitor (staurosporin) and calcium channel inhibitor (verapamil) reduced phagocytosis in a dose response manner . Genistein, a tyrosine kinase inhibitor, had no effect on phagocytosis . Staurosporin had a marked inhibitory effect on LDCL (>90%) while genistein had a dose responsive inhibition on LDCL . Both verapamil (40-45%) and pertussin toxin (50-55%) had a statistically significant, but less biologically significant effect on LDCL . Genistein significantly reduced the degranulation (78-81%) of heterophils by opsonized SE . Staurosporin also reduced degranulation by 43-50%, but neither verapamil nor pertussis toxin had a significant effect on degranulation . These findings demonstrate that distinct signal transduction pathways differentially regulate the stimulation of the functional activities of avian heterophils . Pertussin toxin-sensitive, Ca++-dependent G-proteins appear to regulate phagocytosis of opsonized SE, protein kinase C-dependent, tyrosine kinase-dependent protein phosphorylation plays a major role in LDCL, and tyrosine kinase(s)-dependent phosphorylation regulates primary granule release.

Microbiol Immunol, 2001, 45(2), 149 - 58
Vi-Suppressed wild strain Salmonella typhi cultured in high osmolarity is hyperinvasive toward epithelial cells and destructive of Peyer's patches; Zhao L et al.; Salmonella typhi GIFU10007-3 which lost a viaB locus on its chromosome became highly invasive in our previous study . To investigate the phenomenon, we controlled Vi expression in wild strain S . typhi GIFU10007, and studied the invasive phenotype both in vitro and in vivo . When the wild strain of S . typhi was cultured in 300 mM NaCl containing Luria-Bertani broth (LBH), the expression of Vi antigen was suppressed, but secretion of invasion proteins (SipC, SipB and SipA) was increased . In this condition, wild strain S . typhi became highly invasive toward both epithelial cells and M cells of rat Peyer's patches . When GIFU10007 was cultured under conditions of high osmolarity, the bacteria disrupted Peyer's patches and induced massive bleeding in these structures only 20 min after inoculation into the ileal loop . In contrast, Vi-encapsulated wild strain GIFU10007 cultured under low osmolarity was not destructive, even after 60 min . To understand the role of the type III secretion system under conditions of high osmolarity, we knocked out the invA and sipC genes of both GIFU10007 and GIFU10007-3 . Neither invA nor sipC mutants could invade epithelial cells or M cells in a high osmolarity environment . Our data show that the highly invasive phenotype was only expressed when the wild strain S . typhi was cultured under high osmolarity, which induced a state of Vi suppression, and in the presence of the type III secretion system.

J Bacteriol, 2001 May, 183(9), 2852 - 8
Low-molecular-weight plasmid of Salmonella enterica serovar Enteritidis codes for retron reverse transcriptase and influences phage resistance; Rychlik I et al.; Retron reverse transcriptases are unusual procaryotic enzymes capable of synthesis of low-molecular-weight DNA by reverse transcription . All of the so-far-described DNA species synthesized by retron reverse transcriptases have been identified as multicopy single-stranded DNA . We have shown that Salmonella enterica serovar Enteritidis is also capable of synthesis of the low-molecular-weight DNA by retron reverse transcriptase . Surprisingly, Salmonella serovar Enteritidis-produced low-molecular-weight DNA was shown to be a double-stranded DNA with single-stranded overhangs (sdsDNA) . The sdsDNA was 72 nucleotides (nt) long, of which a 38-nt sequence was formed by double-stranded DNA with 19- and 15-nt single-stranded overhangs, respectively . Three open reading frames (ORFs), encoded by the 4,053-bp plasmid, were essential for the production of sdsDNA . These included an ORF with an unknown function, the retron reverse transcriptase, and an ORF encoding the cold shock protein homologue . This plasmid was also able to confer phage resistance onto the host cell by a mechanism which was independent of sdsDNA synthesis.

J Bacteriol, 2001 May, 183(9), 2733 - 45
Roles of hilC and hilD in regulation of hilA expression in Salmonella enterica serovar Typhimurium; Lucas RL et al.; Sequences between -332 and -39 upstream of the hilA promoter are required for repression of hilA . An unidentified repressor is thought to bind these upstream repressing sequences (URS) to inhibit hilA expression . Two AraC-like transcriptional regulators encoded on Salmonella pathogenicity island 1 (SPI1), HilC and HilD, bind to the URS to counteract the repression of hilA . The URS is required for regulation of hilA by osmolarity, oxygen, PhoP/PhoQ, and SirA/BarA . Here, we show that FadD, FliZ, PhoB, and EnvZ/OmpR also require the URS to regulate hilA . These environmental and regulatory factors may affect hilA expression by altering the expression or activity of HilC, HilD, or the unknown repressor . To begin investigating these possibilities, we tested the effects of environmental and regulatory factors on hilC and hilD expression . We also examined hilA regulation when hilC or hilD was disrupted or expressed to a high level . Although hilC is regulated by all environmental conditions and regulatory factors that modulate hilA expression, hilC is not required for the regulation of hilA by any conditions or factors except EnvZ/OmpR . In contrast, hilD is absolutely required for hilA expression, but environmental conditions and regulatory factors have little or no effect on hilD expression . We speculate that EnvZ/OmpR regulates hilA by altering the expression and/or activity of hilC, while all other regulatory conditions and mutations regulate hilA by modulating hilD posttranscriptionally . We also discuss models in which the regulation of hilA expression is mediated by modulation of the expression or activity of one or more repressors.

Infect Immun, 2001 May, 69(5), 3164 - 74
Disruption of the genes for ClpXP protease in Salmonella enterica serovar Typhimurium results in persistent infection in mice, and development of persistence requires endogenous gamma interferon and tumor necrosis factor alpha; Yamamoto T et al.; The enteric pathogen Salmonella enterica serovar Typhimurium, similar to other facultative intracellular pathogens, has been shown to respond to the hostile conditions inside macrophages of the host organism by producing a set of stress proteins that are also induced by various environmental stresses . The stress-induced ClpXP protease is a member of the ATP-dependent proteases, which are known to be responsible for more than 90% of all proteolysis in Escherichia coli . To investigate the contribution of the ClpXP protease to the virulence of serovar Typhimurium we initially cloned the clpP and clpX operon from the pathogenic strain serovar Typhimurium chi3306 and then created insertional mutations in the clpP and/or clpX gene . The Delta clpP and Delta clpX mutants were used to inoculate BALB/c mice by either the intraperitoneal or the oral route and found to be limited in their ability to colonize organs of the lymphatic system and to cause systemic disease in the host . A variety of experiments were performed to determine the possible reasons for the loss of virulence . An oxygen-dependent killing assay using hydrogen peroxide and paraquat (a superoxide anion generator) and a serum killing assay using murine serum demonstrated that all of the serovar Typhimurium Delta clpP and Delta clpX mutants were as resistant to these killing mechanisms as the wild-type strain . On the other hand, the macrophage survival assay revealed that all these mutants were more sensitive to the intracellular environment than the wild-type strain and were unable to grow or survive within peritoneal macrophages of BALB/c mice . In addition, it was revealed that the serovar Typhimurium ClpXP-depleted mutant was not completely cleared but found to persist at low levels within spleens and livers of mice . Interferon gamma-deficient mice and tumor necrosis factor alpha-deficient mice failed to survive the attenuated serovar Typhimurium infections, suggesting that both endogenous cytokines are essential for regulation of persistent infection with serovar Typhimurium.

Infect Immun, 2001 May, 69(5), 3110 - 9
Stable transfection of the bovine NRAMP1 gene into murine RAW264.7 cells: effect on Brucella abortus survival; Barthel R et al.; Genetically based natural resistance to brucellosis in cattle provides for novel strategies to control zoonotic diseases . Bovine NRAMP1, the homologue of a murine gene (Bcg), has been identified as a major candidate for controlling the in vivo resistant phenotype . We developed an in vitro model for expression of resistance- and susceptibility-associated alleles of bovine NRAMP1 as stable transgenes under the regulatory control of the bovine NRAMP1 promoter in the murine RAW264.7 macrophage cell line (Bcg(s)) to analyze the regulation of the NRAMP1 gene and its role in macrophage function . We demonstrated that the 5'-flanking region of bovine NRAMP1, despite the lack of TATA and CAAT boxes, has a functional promoter capable of driving the expression of a transgene in murine macrophages . A polymorphism within a microsatellite in the 3' untranslated region critically affects the expression of bovine NRAMP1 and the control of in vitro replication of Brucella abortus but not Salmonella enterica serovar Dublin . We did not observe any differences in the production of NO by resting or gamma interferon (IFN-gamma)- and IFN-gamma-lipopolysaccharide (LPS)-treated transfected cell lines, yet the resistant transfected cell lines produced significantly less NO than other cell lines, following stimulation with LPS at 24 and 48 h.

Infect Immun, 2001 May, 69(5), 3100 - 9
Antibodies against listerial protein 60 act as an opsonin for phagocytosis of Listeria monocytogenes by human dendritic cells; Kolb-Maurer A et al.; Human-monocyte-derived dendritic cells (MoDC) are very efficient in the uptake of Listeria monocytogenes, a gram-positive bacterium which is an important pathogen in humans and animals causing systemic infections with symptoms such as septicemia and meningitis . In this work, we analyzed the influence of blood plasma on the internalization of L . monocytogenes into human MoDC and compared the uptake of L . monocytogenes with that of Salmonella enterica serovar Typhimurium and Yersinia enterocolitica . While human plasma did not significantly influence the uptake of serovar Typhimurium and Y . enterocolitica by human MoDC, the efficiency of the uptake of L . monocytogenes by these phagocytes was strongly enhanced by human plasma . In plasma-free medium the internalization of L . monocytogenes was very low, whereas the addition of pooled human immunoglobulins resulted in the internalization of these bacteria to a degree comparable to the highly efficient uptake observed with human plasma . All human plasma tested contained antibodies against the 60-kDa extracellular protein of L . monocytogenes (p60), and anti-p60 antibodies were also found in the commercially available pooled immunoglobulins . Strikingly, in contrast to L . monocytogenes wild type, an iap deletion mutant (totally deficient in p60) showed only a minor difference in the uptake by human MoDC in the presence or the absence of human plasma . These results support the assumption that antibodies against the listerial p60 protein may play an important role in Fc-receptor-mediated uptake of L . monocytogenes by human MoDC via opsonization of the bacteria . This process may have a major impact in preventing systemic infection in L . monocytogenes in immunocompetent humans.

Infect Immun, 2001 May, 69(5), 3092 - 9
Salmonella enterica serovar-host specificity does not correlate with the magnitude of intestinal invasion in sheep; Uzzau S et al.; The colonization of intestinal and systemic tissues by Salmonella enterica serovars with different host specificities was determined 7 days after inoculation of 1 to 2-month-old lambs . Following oral inoculation, S . enterica serovars Abortusovis, Dublin, and Gallinarum were recovered in comparable numbers from the intestinal mucosa, but serovar Gallinarum was recovered in lower numbers than the other serovars from systemic sites . The pattern of bacterial recovery from systemic sites following intravenous inoculation was similar . The magnitude of intestinal invasion was evaluated in ovine ligated ileal loops in vivo . Serovars Dublin and Gallinarum and the broad-host-range Salmonella serovar Typhimurium were recovered in comparable numbers from ileal mucosa 3 h after loop inoculation, whereas the recovery of serovar Abortusovis was approximately 10-fold lower . Microscopic analysis of intestinal mucosae infected with serovars Typhimurium and Dublin showed dramatic morphological changes and infiltration of inflammatory cells, whereas mucosae infected with serovars Abortusovis and Gallinarum were indistinguishable from uninfected mucosae . Together these data suggest that Salmonella serovar specificity in sheep correlates with bacterial persistence at systemic sites . Intestinal invasion and avoidance of the host's intestinal inflammatory response may contribute to but do not determine the specificity of serovar Abortosovis for sheep . Intestinal invasion by serovar Abortusovis was significantly reduced after mutation of invH but was not reduced following curing of the virulence plasmid, suggesting that the Salmonella pathogenicity island 1 influences but the virulence plasmid genes do not influence the ability of serovar Abortusovis to invade the intestinal mucosa in sheep.

Infect Immun, 2001 May, 69(5), 3021 - 30
Flagellar phase variation of Salmonella enterica serovar Typhimurium contributes to virulence in the murine typhoid infection model but does not influence Salmonella-induced enteropathogenesis; Ikeda JS et al.; Although Salmonella enterica serovar Typhimurium can undergo phase variation to alternately express two different types of flagellin subunit proteins, FljB or FliC, no biological function for this phenomenon has been described . In this investigation, we constructed phase-locked derivatives of S . enterica serovar Typhimurium that expressed only FljB (termed locked-ON) or FliC (termed locked-OFF) . The role of phase variation in models of enteric and systemic pathogenesis was then evaluated . There were no differences between the wild-type parent strain and the two phase-locked derivatives in adherence and invasion of mouse epithelial cells in vitro, survival in mouse peritoneal macrophages, or in a bovine model of gastroenteritis . By contrast, the locked-OFF mutant was virulent in mice following oral or intravenous (i.v.) inoculation but the locked-ON mutant was attenuated . When these phase-locked mutants were compared in studies of i.v . kinetics in mice, similar numbers of the two strains were isolated from the blood and spleens of infected animals at 6 and 24 h . However, the locked-OFF mutant was recovered from the blood and spleens in significantly greater numbers than the locked-ON strain by day 2 of infection . By 5 days postinfection, a majority of the mice infected with the locked-OFF mutant had died compared with none of the mice infected with the locked-ON mutant . These results suggest that phase variation is not involved in the intestinal stage of infection but that once S . enterica serovar Typhimurium reaches the spleens of susceptible mice those organisms in the FliC phase can grow and/or survive better than those in the FljB phase . Additional experiments with wild-type S . enterica serovar Typhimurium, fully capable of switching flagellin type, supported this hypothesis . We conclude that organisms that have switched to the FliC(+) phase have a selective advantage in the mouse model of typhoid fever but have no such advantage in invasion of epithelial cells or the induction of enteropathogenesis.

Infect Immun, 2001 May, 69(5), 2894 - 901
Salmonella enterica serovar Typhi possesses a unique repertoire of fimbrial gene sequences; Townsend SM et al.; Salmonella enterica serotype Typhi differs from nontyphoidal Salmonella serotypes by its strict host adaptation to humans and higher primates . Since fimbriae have been implicated in host adaptation, we investigated whether the serotype Typhi genome contains fimbrial operons which are unique to this pathogen or restricted to typhoidal Salmonella serotypes . This study established for the first time the total number of fimbrial operons present in an individual Salmonella serotype . The serotype Typhi CT18 genome, which has been sequenced by the Typhi Sequencing Group at the Sanger Centre, contained a type IV fimbrial operon, an orthologue of the agf operon, and 12 putative fimbrial operons of the chaperone-usher assembly class . In addition to sef, fim, saf, and tcf, which had been described previously in serotype Typhi, we identified eight new putative chaperone-usher-dependent fimbrial operons, which were termed bcf, sta, stb, ste, std, stc, stg, and sth . Hybridization analysis performed with 16 strains of Salmonella reference collection C and 22 strains of Salmonella reference collection B showed that all eight putative fimbrial operons of serotype Typhi were also present in a number of nontyphoidal Salmonella serotypes . Thus, a simple correlation between host range and the presence of a single fimbrial operon seems at present unlikely . However, the serotype Typhi genome differed from that of all other Salmonella serotypes investigated in that it contained a unique combination of putative fimbrial operons.

Vet Immunol Immunopathol, 2001 Feb 10, 78(3-4), 263 - 77
Bacterially induced activation of interleukin-18 in porcine intestinal mucosa; Foss DL et al.; Interleukin (IL)-18 is a cytokine with structural and functional properties similar to IL-1beta and IL-12, respectively . It is activated by caspase-1 cleavage, like IL-1beta, and induces interferon (IFN)-gamma, like IL-12 . In order to study the role of IL-18 in the immune response to infectious diseases of mucosal surfaces we cloned and expressed porcine IL-18 and developed antibodies to the protein . Porcine IL-18 retains the caspase-1 cleavage site present in other mammalian IL-18 proteins, but has two potential N-linked glycosylation sites not found in those proteins . Porcine interleukin-18 mRNA and protein are expressed in immune tissues including lymph nodes and gut associated lymphoid tissues . Specific cell types containing IL-18 include lung and splenic macrophages, nonadherent spleen cells and intestinal epithelial cells . Although IL-18 transcription is moderately induced by lipopolysaccharide, the magnitude and total expression level are small compared to those of interleukin-1beta . In vivo and ex vivo infection of intestinal mucosa with Salmonella choleraesuis resulted in a decrease in size of IL-18, consistent with cleavage of the preprotein by caspase-1 . Thus, IL-18 is present in mucosal tissues where it could play a role in the immune response to invading pathogens.

J Immunol, 2001 Apr 15, 166(8), 5176 - 82
Production of chemokines in vivo in response to microbial stimulation; Coates NJ et al.; Members of the chemokine gene superfamily are known to play a central role in leukocyte extravasation; however, their involvement in acute inflammation in response to micro-organisms has not yet been well studied . We have therefore investigated the role of murine macrophage-inflammatory protein (muMIP) 1alpha and muMIP-2 in the inflammatory response mounted against the bacteria Salmonella enteritidis and the Sacchromyces cerevisiae cell wall component, zymosan . Leukocyte extravasation was monitored in murine s.c . air pouches . Both agonists induced accumulation of leukocytes in a dose- and time-dependent manner, with the response peaking after 4 h and declining thereafter . The inflammatory exudate comprised mainly neutrophils; however, an increase in eosinophil accumulation was also observed in response to zymosan . The production of both muMIP-1alpha and muMIP-2 increased with time in response to both the agonists, although production was more sustained in response to the bacteria . Prior treatment of mice with neutralizing Abs against muMIP-1alpha or muMIP-2, either alone or in combination, failed to attenuate the accumulation of leukocytes in response to the agonists . In contrast, the anti-muMIP-2 Abs significantly inhibited leukocyte recruitment in response to S . enteritidis in complement-deficient mice . Taken together, these data show that while muMIP-1alpha and muMIP-2 are produced in response to phagocytosis of micro-organisms in s.c . tissue, under these circumstances components of the complement pathway appear to play a dominant role in the recruitment of neutrophils.

J Toxicol Environ Health A, 2001 Apr 6, 62(7), 505 - 21
Antiestrogenicity of clarified slurry oil and two crude oils in a human breast-cancer cell assay; Arcaro KF et al.; Exposure to crude oil and certain petroleum products can be a serious health hazard . Clarified slurry oil (CSO) is a complex mixture of hydrocarbons derived from the processing of crude oil, and is a known systemic and developmental toxicant, mutagen, and carcinogen . In the present study, CSO and two crude oils, Belridge heavy crude oil (BHCO) and Lost Hills light crude oil (LHLCO), were examined for their estrogenic and antiestrogenic properties in a human breast-cancer cell (MCF-7) assay . The MCF-7 focus assay is based on postconfluent cell growth and tissue restructuring, measured as the postconfluent development of multicellular nodules or foci . The mutagenicity indices of BHCO and LHLCO also were determined in a modified Ames Salmonella assay . Oil samples were prepared in dimethyl sulfoxide, resulting in extraction of virtually all of the aromatic compounds including the sulfur- and nitrogen-substituted three- to seven-ring polycyclic aromatic compounds comprising 62.2% of the CSO, 9% of the BHCO, and 2% of the LHLCO by total weight . None of the three samples was estrogenic in the MCF-7 focus assay . In contrast, all of the samples were antiestrogenic; that is, they inhibited the development of foci induced by 1 nM 17beta-estradiol (E2) . The potencies of the oil samples for both antiestrogenicity and mutagenicity were correlated with the percent of polycyclic aromatic compounds they contained . Two potential mechanisms for the observed antiestrogenicity were examined . Radiometric analysis of the catabolism of {3H}E2 in MCF-7 cell cultures demonstrated that all three samples increased catabolism of E2 . Results from a whole-cell estrogen-receptor (ER) binding assay suggested that metabolites of compounds in the oil samples might have competed with {3H}E2 for ER in the MCF-7 cultures . Thus the antiestrogenicity of the oil samples may occur through at least two mechanisms, increased catabolism of E2 and antagonistic binding to ER.

Am J Trop Med Hyg, 2000 May, 62(5), 644 - 8
The epidemiology of typhoid fever in the Dong Thap Province, Mekong Delta region of Vietnam; Lin FY et al.; A population-based surveillance for typhoid fever was conducted in three rural communes of Dong Thap Province in southern Vietnam (population 28,329) for a 12-month-period starting on December 4, 1995 . Cases of typhoid fever were detected by obtaining blood for culture from residents with fever > or = 3 days . Among 658 blood cultures, 56 (8.5%) were positive for Salmonella typhi with an overall incidence of 198 per 10(5) population per year . The peak occurrence was at the end of the dry season in March and April . The attack rate was highest among 5-9 year-olds (531/10(5)/year), and lowest in > 30 year-olds (39/10(5)/year) . The attack rate was 358/10(5)/year in 2-4 year-olds . The isolation of S . typhi from blood cultures was highest (17.4%) in patients with 5 to 6 days of fever . Typhoid fever is highly endemic in Vietnam and is a significant disease in both preschool and school-aged children.

J Med Microbiol, 2001 Apr, 50(4), 385 - 9
Influence of infection of cells with bacteria associated with reactive arthritis on the peptide repertoire presented by HLA-B27; Ringrose JH et al.; Reactive arthritis (ReA) after infections with various gram-negative bacteria is strongly associated with the MHC class I molecule HLA-B27 . It is supposed that the B27 molecule itself plays a role in the pathogenesis of ReA by presenting antigenic peptides to cytotoxic T lymphocytes . The peptide repertoires presented by Salmonella-, Shigella- and non-infected cells were compared to identify such peptides . From the peptides isolated from the B27 molecules of these cells, profiles were generated by reversed-phase chromatography and peaks present in the profiles from infected cells but not in profiles from non-infected cells were studied for their peptide compositions . Some sequences with identity to those in human histone H3, human ribosomal protein S17 and the heavy chain of HLA-B27 itself were detected only in profiles from infected cells . All peptides identified from infected cells contained the B*2705 peptide-binding motif . The data suggest that HLA-B27-positive cells infected with ReA-inducing bacteria show an increased presentation of certain self-peptides . There was no evidence for altered peptide-binding specificity of B27 after infection . However, the interpretations were hampered by the variation in peptide presentation between different experiments.

J Med Microbiol, 2001 Apr, 50(4), 339 - 44
Demonstration of the Rb1 lipopolysaccharide core structure in Salmonella strains with the monoclonal antibody M105; Mansfield LP et al.; The lipopolysaccharide (LPS) from 42 strains representing 19 Salmonella serogroups was differentiated into characteristic ladder-like profiles by SDS-PAGE analysis . The core-specific antibody M105 (Ra, Rb1 and Rb2) was used in an immunoblot assay of SDS-PAGE-separated LPS molecules . The M105 antibody bound to the R-type LPS of 18 of the 20 Salmonella strains tested . The results demonstrate that S . enterica serotype Godesberg, S . Adelaide (one of two strains), S . Milwaukee, S . Niarembe, S . Bere and S . Arizonae (serogroup 63) have an atypical LPS core structure which is Rb1 type.

Biosens Bioelectron, 2000 Jun, 15(3-4), 135 - 41
Rapid and sensitive biosensor for Salmonella; Pathirana ST et al.; The rapid and sensitive detection of Salmonella typhymurium based on the use of a polyclonal antibody immobilized by the Langmuir-Blodgett method on the surface of a quartz crystal acoustic wave device was demonstrated . The binding of bacteria to the surface changed the crystal resonance parameters; these were quantified by the output voltage of the sensor instrumentation . The sensor had a lower detection limit of a few hundred cells/ml, and a response time of < 100 s over the range of 10(2)-10(10) cells/ml . The sensor response was linear between bacterial concentrations of 10(2)-10(7) cells/ml, with a sensitivity of 18 mV/decade . The binding of bacteria was specific with two binding sites needed to bind a single cell . The sensors preserve approximately 75% of their sensitivity over a period of 32 days.

J Med Invest, 2001 Feb, 48(1-2), 88 - 96
Inhibitory effects of bitter melon (Momordica charantia Linn.) on bacterial mutagenesis and aberrant crypt focus formation in the rat colon; Chiampanichayakul S et al.; Antimutagenicity and chemopreventive activity of an 80%-ethanol extract of bitter melon (Momordica charantia Linn.) against the formation of azoxymethane (AOM)-induced aberrant crypt foci (ACF) was investigated . The bitter melon extract was nonmutagenic and inhibited the mutagenicity of heterocyclic amines 2-amino-3,4-dimethylimidazo{4,5-f}quinoline and 2-amino-1-methyl-6-phenylimidazo{4,5-b}pyridine, and aflatoxin B1 in the Salmonella mutation assay . To examine the inhibitory effect of bitter melon on AOM-induced ACF formation, male F344 rats were fed various concentrations of the extract (0.1, 0.5, and 1.0 g/kg body weight) for five weeks during the initiation stage . One week after the administration of the plant extract, rats were subcutaneously given AOM at 15 mg/kg body weight once a week for two weeks . Three rats in each group were sacrificed 12 hr after the second AOM injection to analyze DNA adducts, O6-methylguanine (O6-meG) and N7-methylguanine in the liver and colon . The remaining rats were sacrificed 3 weeks after the second AOM injection to observe ACF . To examine the inhibitory effect of the extract on ACF formation in the postinitiation stage, rats were fed the extract at 0.1 and 1.0 g/kg body weight for 12 weeks starting two weeks after the second AOM injection . Treatment with bitter melon extract significantly inhibited ACF formation in the colon during the initiation stage and dose-dependently decreased the average of O6-meG DNA adduct in the colonic mucosa . During the postinitiation stage, bitter melon extract, at 1.0 g/kg body weight, significantly inhibited ACF formation in the colon, especially the formation of ACF with four or more crypts per focus . These findings suggest that bitter melon is a possible chemopreventive agent against colon carcinogenesis.

J Clin Invest, 2001 Apr, 107(7), 775 - 80
Diverse virulence traits underlying different clinical outcomes of Salmonella infection; Fierer J et al.; Salmonella strains have evolved to infect a wide variety of reptiles, birds, and mammals resulting in many different syndromes ranging from colonization and chronic carriage to acute fatal disease . Adaptation to a large number of different evolutionary niches has undoubtedly driven the high degree of phenotypic and genotypic diversity in Salmonella strains . Differences in LPS and flagellar structure generate the antigenic variation that is reflected in the more than 2,000 known serotypes . Moreover, variations of LPS structure affect the virulence of the strain . The differential expression of various fimbriae by Salmonella is likely to be due to the wide variety of mucosal surfaces that are encountered by various strains, and the host immune response may select for a different expression pattern . As with these surface structures, a variety of other important virulence determinants show a variable distribution in Salmonella strains and also serve to delineate the divergence of the Salmonella lineage from E . coli . The acquisition of the SPI-1 region may have represented the defining genetic event in the separation of the Salmonella and E . coli lineages . The SPI-1 cell invasion function allowed Salmonella to establish a separate niche in epithelial cells . The mgtC locus on SPI-3 is also present in all lineages and facilitates the adaptation of the bacteria to the low Mg2+, low pH environment of the endosome that results from SPI-1-mediated invasion.Subsequent acquisition of SPI-2 allowed Salmonella to manipulate the sorting of the endosome or phagosome, altering the intracellular environment and facilitating bacterial growth within infected cells . The ability to disseminate from the bowel and establish extraintestinal niches is promoted by the spv locus . Since Salmonella proliferates within macrophages and must avoid phagocytosis by neutrophils to establish a systemic infection, the spv genes appear to promote the macrophage phase of the disease process . Here the polymorphism of the spv locus is clearly demonstrated, since the serovars that cause most cases of nontyphoid bacteremia contain the spv genes . The absence of the spv genes from S . typhi is particularly puzzling and is a strong indication that the pathogenesis of typhoid fever is fundamentally different from that of bacteremia due to nontyphoid Salmonella . There is currently no genetic explanation for the phenotype of host adaptation or for the finding that only a few serovars cause the majority of human infections . Based on recent findings that multiple individual virulence genes have a variable distribution in Salmonella, it is unlikely that a single locus will be found to be responsible for these complex biological traits . Instead, a complicated combination of genes are likely to contribute to the overall virulence phenotype.

Ann Trop Paediatr, 2001 Mar, 21(1), 88 - 90
Septic arthritis of the hip caused by Salmonella typhi; Chiu S et al.; We describe septic arthritis of the hip in a child with typhoid fever . The aetiological diagnosis was confirmed by a positive Widal test as well as by isolation of Salmonella typhi from joint aspirate . Treatment with ceftriaxone along with surgical drainage was successful.

Microbiology, 2001 Apr, 147(Pt 4), 861 - 7
Antibody response against Escherichia coli heat-stable enterotoxin expressed as fusions to flagellin; Pereira CM et al.; The heat-stable toxin (ST) produced by enterotoxigenic Escherichia coli strains causes diarrhoea by altering the fluid secretion in intestinal epithelial cells . Here, the effectiveness of a flagellin fusion protein of Salmonella containing a 19-amino-acid sequence derived from the ST sequence (FLA--ST) in generating antibodies capable of neutralizing the toxic activity of ST was evaluated . This fusion protein, and an alternative construction where two cysteine residues in the ST sequence were substituted by alanines (ST(mt)), were delivered to the immune system by three distinct strategies: (i) orally, using an attenuated Salmonella strain expressing FLA--ST; (ii) intraperitoneally, by injection of purified FLA--ST; (iii) orally, using attenuated Salmonella carrying a eukaryotic expression plasmid (pCDNA3) with the gene encoding FLA-ST . The results showed that the flagellin system can be used as a carrier to generate ST-neutralizing antibodies . However, it should be mentioned that humoral immune response against ST was only obtained when the mutated ST sequence was employed . FLA-ST was found to be non-immunogenic when delivered via the oral route with attenuated Salmonella strains . However, a flagellin antibody response was obtained by immunizing mice with Salmonella carrying pCDNA3/FLA-ST(mt) . Oral immunization with Salmonella carrying the eukaryotic expression plasmid (pCDNA3/FLA--ST(mt)) seems to be a promising method to elicit an appropriate response against fusions to flagellin.

