Shigella

Infect Immun, 1999 Jan, 67(1), 350 - 6
Establishment of unipolar localization of IcsA in Shigella flexneri 2a is not dependent on virulence plasmid determinants; Sandlin RC et al.; Unipolar localization of IcsA on the surface of Shigella flexneri is required for efficient formation of actin tails and protrusions in infected eucaryotic cells . Lipopolysaccharide (LPS) mutations have been demonstrated to affect either the establishment or the maintenance of IcsA in a unipolar location, although the mechanism is unknown . In order to analyze the contribution of virulence plasmid determinants on the unipolar localization of IcsA, we examined the localization of IcsA expressed from a cloned plasmid copy in two different genetic backgrounds . The localization of IcsA was first examined in a virulence plasmid-cured derivative of the wild-type S . flexneri 2a isolate 2457T . This approach examined the contribution of virulence plasmid-borne factors, including the previously identified virulence plasmid-borne protease that is responsible for cleaving IcsA in the outer membrane and releasing the 95-kDa secreted form from the cell surface . IcsA localization in a related but nonpathogenic Escherichia coli strain expressing LPS of the O8 serotype was also examined . IcsA surface presentation in both of these genetic backgrounds continued to be unipolar, demonstrating that virulence plasmid-borne determinants are not responsible for unipolar localization of IcsA . The unipolar localization of IcsA in the E . coli background suggests that a common pathway that allows IcsA to be spatially restricted to one pole on the bacterial cell surface exists in Shigella and E . coli.

Blood, 1999 Jan 1, 93(1), 394 - 8
Peripheral blood CD14(+) cells from healthy subjects carry a circular conformation of latent cytomegalovirus genome; Bolovan-Fritts CA et al.; The majority of the human population harbors latent cytomegalovirus . Although CD14(+) peripheral blood mononuclear cells have been implicated as sites of latency, the conformation of the latent viral genome in these cells is unknown . In this study, the conformation of viral genomic DNA was assessed in CD14(+) cells from healthy virus seropositive carriers using an electrophoretic separation on native agarose gels in combination with polymerase chain reaction detection . Here we show that the viral genome migrates as a circular plasmid with a mobility equivalent to a circular 230-kb Shigella flexneri megaplasmid marker . Neither linear nor complex or integrated forms of the viral genome were detected . This report provides further evidence that the CD14(+) cell population is an important site of viral latency in the naturally infected human host . Detection of the viral genome as a circular plasmid during latency suggests that this virus maintains its genome in a manner analogous to other herpesviruses where latent viral genome conformation has been studied.

Am J Med Sci, 1998 Dec, 316(6), 379 - 84
Multiresistant Shigella species isolated from pediatric patients with acute diarrheal disease; Flores A et al.; A total of 57 strains of Shigella (36 S sonnei, 21 S flexneri), isolated from children with acute diarrheal disease who presented for treatment at the Andes University Hospital, Merida, Venezuela, from June 1993 to June 1995, were tested for their susceptibility to trimethoprim, sulfamethoxazole, ampicillin, cefamandole, ceftriaxone, streptomycin, fleroxacin, and nalidixic acid, by the agar dilution method . Twenty-seven strains (75%) of S sonnei and eight strains of S flexneri (38.1%) isolates showed high-level resistance to trimethoprim (MIC90 > 1024 microg/mL), which was also associated with other resistance patterns . The most common resistant phenotype associated with trimethoprim-resistance among S sonnei isolates was sulfamethoxazole-streptomycin (63%); among S flexneri isolates, it was sulfamethoxazole-ampicillin-streptomycin (87.5%) . Individual resistance was only observed for ampicillin, mainly in four isolates of S flexneri, and in one isolate of S sonnei . Most Shigella strains were resistant to three or more antimicrobial agents . These results confirmed that multiresistant strains of Shigella are present in Merida, and emphasize the importance to maintain these under surveillance in order to assess local susceptibility patterns and empiric therapy.

Commun Dis Public Health, 1998 Dec, 1(4), 279 - 80
Shigella outbreak in a school associated with eating canteen food and person to person spread; Maguire HC et al.; In June 1993 an outbreak of Shigella sonnei infection at a primary school in south east England affected 42% of 327 pupils and staff . Attack rates of diarrhoea and fever were 33% for children aged 4 to 8 years, and 8% for those aged 8 to 12 years (p < 0.00001) . Illness was associated with eating canteen food (relative risk 5.9; 95% confidence interval 3.4, -10.3) . All strains examined were S . sonnei phage type 3, with the same antibiogram (ttSTSS), and were indistinguishable using colicin typing and biotyping (colicin type 9, E8) and pulse field gel electrophoresis . Molecular epidemiology suggested but could not confirm that the outbreak strain was introduced into the school population from the community.

Ann Med Interne (Paris), 1998 Oct, 149(6), 340 - 50
{Vaccination against diarrheal diseases and typhoid fever . Current status and prospects}; Ivanoff B et al.; Diarrheal diseases and typhoid fever are still common in developing countries and there is still a search for effective control measures able to prevent the epidemics they cause from time to time . There are recommended preventive measures based on health education and improvement of sewage and water facilities; however these recommendations given for many years have not reached the expected results for different reasons . Antibiotherapy was very effective for many years; unfortunately increasing antibiotic resistance has been reported, particularly in Shigella and typhoid fever treatment . This explains the re-kindled interest currently taking place in vaccines development against infections due to V . cholerae, Shigella, E.coli ETEC, S . typhi and rotavirus . The new available vaccines are very effective and provide greater protection than that given by the old killed injectable vaccines . They paved the way for development of new candidate vaccines easier to deliver (oral vaccines or one dose parenteral vaccine), which already give promising results . Some of these candidate vaccines like those related to Shigella infections are considered as a future promising tool for controlling diarrhea due to Shigella.

EMBO J, 1998 Dec 1, 17(23), 7033 - 43
Thermoregulation of Shigella and Escherichia coli EIEC pathogenicity . A temperature-dependent structural transition of DNA modulates accessibility of virF promoter to transcriptional repressor H-NS; Falconi M et al.; The expression of plasmid-borne virF of Shigella encoding a transcriptional regulator of the AraC family, is required to initiate a cascade of events resulting in activation of several operons encoding invasion functions . H-NS, one of the main nucleoid-associated proteins, controls the temperature-dependent expression of the virulence genes by repressing the in vivo transcription of virF only below a critical temperature (approximately 32 degrees C) . This temperature-dependent transcriptional regulation has been reproduced in vitro and the targets of H-NS on the virF promoter were identified as two sites centred around -250 and -1 separated by an intrinsic DNA curvature . H-NS bound cooperatively to these two sites below 32 degrees C, but not at 37 degrees C . DNA supercoiling within the virF promoter region did not influence H-NS binding but was necessary for the H-NS-mediated transcriptional repression . Electrophoretic analysis between 4 and 60 degrees C showed that the virF promoter fragment, comprising the two H-NS sites, undergoes a specific and temperature-dependent conformational transition at approximately 32 degrees C . Our results suggest that this modification of the DNA target may modulate a cooperative interaction between H-NS molecules bound at two distant sites in the virF promoter region and thus represents the physical basis for the H-NS-dependent thermoregulation of virulence gene expression.

J Biol Chem, 1998 Dec 4, 273(49), 32895 - 900
Shigella-induced apoptosis is dependent on caspase-1 which binds to IpaB; Hilbi H et al.; We report here that the Shigella invasion plasmid antigen (Ipa)B, which is sufficient to induce apoptosis in macrophages, binds to caspase (Casp)-1, but not to Casp-2 or Casp-3 . Casp-1 is activated and its specific substrate interleukin-1beta is cleaved shortly after Shigella infection . Macrophages isolated from Casp-1 knock-out mice are not susceptible to Shigella-induced apoptosis, although they respond normally to other apoptotic stimuli . Shigella kills macrophages from casp-3, casp-11, and p53 knock-out mice as well as macrophages overexpressing Bcl-2 . We propose that Shigella induces apoptosis by directly activating Casp-1 through IpaB, bypassing signal transduction events and caspases upstream of Casp-1 . Taken together these data indicate that Shigella-induced apoptosis is distinct from other forms of apoptosis and seems uniquely dependent on Casp-1.

Membr Cell Biol, 1998, 12(1), 1 - 8
Structural features, physiological roles, and biotechnological applications of the membrane proteases of the OmpT bacterial endopeptidase family: a micro-review; Stathopoulos C; The proteins of the OmpT family represent a new class of integral membrane peptidases showing no sequence homology with other known classes of proteases . The prototype of the family, the Escherichia coli K-12 protein OmpT (or omptin), is an outer membrane endopeptidase with unusual specificity: it cleaves the peptide bond between two basic amino acids . A second distinct characteristic of OmpT is its ability to function even under extreme denaturing conditions (e.g . high concentration of urea) . There is a growing number of reports that associate the proteases of the OmpT family with pathogenicity of certain gram-negative bacteria such as Yersinia pestis, Shigella flexneri, and pathogenic E . coli strains . This article reviews recent developments in the field of the OmpT proteases, provides a guide for the recognition of residues of the active site, and finally discusses potential uses of these proteins in biotechnology applications.

Carbohydr Res, 1998 Sep, 311(3), 121 - 33
Synthesis of tri- and tetrasaccharide fragments of the Shigella dysenteriae type 1 O-antigen deoxygenated and fluorinated at position 3 of the methyl alpha-D-galactopyranoside terminus; Mulard LA et al.; The blockwise synthesis of methyl alpha tri- and tetrasaccharide analogs of the biochemical repeating unit of the Shigella dysenteriae type 1 O-polysaccharide is described . Modifications include deoxygenation and deoxyfluorination at position 3 of the galactopyranoside residue . Methyl 4,6-O-benzylidene-3-deoxy-alpha-D-xylo-hexopyranoside (8) and methyl 4,6-O-benzylidene-3-deoxy-3-fluoro-alpha-D-galactopyranoside (9) were condensed with (2,3,4-tri-O-benzoyl-alpha-L-rhamnopyranosyl)-(1-->3) -2,4-di-O-benzoyl-alpha-L-rhamnopyranosyl chloride to give, after deprotection, the target trisaccharide methyl alpha-L-rhamnopyranosyl-(1-->3)-alpha-L- rhamnopyranosyl-(1-->2)-3-deoxy-alpha-D-xylo-hexopyranoside and the corresponding fluorinated oligosaccharide . For the tetrasaccharide synthesis, the glycosyl acceptors 8 and 9 were condensed with the temporarily protected (2,4-di-O-benzoyl-3-O-chloroacetyl-alpha-L- rhamnopyranosyl)-(1-->3)-2,4-di-O-benzoyl-alpha-L-rhamnopyranosyl chloride . Removal of the chloroacetyl group was followed by condensation of the resulting selectively deblocked trisaccharides with 3,4,6-tri-O-acetyl-2-azido-2-deoxy-alpha-D-glucopyranosyl chloride . Reduction and deprotection then gave the free methyl 2-acetamido-2-deoxy- alpha-D-glucopyranosyl-(1-->3)-alpha-L-rhamnopyranosyl- (1-->3)-alpha-L-rhamnopyranosyl-(1-->2)-3-deoxy-alpha-D-xylo-hexopyra noside and the fluorinated analog.

Tidsskr Nor Laegeforen, 1998 Sep 30, 118(23), 3649 - 53
{Communicable disease control in connection with international air traffic to Norway}; Aavitsland P et al.; International air traffic has increased the risk of importation of infectious diseases to Norway . We have used notification data and a theoretical framework to assess the risk of importation and subsequent disemination of serious infectious diseases in Norway . Every year, a few cases of these diseases are imported to Norway, especially malaria, shigellosis and typhoid fever . A few secondary cases of enteric diseases may occur, but epidemics are unlikely . Counselling and immunisation of Norwegians going abroad is the first step in prevention . Secondly, health services all over the country should be able to diagnose imported diseases early and institute infection control measures . However, there is no need for concentrating resources for disease control at international airports in Norway.

J Cell Biol, 1998 Nov 16, 143(4), 1003 - 12
Interferon alpha inhibits a Src-mediated pathway necessary for Shigella-induced cytoskeletal rearrangements in epithelial cells; Dumenil G et al.; Shigella flexneri, the causative agent of bacillary dysentery, has the ability to enter nonphagocytic cells . The interferon (IFN) family of cytokines was found to inhibit Shigella invasion of cultured epithelial cells . We show here that IFN-alpha inhibits a Src-dependent signaling cascade triggered by Shigella that leads to the reorganization of the host cell cytoskeleton . Immunofluorescence studies showed that IFN-alpha inhibits Shigella-induced actin polymerization required for bacterial entry into cells . Phosphorylation of cortactin, a Src-substrate specifically tyrosyl-phosphorylated during Shigella entry, was inhibited by IFN-alpha . Overexpression of a dominant interfering form of pp60c-src led to inhibition of Shigella-induced cytoskeletal rearrangements and decreased cortactin phosphorylation indicating a role for Src in Shigella entry . Also, Shigella uptake in cells that expressed constitutively active Src was unaffected by IFN-alpha treatment . We conclude that Src kinase activity is necessary for Shigella invasion of epithelial cells and that IFN-alpha inhibits this Src-dependent signaling pathway.

Scand J Infect Dis, 1998, 30(4), 351 - 3
Drug resistance of Shigella strains isolated in Ankara, Turkey, 1993-1996; Aysev AD et al.; 289 Shigella strains were isolated from children at the paediatrics department of Ankara University . 75% of the isolates were S . sonnei and 24.8% were S . flexneri . Each strain was tested for resistance to 9 antimicrobial agents . 79% of the isolates were resistant to streptomycin (S), 56% to tetracycline (T), 55.7% to trimethoprim-sulfamethoxazole (SXT), 27.7% to ampicillin (Am) and 19.7% to chloramphenicol (C) . None of the isolates was resistant to ciprofloxacin, nalidixic acid, cephalothin, ampicillin-sulbactam and ceftriaxone . 56% of the isolates were resistant to 3 or more antimicrobial agents . The most frequent pattern of resistance of S . sonnei and S . flexneri strains was SXT, T, S (39.6%) and Am, SXT, T, S, C (48.6%), respectively (p < 0.0001) . These results demonstrate that trimethoprim-sulfamethoxazole should not be used in the treatment of shigellosis.

J Travel Med, 1995 Jun 1, 2(2), 70 - 76
Illness in Journalists and Relief Workers Involved in International Humanitarian Assistance Efforts in Somalia, 1992-93; Sharp TW et al.; Background: Journalists and relief workers participating in international relief efforts in Somalia following the intervention of outside armed forces in late 1992, were faced with a number of threats to their health . Principally these threats were from endemic infectious diseases and trauma . Methods: In-patient, emergency clinic, and laboratory records of U.S . military field hospitals, which provided the only available sophisticated medical care in Somalia during most of the study period (December 15, 1992, to February 15, 1993), were reviewed to determine the number of workers evaluated and the causes of their illnesses . In addition, two questionnaire surveys were conducted to elucidate risk factors for illness in these groups . Results: One hundred and thirty-eight journalists and relief workers, primarily from Europe and North America, were evaluated at a hospital for a variety of common travel-associated health problems, including diarrhea (33%), acute respiratory infection (21%), other febrile illnesses (11%), hepatitis (2%), major trauma (6%), and minor trauma (13%) . Documented infectious disease pathogens included Plasmodium falciparum (7 cases), Shigella sp (3 cases), enterotoxigenic Escherichia coli (ETEC) (3 cases), dengue virus-2 (2 cases), and hepatitis E virus (3 cases) . Two relief workers were killed by gunshot wounds . In the questionnaire surveys of 104 journalists and 98 relief workers, 84% of respondents reported that they had received some pretravel medical advice, but only 70% sought a medical consultation in person . Thirty-four percent were not receiving a recommended antimalarial chemoprophylaxis regimen, and only 10% obtained a fluoroquinolone antimicrobial drug for self treatment of diarrhea . Sixty-four percent of both groups combined, reported having had diarrhea, and 26% experienced a nondiarrheal febrile illness . Sixty-eight percent reported that their work performance was adversely affected by illness . In multivariate logistic regression analyses, factors associated with an increased risk of diarrhea were age < 35 years (OR 1.5, 95% CI 1.1-1.9); residence in Somalia for more than 21 days (OR 1.7, 95% CI 1.3-2.1); and regular consumption of local food and water (OR 3.8, 95% CI 3.4-4.2) . Factors associated with nondiarrheal febrile illness were age < 35 years (OR 1.4, 95% CI 1.1-1.8); residence in Somalia for more than 21 days (OR 1.8, 95% CI 1.4-2.2); and not having had an in-person pretravel medical consultation (OR 2.0, 95% CI 1.5-3.0) . Conclusions: These data indicate that journalists and relief workers who traveled to Somalia in response to the massive humanitarian crisis themselves experienced substantial health problems . Improved pretravel medical preparation might prevent or limit illness in these unique groups and improve the efficiency of future disaster response efforts . (J Travel Med 2:70-76, 1995)

Proc Natl Acad Sci U S A, 1998 Nov 10, 95(23), 13917 - 22
Vaccinia locomotion in host cells: evidence for the universal involvement of actin-based motility sequences ABM-1 and ABM-2; Zeile WL et al.; Vaccinia uses actin-based motility for virion movement in host cells, but the specific protein components have yet to be defined . A cardinal feature of Listeria and Shigella actin-based motility is the involvement of vasodilator-stimulated phosphoprotein (VASP) . This essential adapter recognizes and binds to actin-based motility 1 (ABM-1) consensus sequences {(D/E)FPPPPX(D/E), X = P or T} contained in Listeria ActA and in the p90 host-cell vinculin fragment generated by Shigella infection . VASP, in turn, provides the ABM-2 sequences {XPPPPP, X = G, P, L, S, A} for binding profilin, an actin-regulatory protein that stimulates actin filament assembly . Immunolocalization using rabbit anti-VASP antibody revealed that VASP concentrates behind motile virions in HeLa cells . Profilin was also present in these actin-rich rocket tails, and microinjection of 10 microM (intracellular) ABM-2 peptide (GPPPPP)3 blocked vaccinia actin-based motility . Vinculin did not colocalize with VASP on motile virions and remained in focal adhesion contacts; however, another ABM-1-containing host protein, zyxin, was concentrated at the rear of motile virions . We also examined time-dependent changes in the location of these cytoskeletal proteins during vaccinia infection . VASP and zyxin were redistributed dramatically several hours before the formation of actin rocket tails, concentrating in the viral factories of the perinuclear cytoplasm . Our findings underscore the universal involvement of ABM-1 and ABM-2 docking sites in actin-based motility of Listeria, Shigella, and now vaccinia.

J Zoo Wildl Med, 1998 Sep, 29(3), 261 - 8
Protein deficiency in a colony of western lowland gorillas (Gorilla g . gorilla)
Mundy NI, Ancrenaz M, Wickings EJ, Lunn PG.
A syndrome of alopecia and weight loss in a colony of 10 western lowland gorillas (Gorilla gorilla gorilla) in Gabon during a 3-yr period was apparently due to a dietary protein deficiency, with nine individuals affected to some extent . The most severely afflicted was a 4-yr-old female who eventually died as a result of acute gastroenteritis caused by Shigella flexneri . Clinical signs included chronic alopecia, hair discoloration, failure to thrive, and weight loss, and their severity was directly correlated with the degree of hypoalbuminemia (12 g/L in the most extreme case) and normocytic normochromic anemia . Preliminary clinical tests and autopsy results suggested a dietary protein or amino acid deficiency as the cause of the hypoalbuminemia, and further analyses of serum amino acid and protein levels were consistent with a diagnosis of dietary protein deficiency . Supplementation of the colony diet with a protein preparation for humans produced a rapid amelioration of signs and improvement in body and coat condition, a normalization of serum albumin and total protein levels, and disappearance of the anemia in all affected animals except a 12-yr-old male, who responded well to treatment with anabolic steroids . The natural diet of western lowland gorillas is surprisingly high in protein, and the dietary protein requirement of captive gorillas may be increased as a result of the absence of commensal gastrointestinal ciliates.

APMIS, 1998 Sep, 106(9), 879 - 83
Antimicrobial susceptibilities and beta-lactamase production of Shigella isolates in Crete, Greece, during the period 1991-1995; Maraki S et al.; The susceptibility to 11 antibiotics was determined for 52 strains of Shigella isolated from patients with diarrheal disease in Crete, Greece, during the period 1991-1995 . Forty-six percent of the isolates were resistant to ampicillin, 48% to tetracycline, 44.2% to chloramphenicol, and 28.8% to cotrimoxazole . Shigella flexneri was more resistant than S . sonnei to ampicillin (82 vs 4.3%), to tetracycline (82 vs 8.7%) and to cotrimoxazole (42.8 vs 13%) . Overall, 82% of all S . flexneri isolates were resistant to the three or four antimicrobial agents tested . The beta-lactamases produced by shigellae were identified by isoelectric focusing and were found to be OXA-1, TEM-1, and a low-level beta-lactamase with a pI>8 . The results from the present study, which is the first carried out in Crete, emphasize the need for continuous surveillance of resistance and control of antibiotic usage.

Rev Cubana Med Trop, 1995, 47(2), 131 - 4
{Septicemia due to Shigella . A case report and review of the literature}; Ben Salas C et al.; Knowing that the isolation of Shigella in blood is considered as an unusual medical event, a case of an infant deceased from septicemia by Shigella sonnei is presented here . This is the first case of the kind reported in Pinar del Rio province . A review of the literature is included.

Kansenshogaku Zasshi, 1998 Sep, 72(9), 935 - 8
{A case of bacillary dysentery caused by new quinolone-resistant Shigella flexneri 2a}; Yoshimura K et al.; A 73-year-old male was admitted to our hospital because of detection of Shigella flexneri 2a from his stool . Antimicrobial treatment with levofloxacin (LVFX) was started, but could not eliminate the organism in the stool . In the examination of drug susceptibility, this strain was highly resistant to all new quinolones . The minimal inhibitory concentration of norfloxacin, ofloxacin and ciprofloxacin to this strain was 12.5 micrograms/ml, 6.25 micrograms/ml and 6.25 micrograms/ml, respectively . The dual mutations were detected in the codon 83 and 87 of the gyrA gene by sequencing the quinolone-resistance determining region (QRDR) . There was, however, no significant difference between the intracellular uptake of ciprofloxacin in this strain and in the ciprofloxacin-sensitive strain . The amount of ciprofloxacin in this strain unchanged when carbonyl cyanide m-chlorophenyl hydrazone (CCCP) was added . These results suggest that the advanced resistance in Shigella flexneri against new quinolones could be acquired by only this dual mutations without the change of the active efflux mechanism.