J Clin Microbiol, 2001 Apr, 39(4), 1571 - 6
Quantitation of bacteria in bone marrow from patients with typhoid fever: relationship between counts and clinical features; Wain J et al.; Enteric fever is the only bacterial infection of humans for which bone marrow examination is routinely recommended . A prospective study of the concentrations of bacteria in the bone marrow and their relationship to clinical features was conducted with 120 Vietnamese patients with suspected enteric fever, of whom 89 had confirmed typhoid fever . Ninety-three percent of the Salmonella enterica serovar Typhi samples isolated were resistant to ampicillin, chloramphenicol, and co-trimoxazole . For 81 patients with uncomplicated typhoid and satisfactory bone marrow aspirates, the number of serovar Typhi CFU in bone marrow aspirates was a median value of 9 (interquartile range {IQR}, 1 to 85; range, 0.1 to 1,580) compared to 0.3 (IQR, 0.1 to 10; range, 0.1 to 399) CFU/ml in simultaneously sampled blood . The ratio of individual blood counts to bone marrow counts was 10 (IQR, 2.3 to 97.5) . The number of bacteria in blood but not bone marrow was correlated inversely with the duration of preceding fever . Thus, with increasing duration of illness the ratio of bone marrow-to-blood bacterial concentrations increased; the median ratio was 4.8 (IQR, 1 to 27.5) during the first week compared with 158 (IQR, 60 to 397) during the third week . After lysing the host cells, the median ratio of viable bone marrow to blood increased, reflecting the higher concentration of intracellular serovar Typhi in the bone marrow . Effective antibiotic pretreatment had a significantly greater effect in reducing blood counts compared to bone marrow counts (P < 0.001) . Thus, bacteria in the bone marrow of typhoid patients are less affected by antibiotic treatment than bacteria in the blood . The numbers of bacteria in bone marrow correlated negatively with the white blood cell (R = -0.3, P = 0.006) and platelet counts (R = -0.32, P = 0.01) and positively with fever clearance time after treatment (R = 0.4, P < 0.001) . The bacterial load in bone marrow therefore may reflect the clinical course of the infection, and high levels may suppress neutrophil proliferation.

J Clin Microbiol, 2001 Apr, 39(4), 1443 - 8
Use of a LightCycler gyrA mutation assay for rapid identification of mutations conferring decreased susceptibility to ciprofloxacin in multiresistant Salmonella enterica serotype Typhimurium DT104 isolates; Walker RA et al.; A LightCycler-based PCR-hybridization gyrA mutation assay (GAMA) was developed to rapidly detect gyrA point mutations in multiresistant (MR) Salmonella enterica serotype Typhimurium DT104 with decreased susceptibility to ciprofloxacin (MIC, 0.25 to 1.0 mg/liter) . Ninety-two isolates (49 human, 43 animal) were tested with three individual oligonucleotide probes directed against an Asp-87-to-Asn (GAC-->AAC) mutation, an Asp-87-to-Gly (GAC-->GGC) mutation, and a Ser-83-to-Phe (TCC-->TTC) mutation . Strains homologous to the probes could be distinguished from strains that had different mutations by their probe-target melting temperatures . Thirty-seven human and 30 animal isolates had an Asp-87-to-Asn substitution, 6 human and 6 animal isolates had a Ser-83-to-Phe substitution, and 5 human and 2 animal isolates had an Asp-87-to-Gly substitution . The remaining six strains all had mismatches with the three probes and therefore different gyrA mutations . The sequencing of gyrA from these six isolates showed that one human strain and two animal strains had an Asp-87-to-Tyr (GAC-->TAC) substitution and two animal strains had a Ser-83-to-Tyr (TCC-->TAC) substitution . One animal strain had no gyrA mutation, suggesting that this isolate had a different mechanism of resistance . Fifty-eight of the strains tested were indistinguishable by several different typing methods including antibiograms, pulsed-field gel gel electrophoresis, and plasmid profiling, although they could be further subdivided according to gyrA mutation . This study confirmed that MR DT104 with decreased susceptibility to ciprofloxacin from humans and food animals in England and Wales may have arisen independently against a background of clonal spread of MR DT104.

Appl Environ Microbiol, 2001 Apr, 67(4), 1979 - 82
Inhibition of a glucose-limited sequencing fed-batch culture of Salmonella enterica serovar enteritidis by volatile fatty acids representative of the ceca of broiler chickens; van der Wielen PW et al.; The effects of concentrations of volatile fatty acids on an anaerobic, glucose-limited, and pH-controlled growing culture of Salmonella enterica serovar Enteritidis were studied . Suddenly increasing volatile fatty acids to the concentrations representative of the ceca of 15-day-old broiler chickens caused washout of serovar Enteritidis . In contrast, a sudden increase to the volatile fatty acid concentrations representative of the ceca of younger broiler chickens caused a reduction in the biomass but not washout . Gradually increasing volatile fatty acids caused a gradual decrease in the biomass of serovar Enteritidis . We conclude that the concentrations of volatile fatty acids present in the ceca of broilers with a mature microflora can cause washout of serovar Enteritidis in an in vitro system mimicking cecal ecophysiology.

Vaccine, 2001 Apr 6, 19(20-22), 3009 - 18
Enhanced immune responses to viral epitopes by combining macrophage-inducible expression with multimeric display on a Salmonella vector; Chen H et al.; In this study, the immunogenicity of chimeric 987P fimbriae on a Salmonella vaccine strain was improved by optimizing fimbrial expression . The constitutive tetA promoter and the in vivo activated nirB and pagC promoters were evaluated for their use to express two epitopes of the transmissible gastroenteritis virus (TGEV) spike protein carried by fimbriae which were displayed on a Salmonella vaccine strain . Constructs with the pagC promoter were shown to drive increased expression of chimeric 987P fimbriae in macrophages as well as in Mg(2+)-poor media, mimicking a major environmental signal found in Salmonella-containing endocytic vacuoles of macrophages . Mice immunized orally with a Salmonella vaccine strain which expressed chimeric fimbriae from the pagC promoter elicited significantly higher mucosal and systemic immune responses to both the 987P fimbriae and the TGEV epitopes than mice immunized with the same strain hosting a tetA or nirB promoter-driven expression plasmid . Moreover, only the Salmonella vaccine strains harboring a plasmid with the pagC promoter, with or without an additional tetA promoter in tandem, elicited neutralizing antibodies to TGEV . This indicated that the pagC promoter can be used successfully to improve epitope-display by chimeric fimbriae on Salmonella vaccine strains for the induction of a desired immune response.

Pathology, 2001 Feb, 33(1), 66 - 72
Practical evaluation of molecular subtyping and phage typing in outbreaks of infection due to Salmonella enterica serotype typhimurium; Jeoffreys NJ et al.; Identification and control of food-poisoning outbreaks due to salmonellosis depend on prompt microbiological diagnosis and subtyping to identify the causative strain . In Australia, Salmonella enterica subspecies enterica serotype typhimurium (S . typhimurium) is responsible for 40-70% of cases of human salmonellosis . Phage typing is the usual method of subtyping S . typhimurium, but on its own, has limitations . We compared it with three molecular subtyping methods using 100 isolates of S . typhimurium, representing four different phage types (PT 1, 9, 126 and 135) and comprising 74 isolates from three presumed outbreaks, 25 isolates from sporadic cases of salmonellosis and S . typhimurium ATCC 10428 (phage type 126) . The isolates were divided into 11 subtypes by IS200 restriction fragment length polymorphism (RFLP) typing, four each by ribotyping and pulsed-field gel electrophoresis (PFGE) and 17 distinct strains using a combination of phage and molecular typing . Isolates from two presumed outbreaks were resolved into multiple strains, possibly explaining the failure to identify a common source for either during the original investigations . IS200 RFLP analysis was the most discriminatory and reproducible typing method . Several strains were identifiable within and shared between phage types 1, 9 and 126 . Phage and IS200 RFLP typing together, would provide improved definition of S . typhimurium outbreaks.

Vet Microbiol, 2001 May 3, 80(1), 85 - 98
Molecular epidemiology of Salmonella Heidelberg in an equine hospital; Amavisit P et al.; From 1992 to 1997, multi-drug resistant (MDR) Salmonella Heidelberg isolates were cultured from a number of horses hospitalised in a veterinary hospital in Victoria, Australia . To examine the relationships between the cases, 28 isolates from the hospital were compared by pulsed field gel electrophoresis (PFGE), IS200 element profiles, antimicrobial resistance patterns, plasmid profiles and phage typing . The PFGE patterns following digestion with XbaI and BlnI restriction endonucleases showed that the isolates from the veterinary hospital originated from a common source . These isolates also had indistinguishable IS200 profiles . However, PFGE was more discriminatory than IS200 profiles . All the veterinary hospital isolates and one independent isolate had the same antimicrobial resistance pattern and had at least one plasmid in common . Localisation of antimicrobial resistance genes indicated that the veterinary hospital isolates had more than one plasmid carrying resistance genes and that the genes encoding sulphathiazole and trimethoprim resistance were not on these plasmids . Phage typing was ineffective as 22 of the 28 isolates were untypeable . In conclusion, the combination of different methods used for epidemiological studies suggested that a single strain of MDR S . Heidelberg was isolated from horses admitted to the hospital for 6 years and caused salmonellosis in susceptible horses within that period with no apparent correlation between the antimicrobials used and retention of its MDR phenotype.

J Bacteriol, 2001 Apr, 183(8), 2682 - 5
glnD and mviN are genes of an essential operon in Sinorhizobium meliloti; Rudnick PA et al.; To evaluate the role of uridylyl-transferase, the Sinorhizobium meliloti glnD gene was isolated by heterologous complementation in Azotobacter vinelandii . The glnD gene is cotranscribed with a gene homologous to Salmonella mviN . glnD1::Omega or mviN1::Omega mutants could not be isolated by a powerful sucrose counterselection procedure unless a complementing cosmid was provided, indicating that glnD and mviN are members of an indispensable operon in S . meliloti.

J Bacteriol, 2001 Apr, 183(8), 2586 - 94
Yersinia pestis pFra shows biovar-specific differences and recent common ancestry with a Salmonella enterica serovar Typhi plasmid; Prentice MB et al.; Population genetic studies suggest that Yersinia pestis, the cause of plague, is a clonal pathogen that has recently emerged from Yersinia pseudotuberculosis . Plasmid acquisition is likely to have been a key element in this evolutionary leap from an enteric to a flea-transmitted systemic pathogen . However, the origin of Y . pestis-specific plasmids remains obscure . We demonstrate specific plasmid rearrangements in different Y . pestis strains which distinguish Y . pestis bv . Orientalis strains from other biovars . We also present evidence for plasmid-associated DNA exchange between Y . pestis and the exclusively human pathogen Salmonella enterica serovar Typhi.

J Bacteriol, 2001 Apr, 183(8), 2463 - 75
The alternative electron acceptor tetrathionate supports B12-dependent anaerobic growth of Salmonella enterica serovar typhimurium on ethanolamine or 1,2-propanediol; Price-Carter M et al.; Synthesis of cobalamin de novo by Salmonella enterica serovar Typhimurium strain LT2 and the absence of this ability in Escherichia coli present several problems . This large synthetic pathway is shared by virtually all salmonellae and must be maintained by selection, yet no conditions are known under which growth depends on endogenous B12 . The cofactor is required for degradation of 1,2-propanediol and ethanolamine . However, cofactor synthesis occurs only anaerobically, and neither of these carbon sources supports anaerobic growth with any of the alternative electron acceptors tested thus far . This paradox is resolved by the electron acceptor tetrathionate, which allows Salmonella to grow anaerobically on ethanolamine or 1,2-propanediol by using endogenously synthesized B12 . Tetrathionate provides the only known conditions under which simple cob mutants (unable to make B12) show a growth defect . Genes involved in this metabolism include the ttr operon, which encodes tetrathionate reductase . This operon is globally regulated by OxrA (Fnr) and induced anaerobically by a two-component system in response to tetrathionate . Salmonella reduces tetrathionate to thiosulfate, which it can further reduce to H2S, by using enzymes encoded by the genes phs and asr . The genes for 1,2-propanediol degradation (pdu) and B12 synthesis (cob), along with the genes for sulfur reduction (ttr, phs, and asr), constitute more than 1% of the Salmonella genome and are all absent from E . coli . In diverging from E . coli, Salmonella acquired some of these genes unilaterally and maintained others that are ancestral but have been lost from the E . coli lineage.

Microb Drug Resist, 2000 Winter, 6(4), 319 - 25
Antimicrobial drug resistance in non-typhoidal salmonellas from humans in England and Wales in 1999: decrease in multiple resistance in Salmonella enterica serotypes Typhimurium, Virchow, and Hadar; Threlfall EJ et al.; In 1999 the incidence of multiple drug resistance (to four or more antimicrobials) in non-typhoidal salmonellas from humans in England and Wales fell in isolations of Salmonella enterica serotypes Typhimurium, Virchow, and Hadar . This fall has been most noticeable in S . Typhimurium, where 59% of isolates were multiresistant compared to 81% in 1996 . The main reason for this has been a 75% decline in isolations of multiply-resistant S . Typhimurium definitive phage type (DT) 104 (MR DT104) since 1996 . Nevertheless MR DT104 remains second to S . Enteritidis phage type 4 as the most common strain in cases of human salmonellosis in England and Wales . Multiple resistance has also remained high in S . Hadar, with 49% of isolates resistant to four drugs or more compared to 56% in 1996 . Isolates with decreased sensitivity to ciprofloxacin (minimal inhibitory concentration: 0.25-1.0 mg/L) have increased in incidence in S . Enteritidis, S . Virchow, and S . Hadar; in S . Hadar 70% of isolates were resistant to ciprofloxacin at this level . It is hoped that Codes of Practice introduced by some pharmaceutical companies, governments, professional organisations, and others to combat the unnecessary prophylactic use of fluoroquinolones in animal husbandry will not result in a reduction in the incidence of resistance to ciprofloxacin in salmonella organisms causing infections in humans.

Microb Drug Resist, 2000 Winter, 6(4), 277 - 82
Mutations in the interdomain loop region of the tetA(A) tetracycline resistance gene increase efflux of minocycline and glycylcyclines; Tuckman M et al.; A novel class of tetracyclines, the glycylcyclines, have been shown to be active against bacterial strains harboring genes encoding tetracycline efflux pumps . However, two veterinary Salmonella isolates that carried tetracycline resistance determinants of the tetA(A) class were found to have reduced susceptibility to glycylcyclines, especially two early investigational glycylcyclines, DMG-MINO and DMG-DMDOT . These isolates were also quite resistant to tetracycline and minocycline . The isolates, one a strain of S . cholerasuis and the other, S . typhimurium, both carried the same novel tetA(A) variant, based on DNA sequencing, with one determinant plasmid encoded and the other located on the chromosome . This tetA(A) variant was cloned and shown to provide reduced susceptibility to the glycylcycline class although GAR-936, a glycylcycline currently in clinical development, was the least affected . The novel tetA(A) gene carries two mutations in the largest cytoplasmic loop of the efflux pump, which causes a double frameshift in codons 201, 202, and 203 . This "interdomain region" of the efflux pump has generally been regarded as having no functional role in the efflux of tetracycline but the double frameshift is most likely responsible for the enhanced resistance observed and points to an interaction that was previously unrecognized . Mutants of the tetA(B) class with decreased susceptibility to the glycylcyclines were also generated in vitro . These all carried mutations in the portion of the tetA(B) gene encoding a transmembrane spanning region of the efflux pump . The laboratory-generated mutants point to the tight constraints in substrate recognition of the transmembrane-spanning region and may suggest that it will be the interdomain region of the pump that is likely to be the locus of future glycylcycline resistance mutations as these compounds enter clinical use.

J Food Prot, 2001 Feb, 64(2), 152 - 8
Comparison of chlorine and a prototype produce wash product for effectiveness in killing Salmonella and Escherichia coli O157:H7 on alfalfa seeds; Beuchat LR et al.; Outbreaks of Salmonella and Escherichia coli O157:H7 infections associated with alfalfa and other seed sprouts have occurred with increased frequency in recent years . This study was undertaken to determine the efficacy of a liquid prototype produce wash product (Fit), compared with water and chlorinated water, in killing Salmonella and E . coli O157:H7 inoculated onto alfalfa seeds . We investigated the efficacy of treatments as influenced by seeds from two different lots obtained from two seeds suppliers and by two methods of inoculation . The efficacy of treatments was influenced by differences in seed lots and amount of organic material in the inoculum . Significant (alpha = 0.05) reductions in Salmonella populations on seeds treated with 20,000 ppm of chlorine or Fit for 30 min ranged from 2.3 to 2.5 log10 CFU/g and 1.7 to 2.3 log10 CFU/g, respectively . Reductions (alpha = 0.05) in E . coli O157:H7 ranged from 2.0 to 2.1 log10 CFU/g and 1.7 to more than 5.4 log10 CFU/g of seeds treated, respectively, with 20,000 ppm of chlorine or Fit . Compared with treatment with 200 ppm of chlorine, treatment with either 20,000 ppm of chlorine or Fit resulted in significantly higher reductions in populations of Salmonella and E . coli O157:H7 . None of the treatments eliminated these pathogens as evidenced by their detection on enrichment of treated seeds . Considering the human health and environmental hazards associated with the use of 20,000 ppm of chlorine, Fit provides an effective alternative to chlorine as a treatment to significantly reduce bacterial pathogens that have been associated with alfalfa seeds.

Indian J Med Sci, 2000 Feb, 54(2), 65 - 6
Salmonella senftenberg: ear infection . A case report; Bairy I et al.; A case of Otitis media, a rare complication of Salmonella senftenberg infection is reported.

Nature, 2001 Mar 15, 410(6826), 331 - 7
Structure of the bacterial flagellar protofilament and implications for a switch for supercoiling; Samatey FA et al.; The bacterial flagellar filament is a helical propeller constructed from 11 protofilaments of a single protein, flagellin . The filament switches between left- and right-handed supercoiled forms when bacteria switch their swimming mode between running and tumbling . Supercoiling is produced by two different packing interactions of flagellin called L and R . In switching from L to R, the intersubunit distance ( approximately 52 A) along the protofilament decreases by 0.8 A . Changes in the number of L and R protofilaments govern supercoiling of the filament . Here we report the 2.0 A resolution crystal structure of a Salmonella flagellin fragment of relative molecular mass 41,300 . The crystal contains pairs of antiparallel straight protofilaments with the R-type repeat . By simulated extension of the protofilament model, we have identified possible switch regions responsible for the bi-stable mechanical switch that generates the 0.8 A difference in repeat distance.

FEMS Microbiol Lett, 2001 Mar 15, 196(2), 215 - 21
Monoclonal antibodies of IgA isotype specific for lipopolysaccharide of Salmonella enteritidis: production, purification, characterization and application as serotyping reagents; Iankov ID et al.; Hybridomas secreting immunoglobulin A (IgA) monoclonal antibodies (MAbs) against Salmonella enteritidis lipopolysaccharide (LPS) were generated after mucosal immunization of BALB/c mice with heat killed bacteria . Antigen binding properties and specificity of the produced MAbs were studied in ELISA and immunoblotting with purified LPS . Two IgA MAbs agglutinated all Salmonella OD1 strains and all S . enteritidis clinical isolates . MAb 178H11 recognized O:9 antigen of subserogroup OD1 LPS . MAb 177E6/A9 reacted also with OD3 LPS antigen and agglutinated OD3 strains . These data suggest the existence of different O:9 antigen subspecificities, one presented in subgroup OD1 and the other common for OD1 and OD3 . Thus the produced IgA MAbs prove to be useful reagents, which could differentiate OD1 and OD3 from OD2 strains.

Nucleic Acids Res, 2001 Apr 1, 29(7), 1420 - 5
Enhancement of translation by the epsilon element is independent of the sequence of the 460 region of 16S rRNA; O'Connor M et al.; The epsilon enhancer element is a pyrimidine-rich sequence that increases expression of T7 gene 10 and a number of Escherichia coli mRNAs during initiation of translation and inhibits expression of the recF mRNA during elongation . Based on its complementarity to the 460 region of 16S rRNA, it has been proposed that epsilon exerts its enhancer activity by base pairing to this complementary rRNA sequence . We have tested this model of enhancer action by constructing mutations in the 460 region of 16S rRNA and examining expression of epsilon-containing CAT reporter genes and recF-lacZ fusions in strains expressing the mutant rRNAs . Replacement of the 460 E.coli stem-loop with that of Salmonella enterica serovar Typhimurium or a stem-loop containing a reversal of all 8 bp in the helical region produced fully functional rRNAs with no apparent effect on cell growth or expression of any epsilon-containing mRNA . Our experiments confirm the reported effects of the epsilon elements on gene expression but show that these effects are independent of the sequence of the 460 region of 16S rRNA, indicating that epsilon-rRNA base pairing does not occur.

Evolution Int J Org Evolution, 2001 Jan, 55(1), 33 - 40
Evolutionary adaptation to temperature . VIII . Effects of temperature on growth rate in natural isolates of Escherichia coli and Salmonella enterica from different thermal environments; Bronikowski AM et al.; Are enteric bacteria specifically adapted to the thermal environment of their hosts? In particular, do the optimal temperatures and thermal niches of the bacterial flora reflect seasonal, geographic, or phylogenetic differences in their hosts' temperatures? We examined these questions by measuring the relationship between the temperature-dependent growth rates of enteric bacteria in a free-living ectothermic host . We sampled two species of enteric bacteria (Escherichia coli and Salmonella enterica) from three natural populations of slider turtles (Trachemys scripta elegans) seasonally over two years . Despite pronounced differences in turtle body temperatures at different seasons and in different locations, we found no evidence that the thermal growth profiles of these bacteria mirrored this variation . Optimal temperatures and maximal growth rates in rich medium were nearly the same for both bacterial species (35-36 degrees C, 2.5 doublings per hour) . The thermal niche (defined as the range of temperatures over which 75% of maximal growth rate occurred) was slightly higher for E . coli (28.5-41.0 degrees C) than for S . enterica (27.7-39.8 degrees C), but the niche breadth was about the same for both . We also measured the thermal dependence of growth rate in these same bacterial species isolated from mammalian hosts . Both bacterial species had temperatures of maximal growth and thermal niches that were about 2 degrees C higher than those of their respective conspecifics sampled from turtles; niche breadths were not different . These data suggest that these bacterial species are thermal generalists that do not track fine-scale changes in their thermal environments . Even major differences in body temperatures, as great as those between ectothermic and endothermic hosts, may result in the evolution of rather modest changes in thermal properties.

J Infect Dis, 2001 Apr 15, 183(8), 1295 - 9 Epub 2001 Mar 26.
Serotype distribution of Salmonella isolates from food animals after slaughter differs from that of isolates found in humans; Sarwari AR et al.; If raw meat and poultry are the primary point of entry for Salmonella species into human populations, a correlation might be expected between the serotype distribution of Salmonella species isolated from animals at the time of slaughter and that of isolates found in humans . For 1990-1996, sufficient national data were available to permit such a comparison . A mathematical model was developed to predict serotype distributions of Salmonella isolates among humans on the basis of animal data . There was a significant mismatch between the serotype distributions among humans predicted by the model and those actually observed . This mismatch raises questions about the validity of the "standard" assumptions about Salmonella transmission on which the model was based-namely, that raw animal products are the primary source for human salmonellosis, that the risk of transmission to humans is equal for all food product categories, and that all Salmonella serotypes have an equal ability to cause human illness.

Kansenshogaku Zasshi, 2001 Feb, 75(2), 116 - 23
{Serovar-distribution and drug-resistance of Salmonella strains isolated from domestic and imported cases during 1995-1999 in Tokyo}; Matsushita S et al.; A total of 2,277 non-typhoidal Salmonella strains consisting of 1,807 domestic strains and 470 imported strains isolated from sporadic cases during 1995-1999 in Tokyo, were examined regarding their serovar-distibution and their drug-resistance . The serological typing results showed that the domestic strains were classified into 17 O-groups and 99 serovars, and the imported strains were classified into 12 O-groups and 58 serovars . Among the serovars identified, Salmonella serovar Enteritidis (S . Enteritidis), S . Thompson, S . Hadar, S . Infantis, S . Typhimurium, and S . Litchfield were predominant in the domestic strains, whereas S . Enteritidis, S . Anatum, S . Hadar, and S . Weltevreden were predominant in the imported strains . The drug-resistance test using 9 drugs (CP, TC, SM, KM, ABPC, ST, NA, FOM, and NFLX) showed that 34.0% of the domestic strains and 33.0% of the imported strains were resistant to any of the drugs examined . The serovars of a high resistant rate during this period were S . Blockley (100%), S . Hadar (96.6%), S . Typhimurium (63.6%), and S . Enteritidis (62.2%) in the domestic strains and S . Blockley (100%), S . Hadar (97.1%), S . Rissen (88.9%), S . Emek (83.3%), S . Panama (83.3%), and S . Typhimurium (77.8%) in the imported strains . Drug-resistance patterns of the resistant isolates varied to 60 types . Prevalent patterns recognized were SM, TC.SM, TC, TC.SM.KM.ST, TC.SM.KM, and CP.TC.SM.ABPC in the domestic strains and TC.SM, TC, NA, TC.SM.KM.NA, and TC.SM.NA in the imported strains.

Mol Microbiol, 2001 Mar, 39(6), 1464 - 70
The Salmonella spvB virulence gene encodes an enzyme that ADP-ribosylates actin and destabilizes the cytoskeleton of eukaryotic cells; Lesnick ML et al.; ADP-ribosylating enzymes, such as cholera and diphtheria toxins, are key virulence factors for a variety of extracellular bacterial pathogens but have not been implicated previously during intracellular pathogenesis . Salmonella strains are capable of invading epithelial cells and localizing in macrophages during infection . The spvB virulence gene of Salmonella is required for human macrophage cytotoxicity in vitro and for enhancing intracellular bacterial proliferation during infection . Here, we present evidence that spvB encodes an ADP-ribosylating enzyme that uses actin as a substrate and depolymerizes actin filaments when expressed in CHO cells . Furthermore, site-directed mutagenesis demonstrates that the ADP-ribosylating activity of SpvB is essential for Salmonella virulence in mice . As spvB is expressed by Salmonella strains after invasion of epithelial cells or phagocytosis by macrophages, these results suggest that SpvB functions as an intracellular ADP-ribosylating toxin critical for the pathogenesis of Salmonella infections.

FEMS Microbiol Lett, 2001 Mar 1, 196(1), 7 - 11
Restricted growth of ent(-) and tonB mutants of Salmonella enterica serovar Typhi in human Mono Mac 6 monocytic cells; Gorbacheva VY et al.; Monocytes and macrophages are an important host defense in humans infected with Salmonella enterica serovar Typhi . Bacterial ability to survive in these cells is therefore a crucial virulence characteristic of this pathogen . In this study, we demonstrate that growth of a Salmonella enterica serovar Typhi enterochelin synthesis mutant and a tonB mutant in the human monocyte cell line Mono Mac 6 is restricted compared to that of the parental wild-type Ty2 strain . These results suggest that enterochelin- and TonB-mediated iron uptake plays a role in S . enterica serovar Typhi pathogenesis, and also suggest that mutations in iron uptake may attenuate S . enterica serovar Typhi strains for human beings.

Vaccine, 2001 Mar 21, 19(17-19), 2621 - 8
Recombinant attenuated bacteria for the delivery of subunit vaccines; Gentschev I et al.; Using attenuated intracellular bacteria as carriers, we have developed two different approaches for the delivery of subunit vaccines encoding heterologous antigens . The first system is based on the direct secretion of the heterologous antigens in Gram-negative bacteria via the hemolysin secretion system of Escherichia coli into either phagosome or cytosol of infected cells . The second approach is based on the transport of eukaryotic antigen expression vectors by intracellular bacteria like Listeria and Salmonella into the host cell and here, preferably, into the cytosolic compartment . After release of the plasmid DNA from the bacteria, the plasmid-encoded antigens can be expressed directly by the host cell . Finally, we combined both types of subunit vaccines in one live vector - we equipped Salmonella strains with a phagosomal escape function by utilization of the hemolysin secretion system and used this recombinant vaccine strain for the delivery of a eukaryotic antigen expression vector into the cytosol of macrophages.

Antimicrob Agents Chemother, 2001 Apr, 45(4), 1305 - 8
Multidrug resistance is mediated by large plasmids carrying a class 1 integron in the emergent Salmonella enterica serotype {4,5,12:i:-}; Guerra B et al.; A multidrug-resistant Salmonella enterica serotype {4,5,12:i:-} clone carried a class 1 integron harboring dfrA12 and aadA2 gene cassettes and bla(TEM-1), aac(3)-IV, cmlA1, and tetA genes located in large plasmids of about 140 kb (carrying spv) or 120 kb (lacking spv) . Several segregants, lacking multidrug resistance, contained a plasmid smaller than the parental one and no longer hybridized with probes for the lost resistances . The genes mediating resistance to ampicillin, chloramphenicol, and tetracycline in the {4,5,12:i:-} clone are different from those found in the pentadrug-resistant serotype Typhimurium DT104 clone.