Sante, 1998 Jul-Aug, 8(4), 303 - 5
{Ciprofloxacin in the treatment of dysentery caused by type 1 Shigella dysenteriae during an epidemic in Rwandan refugees in Goma in 1994}; Laureillard D et al.; There was an outbreak of dysentery caused by type I Shigella dysenteriae among Rwandan refugees at Goma, in what was then Zaire, in 1994 . The causal organism was resistant to all antibiotics available from the public health authorities . The only effective antimicrobial agent available was ciprofloxacin . It was given to 326 inpatients at the Medecins Sans Frontieres (MSF) Center, mostly children under the age of 5, pregnant women and immunocompromised patients . A standard dose schedule was used: 1 g ciprofloxacin per day in two doses for 5 days for adults, 250 mg for children weighing less than 20 kg and 500 mg for children weighing less than 50 kg . The treatment was effective in 285 patients (85.6%) according to clinical criteria . Treatment was unsuccessful in 6 patients and 14 decided to stop taking the medication although it was having a positive effect . No side effects clearly caused by the treatment have been reported . This is consistent with previous reports showing that ciprofloxacin is clinically effective against epidemic dysentery caused by multi-drug resistant Shigella dysenteriae type I . However, fluoroquinolones are expensive and difficult to obtain and their use would require improvements in logistics and compliance.

Mikrobiol Z, 1998 May-Jun, 60(3), 63 - 9
{The inductive immunosuppressive activity of the lipopolysaccharide from Shigella sonnei R forms}; Borisova EV; Investigations have been carried out to find the position of lypopolysaccharide (LPS) structural part which can be activated by the redox system and to study peculiarities of its activation . Cell-free culture filtrate (CF) of Shigella sonnei strain R colonies on the nutrient agar medium was used . It was shown that CF contained three active fractions possessing inductive immunosuppressive properties . From all the phenol-water LPS fractions only lipid A possessed activity after redox treatment . O-chain and our fractions did not express such activity . The results of our investigations have shown that inductive immunosuppressive activity of the Shigella sonnei LPS was determined by lipid A.

Nutrition, 1998 Oct, 14(10), 780 - 3
Local and systemic effects of macrophage cytokines in intestinal inflammation; Murch SH; The activation of macrophages and newly recruited monocytes appears to be common to both Crohn's disease and ulcerative colitis, despite different inductive stimuli . Similar activation occurs acutely during the course of invasive intestinal infections such as shigellosis, but is then usually downregulated . The macrophage cytokines tumor necrosis factor-alpha and interleukin-1 (IL-1) are centrally involved in the local inflammatory response, and blockade of either cytokine greatly attenuates the inflammatory lesion . Induction of focal vascular thrombosis and matrix degradation are thought to be an important component of this focal damage . Both cytokines and IL-6 are now recognized to contribute to the systemic effects of intestinal disease, including growth suppression, anorexia, and chronic anemia . Disturbance of sleep patterns, mood, and affect may also occur, and recent evidence points towards bidirectional interplay between macrophage cytokines and central nervous system function.

Microbiology, 1998 Sep, 144 ( Pt 9), 2667 - 72
Shigella and enteroinvasive Escherichia coli strains are derived from distinct ancestral strains of E . coli; Rolland K et al.; The differentiation between Shigella subspecies, and the phylogenetic position of Shigella clones within Escherichia coli clones was determined by analysis of restriction fragment length polymorphisms of rDNA (ribotyping) . Seventy-five Shigella strains belonging to the four subspecies and 13 enteroinvasive E . coli (EIEC) strains were compared with the 72 E . coli strains of the ECOR collection, which have been classified into four phylogenetic groups (A, B1, B2 and D) . Seventeen Shigella dysenteriae ribotypes, 12 Shigella flexneri ribotypes, 23 Shiegella boydii ribotypes, 12 Shigella sonnei ribotypes and 13 EIEC ribotypes were identified following digestion with HindIII and EcoRI . Correspondence analysis of the data showed that S . boydii serotype 13 strains were distantly related to the other Shigella strains, and that S . sonnei and S . flexneri were distinct from S . boydii and S . dysenteriae . The ribotypes of Shigella and ECOR strains were indistinguishable, and S . sonnei, S . flexneri and most S . dysenteriae strains were closely related to phylogenetic group D, whereas S . dysenteriae serotype 1 strains belonged to phylogenetic group B1, and S . boydii strains were evenly distributed between the two groups . The Shigella strains were distantly related to group B2, which contains E . coli strains frequently implicated in extra-intestinal infections in humans . In contrast, the 13 EIEC strains were more widely distributed between phylogenetic groups B1, A and B2 . Thus, there was no primordial Shigella species and Shigella and EIEC strains are derived from different ancestral strains.

Tsitologiia, 1998, 40(6), 524 - 8
{Invasion of Escherichia coli A2 induces reorganization of actin microfilaments in Hep-2 cells}; Efremova TN et al.; Bacteria of spontaneously isolated non-pathogenic strain E . coli A2 have been previously shown to produce a new proteinase, referred to as protease ECP 32, which specifically cleaves actin (Khaitlina et al., 1988; Matveyev et al., 1996) . Similar proteinase activity was found in revertants of Shigella flexneri L-forms . In this work immunofluorescence and electron microscopy were used to address a question of whether E . coli A2 can invade epithelial cells similarly as it has been demonstrated for Sh . flexneri . Infection of Hep-2 cells with E . coli A2 resulted in bacterial invasion of the cells followed by cytoskeleton reorganization . On one end of intracellular bacteria bundles of actin filaments resembling a comet-like tail were observed . Bacteria of referent strain CCM 5172, not producing protease ECP 32, were not taken up by the cells . These data suggest that protease ECP 32 may be involved in the process of bacterial invasion and cytoskeleton reorganization.

J Nutr, 1998 Oct, 128(10), 1688 - 91
Increased height gain of children fed a high-protein diet during convalescence from shigellosis: a six-month follow-Up study; Kabir I et al.; The impact of dietary supplementation on catch-up growth was evaluated in 69 malnourished children ages 24-60 mo after recovery from shigellosis . They were fed either a high-protein (HP) diet with 15% of energy as protein, or a standard-protein (SP) diet with 7.5% energy as protein, for 3 wk in a metabolic study ward . Children were followed up bi-weekly for 6 mo by trained health assistants when anthropometric measurements and information of any illness were collected . Thirty-one children in the HP group and 28 children in the SP group completed 6-mo follow-up . The increase in height (mean +/- SD) was 5.3 +/- 1.0 cm vs . 4.1 +/- 1.1 cm for HP and SP groups, respectively (P < 0.001), whereas increase in body weight was 1.39 +/- 0.58 and 1.29 +/- 0.72 kg for children fed HP and SP, respectively (P = 0.59) . The proportion of children who were severely stunted (< -2 SD height-for-age) decreased from 45 to 29% in the HP group compared to 50 to 46% in the SP group (P < 0.05) at 6-mo follow-up . The number of diarrheal episodes per child tended to be lower in the HP vs . SP than in the SP group (1.9 vs . 2.3, P = 0.41) . These results demonstrate that feeding an HP diet to the malnourished children during recovery from shigellosis enhanced linear growth with a modest reduction in diarrheal morbidity during the 6-mo follow-up period.

Med Pregl, 1998 Jul-Aug, 51(7-8), 305 - 9
{Shigellae isolated in 1997--plasmid profiles and antibiotic resistance}; Jelesic Z et al.; INTRODUCTION: Shigella spp is one of the most frequently isolated bacteria causing acute diarrhea with us . Genetics of pathogenicity of Shigella spp . includes chromosomal and plasmid genes . Most virulence factors are coded by invasion plasmid antigen genes residing on a 180-230 MDa plasmid . There is a big problem with multiple resistance of Shigella spp . strains, which is mostly plasmid-borne . Genetic analysis of bacterial cells, that is plasmid profile analysis, is important for investigation of sources and ways of spreading of the infection . All isolates originating from the same clone have identical plasmid profiles, i.e . number and size of plasmids . The aim of the investigation was: comparing the type of resistance to antimicrobical agents found in epidemic and nonepidemic . Shigella strains isolated in 1997, analyzing plasmid profiles of these isolates and confirming their epidemic connection . MATERIAL AND METHODS: Susceptibility to antibiotics was examined by a standard disc-diffusion method . Plasmid profiles of 40 strains (20 from the outbreak and 20 from sporadic cases) were tested using a method of alkaline lysis by Birnboim and Doly followed by electrophoresis in agarose gel . RESULTS: Shigella strains were resistant to antimicrobial agents which are most commonly used . Epidemic isolates shared the same resistance type, they were resistant to cephalexin, streptomycin and co-trimoxazole . The dominant type of resistance of nonepidemic strains was to ampicillin, streptomycin and co-trimoxazole . Strains isolated during the outbreak had identical plasmid profiles (2 plasmid bands of 55 and 1.5 MDa) . Non-epidemic isolates had different plasmid profiles as well as type of resistance . CONCLUSION: Strains of Shigella spp . isolated during an outbreak had the same type of resistance and the same plasmid profiles, which indicated their origin from the same clone . The plasmid profile analysis is a reliable and precise method for determination of epidemic connection of Shigella isolates.

Rev Cubana Med Trop, 1994, 46(3), 148 - 51
{Ampicillin resistance mediated by the R plasmid in strains of Shigella flexneri}; Ramirez MM et al.; Forty Shigella flexneri strains isolated from children attended to at the Children's Hospital of Camaguey during an outbreak of acute diarrheal disease were studied; the minimal inhibitory concentration of ampicillin was determined . 33 strains (82.5%) were resistant to higher concentrations: 8 to 16 micrograms/mL, and 7 were susceptible to 4 micrograms/mL concentrations . Resistance plasmid (R) extraction was carried out in all the isolated strains and a common plasmid was found this plasmid was purified and transferred to Escherichia coli HE 101 . Resistance transmission was tested.

Res Microbiol, 1998 Jan, 149(1), 15 - 25
A role for H-NS in the regulation of the virF gene of Shigella and enteroinvasive Escherichia coli; Prosseda G et al.; We have investigated the role of H-NS, one of the major components of the bacterial nucleoid, in the expression of the virF gene present on the large virulence plasmid of Shigella and enteroinvasive Escherichia coli in response to different environmental conditions . VirF is an AraC-like protein which activates at least two promoters, virB and virG, both repressed by H-NS . Band shift experiments reveal that the affinity of H-NS for the virF and virB promoters is comparable, while the affinity for the virG promoter is higher . Polyacrylamide gel electrophoresis of three DNA fragments containing the virF, the virB and the VirG promoters demonstrates, in agreement with computer predictions, that they have an intrinsically curved structure, confirming the preference of H-NS for bent DNA . In vivo transcriptional analysis of virF mRNA shows that H-NS negatively controls the expression of virF at 30 degrees C . The expression of a virF-lacZ translational fusion in E.coli wild type and in an hns-defective derivative grown at 30 degrees or 37 degrees C and at pH 6.0 or 7.0 indicates that, in the absence of H-NS, virF expression becomes insensitive to temperature and to limited pH changes . Our results strongly suggest that H-NS controls virF expression by binding to the virF promoter and by repressing its expression at low temperature and at low pH.

Eur J Immunol, 1998 Sep, 28(9), 2726 - 37
Major histocompatibility complex class I presentation of exogenous soluble tumor antigen fused to the B-fragment of Shiga toxin; Lee RS et al.; Targeting exogenous antigen into the MHC class I-restricted presentation pathway is a prerequisite for the induction of cytotoxic T lymphocytes (CTL) which have been shown to represent an important component of the protective and therapeutic immune response to viral infections and tumors . In this study, we produced recombinant proteins composed of the receptor-binding non-toxic B-fragment of bacterial Shiga toxin derived from Shigella dysenteriae associated with an epitope from a model tumor antigen, Mage 1 . We show that Shiga B-Mage 1 fusion proteins carrying an active or inactive endoplasmic reticulum retrieval signal (the C-terminal peptides KDEL or KDELGL, respectively) could be presented by peripheral blood mononuclear cells in an MHC class I-restricted manner to Mage 1-specific CTL . After pulsing B lymphoblastoid cells or dendritic cells with Shiga B-Mage 1 fusion protein, activation of the MHC class I-restricted Mage 1-specific CTL was also demonstrated . In further analysis, we showed that treatment with brefeldin A or paraformaldehyde fixation of Epstein-Barr virus-transformed B cells prevented the presentation of the Mage 1 T cell epitope, which excluded extracellular processing of the antigen . Immunofluorescence analysis also revealed that the Shiga B-Mage 1 fusion protein was largely excluded from Lamp-2-positive lysosomal structures . Therefore, the ability of Shiga toxin B-fragment to target dendritic cells and B cells and to direct antigen into the exogenous class I-restricted pathway makes it an attractive non-living and non-toxic vaccine vector.

Dig Dis Sci, 1998 Sep, 43(9), 2111 - 6
Quantitative and ultrastructural analysis of rectal mucosal mast cells in acute infectious diarrhea; Pulimood AB et al.; The role of mast cells, potential mediators of mucosal immunity and inflammation, was studied morphologically in the rectal mucosa in two acute diarrheal diseases, cholera and shigellosis . Quantitation of mucosal mast cells showed that they were significantly higher in the deeper lamina propria where blood vessels and nerves were more abundant . There was no difference in mast cell counts or degranulation in the mucosa in both groups of patients and controls . Intraepithelial mast cells were decreased in the patients . The prevalence of lipid bodies was significantly higher in mast cells from patients with cholera and shigellosis (P < 0.01) . These findings suggest that mast cell populations are more dense around blood vessels and nerves and that inflammatory mediators derived from arachidonic acid metabolites, as indicated by the lipid bodies, are the response of mast cells to the alterations in diarrhea, despite differences in the etiology of diarrhea.

J Bacteriol, 1998 Oct, 180(19), 5260 - 2
H-NS regulates DNA repair in Shigella; Palchaudhuri S et al.; We report a new role for H-NS in Shigella spp.: suppression of repair of DNA damage after UV irradiation . H-NS-mediated suppression of virulence gene expression is thermoregulated in Shigella, being functional at 30 degrees C and nonfunctional at 37 to 40 degrees C . We find that H-NS-mediated suppression of DNA repair after UV irradiation is also thermoregulated . Thus, Shigella flexneri M90T, incubated at 37 or 40 degrees C postirradiation, shows up to 30-fold higher survival than when incubated at 30 degrees C postirradiation . The hns mutants BS189 and BS208, both of which lack functional H-NS, show a high rate of survival (no repression) whether incubated at 30 or 40 degrees C postirradiation . Suppression of DNA repair by H-NS is not mediated through genes on the invasion plasmid of S . flexneri M90T, since BS176, cured of plasmid, behaves identically to the parental M90T . Thus, in Shigella the nonfunctionality of H-NS permits enhanced DNA repair at temperatures encountered in the human host . However, pathogenic Escherichia coli strains (enteroinvasive and enterohemorrhagic E . coli) show low survival whether incubated at 30 or 40 degrees C postirradiation . E . coli K-12 shows markedly different behavior; high survival postirradiation at both 30 and 40 degrees C . These K-12 strains were originally selected from E . coli organisms subjected to both UV and X irradiation . Therefore, our data suggest that repair processes, extensively described for laboratory strains of E . coli, require experimental verification in pathogenic strains which were not adapted to irradiation.

Epidemiol Infect, 1998 Aug, 121(1), 43 - 8
Shigella infections among children in Andaman--an archipelago of tropical islands in Bay of Bengal; Ghosh AR et al.; Shigellosis is common among children in the Andaman and Nicobar islands . Our experience showed two distinct features of shigellosis within a span of 3 years in 1994-6: (i) changing patterns of serotype or subtype specific shigellosis and (ii) emergence of multidrug resistant isolates with changing R-patterns . The rate of isolation was 10.4-27.9% with the rate of isolation of Shigella flexneri interchanging with S . dysenteriae alternately . In 1994, S . flexneri superseded S . dysenteriae (48.6% vs . 33.3%; P < 0.05) while S . dysenteriae dominated over S . flexneri in 1995 (54.7% vs . 34.0%; P < 0.05) . The picture reversed again in 1996 (63.0% vs . 22.2%; P < 0.05) . Among shigellae isolates, the commonest serotypes were S . dysenteriae type 1 and S . flexneri type 2a . Isolated shigellae were of multidrug resistant type . Seven R-patterns were observed in 1994, while 8R-patterns were observed during the next year with the emergence of nalidixic acid resistance . In 1996, emergence of gentamicin resistance was also observed . All isolates were resistant to ampicillin and sensitive to quinolones . The MIC of nalidixic acid and gentamicin are > or = 128 microg/ml and > or = 64 microg/ml respectively . These changing trends in shigellosis has important public health significance.

Infect Immun, 1998 Oct, 66(10), 4957 - 64
Expression of the virulence plasmid-carried apyrase gene (apy) of enteroinvasive Escherichia coli and Shigella flexneri is under the control of H-NS and the VirF and VirB regulatory cascade; Berlutti F et al.; The transcription of the virulence plasmid (pINV)-carried invasion genes of Shigella flexneri and enteroinvasive Escherichia coli (EIEC) is induced at 37 degreesC and repressed at 30 degreesC . In this work, we report that the O135: K-:H- EIEC strain HN280 and S . flexneri SFZM53, M90T, and 454, of serotypes 4, 5, and 2a, respectively, produce apyrase (ATP-diphosphohydrolase), the product of the apy gene . In addition, the S . flexneri strains, but not the EIEC strain, produce a nonspecific phosphatase encoded by the phoN-Sf gene . Both apy and phoN-Sf are pINV-carried loci whose contribution to the pathogenicity of enteroinvasive microorganisms has been hypothesized but not yet established . We found that, like that of virulence genes, the expression of both the apy and the phoN-Sf genes was temperature regulated . Strain HN280/32 (a pINV-integrated avirulent derivative of HN280 which has a severe reduction of virB transcription) expressed the apy gene in a temperature-regulated fashion but to a much lower extent than wild-type HN280, while the introduction of the Deltahns deletion in HN280 and in HN280/32 induced the wild-type temperature-independent expression of apyrase . These results indicated that a reduction of virB transcription, which is known to occur in the pINV-integrated strain HN280/32, accounts for reduced apyrase expression and that the histone-like protein H-NS is involved in this regulatory network . Independent spontaneously generated mutants of HN280 and of SFZM53 which had lost the capacity to bind Congo red dye (Crb-) were isolated, and the molecular alterations of pINV were evaluated by PCR analysis . Alterations of pINV characterized by the absence of virF or virB and by the presence of the intact apy locus or intact apy and phoN-Sf loci were detected among Crb- mutants of HN280 and SFZM53, respectively . While all Crb- apy+ mutants of HN280 failed to produce apyrase, Crb- apy+ phoN-Sf+ mutants of SFZM53 lacked apyrase activity but produced a nonspecific phosphatase, like parental SFZM53 . Moreover, the introduction of recombinant plasmids carrying cloned virF (pMYSH6504) or virB (pBN1) into Crb- mutants of HN280 and SFZM53 lacking virF or virB, respectively, fully restored temperature-dependent apyrase expression to levels resembling those of the parental strains . Taken together, our results demonstrate that, as has already been shown for invasion genes, apy is another locus whose expression is controlled by temperature, H-NS, and the VirF and VirB regulatory cascade . In contrast, the temperature-regulated expression of the nonspecific phosphatase does not appear to be under the control of the same regulatory network . These findings led us to speculate that apyrase may play a role in the pathogenicity of enteroinvasive bacteria.

Infect Immun, 1998 Oct, 66(10), 4700 - 10
Identification of two Shigella flexneri chromosomal loci involved in intercellular spreading; Hong M et al.; The ability of Shigella flexneri to multiply within colonic epithelial cells and spread to adjacent cells is essential for production of dysentery . Two S . flexneri chromosomal loci that are required for these processes were identified by screening a pool of TnphoA insertion mutants . These mutants were able to invade cultured epithelial cells but could not form wild-type plaques . Analysis of the nucleotide sequence indicated that the sites of TnphoA insertion were within two different regions that are almost identical to Escherichia coli K-12 chromosomal sequences of unknown functions . One region is located at 70 min on the E . coli chromosome, upstream of murZ, while the other is at 28 min, downstream of tonB . The mutant with the insertion at 70 min was named vpsC because it showed an altered pattern of virulence protein secretion . The vpsC mutant formed pinpoint-sized plaques, was defective in recovery from infected tissue culture cells, and was sensitive to lysis by the detergent sodium dodecyl sulfate . Recombinant plasmids carrying the S . flexneri vpsA, -B, and -C genes complemented all of the phenotypes of the vpsC mutant . A mutation in vpsA resulted in the same phenotype as the vpsC mutation, suggesting that these two genes are part of a virulence operon in S . flexneri . The mutant with the insertion at 28 min was interrupted in the same open reading frame as S . flexneri ispA . This ispA mutant could not form plaques and was defective in bacterial septation inside tissue culture cells.

Indian J Med Res, 1998 Jul, 108, 3 - 7
Oxidative stress response in Shigella & nonpathogenic gut bacteria; Khanduja V et al.; The effect of oxidative stress in the form of exogenous H2O2 on the survival of four species of Shigella and two nonpathogenic Gram negative gut bacteria and the role of catalase as an antioxidant enzyme, neutralizing the effect of H2O2 were examined . A significant decrease in the number of colony forming units (CFUs) after exposure to exogenous H2O2 (122 +/- 37), compared to control bacteria (218 +/- 63, P < 0.001) was observed . There was an induction of catalase activity after exposure to exogenous H2O2 and the specific activity of catalase in H2O2 exposed bacteria was significantly increased (2.88 +/- 1.25), compared to control bacteria (1.5 +/- 0.44; P < 0.05) . A direct correlation was observed between the decrease in bacterial counts and increase in catalase activity after exposure of H2O2 (regression coefficient (0.56) . Gut bacteria appear to be susceptible to oxidative stress and inducible catalase activity may form an important part of the antioxidant defence mechanism against oxidative stress.

Carbohydr Res, 1998 Jul, 309(3), 219 - 26
Binding of modified fragments of the Shigella dysenteriae type 1 O-specific polysaccharide to monoclonal IgM 3707 E9 and docking of the immunodeterminant to its modeled Fv; Miller CE et al.; The O-specific polysaccharide (O-SP) of Shigella dysenteriae type 1 has been shown by others to have the structure-->3)-alpha-L-Rhap-(1-->3)-alpha-L-Rhap-(1-->2)-alp ha-D- Galp-(1-->3)-alpha-D-GlcpNAc-(1--> . We have shown in the past that IgM 3707 E9, an anti S . dysenteriae type 1 O-SP monoclonal antibody, binds specifically to the -alpha-L-Rhap-(1-->2)-alpha-D-Galp-determinant of the polysaccharide . In this report we show that determinant to have hydrogen bonds, necessary for binding to the antibody, involving positions 3, 4 and 6 of the galactopyranosyl residue . The hydroxyl groups of the rhamnopyranosyl moiety of the immunodeterminant appear not to partake in hydrogen-bond interactions with the antibody . A model is presented of the Fv of IgM 3707 E9 based on our previously established cDNA-sequence and two known, highly homologous immunoglobulin crystal structures . The methyl glycoside of the immunodeterminant alpha-L-rhamnopyranosyl-(1-->2)-alpha-D-galactopyranose is docked to the combining area of the Fv.