Infect Immun, 2001 Apr, 69(4), 2659 - 65
Curli fibers mediate internalization of Escherichia coli by eukaryotic cells; Gophna U et al.; Curli fibers are adhesive surface fibers expressed by Escherichia coli and Salmonella enterica that bind several host extracellular matrix and contact phase proteins and were assumed to have a role in pathogenesis . The results presented here suggest that one such role is internalization into host cells . An E . coli K-12 strain transformed with a low-copy vector containing the gene cluster encoding curli fibers (csg operon) was internalized by several lines of eukaryotic cells . The internalization could be correlated with a high level of curli fiber expression and was abolished by disruption of the csg operon . The ability to be internalized by eukaryotic cells could be conferred even by the curli fiber gene cluster of a noninvasive K-12 strain, but the homologous csg cluster from a virulent septicemic E . coli isolate mediated a higher level of internalization . The finding that curli fibers promote bacterial internalization indicates a new role for curli fibers in pathogenesis.

Infect Immun, 2001 Apr, 69(4), 2612 - 20
Complete DNA sequence and comparative analysis of the 50-kilobase virulence plasmid of Salmonella enterica serovar Choleraesuis; Haneda T et al.; The complete nucleotide sequence of pKDSC50, a large virulence plasmid from Salmonella enterica serovar Choleraesuis strain RF-1, has been determined . We identified 48 of the open reading frames (ORFs) encoded by the 49,503-bp molecule . pKDSC50 encodes a known virulence-associated operon, the spv operon, which is composed of genes essential for systemic infection by nontyphoidal Salmonella . Analysis of the genetic organization of pKDSC50 suggests that the plasmid is composed of several virulence-associated genes, which include the spvRABCD genes, plasmid replication and maintenance genes, and one insertion sequence element . A second virulence-associated region including the pef (plasmid-encoded fimbria) operon and rck (resistance to complement killing) gene, which has been identified on the virulence plasmid of S . enterica serovar Typhimurium, was absent . Two different replicon regions, similar to the RepFIIA and RepFIB replicons, were found . Both showed high similarity to those of the pO157 plasmid of enterohemorrhagic Escherichia coli O157:H7 and the enteropathogenic E . coli (EPEC) adherence factor plasmid harbored by EPEC strain B171 (O111:NM), as well as the virulence plasmids of Salmonella serovars Typhimurium and Enteritidis . Comparative analysis of the nucleotide sequences of the 50-kb virulence plasmid of serovar Choleraesuis and the 94-kb virulence plasmid of serovar Typhimurium revealed that 47 out of 48 ORFs of the virulence plasmid of serovar Choleraesuis are highly homologous to the corresponding ORFs of the virulence plasmid of serovar Typhimurium, suggesting a common ancestry.

Infect Immun, 2001 Apr, 69(4), 2293 - 301
Salmonella enterica serovar typhimurium induces cell death in bovine monocyte-derived macrophages by early sipB-dependent and delayed sipB-independent mechanisms; Santos RL et al.; It was previously demonstrated that Salmonella enterica serovar Typhimurium induces cell death with features of apoptosis in murine macrophages . Mice infected with Salmonella serovar Typhimurium develop systemic disease without diarrhea, whereas the infection in cattle and in humans is localized and characterized by diarrhea . Considering these clinical disease expression differences between mice and cattle, we investigated whether serovar Typhimurium is cytotoxic for bovine macrophages . Macrophages infected with serovar Typhimurium grown in the logarithmic phase quickly underwent cell death . Macrophages infected with stationary-phase cultures or with a mutant lacking sipB underwent no immediate cell death but did develop delayed cytotoxicity, undergoing cell death between 12 and 18 h postinfection . Both pathways were temporarily blocked by the general caspase inhibitor Z-VAD-Fmk and by the caspase 1 inhibitor Z-YVAD-Fmk . Comparisons of macrophages from cattle naturally resistant or susceptible to intracellular pathogens indicated no differences between these two genetic backgrounds in terms of susceptibility to serovar Typhimurium-induced cell death . We conclude that Salmonella serovar Typhimurium induces cell death in bovine macrophages by two distinct mechanisms, early sipB-mediated and delayed sipB-independent mechanisms.

Infect Immun, 2001 Apr, 69(4), 2154 - 61
Induction of protective immunity against Streptococcus mutans colonization after mucosal immunization with attenuated Salmonella enterica serovar typhimurium expressing an S . mutans adhesin under the control of in vivo-inducible nirB promoter; Huang Y et al.; The purpose of the present study was to evaluate the effectiveness of an attenuated Salmonella enterica serovar Typhimurium vaccine strain expressing the saliva-binding region (SBR) of the Streptococcus mutans antigen I/II adhesin, either alone or linked with the mucosal adjuvant cholera toxin A2 and B subunits (CTA2/B) and under the control of the anaerobically inducible nirB promoter, in inducing a protective immune response against S . mutans infection . BALB/c mice were immunized by either the intranasal or the intragastric route with a single dose of 10(9) or 10(10) Salmonella CFU, respectively . The Salmonella vaccine strain expressing an unrelated antigen (fragment C of tetanus toxin {TetC}) was also used for immunization as a control . Samples of serum and secretion (saliva and vaginal washes) were collected prior to and following immunization and assessed for antibody activity by enzyme-linked immunosorbent assay . Anti-SBR antibodies were detected in the serum and saliva of experimental animals by week 3 after immunization . A booster immunization at week 17 after the initial immunization resulted in enhanced immune responses to the SBR . The serum immunoglobulin G subclass profiles were indicative of T helper type 1 responses against both the vector and the SBR antigen . To determine the effectiveness of these responses on the protection against S . mutans infection, mice were challenged after the second immunization with a virulent strain of S . mutans which was resistant to tetracycline and erythromycin . Prior to the challenge, mice were treated for 5 days with tetracycline, erythromycin, and penicillin . S . mutans was initially recovered from all of the challenged mice . This bacterium persisted at high levels for at least 5 weeks in control TetC-immunized or nonimmunized mice despite the reappearance of indigenous oral organisms . However, mice immunized with Salmonella clones expressing SBR or SBR-CTA2/B demonstrated a significant reduction in the number of S . mutans present in plaque compared to the control groups . These results provide evidence for the effectiveness of the Salmonella vector in delivering the SBR antigen for the induction of mucosal and systemic immune responses to SBR . Furthermore, the induction of a salivary anti-SBR response corresponded with protection against S . mutans colonization of tooth surfaces.

Infect Immun, 2001 Apr, 69(4), 2045 - 53
Synergistic effect of muramyldipeptide with lipopolysaccharide or lipoteichoic acid to induce inflammatory cytokines in human monocytic cells in culture; Yang S et al.; An analog of 1alpha,25-dihydroxyvitamin D3, 22-oxyacalcitriol (OCT), differentiated human monocytic THP-1 and U937 cells to express membrane CD14 and rendered the cells responsive to bacterial cell surface components . Both THP-1 and U937 cells expressed Toll-like receptor 4 (TLR4) on the cell surface and TLR4 mRNA in the cells, irrespective of OCT treatment . In contrast, OCT-treated U937 cells scarcely expressed TLR2 mRNA, while OCT-treated THP-1 cells expressed this transcript . Muramyldipeptide (MDP) by itself exhibited only a weak ability to induce secretion of inflammatory cytokines such as interleukin-8 (IL-8) in the OCT-differentiated THP-1 cells but showed marked synergistic effects with Salmonella lipopolysaccharide (LPS) or lipoteichoic acid (LTA) from Staphylococcus aureus, both of which exhibited strong activities . Combinatory stimulation with LPS plus LTA did not show a synergistic effect on OCT-differentiated THP-1 cells . Similar results were observed in OCT-differentiated U937 cells, although combination experiments were carried out only with MDP plus LPS . Anti-CD14 monoclonal antibody (MAb) MY4, anti-TLR4 MAb HTA125, and the synthetic lipid A precursor LA-14-PP almost completely inhibited the IL-8-inducing activities of LTA as well as LPS on OCT-treated THP-1 cells, but these treatments increased MDP activity . OCT-treated THP-1 cells primed with MDP exhibited enhanced production of IL-8 upon stimulation with LPS, while the cells primed with LPS showed no change in production upon stimulation with MDP . MDP up-regulated mRNA expression of an adapter molecule to TLRs, MyD88, to an extent similar to that for LPS in OCT-treated THP-1 cells . These findings suggested that LTA as well as LPS activated human monocytic cells in a CD14- and TLR4-dependent manner, whereas MDP exhibited activity in a CD14-, TLR4-, and probably TLR2-independent manner and exhibited synergistic and priming effects on the cells for cytokine production in response to various bacterial components.

Am J Physiol Gastrointest Liver Physiol, 2001 Apr, 280(4), G710 - 9
Regulated MIP-3alpha/CCL20 production by human intestinal epithelium: mechanism for modulating mucosal immunity; Izadpanah A et al.; Human intestinal epithelial cells secrete an array of chemokines known to signal the trafficking of neutrophils and monocytes important in innate mucosal immunity . We hypothesized that intestinal epithelium may also have the capacity to play a role in signaling host adaptive immunity . The CC chemokine macrophage inflammatory protein (MIP)-3alpha/CCL20 is chemotactic for immature dendritic cells and CD45RO(+) T cells that are important components of the host adaptive immune system . In these studies, we demonstrate the widespread production and regulated expression of MIP-3alpha by human intestinal epithelium . Several intestinal epithelial cell lines were shown to constitutively express MIP-3alpha mRNA . Moreover, MIP-3alpha mRNA expression and protein production were upregulated by stimulation of intestinal epithelial cells with the proinflammatory cytokines tumor necrosis factor-alpha or interleukin-1alpha or in response to infection with the enteric bacterial pathogens Salmonella or enteroinvasive Escherichia coli . In addition, MIP-3alpha was shown to function as a nuclear factor-kappaB target gene . In vitro findings were paralleled in vivo by increased expression of MIP-3alpha in the epithelium of cytokine-stimulated or bacteria-infected human intestinal xenografts and in the epithelium of inflamed human colon . Mucosal T cells, other mucosal mononuclear cells, and intestinal epithelial cells expressed CCR6, the cognate receptor for MIP-3alpha . The constitutive and regulated expression of MIP-3alpha by human intestinal epithelium is consistent with a role for epithelial cell-produced MIP-3alpha in modulating mucosal adaptive immune responses.

Clin Rheumatol, 2001, 20(1), 53 - 6
Bilateral femoral osteomyelitis with knee arthritis due to Salmonella enteritidis in a patient with systemic lupus erythematosus; Picillo U et al.; A bilateral knee septic arthritis due to Salmonella enteritidis developed in a female patient affected by long-standing systemic lupus erythematosus (SLE) with cardiac and renal involvement treated with immunosuppressants and corticosteroids . Because avascular necrosis and multiple osteomyelitic areas were detected at the same time in both right and left femoral condyles, an early localisation of Salmonella into the bone was assumed . Involvement of the joints was regarded as consequence of local dissemination of infection . Ampicilline (0.2 g/kg body weight daily for 2 months) plus ciprofloxacin (1.5 g daily for 12 months) and withdrawal of immunosuppressants appeared to be effective in preventing complications of infection.

Trop Anim Health Prod, 2001 Apr, 33(2), 95 - 102
An outbreak of Salmonella enteritidis infection in pygmy hogs (Sus salvanius); Rahman H et al.; An outbreak of salmonellosis was recorded in captive pygmy hogs (Sus salvanius), a critically endangered species of mammal . Of 42 captive animals maintained for conservation breeding by the Pygmy Hog Conservation Programme, Guwahati, Assam, India, 7 (16.67%) died within 3 days . The organism associated with this outbreak was identified as Salmonella enteritidis . The organisms were highly susceptible to chloramphenicol, gentamicin, norfloxacin and cefotaxim but were resistant to ampicillin, oxytetracycline, mezlocillin and sulfamerazin . The strain belonged to phage type 13a/7 and harboured two plasmids (38 and 44 megadaltons) . The organisms were enterotoxigenic in CHO cell assay and were found to carry stn, sef and pef genes.

Rev Panam Salud Publica, 2001 Jan, 9(1), 7 - 12
{Phage typing of Salmonella enteritidis isolated from clinical, food, and poultry samples in Chile}; Prat S et al.; Since 1994 an extensive epidemic of infections with Salmonella enteritidis (S . enteritidis) has affected Chile . In order to understand the diversity of infective sources, the possible origin of the epidemic, and the epidemiological relationships between clinical, food, and poultry isolates, we carried out phage typing of three groups of samples: 1) 310 S . enteritidis clinical samples collected between 1975 and 1996, 2) 47 food isolates obtained during S . enteritidis outbreaks, and 3) 27 strains isolated in surveillance studies of poultry-raising establishments . With the clinical samples, a total of 13 phage types were identified, 2 isolates could not be typed, and 1 was considered atypical . The phage types that were identified most frequently were 1 (56.8%) and 4 (31.3%), trailed by type 8 (4.8%) and type 28 (1.9%) . Over time and in different regions of the country there were major changes in the distribution of the phage types . In the first years of collection the only phage types registered were 8 and 28, which disappeared around 1980 and then began reappearing sporadically in 1996 . With the gradual S . enteritidis expansion that started in 1988, in the central and southern areas of the country phage type 4 began to appear; that type had not been found before in Chile . In 1991 in the northern area of the country phage type 1 began to predominate; it was another type that had not been reported before in Chile . In the food isolates the only phage types identified were 1 and 4, which were also the most common in the poultry isolates . Phage typing of S . enteritidis has proved to be useful in guiding the epidemiological analysis of the infections caused by this pathogen.

Int J Food Microbiol, 2001 Feb 28, 64(1-2), 189 - 91
Occurrence of Salmonella spp . in consumption eggs in Poland; Radkowski M; The purpose of this study was to determine the prevalence of Salmonellae on egg shells in markets in Olsztyn, Poland . An investigation carried out by the Sanitary and Epidemiological Station into cases of food poisoning caused in Poland by Salmonella spp . in recent years showed that the largest number of outbreaks is connected with consuming foods containing hens eggs which had not undergone heat treatment, such as mayonnaise, creams, ice-cream and other products . The world egg production amounts to 400 billion, in Poland it reaches the level of around 8 billion per year . A total of 1200 eggs were purchased in 40 local markets in Olsztyn were examined for the presence of Salmonella between June 1997 and December 1998 . Salmonella was not found on the shell or inside the eggs . From this study it would appear that the incidence of Salmonellae on eggs from Olsztyn shops is very low.

J Food Prot, 2001 Mar, 64(3), 410 - 29
Heat resistance of Listeria monocytogenes; Doyle ME et al.; The heat resistance data on Listeria monocytogenes in culture media and foods are summarized . Most heat resistance data for foods have been obtained in dairy, meat, poultry, and egg products . Limited data have been published on seafood, fruits, and vegetables . The methodologies employed have evolved over time; hence data from earlier experiments are not directly comparable to more recent studies . Many factors influence the heat resistance of L . monocytogenes . Variation exists among different strains in their ability to withstand heat treatment . In addition, heat resistance is influenced by age of the culture, growth conditions, recovery media, and characteristics of foods such as salt content, a(w), acidity, and the presence of other inhibitors . Listeriae are more heat resistant than most other nonspore-forming foodborne pathogens, and thus, processing recommendations based on data from experiments with Salmonella spp . or pathogenic Escherichia coli may not be sufficient to eliminate similar numbers of L . monocytogenes . The data provided in this review may prove useful for food processors in determining appropriate times and temperatures for producing foods free of vegetative pathogens.

J Food Prot, 2001 Mar, 64(3), 315 - 20
Thermal inactivation of stationary-phase and acid-adapted Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes in fruit juices; Mazzotta AS; The heat resistance of stationary-phase and acid-adapted Escherichia coli O157:H7, Salmonella enterica (serotypes Typhimurium, Enteritidis, Gaminara, Rubislaw, and Hartford), and Listeria monocytogenes was evaluated in single-strength apple . orange, and white grape juices adjusted to pH 3.9 . The heat resistance increased significantly (P < 0.05) after acid adaptation . Salmonella had an overall lower heat resistance than the other pathogens . Acid-adapted E . coli O157:H7 presented the highest heat resistance in all juices at the temperatures tested, with lower z-values than Salmonella and L . monocytogenes . The heat resistance (D(60 degrees C)-values) of all three pathogens, assessed in tryptic soy broth adjusted to different pH values, increased above pH 4.0 . From the results obtained in this study, one example of a treatment that will inactivate 5 logs of vegetative pathogens was calculated as 3 s at 71.1 degrees C (z-value of 5.3 degrees C) . Normal processing conditions calculated for hot-filled, shelf-stable juices achieve a lethality in excess of 50,000 D for all three pathogens.

J Food Prot, 2001 Mar, 64(3), 310 - 4
Microscopic observation and processing validation of fruit sanitizing treatments for the enhanced microbiological safety of fresh orange juice; Pao S et al.; Studies were conducted to evaluate the infiltration of dye and bacteria into the interior of orange fruit and the impact of possible infiltration on achieving a 5-log microbial reduction during fresh juice processing . Fresh orange fruit were treated at the stem end area with dye and either Salmonella Rubislaw or Escherichia coli strains expressing green fluorescent protein . Microscopic images showed that bacterial contaminants localized at the surface or near surface areas that may be sanitized by surface treatments . Dye infiltration was not a reliable indicator of bacterial penetration in citrus fruit . To quantify the reduction of bacterial contamination, orange fruit were inoculated with E . coli and processed with and without hot water treatments . Greater than 5-log reductions were achieved in juice extracted from fruit immersed in hot water for 1 or 2 min at 80 degrees C, in comparison to the E . coli level detected in the control juice obtained by homogenization of inoculated fruit.

J Food Prot, 2001 Mar, 64(3), 292 - 7
Elution, detection, and quantification of polio I, bacteriophages, Salmonella montevideo, and Escherichia coli O157:H7 from seeded strawberries and tomatoes; Lukasik J et al.; This study compared the effect of different physical and chemical treatments of strawberries and tomatoes to determine their ability to recover seeded viral and bacterial pathogens from produce surfaces . Solutions of salts, amino acids, complex media, and detergents were compared as eluants . Phosphate-buffered saline (PBS) containing 0.1% Tween 80 eluted the highest number of seeded microorganisms . Elution with this defined solution was then compared under different conditions of physical agitation . Rotary shaking for 20 min at 36 degrees C eluted higher numbers of viruses and bacteria than did low- or high-speed stomaching . Commercially available and laboratory prepared bacteriological differential media were compared for their ability to recover and distinguish eluted Salmonella Montevideo and Escherichia coli O157:H7 strains from seeded produce . The recovery of seeded bacterial pathogens was low when differential media containing selective ingredients were used (MacConkey sorbitol agar, XLD agar, MacConkey agar) . Highest recoveries were obtained on a medium consisting of tryptic soy agar supplemented with sodium thiosulfate and ferric ammonium citrate compared with selective media that inhibited up to 50% of the growth of the eluted microorganisms.

Trop Med Int Health, 2001 Jan, 6(1), 55 - 9
Shigella and Salmonella strains isolated from children under 5 years in Gaborone, Botswana, and their antibiotic susceptibility patterns; Urio EM et al.; We isolated Shigella from 43/221 (21%) and Salmonella 8/221 (3%) rectal swabs from children under 5 years with diarrhoea, and found Shigella in two of 100 specimens from children without diarrhoea . Sh . boydii (13%) was the most prevalent Shigella species followed by Sh . flexneri (6%) and Sh . sonnei (2%) . The prevalence of various types of Sh . boydii was type 7, 5%; type 9, 3%; type 12 and 16, 2%; and type 18, 1% . Other Shigella serotypes encountered were Sh . flexneri type 6 (4%), type 4 (2%), with Sh . sonnei phase II isolated from 2% of the specimens . The Salmonella species were S . typhimurium and S . paratyphi . The high rate of isolation of Shigella species from children with diarrhoea is indicative of a definite role of this enteropathogen in causing endemic diarrhoea in Gaborone, Botswana . Antibiograms of the predominant isolates showed that most Shigella species were resistant to ampicillin but susceptible to chloramphenicol, and with the exception of Sh . flexneri type 6, also susceptible to gentamicin . The Salmonella species were susceptible to chloramphenicol, collistin-sulphate, gentamicin, cotrimoxazole, and ampicillin.

Mol Microbiol, 2001 Mar, 39(5), 1382 - 94
Regulation of RpoS by a novel small RNA: the characterization of RprA; Majdalani N et al.; Translational regulation of the stationary phase sigma factor RpoS is mediated by the formation of a double-stranded RNA stem-loop structure in the upstream region of the rpoS messenger RNA, occluding the translation initiation site . The interaction of the rpoS mRNA with a small RNA, DsrA, disrupts the double-strand pairing and allows high levels of translation initiation . We screened a multicopy library of Escherichia coli DNA fragments for novel activators of RpoS translation when DsrA is absent . Clones carrying rprA (RpoS regulator RNA) increased the translation of RpoS . The rprA gene encodes a 106 nucleotide regulatory RNA . As with DsrA, RprA is predicted to form three stem-loops and is highly conserved in Salmonella and Klebsiella species . Thus, at least two small RNAs, DsrA and RprA, participate in the positive regulation of RpoS translation . Unlike DsrA, RprA does not have an extensive region of complementarity to the RpoS leader, leaving its mechanism of action unclear . RprA is non-essential . Mutations in the gene interfere with the induction of RpoS after osmotic shock when DsrA is absent, demonstrating a physiological role for RprA . The existence of two very different small RNA regulators of RpoS translation suggests that such additional regulatory RNAs are likely to exist, both for regulation of RpoS and for regulation of other important cellular components.

Toxicol Sci, 2001 Apr, 60(2), 232 - 41
Metabolism, microflora effects, and genotoxicity in haloacetic acid-treated cultures of rat cecal microbiota; Nelson GM et al.; Haloacetic acids are by-products of drinking water disinfection . Several compounds in this class are genotoxic and have been identified as rodent hepatocarcinogens . Enzymes produced by the normal intestinal bacteria can transform some promutagens and procarcinogens to their biologically active forms . The present study was designed to investigate the influence of the cecal microbiota on the mutagenicity of haloacetic acids, and to look at changes in the microbiota populations and enzyme activities associated with exposure to haloacetic acids . PYG medium containing 1 mg/ml of monochloroacetic (MCA), monobromoacetic (MBA), dichloroacetic (DCA), dibromoacetic (DBA), trichloroacetic (TCA), tribromoacetic (TBA), or bromochloroacetic (BCA) acid was inoculated with rat cecal homogenate and incubated anaerobically at 37 degrees C . Growth curves were performed with enumeration of the microflora populations on selective media . Mutagenicity in a Salmonella microsuspension bioassay was determined after incubation for various lengths of time, with or without the cecal microbiota . At 15 h of incubation, enzyme assays determined the activities for beta-glucuronidase, beta-galactosidase, beta-glucosidase, azoreductase, nitroreductase, dechlorinase, and dehydrochlorinase . The haloacetic acids, with the exception of BCA, were toxic to the cecal microbiota, and especially to the enterococci . DBA, TBA, and BCA were mutagenic in the microsuspension assay, but the presence of the intestinal flora did not significantly alter the mutagenicity . BCA increased the activities of several enzymes, and therefore has the potential to affect the biotransformation of co-exposed compounds.

Clin Infect Dis, 2001 Mar 15, 32(6), 890 - 6 Epub 2001 Mar 14.
Emergence of Salmonella enteritidis phage type 4 in the Caribbean: case-control study in Trinidad and Tobago, West Indies; Indar-Harrinauth L et al.; A prospective case-control study involving 46 case patients and 92 age- and neighborhood-matched control subjects was conducted in Trinidad and Tobago (T&T) between March 1998 and May 1999 to determine the etiology, sources, and risk factors for Salmonella enteritidis (SE) infection . SE infection in T&T was found to be associated with the consumption of shell eggs, and in particular raw or undercooked eggs . SE isolates from 30 (88%) of 34 patients and from 9 implicated egg or egg-containing food samples were phage type 4 . Homemade eggnog and ice cream, cake batter, and egg-containing beverages were the main raw egg-containing foods, reflecting the cultural practices of the people of T&T . Public health education on the risks of eating raw or undercooked eggs, thorough cooking of all egg dishes, and refrigeration of shell eggs and egg dishes; studies tracing infected eggs to their sources; and testing of flocks of layer chickens for SE are needed to reduce the incidence of this infection.

Comp Immunol Microbiol Infect Dis, 2001 Apr, 24(2), 81 - 9
Chlortetracycline modulates acute phase response of ex vivo perfused pig livers, and inhibits TNF-alpha secretion by isolated Kupffer cells; Akunda JK et al.; Tetracyclines have been shown to have anti-inflammatory effects in addition to their antimicrobial action . We investigated the effects of in vivo administration of chlortetracycline (CTC) on ex vivo perfused pig livers . The retention and clearance of Salmonella choleraesuis, production of acute phase proteins C-reactive protein (CRP), and haptoglobin (HPG) by whole livers were studied . The in vitro modulation by CTC of TNF-alpha secretion by pig Kupffer cells (KC) was also studied . Pigs were dosed orally with CTC for three days, and given injections of Salmonella LPS 24 h before removal of the liver . Salmonella retention and clearance by livers of pigs given CTC was lower than by control livers (p < 0.01 and p < 0.05, respectively) . We demonstrated an increase of CRP and HPG by livers from control pigs after a three-hour perfusion while pigs from CTC pretreated pigs varied in this response . Further, CTC decreased the secretion of TNF-alpha by cultured KC incubated in vitro with LPS . Modulation of TNF-alpha production by CTC suggests a potential for attenuating the inflammatory response . However, this possible beneficial action of CTC was accompanied by a significant decline in the antimicrobial effect of the liver.

Int J Food Microbiol, 2001 Feb 15, 63(3), 235 - 41
Effect of different complex carbon sources on growth and bacteriocin synthesis of Enterococcus faecium; Audisio MC et al.; Different criteria are followed in order to select bacteria to be used in probiotic and symbiotic supplements . A new parameter to choose strains could be fermentation by intestinal bacteria of some complex carbohydrates because they are prebiotics and promote the development of beneficial microorganisms in the intestinal environment . An Enterococcus faecium strain, isolated from the crop of a free-range chicken, was assayed in order to determine the utilization of commercial sugars and/or crude carbohydrate samples from a sugar mill . The production of antimicrobial substances, under these conditions, was also considered . Ent . faecium CRL1385 grew well in the presence of complex carbohydrates and its ability to produce bacteriocin, active against poultry pathogens such as Ent . hirae, Salmonella pullorum and Listeria monocytogenes, was not significantly modified . These results are promising because the trend today is to employ eubiotic or symbiotic products and their use in the poultry industry could be a natural way to protect the flocks against potential pathogens.

Int J Food Microbiol, 2001 Feb 15, 63(3), 225 - 33
Automated simultaneous detection of low levels of listeriae and salmonellae in foods; Peng H et al.; Salmonella spp . and Listeria monocytogenes continue to be major pathogens of concern to food processors . However, routine screening of food samples to detect these pathogens is generally labor intensive and costly . Automated optical procedures for the detection of salmonellae and listeriae in foods were developed in our laboratory . In the present study we report their adaptation to a simultaneous recovery and detection procedure . Milk, shell eggs, fresh and ready-to-eat (RTE) meats or raw chicken contaminated with a combination of sub-lethally injured salmonellae and listeriae (10-50 cells each) were incubated for 6 h at 35 degrees C in modified universal pre-enrichment broth (MUPB) . Volumes (4 ml) were then transferred to vials containing selective liquid media for these pathogens (4 ml), and incubated overnight at 35 degrees C in a BioSys instrument . The presence of the pathogens was identified by a black coloration of the media and a sharp drop in light transmittance caused by hydrogen sulfide production (Salmonella organisms), or esculin hydrolysis (Listeria organisms) . There was no difference in the detection time of salmonellae when incubated alone or with listeriae, but listeriae grew at a slower rate in the presence of salmonellae, resulting in a delay of < or = 1 h in their detection . Overall, the detection of 10-50 salmonellae and 10-50 listeriae in 25 g of the tested foods required a total of 24 h . Confirmation of the pathogens by PCR-based assay (6 h) was completed the following day directly from positive vials, requiring a total of < or = 30 h for detection and confirmation . Negative samples required no confirmation . The testing system was confirmed in 70 naturally contaminated foods.

J Periodontal Res, 2001 Feb, 36(1), 25 - 31
Effect of lipopolysaccharide from periodontal pathogens on the production of tissue plasminogen activator and plasminogen activator inhibitor 2 by human gingival fibroblasts; Xiao Y et al.; Both tissue plasminogen activator (t-PA) and plasminogen activator inhibitor 2 (PAI-2) are important proteolysis factors present in inflamed human periodontal tissues . The aim of the present study was to investigate the effect of lipopolysaccharide (LPS) on the synthesis of t-PA and PAI-2 by human gingival fibroblasts (HGF) . LPS from different periodontal pathogens including Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis and Fusobacterium nucleatum were extracted by the hot phenol water method . The levels of t-PA and PAI-2 secreted into the cell culture media were measured by enzyme-linked immunosorbent assays (ELISA) . The mRNA for t-PA and PAI-2 were measured by RT-PCR . The results showed t-PA synthesis was increased in response to all types of LPS studied and PAI-2 level was increased by LPS from A . actinomycetemcomitans and F . nucleatum, but not P . gingivalis . When comparing the effects of LPS from non-periodontal bacteria (Escherichia coli and Salmonella enteritidis) with the LPS from periodontal pathogens, we found that the ratio of t-PA to PAI-2 was greater following exposure of the cells to LPS from periodontal pathogens . The highest ratio of t-PA to PAI-2 was found in those cells exposed to LPS from P . gingivalis . These results indicate that LPS derived from periodontal pathogens may cause unbalanced regulation of plasminogen activator and plasminogen activator inhibitor by HGF and such an effect may, in part, contribute to the destruction of periodontal connective tissue through dysregulated pericellular proteolysis.