FEMS Microbiol Lett, 1998 Sep 1, 166(1), 79 - 87
Serotype conversion of a Shigella flexneri candidate vaccine strain via a novel site-specific chromosome-integration system; Guan S et al.; Shigella flexneri SFL124 (serotype Y) is a promising live oral vaccine candidate, which has been shown to be safe and immunogenic in human volunteers . To change the serotype of this vaccine strain, we inserted a serotype conversion gene cluster into the chromosome of SFL124 by using a bacteriophage-based site-specific integration system . By cloning an integrase gene (int), an attachment site (attP) and a glucosyl transfer gene cluster from bacteriophage SfX into a suicide vector, and subsequently introducing this construct into S . flexneri SFL124, we obtained a S . flexneri strain (designated SFL1213) expressing the serotype X somatic antigen specificity . The strain retained other characteristics of the parent strain, such as colony shape, growth rate, and Congo red binding property . Stability test showed that the serotype X O-antigen specificity in SFL1213 was 100% stable after being cultured approximately 72 successive hours under non-selective condition . In a mouse pulmonary model, the recombinant strain elicited a significant level of humoral antibodies which recognized the lipopolysaccharide (LPS) of a wild-type S . flexneri serotype X strain . The site-specific insertion system will be useful when stable expression of a cloned single copy gene is desired in the chromosome of S . flexneri vaccine candidate, SFL124.

Mol Microbiol, 1998 Aug, 29(3), 677 - 84
The Shigella virulence gene regulatory cascade: a paradigm of bacterial gene control mechanisms; Dorman CJ et al.; Shigella flexneri is the causative agent of bacillary dysentery and is a facultative intracellular pathogen . Its virulence regulon is subject to tight control by several mechanisms involving the products of over 20 genes and an array of environmental signals . The reguIon is carried on a plasmid that is prone to instability and to integration into the chromosome, with associated silencing of the virulence genes . Closely related regulons are found in other species of Shigella and in enteroinvasive Escherichia coli . A wealth of detailed information is now available on the Shigella virulence gene control circuits, and it is becoming clear that these share many features with regulatory systems found in other bacterial pathogens . All of this makes the S . flexneri virulence gene control system a very attractive topic for those interested in the nature of gene regulatory networks in bacteria.

J Chemother, 1998 Aug, 10(4), 285 - 90
Prevalence and susceptibility of Shigella species to 11 antibiotics in a Kuwait teaching hospital; Jamal WY et al.; During the 5-year period 1990-1993 and 1996, 202 Shigella spp . were isolated from stool specimens of symptomatic patients of all age groups seen in our hospital . Over these periods the trend of the incidence of shigellosis showed that 18% of the total strains were isolated during the invasion year (1990) followed by an upsurge (24%) during the Gulf War period (1991) and a steady decline in the post-war period, 17% in 1992 and 14% in 1993 . There was another wave of increased isolation rate (27%) during a period of relative calm in the country (1996) studied for comparison . The predominant Shigella species was S . flexneri which accounted for 46% of the 202 isolates, followed by S . sonnei (42%), S . dysenteriae (7%) and S . boydii (5%) . Fifty-four percent of the 202 Shigella isolates were resistant to ampicillin, 56% to trimethoprim/sulfamethoxazole, 35% to chloramphenicol, 13% and 9% to cephalothin and amoxicillin/clavulanic acid respectively . All the isolates were fully susceptible to ciprofloxacin, the aminoglycosides and the second- and third-generation cephalosporins . Eighty-seven (43%) of the 202 isolates were resistant to two or more antibiotics . Of the 87 multiply resistant Shigella spp., 58 (67%) were S . flexneri while 19 (22%) were S . sonnei . Shigella resistance to the first-line antibiotics is a major problem that frequently limits the therapeutic options with orally available active antibiotic therapy.

Folia Microbiol (Praha), 1998, 43(3), 305 - 10
Interaction of vaccinia virus with the actin cytoskeleton; Way M; Vaccinia virus infection results in large rearrangements of the host actin cytoskeleton including the formation of actin tails that are strikingly similar to those seen in Listeria, Shigella and Rickettsia infections . Using actin polymerization as the driving force the intracellular enveloped form of the vaccinia virus (IEV) is propelled on the tip of actin tails at a speed of 2.8 microns/min, both intra- and intercellularly . The similarities between the actin-based motility of the vaccinia virus, Listeria, Shigella and Rickettsia suggest that intracellular pathogens have developed a common strategy to exploit the actin cytoskeleton of the host to facilitate their intercellular spread . This review focuses on our current understanding of the interactions between the vaccinia virus and the actin cytoskeleton.

Folia Microbiol (Praha), 1998, 43(3), 239 - 46
Molecular and cellular mechanisms of invasion of the intestinal barrier by enteric pathogens . The paradigm of Shigella; Sansonetti PJ; The pathogenesis of bacillary dysentery can be studied at different levels of integration of the cellular components that constitute the colonic mucosal barrier . We considered the interaction of Shigella flexneri in three experimental systems that provide complementary information and a scheme of events occurring in human colorectal mucosa as Shigella invasion proceeds . Interaction of S . flexneri with individual epithelial cells shows a series of events in which the bacterium, upon contact with the cell surface, releases a set of Ipa proteins (i.e . invasins) through a specialized, activable, type-III secretory apparatus (i.e . Mxi/Spa) . Via a complex signaling process, these invasins cause major rearrangements of the subcortical cytoskeletal network which allow bacterial entry by a macropinocytotic event . Then the bacterium lyses its phagocytotic vacuole and initiates intracytoplasmic movement, due to polar assembly of actin filaments caused by a bacterial surface protein, IcsA . This allows very efficient colonization of the host cell cytoplasm and passage to adjacent cells via protrusions which are engulfed by a cadherin-dependent process . However, when invasive Shigella are deposited on the apical side of polarized monolayers of human colonic cells, they appear unable to invade, indicating that bacteria need to reach the subepithelial area to invade the epithelium . In this system, it has been shown that transepithelial signaling caused by apical bacteria induces adherence and transmigration of basal polymorphonuclears (PMN), thus disrupting the monolayer permeability and facilitating bacterial invasion . LPS accounts for a large part of this transepithelial signalization to PMN . Such a process could account for invasion in intestinal crypts . Finally, models of infection, such as the rabbit ligated intestinal loop show that initial bacterial entry occurs essentially via M cells of the follicular associated epithelium . It then causes apoptosis of macrophages located in the follicular dome, inducing release of IL-1 beta which, in turn, initiates inflammation, leading to destabilization of the epithelial structures as modeled above . These data can now be used to understand the mechanisms of mucosal protection against bacillary dysentery.

Br J Rheumatol, 1998 Jul, 37(7), 784 - 8
Longitudinal investigation of bacterium-specific synovial lymphocyte proliferation in reactive arthritis and lyme arthritis; Fendler C et al.; BACKGROUND: Antigen-specific lymphocyte proliferation of synovial fluid mononuclear cells (SF MNC) has been reported repeatedly in reactive arthritis and Lyme arthritis; however, less information is available on serial investigations of SF MNC in the same patients . METHODS: In this study, the synovial lymphocyte proliferation to Yersinia, Chlamydia, Shigella and Borrelia burgdorferi was investigated sequentially at different time points in 28 patients with reactive arthritis, undifferentiated oligoarthritis or Lyme arthritis responding to one of these bacteria . RESULTS: The same bacterium was always recognized in arthritis triggered by Chlamydia, Shigella or Borrelia, with much variation in the proliferative response . Only the Yersinia-specific responses changed specificity, suggesting that the proliferative response to Yersinia is non-specific in some patients . CONCLUSIONS: Our data support the concept of a local antigen-specific T-cell response in reactive arthritis or Lyme arthritis but not the concept suggested by others that a switch to an autoimmune response takes place in long-standing disease.

Infect Immun, 1998 Sep, 66(9), 4572 - 6
Construction of a stable attenuated Shigella sonnei DeltavirG vaccine strain, WRSS1, and protective efficacy and immunogenicity in the guinea pig keratoconjunctivitis model; Hartman AB et al.; Construction of a stable Shigella sonnei vaccine has been complicated by the instability of the virulence phenotype caused by the spontaneous loss of the invasion plasmid . To select a suitable candidate for vaccine construction, 16 S . sonnei strains were screened for stability of the virulence phenotype . A stable strain, S . sonnei Mosely, was selected for further work . pDeltavirG2, a deletion derivative of the virG gene in the sacB suicide vector pCVD442, was used to generate an S . sonnei virG deletion strain, WRSS1, which was invasive in HeLa cells but negative in the Sereny test . WRSS1 was found to be both immunogenic and protective in the guinea pig keratoconjunctivitis model.

Infect Immun, 1998 Sep, 66(9), 4484 - 90
Alteration of HLA-B27 peptide presentation after infection of transfected murine L cells by Shigella flexneri; Boisgerault F et al.; Shigella flexneri is a triggering agent for reactive arthritis in HLA-B27-susceptible individuals . Considering the intracellular multiplication of bacteria, it seems likely that bacterial peptides may be presented by the major histocompatibility complex (MHC) class I pathway . To examine this hypothesis, we infected HLA-B*2705- and/or human beta2-microglobulin-transfected murine L-cell lines with M90T, an invasive strain of S . flexneri . Bacterial infection induced no detectable modifications in the biosynthesis and expression level of HLA-B27, as assessed by immunoprecipitation, Northern blot analysis, and flow cytometry . Using confocal microscopy, we observed that bacterial infection induced a clustering of HLA-B27 molecules during macropinocytosis and before bacterial dissemination from cell to cell . Peptides naturally bound to HLA-B27 molecules were acid eluted from infected cells and separated by high-performance liquid chromatography . Major differences were observed in high-performance liquid chromatography profiles and in the nature of peptides presented following bacterial infection . Although most of the antigens presented were not accessed by Edman degradation, we obtained two sequences partially homologous to bacterial proteins . These peptides lacked the major HLA-B27 peptide anchor (Arg) at position 2, and one had an unusual length of 14 amino acids . These data suggest that alterations in the peptide presentation by HLA-B27 occur during infection, which could be relevant to the pathogenesis of HLA-B27-related arthritis.

Infect Immun, 1998 Sep, 66(9), 4237 - 43
Requirement of the Shigella flexneri virulence plasmid in the ability to induce trafficking of neutrophils across polarized monolayers of the intestinal epithelium; McCormick BA et al.; Attachment of an array of enteric pathogens to epithelial surfaces is accompanied by recruitment of polymorphonuclear leukocytes (PMN) across the intestinal epithelium . In this report, we examine how Shigella-intestinal epithelium interactions evoke the mucosal inflammatory response . We modeled these interactions in vitro by using polarized monolayers of the human intestinal epithelial cell line, T84, isolated human PMNs, and Shigella flexneri . We show that Shigella attachment to T84-cell basolateral membranes was a necessary component in the signaling cascade for induction of basolateral-to-apical directed transepithelial PMN migration, the direction of PMN transepithelial migration in vivo . In contrast, attachment of Shigella to the T84-cell apical membrane failed to stimulate a directed PMN transepithelial migration response . Importantly, the ability of Shigella to induce PMN migration across epithelial monolayers was dependent on the presence of the 220-kb virulence plasmid . Moreover, examination of Shigella genes necessary to signal subepithelial neutrophils established the requirement of a functional type III secretion system . Our results indicate that the ability of Shigella to elicit transepithelial signaling to neutrophils from the basolateral membrane of epithelial cells represents a mechanism involved in Shigella-elicited enteritis in humans.

FEMS Microbiol Lett, 1998 Aug 1, 165(1), 159 - 65
Characterization of enteroinvasive Escherichia coli and Shigella strains by RAPD analysis; Bando SY et al.; Genetic variation of 33 enteroinvasive Escherichia coli (EIEC), 12 non-EIEC and 39 Shigella strains (representing the 4 species of this genus) was analyzed using the random amplified polymorphic DNA (RAPD) technique . Reproducible polymorphisms were generated and the combined data allowed us to construct a dendrogram using Jaccard's distance . Two main groups were obtained: one for Shigella and the other for EIEC and non-EIEC strains . The first group contained four clusters, one for each Shigella species . The second group contained one cluster for EIEC and another for non-EIEC strains . The main clusters encompassed many small clusters corresponding to different serotypes . It was possible to characterize each one of the 84 strains under study as well as the boundaries among Shigella species and between this genus and EIEC strains.

J Clin Microbiol, 1998 Sep, 36(9), 2404 - 7
Study of the relatedness of isolates of Shigella flexneri and Shigella sonnei obtained in 1986 and 1987 and in 1994 and 1995 from Hong Kong; Houang ET et al.; We used pulsed-field gel electrophoresis (PFGE) to study the genetic relatedness of 235 isolates of Shigella flexneri and Shigella sonnei collected in Hong Kong (97 isolates from 1986 and 1987 and 138 isolates from 1994 and 1995) . Altogether, 13 gels were run with bacteriophage lambda ladder DNA (Pharmacia) as an external reference in every sixth lane, standardized reagents and methods, and isolates randomized for species and years . For quantitative illustration of the relationships within a large body of isolates, computer-generated dendrograms were used to determine the number of isolates in pulsotypes at Dice coefficients of similarity of 75% (PT75) and 50% (PT50) . For S . flexneri, there was a significant difference in the distribution of isolates collected during the two periods in both PT75 and PT50, with 68% of isolates collected in 1994 and 1995 sharing a coefficient of similarity of >/=68% . For S . sonnei, a significant difference was observed in PT50 only . We also used Upholt's formula for an approximation of the fraction of nucleotide difference between isolates and Molecular Evolutionary Genetics Analysis to determine relative genetic distances . For both species, the relative genetic distances between isolates of the earlier collection period were significantly greater (P < 0.0001), i . e., they were further apart and therefore more diverse than those of the later period . We conclude that it is possible for a typical clinical laboratory to analyze a large amount of PFGE information on Shigella isolates obtained under controlled conditions . Such data analysis should enhance surveillance capabilities and give indications of further work to be done on various aspects of bacterial pathogenicity of the species.

Biochem Biophys Res Commun, 1998 Jul 30, 248(3), 669 - 72
Alterations in high molecular mass penicillin-binding protein 1 associated with beta-lactam resistance in Shigella dysenteriae; Ghosh AS et al.; Beta-lactam resistance poses a major problem in the chemotherapy of shigellosis caused by Shigella dysenteriae . Such resistance may arise from alterations in the affinities or amounts of the penicillin-binding proteins (PBPs) for beta-lactams, elaboration of beta-lactamases and reduced permeability across the outer membrane . The mechanisms of resistance in S . dysenteriae have not been studied in depth . This report describes a laboratory mutant, M19 which was characterized by the appearance of two high molecular mass PBPs of 84 (PBP1') and 82 kDa (PBP1") . M19 was more resistant to cefsulodin and cefoxitin . Resistance could be correlated with lower second order rate constants (k+2/K) of acylation . Moreover there was an overall two-fold increase in the relative amount of PBP1 (i.e . 1' + 1") in the mutant M19 compared to C152 . This is the first report which presents evidence of the involvement of altered high molecular mass PBPs in beta-lactam resistance in S . dysenteriae.

Zh Mikrobiol Epidemiol Immunobiol, 1998 May-Jun, (3), 63 - 7
{Genotyping of Shigella flexneri 2a strains isolated from patients with acute dysentery in St . Petersburg}; Stavitskaia EL et al.; Polymerase chain reaction with universal primers (UP-PCR) was used for the genotyping of 76 S.flexneri 2a cultures isolated from patients with acute dysentery in infectious and psychoneurological hospitals of St . Petersburg . 9 types were determined, and each of them included cultures with identical UP-PCR patterns . The population of the infective agent was more heterogeneous in psychoneurological hospitals where the change of types was registered in May-September 1995 . Some of these types were probably epidemic strains . UP-PCR was found to be a promising method increasing the efficiency of traditional epidemiological analysis.

Zh Mikrobiol Epidemiol Immunobiol, 1998 May-Jun, (3), 31 - 5
{Interhospital spread of Shigella flexneri 2A}; Kurakin ES; In this article the results of the study of regularities in the development of outbreak morbidity in shigellosis, caused by S.flexneri 2a, in hospitals are presented . The study was carried out with the use of the method of typing by the plasmid profile . The study showed the continuity of the epidemic process in the foci which appeared at intervals considerably exceeding the incubation period . The fact of the interhospital spread of S.flexneri 2a was established . The strain causing the disease was identified by the characteristic set of plasmids and their size . The possibility of reinfection of patients with S.flexneri 2a under hospital conditions was confirmed . The possibility of changes in the main transmission routes in the course of the spread of S.flexneri 2a infection in closed groups was pointed out.

J Antimicrob Chemother, 1998 Jul, 42(1), 99 - 102
Increasing frequency of mecillinam-resistant shigella isolates in urban Dhaka and rural Matlab, Bangladesh: a 6 year observation; Hossain MA et al.; A total of 14,915 shigella isolates obtained in 1991-1996 from patients attending the Dhaka (urban) and Matlab (rural) treatment centres of the International Centre for Diarrhoeal Disease Research, Bangladesh were examined for susceptibility to ampicillin, co-trimoxazole, nalidixic acid, mecillinam and ciprofloxacin by a disc diffusion method . There were no ciprofloxacin-resistant shigella isolates . The prevalence of resistance to ampicillin, co-trimoxazole and nalldixic acid varied between isolates . It increased to similar degrees in isolates from both Matlab and Dhaka . However, resistance to mecillinam was more prevalent among isolates from Matlab than from Dhaka . The increase in mecillinam-resistant shigellae in the community may have grave implications for the empirical treatment of shigellosis in Bangladesh and other developing countries.

Rev Biol Trop, 1989 Jun, 37(1), 69 - 73
{Aeromonas spp . and Plesiomonas shigelloides in bivalves, mud, and water from the Gulf of Nicoya, Costa Rica}; Rodriguez E et al.; Bivalves, mud, and surface water were collected at three different sites of the Gulf of Nicoya, Costa Rica, in search of Aeromonas spp . and Plesiomonas shigelloides . For their isolation, these bacteria were enriched in alkaline peptone water and streaked on MacConkey agar and on brilliant green bile inositol agar . This was followed by the biochemical tests necessary for their identification . Thirty-five strains of A . hydrophila, 58 of A . caviae, 43 of A . sobria, and 7 of P . shigelloides were isolated . None of these predominated nor was there any indication of a seasonal distribution along the 15 month's duration of the study . Seven strains of A . hydrophila and two of A . sobria showed the biochemical characteristics associated with toxin production (positive Voges-Proskauer and lysine decarboxylase tests) . These species are widely distributed in the gulf and there is risk of contracting an infection while bathing or when eating raw bivalves from this area.

J Bacteriol, 1998 Aug, 180(16), 4111 - 5
The tip of the hydrophobic hairpin of colicin U is dispensable for colicin U activity but is important for interaction with the immunity protein; Pilsl H et al.; The hydrophobic C terminus of pore-forming colicins associates with and inserts into the cytoplasmic membrane and is the target of the respective immunity protein . The hydrophobic region of colicin U of Shigella boydii was mutated to identify determinants responsible for recognition of colicin U by the colicin U immunity protein . Deletion of the tip of the hydrophobic hairpin of colicin U resulted in a fully active colicin that was no longer inactivated by the colicin U immunity protein . Replacement of eight amino acids at the tip of the colicin U hairpin by the corresponding amino acids of the related colicin B resulted in colicin U(575-582ColB), which was inactivated by the colicin U immunity protein to 10% of the level of inactivation of the wild-type colicin U . The colicin B immunity protein inactivated colicin U(575-582ColB) to the same degree . These results indicate that the tip of the hydrophobic hairpin of colicin U and of colicin B mainly determines the interaction with the corresponding immunity proteins and is not required for colicin activity . Comparison of these results with published data suggests that interhelical loops and not membrane helices of pore-forming colicins mainly interact with the cognate immunity proteins and that the loops are located in different regions of the A-type and E1-type colicins . The colicin U immunity protein forms four transmembrane segments in the cytoplasmic membrane, and the N and C termini face the cytoplasm.

Microbiology, 1998 Jul, 144 ( Pt 7), 1815 - 22
SepA, the 110 kDa protein secreted by Shigella flexneri: two-domain structure and proteolytic activity; Benjelloun-Touimi Z et al.; Shigellosis is characterized by a strong inflammatory response which is induced by bacteria invading the colonic mucosa . Characterization of a sepA mutant indicated that SepA, the major protein secreted by Shigella flexneri growing in laboratory media, might be involved in invasion and destruction of the host intestinal epithelium . The sequence of the first 500 residues of mature SepA (110 kDa) is homologous to that of the N-terminal region of IgA1 proteases . To investigate the potential proteolytic activity of SepA, the activity of the purified protein on a wide range of synthetic peptides was tested . SepA hydrolysed several of these substrates and the activity was inhibited by PMSF . Several peptides which were hydrolysed by SepA have been described as specific substrates for cathepsin G, a serine protease produced by polymorphonuclear leukocytes that was proposed to play a role in inflammation . However, unlike cathepsin G, SepA degraded neither fibronectin nor angiotensin I and had no effect on aggregation of human platelets . In addition, analysis of SepA hydrolysis by proteinase K suggested that the protein is composed of two domains of about 450 residues separated by a hinge region of 100 residues . The 47 kDa N-terminal domain was stable and endowed with proteolytic activity.

N Z Med J, 1998 Jun 26, 111(1068), 234 - 5
Antimicrobial resistances among Shigella in New Zealand; Brett MS; AIM: To determine the prevalence of antimicrobial resistances among recent isolates of Shigella in New Zealand . METHOD: A total of 107 Shigella isolates referred to the Institute of Environmental Science and Research from 20 hospital and community laboratories between January and June 1996 were tested by an agar dilution method . RESULTS: Shigella sonnei accounted for 70% of the isolates and S flexneri for 23% . Resistance to ampicillin and cotrimoxazole was detected in 42% and 57% of the isolates respectively, and combined ampicillin and co-trimoxazole resistance occurred in 30.8% of the isolates . The prevalence of cephalothin resistance was 5.6% . Resistance to cefotaxime, ciprofloxacid and gentamicin was not detected and 31.8% were sensitive to all agents tested . Ampicillin resistance was significantly more prevalent in S flexneri than S sonnei . CONCLUSIONS: The high prevalence of ampicillin and cotrimoxazole resistance indicates that ampicillin and cotrimoxazole are no longer useful for empirical treatment of shigellosis in New Zealand . The findings indicate a need to monitor the prevalence of antimicrobial resistances among Shigella and suggest that antimicrobial susceptibility testing might be needed to guide antimicrobial therapy.

Kansenshogaku Zasshi, 1998 Jun, 72(6), 615 - 20
{Usefulness of genotypic analysis for investigation of an epidemic of Shigella sonnei infections in Ooami-shirasato Town, Chiba Prefecture}; Uchimura M et al.; In March 1996, an epidemic of Shigella sonnei infection occurred in Ooamishira-sato Town, Chiba Prefecture . Colicine typing, antibiotic resistance patterns, plasmid profiles, pulsed-field gel electrophoresis (PFGE) and random amplified poly-morphic DNA (RAPD) were used for the investigation of the epidemic . Ninety-four isolates from patients exhibited three different colicine types and five different antibiotic resistance patterns . But the patterns of plasmid profile, PFGE and RAPD were uniform among the isolates with different colicine type and antibiotic resistance pattern . It is possible that these isolates belonged to a single bacterial clone and circulated through human to human.