J Vet Med B Infect Dis Vet Public Health, 2000 Nov, 47(9), 707 - 19
Studies of the phenomenon of host adaptation in Salmonella; Steinbach G et al.; To study the phenomenon of host adaptation in Salmonella, a mathematical model has been developed which permits a definition and experimental investigation of the specific interaction between the adapted serovar and the adequate host . After experimental infection using a mixture of equal parts of two Salmonella strains, A and B, the bacterial concentrations CA and CB were determined in the organs of the animals infected . If an animal of species a and an animal of species b are infected with the same mixture of strain A adapted to a and strain B adapted to b, an expression: log10Qab = log10CaA + log10CbB - log10CaB - log10CbA may be calculated which describes the influence of the specific serovar-host interaction on the dynamics of the bacterial count . The variable Qab was determined using four Salmonella dublin, four Salmonella choleraesuis and five Salmonella gallinarum/pullorum strains in a total of 63 pairs of different hosts (calf and pig, calf and chicken, or pig and chicken) . On this basis, the following statements can be made . The epidemiologically defined host adaptation of Salmonellas is accompanied by a specific agent-host interaction between the adapted serovar and adequate host . It promotes adherence and spreading of the agent in the adequate host . The effect was particularly expressed on day 3 post-infection and could be detected both in the lumen of the anterior sections of the intestine and in the intestinal lymph nodes and the liver . In part, the host-independent strain characteristics had a greater influence than the specific serovar-host interaction on the dynamics of the bacterial count . Strains of non-adapted serovars may thus result in a more intense colonization and invasion of the host than simultaneously administered bacteria of a serovar which is adapted to the respective host . The effects of a specific serovar-host interaction on colonization of and spreading in the host should be considered only as a component which contributes to the phenomenon of host adaptation.

J Mol Evol, 2001 Feb, 52(2), 193 - 204
The interaction of protein structure, selection, and recombination on the evolution of the type-1 fimbrial major subunit (fimA) from Escherichia coli; Peek AS et al.; Fimbrial adhesins allow bacteria to interact with and attach to their environment . The bacteria possibly benefit from these interactions, but all external structures including adhesins also allow bacteria to be identified by other organisms . Thus adhesion molecules might be under multiple forms of selection including selection to constrain functional interactions or evolve novel epitopes to avoid recognition . We address these issues by studying genetic diversity in the Escherichia coli type-1 fimbrial major subunit, fimA . Overall, sequence diversity in fimA is high (pi = 0.07) relative to that in other E . coli genes . High diversity is a function of positive diversifying selection, as detected by d(N)/d(S) ratios higher than 1.0, and amino acid residuces subject to diversifying selection are nonrandomly clustered on the exterior surface of the peptide . In addition, McDonald and Kreitman tests suggest that there has been historical but not current directional selection at fimA between E . coli and Salmonella . Finally, some regions of the fimA peptide appear to be under strong structural constraint within E . coli, particularly the interior regions of the molecule that is involved in subunit to subunit interaction . Recombination also plays a major role contributing to E . coli fimA allelic variation and estimates of recombination (2N(e)c) and mutation (2N(e)mu) are about the same . Recombination may act to separate the diverse evolutionary forces in different regions of the fimA peptide.

J Interferon Cytokine Res, 2001 Feb, 21(2), 85 - 92
Modulation of functional activities of chicken heterophils by recombinant chicken IFN-gamma; Kogut MH et al.; The objective of the present studies was to examine the in vitro effects of recombinant chicken interferon-gamma (rChIFN-gamma) on shape change, phagocytosis, and the oxidative/nonoxidative killing activities of day-old chicken heterophils . Heterophils (4 x 10(6)/ml) were incubated with various concentrations of recombinant ChIFN-gamma from both Escherichia coli and transfected Cos cells for 2 h at 39 degrees C . The incubation of the neonatal heterophils with rChIFN-gamma resulted in significantly greater numbers of cells with membrane shape change when compared with the mock-treated heterophils . Both Cos cell-derived and E . coli-derived ChIFN-gamma significantly increased (p < 0.01) the phagocytosis of opsonized or nonopsonized Salmonella enteritidis by the neonatal heterophils in a concentration-dependent manner . Incubation with ChIFN-gamma induced no direct stimulation of the respiratory burst by the chicken heterophils but did prime the heterophils for a significantly strengthened respiratory burst to subsequent stimulation with opsonized zymosan (OZ) . Lastly, incubation of the heterophils with ChIFN-gamma primed the cells for a significant increase in the release of beta-D-glucuronidase following stimulation with OZ . These results show that neonatal avian heterophils can respond to cytokine modulation with enhanced functional competence, suggesting that ChIFN-gamma can enhance the immune competence of the innate defenses of chickens during the first week of life.

J Bacteriol, 2001 Apr, 183(7), 2348 - 58
Salmonella host cell invasion emerged by acquisition of a mosaic of separate genetic elements, including Salmonella pathogenicity island 1 (SPI1), SPI5, and sopE2; Mirold S et al.; Salmonella spp . possess a conserved type III secretion system encoded within the pathogenicity island 1 (SPI1; centisome 63), which mediates translocation of effector proteins into the host cell cytosol to trigger responses such as bacterial internalization . Several translocated effector proteins are encoded in other regions of the Salmonella chromosome . It remains unclear how this complex chromosomal arrangement of genes for the type III apparatus and the effector proteins emerged and how the different effector proteins cooperate to mediate virulence . By Southern blotting, PCR, and phylogenetic analyses of highly diverse Salmonella spp., we show here that effector protein genes located in the core of SPI1 are present in all Salmonella lineages . Surprisingly, the same holds true for several effector protein genes located in distant regions of the Salmonella chromosome, namely, sopB (SPI5, centisome 20), sopD (centisome 64), and sopE2 (centisomes 40 to 42) . Our data demonstrate that sopB, sopD, and sopE2, along with SPI1, were already present in the last common ancestor of all contemporary Salmonella spp . Analysis of Salmonella mutants revealed that host cell invasion is mediated by SopB, SopE2, and, in the case of Salmonella enterica serovar Typhimurium SL1344, by SopE: a sopB sopE sopE2-deficient triple mutant was incapable of inducing membrane ruffling and was >100-fold attenuated in host cell invasion . We conclude that host cell invasion emerged early during evolution by acquisition of a mosaic of genetic elements (SPI1 itself, SPI5 {sopB}, and sopE2) and that the last common ancestor of all contemporary Salmonella spp . was probably already invasive.

J Bacteriol, 2001 Apr, 183(7), 2234 - 40
Altered pathway routing in a class of Salmonella enterica serovar Typhimurium mutants defective in aminoimidazole ribonucleotide synthetase; Zilles JL et al.; In Salmonella enterica serovar Typhimurium, purine nucleotides and thiamine are synthesized by a branched pathway . The last known common intermediate, aminoimidazole ribonucleotide (AIR), is formed from formylglycinamidine ribonucleotide (FGAM) and ATP by AIR synthetase, encoded by the purI gene in S . enterica . Reduced flux through the first five steps of de novo purine synthesis results in a requirement for purines but not necessarily thiamine . To examine the relationship between the purine and thiamine biosynthetic pathways, purI mutants were made (J . L . Zilles and D . M . Downs, Genetics 143:37-44, 1996) . Unexpectedly, some mutant purI alleles (R35C/E57G and K31N/A50G/L218R) allowed growth on minimal medium but resulted in thiamine auxotrophy when exogenous purines were supplied . To explain the biochemical basis for this phenotype, the R35C/E57G mutant PurI protein was purified and characterized kinetically . The K(m) of the mutant enzyme for FGAM was unchanged relative to the wild-type enzyme, but the V(max) was decreased 2.5-fold . The K(m) for ATP of the mutant enzyme was 13-fold increased . Genetic analysis determined that reduced flux through the purine pathway prevented PurI activity in the mutant strain, and purR null mutations suppressed this defect . The data are consistent with the hypothesis that an increased FGAM concentration has the ability to compensate for the lower affinity of the mutant PurI protein for ATP.

J Bacteriol, 2001 Apr, 183(7), 2178 - 86
Global analysis of Escherichia coli gene expression during the acetate-induced acid tolerance response; Arnold CN et al.; The ability of Escherichia coli to survive at low pH is strongly affected by environmental factors, such as composition of the growth medium and growth phase . Exposure to short-chain fatty acids, such as acetate, proprionate, and butyrate, at neutral or nearly neutral pH has also been shown to increase acid survival of E . coli and Salmonella enterica serovar Typhimurium . To investigate the basis for acetate-induced acid tolerance in E . coli O157:H7, genes whose expression was altered by exposure to acetate were identified using gene arrays . The expression of 60 genes was reduced by at least twofold; of these, 48 encode components of the transcription-translation machinery . Expression of 26 genes increased twofold or greater following treatment with acetate . This included six genes whose products are known to be important for survival at low pH . Five of these genes, as well as six other acetate-induced genes, are members of the E . coli RpoS regulon . RpoS, the stress sigma factor, is known to be required for acid tolerance induced by growth at nonlethal low pH or by entry into stationary phase . Disruption of the rpoS gene by a transposon insertion mutation also prevented acetate-induced acid tolerance . However, induction of RpoS expression did not appear to be sufficient to activate the acid tolerance response . Treatment with either NaCl or sodium acetate (pH 7.0) increased expression of an rpoS::lacZ fusion protein, but only treatment with acetate increased acid survival.

J Mol Biol, 2001 Mar 16, 307(1), 283 - 95
The crystal structure of dTDP-D-Glucose 4,6-dehydratase (RmlB) from Salmonella enterica serovar Typhimurium, the second enzyme in the dTDP-l-rhamnose pathway; Allard ST et al.; l-Rhamnose is a 6-deoxyhexose that is found in a variety of different glycoconjugates in the cell walls of pathogenic bacteria . The precursor of l-rhamnose is dTDP-l-rhamnose, which is synthesised from glucose- 1-phosphate and deoxythymidine triphosphate (dTTP) via a pathway requiring four enzymes . Significantly this pathway does not exist in humans and all four enzymes therefore represent potential therapeutic targets . dTDP-D-glucose 4,6-dehydratase (RmlB; EC 4.2.1.46) is the second enzyme in the dTDP-L-rhamnose biosynthetic pathway . The structure of Salmonella enterica serovar Typhimurium RmlB had been determined to 2.47 A resolution with its cofactor NAD(+) bound . The structure has been refined to a crystallographic R-factor of 20.4 % and an R-free value of 24.9 % with good stereochemistry.RmlB functions as a homodimer with monomer association occurring principally through hydrophobic interactions via a four-helix bundle . Each monomer exhibits an alpha/beta structure that can be divided into two domains . The larger N-terminal domain binds the nucleotide cofactor NAD(+) and consists of a seven-stranded beta-sheet surrounded by alpha-helices . The smaller C-terminal domain is responsible for binding the sugar substrate dTDP-d-glucose and contains four beta-strands and six alpha-helices . The two domains meet to form a cavity in the enzyme . The highly conserved active site Tyr(167)XXXLys(171) catalytic couple and the GlyXGlyXXGly motif at the N terminus characterise RmlB as a member of the short-chain dehydrogenase/reductase extended family.The quaternary structure of RmlB and its similarity to a number of other closely related short-chain dehydrogenase/reductase enzymes have enabled us to propose a mechanism of catalysis for this important enzyme .

Vet J, 2001 Mar, 161(2), 132 - 64
Salmonella: immune responses and vaccines; Mastroeni P et al.; Salmonella infections are a serious medical and veterinary problem world-wide and cause concern in the food industry . Vaccination is an effective tool for the prevention of Salmonella infections . Host resistance to Salmonella relies initially on the production of inflammatory cytokines leading to the infiltration of activated inflammatory cells in the tissues . Thereafter T- and B-cell dependent specific immunity develops allowing the clearance of Salmonella microorganisms from the tissues and the establishment of long-lasting acquired immunity to re-infection . The increased resistance that develops after primary infection/ vaccination requires T-cells cytokines such as IFNgamma TNFalpha and IL12 in addition to opsonising antibody . However for reasons that are not fully understood seroconversion and/or the presence of detectable T-cell memory do not always correlate with the development of acquired resistance to infection.Whole-cell killed vaccines and subunit vaccines are used in the prevention of Salmonella infection in animals and in humans with variable results . A number of early live Salmonella vaccines derived empirically by chemical or u.v . mutagenesis proved to be immunogenic and protective and are still in use despite the need for repeated parenteral administration . Recent progress in the knowledge of the genetics of Salmonella virulence and modern recombinant DNA technology offers the possibility to introduce multiple defined attenuating and irreversible mutations into the bacterial genome . This has recently allowed the development of Salmonella strains devoid of significant side effects but still capable of inducing solid immunity after single oral administration . Live attenuated Salmonella vaccines have been used for the expression of heterologous antigens/proteins that can be successfully delivered to the immune system . Furthermore Salmonella can transfer plasmids encoding foreign antigens under the control of eukaryotic promoters (DNA vaccines) to antigen-presenting cells resulting in targeted delivery of DNA vaccines to these cells . Despite the great recent advances in the development of Salmonella vaccines a large proportion of the work has been conducted in laboratory rodents and more research in other animal species is required .

Arkh Patol, 2001 Jan-Feb, 63(1), 15 - 8
{Characteristic of proliferative processes in colonic mucosa in acute salmonellosis}; Mokretsova EV et al.; DNA synthesis in the epithelium of a distal portion of human colon was studied at radioautography with 3H-thymidine through the first three days of gastrointestinal salmonellesis . Control studies were performed on the mucosa of the sigmoid colon of healthy persons undergoing rectoromanoscopy because of epidemiological reasons . No pathological changes were found in these specimens, the labeled nuclei index (LNI) was 5.16 +/- 0.27%, the label intensity (LI) which characterizes the rate of DNA synthesis was 13.65 +/- 0.82 . Group 1 consisted of 18 patients having slight inflammation without erosions, ulcerative and haemorrhagic changes . We found significant activation of proliferation (LNI = 15.09 +/- 0.9%, LI = 22.23 +/- 1.9; p < 0.05) in this group compared to the control one . 15 patients with salmonella-induced hemorrhagic colitis formed group 2 in which LNI and LI were also increased (LNI = 9.89 +/- 1.0%, LI = 19.3 +/- 2.3; p < 0.02) vs . control group, but these changes seemed to be significantly weaker than those in group 1 (p < 0.01) . It is inferred that rates of proliferation in colon epithelium in acute salmonellosis are significantly higher than in healthy epithelium but activity of these processes decreases with growing severity of inflammation.

Microbiol Mol Biol Rev, 2001 Mar, 65(1), 119 - 30
Escherichia coli and Salmonella 2000: the view from here; Schaechter M; View From Here Group; Five years after the publication of the second edition of the reference book Escherichia coli and Salmonella: Cellular and Molecular Biology, and on the eve of launching a successor venture, the editors and colleagues examine where we stand in our quest for an understanding of these organisms . The main areas selected for this brief inquiry are genomics, evolution, molecular multifunctionality, functional backups, regulation of gene expression, cell biology, sensing of the environment, and ecology.

Microbiology, 2001 Mar, 147(Pt 3), 599 - 610
Molecular evolution of the GDP-mannose pathway genes (manB and manC) in Salmonella enterica; Jensen SO et al.; The evolutionary history of the GDP-mannose pathway in Salmonella enterica was studied via sequencing manB and manC genes from 13 representative strains for O antigens containing mannose and/or sugar derivatives of GDP-D-mannose . In addition, colanic acid (CA) manB and manC genes were sequenced from selected strains, as the basis for a detailed comparison . Interestingly, including the eight previously characterized O antigen gene clusters, 12 of the 21 S . enterica strains studied in total (each representing a different O antigen structure) possess a manB gene which displays DNA identity, ranging from 93 to 99%, to the CA manB gene of S . enterica LT2 . Furthermore, the CA-like manB genes (as well as the CA manB and manC genes) display subspecies specificity, and the CA and CA-like manB genes (for individual strains) appear to be evolving in concert via gene conversion events . In comparison, the manC genes were generally not CA-like, a situation also apparent in Escherichia coli,and therefore most strongly reflected the evolutionary history of the S . enterica O antigen GDP-mannose pathway . It appears that, in relatively recent times, gene capture from a distant source has occurred infrequently, and that groups of manB and manC genes have been maintained and are continuing to evolve within S . enterica and more closely related species.

J Infect Dis, 2001 Apr 1, 183(7), 1156 - 60 Epub 2001 Mar 01.
Typhoid fever and genetic polymorphisms at the natural resistance-associated macrophage protein 1; Dunstan SJ et al.; Control of Salmonella enterica serovar Typhimurium (S . typhimurium) infection in the mouse model of typhoid fever is critically dependent on the natural resistance-associated macrophage protein 1 (Nramp1) . In this study, we examined the role of genetic polymorphisms in the human homologue, NRAMP1, in resistance to typhoid fever in southern Vietnam . Patients with blood-culture-confirmed typhoid fever and healthy control subjects were genotyped for 6 polymorphic markers within and near NRAMP1 on chromosome 2q35 . Four single base-pair polymorphisms (274 C/T, 469+14 G/C, 1465-85 G/A, and D543N), a (GT)(n) repeat in the promoter region of NRAMP1 and D2S1471, and a microsatellite marker approximately 130-kb downstream of NRAMP1 were examined . The allelic and genotypic frequencies for each polymorphism were compared in case patients and control subjects . No allelic association was identified between the NRAMP1 alleles and typhoid fever susceptibility . In addition, neither homozygotes nor heterozygotes for any NRAMP1 variants were at increased risk of typhoid fever.

J Infect Dis, 2001 Mar 15, 183(6), 984 - 7 Epub 2001 Feb 21.
An outbreak of Salmonella serotype Thompson associated with fresh cilantro; Campbell JV et al.; An outbreak of Salmonella serotype Thompson in California was identified through laboratory-based surveillance and investigated with case-control, traceback, and laboratory studies . There were 35 "sporadic" cases and a restaurant-associated outbreak of 41 cases with onset between 6 March and 31 March 1999 . Three case patients were hospitalized . A case-control study found a significant association between illness and eating cilantro at a restaurant (63% of case patients vs . 34% of control subjects; odds ratio, 3.5; 95% confidence interval, 1.1-11.4) . Although common distributors of cilantro were identified, inadequate records prohibited the identification of a single farm supplying cilantro . At room temperature, Salmonella Thompson grew more rapidly and to a higher concentration on chopped cilantro, compared with whole-leaf cilantro . Freshly made salsa (pH 3.4) supported growth of Salmonella Thompson . Cilantro should be served promptly after chopping . Accurate records of the distribution of produce should be available, and bacterial contamination of produce should be prevented in retail and wholesale establishments, in packing sheds, and on farms.

J AOAC Int, 2001 Jan-Feb, 84(1), 65 - 83
Rappaport-Vassiliadis medium for recovery of Salmonella spp . from low microbial load foods: collaborative study; Hammack TS et al.; Twenty-three laboratories participated in a collaborative study to compare the relative effectiveness of Rappaport-Vassiliadis (RV) medium incubated at 42 degrees C, selenite cystine (SC) broth (35 degrees C), and tetrathionate (TT) broth (35 and 43 degrees C) for recovery of Salmonella from the following foods with a low microbial load: dried egg yolk, dry active yeast, ground black pepper, guar gum, and instant nonfat dry milk . For dry active yeast, lauryl tryptose (LT) broth, incubated at 35 degrees C, was used instead of SC broth . All of the foods were artificially inoculated with single Salmonella serovars, that had been lyophilized before inoculation, at high and low target levels of 0.4 and 0.04 colony forming units/g food, respectively . For analysis of 870 test portions, representing all of the foods except yeast, 249 Salmonella-positive test portions were detected by RV medium, 265 by TT broth (43 degrees C), 268 by TT broth (35 degrees C), and 269 by SC broth (35 degrees C) . For analysis of 225 test portions of yeast, 79 Salmonella-positive test portions were detected by RV medium, 79 by TT broth (43 degrees C), 84 by TT broth (35 degrees C), and 68 by LT broth (35 degrees C) . RV medium was comparable to, or even more effective than, the other selective enrichments for recovery of Salmonella from all of the foods except guar gum . It is recommended that RV (42 degrees C) and TT (35 degrees C) be used with foods that have a low microbial load, except for guar gum for which SC (35 degrees C) and TT (35 degrees C) are recommended.

Acta Med Port, 2000 Sep-Dec, 13(5-6), 325 - 8
{Pleural effusion infected with Salmonella enteridis}; Vanzeller M et al.; The authors describe the case of a 49 year-old caucasian male with left pleural effusion . The etiology of the effusion was exsudative with a preponderance of neutrophils . Ten days after admission and on empirical antibiotic therapy, the patient still had fever and the pleural effusion that became purulent . The thoracic echography and computerized tomography showed a subcapsular splenic abcess . The diagnosis was established by the culture of the pleural effusion and the isolation of Salmonella enteritidis enteritidis serotype . According to the antibiogram, a treatment with cotrimoxazole was established with clinical improvement . A splenectomy was performed.

Transplantation, 2001 Feb 15, 71(3), 479 - 81
Non-typhoid Salmonella septicemia and visceral leishmaniasis in a renal transplant patient; Hussein MM et al.; BACKGROUND: We report on a renal transplant patient with recurrent attacks of fever, in which Salmonella septicemia as well as visceral leishmaniasis were diagnosed . PATIENT: The patient was a 62-year-old man with diabetic nephropathy and a living related kidney transplantation . RESULTS: Nearly 2 years after the transplantation, the patient developed recurrent attacks of fever, which were initially diagnosed as non-typhoid salmonellosis and improved after treatment . Three months later, he had relapses of fever . As the patient developed pancytopenia, a bone marrow aspiration was done, showing Leishmania parasites . The patient responded well to treatment with sodium stibogluconate . CONCLUSIONS: A high index of suspicion, together with better diagnostic assays to detect visceral leishmaniasis, is warranted in the diagnostic work-up of any fever of unknown origin in immunocompromised patients, especially in endemic areas.

Acta Microbiol Immunol Hung, 2001, 48(1), 95 - 105
The spread and antibiotic resistance of Salmonella enterica serotype typhimurium DT104 in Hungary; Paszti J et al.; Comparison of phage types (PTs) determined by Felix and Callow's and Anderson's methods was performed testing 99 human strains of S . enterica serotype Typhimurium (S . typhimurium) isolated in Hungary . PT2 and PT2c--according to Felix-Callow--corresponded with Anderson's DT104 in case of 39 strains out of 40 . Among 59 isolates belonging to other Felix-Callow's PTs only one strain was found which was DT 104 . Similar unambiguous equalities could not be established between any other PTs comparing the two methods . The PTs of 17,877 human strains isolated between 1988 and 1999 were determined using Felix-Callow's method . On the basis of the above equality the emergence of DT104 could be followed retrospectively by means of the rate of PT2 and PT2c . The increase of DT104 began already in 1989, emerging first PT2c then PT2 . It predominated since 1991 and it reached its maximum (78.3%) in 1999 . The incidence of multiresistance among one of the groups of DT104 strains (Felix-Callow's PT2) was significantly higher in 1998 than the average of non-DT104 strains . The predominant R-type was ACST.

Biotechniques, 2001 Feb, 30(2), 304 - 6, 308-11
Inside or outside: detecting the cellular location of bacterial pathogens; Edwards RA et al.; Salmonella are intracellular pathogens that infect and multiply inside macrophages . Although Salmonella are some of the best-studied pathogens, it is difficult to determine quickly and reliably whether the bacteria are intracellular or extracellular . We have developed a novel method using differential fluorescence of two fluorescent proteins to determine the cellular location of pathogenic bacteria in macrophage infection assays . Using the differential expression of two unique fluorescent proteins that are expressed under specific conditions, we have developed a real-time assay for macrophage infections . The critical advantages of this system are that it does not alter the bacterial surface, it is not toxic to either the bacteria or the host cell, and it may be used in real-time quantitative assays . This assay can be readily applied to any other model pathogenic systems such as Listeria, Mycobacteria, and Legionella in which intracellular gene expression has been characterized.

Klin Lab Diagn, 2001 Jan, (1), 52 - 4
{Serodiagnosis in salmonelloses}; Zolotarev IuV et al.; A method for preparing antigenic hydrosol diagnostic agent for hydrosol agglutination test is suggested . Efficiencies of hydrosol agglutination and passive hemagglutination tests in detection of antibodies to salmonella are compared . Arbitrary diagnostic titers are determined, diagnostic value of hydrosol agglutination test is assessed, time course of accumulation of specific antibodies is traced, and optimal terms of serological diagnosis of salmonellosis in patients of different age are determined.

Int J Infect Dis, 2000, 4(4), 194 - 7
Multidrug-resistant strains of Salmonella enterica serotype typhi are genetically homogenous and coexist with antibiotic-sensitive strains as distinct, independent clones; Thong KL et al.; OBJECTIVE: The goal of this study was to report the molecular analysis of antibiotic-sensitive and multidrug-resistant (MDR) strains of Salmonella typhi, using pulsed-field gel electrophoresis (PFGE), with a particular emphasis on the coexistence of these strains in a typhoid-endemic region of Karachi, Pakistan . METHODS: One hundred isolates of S . typhi in humans (50 MDR and 50 antibiotic-sensitive isolates) from sporadic cases of typhoid fever were analyzed by Vi-phage typing, antibiograms and PFGE . RESULTS: The MDR S . typhi strains were resistant to ampicillin, chloramphenicol, and trimethoprim-sulfamethoxazole . Analysis by PFGE showed that 50 MDR isolates of S . typhi had a single, homogenous PFGE profile, which was distinctly different from that of 50 antibiotic-sensitive isolates obtained in the same time frame from the same area . This latter group of isolates showed much greater diversity of PFGE profiles, as has been observed in other endemic regions . CONCLUSIONS: Multidrug-resistant and antibiotic-susceptible strains of S . typhi can coexist in endemic areas as epidemiologically independent pathogens and are not in competition for continued persistence and transmission.

Mutagenesis, 2001 Mar, 16(2), 169 - 77
The preparation of anthraquinone used in the National Toxicology Program cancer bioassay was contaminated with the mutagen 9-nitroanthracene; Butterworth BE et al.; Commercial anthraquinone (AQ) (9,10-anthracenedione) is produced by at least three different production methods worldwide: oxidation of anthracene (AQ-OX), Friedel-Crafts technology (AQ-FC) and by Diels-Alder chemistry (AQ-DA), with the final product varying in color and purity . AQ-OX begins with anthracene produced from coal tar and different lots can contain various contaminants, particularly the mutagenic isomers of nitroanthracene . AQ has been reported to be negative in a variety of genotoxicity tests including numerous Ames Salmonella mutagenicity assays . In addition, we report that AQ-DA is negative in the Salmonella-Escherichia coli reverse mutation assays, the L5178Y mouse lymphoma forward mutation assay, for inducing chromosomal aberrations, polyploidy or endoreduplication in Chinese hamster ovary cells, and in the in vivo mouse micronucleus assay . Further, a previous 18 month bioassay conducted with AQ administered to male and female B6C3F(1) and (C57BL/6xAKR)F(1) mice reported no induction of cancer . Thus, it was somewhat unexpected that in a long-term study conducted by the National Toxicology Program (NTP) AQ-OX induced a weak to modest increase in tumors in the kidney and bladder of male and female F344/N rats and a strong increase in the livers of male and female B6C3F(1) mice . In the studies reported here, a sample of the AQ-OX used in the NTP bioassay was shown to be mutagenic in the Ames tester strains TA98, TA100 and TA1537 . Addition of an S9 metabolic activation system decreased or eliminated the mutagenic activity . In contrast, the purified NTP AQ-OX as well as the technical grade samples AQ-FC and AQ-DA were not mutagenic in the Ames test . The chemical structure of AQ does not suggest that the parent compound would be DNA reactive . Therefore, a mutagenic contaminant was present in the NTP bioassay sample that is either directly mutagenic or can be activated by bacterial metabolism . Analytical studies showed that the primary contaminant 9-nitroanthracene (9-NA) was present in the NTP AQ-OX at a concentration of 1200 p.p.m., but not in the purified material . The 9-NA and any other contaminants that might have been present in the NTP AQ-OX induced measurable mutagenicity at 9-NA concentrations as low as 0.15 microg/plate in tester strain TA98, indicating potent mutagenic activity . On the basis of revertants per microgram, 9-NA was more potent than benzo{a}pyrene (B{a}P) and was about equally as potent as the 2-nitrofluorene run concurrently as positive controls . TD(50) quantitative carcinogenicity potency estimates indicate that a carcinogen of a potency in the range between B{a}P and dimethylnitrosamine would be required to produce the observed carcinogenic response at the levels of the contaminants found in the test sample . While recognizing that there are limitations in extrapolating mutagenic potency to potential carcinogenic potency, these estimates do indicate that it is plausible that the 9-NA contaminant might have been responsible for all of the tumor induction observed in the NTP study . In fact, in the absence of reliable cancer data, the genetic toxicology profile indicates that AQ would not be a genotoxic carcinogen . Thus, no conclusion as to the carcinogenic activity of AQ can be made at this time.

Mol Biol Evol, 2001 Mar, 18(3), 404 - 12
Codon bias and base composition are poor indicators of horizontally transferred genes; Koski LB et al.; Horizontal gene transfer is now recognized as an important mechanism of evolution . Several methods to detect horizontally transferred genes have been suggested . These methods are based on either nucleotide composition or the failure to find a similar gene in closely related species . Genes that evolve vertically between closely related species can be divided into those that retain homologous chromosomal positions (positional orthologs) and those that do not . By comparing open reading frames in the Escherichia coli and Salmonella typhi genomes, we identified 2,728 positional orthologs since these species split 100 MYA . A group of 1,144 novel E . coli genes were unusually diverged from their S . typhi counterparts . These novel genes included those that had been horizontally transferred into E . coli, as well as members of gene pairs that had been rearranged or deleted . Positional orthologs were used to investigate compositional methods of identifying horizontally transferred genes . A large number of E . coli genes with normal nucleotide composition have no apparent ortholog in S . typhi, and many genes of atypical composition do, in fact, have positional orthologs . A phylogenetic approach was employed to confirm selected examples of horizontal transmission among the novel groups of genes . Our analysis of 80 E . coli genes determined that a number of genes previously classified as horizontally transferred based on base composition and codon bias were native, and genes previously classified as native appeared to be horizontally transferred . Hence, atypical nucleotide composition alone is not a reliable indicator of horizontal transmission.