Acta Paediatr Jpn, 1998 Jun, 40(3), 259 - 63
Diagnosis of bacterial enteric infections in children in Zambia; Nakano T et al.; BACKGROUND: The bacterial pathogens commonly responsible for diarrhea in children under the age of 5 in Zambia were identified and the most effective methods of diagnosis of such infections in laboratories with limited resources, such as those in developing countries, are recommended . METHODS: Stool samples were collected from children under the age of 5 years who visited the Diarrhoea Training Unit (DTU) of Zambia University Teaching Hospital in Lusaka, Zambia, between May 1992 and May 1993 . A total of 639 children were evaluated for the presence of bacterial infection using standard culture media . The prevalence of bacterial pathogens was compared with that reported from other developing countries . RESULTS: Pathogenic strains of Escherichia coli were isolated from 95 (14.9%) children, Shigella species from 65 (10.2%) children, and Vibrio cholerae from 21 (3.3%) children . The presence of visible blood in the feces was an early indicator of the presence of shigellosis . CONCLUSIONS: E . coli, Shigella species and Vibrio cholerae were the major causes of bacterial diarrhea in the Zambian children studied . Research is required to determine the prevalence of such enteropathogenic strains . The use of adequate diagnostic procedures is indispensable to appropriate management . The recommendations have been prepared as a manual for the identification of enteropathogenic bacteria to be used in laboratories with limited resources, such as in developing countries.

Acta Paediatr, 1998 Jun, 87(6), 627 - 30
Nutritional status and diarrhoeal pathogen in hospitalized children in Bangladesh; Dewan N et al.; We studied the relationship between nutritional status and infection due to specific enteropathogens in young children with diarrhoea . Overall, 26% of the children were severely underweight, 27% were severely wasted and 19% were severely stunted . Children with Shigellae and V . cholerae O1 were significantly more severely underweight, wasted and stunted than those with rotavirus diarrhoea (p < 0.0001) . Our results indicate that an effective nutrition programme for young children might have greater impact on diarrhoeal illness caused by Shigella and V . cholerae than by rotavirus diarrhoea.

Mol Microbiol, 1998 Jun, 28(6), 1211 - 22
Overexpression and topology of the Shigella flexneri O-antigen polymerase (Rfc/Wzy); Daniels C et al.; Lipopolysaccharides (LPS), particularly the O-antigen component, are one of many virulence determinants necessary for Shigella flexneri pathogenesis . O-antigen biosynthesis is determined mostly by genes located in the rfb region of the chromosome . The rfc/wzy gene encodes the O-antigen polymerase, an integral membrane protein, which polymerizes the O-antigen repeat units of the LPS . The wild-type rfc/wzy gene has no detectable ribosome-binding site (RBS) and four rare codons in the translation initiation region (TIR) . Site-directed mutagenesis of the rare codons at positions 4, 9 and 23 to those corresponding to more abundant tRNAs and introduction of a RBS allowed detection of the rfc/wzy gene product via a T7 promoter/polymerase expression assay . Complementation studies using the rfc/wzy constructs allowed visualization of a novel LPS with unregulated O-antigen chain length distribution, and a modal chain length could be restored by supplying the gene for the O-antigen chain length regulator (Rol/Wzz) on a low-copy-number plasmid . This suggests that the O-antigen chain length distribution is determined by both Rfc/Wzy and Rol/Wzz proteins . The effect on translation of mutating the rare codons was determined using an Rfc::PhoA fusion protein as a reporter . Alkaline phosphatase enzyme assays showed an approximately twofold increase in expression when three of the rare codons were mutated . Analysis of the Rfc/Wzy amino acid sequence using TM-PREDICT indicated that Rfc/Wzy had 10-13 transmembrane segments . The computer prediction models were tested by genetically fusing C-terminal deletions of Rfc/Wzy to alkaline phosphatase and beta-galactosidase . Rfc::PhoA fusion proteins near the amino-terminal end were detected by Coomassie blue staining and Western blotting using anti-PhoA serum . The enzyme activities of cells with the rfc/wzy fusions and the location of the fusions in rfc/wzy indicated that Rfc/Wzy has 12 transmembrane segments with two large periplasmic domains, and that the amino- and carboxy-termini are located on the cytoplasmic face of the membrane.

Carbohydr Res, 1998 Mar, 308(1-2), 229 - 38
Measurement of interglycosidic 3JCH coupling constants of selectively 13C labeled oligosaccharides by 2D J-resolved 1H NMR spectroscopy; Pozsgay V et al.; Tri-, tetra-, and penta-saccharide fragments of the O-specific polysaccharide of Shigella dysenteriae type 1 have been prepared in which a D-galactose residue of each oligosaccharide methyl glycoside derivative contains a 13C label at C-1 . The interglycosidic coupling constants (3JCH) of these 13C nuclei with the H-3 nuclei of the adjacent 2-acetamido-2-deoxy-D-glucose residues have been measured by two-dimensional, J-resolved 1H NMR spectroscopy . The magnitudes of these coupling constants indicate that the trisaccharide is conformationally different to the higher oligosaccharide homologs, in agreement with previous studies of 13C chemical shifts and 1JCH values.

J Appl Microbiol, 1998 May, 84(5), 709 - 14
Evaluation of the immunospecificity of the porin Om1 of Vibrio anguillarum serotype O1; Simon M et al.; Three methods of immunoanalysis (immunoblot, ELISA and dot-blot) were used to evaluate the immunospecificity of the antiserum against the porin Om1 of Vibrio anguillarum serotype O1 with respect to all the serotypes of V . anguillarum, different Vibrio species and other Gram-negative genera . In the immunoblot analysis of the outer membrane proteins, this antiserum cross-reacted with the main outer membrane protein (MOMP) of all the Vibrio strains studied but not with other genera, except Plesiomonas shigelloides . However, when analyses were performed using whole cells as antigens (ELISA and dot-blot), the antiserum was more specific for V . anguillarum.

Infect Immun, 1998 Aug, 66(8), 3918 - 24
Hemolysin-positive enteroaggregative and cell-detaching Escherichia coli strains cause oncosis of human monocyte-derived macrophages and apoptosis of murine J774 cells; Fernandez-Prada C et al.; Infection of human monocyte-derived macrophages (HMDM) and J774 cells (murine macrophage cell line) with several enteroaggregative and cytodetaching Escherichia coli (EAggEC and CDEC, respectively) strains demonstrated that some strains could induce macrophage cell death accompanied by release of lactate dehydrogenase activity and interleukin 1beta (IL-1beta) into culture supernatants . The mode of cell death differed in the two types of macrophages . Damage to macrophage plasma membrane integrity without changes in nuclear morphology resulted in cytolysis of HMDM . This mechanism of cell death has been previously described for virulent Shigella infection of HMDM and is termed oncosis . In contrast, infection of J774 cells by EAggEC and CDEC strains resulted in apoptosis . The presence of alpha-hemolysin (Hly) in EAggEC and CDEC strains appears to be critical for both oncosis in HMDM and apoptosis in J774 cells . Bacteria lacking Hly, including Hly- EAggEC strains as well as enterotoxigenic, enteropathogenic, and enterohemorrhagic E . coli strains, behaved like avirulent Shigella flexneri in that the macrophage monolayers were intact, with no release of lactate dehydrogenase activity or IL-1beta into the culture supernatants.

Infect Immun, 1998 Aug, 66(8), 3909 - 17
Inactivation of DsbA, but not DsbC and DsbD, affects the intracellular survival and virulence of Shigella flexneri; Yu J; In this study, three mutants, dsbA::kan, dsbC-kan, and dsbD-kan, of Shigella flexneri serotype 5 were constructed and characterized to investigate the role of the periplasmic thiol:disulfide oxidoreductases in pathogenicity . In gentamicin protection assays and the Sereny test, the dsbA mutant showed reduced virulence while the dsbC and dsbD mutants were similar to the wild type . That inactivation of dsbA was responsible for the reduced virulence was verified by complementation with the cloned wild-type gene in in vitro and in vivo assays . Despite the changed virulence behavior, the dsbA mutant could penetrate HeLa cells 15 min postinfection, consistent with the fact that it actively secretes Ipa proteins upon Congo red induction . Furthermore, the dsbA mutant was able to produce actin comets and protrusions, indicating its capacity for intra- and intercellular spread . However, a kinetic analysis of intracellular growth showed that the dsbA mutant barely grew in HeLa cells during a 4-h infection whereas the wild type had a doubling time of 41 min . Electron microscopy analysis revealed that dsbA mutant bacteria were trapped in protrusion-derived vacuoles surrounded by double membranes, resembling an icsB mutant reported previously . Moreover, the trapped bacteria appeared to be lysed simultaneously with the double membranes, resulting in characteristic empty vacuoles in the host cell cytosol . Thus, the attenuation mechanism for dsbA mutant appears to be more complicated than was previously suggested.

J Chemother, 1998 Jun, 10(3), 221 - 4
Transferable trimethoprim resistance in Shigella strains; Yuce A et al.; The susceptibility patterns of 35 Shigella isolates (16 S . flexneri, 14 S . dysenteriae and 5 S . sonnei) to trimethoprim (Tp) and various antibiotics including amoxycillin, amoxycillin-clavulanic acid, nalidixic acid, ciprofloxacin, ceftazidime and ceftriaxone, were investigated . Twenty-two (62.8%) strains were resistant to Tp with a minimal inhibitory concentration (MIC50) value of 512 mg/L . Only six isolates were amoxycillin resistant, to which clavulanic acid restored sensitivity in all of them . None of the isolates were resistant either to extended spectrum cephalosporins or to quinolones . Resistance to Tp was transferred from 7 of the 22 isolates (31.8%) to the recipient Escherichia coli K12 . Tp MIC values of the transconjugants were 512 mg/L . In no strain could amoxycillin resistance be transferred . Our results indicate that as the prevalence of transferable Tp resistance in Shigella isolates in Izmir is substantially high, alternative antimicrobial agents should be considered for empirical antibiotic therapy.

Risk Anal, 1998 Jun, 18(3), 309 - 28
Topics in microbial risk assessment: dynamic flow tree process; Marks HM et al.; Microbial risk assessment is emerging as a new discipline in risk assessment . A systematic approach to microbial risk assessment is presented that employs data analysis for developing parsimonious models and accounts formally for the variability and uncertainty of model inputs using analysis of variance and Monte Carlo simulation . The purpose of the paper is to raise and examine issues in conducting microbial risk assessments . The enteric pathogen Escherichia coli O157:H7 was selected as an example for this study due to its significance to public health . The framework for our work is consistent with the risk assessment components described by the National Research Council in 1983 (hazard identification; exposure assessment; dose-response assessment; and risk characterization) . Exposure assessment focuses on hamburgers, cooked a range of temperatures from rare to well done, the latter typical for fast food restaurants . Features of the model include predictive microbiology components that account for random stochastic growth and death of organisms in hamburger . For dose-response modeling, Shigella data from human feeding studies were used as a surrogate for E . coli O157:H7 . Risks were calculated using a threshold model and an alternative nonthreshold model . The 95% probability intervals for risk of illness for product cooked to a given internal temperature spanned five orders of magnitude for these models . The existence of even a small threshold has a dramatic impact on the estimated risk.

Infect Dis Clin North Am, 1998 Jun, 12(2), 285 - 303
Travelers' diarrhea . Epidemiology, prevention, and self-treatment; Ericsson CD; Risk factors for travelers' diarrhea include adventurous behavior, consumption of unclean water or food, and special hosts like those taking long acting H2 blockers . Approaches to prevention include education about risk factors, which often fails to lead to modification of risky behavior, and chemoprophylaxis with bismuth subsalicylate-containing compounds or antimicrobial agents . Chemoprophylaxis is generally discouraged except in special circumstances and in high-risk hosts . Self-treatment of travelers' diarrhea is successful in limiting the course of diarrhea and minimizing losses of vacation and business time . Current therapeutic options, in order of increasing effectiveness, include attapulgite, BSS-containing compounds, loperamide, antimicrobial agents such as the fluoroquinolones, and the combination of loperamide and an antimicrobial agent . Under study are a nonabsorbed antimicrobial agent, rifaximin, and a novel calmodulin inhibitor, zaldaride . Development and evaluation of vaccines against enterotoxigenic Escherichia coli and Shigella are proceeding apace but are not yet available for routine use.

J Bacteriol, 1998 Jul, 180(14), 3522 - 8
Identification of cpxR as a positive regulator essential for expression of the Shigella sonnei virF gene; Nakayama S et al.; virF is the master regulator which activates the virulence determinant genes of Shigella spp . such as ipaBCD and virG . We previously reported that expression of virF itself is regulated in a pH-dependent manner and that cpxA, a sensor of a two-component regulatory system, is involved in this regulation (S . Nakayama and H . Watanabe, J . Bacteriol . 177:5062-5069, 1995) . Disruption of cpxR, which has been thought to be the cognate response regulator of cpxA (J . Dong, S . Iuchi, H.-S . Kwan, Z . Lue, and E . C . C . Lin, Gene 136:227-230, 1993), abolished virF expression almost completely . Purified CpxR bound directly to the upstream region of virF . Binding capacity was enhanced when CpxR was phosphorylated by coincubation with acetyl phosphate in vitro . Furthermore, we observed that phosphorylated CpxR could activate virF transcription in vitro . These results clearly indicated that CpxR was an essential activator for virF expression and strongly suggested that the binding of phosphorylated CpxR to the target site upstream of the virF gene induced a direct activation of virF transcription.

Blood, 1998 Jul 15, 92(2), 558 - 66
Shiga toxin type 1 activates tumor necrosis factor-alpha gene transcription and nuclear translocation of the transcriptional activators nuclear factor-kappaB and activator protein-1; Sakiri R et al.; Shiga toxins (Stxs) produced by Shigella dysenteriae 1 and Escherichia coli have been implicated in the pathogenesis of bloody diarrhea, acute renal failure, and neurologic abnormalities . The pathologic hallmark of Stx-mediated tissue damage is the development of vascular lesions in which endothelial cells are swollen and detached from underlying basement membranes . However, in vitro studies using human vascular endothelial cells demonstrated minimal Stx-induced cytopathic effects, unless the target cells were also incubated with the proinflammatory cytokines tumor necrosis factor-alpha (TNF-alpha) or interleukin-1beta (IL-1bta) . These cytokines have been shown to upregulate the expression of the Stx-binding membrane glycolipid globotriaosylceramide (Gb3) . We show here that purified Stx1 induces TNF secretion by a human monocytic cell line, THP-1, in a dose- and time-dependent manner . Treatment of cells with both lipopolysaccharides (LPS) and Stx1 results in augmented TNF production . Treatment with the nontoxic Gb3-binding subunit of Stx1 or with an anti-Gb3 monoclonal antibody did not trigger TNF production . Northern blot analyses show that Stx1 causes increased TNF-alpha production through transcriptional activation . Increased levels of TNF-alpha mRNA are preceded by the nuclear translocation of the transcriptional activators NF-kappaB and AP-1 and the loss of cytoplasmic IkappaB-alpha . These data are the first to show that, in addition to direct cytotoxicity, Stxs possess cellular signaling capabilities sufficient to induce the synthesis of cytokines that may be necessary for target cell sensitization and the development of vascular lesions.

J R Coll Surg Edinb, 1998 Jun, 43(3), 160 - 2
Surgical lessons learned from the Shigella dysenteriae type I epidemic; Grant HW et al.; An epidemic of Shigella dysenteriae type I is spreading through Africa . It is a particularly infectious and virulent form of dysentery which can cause clinical confusion with other endemic diseases and may present to the surgeon as a result of its complications . A total of 140 children with Shigella dysenteriae type I presented to the paediatricians at King Edward VIII Hospital in 1995; 35 were referred to the surgeons because of abdominal tenderness, distension, peritonitis or perforation . Ten children underwent laparotomy--four for peritonitis and six for perforation . Of the four children with peritonitis, three had transmural colitis . Therefore laparotomy was only performed for objective evidence of perforation . Of the subsequent non-operated group with the clinical features of peritonitis, none developed further surgical problems in the acute phase and none died . It is suggested that surgery in the acute phase should be avoided unless there is evidence of perforation.

Biochemistry, 1998 Jun 30, 37(26), 9394 - 8
Shiga toxin attacks bacterial ribosomes as effectively as eucaryotic ribosomes; Suh JK et al.; Several pathogenic bacteria, including Shigelladysenteriae and certain strains of Escherichia coli, produce potent class 2 ribosome inhibiting proteins (RIPs) termed Shiga toxins (Stx) . The toxins are bipartite molecules composed of a single A chain (StxA) noncovalently associated with a pentamer of receptor-binding B subunits (StxB) . StxA and Stx1A from E . coli are protoxins . Proteolysis generates an A1 enzyme (28 kDa) and an A2 fragment (3 kDa), which remain bound, inactivating the enzyme, until a disulfide bond linking them is reduced . Efforts to express active recombinant Stx1A1 in the cytoplasm of E . coli were very difficult and led to the hypothesis that Stx1A1 is toxic to E . coli . We created the gene for a His-tagged Stx1A1 (cStx1A1) and expressed it in E . coli from a tightly controlled expression vector . About 1-2 mg of protein can be purified in a one-step isolation from 1 L of culture . cStx1A1, RTA, and PAP exhibited similar high toxicity against the Artemia ribosomes with IC50 values near 1 nM . Surprisingly, Stx1A1 had an IC50 of 0.8 nM against E . coli ribosomes, about the same as it had for Artemia ribosomes . This is about 250 times more active than PAP against bacterial targets, making Stx1A1 the most powerful RIP toxin presently known against E . coli ribosomes.

Kansenshogaku Zasshi, 1998 May, 72(5), 499 - 503
{Shigella dysenteriae strains possessing a new serovar (204/96) isolated from imported diarrheal cases in Japan}; Matsushita S et al.; Five Shigella strains isolated from stool cultures of imported diarrheal cases in Japan, did not react to any antisera of the established Shigella serovars . These strains had the typical biochemical characteristics of Shigella dysenteriae, and were biochemically identical . All strains were positive in the Sereny test and other tests for invasivness; these indicate that they can cause shigellosis in humans . The results of antigenic analysis revealed that they did not belong to any of the recognized or provisional serovars, and were serologically indistinguishable . They had the same drug-resistance pattern (CP.TC.SM.ABPC.ST) and plasmid-profile . Strain 96-204 is designated as the test strain for this new serovar.

East Afr Med J, 1998 Mar, 75(3), 160 - 1
Antibiotic sensitivity of endemic Shigella in Mbarara, Uganda; Legros D et al.; We analysed the chimio-sensitivity to antibiotics of endemic strains of Shigella isolated in Mbarara district, southwest Uganda . Twenty four strains were isolated, of which none was sensitive to cotrimoxazole and eight (33.4%, 95% CI {15.6-55.3}) to ampicillin, the two antibiotics recommended to treat dysentery during non epidemic periods in Uganda . Two isolates were resistant to nalidixic acid and none was resistant to the fluoroquinolones (Ciprofloxacin, Norfloxacin) . It is concluded that the results of this survey could be used to facilitate the elaboration of a new treatment protocol to treat endemic dysentery cases in Uganda.

Curr Microbiol, 1998 Jul, 37(1), 28 - 31
Incidence of non-01 Vibrio cholerae and Aeromonas spp . in fresh water in Araraquara, Brazil; Pasetto Falcao D et al.; The occurrence of Aeromonas spp., Vibrio cholerae, and Plesiomonas shigelloides in fresh water from various sources in Araraquara, State of Sao Paulo, Brazil was determined . Samples from ten distinct irrigation systems used in vegetable cultivation, from five distinct streams, from two reservoirs, from one artificial lake, and from three distinct springs were analyzed . All isolates were serotyped and tested for hemolysin, cytotoxin, heat-stable (ST) and heat-labile (LT) enterotoxins production; presence of plasmid; autoagglutination and drug resistance . V . cholerae isolates were also tested for cholera enterotoxin (CT) production, and Aeromonas isolates for suicide phenomenon . No P . shigelloides was found . V . cholerae non 01 was found in five irrigation water samples and in three stream samples . Aeromonas sp . were isolated in two samples of irrigation water, in three streams, and in one reservoir . All the V . cholerae and Aeromonas isolates were positive for beta-hemolysin production, and all Aeromonas isolates were positive for suicide phenomenon; cytotoxic activities were observed in two Aeromonas strains . Cholera enterotoxin was not found in eight V . cholerae non-01 isolates tested by the Y-1 mouse adrenal cell . All isolates were also negative for the other virulence markers . V . cholerae isolates were found to be sensitive to the majority of drugs tested, while Aeromonas strains presented multiple drug resistance.

Int J Food Microbiol, 1998 May 5, 41(1), 9 - 19
Revised model for aerobic growth of Shigella flexneri to extend the validity of predictions at temperatures between 10 and 19 degrees C; Zaika LL et al.; Although Shigella is a major foodborne pathogen, its growth in foods has received little attention . Growth of S . flexneri 5348 inoculated into commercially available sterile foods (canned broths, meat, fish, UHT milk, baby foods) was studied at 10 to 37 degrees C . S . flexneri was enumerated by surface-plating on Tryptic Soy Agar and growth curves were fitted by means of the Gompertz equation . Observed growth kinetics values and values calculated using a previously developed response surface model compared favorably for growth at 19 to 37 degrees C, but not at < 19 degrees C . To refine the model, additional data were collected for growth at 10 to 19 degrees C . A total of 844 tests in BHI broth, representing 197 variable combinations of temperature (10-37 degrees C), pH (5.0-7.5), NaCl (0.5-5.0%) and NaNO2 (0-1000 ppm) was used for the revised model . The revised model, developed in BHI, gave significantly better agreement of calculated growth kinetics values with those observed in foods at 10 to 19 degrees C.

Aust N Z J Ophthalmol, 1998 May, 26(2), 161 - 3
Congenital endophthalmitis following maternal shellfish ingestion; Marshman WE et al.; PURPOSE: To highlight an unusual organism causing a unilateral endophthalmitis by transplacental spread . METHOD: We report a case of Plesiomonas shigelloides endophthalmitis, presenting in a newborn, with co-existing septicaemia and meningitis.There was a significant maternal history of diarrhoea associated with the ingestion of oysters 2 weeks prior to delivery . RESULT: The endophthalmitis was treated with parenteral antibiotics and topical mydriatics with complete resolution, although subsequent assessment of the affected eye suggests a poor visual outcome . CONCLUSION: Endophthalmitis in the newborn is an unusual clinical finding and usually presents with other manifestations of bacteraemia . Plesiomonas shigelloides is fortunately an infrequent cause of neonatal infection, but is associated with a high degree of morbidity and mortality . We postulate that this neonate acquired P . shigelloides via the transplacental route, and suggest that this organism be included in the list of 'other' causes of transplacental infection that has been abbreviated to 'O' in the acronym 'TORCH'.

DNA Res, 1998 Feb 28, 5(1), 11 - 4
Identification of the region required for monomerization of the rolling circle plasmid pKYM; Yasukawa H et al.; Plasmid pKYM, isolated from the gram-negative bacterium Shigella sonnei, is a small multicopy plasmid which replicates by a rolling circle mechanism . The formation of multimers has been observed in a derivative of pKYM which lost a part of the origin region, and the loss of the monomerization mechanism would have led to these multimers . By analyzing the constructs of several mutants, we discovered that a DNA region required for monomerization was present upstream of the RepK binding site in the replication origin . As either of the T-rich sequence or the inverted repeat sequences which were seen in that region have been lost in the multimer-forming plasmids, these sequences may be necessary for monomerization.

FEMS Microbiol Lett, 1998 May 15, 162(2), 303 - 9
Two highly related regulatory proteins, Shigella flexneri VirF and enterotoxigenic Escherichia coli Rns, have common and distinct regulatory properties; Porter ME et al.; The Rns protein of enterotoxigenic Escherichia coli (ETEC) and the VirF protein of Shigella flexneri are members of the AraC family of transcription regulators . Rns is required for positive activation of the CS1 fimbrial genes, while VirF is a positive regulator of an invasion gene regulon . The amino acid sequences of the proteins are 36% identical, and both proteins activate transcription in response to increases in temperature . Here, we show that Rns is capable of complementing fully a null mutation in the S . flexneri virF gene . However, the VirF protein cannot replace Rns as an activator of CS1 gene expression in ETEC . This failure is not due to the absence from ETEC of a co-factor required by VirF since it also occurs when the CS1 system is moved into an S . flexneri genetic background . Nor is it a function of growth medium composition or a failure in virF gene expression . Instead, these findings point to important differences in the mechanisms by which these related transcription factors regulate gene expression in Gram-negative pathogens.

FEMS Microbiol Lett, 1998 May 15, 162(2), 201 - 6
Novel metallo beta-lactamase mediated by a Shigella flexneri plasmid; O'Hara K et al.; Novel carbapenem-hydrolyzing beta-lactamase (newly named MET-1) encoded on a transferable plasmid pMS390 from Shigella flexneri JS19622 was purified . The molecular weight was 28,000 by SDS-PAGE and the isoelectric point was higher than 9.3 . This beta-lactamase favorably hydrolyzed classical cephalosporins and oxyimino-cephalosporins rather than penicillins and carbapenems, but did not hydrolyze monobactams . The enzymatic activity was inhibited by EDTA, and the enzyme was found to contain two moles of zinc per mole of enzyme protein by means of atomic absorption spectrophotometry . These results indicated that the enzyme is a zinc beta-lactamase which differs from known metallo beta-lactamases, especially in its cephalosporinase-type substrate profile.

Antimicrob Agents Chemother, 1998 Jun, 42(6), 1476 - 83
Delivery of the non-membrane-permeative antibiotic gentamicin into mammalian cells by using Shigella flexneri membrane vesicles; Kadurugamuwa JL et al.; We developed a model to test whether non-membrane-permeative therapeutic agents such as gentamicin could be delivered into mammalian cells by means of bacterial membrane vesicles . Many gram-negative bacteria bleb off membrane vesicles (MVs) during normal growth, and the quantity of these vesicles can be increased by brief exposure to gentamicin (J . L . Kadurugamuwa and T . J . Beveridge, J . Bacteriol . 177:3998-4008, 1995), which can be entrapped within the MVs . Gentamicin-induced MVs (g-MVs) were isolated from Shigella flexneri and contained 85 +/- 2 ng of gentamicin per microgram of MV protein . Immunogold electron microscopic labeling of thin sections with antibodies specific to S . flexneri lipopolysaccharide (LPS) demonstrated the adherence and subsequent engulfment of MVs by the human Henle 407 intestinal epithelial cell line . Further incubation of g-MVs with S . flexneri-infected Henle cells revealed that the g-MVs penetrated throughout the infected cells and reduced the intracellular pathogen by approximately 1.5 log10 CFU in the first hour of incubation . Antibiotic was detected in the cytoplasms of host cells, indicating the intracellular placement of the drug following the penetration of g-MVs . Soluble antibiotic, added as a fluid to the tissue culture growth medium, had no effect on intracellular bacterial growth, confirming the impermeability of the cell membranes of the tissue to gentamicin . Western blot analysis of MVs with S . flexneri Ipa-specific antibodies demonstrated that the invasion protein antigens IpaB, IpaC, and IpaD were present in MVs . Being bilayered, with outer faces composed of LPS and Ipa proteins, these MVs were readily engulfed by the otherwise impermeable membranes and eventually liberated their contents into the cytoplasmic substance of the host tissue.

Microbiol Immunol, 1998, 42(4), 259 - 64
Epidemiologic study of Shigella sonnei from sequential outbreaks and sporadic cases using different typing techniques; Matsumoto M et al.; We noted that eight outbreaks of Shigella sonnei from an unknown source occurred sequentially in Aichi Prefecture, Japan, between October 1992-June 1993 . For comparative purposes we analyzed 53 outbreak-related isolates of Shigella sonnei using different subtyping methods and studied the epidemiology of the outbreaks . It appeared from our study that DNA-based techniques such as plasmid typing and pulsed-field gel electrophoresis (PFGE) were more useful tools for subtyping Shigella sonnei than colicin typing and the antimicrobial susceptibility test . Moreover, according to PFGE analysis, four genetically related isolates of Shigella sonnei were responsible for the eight sequential outbreaks . To further investigate the epidemiology of outbreaks, 58 sporadic isolates of Shigella sonnei from overseas travelers with shigellosis during the same period were also examined . We found that some sporadic isolates from travelers in Asia were genetically related to those of the outbreak-related isolates, indicating that genetically related isolates prevailed in Asia during this period, probably because of the extensive movement of people or food.

Kansenshogaku Zasshi, 1998 Apr, 72(4), 365 - 70
{Mechanism of resistance of Shigella flexneri 2a resistant to new quinolone antibiotics}; Oonaka K et al.; A Shigella flexneri 2a strain, which did not respond clinically or in laboratory tests to treatment with new quinolone derivatives, was isolated for the first time in Japan from a patient admitted for diarrhea to a Tokyo hospital . The mechanism of resistance was examined by sequencing the quinolone resistance determining region (QRDR) of the gyrA (a quinolone target enzyme) gene and by comparing the active efflux mechanisms of two strains isolated from this patient (before hospitalization and after tosufloxacin treatment) and one strain isolated from a patient with secondary infection with that of the standard strain ATCC 29903 . DNA sequencing revealed that two amino acid substitutions, namely, Ser (TCG)-83-->Leu (TTG) and Asp (GAC)-87-->Gly (GGC), had occurred in the gyrA of all 3 strains isolated from the patients . Examination of the accumulation of antibiotics in these 3 strains revealed that the strain isolated after tosufloxacin treatment had the highest resistance to tosufloxacin, and exhibited decreased accumulation of tosufloxacin in the bacterial cells discharged after 5 days of treatment with this antibiotic . However, accumulation was restored by addition of a proton-pump inhibitor . These results suggest that the strains isolated from the inpatient and the patient with secondary infection acquired resistance due to dual gyrA mutation induced by treatment with new quinolone antibiotics . Furthermore, in addition to this dual mutation, the active efflux mechanism also appears to be associated with resistance in bacteria that have been exposed to tosufloxacin.

EMBO J, 1998 May 15, 17(10), 2894 - 903
Induction of type III secretion in Shigella flexneri is associated with differential control of transcription of genes encoding secreted proteins; Demers B et al.; Shigella, the etiological agent of human bacillary dysentery, invades the colonic epithelium where it induces an intense inflammatory response . Entry of Shigella into epithelial cells involves a type III secretion machinery, encoded by the mxi and spa operons, and the IpaA-D secreted proteins . In this study, we have identified secreted proteins of 46 and 60 kDa as the products of virA and ipaH9.8, respectively, the latter being a member of the ipaH multigene family . Inactivation of virA did not affect entry into epithelial cells . Using lacZ transcriptional fusions, we found that transcription of virA and four ipaH genes, but not that of the ipaBCDA and mxi operons, was markedly increased during growth in the presence of Congo red and in an ipaD mutant, two conditions in which secretion through the Mxi-Spa machinery is enhanced . Transcription of the virA and ipaH genes was also transiently activated upon entry into epithelial cells . These results suggest that transcription of the virA and ipaH genes is regulated by the type III secretion machinery and that a regulatory cascade differentially controls transcription of genes encoding secreted proteins, some of which, like virA, are not required for entry.

EMBO J, 1998 May 15, 17(10), 2767 - 76
Neural Wiskott-Aldrich syndrome protein is implicated in the actin-based motility of Shigella flexneri; Suzuki T et al.; Shigella, the causative agent of bacillary dysentery, is capable of directing its own movement in the cytoplasm of infected epithelial cells . The bacterial surface protein VirG recruits host components mediating actin polymerization, which is thought to serve as the propulsive force . Here, we show that neural Wiskott-Aldrich syndrome protein (N-WASP), which is a critical target for filopodium formation downstream of Cdc42, is required for assembly of the actin tail generated by intracellular S.flexneri . N-WASP accumulates at the front of the actin tail and is capable of interacting with VirG in vitro and in vivo, a phenomenon that is not observed in intracellular Listeria monocytogenes . The verprolin-homology region in N-WASP was required for binding to the glycine-rich repeats domain of VirG, an essential domain for recruitment of F-actin on intracellular S.flexneri . Overexpression of a dominant-negative N-WASP mutant greatly inhibited formation of the actin tail by intracellular S.flexneri . Furthermore, depletion of N-WASP from Xenopus egg extracts shut off Shigella actin tail assembly, and this was restored upon addition of N-WASP protein, suggesting that N-WASP is a critical host factor for the assembly of the actin tail by intracellular Shigella.

J Bacteriol, 1998 Jun, 180(11), 2983 - 6
Escherichia coli clone Sonnei (Shigella sonnei) had a chromosomal O-antigen gene cluster prior to gaining its current plasmid-borne O-antigen genes; Lai V et al.; O antigen is part of the lipopolysaccharide present in the outer membrane of gram-negative bacteria . The surface-exposed O antigen is subject to selection by the host immune system, which may account for the maintenance of many different O-antigen forms . Characteristically, all genes specific to O-antigen synthesis are clustered in a region close to the his and gnd genes on the chromosome of Escherichia coli and related species . Shigella sonnei, essentially a clone of E . coli (E . coli clone Sonnei), is an important human pathogen and is unusual in that its O-antigen gene cluster is located on a plasmid . Our results suggest that it once had a normal chromosomal O-antigen gene cluster which has been largely deleted . We suggest that the O antigen encoded by the plasmid-borne genes offered a selective advantage in adapting to a new environment and that the chromosomal O-antigen genes were eventually inactivated . We also identified, by PCR and sequencing, a potential ancestor of E . coli Sonnei among the 166 known E . coli serotype strains.

Rev Soc Bras Med Trop, 1998 May-Jun, 31(3), 263 - 70
{Multiple antibiotic resistance mediated by R plasmid in Shigella flexneri strains isolated in the northeast of Brazil}; Sidrim JJ et al.; In Shigella strains were studied the molecular mechanism that mediated the multiply antibiotic-resistance . Twenty-six strains of Shigella flexneri were utilised in this investigation . These strains were submitted to disk diffusion test, mating experiments and plasmid isolation . In relation to antibiotics resistance standard it was observed that all Shigella flexneri strains were resistant to at least, three antibiotics tested . From twenty-six Shigella flexneri strains donors submitted to conjugation process, 34.6% (nine strains) resulted in variable frequency of transconjugants . From strains that conjugated, 100%, transferred the resistance factor acquainted with ampicillin . Being that, in all transconjugants which were observed, just one plasmid with 23.1 Kb was evidenced . This plasmid found in all strains was characterised as the cause of resistance to ampicillin.

J Womens Health, 1998 May, 7(4), 451 - 8
Differences in notifiable infectious disease morbidity among adult women--United States, 1992-1994; Niskar AS et al.; By 1990, all 50 states were using the Centers for Disease Control and Prevention (CDC) National Electronic Telecommunications System for Surveillance to report individual case data that included demographic information (without personal identifiers) about most notifiable diseases . This analysis of National Notifiable Diseases Surveillance System (NNDSS) data is useful for evaluating the distribution of reported notifiable infectious diseases among adult women by age and race . The number of cases of the 48 nationally notifiable infectious diseases reported among adult women (i.e., women > or = 15 years of age) were compiled for 1992-1994 . These data were then analyzed by age and race, and rates per 100,000 adult women were calculated . During 1992-1994, the 10 most commonly reported nationally notifiable diseases among adult women in the United States were, in descending order of frequency, gonorrhea, primary/secondary syphilis, acquired immunodeficiency syndrome (AIDS), salmonellosis, tuberculosis, hepatitis A, hepatitis B, shigellosis, Lyme disease, and hepatitis C/non-A non-B . Gonorrhea was the most commonly reported notifiable infectious disease for women of all ages, except those ages > or = 55 years, and for women of all races, except Asian/Pacific Islanders . Tuberculosis was the most commonly reported infectious disease among women of Asian/Pacific Island descent . Analysis of NNDSS data provides information about the relative reported burden of diseases among women of all ages and different races . This information may be used for targeting research, prevention, and control efforts.

J Clin Pathol, 1998 Feb, 51(2), 127 - 33
Assessment of invasion frequencies of cultured HEp-2 cells by clinical isolates of Helicobacter pylori using an acridine orange assay; Wilkinson SM et al.; AIMS: Recent studies suggest that Helicobacter pylori is an invasive enteropathogen . However, the efficiency with which this pathogen invades mammalian cells remains unknown . Therefore, this study was designed to investigate the invasion frequencies of HEp-2 cells by clinical strains of H pylori . METHODS: An acridine orange assay and cultured HEp-2 cell monolayers were used to determine the HEp-2 cell penetration frequencies of 17 clinical isolates and one American Type Culture Collection (ATCC) strain of H pylori, and single clinical strains of Yersinia enterocolitica, Shigella flexneri, and a non-invasive ATCC Escherichia coli strain . RESULTS: The acridine orange assay demonstrated that invasion frequencies of HEp-2 cells by all H pylori isolates were significant and, in most instances, exceeded those for the S flexneri strain and equalled those for the Y enterocolitica strain . The assay also showed that internalised H pylori organisms remained viable for at least six hours, the maximum time that bacteria and HEp-2 cells were co-incubated . CONCLUSIONS: These results may have important implications for treatment and prevention strategies for this gastric pathogen . Furthermore, the acridine orange assay may be useful for assessing, in vitro, the ability of conventional and newer antibiotics, alone or in combination, to kill intracellular H pylori organisms.

Infect Immun, 1998 Jun, 66(6), 3012 - 6
Clearance of Shigella flexneri infection occurs through a nitric oxide-independent mechanism; Way SS et al.; Nitric oxide (NO) generated by gamma interferon (IFN-gamma) activation of macrophages mediates the killing of many intracellular pathogens . IFN-gamma is essential to innate resistance to Shigella flexneri infection . We demonstrate that NO is produced following S . flexneri infection both in mice and in activated cells in vitro and that while it is able to kill S . flexneri in a cell-free system, it is not required for clearance of S . flexneri in either infected mice or in activated cells in vitro.

Arch Immunol Ther Exp (Warsz), 1997, 45(2-3), 235 - 42
Mechanism of antigenic variation in Shigella flexneri bacilli . IV . Role of lipopolysaccharides and their components in the sensitivity of Shigella flexneri 1b and its Lac+ recombinant to killing action of serum; Doroszkiewicz W; The effect of lipopolysaccharides (LPS) on the normal bovine serum (NBS) bactericidal reactions against mixture of S . flexneri 6713 1b strain and its 3b Lac+ recombinant were investigated . The serum killing of S . flexneri strains was inhibited, in different degree, by LPS extracted from either organisms . These properties were mainly due to LPS molecules; the lipid A fraction showed only low anticomplement activity, the polysaccharide fraction inhibited the killing activity of NBS in very low degree even at high concentration . These studies suggest that LPS composition especially the O-antigen polysaccharide chain contributes to the susceptibility of S . flexneri strains to NBS bactericidal activity.

J Infect Dis, 1998 May, 177(5), 1409 - 12
Enteroaggregative Escherichia coli strains as a cause of traveler's diarrhea: a case-control study; Gascon J et al.; To elucidate the importance of enteroaggregative Escherichia coli (EAggEC) strains as a cause of traveler's diarrhea in Spanish travelers, a prospective case-control 1:1 study was done in a university hospital clinic for travelers . EAggEC strains were isolated from 23 of 165 case-patients and from 4 of 165 controls (P = .0003) . In 16 patients, this was the only isolate recovered . Six of the EAggEC-positive isolates from the case-patients and 2 from the controls were positive for the enteroaggregative stable toxin type 1 gene . Other enteropathogens were also isolated . Shigella and enterotoxigenic E . coli strains showed significant differences between cases and controls (P = .0023 and P < .0001, respectively) . Geographic distribution of the EAggEC strains was homogeneous, and the clinical symptom, secretory diarrhea, did not differ statistically with that for the enterotoxigenic E . coli strains . EAggEC strains are a cause of secretory diarrhea in Spaniards traveling to developing countries.

J Infect Dis, 1998 May, 177(5), 1405 - 9
A prolonged outbreak of Shigella sonnei infections in traditionally observant Jewish communities in North America caused by a molecularly distinct bacterial subtype; Sobel J et al.; During 1994-1996, Shigella sonnei outbreaks occurred in 8 North American traditionally observant Jewish communities . These communities remain relatively separate from neighboring populations while maintaining close contact by travel with coreligionists in other cities . Epidemiologic investigations suggested community-to-community transmission via travel . Outbreak-related and control isolates of S . sonnei from each city were subtyped by pulsed-field gel electrophoresis (PFGE) to confirm an epidemiologic linkage between outbreaks . Forty-three (94%) of 46 outbreak-related isolates had closely related PFGE patterns, constituting a single subtype; 33 (94%) of 35 control isolates demonstrated unrelated PFGE patterns . Several patterns differing by < or = 3 bands were identified within the outbreak subtype; one of these accounted for 65% of outbreak isolates . Hence, a single subtype of S . sonnei caused an international outbreak involving 8 traditionally observant Jewish communities, but not neighboring populations, over a 2-year period, suggesting sustained propagation of the epidemic strain between communities.

Microbios, 1997, 92(371), 123 - 32
Release of interleukin-2 induced by a major antigenic outer membrane protein of Shigella dysenteriae type 1 in natural infection; Chakrabarti S et al.; An antigen specific modulation of peripheral blood lymphocyte function was examined in a patient-based study of Shigella dysenteriae type 1 infection . Interleukin-2 (IL-2) production by the peripheral blood mononuclear cells (PBMC) from Shigella-infected patients was correlated with the expression of host cellular immune responses . To evaluate the role of a 57 kD major antigenic outer membrane protein of S . dysenteriae 1 in the proliferation of PBMC and the production of IL-2, the in vitro blastogenic transformation assay was employed . The magnitude of the response was monitored morphologically as well as by the proliferation of the IL-2 dependent CTLL-2 cell line . The proliferation of the IL-2 dependent CTLL-2 cell line against PBMC culture fluids after exposure to the major antigen reflected the participation of functionally active T-lymphocytes in shigellosis patients . The precise quantitation of IL-2 concentration in such lymphocyte culture supernatants by immunoassay showed substantial production of IL-2.

Acta Paediatr Jpn, 1998 Apr, 40(2), 131 - 4
Comparative efficacy of cefixime and ampicillin-sulbactam in shigellosis in children; Helvaci M et al.; Shigellosis is still an important health problem in developing and underdeveloped countries as it is resistance to commonly used antibiotics including ampicillin, trimethoprim-sulfamethoxazole, chloramphenicol and tetracycline . Between May 1996 and October 1996, in a prospective randomized double-blind trial, cefixime was compared with ampicillin-sulbactam, both given orally for a period of 5 days, for the treatment of 80 children with acute bloody diarrhea . Forty patients were treated with a single-dose (8 mg/kg per day) of cefixime and the other 40 patients were given three doses of 100 mg/kg per day of ampicillin-sulbactam . After identification of Shigella organisms in stool specimens, nine patients in the cefixime receiving group and six patients in the ampicillin-sulbactam receiving group were excluded from the study . Differences in average age, sex and weight between the cefixime and ampicillin-sulbactam group were statistically meaningless (P > 0.05) . Fever and bloody diarrhea were universal features . The efficacy of cefixime was found to be better than ampicillin-sulbactam . Patients given cefixime had a shorter duration of fever (P < 0.01), shorter duration to disappearance of blood in the stool (P < 0.01), reduced time with diarrhea (P < 0.01) and reduced hospitalization time during the 5 study days (P < 0.01) than patients given ampicillin-sulbactam . No adverse effects were observed in the two study groups . This controlled trial showed good efficacy with cefixime compared to ampicillin-sulbactam in the treatment of shigellosis . Single-dose daily oral therapy with cefixime also showed good tolerability . Cefixime should be considered as an alternative drug of choice for shigellosis in children.

Z Geburtshilfe Neonatol, 1998 Jan-Feb, 202(1), 38 - 9
{Induction of uterine contractions by Shigella}; Lechner W et al.; The uterus-contracting properties of Shigellae in a clinically relevant dose of 10(5) organisms per ml was investigated in 17 uterine strips which where dissected during caesarean section from the lower uterine segment . A highly significant (p < 0.001) increase in uterine activity was observed.

Folia Med (Plovdiv), 1997, 39(4), 87 - 92
A study on the aerobic intestinal microflora in patients with salmonellosis and shigellosis; Stoicheva M et al.; Human intestinal microflora provides substantial protection of the body against intestinal pathogens and affects the course and outcome of intestinal infections with diarrheal syndrome . We studied the aerobic intestinal microflora in 120 patients with salmonellosis and 60 patients with shigellosis . Intestinal microflora was determined qualitatively assessing the relative share of E . coli and other aerobic representatives of the potentially pathogenic microorganisms . Disturbances of the aerobic intestinal microflora were found in 76% of the patients with salmonellosis and 80% of the patients with shigellosis in the acute stage of the disease . They occurred more commonly and were graver in the severe clinical forms of intestinal infections . Their frequency in convalescent bacterial carriers was greater.

Arzneimittelforschung, 1998 Feb, 48(2), 185 - 7
Effect of subinhibitory concentrations of some quinolones on a strain of Shigella dysenteriae type 1; Hostacka A et al.; Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed that the outer membrane proteins of a strain of Shigella dysenteriae exposed to four quinolone compounds (ciprofloxacin--CAS 85721-33-1, ofloxacin--CAS 83380-47-6, pefloxacin--CAS 70458-95-6, and enoxacin--CAS 74011-58-8) at subinhibitory concentrations of 1/4 or 1/8 of the minimal inhibitory concentration (MIC) showed no alterations as compared to the control . Also the hydrophobicity of the cell surface of the test strain was not affected after exposure to subinhibitory concentrations of the quinolones.