J Clin Microbiol, 2001 Mar, 39(3), 1057 - 66
Molecular typing and epidemiological study of Salmonella enterica serotype Typhimurium isolates from cattle by fluorescent amplified-fragment length polymorphism fingerprinting and pulsed-field gel electrophoresis; Tamada Y et al.; One hundred twenty Salmonella enterica serotype Typhimurium strains, including 103 isolates from cattle gathered between 1977 and 1999 in the prefecture located on the northern-most island of Japan, were analyzed by using fluorescent amplified-fragment length polymorphism (FAFLP) and pulsed-field gel electrophoresis (PFGE) to examine the genotypic basis of the epidemic . Among these strains, there were 17 FAFLP profiles that formed four distinct clusters (A, B, C, and D) . Isolates that belonged to cluster A have become increasingly common since 1992 with the increase of bovine salmonellosis caused by serotype Typhimurium . PFGE resolved 25 banding patterns that formed three distinct clusters (I, II, and III) . All the isolates that belonged to FAFLP cluster A, in which all the strains of definitive phage type 104 examined were included, were grouped into PFGE cluster I . Taken together, these results indicate that clonal exchange of serotype Typhimurium has taken place since 1992, and they show a remarkable degree of homogeneity at a molecular level among contemporary isolates from cattle in this region . Moreover, we have sequenced two kinds of FAFLP markers, 142-bp and 132-bp fragments, which were identified as a polymorphic marker of strains that belonged to clusters A and C, respectively . The sequence of the 142-bp fragment shows homology with a segment of P22 phage, and that of the 132-bp fragment shows homology with a segment of traG, which is an F plasmid conjugation gene . FAFLP is apparently as well suited for epidemiological typing of serotype Typhimurium as is PFGE, and FAFLP can provide a source of molecular markers useful for studies of genetic variation in natural populations of serotype Typhimurium.

J Clin Microbiol, 2001 Mar, 39(3), 1002 - 7
Serology of typhoid fever in an area of endemicity and its relevance to diagnosis; House D et al.; Currently, the laboratory diagnosis of typhoid fever is dependent upon either the isolation of Salmonella enterica subsp . enterica serotype Typhi from a clinical sample or the detection of raised titers of agglutinating serum antibodies against the lipopolysaccharide (LPS) (O) or flagellum (H) antigens of serotype Typhi (the Widal test) . In this study, the serum antibody responses to the LPS and flagellum antigens of serotype Typhi were investigated with individuals from a region of Vietnam in which typhoid is endemic, and their usefulness for the diagnosis of typhoid fever was evaluated . The antibody responses to both antigens were highly variable among individuals infected with serotype Typhi, and elevated antibody titers were also detected in a high proportion of serum samples from healthy subjects from the community . In-house enzyme-linked immunosorbent assays (ELISAs) for the detection of specific classes of anti-LPS and antiflagellum antibodies were compared with other serologically based tests for the diagnosis of typhoid fever (Widal TO and TH, anti-serotype Typhi immunoglobulin M {IgM} dipstick, and IDeaL TUBEX) . At a specificity of > or =0.93, the sensitivities of the different tests were 0.75, 0.55, and 0.52 for the anti-LPS IgM, IgG, and IgA ELISAs, respectively; 0.28 for the antiflagellum IgG ELISA; 0.47 and 0.32 for the Widal TO and TH tests, respectively; and 0.77 for the anti-serotype Typhi IgM dipstick assay . The specificity of the IDeaL TUBEX was below 0.90 (sensitivity, 0.87; specificity, 0.76) . The serological assays based on the detection of IgM antibodies against either serotype Typhi LPS (ELISA) or whole bacteria (dipstick) had a significantly higher sensitivity than the Widal TO test when used with a single acute-phase serum sample (P < or = 0.007) . These tests could be of use for the diagnosis of typhoid fever in patients who have clinical typhoid fever but are culture negative or in regions where bacterial culturing facilities are not available.

Appl Environ Microbiol, 2001 Mar, 67(3), 1190 - 7
Multiple antibiotic resistance (mar) locus in Salmonella enterica serovar typhimurium DT104; Randall LP et al.; In order to understand the role of the mar locus in Salmonella with regard to multiple antibiotic resistance, cyclohexane resistance, and outer membrane protein F (OmpF) regulation, a marA::gfp reporter mutant was constructed in an antibiotic-sensitive Salmonella enterica serovar Typhimurium DT104 background . Salicylate induced marA, whereas a number of antibiotics, disinfectants, and various growth conditions did not . Increased antibiotic resistance was observed upon salicylate induction, although this was shown to be by both mar-dependent and mar-independent pathways . Cyclohexane resistance, however, was induced by salicylate by a mar-dependent pathway . Complementation studies with a plasmid that constitutively expressed marA confirmed the involvement of mar in Salmonella with low-level antibiotic resistance and cyclohexane resistance, although the involvement of mar in down regulation of OmpF was unclear . However, marA overexpression did increase the expression of a ca . 50-kDa protein, but its identity remains to be elucidated . Passage of the marA::gfp reporter mutant with increasing levels of tetracycline, a method reported to select for mar mutants in Escherichia coli, led to both multiple-antibiotic and cyclohexane resistance . Collectively, these data indicate that low-level antibiotic resistance, cyclohexane resistance, and modulation of OMPs in Salmonella, as in E . coli, can occur in both a mar-dependent and mar-independent manner.

Microbios, 2001, 104(407), 39 - 47
Molecular characterization of Salmonella weltevreden isolated from poultry: evidence of conjugal transfer of plasmid and antibiotic resistance; Radu S et al.; Ten strains of Salmonella weltevreden isolated from poultry sources were examined and found to contain plasmid DNA ranging in size from 1.8 to 68.5 MD . All isolates were susceptible to carbenicillin, cephalothin, ceftriazone, gentamicin, kanamycin and nalidixic acid, but resistance to bacitracin (100%), penicillin G (100%), rifampicin (100%), sulphamethoxazole (100%), cefuroxime (80%) and tetracycline (60%) was recorded . The 55 MD plasmid of strain SW5 determined resistance to penicillin G and tetracycline, which was transmissible to the E . coli K12 recipient at a frequency of 3.52 x 10(-5) transconjugants per input donor cell . The results of arbitrarily primed polymerase chain reaction (AP-PCR), using two 10-mer oligonucleotides and PCR-ribotyping to differentiate between the ten strains of S . weltevreden were compared . The strains were separated into ten different genome types by AP-PCR but were indistinguishable by PCR-ribotyping . These results suggest that poultry may constitute a reservoir for disseminating antibiotic resistance and that AP-PCR may be a valuable tool for epidemiological studies.

Indian J Med Sci, 2000 Mar, 54(3), 102 - 5
Antibacterial effect of some leaf extracts on Salmonella typhi; Gehlot D et al.; Aqueous and methanol extracts of fresh leaves of twenty desert plants of Rajasthan state were tested for their antibacterial activity against human pathogenic bacteria Salmonella typhi, causal organism of typhoid fever in human beings . 10% concentrate extracts of leaves of various plant species were used for testing antibacterial potential . Five plant species were found to have inhibitory effect against the organism . Fagonia cretica leaf extracts were found most effective against Salmonella typhi.

Can J Vet Res, 2001 Jan, 65(1), 15 - 21
Testing of bulk tank milk for Salmonella Dublin infection in Danish dairy herds; Wedderkopp A et al.; The usefulness of enzyme-linked immunosorbent assay (ELISA) was investigated as a simple method to screen for Salmonella Dublin infection in dairy herds, examining bulk tank milk samples for lipopolysaccharide (O:1,9,12) antibodies . The cut-off value for the ELISA on bulk tank milk was established based on individual milk samples (n = 2887) and bulk tank milk from 52 herds . Bulk tank milk samples (n = 5108) were collected from 1464 dairy herds located in 19 different areas . About 10% of the dairy herds in Denmark participated in the study . The percentage of herds changing from test-negative to test-positive in each area was correlated with the incidence of S . Dublin outbreaks in the corresponding county (r = 0.48, n = 19; P < 0.025) . The mean level of the OD values obtained in the first and third test rounds was not constant (Pr /t/ = 0.0001) . The study demonstrated that the probability of being test-negative in the third test round was 0.926 for a herd with 2 previous test-negative results . It was concluded that the investigated ELISA method was in general accordance with the cases of clinical S . Dublin infection recorded, and that the method has a potential for national screening purposes.

Indian J Med Sci, 2000 Apr, 54(4), 149 - 50
An unusual post-operative wound infection with Salmonella typhi: case report; Sengupta S et al.; A 25 year old male student presented with a discharging sinus and swelling over right forearm, which on culture yielded S . typhi, sensitive to Ciprofloxacin . Predisposing factors were absent but there was a history of surgery for chronic osteomyelitis of right ulna and injury with cricket ball at same site . Pus obtained during surgery was sterile . Patient responded to oral Ciprofloxacin . Soft tissue infections are uncommon manifestation of salmonellosis . This case is an unusual presentation of post-operative Salmonella typhi wound infection.

Proc Natl Acad Sci U S A, 2001 Feb 27, 98(5), 2561 - 5 Epub 2001 Feb 13.
Defective localization of the NADPH phagocyte oxidase to Salmonella-containing phagosomes in tumor necrosis factor p55 receptor-deficient macrophages; Vazquez-Torres A et al.; Tumor necrosis factor receptor (TNFR) p55-knockout (KO) mice are susceptible profoundly to Salmonella infection . One day after peritoneal inoculation, TNFR-KO mice harbor 1,000-fold more bacteria in liver and spleen than wild-type mice despite the formation of well organized granulomas . Macrophages from TNFR-KO mice produce abundant quantities of reactive oxygen and nitrogen species in response to Salmonella but nevertheless exhibit poor bactericidal activity . Treatment with IFN-gamma enhances killing by wild-type macrophages but does not restore the killing defect of TNFR-KO cells . Bactericidal activity of macrophages can be abrogated by a deletion in the gene encoding TNFalpha but not by saturating concentrations of TNF-soluble receptor, suggesting that intracellular TNFalpha can regulate killing of Salmonella by macrophages . Peritoneal macrophages from TNFR-KO mice fail to localize NADPH oxidase-containing vesicles to Salmonella-containing vacuoles . A TNFR-KO mutation substantially restores virulence to an attenuated mutant bacterial strain lacking the type III secretory system encoded by Salmonella pathogenicity island 2 (SPI2), suggesting that TNFalpha and SPI2 have opposing actions on a common pathway of vesicular trafficking . TNFalpha-TNFRp55 signaling plays a critical role in the immediate innate immune response to an intracellular pathogen by optimizing the delivery of toxic reactive oxygen species to the phagosome.

Berl Munch Tierarztl Wochenschr, 2001 Jan-Feb, 114(1-2), 30 - 4
{Sampling plan for the establishment of a serologic Salmonella surveillance for slaughter pigs with meat juice ELISA}; Osterkorn K et al.; The guidelines of the German Ministery of Food, Agriculture and Forestry outlining a Salmonella surveillance programme, "Leitlinien fur ein Programm zur Reduzierung des Eintrags von Salmonellen durch Schlachtschweine in die Fleischgewinnung" (February 5th, 1998), provide a staggered spot-check size depending on the annual production of slaughtery pigs . A classification of farms into three quality categories (< 20%, 20-40%, and > 40%) is performed by salmonella antibody levels detected in meat samples using ELISA . Beside a fundamental inquiry into the salmonella status, the programme ought to lead to a decreased burden on slaughtery pigs and finally to a reduced salmonella entry into meat handling and processing companies . The spot-check plan is based on an unfavourable initial position and does not consider the real situation of salmonella load in pig fattening farms . For many farms the procedure will lead to an unjustified expenditure of examinations . In simple model calculations it is shown how a significant reduction of testing amount can be reached and statistical reliability is guaranteed, too . At the same time, we attempt to find a compromise between optimal spot check size and practicability . For reasons of free enterprise, an additional category would be desirable containing farms without any positive antibody titres in the samples . The results achieved so far indicate that a large number of German slaughter pig producers would fall into this category, without the necessity of a higher examination effort.

Shock, 2001 Feb, 15(2), 124 - 9
Binding specificity of polymyxin B, BPI, LALF, and anti-deep core/lipid a monoclonal antibody to lipopolysaccharide partial structures; Kellogg TA et al.; The deep core/lipid A (DCLA) region of gram-negative bacterial lipopolysaccharide (LPS) is common to most gram-negative pathogens and contains anionic phosphoryl groups plus numerous acyl chains as part of the toxic lipid A moiety . Several disparate agents that antagonize the effects of LPS exhibit extensive physicochemical similarities (hydrophobicity, cationic charge) within their binding domains . It is presumed that binding to the DCLA region by each of these antagonists-cross-reactive anti-LPS monoclonal antibodies (mAbs), polymyxin B (PmB), plus bactericidal permeability-increasing protein (BPI) and Limulus anti-LPS factor (LALF)-may be related to these properties . Therefore, we hypothesized that in addition to secondary and tertiary protein conformation, electrostatic interactions involving the negatively charged phosphoryl groups, hydrophobic interactions involving the acyl chains of lipid A, or both might be important factors that promote LPS antagonism . Binding of PmB, BPI, LALF, or anti-DCLA mAb 1B6 to Salmonella minnesota monophosphoryl lipid A (MPLA), diphosphoryl lipid A (DPLA), and Salmonella minnesota Re (which possess a common structural moiety, but vary considerably in structure and charge) was examined . Highly phosphorylated DNA and bovine serum albumin served as unrelated structural controls . BPI bound MPLA, which is hydrophobic and minimally charged, while mAb 1B6 bound anionic DNA; neither PmB nor LALF were reactive with MPLA or DNA . We surmised that hydrophobic interactions play a role in BPI binding to LPS, and although electrostatic interactions appear to be important for binding of mAb 1B6 to DCLA, they may not contribute to as great an extent for PmB, BPI, or LALF . Thus our data support the contention that the contribution of these specific physicochemical factors varies among endotoxin antagonists.

Carcinogenesis, 1980 Sep, 1(9), 801 - 2
Comparative activity of 4,4'-diaminobiphenyl (benzidine) and its terphenyl analogue, 4,4'-diaminoterphenyl, in two in vitro assays for potential carcinogenicity; Ashby J et al.; The carcinogen 4,4'-diaminobiphenyl (benzidine) has been compared in vitro with its terphenyl analogue 4,4''-diaminoterphenyl using the Salmonella reverse mutation assay and the BHK cell-transformation assay . The responses observed, taken together with a consideration of chemical structures, indicate that the terphenyl compound is a potential carcinogen . These findings may contribute to an understanding of the mechanism of action of benzidine as a carcinogen.

Carcinogenesis, 1980, 1(11), 925 - 30
Mutagenicity of cimetidine in nitrite-enriched human gastric juice; De Flora S et al.; A mutagenic response was obtained in the Salmonella/microsome reversion test by preincubating sodium nitrite and cimetidine in human gastric juice from untreated individuals, or even by adding nitrite to gastric juice samples from patients receiving cimetidine . Both base-pair substitutions (strains TA1535 and TA100) and, though very weakly, also frameshift errors (TA1537, TA1538 and TA98) were induced by such reaction . Mutagenicity was not affected by S-9 mix containing rat liver homogenates, neither in the sense of activation nor of deactivation . The optimal reaction occurred at high equimolar concentrations of the two precursor compounds, under physiological pH and temperature conditions and within a short time of contact . Ascorbic acid was efficient in preventing the formation of mutagenic nitrosoderivative(s).

Planta, 2000 Dec, 212(1), 136 - 43
A cDNA encoding 3-deoxy-D-manno-oct-2-ulosonate-8-phosphate synthase of Pisum sativum L . (pea) functionally complements a kdsA mutant of the Gram-negative bacterium Salmonella enterica; Brabetz W et al.; Recombinant plasmids encoding 3-deoxy-D-manno-oct-2-ulosonate-8-phosphate (Kdo-8-P) synthase (KdsA; EC 4.1.2.16) were identified from a cDNA library of Pisum sativum L . (pea) by complementing a temperature-sensitive kdsA(ts) mutant of the Gram-negative bacterium Salmonella enterica . Sequence analysis of several inserts revealed a central open reading frame encoding a protein of 290 amino acids with a high degree of amino acid sequence similarity to bacterial KdsA . The cDNA was confirmed by amplifying a 1,812-bp DNA fragment from the chromosome of pea that encoded four exons around the 5'-end of kdsA . The recombinant enzyme was subcloned, overexpressed and characterized to synthesize Kdo-8-P from D-arabinose-5-phosphate and phosphoenolpyruvate . The pH optimum was 6.1 and the activity of the enzyme was neither stimulated by the addition of divalent cations nor inhibited by EDTA . The cDNA of kdsA could not complement Escherichia coli K-12 strain AB3257, which is defective in all three isoenzymes (AroFGH) of 3-deoxy-D-arabino-hept-2-ulosonate-7-phosphate (Dha-7-P) synthase (EC 4.1.2.15), and neither D-erythrose-4-phosphate nor D-ribose-5-phosphate could substitute for D-arabinose-5-phosphate in vitro . Thus, plant cells possess a specific enzyme for the biosynthesis of Kdo-8-P with remarkable structural and functional similarities to bacterial KdsA proteins.

Ann Trop Paediatr, 2000 Dec, 20(4), 297 - 303
Typhoid fever, ciprofloxacin and growth in young children; Doherty CP et al.; Typhoid fever remains a significant public health problem in Southern Asia, particularly with the emergence of multi-resistant strains of Salmonella typhi in the late 1980s . Use of ciprofloxacin in children, although discouraged, is increasing and we aimed to assess whether its use affects growth or the prevalence of joint symptomology . Children under 6 years of age diagnosed as typhoid fever on the basis of a positive Widal test were recruited in the outpatient department of a paediatric teaching hospital after treatment had been initiated . During 6 months follow-up, prevalences of arthritis/arthralgia and ponderal, linear and knemometric growth were recorded . Seventy-five children were recruited (mean age 32 months, mean weight-for-height Z-score--1.3, mean height-for-age Z-score 1.4) and 29 (39%) of them received ciprofloxacin . No significant adverse effects on ponderal, linear or knemometric growth, or on the incidence of arthritis/arthralgia were found to be associated with the use of ciprofloxacin . Knemometric and ponderal catch-up growth was demonstrable 30 days after diagnosis but linear growth was still declining 3 months after diagnosis with catch-up growth demonstrable only after 6 months . We conclude that ciprofloxacin is commonly used in typhoid fever and has no adverse effects on growth or joint symptomology.

Indian J Exp Biol, 2000 Apr, 38(4), 358 - 62
Salmonella . typhi OMPs induced immunomodulation in peritoneal macrophages; Kashyap DR et al.; The immunomodulatory properties of outer membrane proteins (OMPs) from S . typhi Ty2 were studied in mouse model at 72 hr and 20 days post-infection . Inspite of reduction in the number of macrophages and their protein content observed in the immunized group vis-a-vis infected group, OMPs activated macrophages showed significant upregulation of NO . At 20 days post infection, the level remained almost the same suggesting the prolonged cytotoxic and cytostatic activity due to the long lasting effects of OMPs activated macrophages . Higher activity of SOD in these aged cells pointed out towards the protective efficacy of OMPs to keep the macrophages themselves away from the noxious effects of O2- . Lower level of acid phosphatase in the macrophages from immunized mice group indicated the involvement of oxygen dependent rather than oxygen independent killing process . The enhanced uptake of organisms and their killing could be related to the production of oxygen and nitrogen radicals in the OMPs immunized group.

Kansenshogaku Zasshi, 2001 Jan, 75(1), 48 - 52
{Two cases of typhoid fever with reduced susceptibility to fluoroquinolones}; Adachi T et al.; Two separate febrile Indian patients who reside in Japan and had recently returned from their country were diagnosed as suffering from typhoid fever . Fluoroquinolone therapy was clinically ineffective and the addition of a third-generation cephalosporin was required in each case . Each strain of Salmonella Typhi was resistant to nalidixic acid in vitro and also showed higher minimal inhibitory concentration to other quinolones than usual susceptible strains . Similar cases of typhoid fever responding poorly to quinolone treatment have been observed in the Indian subcontinent, south-east Asia and central Asia since the early 1990s, and potential spread by travelers into Japan is of serious concern . Although quinolones still remain the drugs of choice for treatment of typhoid fever, physicians should be aware of the possibility and implications of clinical treatment failure.

Epidemiol Infect, 2000 Dec, 125(3), 491 - 8
Initially unrecognized distribution of a commercially cooked meat product contaminated over several months with Salmonella serotype Infantis; Kohl KS et al.; An outbreak of salmonellosis occurred among 63 wedding participants . The outbreak was investigated through cohort, laboratory, and environmental studies . Consumption of rice-dressing made from a commercially cooked, meat-based, rice-dressing mix was strongly associated with illness . Nineteen patient isolates, six company/grocery store isolates cultured from the rice-dressing mix, and one environmental isolate from a pump in the production line were of an identical outbreak strain of Salmonella Infantis characterized by pulsed-field gel electrophoresis . In the production line, cooked rice-dressing mix tested negative for S . Infantis before and positive after contact with the contaminated pump . The dressing-mix had an estimated 200 colony-forming units of salmonella per gram of product, and > 180,000 pounds were distributed in 9 states for > or = 2 months before contamination was recognized . Food manufacturers should be required to use systematic, hazard analysis critical control point risk management practices for all processed meat products, validated by periodic microbiologic monitoring of the end product.

Epidemiol Infect, 2000 Dec, 125(3), 481 - 9
Usefulness of genetic typing methods to trace epidemiologically Salmonella serotype Ohio; Soto SM et al.; Different genetic typing procedures were applied in an epidemiological study of Salmonella serotype Ohio . Isolates that generated identical DNA fingerprints (HinclI ribotypes, ERIC and RAPD profiles) were clustered into the same lineage, and the addition of data from plasmid, integron and resistance profiles was used to differentiate types . Results led to the determination of the endemic and the emergent epidemic types at specific times, and to ascertain the clinical and epidemiological impact of each type . In the series analysed (47 clinical isolates and 3 non-clinical isolates) 11 lineages and 32 types were found . Two lineages were considered prevalent and endemic, and during an epidemiological alert (Spain, 1998) a re-emergence and spread of organisms mainly from the most frequent lineage had occurred . The combination of H-ribotype with ERIC profile, as primary markers, and resistance profile with plasmid profile, as secondary markers, was shown to be the most useful tool to trace epidemiologically Ohio.

Epidemiol Infect, 2000 Dec, 125(3), 467 - 72
The role of outbreaks in developing food safety policy: population based surveillance of salmonella outbreaks in Wales 1986-98; Palmer S et al.; In developing public policy on food safety, systematic identification and thorough investigation of all general outbreaks is necessary in order to avoid bias towards highly publicised outbreaks . In Wales, from 1986 to 1998, 87 general foodborne outbreaks of salmonellosis were identified . Most outbreaks occurred at functions or were associated with small catering outlets such as bakeries and sandwich bars . In 50 outbreaks, a vehicle of infection was confirmed microbiologically and/or epidemiologically . The most common food vehicles were those containing shell eggs . Salmonella enteritidis outbreaks were significantly more likely than outbreaks of other serotypes to be associated with vehicles containing shell eggs, suggesting that eggs were also the source of infection in many outbreaks . The routine use of analytical epidemiological studies to identify vehicles in outbreaks is recommended.

Indian J Pathol Microbiol, 2000 Apr, 43(2), 135 - 8
Multidrug resistant Salmonella typhi in Rourkela, Orissa; Das U et al.; Out of 5410 blood samples 715 samples were found positive for Salmonella typhi . Enteric fever was prevalent for last three years in Rourkela . In last two years, a number of multidrug resistant strains of Salmonella typhi was isolated which constituted almost 16.1% of the total isolates . In this study, chloramphenicol sensitivity was found quite high (86.5%) and ceftriaxone showed 100% sensitivity . Resistance to ciprofloxacin was found 2.5% which due to direct consequence of indiscriminate use of antibiotics, either singly or in combination.

Tidsskr Nor Laegeforen, 2000 Dec 10, 120(30), 3670 - 1
{Salmonella infection from turtles}; Torfoss D et al.; Small turtles are asymptomatic carriers of Salmonella . Infants are particularly at risk of clinical infection . We describe an eight months old boy who became sick with Salmonella . The family had two turtles . Salmonella Abony was found in faeces from the child and in samples from both turtles . Commercial distribution of reptiles is prohibited in Norway . However, illegal import from other countries where no such ban exist is common . There are an estimated 10,000 pet reptiles in the Oslo region, most of them are turtles . More than 90% of turtles may be carriers of Salmonella . Many owners of turtles are not aware of the risk of salmonellosis from their pets.

Tidsskr Nor Laegeforen, 2000 Dec 10, 120(30), 3666 - 9
{Norwegian newspapers' presentation of Salmonella}; Haukenes A; BACKGROUND: Compared to other microbes, Salmonella gets rather frequent coverage in Norwegian newspapers . METHODS: This article reports a qualitative content analysis of three Norwegian newspapers' coverage of Salmonella in the period January 1996 to July 1998 . We focus on aspects of the "risk image" given to Salmonella, with special emphasis on the type of solutions or measures that are associated with the Salmonella problem . RESULTS: The analysis shows that when a newspaper defines Salmonella as a potential risk in Norway, the responsibility and relevant solutions are placed mainly at the political and to some extent at the central administrative level . When Salmonella is defined as a current risk, there seems to be a shift to central and individual levels . With individual solutions the responsibility for Salmonella illness is placed at the consumers and their personal and food hygiene, and a relevant measure seems to be to educate the consumers to cope with the Salmonella risk themselves . INTERPRETATION: In Norway, Salmonella is a minor health problem compared to other countries . With the ongoing harmonisation between Norwegian and EU regulations, the Salmonella situation may change, and the relevant solutions may then imply a transfer of the responsibility for health to the individual . This raises the question of whether solutions based on individuals bearing responsibility for their personal health are desirable when it comes to such aspects as food, microbes and related risks.

Biosens Bioelectron, 2000, 15(11-12), 615 - 21
Evaluation of antibody immobilization methods for piezoelectric biosensor application; Babacan S et al.; The immobilization of anti-Salmonella antibodies by two methods were studied and evaluated for their potential use in a piezoelectric biosensor . The optimum temperature-time combinations for the highest immobilization yields were determined for both methods . Protein A binding was found to be 67.4+/-3.8% on the gold surface which then allowed an immobilization of 42.1+/-2.09% antibody . The degree of antibody immobilization via surface aldehyde groups of glutaraldehyde (GA) on a precoated quartz crystal with polyethylenimine (PEI) was 31.6+/-0.3% . A piezoelectric probe was designed and used in dry assays to observe the frequency change due to addition of mass by the immobilization layers . The frequency changes recorded showed a better reproducibility and less added mass for the Protein A method . The frequency decrease due to microg of added antibodies was compared to frequency decrease calculated by the Sauerbrey equation . The experimental data was found to be only approximately 8% of theoretical data . The functionality of the immobilized antibodies with the Protein A method was tested with S . typhimurium in a wet chamber and the frequency decrease was compared to results of a similar system activated with PEI-GA immobilization . The frequency decreases with S . typhimurium concentration of approximately 1.5 x 10(9) CFU/ml were 50+/-2 Hz and 44+/-3 Hz for the Protein A method and PEI-GA method, respectively . It was concluded that although both methods resulted in comparable activities in terms of % immobilized protein and frequency decreases due to Salmonella binding, the Protein A method was favorable due to stability and better reproducibility of the immobilization layers.

Bull Tokyo Dent Coll, 2000 Aug, 41(3), 135 - 40
Differences in TNF-alpha producing activity from murine peritoneal macrophages induced by lipopolysaccharides of Prevotella heparinolytica and Porphyromonas gingivalis; Hirai K et al.; We compared the effects of LPSs from P . gingivalis and P . heparinolytica on the induction of tumor necrosis factor-alpha (TNF-alpha) production by murine peritoneal macrophages . The lipopolysaccharide (LPS) preparation from P . gingivalis showed a typical ladder pattern in SDS-PAGE, whereas that from P . heparinolytica formed several stained bands without a ladder pattern . When the macrophages from C3H/HeJ mice were incubated with P . gingivalis LPS, the level of TNF-alpha released in the culture supernatants was significantly higher than that with P . heparinolytica . All tested reagents except genistein strongly inhibited the production of TNF-alpha by the macrophages after induction by either LPS . These results suggested the following possibilities, i) the induction level of TNF-alpha by P . heparinolytica is similar to that of Salmonella minnesota, ii) tyrosine phosphorylation is not the only pathway for the TNF-alpha production induced by these LPSs, iii) different regulatory mechanisms are involved in TNF-alpha production in P . gingivalis LPS stimulated and P . heparinolytica LPS stimulated cells.

J Med Microbiol, 2001 Feb, 50(2), 191 - 7
Expression of type 1 fimbriae (SEF 21) of Salmonella enterica serotype enteritidis in the early colonisation of the rat intestine; Naughton PJ et al.; The involvement of type 1 fimbriae in colonisation of the rat gastrointestinal tract in vivo was investigated with Salmonella enterica serotype Enteritidis LA5 and a mutant of LA5 denoted EAV3 unable to elaborate type 1 fimbriae (SEF 21) . Rats were given a single dose of LA5 or EAV3 or a 1:1 mixture of both . LA5 was found in higher numbers in the stomach and small intestine than EAV3 at 6 h after infection with a single strain, but not after 6 days . LA5 did not out-compete EAV3 when the strains were administered together . Indeed, after 6 and 21 days, EAV3 was found in the distal small intestine and large intestine in far higher numbers than LA5 . These findings suggest that SEF 21 have an important role(s) in the early stages of infection in vivo . However, SEF 21 expression may disadvantage the pathogen in the longer term as indicated by EAV3 out-competing LA5 in the gut at 21 days.

Zh Mikrobiol Epidemiol Immunobiol, 2000 Nov-Dec, (6), 67 - 8
{Effect of Actoflor preparations on survival of Escherichia coli M-17 and Salmonella enteritidis under starvation conditions in mixed cultures}; Vakhitov TIa et al.; The viability of E . coli M-17 and S . enteritidis under starvation conditions in mono- and mixed cultures was studied . E . coli M-17 showed greater capacity for survival in mixed cultures than in monocultures, while for S . enteritidis the contrary was true . Preparations "Actoflor" enhanced the antagonistic activity of E . coli M-17, ensuring its absolute selective advantage under starvation conditions in mixed cultures . The role of E . coli M-17 low-molecular exometabolites is discussed; they are probably an important factor in the antagonistic activity of these microorganisms.

Onderstepoort J Vet Res, 2000 Dec, 67(4), 297 - 300
Bacterial colonization and endotoxin activity during experimental acute fowl typhoid in chickens; Kokosharov T; Bacterial colonization and endotoxin production were investigated before and after experimental Salmonella gallinarum infection in 8-week-old female broiler chickens . These parameters were assayed by means of colony forming units test (CFU) and the Limulus Amebocyte Lysate test (LAL), respectively . Birds were infected per os with 1,5 x 10(9) CFU/ml of wild strain of S . gallinarum isolated from a dead hen . Approximately 1,5 x 10(2); 1,3 x 10(2) and 1,2 x 10(2) CFU of S . gallinarum were recorded from 1 g of liver, 1 g of spleen and 1 ml of blood from the chickens on day 1 post infection . By day 4 corresponding data were 3,7 x 10(4); 4,8 x 10(3) and 1,1 x 10(3) respectively and on day 7 10(5) CFU were present in all three specimen types . The liver and spleen of dead birds were contaminated with more than 10(7) CFU per g . The endotoxin from S . gallinarum was found to have an activity of 1,5; 12,0 and 15,0 endotoxin units (EU)/ml on day 1, 4 and 7 after infection, respectively . No endotoxin activity was established in the blood of the control group (before infection) by the LAL test . This is the first time the connection between the amount of live S . gallinarum in the blood, liver and the circulating level of endotoxin in the blood during the infectious stage of experimental acute fowl typhoid, has been demonstrated.

Vet Q, 2001 Jan, 23(1), 2 - 10
Human health hazards associated with the administration of antimicrobials to slaughter animals . Part I . An assessment of the risks of residues of tetracyclines in pork; Berends BR et al.; This article describes the assessment of consumer risks of residues of tetracyclines in slaughter pigs in the Netherlands . The assessed risks were toxic and allergic reactions, and the disturbance of the consumers' intestinal flora . Toxic and allergic reactions in humans and animals have only been observed at therapeutic doses, affecting between an estimated 1 in 5,000 and one 1 in 140,000 individuals exposed . Residues of tetracyclines in pigs are closely associated with treatment with injectable formulations . Established Maximum Residue Levels (MRLs) do not reflect actual consumer risks in case a limit is violated incidentally . For example, when the established MRLs for tetracyclines in meat are exceeded with a factor 400, 40,000, and 200,000, respectively, the actual risk of an adverse drug reaction for the consumer following a single consumption of this meat is maximally 1 in 3 million, 1 in 300,000, and 1 in 8,000, respectively . At the current estimated low levels of incidental exposure via pork, the annual risk of negative health effects for a random consumer is estimated at maximally 1 in 33 million . The annual risk that a temporary disturbance of the intestinal flora may also result in a facilitated infection with certain enteropathogens, such as Salmonella spp., is estimated at 1 in 45 million . It is concluded that the current microbiological risks of pork are greater than the risks of residues of tetracyclines as such, and that the control of the microbiological risks of pork should therefore be given first priority.

Vet Q, 2001 Jan, 23(1), 10 - 21
Human health hazards associated with the administration of antimicrobials to slaughter animals . Part II . An assessment of the risks of resistant bacteria in pigs and pork; Berends BR et al.; Risks for the consumer regarding the acquisition of resistant bacteria and/or resistance genes via the consumption of pork are discussed . In general, Salmonella spp . and Escherichia coli that originate from animals do not easily transfer their resistance genes to the resident intestinal flora of humans . The prevalence of resistant E . coli in humans seems more associated with being a vegetarian (odds ratio (OR) 1.89) than with the consumption of meat and meat products . Other risk factors are treatment with antimicrobials (OR 2-5), becoming hospitalized (OR 5.93), or working in a health setting (OR 4.38) . In the Netherlands, annually an estimated 45,000 people (0-150,000) become a carrier of resistant E . coli and/or resistance genes that ori ginate from pigs, while an estimated 345,000 persons (175,000-600,000) become a carrier of resistant E . coli and/or resistance genes that originate from hospitals, e.g . other patients . Any problems with resistant Salmonella spp . that stem from pigs are, in fact, an integral part of the total problem of food-borne salmonellosis . Sometimes there are outbreaks of a specific multi-resistant clone of S . typhimurium that causes problems in both farm animals and humans . The probability that in the next 30 years there is no or maximally one outbreak of a specific clone that originates from pig herds is estimated at about 75% . Antimicrobials used as a growth promoter can have a measurable influence on the prevalence of resistant bacteria . The likely chain of events regarding avoparcin and the selection and dissemination of resistance against vancomycin in the enterococci gives the impression that the impact of the use of antimicrobials in animals on the prevalence of resistance in humans is largely determined by whether resistance genes are, or become, located on a self-transferable transposon . Furthermore, consumer health risks of antimicrobials used in slaughter pigs are mainly determined by the selection and dissemination of bacterial resistance and much less by the toxicological properties of any residues in pork . It is also concluded that most of the problems with resistant bacteria in humans are associated with the medical use of antimicrobials, and that the impact of particularly the veterinary use of antimicrobials is limited . However, the impact of antimicrobials used as a feed additive appears to be much greater than that of antimicrobials used for strictly veterinary purposes . The use of antimicrobials as a feed additive should therefore be seriously reconsidered.

Int J Food Microbiol, 2001 Jan 22, 63(1-2), 99 - 107
Influence of holding temperature on the growth and survival of Salmonella spp . and Staphylococcus aureus and the production of staphylococcal enterotoxin in egg products; Yang SE et al.; In this study, growth and survival of Salmonella spp . and Staphylococcus aureus in steamed egg and scrambled egg held at 5, 18, 22, 37, 55 and 60 degrees C are investigated . The production of staphylococcal enterotoxin in steamed egg is also examined . Results reveal that Salmonella spp . and Staph . aureus in the egg products multiply best at 37 degrees C, followed closely by 22 and 18 degrees C . Neither pathogen showed growth in the egg products held at 5 degrees C . Initial inoculation dose, holding temperature and holding time affected the population of both organisms found in the egg products . Staphylococcal enterotoxin A (SEA) and B (SEB) are detected only in the egg products held at 37 or 22 degrees C . After holding at 37 degrees C for 36 h, scrambled egg inoculated with ca . 5.0 log cfu/g Staph . aureus contains the highest levels of SEA (> 64 ng/g) and SEB (> 64 ng/g) . Although Salmonella spp . and Staph . aureus grow better in steamed eggs than in scrambled eggs, production of staphylococcal enterotoxin, in general, was higher in scrambled eggs than in steamed eggs . On the other hand, a repaid destruction of the test organisms in steamed eggs held at 60 degrees C was observed . Holding the steamed eggs at 60 degrees C, Salmonella spp . and Staph . aureus with an initial population of ca . 5.9 and 5.6 log cfu/g, respectively, reduced to a non-detectable level in 1 h.

Int J Food Microbiol, 2001 Jan 22, 63(1-2), 165 - 7
Salmonella serotypes isolated from turkey meat in Albania; Beli E et al.; Eleven (11) Salmonella strains were recovered from 11 (8.2%) out of 134 turkey meat samples in Albania, for the period of time 1996-1998 . The percentage of Salmonella positive turkey meat samples varied with 5% in 1996 (3 out of 60), 14.7% in 1997 (5 out of 34) and 7.5% in 1998 (3 out of 40) . The isolated strains were found to belong to 3 different Salmonella serogroups; 6 isolates to serogroup B, 4 isolates to serogroup D and 1 isolate to serogroup C . Five (5) different serotypes were encountered; Salmonella enteritidis (4 isolates), Salmonella agona (3 isolates), S . saint-paul, S . reading and S . blockley with only one isolate each . One Salmonella strain, belonging to serogroup B, was not completely serotyped.

Eksp Klin Farmakol, 2000 Nov-Dec, 63(6), 43 - 8
{Potential role of the antimutagenic effect of xymedone in modification of immunoreactivity}; Cherepnev GV et al.; Effects of the pyrimidine derivatives of xymedone and methyluracil upon the induction of point mutations of the base pair substitution type in the Salmonella/microsome test and the frequency of chromosome aberrations in the lymphocytes of patients with the chronic osteomyelitis diagnosis . Xymedone more effectively than methyluracil inhibited the induction of point mutations by nitrosomethylurea . In the case of the cyclophosphane induced mutagenesis, the two preparations exhibited comparable antimutagen effects . Both xymedone and methyluracil (1.5 g/day, 10 days) reduced the (increased) frequency of chromosomal aberrations in the lymphocytes of patients with the chronic osteomyelitis diagnosis . The anticlastogenic effect of methyluracil vanished 5 days after termination of the 10-day administration course, while xymedone exhibited an afteraction anticlastogenic effect over this period . Interrelation of the antimutagen effect and immunomodulating activity of xymedone is discussed.

Salud Publica Mex, 2000 Nov-Dec, 42(6), 490 - 5
{Salmonella serotypes identified in Mexican health services}; Gutierrez-Cogco L et al.; OBJECTIVE: To identify the different Salmonella strain serotypes isolated at public and private laboratories in Mexico and at the Institute for Epidemiologic Diagnosis and Referral (InDRE) . MATERIAL AND METHODS: A total of 24,394 Salmonella strains collected from 1972 to 1999 in public and private health laboratories of Mexico were analyzed with the Kauffmann-White method, using antisera produced by InDRE, according to Centers for Disease Control and Prevention (CDC, Atlanta, GA) standards; 15,843 (64.9%) samples were from human sources and 8,551 (35.1%) from non-human sources . RESULTS: One hundred ninety nine different serotypes were identified . The most frequent serotype in human beings was S . Typhimurium (20.4%), followed by S . Enteritidis (18.3%) . In the past few years, the frequency of S . Enteritidis has been increasing, surpassing that of S . Typhimurium since 1991 . Presently S . Enteritidis is the most frequently isolated serotype . In non-human sources, S . Derby (13.8%) and S . Anatum (8.5%) are the most frequent strains . CONCLUSIONS: Salmonella serotypes most frequently isolated in Mexico are: S . Typhimurium, S . Enteritidis, S . Derby, S . Agona y S . Anatum . From the epidemiologic standpoint, it is necessary to identify circulating and emerging Salmonella serotypes in order to target pertinent preventative interventions.

Int J Med Microbiol, 2000 Dec, 290(7), 619 - 26
Sequence analysis and distribution in Salmonella enterica serovars of IS3-like elements; Collighan RJ et al.; The genome of Salmonella enterica serovar Enteritidis was shown to possess three IS3-like insertion elements, designated IS1230A, B and C, and each was cloned and their respective deoxynucleotide sequences determined . Mutations in elements IS1230A and B resulted in frameshifts in the open reading frames that encoded a putative transposase to be inactive . IS1230C was truncated at nucleotide 774 relative to IS1230B and therefore did not possess the 3' terminal inverted repeat . The three IS1230 derivatives were closely related to each other based on nucleotide sequence similarity . IS1230A was located adjacent to the sef operon encoding SEF14 fimbriae located at minute 97 of the genome of S . Enteritidis . IS1230B was located adjacent to the umuDC operon at minute 42.5 on the genome, itself located near to one terminus of an 815-kb genome inversion of S . Enteritidis relative to S . Typhimurium . IS1230C was located next to attB, the bacteriophage P22 attachment site, and proB, encoding gamma-glutamyl phosphate reductase . A truncated 3' remnant of IS1230, designated IS1230T, was identified in a clinical isolate of S . Typhimurium DT193 strain 2391 . This element was located next to attB adjacent to which were bacteriophage P22-like sequences . Southern hybridisation of total genomic DNA from eighteen phage types of S . Enteritidis and eighteen definitive types of S . Typhimurium showed similar, if not identical, restriction fragment profiles in the respective serovars when probed with IS1230A.

Int J Med Microbiol, 2000 Dec, 290(7), 605 - 17
Prevalence and polymorphism of genes encoding translocated effector proteins among clinical isolates of Salmonella enterica; Prager R et al.; Pathogenic Salmonella enterica strains are capable of causing local and/or systemic infections . They employ two type III secretion systems to translocate an array of virulence-associated proteins (effector proteins) directly into the cytosol of target cells of the host . Earlier data had shown that changes in the repertoire of translocated effector proteins may contribute to the adaptation of Salmonella strains to new hosts and to the emergence of epidemic strains . Using PCR and Southern blot techniques the presence of and the polymorphism among the genes encoding the translocated effector proteins SopB, SopD, SopE, SopE2, SipA, SipB, SipC, AvrA, and SptP was studied in 71 phylogenetically well characterised S . enterica subspecies I (subspecies enterica) strains of the SARB collection and in 209 clinical and epidemic isolates of S . enterica subspecies I belonging to various serovars, phage types, and genotypes . All these Salmonella strains harbour all these respective genes with the exception of sopE and avrA which have been identified in only some of them . Several of the studied genes display genetic polymorphisms (RFLP) . These RFLP patterns did not show a strict correlation with the genetic distance, the grouping genes in order to understand their role in the evolution of Salmonella as a pathogen.

J Endod, 2000 Jun, 26(6), 321 - 4
The mutagenic potential of AH+ and AH26 by Salmonella/microsome assay; Jukic S et al.; The aim of this study was to examine the mutagenic potential of canal sealers AH+ and AH26 by Salmonella/microsome assay . The materials were tested immediately after mixing, 1 hr and 1 month later, respectively . The dimethyl sulfoxide extracts of sealers in amounts of 3.0, 1.5, and 0.75 microliters/plate were used . The plated bacterial strains of Salmonella were TA 98 and TA 100 . The results showed that AH+ is mutagenic toward strain TA 100 1 hr after mixing . One month after mixing, mutagenic activity was expressed only in TA 98 . Paste A showed strong mutagenicity toward TA 100 . AH26 was more mutagenic to the TA 100 immediately after mixing, 1 hr later, and 1 month after it was polymerized . Also it was mutagenic toward TA 98 in the polymerized condition . Further examinations should be conducted to establish a definitive conclusion about mutagenic potential for these two endodontic materials.

J Food Prot, 2001 Jan, 64(1), 12 - 6
Salmonella in the lairage of pig slaughterhouses; Swanenburg M et al.; The purpose of this study was to determine if lairages of pig slaughterhouses can act as a source of contamination of slaughtered pigs with Salmonella . The prevalence and variety of serotypes of Salmonella in the lairages of two pig slaughterhouses were determined, and the efficacy of the usual cleaning and disinfection on the presence of Salmonella was estimated . Lairages of two pig slaughterhouses were sampled three times when pigs were present . Furthermore, these lairages were sampled after the usual cleaning and disinfection, whereas the lairage of one slaughterhouse was sampled an additional time after improved cleaning and disinfection . Samples were collected by swabbing floor and wall surfaces and collecting the residing fluids on the floor throughout the lairage . Salmonella was isolated in 70 to 90% of the samples when pigs were present . The usual cleaning and disinfection reduced the level of contamination with Salmonella to 25% positive samples, whereas improved cleaning and disinfection reduced this level to 10% positive samples . It is concluded that the waiting period in the lairage of at least 2 h contains a substantial risk for slaughter pigs to become infected with Salmonella, especially for pigs originating from Salmonella-free herds . The usual cleaning and disinfection of the lairage were not sufficient to eliminate this risk, whereas an improved procedure for cleaning and disinfection still was unsatisfactory.

J Food Prot, 2001 Jan, 64(1), 113 - 6
Bactericidal effects of negative air ions on airborne and surface Salmonella enteritidis from an artificially generated aerosol; Seo KH et al.; The bactericidal effect of high levels of negative ions was studied using a custom-built electrostatic space charge device . To investigate whether the ion-enriched air exerted a bactericidal effect, an aerosol containing Salmonella Enteritidis (SE) was pumped into a sealed plastic chamber . Plates of XLT4 agar were attached to the walls, top, and bottom of the chamber and exposed to the aerosol for 3 h with and without the ionizer treatment . The plates were then removed from the chamber, incubated at 37 degrees C for 24 h, and colonies were counted . An average of greater than 10(3) CFU/plate were observed on plates exposed to the aerosol without the ionizer treatment (control) compared with an average of less than 53 CFU/plate on the ionizer-treated plates . In another series of experiments, the SE aerosol was pumped for 3 h into an empty chamber containing only the ionizer and allowed to collect on the internal surfaces . The inside surfaces of the chamber were then rinsed with 100 ml phosphate-buffered saline that was then plated onto XLT4 plates . While the rinse from the control chamber contained colony counts greater than 400 CFU/ml of wash, no colonies were found in the rinse from the ionizer-treatment chamber . These results indicate that high levels of negative air ions can have a significant impact on the airborne microbial load, and that most of this effect is through direct killing of the organisms . This technology, which also causes significant reduction in airborne dust, has already been successfully applied for poultry hatching cabinets and caged layer rooms . Other potential applications include any enclosed space such as food processing areas, medical institutions, the workplace, and the home, where reduction of airborne and surface pathogens is desired.

Can Vet J, 2001 Jan, 42(1), 33 - 7
An investigation of the etiology of a mild diarrhea observed in a group of grower/finisher pigs; Johnston WT et al.; An investigation into a mild diarrhea in a group of grower/finisher pigs was carried out in order to determine the etiology . A tiamulin injection and a carbadox-medicated ration were given to pens of pigs in a 2 x 2 factorial experimental design . Pens of pigs were assessed a score, based on the consistency of the feces in the pen, each week . The clinical investigation looked for the intestinal pathogens Brachyspira pilosicoli, B . hyodysenteriae, Lawsonia intracellularis, Salmonella spp., Yersinia spp., transmissible gastroenteritis virus, and rotavirus . Despite a rigorous investigation, the diarrhea was not attributed to any pathogen . A mild colitis was noted among pigs necropsied while affected with diarrhea . Improved diagnostic tools may allow a more effective response to an outbreak of mild disease, while at the same time reducing the amount of antimicrobials used in swine production.

Biosci Biotechnol Biochem, 2000 Nov, 64(11), 2395 - 401
Dietary antioxidants fail in protection against oxidative genetic damage in in vitro evaluation; Sun M et al.; Carcinogenesis is believed to be induced through the oxidative damage of DNA, and antioxidants are expected to suppress it . So, the polyphenolic antioxidants in daily foods were investigated to see whether they protect against genetic damage by active oxygen . In the evaluation, we used a bioassay and a chemical determination, a Salmonella mutagenicity test for mutation by a N-hydroxyl radical from one of the dietary carcinogens 3-amino-1-methyl-5H-pyrido{4,3-b}indole and the formation of 8-hydroxyl (8-OHdG) from 2'-deoxyguanosine (2'-dG) in a Fenton OH-radical generating system . Thirty-one antioxidants including flavonoids were compared in terms of radical-trapping activity with bacterial DNA and 2'-dG . Antioxidants inhibited the mutation but the IC50 values were in the mM order . Against 8-OHdG formation, only alpha-tocopherol had a suppressive effect with an IC50 of 1.5 microM . Thus, except alpha-tocopherol, the dietary antioxidants did not scavenge the biological radicals faster than bacterial DNA and intact 2'-dG, indicating that they failed to prevent oxidative gene damage and probably carcinogenesis.

Res Microbiol, 2000 Dec, 151(10), 893 - 6
Supplement 1999 (no . 43) to the Kauffmann-White scheme; Popoff MY et al.; This supplement reports the characterization of 26 new Salmonella serovars recognized in 1999 by the WHO Collaborating Centre for Reference and Research on Salmonella: 15 were assigned to S . enterica subsp . enterica, seven to subspecies salamae, two to subspecies diarizonae, and one to subsp . houtenae; and one to S . bongori . In addition, the antigenic factor H:z89 is described.

Rev Panam Salud Publica, 2000 Nov, 8(5), 342 - 7
Molecular analysis of Salmonella enteritidis isolates from the Caribbean by pulsed-field gel electrophoresis; Adesiyun A et al.; Using pulsed-field gel electrophoresis (PFGE), between 1987 and 1996 we analyzed Salmonella enteritidis isolates from gastroenteritis cases in four Caribbean countries: Barbados, Saint Kitts and Nevis, Saint Lucia, and Trinidad and Tobago . We also determined the resistance of the isolates to 12 antimicrobial agents . Of the 129 isolates of S . enteritidis available for testing, DNA digested by XbaI revealed 13 distinctive PFGE patterns . The most prevalent XbaI PFGE patterns were group 1 (88 of 129 isolates, 68.2%) and group 2 (26 of 129, 20.2%) . The patterns found among S . enteritidis isolates correlated with the geographical origin of the isolates . Of the 28 isolates from Barbados, 20 of them (71.4%) belonged to XbaI PFGE group 2, and of the 93 isolates from Trinidad and Tobago, 78 of them (83.9%) belonged to group 1 . SpeI digestion of S . enteritidis genome was not as discriminatory as XbaI . Overall, of the 129 isolates, 67 of them (51.9%) exhibited resistance to one or more of the 12 antimicrobial agents that we tested . The prevalence of resistance was 53.8% for the S . enteritidis isolates tested from Trinidad and Tobago, 50.0% for those from Barbados, 28.6% for those from Saint Lucia, and 100.0% for one isolate from the island of Saint Kitts . Resistance was highest to triple sulfur (59 of 129 isolates, 45.7%), followed by furadantoin (10 of 129, 7.8%), ampicillin (7 of 129, 5.4%), and carbamycin (5 of 129, 3.9%).

Commun Dis Intell, 2000 Nov, 24(11), 336 - 40
A waterborne outbreak of Salmonella Saintpaul; Taylor R et al.; Contamination of a tank water supply system led to an outbreak of Salmonella Saintpaul with 28 cases of gastroenteritis amongst over 200 workers at a large construction site . The outbreak was identified following notification of two salmonellosis cases by general practitioners from different towns during March 1999 . The source of infection, contaminated drinking water, was identified through environmental sampling and confirmed by epidemiological investigations . Frogs and/or mice may have been the original source of the contamination . This report details control measures, the results of investigations and recommendations for future research.

Arch Mal Coeur Vaiss, 2000 Nov, 93(11), 1343 - 7
{Salmonella aortic valve endocarditis presenting with rupture of a femoral artery mycotic aneurysm}; Mourot S et al.; The incidence of Salmonella enteritidis infections has greatly increased over the last few years . Cardiovascular are amongst the most severe extra-digestive complications . The authors report a case of Salmonella enteritidis presenting with rupture of a femoral artery mycotic aneurysm in a chronic alcoholic patient . Salmonella enteritidis was isolated from blood cultures and the operation specimen after the obligatory limb amputation . The outcome was finally favourable after appropriate antibiotic therapy with a residual, stable grade 3 aortic regurgitation . This rare condition is generally observed in immuno-compromised subjects and carries a high mortality (40 to 70% of cases) . The initial infectious signs may be masked, and, in these cases, rupture of an aneurysm is often the mode of presentation . Rapid treatment is essential with, ideally, resection of the aneurysm with reestablishment of arterial continuity and adapted, prolonged antibiotic therapy.

Tijdschr Diergeneeskd, 2000 Dec 15, 125(24), 748 - 51
{Antibiotics for uncomplicated Salmonella enteritis: are they useful? A critical consideration of the literature}; van Duijkeren E et al.; This article, a version of an earlier publication (6), reviews the human and veterinary literature on the effect of anti-microbials on uncomplicated Salmonella enteritis . The main conclusion is that there is no evidence for the widely held belief that anti-microbials prolong the time that salmonellae are shed.

Pharmazie, 2000 Dec, 55(12), 947 - 52
New bisabolane sesquiterpenes from Ligularia songarica; Fu B et al.; Phytochemical investigation of Ligularia songarica (Compositae) afforded seven new bisabolane-type sesquiterpenes . Their structures were confirmed on the basis of spectroscopic methods, especially 2D-NMR techniques, and compound 7 showed stronger antibacterial activity against Escherichia coli, Pseudomonas acruginosa and Salmonella pullorum.

Cell Microbiol, 2000 Dec, 2(6), 443 - 52
The regulatory protein PhoP controls susceptibility to the host inflammatory response in Shigella flexneri; Moss JE et al.; The PhoP/PhoQ two-component regulatory system controls transcription of several key virulence genes essential for Salmonella survival in the host cell phagosome . Here, we determine that the PhoP/PhoQ system also regulates virulence in the aetiological agent of bacillary dysentery, Shigella flexneri, even though this pathogen escapes from the phagosome into the cytoplasm of the host cell . A phoP mutant of Shigella established infections and induced an acute inflammatory response in two different animal models . However, infections with phoP mutant bacteria were resolved more rapidly than infections with wild-type Shigella . Moreover, the Shigella phoP mutant was more sensitive than the wild-type strain to killing by polymorphonuclear leucocytes (PMNs), cationic polypeptides extracted from PMNs and other animal-derived antimicrobial peptides . The phoP mutant, however, invaded epithelial cells, spread intercellularly, induced apoptosis in macrophages and tolerated extreme acid pH as efficiently as the wild-type strain . PhoP appears to regulate Shigella susceptibility to PMNs and antimicrobial molecules that are important for the late stages of infection with this enteric bacterium.

Cell Microbiol, 2000 Aug, 2(4), 293 - 303
The secreted effector protein of Salmonella dublin, SopA, is translocated into eukaryotic cells and influences the induction of enteritis; Wood MW et al.; Salmonella-induced enteritis is associated with the induction of an acute intestinal inflammatory response and net fluid secretion into the lumen of infected mucosa . Proteins secreted by the Inv/Spa type III secretion system of Salmonella play a key role in the induction of these responses . We have demonstrated recently that the Inv/Spa-secreted SopB and SopD effector proteins are translocated into eukaryotic cells via a Sip-dependent pathway and act in concert to mediate inflammation and fluid secretion in infected ileal mucosa . Mutations of both sopB and sopD significantly reduced, but did not abrogate, the enteropathogenic phenotype . This indicated that other virulence factors are involved in the induction of enteritis . In this work, we characterize SopA, a secreted protein belonging to the family of Sop effectors of Salmonella dublin . We demonstrate that SopA is translocated into eukaryotic cells and provide evidence suggesting that SopA has a role in the induction of enteritis.

Cell Microbiol, 2000 Aug, 2(4), 265 - 73
Pathogen-induced apoptosis of macrophages: a common end for different pathogenic strategies; Navarre WW et al.; Microbe-macrophage interactions play a central role in the pathogenesis of many infections . Several bacterial pathogens induce apoptosis specifically in macrophages, but the mechanisms by which it occurs differ, and the resulting pathology can take different courses . Macrophage death caused by Shigella flexneri and Salmonella spp . has been shown to result in the release of pro-inflammatory cytokines . Conversely, Yersinia spp . induce apoptosis by suppressing the signalling pathways that lead to the production of tumour necrosis factor (TNF)-alpha, a cytokine essential for the control of this infection . It is likely that there are a variety of reasons why macrophages are particularly susceptible to pathogen-induced apoptosis . One reason may be the expression of surface receptors that recognize highly conserved bacterial components, such as lipopolysaccharide (LPS) and bacterial lipoproteins (BLPs) . These receptors have recently been shown to activate pro-apoptotic signalling pathways . The roles of macrophage apoptosis in different disease processes are discussed.

Cell Microbiol, 2000 Apr, 2(2), 83 - 9
Cross-talk between enteric pathogens and the intestine; Uzzau S et al.; Enteric pathogens finely regulate the expression of virulence genes in reply to stimuli generated by the intestinal environment . This minireview focuses on recently discovered strategies developed by enteric bacteria to cause intestinal secretion through the elaboration of factors that share structure and function with specific host counterparts . Such bacterial antigens appear to interfere largely with the epithelial cell signalling that physiologically regulates the numerous and, as yet not fully elucidated, mechanisms controlling both the transcellular and the paracellular secretion pathways . Heat-stable enterotoxins (STs) elaborated by enterotoxigenic Escherichia coli and the enteroaggregative E . coli enterotoxin (EAST1) are both typical examples of enteric toxins that activate the transcellular secretion pathway by mimicking guanylin, the endogenous modulator of cGMP signalling . Alternative strategies have been developed by Salmonella to induce intestinal secretion through the elaboration of a factor (SopB) that resembles at least two of the host cell 4-phosphatases, enzymes that activate the Ca-dependent transcellular secretion pathway . Finally, Vibrio cholerae has developed innovative tactics to activate the paracellular secretion pathway through the elaboration of Zonula occludens toxin (Zot), a factor that mimics a recently described physiological modulator of intercellular tight junctions.