Proc Natl Acad Sci U S A, 1998 Mar 31, 95(7), 3943 - 8
"Black holes" and bacterial pathogenicity: a large genomic deletion that enhances the virulence of Shigella spp . and enteroinvasive Escherichia coli; Maurelli AT et al.; Plasmids, bacteriophages, and pathogenicity islands are genomic additions that contribute to the evolution of bacterial pathogens . For example, Shigella spp., the causative agents of bacillary dysentery, differ from the closely related commensal Escherichia coli in the presence of a plasmid in Shigella that encodes virulence functions . However, pathogenic bacteria also may lack properties that are characteristic of nonpathogens . Lysine decarboxylase (LDC) activity is present in approximately 90% of E . coli strains but is uniformly absent in Shigella strains . When the gene for LDC, cadA, was introduced into Shigella flexneri 2a, virulence became attenuated, and enterotoxin activity was inhibited greatly . The enterotoxin inhibitor was identified as cadaverine, a product of the reaction catalyzed by LDC . Comparison of the S . flexneri 2a and laboratory E . coli K-12 genomes in the region of cadA revealed a large deletion in Shigella . Representative strains of Shigella spp . and enteroinvasive E . coli displayed similar deletions of cadA . Our results suggest that, as Shigella spp . evolved from E . coli to become pathogens, they not only acquired virulence genes on a plasmid but also shed genes via deletions . The formation of these "black holes," deletions of genes that are detrimental to a pathogenic lifestyle, provides an evolutionary pathway that enables a pathogen to enhance virulence . Furthermore, the demonstration that cadaverine can inhibit enterotoxin activity may lead to more general models about toxin activity or entry into cells and suggests an avenue for antitoxin therapy . Thus, understanding the role of black holes in pathogen evolution may yield clues to new treatments of infectious diseases.

Scand J Infect Dis, 1997, 29(6), 631 - 2
A case of Plesiomonas shigelloides cellulitis and bacteraemia from northern Europe; Jonsson I et al.; Bacteremia caused by Plesiomonas shigelloides is a rare event, often associated with consumption of seafood and fresh or estuarine water in temperate or tropical climates . Most patients have showed underlying health disorders . Here we present a case of P . shigelloides septicaemia and cellulitis of the left hand associated with fish handling in Northern Sweden (65 degrees latitude north) . The patient, who suffered from multiple myeloma, recovered uneventfully after initial treatment with intravenous cefuroxime followed by a course of oral ciprofloxacin . P . shigelloides seems to be ubiquitous in freshwater world-wide and may cause invasive infections also in cold climate areas.

Parasitology, 1997, 115 Suppl, S79 - 87
Macrophage apoptosis in microbial infections; Hilbi H et al.; Upon infection with a pathogen, eukaryotic cells can undergo programmed cell death as an ultimate response . Therefore, modulation of apoptosis is often a prerequisite to establish a host-pathogen relationship . Some pathogens kill macrophages by inducing apoptosis and thus overcome the microbicidal arsenal of the phagocyte . Apoptotic macrophages, on the other hand, can elicit an inflammation by secretion of proinflammatory cytokines . Shigella flexneri, the aetiological agent of bacillary dysentery, induces apoptosis in macrophages which, in agony, specifically release mature interleukin-1 beta (IL-1 beta) . This cytokine attracts neutrophils (PMN) to the site of infection resulting in the massive colonic inflammation characteristic of bacillary dysentery . Shigellosis represents a paradigm of a proinflammatory apoptosis in a bacterial infection . The molecular link between apoptosis and inflammation is interleukin-1 beta converting enzyme (ICE) which is activated during macrophage apoptosis and binds to IpaB, a secreted Shigella protein.

Roum Arch Microbiol Immunol, 1996 Oct-Dec, 55(4), 305 - 12
Plasmid profile analysis and restriction enzyme analysis in characterizing Shigella flexneri isolates from an outbreak; Fagarasan S et al.; Shigella flexneri strains which are multiply resistant to antimicrobial agents were isolated from 11 children from an orphanage in Cluj-Napoca during an epidemiological investigation initiated by the Department of Epidemiology . Plasmid profile analysis and restriction endonuclease analysis were used in conjunction with biotyping, serotyping and antimicrobial susceptibility testing for identifying epidemiological related isolates . All strains were serotype 2a and with one exception all of them showed the same resistotype . Plasmid profile analysis differentiated S . flexneri isolate into four patterns, with two common plasmids of 3.5 and 1.9 kb . This study indicates that this outbreak was caused by at least two different strains of S . flexneri which were not differentiated by the classical technique-biotyping, serotyping and antimicrobial susceptibility pattern.

Mol Cell Biochem, 1998 Jan, 178(1-2), 261 - 8
Binding of Shigella to rat and human intestinal mucin; Rajkumar R et al.; Invasion of epithelial cells by Shigella is an early step in their pathogenesis . Adherence is generally presumed to be a prerequisite for invasion . This study examined the possibility of intestinal mucins serving as initial binding sites for clinical isolates of S . boydii and S . sonnei . The interactions of Shigella with rat and human small intestinal and colonic mucin were investigated . In solid phase binding assays, {35S} labelled Shigella did not show any preferential binding to rat/human small intestinal mucin or to rat colonic mucin . On the other hand, Shigella bound specifically to human colonic mucin in a concentration-dependent manner . This specific binding to human colonic mucin was not by weak hydrophobic interactions and could not be attributed to the presence of contaminating glycolipids in the mucin preparation . The human colonic mucin receptor was sensitive to periodate treatment suggesting the involvement of the carbohydrate portion of the mucin . Reduction and alkylation of mucin enhanced adherence probably by exposing buried binding sites . The monosaccharides present in mucins were ineffective as hapten inhibitors as was the lectin wheat germ agglutinin suggesting that the mucin receptor is a more complex one . This study identifies, for the first time, the presence of a specific Shigella-binding site on the carbohydrate portion of human colonic mucin, which is not present in rat colonic mucin or in rat/human small intestinal mucin.

Mol Cell Biochem, 1998 Jan, 178(1-2), 169 - 79
Shigella dysenteriae type 1 toxin induced lipid peroxidation in enterocytes isolated from rabbit ileum; Kaur T et al.; To evaluate the role of reactive oxygen species (ROS) in Shigella dysenteriae 1 toxin (STx) mediated intestinal infection, the ligated rabbit small intestinal loops were injected with STx . The enterocytes isolated from STx treated rabbit ileal loops had a significantly higher level of lipid peroxidation as compared to enterocytes isolated from control rabbit ileum . To study the role of second messengers in STx mediated intestinal damage, the in vivo and in vitro effects of modulators of lipid peroxidation of enterocytes were used . The presence of Ca2+-ionophore A23187 enhanced the extent of lipid peroxidation in enterocytes isolated from the control and STx treated rabbit ileum . However, 1-verapamil only marginally decreased the lipid peroxidation level of enterocytes isolated from STx treated rabbit ileum . The in vitro effect of modulators was in agreement with in vivo studies . Dantrolene significantly decreased the extent of lipid peroxidation of enterocytes isolated from STx treated rabbit ileum . PMA significantly increased the lipid peroxidation level of enterocytes isolated from control ileum . However, PMA could not further enhance the lipid peroxidation level of enterocytes isolated from STx treated rabbit ileum . The presence of H-7 significantly decreased the extent of lipid peroxidation of enterocytes isolated from STx treated rabbit ileum . In vitro effect of PMA and H-7 was in agreement with that of in vivo findings . The role of arachidonic acid metabolites, prostaglandins (PGs), in mediating STx induced lipid peroxidation was also studied . The presence of indomethacin (a PG synthesis inhibitor) significantly decreased the lipid peroxidation induced by STx . These findings suggest that lipid peroxidation induced by STx is mediated through cytosolic calcium . The increase in (Ca2+)i leads to activation of PKC . A significant decrease in the enterocyte levels of antioxidant enzymes superoxide dismutase, catalase and reduced glutathione in STx treated rabbit ileum as compared to control was seen . A significant decrease in vitamin E levels was also observed . This suggests that there is decreased endogenous intestinal protection against ROS in STx mediated intestinal infection which could contribute to enterocyte membrane damage that ultimately leads to changes in membrane permeability and thus to fluid secretion.

Appl Environ Microbiol, 1998 Apr, 64(4), 1242 - 5
PCR for detection of Shigella spp . in mayonnaise; Villalobo E et al.; The use of PCR to amplify a specific virA gene fragment serves as a highly specific and sensitive method to detect virulent bacteria of the genus Shigella and enteroinvasive Escherichia coli . Amplification of a 215-bp DNA band was obtained by using isolated genomic DNA of Shigella, individual cells of Shigella dysenteriae, and mayonnaise contaminated with S . dysenteriae . Moreover, a multiplex PCR with specific (virA) and bacterium-restricted (16S ribosomal DNA) primers generated an amplification product of approximately 755 bp for all bacteria tested and an additional 215-bp product for Shigella and enteroinvasive E . coli.

FASEB J, 1998 Apr, 12(6), 495 - 502
Double-stranded DNA can be translocated across a planar membrane containing purified mitochondrial porin; Szabo I et al.; The transport of genetic material across biomembranes is a process of great relevance for several fields of study . However, much remains to be learned about the mechanisms underlying transport, one of which implies the involvement of proteic DNA-conducting pores . Entry of genetic material into mitochondria has been observed under both physiological and pathological conditions . We report here that double-stranded DNA can move through a planar bilayer membrane containing isolated mitochondrial porin (voltage-dependent anion channel) . The transport is driven by the applied electrical field, and the presence of DNA is associated with a decrease of current conduction by the pores . The passage of DNA does not take place if the bilayer has not been doped with any protein or in the presence of both reconstituted porin and anti-porin antibody . Translocation does not occur if the bilayer contains Shigella sonnei maltoporin, gramicidin A channels, or a 30 pS anion-selective channel plus other proteins . These results show that mitochondrial porin is capable of mediating the transport of genetic material, revealing a new property of this molecule and further confirming the idea that DNA can move through proteic pores.

Carbohydr Res, 1997 Dec, 305(1), 93 - 9
Conformational stabilization of the altruronic acid residue in the O-specific polysaccharide of Shigella sonnei/Plesiomonas shigelloides; Batta G et al.; Complete assignments for the 1H- and the 13C-NMR spectra of the O-specific polysaccharide of S . sonnei/Plesiomonas shigelloides are reported . Evidence is presented that in this polysaccharide both pyranose residues exist preferentially in the 4C1 chair conformation and that the polysaccharide exists in the zwitterion form.

Microb Pathog, 1998 Feb, 24(2), 117 - 22
Inhibition of prokaryotic translation by the Shiga toxin enzymatic subunit; Skinner LM et al.; Shiga toxin, produced by Shigella dysenteriae serotype 1, is a member of the large family of ribosome-inactivating proteins (RIPs) which are primarily produced by plants . All RIPs are rRNA N-glycosidases which inactivate ribosomes through the removal of a specific adenine residue from the well-conserved aminoacyl-tRNA-accepting loop of rRNA . As a type II RIP, STX is believed to have little effect on prokaryotic ribosomes . However, we have demonstrated that over-expression of the STX enzymatic (A1) polypeptide which lacks a signal sequence caused a reduced rate of growth of its Escherichia coli host . Over-expression of the same StxA1 polypeptide with a catalytic site substitution had no effect on the growth of E . coli . In addition, purified StxA1 was an inhibitor of prokaryotic protein synthesis as assessed using an in vitro transcription and translation assay . The specific activity of StxA1 was significantly higher than ricin, which is another type II RIP, with both eukaryotic and prokaryotic translation systems .

Microb Drug Resist, 1998 Spring, 4(1), 57 - 60
Increasing incidence of antibiotic resistance in shigellas from humans in England and Wales: recommendations for therapy; Cheasty T et al.; Since 1983 the incidence of resistance to ampicillin in Shigella dysenteriae, Sh . flexneri, and Sh . boydii infections in England and Wales has increased from 42% to 65% and the incidence of resistance to trimethoprim, from 6% to 64% . Furthermore, of 1524 strains received in 1995-1996, 46% were resistant to both of these antimicrobials . For Sh . sonnei almost 50% of isolates were resistant to ampicillin or trimethoprim and 15% were resistant to both of these antimicrobials . These results demonstrate that if antibiotic therapy had been indicated for infections with Sh . dysenteriae, Sh . flexneri, and Sh . boydii, then treatment with either ampicillin or trimethoprim may have been ineffective in almost 50% of cases and for Sh . sonnei, in 15% of cases . It is concluded that if it is necessary to commence treatment before the results of laboratory-based sensitivity tests are available, the best options would be to use nalidixic acid for children and a fluoroquinolone antibiotic such as ciprofloxacin or ofloxacin, for adults.

Infect Immun, 1998 Apr, 66(4), 1342 - 8
An essential role for gamma interferon in innate resistance to Shigella flexneri infection; Way SS et al.; Shigella spp . are the major cause of bacillary dysentery worldwide . To identify immune effectors associated with protection of the naive host during infection, the susceptibility to pulmonary Shigella infection of each of various mouse strains that have a targeted deletion in a specific aspect of the immune system was evaluated . Our results demonstrate that mice deficient in gamma interferon are 5 orders of magnitude more susceptible to Shigella than are wild-type mice, whereas mice deficient in B and T lymphocytes or in T lymphocytes alone exhibit no difference in susceptibility . Significantly lower numbers of shigellae were recovered from immunocompetent compared with gamma-interferon-deficient mice after infection . While immunocompetent mice were able to clear a sublethal Shigella inoculum by day 5 postinfection, progressively increasing numbers of shigellae were cultured from the lungs of gamma interferon-deficient mice over the same period . Histopathology of the lungs from immunocompetent mice infected with a sublethal Shigella inoculum showed mild inflammatory changes, whereas the lungs from gamma interferon-deficient mice demonstrated progressively worsening acute bronchiolitis with ulceration . Further, the time to death in gamma interferon-deficient mice correlates inversely with the size of the Shigella inoculum . To identify the cellular source of gamma interferon, we infected SCID mice, T-cell-receptor-deficient mice, beige mice (a mouse strain deficient in natural killer {NK} cell activity), and mice depleted of NK cells using anti-asialo-GM1 . Each NK cell-deficient mouse strain exhibited a 10-fold-greater susceptibility to Shigella infection than immunocompetent mice . To test the protective effects of gamma interferon in vitro, survival of intracellular Shigella was examined in primary macrophages from wild-type mice, primary macrophages from gamma interferon-deficient mice, a macrophage cell line, and a fibroblast cell line . Following activation with gamma interferon, each cell type eradicated intracellular Shigella, while nonactivated macrophages fostered Shigella replication and nonactivated fibroblast cells fostered both Shigella replication and intercellular spread . Taken together, these data establish that NK cell-mediated gamma interferon is essential to resistance following primary Shigella infection.

Antimicrob Agents Chemother, 1998 Feb, 42(2), 440 - 3
Antimicrobial resistance in Shigella flexneri and Shigella sonnei in Hong Kong, 1986 to 1995; Chu YW et al.; Three hundred and thirty-three Shigella isolates obtained in 1986 to 1995 were tested for their susceptibilities to 19 antimicrobial agents . Nalidixic acid resistance had emerged in 59.6% of Shigella flexneri isolates during 1994 to 1995, with all tested resistant isolates having the mutation in gyrA encoding the Ser-83 alteration . Multiresistance (resistance to four or more agents) was more common in S . flexneri than in Shigella sonnei.

Cent Eur J Public Health, 1998 Feb, 6(1), 67 - 70
Characterization of Plesiomonas shigelloides from diarrheic children; Bravo L et al.; Infrastructure of 29 P . shigelloides strains isolated as the only positive finding from children with diarrhea (biochemical properties, antigenic structure, antigenic relationship to shigellae, ATB susceptibility and plasmids) were described . A big variety of 22 serovars in a relatively small number of strains was found, inclusive four new 0 (093, 094, 095 and 096) and one new H (H46) antigen . Some strains belonged to the so-called "Schubert antigenic scheme" the serovars of which come of surface water of small ponds in Germany.

P N G Med J, 1995 Dec, 38(4), 262 - 71
Diarrhoea in children in Papua New Guinea; Vince JD; National data for diarrhoeal disease in children can only be used as a very rough guide to morbidity and mortality, since they are based on incomplete reporting . Furthermore, when only one diagnosis per attendance, admission or cause of death is recorded, the true importance of diarrhoea as a cause of morbidity and mortality may be obscured . This may in part explain discrepancies between figures recorded in national and hospital statistics and those recorded in detailed studies of diarrhoeal admissions . While there appear to be quite marked differences in the relative importance of diarrhoea in different parts of the country, and while diarrhoeal disease is less of a scourge than in some other parts of the world, it is nevertheless a major cause of attendance at health facilities, the second or third most common cause of admission to many of the hospitals in the country, and a significant and often preventable cause of death . Limited studies of diarrhoeal aetiology indicate the major importance of rotavirus, Shigella and enteropathogenic and enterotoxigenic Escherichia coli . The control of diarrhoeal diseases in children is based not only on early and appropriate treatment, but also on preventive strategies . These include breastfeeding (which has saved the lives of many thousands of Papua New Guinean children and which is once again under threat), ensuring good host defence by good nutrition, immunization and early treatment of childhood illness, and ensuring satisfactory sanitation and hygiene . Increasing fluid intake to prevent dehydration remains the most important part of the early management of acute diarrhoeal disease . In the management of children with dehydration, UNICEF glucose-based oral rehydration therapy is widely available but not used as well as it should be . There are significant advantages in cereal-based oral rehydration solutions, and the use of such solutions, locally prepared, should be encouraged . Breastfeeding should be continued during episodes of diarrhoea, unless there is the specific contraindication of lactose intolerance . In all events the child's nutritional intake should be maintained and if possible increased during episodes of diarrhoea . There are specific indications for the use of antibiotics in the management of children with diarrhoea . They should not be used, and may be harmful, in the absence of these indications . Persistent diarrhoea--lasting more than 14 days--is associated with a high mortality and severe malnutrition . It is therefore important that children whose diarrhoea is prolonged for more than 7 days are managed appropriately, using the standard guidelinesPIP: The incidence of diarrhea tends to vary among Papua New Guinea's various populations and it remains unclear to what extent the country's children are plagued by such diseases . Controlling diarrheal diseases in children involves early and appropriate treatment, as well as prevention . Breast feeding, good nutrition, immunization, the early treatment of childhood illness, and maintaining proper sanitation and hygiene all help prevent the development of diarrheal disease . Fluid intake must be increased in children with diarrhea in order to prevent dehydration . This increase in fluid consumption is the most important part of the early management of acute diarrheal disease . While UNICEF's glucose-based oral rehydration therapy is widely available to manage dehydrated children, it is inadequately used . The use of locally prepared, cereal-based oral rehydration solutions should be encouraged . Furthermore, breast feeding should be continued during episodes of diarrhea unless there is a specific contraindication of lactose intolerance . The child's nutritional intake should nonetheless be maintained and, if possible, increased during episodes of diarrhea . Antibiotics should not be used to treat diarrhea in children unless there are specific indications for such use . Diarrheal episodes which last more than 14 days are associated with high mortality and severe malnutrition . It is therefore important for children with diarrhea of longer than 7 days to be managed appropriately according to standard guidelines .

Microb Pathog, 1997 Dec, 23(6), 357 - 69
Identification and molecular characterization of a 27 kDa Shigella flexneri invasion plasmid antigen, IpaJ; Buysse JM et al.; Shigella species and enteroinvasive Escherichia coli contain a core set of virulence genes whose coordinated expression results in the invasion of host colonic epithelial cells and the dysenteric syndrome . A number of virulence determinants are carried by the 230 kb invasion plasmid found in all virulent strains of Shigellae . Many of these invasion plasmid genes encode immunogens that are recognized by convalescent serum, including proteins that mediate the invasion (IpaB, IpaC, IpaD) and cell spreading (VirG or IcsA and IcsB) phenotypes . In this report, we describe the molecular characterization of a novel invasion plasmid antigen from Shigella flexneri, designated IpaJ . The ipaJ gene encodes a 780 bp open reading frame (ORF), separated from the ipaR (virB) stop codon by 944 bp . The predicted amino acid sequence for IpaJ revealed a consensus signal peptide for protein export . TnphoA mutagenesis of the ipaJ ORF confirmed the presence of export signal sequences in IpaJ . Unlike ipaBCDA genes, transcription analysis of ipaJ indicated that the gene is not expressed in a temperature-dependent fashion . The IpaJ protein was expressed and purified as a His6-tagged fusion protein that reacted with convalescent sera in Western blot analyses, confirming its identification as a Shigella immunogen . Construction and phenotypic characterization of ipaJ mutants in two serotypes of S . flexneri showed that the mutants were not compromised in their ability to invade cultured epithelial cells or to form plaques on BHK cell monolayers . In addition, the ipaJ mutants were Sereny positive indicating a capacity for intercellular dissemination; however, in the limited number of guinea-pigs tested, the keratoconjunctivitis reaction appeared attenuated .

Trans R Soc Trop Med Hyg, 1997 Nov-Dec, 91(6), 681 - 5
Gastric acid secretion and enteric infection in Bangladesh; Evans CA et al.; In developing countries many enteric infections are caused by acid-sensitive pathogens . Failure of the gastric acid barrier to infection has been reported in cholera but gastric acid secretion has been little studied in other enteric infections . We therefore studied basal and stimulated gastric acid in 185 Bangladeshi men admitted to hospital for the treatment of enteric infection . Patients with dysentery (amoebiasis, n = 24 and shigellosis, n = 19) and culture-negative diarrhoea (n = 69) had similar mean gastric acid levels (basal, 3-5 mmol/h; stimulated, 11-17 mmol/h), which remained stable in those patients studied throughout 12 weeks of convalescence . In contrast, patients with secretory diarrhoea caused by cholera or enterotoxigenic Escherichia coli (ETEC) had low gastric acid levels (P < 0.05 compared with other groups) (cholera, n = 34: basal mean 1.8 mmol/h {SD = 2.2}, stimulated mean 7.9 mmol/h {SD = 6.4}; ETEC, n = 39: basal mean 2.7 mmol/h {SD = 2.8}, stimulated mean 9.4 mmol/h {SD = 7.5}) . Cholera patients' gastric acid level rose during convalescence to similar levels to the dysentery patients' . Low gastric acid level was associated with severe disease in patients with cholera (P < 0.02) or ETEC (P < 0.05) . Gastric acid level fell with increasing age (P < 0.007) but this did not account for the differences between groups . Gastric acid levels were not associated with Giardia duodenalis or Strongyloides stercoralis co-infection, fever, use of tobacco, or chewing betel nut . Cholera and secretory diarrhoea caused by ETEC may, therefore, partly result from a reduction in gastric acid level which does not occur during dysentery . Factors which impair gastric acid secretion may predispose to diarrhoeal disease in developing countries.

Mol Cell Probes, 1997 Dec, 11(6), 427 - 32
Phylogenetic analysis and identification of Shigella spp . by molecular probes; Wang RF et al.; Oligonucleotide probes were used for identification of Shigella and analysis of the relationship between Shigella spp . and Escherichia coli . Probe-based PCRs shown cross-reactions from Shigella to E . coli . Probe-based 16S rRNA sequencing and phylogenetic analysis showed the four species of Shigella: Sh . dysenteriae, Sh . boydii, Sh . sonnei, and Sh . flexneri, formed a cluster with E . coli . Shigella flexneri and Sh . sonnei are even more similar to E . coli than to the other two Shigella species . These results confirmed an earlier recommendation that the four species of Shigella and E . coli should be classified as five sub-groups within a single species.

Arq Gastroenterol, 1997 Apr-Jun, 34(2), 112 - 20
{Scanning electronic microscopy of the small intestine in persistent diarrhea}; Costa Sde M et al.; Persistent diarrhea very often leads children to malnutrition . It has become the major cause of death resulting from acute diarrhea episodes in developing countries . In order to determine the ultrastructural alterations of the small bowel that occur in the syndrome, 16 infants with severe persistent diarrhea were studied, utilizing light microscopy and the scanning electron microscope . Stool and jejunal fluid samples were collected for culture, rotavirus, ova and parasite search . Enteropathogenic agents were isolated in stools from 11 (68.7%) patients and bacterial proliferation in the small bowel was detected in 11 (68.7%) patients . EPEC strains were the most frequent enteropathogenic agent isolated both from stool and jejunal fluid cultures . The stool cultures revealed the presence of the following enteropathogenic microorganisms: EPEC 0111 in four, EPEC 0119 in one, EAggEC in five, Shigella flexneri in two, and Shigella sonnei in one; mixed infections due to EAggEC associated with EPEC 0111 were seen in two patients . The light microscopic analysis revealed that 56.2% of the patients suffered moderate villous atrophy most frequently associated with effacement of the microvilli, intracytoplasmatic vacuolization, increased number of multivesicular bodied and increased lymphocytic and eosinophylic infiltration in the lamina propria . The scanning electron microscopic analysis revealed in all cases shortening of the villi and enterocyte derangements; very often there was a total lack and/or effacement of the microvilli; in half of the patients there was a mucoid material covering the enterocytes tightly adhered to the apical epithelium surface . The scanning ultrastructural alterations observed in these patients are probably due to an association of factors brought about by the presence of enteropathogenic microorganisms and the resulting food intolerance that is responsible for perpetuation of diarrhea.

Infect Dis Clin North Am, 1998 Mar, 12(1), 231 - 41
Emerging infectious diseases and travel medicine; Ostroff SM et al.; International movement of individuals, populations, and products is one of the major factors associated with the emergence and reemergence of infectious diseases as the pace of global travel and commerce increases rapidly . Travel can be associated with disease emergence because (1) the disease arises in an area of heavy tourism, (2) tourists may be at heightened risk because of their activities, or (3) because they can act as vectors to transport the agent to new areas . Examples of recently recognized diseases with relationship to travel include HIV, Legionnaire's disease, cyclosporiasis, Vibrio cholerae O139 Bengal, hantavirus, and variant Creutzfeldt-Jacob disease . Reemerging diseases include dengue fever, malaria, cholera, schistosomiasis, leptospirosis, and viral hemorrhagic fevers . In addition, tuberculosis, drug-resistant shigellosis, and cholera have been major concerns in refugee and migrant populations . Because of the unique role of travel in emerging infections, efforts are underway to address this factor by agencies such as the CDC, WHO, the International Society of Travel Medicine, and the travel industry.

BMJ, 1998 Feb 7, 316(7129), 422 - 6
Single dose vitamin A treatment in acute shigellosis in Bangladesh children: randomised double blind controlled trial; Hossain S et al.; OBJECTIVE: To evaluate the efficacy of a single large oral dose of vitamin A in treating acute shigellosis in children in Bangladesh . DESIGN: Randomised double blind controlled clinical trial . SETTING: Dhaka Hospital, International Centre for Diarrhoeal Disease Research, Bangladesh . SUBJECTS: 83 children aged 1-7 years with bacteriologically proved shigellosis but no clinical signs of vitamin A deficiency; 42 were randomised to treatment with vitamin A and 41 formed a control group . INTERVENTION: Children were given a single oral dose of 200,000 IU of vitamin A plus 25 IU vitamin E or a control preparation of 25 IU vitamin E . MAIN OUTCOME MEASURES: Clinical cure on study day 5 and bacteriological cure . RESULTS: Baseline characteristics of the subjects in the two treatment groups were similar . Significantly more children in the vitamin A group than in the control group achieved clinical cure (19/42 (45%) v 8/14 (20%); chi 2 = 5.14, 1 df, P = 0.02; risk ratio = 0.68 (95% confidence interval; 0.50 to 0.93)) . When cure was determined bacteriologically, the groups had similar rates (16/42 (38%) v 16/41 (39%); chi 2 = 0.02, 1 df, P = 0.89; risk ratio = 0.98 (0.70 to 1.39)) . CONCLUSIONS: Vitamin A reduces the severity of acute shigellosis in children living in areas where vitamin A deficiency is a major public health problem.

Eur J Biochem, 1998 Jan 15, 251(1-2), 534 - 7
Structural determination of the O-antigenic polysaccharide from the enterotoxigenic Escherichia coli O147; Hygge Blakeman K et al.; The structure of the O-antigenic polysaccharide from enterotoxigenic Escherichia coli O147 has been determined by NMR spectroscopy, and component and methylation analyses . The sequence of the sugar residues could be determined by NOESY and heteronuclear-multiple-bond-connectivity NMR experiments . It is concluded that the polysaccharide is composed of tetrasaccharide repeating units with the following structure: -->4)-beta-D-GalpA-(1-->3)-beta-D-GalpNAc-(1-->2)-alpha-L-Rhap+ ++-(1-->2)-alpha-L-Rhap-(1-->, where Rha represents 6-deoxymannose . The O-antigen of E . coli O147 is identical to the repeating unit of Shigella flexneri serotype 6 lipopolysaccharide, except that the latter contains an O-acetyl group at C3 of the rhamnosyl residue substituted by the N-acetylgalactosamine residue . Immunochemical analyses using a monoclonal antibody specific for the S . flexneri serotype 6 O-antigen showed an identical reactivity with both lipopolysaccharides.

Vojnosanit Pregl, 1997 Nov-Dec, 54(6), 565 - 70
{Reliabilty of the antibiogram and plasmid profile in detection of epidemic strains of Shigella sonnei}; Carevic B et al.; The aim of the study was to investigate and compare the type of resistance to antibiotics and plasmid profile of Shigellae sonnei isolated at epidemics of bacillary dysentery to determine which method was most reliable in the identification of epidemic strains of that bacteria . It was investigated 130 isolates of Sh . sonnei isolated from the stools of patients in 14 epidemics of bacillary dysentery in Yugoslav Army and citizens in period from 1987 to 1993 year . On the basis of identity of studied features of all isolates originated from one epidemic, epidemic strains of Sh . sonnei could be identified in 10 (71.4%) of 14 studied epidemics by means of plasmid profile, and in 8 (57.1%) epidemics by means of determination of resistance type to antibiotics . According to that, the method of plasmid profile analysis is more reliable in identification of Sh . sonnei epidemic strains compared to the method of determination of resistance type to antibiotics.

Sante, 1997 Sep-Oct, 7(5), 295 - 9
{Toxic food infection caused by Shigella flexneri in a military unit}; Cheftel E et al.; Food borne disease outbreaks have increased in France, but outbreaks caused by Shigella are rare, accounting for only 73 cases (1.62%) in 1993 . We report a food borne outbreak of Shigella flexneri strain 3 infection in a fire fighting unit in Paris between July 13th and 17th 1995 . Forty of the 127 firemen suffered symptoms including acute diarrhea (80%), fever (50%) and blood and mucus in stools (1 case, 2.5%) . Epidemiological investigation generated an unimodal epidemic curve suggesting a single source of contamination with no secondary cases . The median incubation period was between 43 hours 30 minutes and 51 hours 30 minutes . This is consistent with food borne Shigella infection . Statistical analysis of a case-control study implicated a mixed salad containing frozen shellfish from Asia (shrimps and mussels), served at lunch and dinner on July 13th 1995 . Shigella was not detected in this salad by microbiological methods . However, inoculation with as little as 100 organisms can cause symptoms . There was low-level contamination with Escherichia coli (940 cfu/g) due to cross-contamination . Shigella flexneri strain 3 was isolated from 11 of 18 stool cultures, but was never isolated from cultures of stools provided by the cooks . All isolates had identical antibiotic resistance profiles . They were resistant to ampicillin and ticarcillin, moderately sensitive to amoxicillin-clavulanic acid, highly sensitive to aminosides, erythromycin and quinolones . This identical pattern in all isolates suggests a common source of contamination . Plasmid-based multiple resistance is common in this organism . Therefore, antibiotics should only be given to patients with evident clinical signs of infection . Treatment was symptom-based in all but 4 patients, who had acute diarrhea and were treated with ciprofloxacin . This antibiotic is well tolerated, has rapid bactericidal action and significantly reduces the duration of the symptoms and excretion of Shigella, thus preventing secondary contamination with this highly infectious bacterium . Thus, food borne outbreaks of Shigella can occur in countries with a high standard of living because of the increase in mass catering (e.g . fast food restaurants) and importation of foodstuffs from developing countries with endemic shigellosis . This is a public health problem because of the morbidity and absenteeism due to illness, particularly when the patients are firemen responsible for emergency management.

Trans R Soc Trop Med Hyg, 1997 Sep-Oct, 91(5), 541 - 3
Epidemic dysentery in western Kenya; Malakooti MA et al.; This paper describes the epidemiology of a probable Shigella dysenteriae type 1 dysentery epidemic in western Kenya . A retrospective record review over 2 years of all cases of dysentery, amoebiasis and diarrhoea was carried out in 13 healthcare facilities in the Rarieda Division of Nyanza province . Of the 3301 cases recorded, 2191 were dysentery, giving a cumulative 2 years incidence rate for dysentery of 4% . The epidemic began in December 1994 and peaked in February 1995, coinciding with the very dry season . One location in the area had an overall attack rate of 9.3%, double that of other locations . Highest rates were in children aged < 5 years and in persons > 15 years old . S . dysenteriae type 1, with its increasing multiantibiotic resistance, is a continuing threat to the health of people in this region; this area may be suitable for intensive, prospective surveillance as a prelude to a Shigella vaccine trial.

Zh Mikrobiol Epidemiol Immunobiol, 1997 Nov-Dec, (6), 81 - 3
{The clinico-pathogenetic significance of the outer membrane proteins determined by the invasiveness plasmid in Flexner's shigellosis}; Bondarenko VM et al.; S . flexneri 2a outer membrane proteins of 38, 43, 62 and 78 kD, determined by the 140 mD invasiveness plasmid, serving as antigens and specific rabbit sera serving as antibodies were used for diagnosing S . flexneri infection in the enzyme immunoassay . The examination of 96 patients and 20 healthy donors showed the possibility of the detection of S . flexneri 2a protein invasins and antibodies to them at different periods of the disease . During the severe course of shigellosis a higher level of protein invasins in the blood serum of patients was established in comparison with that observed during the medium severe course . An elevated level of protein invasins in the blood serum was accompanied by a lower content of specific antibodies to them, which was probably due to the immunosuppressive action of the invasiveness plasmid, established in earlier experiments.

Zh Mikrobiol Epidemiol Immunobiol, 1997 Nov-Dec, (6), 65 - 8
{The immunosuppressive activity of Shigella sonnei differing by the presence of plasmid pSS120}; Borisova EV et al.; S . sonnei virulent strain containing invasiveness plasmid pSS120 was found to suppress delayed hypersensitivity (DH) to nonbacterial antigens . In the filtrate of the culture of this strain extracellular lipopolysaccharide (LPS), capable of inducing immunosuppressing activity in nonvirulent bacteria, was detected . S . sonnei strain having plasmid pSS120 whose invasiveness genes were blocked by the penetration of transposon Tn5, as well as strains containing no invasiveness plasmid, proved to be nonvirulent and could not inhibit immunosuppressing action . Extracellular LPS of nonvirulent strains had no inductive immunosuppressing activity . But it could be activated by chemical treatment . The results of this study indicate that the immunosuppressing action of S . sonnei LPS were linked with some genes of invasiveness plasmid pSS120.

Zh Mikrobiol Epidemiol Immunobiol, 1997 Nov-Dec, (6), 15 - 8
{Differences in the cellular surface of hybrid Escherichia coli K12 bacteria inheriting the rfb a3,4 gene of Shigella flexneri detected using atomic-force microscopy}; Iaminskii IV et al.; The cell surface of E . coli initial parent strain K12 J62 his-, chemotype Ra, and E . coli transductant strain K12 J62 his+, acquiring the capacity for synthesizing primary S-specific side chains of the lipopolysaccharide of S . flexneri O-antigen (group-specific factor 3,4), was studied by the method of atomic force microscopy . The comparative analysis of the images of the genetically linked pair of E.coli strains K12 J62 revealed the presence of essential differences in the topography of the surface structure of the compared bacterial cells, differing in their capacity for synthesizing S . flexneri factor 3,4 represented by repeating chains of L-rhamnose and N-acetyl-D-glucosamine.

Zh Mikrobiol Epidemiol Immunobiol, 1995 Jul-Aug, (4), 52 - 5
{The use of non-Euclidean metrics in epidemiological classifications}; Beliakov VD et al.; A non-Euclidean metric, stable to pollutions in sample data, for hierarchical cluster analysis in epidemiology is proposed . The simplicity of calculations permits its easy use in practice . On the basis of this metric the towns of Tula Province have been grouped according to morbidity rates in the shigellosis of Flexner and Sonne with the conjugated value of parameters.

J Clin Pathol, 1997 Jun, 50(6), 513 - 20
Quantitative assessment of IgG and IgA subclass producing cells in rectal mucosa during shigellosis; Islam D et al.; AIMS: To assess quantitatively both the morphological changes in the rectal mucosa and the changes in the relative frequency of IgA and IgG subclass producing cells found in the rectal mucosa during the acute phase of shigellosis and at convalescence . METHODS: Rectal biopsies from 25 Shigella dysenteriae 1 infected patients, 10 Shigella flexneri infected patients, and 40 uninfected controls were studied . Morphological changes in the mucosa were graded . The frequency of IgA and IgG subclass producing cells was assessed . In addition, immunostaining for secretory component in epithelial cells was analysed . RESULTS: Using morphological grading, 20% of the 35 patients studied had advanced inflammation (grade 3) in the acute phase of the disease . At convalescence, grade 1 inflammation was seen in 37% of the patients and in 10% of the controls . In the acute phase, as well as at convalescence, the number of IgA1, IgA2, and IgG2 positive cells was significantly higher than in the controls . The results were related to the histopathological degree of inflammation . CONCLUSIONS: In shigellosis, there is evidence for a prolonged humoral response residing in the mucosa long after the clinical symptoms have resolved, suggesting that shigellosis induces persisting mucosal humoral immune and inflammatory responses, remaining at least until 30 days after the infection.

Mol Gen Genet, 1997 Sep, 256(2), 93 - 103
Differential regulation of the plasmid-encoded genes in the Shigella flexneri virulence regulon; Porter ME et al.; Expression of the Shigella flexneri virulence gene regulon is controlled by multiple environmental signals acting through a regulatory cascade . The primary regulator is VirF, which is a positive regulator of the secondary regulatory gene virB and the structural gene icsA . The product of the virB gene in turn activates transcription of the genes coding for the invasion proteins, and for the type III secretion system which promotes export of the invasion proteins to the bacterial cell surface . The genes making up the regulon were studied in their native locations on the 230-kb virulence plasmid . Transcriptional control was detected at each level of the regulatory cascade . A gearing effect was detected upon thermal induction of transcription in the regulon, with the virF gene being induced by about two fold, virB by 10-fold and the structural genes by 100-fold . In addition, each gene studied displayed individual characteristics in its response to stimuli such as growth medium osmolarity, pH, variations in DNA superhelicity and the presence or absence of H-NS . The primary regulatory gene virF, displayed loose regulation under standard laboratory growth conditions . Regulation was tighter at the secondary regulator virB, while control of structural gene expression was tighter still . It is proposed that this regulatory pattern ensures that energetically wasteful expression of the structural genes under inappropriate conditions is avoided while allowing the regulatory genes to be expressed sufficiently under non-permissive conditions to ensure a rapid response to inducing conditions when these arise . Once induced, fine tuning of the response can be achieved through the different sensitivities of the individual regulon members to external stimuli.

Infect Immun, 1998 Feb, 66(2), 549 - 57
Intracellular multiplication and virulence of Shigella flexneri auxotrophic mutants; Cersini A et al.; We have constructed and analyzed a group of Shigella flexneri 5 auxotrophic mutants . The wild-type strain M90T was mutagenized in genes encoding enzymes involved in the synthesis of (i) aromatic amino acids, (ii) nucleotides, and (iii) diaminopimelic acid . In this way, strains with single (aroB, aroC, aroD, purE, thyA, and dapB) and double (purE aroB, purE aroC, purE aroD, purE thyA) mutations were obtained . Although the Aro mutants had the same nutritional requirements when grown in laboratory media, they showed different degrees of virulence in vitro and in vivo . The aroB mutant was not significantly attenuated, whereas both the aroC and aroD strains were severely attenuated . p-Aminobenzoic acid (PABA) appeared to be the main requirement for the Aro mutants' growth in tissue culture . Concerning nucleotides, thymine reduced the pathogenicity, whereas adenine did not . However, when combined with another virulence-affecting mutation, adenine auxotrophy appeared to potentiate that mutation's effects . Consequently, the association of either the purE and aroC or the purE and aroD mutations had a great effect on virulence as measured by the Sereny test, whereas the purE aroB double mutation appeared to have only a small effect . All mutants except the dapB strain seemed to move within a Caco-2 cell monolayer after 3 h of infection . Nevertheless, the auxotrophs showing a high intracellular generation time were negative in the plaque assay . Knowledge of each mutation's role in attenuating Shigella strains will provide useful tools in designing vaccine candidates.

J Clin Gastroenterol, 1997 Dec, 25(4), 595 - 601
Diarrheal epidemics among Rwandan refugees in 1994 . Management and outcome in a field hospital; Heyman SN et al.; We describe the clinical course and outcome of Rwandan refugees with cholera-like illness (n = 567) and clinical dysentery (n = 1,062) treated at the Israeli Army field hospital in the disaster region of Goma, Zaire, during the summer of 1994 . Vigorous fluid administration was the primary therapy, complemented with antibiotics for patients with presumed Shigella infection . Recovery rates were 94% and 96% for patients with cholera and dysentery, respectively . Mortality was substantially affected by comorbid conditions such as pneumonia and meningitis, which occurred in one-quarter of these patients . Infective, metabolic, and surgical complications (including three cases of intussusception) may have contributed to the deaths . The outcome of patients during diarrheal epidemics of cholera or bacillary dysentery may be favorable, even in disaster settings, if patients are evacuated promptly to medical facilities and appropriate therapy is instituted . We close with general observations on procedures to be followed in future epidemics of diarrheal diseases.

Acta Paediatr Jpn, 1997 Dec, 39(6), 681 - 4
Shigella gastroenteritis: clinical and epidemiological aspects, and antibiotic susceptibility; Yurdakok K et al.; The epidemiology and antibiotic sensitivity of Shigella species is changing worldwide . The present study surveyed the changing clinical and epidemiological characteristics and antibiotic susceptibility of Shigella gastroenteritis in Hacettepe University Ihsan Dogramaci Children's Hospital Diarrhoea Training and Treatment Unit between 1987 and 1994 . Among 19,812 diarrheal admissions, 618 (3.2%) patient files with Shigella gastroenteritis were reviewed retrospectively . Shigella soneii has been the commonest isolate (64%) since 1987 followed by S . flexineri (30%), S . boydii (5%) and S . dysenteriae (1%), the latter having not been isolated since 1990 . The isolate rate of S . sonnei has increased whereas the isolation rate of S . flexineri has decreased concomitantly since 1987 (r = -0.94; P < 0.001) . The majority of cases (365/618, 59%) were between 1 and 5 years of age . On admission bloody diarrhea was present in 36%, seizures in 3% and mild-moderate dehydration in 11% of cases . No case had severe dehydration . Only six patients (1%) were hospitalized . No deaths were recorded . The resistance rate for trimethoprim-sulfamethoxazole has increased from 27% in 1990 to 66% in 1994 (P < 0.05) while the resistance rate for ampicillin has decreased from 81% in 1987 to 32% in 1993 (P < 0.001) . Shigella flexineri was found to have higher resistance rates to ampicillin, sulbactam-ampicillin, chloramphenicol and gentamicin than S . sonnei . Changing Shigella sp . over the years may be the reason for the mild course of Shigella gastroenteritis . Further regional epidemiological studies are necessary to develop more appropriate management guidelines, especially in developing countries.

Microbiol Immunol, 1997, 41(11), 879 - 82
Evaluation of enzyme-labeled oligonucleotide probes to identify enterohaemorrhagic Escherichia coli; Yoh M et al.; Alkaline phosphatase-conjugated oligonucleotide probes were developed to detect the gene coding for Vero toxin 1 (VT1) and Vero toxin 2 (VT2) . Using these probes, 3 hr was enough to detect VT genes when suspicious colonies of enterohaemorrhagic Escherichia coli (EHEC) were obtained on an agar plate . The results of a hybridization test with 144 isolates of EHEC O157 and one isolate of Shigella dysenteriae Type 1 agreed exactly with the immunological detection, reversed passive latex agglutination (RPLA) test, of VTs in their culture supernatants . The sensitivity levels of these probes for the detection of VT genes were 100% . The specificity of these probes were also tested with a total of 1,002 strains of Escherichia coli other than EHEC and 8 strains of Shigella sp . other than Shigella dysenteriae Type 1; the results showed 100% specificity.

Microb Drug Resist, 1997 Winter, 3(4), 351 - 7
Involvement of a 70-kb plasmid of the epidemic Shigella dysenteriae type 1 (Dt66) strain in drug-resistance, lipopolysaccharide synthesis, and virulence; Datta S et al.; The present work characterizes a 70 kb plasmid of the Indian epidemic isolate Shigella dysenteriae type 1 strain Dt66 in relation to virulence and drug-resistance characters . Curing of the plasmids of Dt66 strain by acriflavine (AF) yielded seven groups of AF-cured derivatives . One group of derivatives containing 5 plasmids (70-2.5 kb) as against 6 (120-2.5 kb) in the wild type showed resistance to chloramphenicol, pivmecillinam, streptomycin, and tetracycline (CmrPivrSmrTcr) but sensitivity for ampicillin and nalidixic acid (AmsNals) . This derivative when used as donor in conjugation experiments with a plasmidless E . coli KL318 strain (AmsCmsPivsSmrTcsNalr) as recipient, transferred only its 70 kb plasmid into the recipient with concomitant transfer of the CmrPivr phenotype . Both the donor and the transconjugant exhibited a diffuse pattern of adherence and produced keratoconjunctivitis in guinea pigs . Transconjugants contained a 42 kDa lipopolysaccharide band which was absent in recipient . Moreover, both donor and transconjugants showed Congo red binding ability . The results suggest that the 70 kb plasmid of S . dysenteriae Dt66 strain encodes not only Cmr,Pivr character but also is associated with virulence-related characters such as Congo red binding, LPS-biosynthesis, HeLa cell adherence, and keratoconjunctivitis related to virulence.