Cell Microbiol, 2000 Feb, 2(1), 49 - 58
The Salmonella virulence plasmid spv genes are required for cytopathology in human monocyte-derived macrophages; Libby SJ et al.; The pathogenesis of serious systemic Salmonella infections is characterized by survival and proliferation of bacteria inside macrophages . Infection of human monocyte-derived macrophages in vitro with S . typhimurium or S . dublin produces cytopathology characterized by detachment of cells that contain large numbers of proliferating bacteria . This cytopathology is dependent on the expression of the bacterial spv genes, a virulence locus previously shown to markedly enhance the ability of Salmonella to produce systemic disease . After 24 h of infection, macrophage cultures contain two populations of bacteria: (i) proliferating organisms present in a detached cell fraction; and (ii) a static bacterial population in macrophages remaining attached to the culture well . Mutations in either the essential transcriptional activator SpvR or the key SpvB protein markedly reduce the cytopathic effect of Salmonella infection . The spv-dependent cytopathology in macrophages exhibits characteristics of apoptosis, with release of nucleosomes into the cytoplasm, nuclear condensation and DNA fragmentation . The current findings suggest that the mechanism of the spv effect is through induction of increased cytopathology in host macrophages.

Cell Microbiol, 1999 Sep, 1(2), 143 - 55
Inhibition of Shigella flexneri-induced transepithelial migration of polymorphonuclear leucocytes by cadaverine; McCormick BA et al.; Dysentery caused by Shigella species is characterized by infiltration of polymorphonuclear leucocytes (PMNs) into the colonic mucosa . Shigella spp . evolved into pathogens by the acquisition of virulence genes and by the deletion of 'antivirulence' genes detrimental to its pathogenic lifestyle . An example is cadA (encoding lysine decarboxylase), which is uniformly absent in Shigella spp., whereas it is present in nearly all isolates of the closely related non-pathogen Escherichia coli . Here, using monolayers of T84 cells to model the human intestinal epithelium, we determined that the introduction of cadA into S . flexneri and the expression of lysine decarboxylase attenuated the bacteria's ability to induce PMN influx across model intestinal epithelium . Such inhibition was caused by cadaverine generated from the decarboxylation of lysine . Cadaverine treatment of model intestinal epithelia specifically inhibited S . flexneri induction of PMN transepithelial migration, while having no effect on the ability of Salmonella or enteropathogenic E . coli (EPEC) to induce PMN migration . These observations not only provide insight into mechanisms of S . flexneri pathogen evolution and pathogenesis, but also suggest a potential for the use of cadaverine in the treatment of dysentery.

Antimicrob Agents Chemother, 2001 Mar, 45(3), 956 - 8
Antibiotic susceptibilities of Salmonella enterica serovar Typhi and S . enterica serovar Paratyphi A isolated from patients in Japan; Hirose K et al.; The antibiotic susceptibilities of 62 strains of Salmonella enterica serovar Typhi and 37 strains of S . enterica serovar Paratyphi A were investigated with 18 antibiotics . Eighteen S . enterica serovar Typhi isolates and five S . enterica serovar Paratyphi A isolates were resistant to one or more antimicrobial agents, among which 10 S . enterica serovar Typhi isolates were nalidixic acid resistant and also showed decreased ciprofloxacin susceptibility.

J Infect Dis, 2001 Mar 1, 183(5), 753 - 61 Epub 2001 Feb 08.
The changing epidemiology of salmonella: trends in serotypes isolated from humans in the United States, 1987-1997; Olsen SJ et al.; Salmonellosis is a major cause of illness in the United States . To highlight recent trends, data for 1987-1997 from the National Salmonella Surveillance System were analyzed . A total of 441,863 Salmonella isolates were reported, with the highest age-specific rate among infants (159/100,000 infants at 2 months) . Annual isolation rates decreased from 19 to 13/100,000 persons; however, trends varied by serotype . The isolation rate of Salmonella serotype Enteritidis increased until 1996, whereas declines were noted in Salmonella serotypes Hadar and Heidelberg . Overall, serotypes that increased in frequency were significantly more likely than those that decreased to be associated with reptiles (P=.008) . Salmonella infections continue to be an important cause of illness, especially among infants . Recent declines in food-associated serotypes may reflect changes in the meat, poultry, and egg industries that preceded or anticipated the 1996 implementation of pathogen-reduction programs . Additional educational efforts are needed to control the emergence of reptile-associated salmonellosis.

Phytother Res, 2001 Feb, 15(1), 73 - 5
Phytochemical and antimicrobial properties of constituents of "Ogwu Odenigbo", a popular Nigerian herbal medicine for typhoid fever; Ebi GC et al.; The ethylacetate-insoluble fraction of the methanol extract of "Ogwu Odenigbo" a popular Nigerian traditional herbal medicine for typhoid fever prepared from the stem bark of Cleistropholis patens Benth, (Annonaceae), was separated into 13 semi-characterized constituents by preparatory TLC . The in vitro antimicrobial activities of the 13 fractions were quantitatively and/or qualitatively assessed by the agar well diffusion method using Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Salmonella typhinium, Aspergillus niger and Candida albicans . The steroidal fraction was about 20 and 15 times more potent than penicillin and chloramphenicol respectively against B . subtilis, and about twice as active as penicillin G . or chloramphenicol against Klebsiella pneumoniae . The glycoside fractions 4/5, 6, 7 and the alkaloidal fraction 11 showed significant activity comparable to those of the controls against Klebsiella pneumoniae . The saponin fraction 1 was the only fraction active against Salmonella typhinium . Its activity was comparable to that of the controls against this organism .

J Appl Toxicol, 2000 Nov-Dec, 20(6), 491 - 7
Di(isononyl) phthalate (DINP) and di(isodecyl) phthalate (DIDP) are not mutagenic; McKee RH et al.; Recently there have been reports of liver and kidney tumors in rodents following long-term exposure to di(isononyl) phthalate (DINP) . Mechanistic studies suggested that the liver tumors were a consequence of peroxisomal proliferation, whereas the kidney tumors (found only in male rats) were associated with induction of alpha(2u)-globulin . Because both peroxisomal proliferation and alpha(2u)-globulin are considered to be non-genotoxic carcinogenic processes, it seemed appropriate to investigate the genotoxic potential of DINP . Additional studies were also conducted on di(isodecyl) phthalate (DIDP), a structurally related substance that also induces peroxisomal proliferation, although it has not been tested in a carcinogenicity bioassay . The DINP was tested in Salmonella, in vitro cytogenetics and mouse micronucleus assays, whereas DIDP was evaluated in a mouse micronucleus test . All of these tests produced negative results, i.e . neither phthalate was mutagenic in any of the test systems . These data are consistent with results of other published and unpublished genotoxicity tests and provide support for the hypothesis that the liver and kidney tumors induced by DINP were the result of non-genotoxic processes .

Infect Immun, 2001 Mar, 69(3), 1714 - 21
Adoptive transfer of CD4+ T cells specific for subunit A of Helicobacter pylori urease reduces H . pylori stomach colonization in mice in the absence of interleukin-4 (IL-4)/IL-13 receptor signaling; Lucas B et al.; Protection in the murine model of Helicobacter pylori infection may be mediated by CD4+ T cells, but the mechanism remains unclear . To better understand how protection occurs in this model, we generated and characterized H . pylori urease-specific CD4+ T cells from BALB/c mice immunized with Salmonella enterica serovar Typhimurium expressing H . pylori urease (subunits A and B) . The CD4+ T cells were found to be specific for subunit A (UreA) . Upon antigen-specific stimulation, expression of interleukin 4 (IL-4), IL-10, gamma interferon (IFN-gamma), and tumor necrosis factor alpha was induced . Immunocytochemical analysis showed that the majority of cells produced IFN-gamma and IL-10 . Adoptive transfer of the UreA-specific CD4+ T cells into naive syngeneic recipients led to a threefold reduction in the number of bacteria in the recipient group when compared to that in the nonrecipient group . Stomach colonization was also reduced significantly after transfer of these cells into patently infected mice . Adoptive transfer of UreA-specific CD4+ T cells into IL-4 receptor alpha chain-deficient BALB/c mice indicated that IL-4 and IL-13 were not critical in the control of bacterial load . In addition, synthetic peptides were used to identify three functional T-cell epitopes present in subunit A which were recognized by the UreA-specific T cells . Analysis of H . pylori-specific cellular immune responses in recipient challenged and nonrecipient infected mice indicated a strong local restriction of the response in infected animals . The implications of these findings for the mechanism of protection and the development of peptide-based vaccination are discussed.

Infect Immun, 2001 Mar, 69(3), 1587 - 92
Rat mannose-binding protein a binds CD14; Chiba H et al.; Lipopolysaccharide (LPS) has been known to induce inflammation by interacting with CD14, which serves as a receptor for LPS . Mannose-binding protein (MBP) belongs to the collectin subgroup of the C-type lectin superfamily, along with surfactant proteins SP-A and SP-D . We have recently demonstrated that SP-A modulates LPS-induced cellular responses by interaction with CD14 (H . Sano, H . Sohma, T . Muta, S . Nomura, D . R . Voelker, and Y . Kuroki, J . Immunol . 163:387-395, 2000) and that SP-D also interacts with CD14 (H . Sano, H . Chiba, D . Iwaki, H . Sohma, D . R . Voelker, and Y . Kuroki, J . Biol . Chem . 275:22442-22451, 2000) . In this study, we examined whether MBP, a collectin highly homologous to SP-A and SP-D, could bind CD14 . Recombinant rat MBP-A bound recombinant human soluble CD14 in a concentration-dependent manner . Its binding was not inhibited in the presence of excess mannose or EDTA . MBP-A bound deglycosylated CD14 treated with N-glycosidase F, neuraminidase, and O-glycosidase, indicating that MBP-A interacts with the peptide portion of CD14 . Since LPS was also a ligand for the collectins, we compared the characteristics of binding of MBP-A to LPS with those of binding to CD14 . MBP-A bound to lipid A from Salmonella enterica serovar Minnesota and rough LPS (S . enterica serovar Minnesota Re595 and Escherichia coli J5, Rc), but not to smooth LPS (E . coli O26:B6 and O111:B4) . Unlike CD14 binding, EDTA and excess mannose attenuated the binding of MBP-A to rough LPS . From these results, we conclude that CD14 is a novel ligand for MBP-A and that MBP-A utilizes a different mechanism for CD14 recognition from that for LPS.

Infect Immun, 2001 Mar, 69(3), 1581 - 6
Staphylococcus aureus and Salmonella enterica serovar Dublin induce tumor necrosis factor-related apoptosis-inducing ligand expression by normal mouse and human osteoblasts; Alexander EH et al.; Staphylococcus aureus and Salmonella enterica serovar Dublin invade osteoblasts and are causative agents of human bone disease . In the present study, we examined the ability of S . aureus and Salmonella serovar Dublin to induce the production of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) by normal osteoblasts . Normal mouse and human osteoblasts were cocultured with S . aureus or Salmonella serovar Dublin at different multiplicities of infection . Following initial incubation and examination of TRAIL expression, extracellular bacteria were killed by the addition of media containing the antibiotic gentamicin . Lysates and conditioned media from osteoblast cultures were then collected at various times following invasion and analyzed . The results demonstrated that S . aureus and Salmonella serovar Dublin are potent inducers of TRAIL expression by osteoblasts . Mouse and human TRAIL mRNA expression was induced by bacterial infection and demonstrated a dose-dependent response . Analysis of kinetics suggested that TRAIL mRNA was induced within 30 min after exposure to bacteria and that its level of expression remained relatively constant over the time period examined . mRNA molecules encoding TRAIL receptors were constitutively expressed by osteoblasts . Furthermore, TRAIL protein was detected as early as 45 min and up to 24 h following infection . The quantity of TRAIL protein produced also increased in a dose-dependent manner . Collectively, these findings suggest a mechanism whereby bacterial pathogens mediate bone destruction via osteoblast apoptosis.

Infect Immun, 2001 Mar, 69(3), 1244 - 55
Molecular characterization of Streptococcus pneumoniae type 4, 6B, 8, and 18C capsular polysaccharide gene clusters; Jiang SM et al.; Capsular polysaccharide (CPS) is a major virulence factor in Streptococcus pneumoniae . CPS gene clusters of S . pneumoniae types 4, 6B, 8, and 18C were sequenced and compared with those of CPS types 1, 2, 14, 19F, 19A, 23F, and 33F . All have the same four genes at the 5' end, encoding proteins thought to be involved in regulation and export . Sequences of these genes can be divided into two classes, and evidence of recombination between them was observed . Next is the gene encoding the transferase for the first step in the synthesis of CPS . The predicted amino acid sequences of these first sugar transferases have multiple transmembrane segments, a feature lacking in other transferases . Sugar pathway genes are located at the 3' end of the gene cluster . Comparison of the four dTDP-L-rhamnose pathway genes (rml genes) of CPS types 1, 2, 6B, 18C, 19F, 19A, and 23F shows that they have the same gene order and are highly conserved . There is a gradient in the nature of the variation of rml genes, the average pairwise difference for those close to the central region being higher than that for those close to the end of the gene cluster and, again, recombination sites can be observed in these genes . This is similar to the situation we observed for rml genes of O-antigen gene clusters of Salmonella enterica . Our data indicate that the conserved first four genes at the 5' ends and the relatively conserved rml genes at the 3' ends of the CPS gene clusters were sites for recombination events involved in forming new forms of CPS . We have also identified wzx and wzy genes for all sequenced CPS gene clusters by use of motifs.

Trends Microbiol, 2001 Feb, 9(2), 64 - 7
Salmonella-induced cell death: apoptosis, necrosis or programmed cell death?
Boise LH, Collins CM.
Over the past several years, it has become apparent that enteropathogens activate cell death programs . For Salmonella and Shigella species, the induction of cell death is required for pathogenesis, and the mechanisms by which these bacteria induce cell death is an area of intense investigation . Although initial studies suggested that Salmonella induce cell death through an apoptotic pathway, recent studies demonstrate that cell death occurs through a unique caspase 1-dependent mechanism.

N Engl J Med, 2001 Jan 18, 344(3), 189 - 95
Use of molecular subtyping in surveillance for Salmonella enterica serotype typhimurium; Bender JB et al.; BACKGROUND: Because Salmonella enterica serotype typhimurium is the most common serotype isolated from persons with salmonellosis in the United States, it is difficult to detect unusual clusters or outbreaks . To determine whether molecular subtyping could be useful in public health surveillance for S . enterica serotype typhimurium, the Minnesota Department of Health initiated the routine use of pulsed-field gel electrophoresis (PFGE) of isolates . METHODS: Beginning in 1994, all S . enterica serotype typhimurium isolates submitted by clinical laboratories to the Department of Health were subtyped by PFGE . A standard questionnaire was used to interview patients about possible sources of infection . RESULTS: From 1994 through 1998, 998 cases of infection with S . enterica serotype typhimurium were reported to the Minnesota Department of Health (4.4 cases per 100,000 person-years) . PFGE was performed on 958 of the isolates (96 percent), and 174 different patterns were identified . Sixteen outbreaks with a common source were identified, accounting for 154 cases . PFGE subtyping made it possible to confirm 10 outbreaks that involved small numbers of cases in institutional settings . Of six larger, community-based outbreaks, four would probably not have been recognized without PFGE subtyping . These four outbreaks accounted for 96 of the 154 culture-confirmed outbreak cases (62 percent) . Fifty-six of 209 isolates tested for antimicrobial susceptibility (27 percent) were resistant to at least five antimicrobial agents . The multidrug-resistant isolates identified had unique PFGE patterns . CONCLUSIONS: Routine molecular subtyping of S . enterica serotype typhimurium by PFGE can improve the detection of outbreaks and aid in the identification of multidrug-resistant strains . Combining routine molecular subtyping with a method of rapid communication among public health authorities can improve surveillance for S . enterica serotype typhimurium infections.

Clin Infect Dis, 2001 Jan 15, 32(2), 263 - 9 Epub 2001 Jan 15.
Nontyphoidal salmonellosis; Hohmann EL; Nontyphoidal Salmonella are important foodborne pathogens that cause gastroenteritis, bacteremia, and subsequent focal infection . These hardy bacteria are especially problematic in a wide variety of immunocompromised individuals, including (but not limited to) patients with malignancy, human immunodeficiency virus, or diabetes, and those receiving corticosteroid therapy or treatment with other immunotherapy agents . Endovascular infection and deep bone or visceral abscesses are important complications that may be difficult to treat . The site of infection and the individual's immune status influence treatment choices . The harbingers of resistance of nontyphoidal Salmonella to both fluoroquinolones and third-generation cephalosporins have been reported recently, and such resistance is likely to be a therapeutic problem in the future . The current report presents a brief overview of the problems and trends associated with salmonellosis that are of interest to the infectious diseases clinician.

Mol Microbiol, 2001 Feb, 39(3), 606 - 19
Actin is ADP-ribosylated by the Salmonella enterica virulence-associated protein SpvB; Tezcan-Merdol D et al.; The Salmonella enterica virulence-associated protein SpvB was recently shown to contain a carboxy-terminal mono(ADP-ribosyl)transferase domain . We demonstrate here that the catalytic domain of SpvB as well bacterial extracts containing full-length SpvB modifies a 43 kDa protein from macrophage-like J774-A.1 and epithelial MDCK cells as shown by label transfer from {32P}-nicotinamide adenine dinucleotide (NAD) to the 43 kDa protein . When analysed by two-dimensional gel electrophoresis, the same protein was modified in cells infected with S . enterica serovariant Dublin strain SH9325, whereas infection with an isogenic spvB mutant strain did not result in modification . Immunoprecipitation and immunoblotting experiments using SH9325-infected cells identified the modified protein as actin . The isolated catalytic domain of SpvB mediated transfer of 32P from {32P}-NAD to actins from various sources in vitro, whereas isolated eukaryotic control proteins or bacterial proteins were not modified . In an in vitro actin polymerization assay, the isolated catalytic SpvB domain prevented the conversion of G actin into F actin . Microscopic examination of MDCK cells infected with SH9325 revealed morphological changes and loss of filamentous actin content, whereas cells infected with the spvB mutant remained virtually unaffected . We conclude that actin is a target for an SpvB-mediated modification, most probably ADP-ribosylation, and that the modification of G actin interferes with actin polymerization.

Lett Appl Microbiol, 2001 Jan, 32(1), 7 - 11
Detection of Salmonella and simultaneous detection of Salmonella and Shiga-like toxin-producing Escherichia coli using the magnetic capture hybridization polymerase chain reaction; Chen J et al.; The magnetic capture hybridization polymerase chain reaction (MCH-PCR) was used to detect Salmonella and also to simultaneously detect Salmonella and Shiga-like toxin-producing Escherichia coli (SLTEC) . Fifty-seven Salmonella and 41 SLTEC were included in the study . Salmonella were detected either individually by a single MCH-PCR assay targeting the inv gene or simultaneously with SLTEC by a multiplex MCH-PCR in which SLTEC were detected using primers for the slt genes . Both single and multiplex assays were found to be specific for tested pathogens . The results indicate that MCH-PCR can be used as means of detecting single or multiple bacterial pathogen(s).

Clin Microbiol Infect, 2000 Oct, 6(10), 536 - 42
Outbreak of Salmonella braenderup gastroenteritis due to contaminated meat pies: clinical and molecular epidemiology; Urfer E et al.; OBJECTIVES: To determine the epidemiologic, clinical and molecular characteristics of an outbreak of severe gastroenteritis due to the ingestion of meat pies highly contaminated with Salmonella braenderup . METHODS: In October 1993, we observed an outbreak of Salmonella braenderup gastroenteritis that occurred in the Lausanne area, Canton de Vaud, Switzerland . Cultures of suspected food products, of samples at the incriminated food factory and from workers, as well as a case-control study, were used to determine the source of the epidemics . Ribotyping of representative Salmonella braenderup strains was performed to define the molecular epidemiology . The clinical characteristics of this infection were determined by using a standardized interview performed during and 6 months after the outbreak in 156 of 215 identified patients . RESULTS: The outbreak resulted from the ingestion of pies, heavily contaminated (> 106 CFU/g) with a strain of Salmonella braenderup . The contamination was due to mishandling and recycling of jelly poured on top of the products . According to its ribotype and plasmid characteristics, this strain had not been isolated previously in Switzerland . Ten of the 24 workers of the incriminated food factory were shedding the epidemic strain in their stools, and one of them reported gastroenteritis 3 weeks before the beginning of the outbreak . The estimated attack rate in the exposed population was 7.5% . The median incubation time was 18 h . Among 127 adult patients studied, 98% had diarrhea, 95% abdominal pain, 74% fever > or = 38.5 degrees C, 69% nausea and 35% vomiting . One patient developed prosthetic valve endocarditis, and one reactive arthritis . Long-term complications were not identified, although 12 patients complained of irritable bowel syndrome and 24 of unusual asthenia lasting for more than 6 weeks after infection . Children had more severe signs and symptoms compared to adults, and six of 29 needed hospitalization . CONCLUSIONS: This study showed that ingestion of food highly contaminated with Salmonella braenderup resulted in severe but typical gastroenteritis and indicated mishandling of food during manufacture as the cause of this outbreak.

J Ethnopharmacol, 2001 Feb, 74(2), 149 - 57
Toxicological evaluation of a tea from leaves of Vernonia condensata; Monteiro MH et al.; Teas of Vernonia condensata Baker (Asteraceae) are widely used in Brazil for gastro-intestinal disorders and to treat several other diseases . In this study, we evaluated the acute toxicity, embryotoxicity and mutagenicity of a lyophilized aqueous extract (LAE) from V . condensata leaves . Single doses of LAE, up to 5000 mg/kg body weight, were given orally or intraperitoneally to male and female Swiss albino mice . No toxicity was observed after oral administration . The "Approximate Lethal Dose" after intraperitoneal injections was 3400 mg/kg for males and 5000 mg/kg for females . Embryotoxicity was investigated in Han:NMRI mice . LAE (0, 500 and 2000 mg/kg/day) was given by gavage on days 10, 11 and 12, and dams were submitted to caesarean sections on day 18 of pregnancy . Fetuses were weighed, examined for externally visible malformations, and evaluated for skeletal anomalies . Except for a slight reduction of fetal body weight accompanied by signs of delayed ossification at the highest dose, no other embryotoxic effect was noted in the exposed offspring . LAE-induced mutagenicity was evaluated in the Salmonella/microsome assay without and with S9 mixture . LAE, tested up to 5000 microg/plate, was not mutagenic to tester strains TA97a, TA98 and TA100 . Results therefore suggest that V . condensata aqueous extracts present low acute toxicity and pose neither teratogenic nor mutagenic risks.

J Ethnopharmacol, 2001 Feb, 74(2), 113 - 23
Antimicrobial and phytochemical studies on 45 Indian medicinal plants against multi-drug resistant human pathogens; Ahmad I et al.; Ethanolic extracts of 45 Indian medicinal plants traditionally used in medicine were studied for their antimicrobial activity against certain drug-resistant bacteria and a yeast Candida albicans of clinical origin . Of these, 40 plant extracts showed varied levels of antimicrobial activity against one or more test bacteria . Anticandidal activity was detected in 24 plant extracts . Overall, broad-spectrum antimicrobial activity was observed in 12 plants (L . inermis, Eucalyptus sp., H . antidysentrica, H . indicus, C . equistifolia . T . belerica, T . chebula, E . officinalis, C . sinensis, S . aromaticum and P . granatum) . No correlation was observed between susceptibility of test strains with plant extracts and antibiotic resistance behaviour of the microbial strains (Staphylococcus aureus, Salmonella paratyphi, Shigella dysenteriae, Escherichia coli, Bacillus subtilis, Candida albicans) . Qualitative phytochemical tests, thin layer chromatography and TLC-bioautography of certain active extracts demonstrated the presence of common phytocompounds in the plant extracts including phenols, tannins and flavonoids as major active constituents.

FEMS Microbiol Lett, 2001 Feb 5, 195(1), 73 - 8
Egg contamination by Salmonella serovar enteritidis following vaccination with Delta-aroA Salmonella serovar typhimurium; Parker C et al.; The efficacy of an aroA Salmonella serovar typhimurium modified live vaccine to decrease internal egg contamination after oral challenge of hens with egg-contaminating Salmonella serovar enteritidis was assessed . Challenge was with a mixed phenotype of S . enteritidis that had virulence characteristics previously associated with enhanced oral invasiveness and egg contamination in chickens . Immunized birds had fewer positive ovary/oviduct pools and lower cfu g(-1) cecal contents than did non-immunized birds, but the differences were not significant . The number of positive intestinal (duodenum, jejunum, ileum) and organ (spleen, kidney, liver) pools following challenge from each treatment group were equivalent . Most importantly, immunization did not decrease egg contamination . These results suggest that the ability of modified live vaccines to reduce internal egg contamination by S . serovar enteritidis can be assessed using characterized strains for challenge.

Vaccine, 2001 Feb 8, 19(13-14), 1694 - 700
Novel use of anaerobically induced promoter, dmsA, for controlled expression of fragment C of tetanus toxin in live attenuated Salmonella enterica serovar Typhi strain CVD 908-htrA; Orr N et al.; The anaerobically induced promoter dmsA (PdmsA) was adapted to optimize in vivo expression of foreign antigens in attenuated Salmonella enterica serovar Typhi live vector vaccines CVD 908-htrA . PdmsA from Escherichia coli and two derivatives, PdmsA2 and PdmsA3 were cloned into a plasmid driving the expression of a gene encoding tetanus toxin fragment C . Expression of fragment C varied from a low level induced by pTETdmsA, to moderate and high levels induced, respectively, by pTETdmsA2 and pTETdmsA3 . Mice were immunized intranasally with CVD 908-htrA harboring pTETdmsA2 or pTETdmsA3, and the serum antitoxin response was compared to that elicited by CVD 908-htrA(pTETnir15) (Pnir15 is a benchmark anaerobically activated promoter) . S . Typhi carrying pTETdmsA2 elicited modest tetanus antitoxin titers while S . Typhi harboring pTETdmsA3 generated elevated titers (GMT=55384) that were higher than elicited by pTETnir15 (GMT=4354) (P=0.007) . Mice immunized with CVD 908-htrA carrying pTETdmsA3 and pTETnir15 survived tetanus toxin challenge . P(dmsA) derivatives are attractive promoters for in vivo expression of foreign genes in attenuated live vector vaccines.

Trends Microbiol, 2001 Jan, 9(1), 29 - 33
Oxygen-dependent anti-Salmonella activity of macrophages; Vazquez-Torres A et al.; Numerous observations have established a crucial role for phagocytic cells in host resistance to Salmonella . Activated macrophages rely on a complex array of oxygen-dependent antimicrobial molecules to inhibit or kill intracellular Salmonella . An initial oxidative bactericidal phase, which is dependent on the respiratory burst phagocyte oxidase (phox) is succeeded by a prolonged nitrosative bacteriostatic phase, which is dependent on inducible nitric oxide synthase (iNOS) . The sequential contribution of phox and iNOS to anti-Salmonella innate immunity has been demonstrated both in vitro and in vivo . The temporal progression from the predominant production of reactive oxygen species to the production of nitrogen oxides could optimize the initial reduction in microbial burden while minimizing the immunopathological consequences of the host inflammatory response.

Trends Microbiol, 2001 Jan, 9(1), 2 - 4; discussion 4-5
The best defense is a good offense--Salmonella deploys an ADP-ribosylating toxin; Lesnick ML et al.; The dramatic clinical manifestations of toxigenic infections such as cholera and diphtheria occur without substantial bacterial invasion . Disease is mediated by the secretion of potent toxins that use ADP-ribosylation as the catalytic mechanism underlying their action . ADP-ribosylating toxins comprise a large family, including the cholera, diphtheria, pertussis and Escherichia coli heat-labile (LT) toxins, and all produce disease by altering key metabolic processes after transfer of an ADP-ribose moiety from NAD to specific host-cell target proteins . A new paradigm implicating ADP-ribosylation during intracellular pathogenesis is beginning to emerge from recent research in Salmonella.

Vet Microbiol, 2001 Feb 12, 78(3), 205 - 19
Herd level husbandry factors associated with the serological Salmonella prevalence in finishing pig herds in The Netherlands; van der Wolf PJ et al.; A national program to reduce Salmonella in pork and pork products should include monitoring and intervention at farm level . To develop an adequate intervention strategy at farm level, risk factors for Salmonella infections in finishing pigs have to be determined . In this study, blood samples were collected randomly at two slaughterhouses from slaughter pigs . Samples were tested by the Dutch Salmonella ELISA, based on the O-antigens 1, 4, 5, 6, 7 and 12, using a cut-off of OD%=10 . This ELISA has been calibrated against the Danish ELISA to give comparable results . Workers from herds from which at least forty blood samples had been collected, were asked to participate in a questionnaire . In total, 353 questionnaires were obtained and analysed . Significant risk factors associated with the proportion of seropositive samples were identified by multiple linear logistic regression . The feeding of a complete liquid feed containing fermented by-products and the omission of disinfection after pressure washing a compartment as part of an all-in/all-out procedure, were both associated with a lower Salmonella seroprevalence . A small to moderate herd size (<800 finishing pigs), a previous diagnosis of clinical Salmonella infection in the herd, the use of tylosin as an antimicrobial growth promoter in finishing feed, or herds which had more than 16% of the livers of their pigs condemned at the slaughterhouse as a result of white spots were associated with a higher Salmonella seroprevalence . Hypothetical intervention strategies based on these risk factors can be studied for their effect on the Salmonella seroprevalence and practical applicability in field studies.

Mol Cell, 2000 Dec, 6(6), 1449 - 60
Modulation of host signaling by a bacterial mimic: structure of the Salmonella effector SptP bound to Rac1; Stebbins CE et al.; Salmonella spp . utilize a specialized protein secretion system to deliver a battery of effector proteins into host cells . Several of these effectors stimulate Cdc42- and Rac1-dependent cytoskeletal changes that promote bacterial internalization . These potentially cytotoxic alterations are rapidly reversed by the effector SptP, a tyrosine phosphatase and GTPase activating protein (GAP) that targets Cdc42 and Rac1 . The 2.3 A resolution crystal structure of an SptP-Rac1 transition state complex reveals an unusual GAP architecture that mimics host functional homologs . The phosphatase domain possesses a conserved active site but distinct surface properties . Binding to Rac1 induces a dramatic stabilization in SptP of a four-helix bundle that makes extensive contacts with the Switch I and Switch II regions of the GTPase.

Microb Pathog, 2001 Feb, 30(2), 81 - 90
A flagellar gene fliZ regulates the expression of invasion genes and virulence phenotype in Salmonella enterica serovar Typhimurium; Iyoda S et al.; We previously reported that the fliZ gene encodes a positive regulatory factor for the class 2 flagellar operons in Salmonella enterica serovar Typhimurium . In this study, we found that the fliZ mutation reduced not only the amounts of excreted flagellar proteins, but also those of several secreted invasion proteins encoded by the genes within Salmonella pathogenicity island 1 . Using the lacZ gene fused to a subset of virulence-associated genes, we show that this downregulation was caused by a decreased transcription of the hilA gene, which encodes a positive regulator for the invasion genes . We further show that the fliZ mutation reduced invasion ability of S . enterica serovar Typhimurium to HEp-2 cells . Consistent with these results, orally challenged cells of the fliZ mutant show an attenuated virulence phenotype in a mouse typhoid model . These results indicate that the fliZ gene product positively regulates the invasion genes and is necessary for expression of full virulence .

Annu Rev Med, 2001, 52, 259 - 74
Salmonella: a model for bacterial pathogenesis; Ohl ME et al.; Salmonellae are gram-negative bacteria that cause gastroenteritis and enteric fever . Salmonella virulence requires the coordinated expression of complex arrays of virulence factors that allow the bacterium to evade the host's immune system . All Salmonella serotypes share the ability to invade the host by inducing their own uptake into cells of the intestinal epithelium . In addition, Salmonella serotypes associated with gastroenteritis orchestrate an intestinal inflammatory and secretory response, whereas serotypes that cause enteric fever establish systemic infection through their ability to survive and replicate in mononuclear phagocytes . This review explores the molecular basis of selected Salmonella virulence strategies, with an emphasis on general themes of bacterial pathogenesis as exemplified by Salmonella.

J Immunol, 2001 Feb 1, 166(3), 1823 - 31
Yersinia outer protein P of Yersinia enterocolitica simultaneously blocks the nuclear factor-kappa B pathway and exploits lipopolysaccharide signaling to trigger apoptosis in macrophages; Ruckdeschel K et al.; Exposure of macrophages to bacteria or LPS mediates activation of signaling pathways that induce expression of self defense-related genes . Pathogenic YERSINIA: species impair activation of transcription factor NF-kappaB and trigger apoptosis in macrophages . In this study, we dissected the mechanism of apoptosis induction by YERSINIA: Selectively, YERSINIA: enterocolitica strains producing the effector protein YERSINIA: outer protein P (YopP) hampered NF-kappaB activation and subsequently conferred apoptosis to J774A.1 macrophages . Thereby, YopP bound and inhibited the macrophage NF-kappaB-activating kinase IKKbeta . YopP- and Yersinia-, but not SALMONELLA:-induced apoptosis was specifically prevented by transient overexpression of NF-kappaB p65, giving evidence that YopP mediates cell death by disrupting the NF-kappaB signaling pathway . Transfection of J774A.1 macrophages with YopP induced a moderate, but significant degree of apoptosis (40-50% of transfected cells) . This effect was strongly enhanced by additional initiation of LPS signaling (80-90%), indicating a synergism between LPS-induced signal transduction and inhibition of NF-kappaB by YopP . This reflects a strategy of a bacterial pathogen that takes advantage of LPS, serving as cofactor, to impair the macrophage.

J Bacteriol, 2001 Mar, 183(5), 1787 - 91
Characterization of the catalytic activities of the PhoQ histidine protein kinase of Salmonella enterica serovar Typhimurium; Montagne M et al.; Studies of Escherichia coli membranes that were highly enriched in the Salmonella enterica serovar Typhimurium PhoQ protein showed that the presence of ATP and divalent cations such as Mg2+, Mn2+, Ca2+, or Ba2+ resulted in PhoQ autophosphorylation . However, when Mg2) or Mn2+ was present at concentrations higher than 0.1 mM, the kinetics of PhoQ autophosphorylation were strongly biphasic, with a rapid autophosphorylation phase followed by a slower dephosphorylation phase . A fusion protein lacking the sensory and transmembrane domains retained the autokinase activity but could not be dephosphosphorylated when Mg2+ or Mn2+ was present at high concentrations . The instability of purified {32P}phospho-PhoP in the presence of PhoQ-containing membranes indicated that PhoQ also possesses a phosphatase activity . The PhoQ phosphatase activity was stimulated by increasing the Mg2+ concentration . These data are consistent with a model in which Mg2+ binding to the sensory domain of PhoQ coordinately regulates autokinase and phosphatase activities.

J Bacteriol, 2001 Mar, 183(5), 1784 - 6
The apeE gene of Salmonella enterica serovar Typhimurium is induced by phosphate limitation and regulated by phoBR; Conlin CA et al.; Mutations in apeR, a regulatory locus of the outer membrane esterase apeE from Salmonella enterica serovar Typhimurium, were shown to be alleles of the pstSCAB-phoU high-affinity phosphate transport operon . Expression of apeE was induced by phosphate limitation, and this induction required the phoBR phosphate regulatory system.

J Bacteriol, 2001 Mar, 183(5), 1655 - 62
Intergenic suppression between the flagellar MS ring protein FliF of Salmonella and FlhA, a membrane component of its export apparatus; Kihara M et al.; The MS ring of the flagellar basal body of Salmonella is an integral membrane structure consisting of about 26 subunits of a 61-kDa protein, FliF . Out of many nonflagellate fliF mutants tested, three gave rise to intergenic suppressors in flagellar region II . The pseudorevertants swarmed, though poorly; this partial recovery of motile function was shown to be due to partial recovery of export function and flagellar assembly . The three parental mutants were all found to carry the same mutation, a six-base deletion corresponding to loss of Ala-174 and Ser-175 in the predicted periplasmic domain of the FliF protein . The 19 intergenic suppressors identified all lay in flhA, and they consisted of 10 independent examples at the nucleotide level or 9 at the amino acid level . Since two of the nine corresponded to different substitutions at the same amino acid position, only eight positions in the FlhA protein have given rise to suppressors . Thus, FliF-FlhA intergenic suppression is a fairly rare event . FlhA is a component of the flagellar protein export apparatus, with an integral membrane domain encompassing the N-terminal half of the sequence and a cytoplasmic C-terminal domain . All of the suppressing mutations lay within the integral membrane domain . These mutations, when placed in a wild-type fliF background, had no mutant phenotype . In the fliF mutant background, mutant FlhA was dominant, yielding a pseudorevertant phenotype . Wild-type FlhA did not exert significant negative dominance in the pseudorevertant background, indicating that it does not compete effectively with mutant FlhA for interaction with mutant FliF . Mutant FliF was partially dominant over wild-type FliF in both the wild-type and second-site FlhA backgrounds . Membrane fractionation experiments indicated that the fliF mutation, though preventing export, was mild enough to permit assembly of the MS ring itself, and also assembly of the cytoplasmic C ring onto the MS ring . The data from this study provide genetic support for a model in which at least the FlhA component of the export apparatus physically interacts with the MS ring within which it is housed.

J Bacteriol, 2001 Mar, 183(5), 1577 - 84
Functional genomic, biochemical, and genetic characterization of the Salmonella pduO gene, an ATP:cob(I)alamin adenosyltransferase gene; Johnson CL et al.; Salmonella enterica degrades 1,2-propanediol by a pathway dependent on coenzyme B12 (adenosylcobalamin {AdoCb1}) . Previous studies showed that 1,2-propanediol utilization (pdu) genes include those for the conversion of inactive cobalamins, such as vitamin B12, to AdoCbl . However, the specific genes involved were not identified . Here we show that the pduO gene encodes a protein with ATP:cob(I)alamin adenosyltransferase activity . The main role of this protein is apparently the conversion of inactive cobalamins to AdoCbl for 1,2-propanediol degradation . Genetic tests showed that the function of the pduO gene was partially replaced by the cobA gene (a known ATP:corrinoid adenosyltransferase) but that optimal growth of S . enterica on 1,2-propanediol required a functional pduO gene . Growth studies showed that cobA pduO double mutants were unable to grow on 1,2-propanediol minimal medium supplemented with vitamin B(12) but were capable of growth on similar medium supplemented with AdoCbl . The pduO gene was cloned into a T7 expression vector . The PduO protein was overexpressed, partially purified, and, using an improved assay procedure, shown to have cob(I)alamin adenosyltransferase activity . Analysis of the genomic context of genes encoding PduO and related proteins indicated that particular adenosyltransferases tend to be specialized for particular AdoCbl-dependent enzymes or for the de novo synthesis of AdoCbl . Such analyses also indicated that PduO is a bifunctional enzyme . The possibility that genes of unknown function proximal to adenosyltransferase homologues represent previously unidentified AdoCbl-dependent enzymes is discussed.

Infect Immun, 2001 Feb, 69(2), 1226 - 9
Mice lacking interleukin-2 (IL-2)/IL-15 receptor beta chain are susceptible to infection with avirulent Salmonella enterica subsp . enterica serovar choleraesuis but mice lacking IL-2 are resistant; Nishimura H et al.; Interleukin-2 (IL-2)/IL-15 receptor beta (IL-15R beta)(-/-) mice were susceptible to infection with avirulent Salmonella enterica subsp . enterica serovar Choleraesuis, whereas IL-2(-/-) mice were resistant . A natural killer cell response was not evident for both types of deficient mice . A Th1 response was detected in IL-2(-/-) but not in IL-2/IL-15R beta(-/-) mice infected with Salmonella, suggesting that IL-2/IL-15R beta signaling is important for the generation of protective Th1 cells.

Infect Immun, 2001 Feb, 69(2), 1192 - 8
Expression, extracellular secretion, and immunogenicity of the Plasmodium falciparum sporozoite surface protein 2 in Salmonella vaccine strains; Gomez-Duarte OG et al.; Deleting transmembrane alpha-helix motifs from Plasmodium falciparum sporozoite surface protein (SSP-2) allowed its secretion from Salmonella enterica serovar Typhimurium SL3261 and S . enterica serovar Typhi CVD 908-htrA by the Hly type I secretion system . In mice immunized intranasally, serovar Typhimurium constructs secreting SSP-2 stimulated greater gamma interferon splenocyte responses than did nonsecreting constructs (P = 0.04).

Infect Immun, 2001 Feb, 69(2), 737 - 43
Salmonella pathogenicity island 2-encoded proteins SseC and SseD are essential for virulence and are substrates of the type III secretion system; Klein JR et al.; Survival of Salmonella enterica serovar Typhimurium within host phagocytic cells is a critical step in establishing systemic infection in mice . Genes within Salmonella pathogenicity island 2 (SPI-2) encode a type III secretion system that is required for establishment of systemic infection . Several proteins encoded by SPI-2 have homology to type III secreted proteins from enteropathogenic Escherichia coli and Yersinia and, based on that homology, are predicted to be secreted through the SPI-2 type III secretion system . We have investigated the roles of two of these proteins, SseC and SseD . We demonstrate here that the SseD protein is required for systemic Salmonella infection of the mouse, and we confirmed the virulence requirement for the SseC protein . Experiments were performed, using cellular fractionation and immunoblotting, to identify the subcellular location of the SseC and SseD proteins . Both proteins were found to localize predominantly to the bacterial cell membrane . In addition, our work revealed that SseC and SseD are exposed to the extracellular environment and are loosely associated with the bacterial membrane . Furthermore, localization of SseC and SseD to the bacterial membrane was found to require a functional SPI-2 type III secretion system . Collectively, these results indicate that the SseC and SseD proteins are secreted by the SPI-2 type III secretion system to the bacterial membrane in order to perform their virulence functions.

Proc Natl Acad Sci U S A, 2001 Jan 30, 98(3), 875 - 9 Epub 2001 Jan 16.
Overexpression of the inositol phosphatase SopB in human 293 cells stimulates cellular chloride influx and inhibits nuclear mRNA export; Feng Y et al.; SopB is an inositol phosphate phosphatase that is a virulence factor in Salmonella species . We have overexpressed SopB cDNA in a tetracycline-dependent system in human embryonic 293 cells, and used this model system to directly analyze the role of SopB in altering inositol metabolite levels in vivo . Addition of tetracycline to these cells resulted in the rapid induction of SopB expression, which was coincident with perturbations in the cellular levels of multiple soluble inositol phosphates . All of the changes induced by SopB expression were reversed within 24 h on removal of tetracycline from media . Specifically, cellular inositol 1,3,4,5,6-pentakisphosphate (InsP(5)) and inositol hexakisphosphate (InsP(6)) levels were depleted within 4 to 6 h after inducing SopB expression . A transient rise in cellular inositol 1,4,5,6-tetrakisphosphate was also observed and was accompanied by increased chloride channel activity . This indicates that SopB alone is sufficient for changes in chloride channel function in cells infected with Salmonella organisms . Depletion of inositol phosphates, including InsP(5) and InsP(6) metabolites, was coincident with the accumulation of polyadenylated RNA in the nucleus . This suggested that a defect in nuclear export had occurred . Moreover, the penetrance of the export defect required localization of SopB to the nucleus . These results provide evidence that inositol phosphate productions may be required for efficient mRNA export in mammalian cells.

J Clin Microbiol, 2001 Feb, 39(2), 791 - 3
Characterization of extended-spectrum beta-lactamase (TEM-52)-producing strains of Salmonella enterica serovar typhimurium with diverse resistance phenotypes; Vahaboglu H et al.; Two Salmonella enterica serovar Typhimurium strains from different clonal origins, both producing an extended-spectrum beta-lactamase (TEM-52), were isolated from a patient . This enzyme was encoded on a single plasmid and was found at very low levels in one strain, while being encoded on multiple plasmids and in multiple different EcoRI fragments in the other strain.

J Clin Microbiol, 2001 Feb, 39(2), 618 - 21
Molecular and phenotypic characterization of potentially new Shigella dysenteriae serotype; Coimbra RS et al.; From September 1997 to November 1998, the French National Center for Salmonella and Shigella received 22 Shigella isolates recovered from 22 different patients suffering from dysentery . None of these isolates reacted with any of the antisera used to identify established Shigella serotypes, but all of them agglutinated in the presence of antisera to a previously described potentially new Shigella dysenteriae serotype (represented by strain 96-204) primarily isolated from stool cultures of imported diarrheal cases in Japan . All French isolates, as well as strain 96-204, showed biochemical reactions typical of S . dysenteriae and gave positive results in a PCR assay for detection of the plasmid ipaH gene coding for invasiveness . No Shiga toxin gene was detected by PCR . These isolates were indistinguishable by molecular analysis of ribosomal DNA (ribotyping) and seemed to be related to S . dysenteriae serotypes 3 and 12 . However, further characterization by restriction of the amplified O-antigen gene cluster clearly distinguished this new serotype from all other Shigella or Escherichia coli serotypes.

J Bacteriol, 2001 Feb, 183(4), 1495 - 8
OmpC is the receptor for Gifsy-1 and Gifsy-2 bacteriophages of Salmonella; Ho TD et al.; Mutations in the Salmonella enterica serovar Typhimurium ompC gene conferred resistance to Gifsy-1 and Gifsy-2 bacteriophages . Selection for complementing plasmids yielded clones of ompC . Introduction of an ompC clone into Escherichia coli conferred the ability to adsorb Gifsy phage . These data show that OmpC is the receptor for Gifsy-1 and Gifsy-2 phages.

J Bacteriol, 2001 Feb, 183(4), 1452 - 4
SigE is a chaperone for the Salmonella enterica serovar Typhimurium invasion protein SigD; Darwin KH et al.; SigD is translocated into eucaryotic cells by a type III secretion system . In this work, evidence that the putative chaperone SigE directly interacts with SigD is presented . A bacterial two-hybrid system demonstrated that SigE can interact with itself and SigD . In addition, SigD was specifically copurified with SigE-His(6) on a nickel column.

J Bacteriol, 2001 Feb, 183(4), 1300 - 11
One of two hemN genes in Bradyrhizobium japonicum is functional during anaerobic growth and in symbiosis; Fischer HM et al.; Previously, we screened the symbiotic gene region of the Bradyrhizobium japonicum chromosome for new NifA-dependent genes by competitive DNA-RNA hybridization (A . Nienaber, A . Huber, M . Gottfert, H . Hennecke, and H . M . Fischer, J . Bacteriol . 182:1472-1480, 2000) . Here we report more details on one of the genes identified, a hemN-like gene (now called hemN(1)) whose product exhibits significant similarity to oxygen-independent coproporphyrinogen III dehydrogenases involved in heme biosynthesis in facultatively anaerobic bacteria . In the course of these studies, we discovered that B . japonicum possesses a second hemN-like gene (hemN(2)), which was then cloned by using hemN(1) as a probe . The hemN(2) gene maps outside of the symbiotic gene region; it is located 1.5 kb upstream of nirK, the gene for a Cu-containing nitrite reductase . The two deduced HemN proteins are similar in size (445 and 450 amino acids for HemN(1) and HemN(2), respectively) and share 53% identical (68% similar) amino acids . Expression of both hemN genes was monitored with the help of chromosomally integrated translational lacZ fusions . No significant expression of either gene was detected in aerobically grown cells, whereas both genes were strongly induced (> or = 20-fold) under microaerobic or anaerobic conditions . Induction was in both cases dependent on the transcriptional activator protein FixK(2) . In addition, maximal anaerobic hemN(1) expression was partially dependent on NifA, which explains why this gene had been identified by the competitive DNA-RNA hybridization approach . Strains were constructed carrying null mutations either in individual hemN genes or simultaneously in both genes . All mutants showed normal growth in rich medium under aerobic conditions . Unlike the hemN(1) mutant, strains lacking a functional hemN(2) gene were unable to grow anaerobically under nitrate-respiring conditions and largely failed to fix nitrogen in symbiosis with the soybean host plant . Moreover, these mutants lacked several c-type cytochromes which are normally detectable by heme staining of proteins from anaerobically grown wild-type cells . Taken together, our results revealed that B . japonicum hemN(2), but not hemN(1), encodes a protein that is functional under the conditions tested, and this conclusion was further corroborated by the successful complementation of a Salmonella enterica serovar Typhimurium hemF hemN mutant with hemN(2) only.

J Bacteriol, 2001 Feb, 183(4), 1159 - 67
Genetic analysis of assembly of the Salmonella enterica serovar Typhimurium type III secretion-associated needle complex; Sukhan A et al.; Several pathogenic bacteria have evolved a specialized protein secretion system termed type III to secrete and deliver effector proteins into eukaryotic host cells . Salmonella enterica serovar Typhimurium uses one such system to mediate entry into nonphagocytic cells . This system is composed of more than 20 proteins which are encoded within a pathogenicity island (SPI-1) located at centisome 63 of its chromosome . A subset of these components form a supramolecular structure, termed the needle complex, that resembles the flagellar hook-basal body complex . The needle complex is composed of a multiple-ring cylindrical base that spans the bacterial envelope and a needle-like extension that protrudes from the bacterial outer surface . Although the components of this structure have been identified, little is known about its assembly . In this study we examined the effect of loss-of-function mutations in each of the type III secretion-associated genes encoded within SPI-1 on the assembly of the needle complex . This analysis indicates that the assembly of this organelle occurs in discrete, genetically separable steps . A model for the assembly pathway of this important organelle is proposed that involves a sec-dependent step leading to the assembly of the base substructure followed by a sec-independent process resulting in the assembly of the needle portion.

Appl Environ Microbiol, 2001 Feb, 67(2), 977 - 8
Twelve-hour PCR-based method for detection of Salmonella spp . in food; Ferretti R et al.; A PCR-based method for the detection of Salmonella spp . in food was developed . The method, set up on typical salami from the Italian region of Marche, is sensitive and specific and shows excellent correlation with the conventional method of reference when naturally contaminated foods are analyzed . Moreover, it can be easily performed within a maximum of 12 h from food sampling, thus allowing prompt detection of Salmonella spp . in the food stocks analyzed.

J Exp Med, 2001 Feb 5, 193(3), 353 - 64
Protective role of Raf-1 in Salmonella-induced macrophage apoptosis; Jesenberger V et al.; Invasive Salmonella induces macrophage apoptosis via the activation of caspase-1 by the bacterial protein SipB . Here we show that infection of macrophages with Salmonella causes the activation and degradation of Raf-1, an important intermediate in macrophage proliferation and activation . Raf-1 degradation is SipB- and caspase-1-dependent, and is prevented by proteasome inhibitors . To study the functional significance of Raf-1 in this process, the c-raf-1 gene was inactivated by Cre-loxP-mediated recombination in vivo . Macrophages lacking c-raf-1 are hypersensitive towards pathogen-induced apoptosis . Surprisingly, activation of the antiapoptotic mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) and nuclear factor kappaB pathways is normal in Raf-1-deficient macrophages, and mitochondrial fragility is not increased . Instead, pathogen-mediated activation of caspase-1 is enhanced selectively, implying that Raf-1 antagonizes stimulus-induced caspase-1 activation and apoptosis.

Genetics, 2001 Feb, 157(2), 491 - 502
Genetic mapping by duplication segregation in Salmonella enterica; Camacho EM et al.; MudP and MudQ elements were used to induce duplications in Salmonella enterica by formation of a triple crossover between two transduced fragments and the host chromosome . The large size (36 kb) of MudP and MudQ is a favorable trait for duplication formation, probably because homology length is a limiting factor for the central crossover . Additional requirements are a multiplicity of infection of 2 or higher in the infecting phage suspensions (which reflects the need of two transduced fragments) and an exponentially growing recipient (which reflects the need of a chromosome replication fork) . We describe a set of 11 strains of S . enterica, each carrying a chromosomal duplication with known endpoints . The collection covers all the Salmonella chromosome except the terminus . For mapping, a dominant marker (e.g., a transposon insertion in or near the locus to be mapped) is transduced into the 11-strain set . Several transductants from each cross are grown nonselectively, and haploid segregants are scored for the presence of the marker . If all the segregants contain the transduced marker, it maps outside the duplication interval . If the marker is found only in a fraction of the segregants, it maps within the duplicated region.

J Agric Food Chem, 2000 Dec, 48(12), 6431 - 4
Development of a rapid and inexpensive assay for the nonspecific detection of antimicrobial residues in chicken egg yolks and neonatal yolk sacs; Caldwell DY et al.; Competitive exclusion of intestinal pathogens by administration of beneficial and defined cultures of normal intestinal microflora is a safe and effective means of reducing the incidence and severity of chick infections with Salmonella and other intestinal pathogens . It is important that competitive exclusion cultures not carry genetic material (e.g., plasmids), which could transfer antibiotic resistance to other microflora, including pathogens . As such, safe and effective competitive exclusion cultures must be sensitive to commonly used antimicrobial agents . By necessity, intentional or accidental exposure of these beneficial microflora to antibiotics will reduce or eliminate the protection provided by competitive exclusion culture establishment . As antibiotic residues can be present from embryonic, hatchling, or maternal administration, a rapid and sensitive assay for the nonspecific detection of residues, which could interfere with competitive exclusion culture establishment, is needed . This study was conducted to develop a rapid and inexpensive bioassay to detect multiple antimicrobial residues in egg yolk and neonatal yolk sacs . Aerobic bacterial strains with known sensitivity to several antibiotics used by the poultry industry were selected and individually compared for sensitivity to enrofloxacin, gentamicin, tetracycline, ceftiofur, and tylosin concentrations in egg yolks . This assay was found to be relatively sensitive for the detection of these antimicrobials, and detection of residues was associated with reduced competitive exclusion culture (PREEMPT) establishment in one experiment . Importantly, this assay can be implemented with minimal training or equipment under commercial hatchery practices and could be used to determine embryo groups, in advance of hatch, that are not suitable candidates for competitive exclusion treatment in the hatchery.

Clin Neurol Neurosurg, 2000 Dec, 102(4), 236 - 239
Salmonella enteritidis brain abscess: case report and review; Sarria JC et al.; Intracranial infections are unusual manifestations of salmonellosis . Even with adequate medical and surgical interventions these infections are often associated with significant morbidity and mortality . We report a case of brain abscess caused by Salmonella enteritidis associated with a brain neoplasm and review previous reports in the literature.

Berl Munch Tierarztl Wochenschr, 2000 Nov-Dec, 113(11-12), 431 - 4
Prevalence of Salmonella in Ethiopian cattle and minced beef; Nyeleti C et al.; To estimate the prevalence and distribution of Salmonella in the chain from cattle to the consumer, faeces, mesenteric lymphnodes and beef cuts from 235 cattle, stool samples from 300 workers of the same Addis Ababa abattoir, and 330 minced beef samples from supermarkets in Addis Ababa were analyzed . Isolated Salmonella strains were serotyped and tested for antibiotic susceptibility . Low prevalence in faeces and lymphnodes, and higher contamination rates of beef cuts (diaphragm, abdominal muscles) indicate severe cross-contamination during slaughter . Animals of poor health status were far more frequently carriers of salmonellae, which stresses the need of intensive ante-mortem inspection on slaughter animals . During transport from slaughterhouse to the supermarkets, production and selling of minced beef, the prevalence of Salmonella did not increase.

Mutat Res, 2001 Jan 25, 490(1), 45 - 56
Use of a Salmonella microsuspension bioassay to detect the mutagenicity of munitions compounds at low concentrations; George SE et al.; Past production and handling of munitions has resulted in soil contamination at various military facilities . Depending on the concentrations present, these soils pose both a reactivity and toxicity hazard and the potential for groundwater contamination . Many munitions-related chemicals have been examined for mutagenicity in the Ames test, but because the metabolites may be present in low environmental concentrations, a more sensitive method is needed to elucidate the associated mutagenicity . RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), TNT (2,4,6-trinitrotoluene), tetryl (N-methyl-N-2,4,6-tetranitroaniline), TNB (1,3,5-trinitrobenzene) and metabolites were examined for mutagenicity in a microsuspension modification of the Salmonella histidine reversion assay with and without metabolic activation . TNB and tetryl were positive in TA98 (32.5, 5.2revertants/nmole) and TA100 (7.4, 9.5revertants/nmole) without metabolic activation and were more potent than TNT (TA98, 0.3revertants/nmole; TA100, 2.4revertants/nmole) . With the exception of the tetranitroazoxytoluene derivatives, TNT metabolites were less mutagenic than TNT . RDX and two metabolites were negative in both strains, however, hexahydro-1,3,5-trinitroso-1,3,5-triazine was positive in TA100 with and without S9 . Microsuspension bioassay results tend to correlate well with published Ames test data, however, there are discrepancies among the published data sets and the microsuspension assay results.

Mutat Res, 2001 Jan 25, 490(1), 1 - 9
Genotoxic effects of methyl isothiocyanate; Kassie F et al.; Aim of the study was to investigate the genotoxic effects of methyl isothiocyanate (MITC), a compound widely distributed in the environment as a constituent of certain vegetables, a soil fumigant and breakdown product of carbamate pesticides . MITC caused only marginal mutation induction in reversion assays with Salmonella strains TA100 and TA98 and, the maximum effect (<2-fold increase over the background rate) was seen at 100microg/ml . In differential DNA-repair assays with E . coli (strains 343/763 uvrB/recA and 343/765 uvr(+)/rec(+)), a pronounced dose-response effect (induction of repairable DNA-damage) was seen at low concentrations (>/=4microg/ml) . In both bacterial assays, addition of activation mix (rat liver S-9) led to a reduction of the genotoxic effects . In micronucleus assay and in single cell gel electrophoresis assay with human hepatoma cells (HepG2), clear cut positive results were obtained at exposure concentrations of <5microg/ml . On the contrary, only marginal effects were seen in differential DNA-repair host-mediated assays where E . coli indicator cells were recovered from different inner organs of mice that had been treated orally with a high dose (90mg/kg bw) of the test compound . Further in vitro experiments showed that MITC is inactivated by body fluids (saliva, gastric juice) and that its DNA-damaging properties are attenuated by non-enzymatic protein binding . Since exposure of HepG2 cells to MITC led to formation of thiobarbituric acid reactive substances, it is likely that its DNA-damaging effects involve lipid peroxidation processes . Overall, our findings show that MITC induces only marginal effects at extremely high (almost lethal) doses in inner organs in vivo, but it causes DNA-damage at low concentrations in vitro.

Prev Vet Med, 2001 Jan 17, 48(1), 35 - 54
Data-quality issues and alternative variable-screening methods in a questionnaire-based study on subclinical Salmonella enterica infection in Danish pig herds; Stege H et al.; Our aim was to determine risk factors for subclinical Salmonella enterica infection in Danish finishing-pig herds . In this paper, the evaluation, combining and initial reduction of variables is presented, along with assessment of the hypotheses in the preliminary statistical testing.The first group of herds was selected at random with no former knowledge of S . enterica infection . Both the herd prevalence and the within-herd prevalence among these herds turned out to be low; hence, some additional herds were selected from The Danish Salmonella Control program, based on their high seroprevalence . This resulted in a hybrid case-"control" design of the study and therefore, five different methods of categorising the data were used to ensure that variables were not wrongfully excluded as a result of using an improper design.Our questionnaire focused on management, infection-limiting precautions and feed and feeding procedures . To establish the prevalence of S . enterica infection within herds at the time of the visit, 50 blood samples from each herd were collected and serologically examined . The reliability of each variable from the questionnaire was assessed and it was decided which variables should be selected, disregarded, combined with other variables and/or recoded . In the simple statistical testing (2x2 tables, cut-off: P=0.25) herds were defined as subclinically S . enterica infected if the within-herd proportion of individual pigs with OD%>10 was more than 20%.The results included questionnaires from 96 randomly selected and 39 high-seroprevalence herds and 6814 blood samples . The initial 95 variables originally included in the questionnaires were reduced to 21 by critical check, combination, recoding and preliminary screening . We failed to demonstrate "herd size" as a risk factor for subclinical S . enterica infection in pig herds.

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