Epidemiol Infect, 1997 Dec, 119(3), 293 - 8
Plasmid profiles of drug resistant Shigella boydii types 1-5, 8, 10, 12-14 from Ethiopia (1974-85); Gebre-Yohannes A et al.; Plasmid profile analysis by agarose gel electrophoresis was performed on 42 drug resistant strains of Shigella boydii serotypes 1-5, 8, 10, 12-14, collected between 1974 and 1985 from endemic cases of shigellosis in Ethiopia, and their Escherichia coli K12 transconjugants . Resistance factors (R factors) were further characterized by incompatibility testing . Patterns of small plasmids, less than 15 kb, were similar within each of the individual S . boydii serotypes . Plasmids of about 3.3-3.7 kb were found in all strains of serotypes 2 and 4 . Plasmids of about 4.3-4.6 kb were found in about 86% of strains . Serotypes 1, 2 and 3 were characterized by plasmids of about 5.6-5.7 kb . The 6.4-6.7 kb plasmid was found consistently in serotypes 1, 2, 3, 5, 8, 12 and 13 which were resistant to SSu or had an SSu resistance component in their phenotypes . Large plasmids (155-186 kb) were found in most S . boydii strains . Conjugative drug resistance plasmids, most often coding for three or less drugs, were found in about 26% of drug resistant strains . R-factors, coding for AT resistance (in types 2 and 8), and ASSuT resistance (in type 4), were compatible with all reference plasmids tested . Plasmids belonging to incompatibility groups X and N were found in serotypes 5 and 10, respectively.

Biochem Biophys Res Commun, 1998 Jan 6, 242(1), 54 - 6
Involvement of an efflux system in high-level fluoroquinolone resistance of Shigella dysenteriae; Ghosh AS et al.; Shigella dysenteriae represent one of the growing list of antibiotic-resistant bacteria . Quinolones are widely employed to treat shigellosis . However, quinolone resistance has already been reported, necessitating an understanding of the mechanisms of development of resistance . We demonstrate that high-level fluoroquinolone resistance of S . dysenteriae exposed to these antibiotics may occur in the absence of gyrA mutations and involve a proton motive force(pmf)-dependent efflux system.

Indian J Med Res, 1997 Dec, 106, 494 - 6
Isolation of a fluoroquinolone resistant Shigella dysenteriae 1 strain from Calcutta; Chunder N et al.; Fourteen strains of Shigella spp . were isolated from patients aged 5-12 yr, hospitalized with dysentery during 1995-1996 . The strains isolated were Shigella dysenteriae 1, S . flexneri and S.sonnei . All but one of the 14 strains were sensitive to ciprofloxacin and norfloxacin . The MIC of both the fluoroquinolones was 15 micrograms/ml for the resistant S.dysenteriae 1 strain (NRM4) . Therefore, the careful use of antimicrobials is required for therapy of Shigellosis.

Folia Microbiol (Praha), 1997, 42(6), 565 - 8
Hydrophobicity and outer membrane proteins of Shigella dysenteriae type 1 after treatment with subinhibitory concentrations of aminoglycosides; Hostacka A et al.; Hydrophobicity and profiles of outer membrane proteins of Shigella dysenteriae type 1 after treatment with subinhibitory concentrations (1/2 or 1/4 of the MIC) of aminoglycosides were studied . The antimicrobial activity of the antibiotics tested was 3.12 mg/L (amikacin, tobramycin) and 6.25 mg/L (gentamicin) . The hydrophobicity of the cell surface of S . dysenteriae type 1 was decreased after exposure to all aminoglycosides at a concentration of 1/2 of the MICs; 1/4 of the MICs of the antibiotics did not affect bacterial aggregation in the presence of ammonium sulfate . SDS-polyacrylamide gel electrophoresis showed that the profiles of outer membrane proteins of the strain treated with aminoglycosides at both subinhibitory concentrations were not changed as compared to the control.

Lab Anim Sci, 1997 Dec, 47(6), 602 - 5
Lack of reactivation of shigellosis in naturally infected enrofloxacin-treated cynomolgus monkeys after exogenous immunosuppression; Black-Schultz L et al.; Four cynomolgus macaques housed at our facility became acutely ill with dysenteric symptoms . Enteric isolates established an etiologic diagnosis of Shigella flexneri . Enrofloxacin antimicrobial therapy cleared the infection with no perceptible bacterial shedding or clinical signs of disease . High-dose methyl-prednisolone therapy was administered to the four monkeys for 5 weeks . The animals were monitored for signs of shigellosis and bacterial shedding weekly throughout the study, for a total of 7 weeks . Although methylprednisolone therapy induced marked cellular immunosuppression in all four animals, as measured by in vitro assays, no animal had evidence of clinical shigellosis or bacterial shedding . These results suggest that cynomolgus macaques naturally infected with S . flexneri and appropriately treated with enrofloxacin are unlikely to have reactivation of shigellosis and shedding of bacteria in the feces during periods of stress or profound immunosuppression.

Arch Latinoam Nutr, 1997 Mar, 47(1), 47 - 9
{Prevalence of Plesiomonas shigelloides in surface water}; Hernandez P et al.; Plesiomonas shigelloides is a Gram negative rod that has been implicated in acute gastroenterities, meningitis, bacteremia and osteomyelitis . Is normally found in the environment, in fresh water, fish and birds, particularly in tropical and subtropical regions . The present study was pursued with the purpose of establish the role of surface water as reservoir and transmission vehicle and to evaluate the seasonal effect on incidence . Surface water samples were isolated on the surface of two selective agars and simultaneously were concentrated using the Seidler technique, submitted to enrichment procedure in alkaline peptone water and isolated on the surface of the selective agars . Isolates were characterized using biochemical test . The prevalence on analyzed samples was 59% and a higher frequency was observed during the warmer season . The use of this water to irrigate vegetable products that are to be consumed without ulterior cooking may represent a risk to the public health.

Ann Trop Med Parasitol, 1997 Sep, 91(6), 643 - 7
Antimicrobial susceptibility of Shigella from a rural community in Bangladesh; Mamun KZ et al.; Of the 63 Shigella strains isolated from stool cultures from 200 patients who attended a district hospital in Bangladesh with bloody diarrhoea, 37 (59%) were S . dysenteriae type 1, 25 (39%) were S . flexneri and only one (2%) was S . sonnei . Over half (54%) of the Shigella isolates came from children aged < 10 years . Most (89%) of the isolates of S . dysenteriae type 1 were resistant to ampicillin, cotrimoxazole, nalidixic acid, tetracycline and chloramphenicol . Although many (60%) of the isolates of S . flexneri were resistant to ampicillin and cotrimoxazole, only 4% of them were resistant to nalidixic acid . However, all of the S . dysenteriae and S . flexneri were sensitive to ciprofloxacin . The need for periodic monitoring to determine the resistance pattern in remote areas is emphasised.

Infect Immun, 1998 Jan, 66(1), 77 - 82
Immunogenicity of IpaC-hybrid proteins expressed in the Shigella flexneri 2a vaccine candidate SC602; Barzu S et al.; We have investigated the capacity of live attenuated Shigella flexneri strains to act as vectors for the induction of local and systemic antibody responses against heterologous epitopes . The S . flexneri IpaC antigen was selected as a carrier protein into which the C3 neutralizing epitope of the poliovirus VP1 protein was inserted in eight sites distributed along IpaC . The resulting IpaC-C3 hybrid proteins were expressed from recombinant plasmids in the S . flexneri 2a vaccine candidate, SC602 . Their production was similar to that of wild-type IpaC . All of the hybrid proteins but one were secreted as efficiently as wild-type IpaC . Immunization of mice with each of the recombinant SC602 derivatives reveals that one construct is able to induce serum and local anti-C3 antibodies, showing that at least one permissive site of insertion within IpaC can be defined . Furthermore, mouse-to-mouse variability in the anti-C3 response indicates that the amount of hybrid proteins produced in the host by SC602 should be improved for optimal use of S . flexneri live attenuated strains as mucosal vectors for foreign epitopes.

Phytochemistry, 1997 Dec, 46(7), 1215 - 8
A succinylanthranilic acid ester and other bioactive constituents of Jolyna laminarioides; Atta-Ur-Rahman et al.; Methyl 2-{propanamide-2'-methoxycarbonyl} benzoate, fucosterol, trans-phytol and p-formylphenol were isolated for the first time from a methanolic extract of Jolyna laminarioides . Methyl 2-{propanamide-2'-methoxycarbonyl}-benzoate exhibited chymotrypsin inhibitory activity and also found to be active against Escherichia coli and Shigella boydii . Fucosterol exhibited antifungal activity against Curvularia lunata, Stachybotrys atra and Microsporum canis.

J Hosp Infect, 1997 Nov, 37(3), 199 - 205
Nosocomial transmission of Shigella dysenteriae type 1; Pillay DG et al.; An outbreak of dysentery due to Shigella dysenteriae type 1 occurred in a chronic care psychiatric institution in Durban, South Africa . Of the 10 patients who developed dysentery, 4 (40%) died . S . dysenteriae type 1 was isolated from stool samples from two of the four patients tested and ribotyping showed that these isolates were identical but differed from other community acquired strains . The isolates were resistant to ampicillin, chloramphenicol, tetracycline and co-trimoxazole . Infection control measures including isolation, cohort nursing and strict hand disinfection resulted in rapid control of the outbreak.

J AOAC Int, 1997 Nov-Dec, 80(6), 1191 - 7
Survival and detection of Shigella flexneri in vegetables and commercially prepared salads; Rafii F et al.; The normal bacterial microflora of 4 commercially prepared salads (coleslaw, crab salad, carrot salad, and potato salad) and 3 vegetables (green pepper, onion, and cabbage) were evaluated . Twenty-eight species of bacteria, including potential pathogens, were isolated . The foods were artificially inoculated with an avirulent mutant strain of Shigella flexneri 5 (pHS1059) to develop a method for the rapid detection of Shigella spp . Bacteria were separated from insoluble and particulate salad ingredients by filtration through shark skin filter paper and by low speed centrifugation . S . flexneri survived at 4 degrees C in all salads for at least 11 days and up to 20 days in crab salad . The polymerase chain reaction (PCR), using primers for amplification of a 118-base pair DNA fragment from the virulence-associated spa region, present in all Shigella spp., was used to detect S . flexneri in filtrates from salads inoculated with S . flexneri 5 (pHS1059) . DNA was amplified from all of the artificially contaminated salads and vegetables except green pepper . After 3-5 days of storage, the PCR also amplified S . flexneri DNA from salads that had been enriched with nutrients to increase the number of bacteria . Green peppers contained a PCR inhibitory substance that was attenuated by dilution and enrichment before the PCR . No amplification of DNA was observed in foods to which S . flexneri had not been added.

Microbiol Immunol, 1997, 41(10), 809 - 13
Cloning and characterisation of the aroA and aroD genes of Shigella dysenteriae type 1; Walker JC et al.; The aroA and aroD genes from Shigella dysenteriae type 1, encoding 5-enolpyruvylshikimate 3-phosphate synthase and 3-dehydroquinase, respectively, were cloned by polymerase chain reaction (PCR) . Their nucleotide sequences were determined and predicted to code for 46 kDa and 27.5 kDa proteins, respectively . Protein expressed from these genes using the minicell system, corresponded to the size of the predicted protein products . The cloned genes were shown to be functional by complementation of Escherichia coli aroA- and aroD- mutants . The predicted amino acid sequences of the cloned aroA (427 amino acids) and aroD (252 amino acids) genes of S . dysenteriae type 1 were found to be highly homologous to the corresponding genes in other bacterial species, indicating the high conservation of these housekeeping genes . The use of the cloned aroA and aroD genes in the development of a vaccine strain against S . dysenteriae is discussed.

J Clin Microbiol, 1997 Dec, 35(12), 3163 - 5
Outbreak of Shigella sonnei in a clinical microbiology laboratory; Mermel LA et al.; Laboratory technologists (22%) developed infections with Shigella sonnei . The isolates had the same antibiogram and pulse-field gel electrophoresis pattern as an unknown isolate handled by a laboratory student . Covering faucet handles with paper towels during hand washing in the laboratory was protective . No further cases occurred after the laboratory was cleaned with a phenolic agent and a handle-free faucet was installed.

J Altern Complement Med, 1997 Spring, 3(1), 13 - 20
Microbiological screening of Indian medicinal plants with special reference to enteropathogens; Vijaya K et al.; The World Health Organisation (WHO) has recommended that all member states actively promote native medicines in their country . Ten Indian medicinal plants were screened for antibacterial activity specific to enteropathogens . Diffusion and dilution methods were used to measure the antibacterial activity . Allium sativum, Camellia sinensis, and Chamaesyce hirta showed higher activity when compared to the rest . They had a minimum bactericidal concentration (MBC) of < 100 micrograms/ml and gave inhibition zones of more than 2 cm . Among the pathogens studied, Vibrio cholerae and Shigella flexneri were found to be highly susceptible to the plant extracts.

Infect Immun, 1997 Dec, 65(12), 5358 - 63
Identification of shuA, the gene encoding the heme receptor of Shigella dysenteriae, and analysis of invasion and intracellular multiplication of a shuA mutant; Mills M et al.; shuA encodes a 70-kDa outer membrane heme receptor in Shigella dysenteriae . Analysis of the shuA DNA sequence indicates that this gene encodes a protein with homology to TonB-dependent receptors of gram-negative bacteria . Transport of heme by the ShuA protein requires TonB and its accessory proteins ExbB and ExbD . The shuA DNA sequence contains a putative Fur box overlapping the -10 region of a potential shuA promoter, and the expression of shuA is repressed by exogenous iron or hemin in a Fur-dependent manner, although hemin repressed expression to a lesser extent than iron salts . Disruption of this open reading frame on the S . dysenteriae chromosome by marker exchange yielded a strain that failed to use heme as an iron source, indicating that shuA is essential for heme transport in S . dysenteriae . However, shuA is not essential for invasion or multiplication within cultured Henle cells; the shuA mutant invaded and produced normal plaques in confluent cell monolayers.

Infect Immun, 1997 Dec, 65(12), 5338 - 41
A systemic downregulation of gamma interferon production is associated with acute shigellosis; Raqib R et al.; Production of cytokines by peripheral blood mononuclear cells from Shigella-infected patients was assessed . The frequencies of tumor necrosis factor alpha (TNF-alpha), TNF-beta, and transforming growth factor beta mRNA-expressing cells were persistently upregulated during the course of shigellosis in comparison to those of healthy controls . In contrast, the frequency of gamma interferon (IFN-gamma) mRNA-expressing cells was significantly reduced during the acute stage compared to that during the convalescent stage and to that of healthy Bangladeshi controls (P < 0.01) . Constitutive IFN-gamma production in Bangladeshi controls was significantly upregulated compared to that in Swedish controls.

Infect Immun, 1997 Dec, 65(12), 5165 - 70
The interleukin 1beta-converting enzyme, caspase 1, is activated during Shigella flexneri-induced apoptosis in human monocyte-derived macrophages; Hilbi H et al.; Shigella, the etiological agent of bacillary dysentery, rapidly kills human monocyte-derived macrophages in vitro . Wild-type Shigella flexneri, but not a nonvirulent derivative, induced human macrophage apoptosis as determined by morphology and terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) . Shigella-mediated macrophage cell death was blocked by the peptide inhibitors of caspases, acetyl-Tyr-Val-Ala-Asp-aldehyde (acetyl-YVAD-CHO) and acetyl-Tyr-Val-Ala-Asp-chloromethylketone (acetyl-YVAD-CMK) . Protection from apoptosis by YVAD was observed in monocytes matured in the presence or absence of colony-stimulating factors (CSF) like macrophage-CSF or granulocyte-macrophage-CSF . Furthermore, lipopolysaccharide (LPS) or gamma interferon (IFN-gamma) rendered human macrophages partially resistant to Shigella cytotoxicity . Macrophages stimulated with either LPS or IFN-gamma were also protected by YVAD from Shigella-induced cell death . During Shigella infections of human macrophages, interleukin-1beta (IL-1beta) was cleaved to the mature form . IL-1beta maturation was severely retarded by YVAD, indicating that IL-1beta-converting enzyme (ICE; caspase 1) is activated in Shigella-induced apoptosis . The finding that Shigella induces apoptosis in human macrophages by activating ICE supports the hypothesis that the acute inflammation characteristic of shigellosis is initially triggered by apoptotic macrophages which release mature IL-1beta during programmed cell death.

Nihon Rinsho Meneki Gakkai Kaishi, 1997 Oct, 20(5), 453 - 6
{A case of reactive arthritis fallen after shigellosis infection}; Tsujimura M et al.; A 25-year-old woman was admitted for general arthralgia in July, 1989 . Reactive arthritis with arthralgia after Shigellosis was diagnosed by sex, localization of arthralgia and positive for HLA-B 27 . Within 3 weeks after starting diclifenac sodium 75 mg/day, the arthralgia remitted . It has been reported that patients who are positive for HLA-B 27 have a more severe acute or chronic sacroiliitis, and our case may support this report.

Carbohydr Res, 1997 Sep 26, 303(3), 319 - 25
Structural studies on the Shigella-like Escherichia coli O121 O-specific polysaccharide; Parolis H et al.; The O-specific polysaccharide isolated from the lipopolysaccharide (LPS) of Escherichia coli O121 by mild acid hydrolysis has been studied using mainly NMR spectroscopy . The polysaccharide was treated with mild base to yield a O-deacetylated polysaccharide which contained D-GlcNAc, D-GalNAcA, D-GalNAcAN (2-acetamido-2-deoxy-D-galacturonamide) and D-Qui4NAcGly (where D-Qui4N is 4-amino-4,6-dideoxy-D-glucose) in equimolar proportions . The presence of the amide was confirmed by recording the 1H NMR spectrum of the O-deacetylated polysaccharide at different pH values . The O-acetyl group was located on O-3 of the GalNAcAN and the structure of the polysaccharide can be written as {sequence: see text} This structure is almost identical to that previously reported for the O-specific polysaccharide of Shigella dysenteriae type 7 LPS, the only difference being that O-acetylation is stoichiometric in the latter.

Eur J Immunol, 1997 Oct, 27(10), 2620 - 5
Induction of anti-carbohydrate antibodies by phage library-selected peptide mimics; Phalipon A et al.; One of the prerequisites for the development of polysaccharide subunit vaccines is the induction of an efficient immune response to carbohydrate antigens like lipopolysaccharide (LPS) or capsular polysaccharide antigens of pathogens . In an attempt to overcome the problems that arise from the T-independent immune response induced by such antigens, selecting peptide sequences that mimic protective carbohydrate epitopes has been proposed . In this study, we investigate a new selection strategy for immunogenic peptide mimics using the phage-displayed peptide library technology . Two monoclonal antibodies (mAb) of the A isotype (mIgA), mIgA C5 and mIgA I3, specific for the O-antigen (O-Ag) part of the human pathogen Shigella flexneri serotype 5a LPS and protective against homologous infection were used to screen two phage-displayed nonapeptide libraries in pVIII . Using mIgA C5, 13 different specific clones were selected, and 6 using mIgA I3; 5 of the latter also interacted in enzyme-linked immunosorbent assay with the first mAb . All of the 19 clones selected were separately used to immunize mice, but only 2 of them, p100c (mIgA I3-specific) and p115 (interacting with both mIgA) were able to induce anti-O-Ag antibodies . The immune response was specific for the O-Ag of the S . flexneri serotype 5a, and also selectively recognized the corresponding bacterial strain . The amino acid sequences of p100c and p115 immunogenic peptide mimics were YKPLGALTH (flanked by two Cys residues) and KVPPWARTA, respectively . These results are the first example of immunogenic mimicry of carbohydrates by phage-displayed peptides, and indicate a new strategy of selection of immunogens for the development of anti-polysaccharide vaccines.

J Med Microbiol, 1997 Nov, 46(11), 949 - 52
Restriction endonucleases in clinical isolates of Shigella spp; Lee KF et al.; Thirteen restriction endonuclease-containing strains were isolated from a collection of 186 clinical isolates of Shigella spp . Among these, eight and five isolates carried isoschizomers of EcoRII and NciI, respectively . The former restriction-modification (R-M) system was homologous to that of EcoRII and was located on plasmids with sizes of 46.6 or 55.6 kb . Isolates producing NciI isoschizomers contained a 5.7-kb non-transferable plasmid . Together with antimicrobial susceptibility tests and plasmid profile studies, it is concluded that these two R-M systems are not widely spread but confined to strains with similar antibiotic resistance and plasmid profile.

FEMS Microbiol Lett, 1997 Nov 1, 156(1), 133 - 9
Cloning and analysis of the glucosyl transferase gene encoding type I antigen in Shigella flexneri; Bastin DA et al.; The O-antigen of most Shigella flexneri serotypes contains an identical tetrasaccharide repeating unit . Apart from serotype Y, the O-antigen is modified by addition of a glucosyl and/or O-acetyl residue to a specific position in the O-unit . In this study the glucosyl transferase gene from a serotype 1 a has been cloned and identified . The bacteriophage SfV integrase (int) gene was used to probe a S . flexneri Y53 (serotype 1 a) cosmid library and 18 unique clones were identified . Southern hybridisation of these clones indicated two unlinked regions of the chromosome contained the int homologue . When expressed in a live candidate vaccine strain of S . flexneri serotype Y (SFL124), clones with one region produced type I antigen, whereas clones containing the other region produced mainly type Y antigen . One of the cosmid clones positive for type I antigen by agglutination and Western blotting was selected for further study . Genes involved in O-antigen glucosyl modification were mapped on a 5.8 kb fragment and subclones were produced which fully or partially expressed the type I antigen, depending on the extent of the clone . Fully and partially expressing clones may be useful vaccine candidate strains for protection against disease caused by two serotypes of S . flexneri.

J Diarrhoeal Dis Res, 1997 Jun, 15(2), 65 - 70
Detection of non-culturable Shigella dysenteriae 1 from artificially contaminated volunteers' fingers using fluorescent antibody and PCR techniques; Islam MS et al.; Epidemiological studies have demonstrated that hands may be an important vehicle for transmission of shigellosis . The present study was carried out to find out the survival potential of Shigella dysenteriae 1 on fingers of volunteers . Finger surface was inoculated with 10(5) cfu of S . dysenteriae 1 and then the bacteria were detected using conventional culture, PCR and fluorescent antibody (FA) techniques after different time intervals . It was found that S . dysenteriae 1 survived for up to one hour in culturable form but up to four hours in non-culturable form on human fingers . The non-culturable S . dysenteriae was detected by PCR and FA techniques . This study elaborates on the role that fingers have in the transmission of shigellae.

Pediatr Res, 1997 Nov, 42(5), 644 - 50
Antibodies to Escherichia coli and Shigella flexneri in milk from undernourished mothers: studies on sodium dodecyl sulfate-polyacrylamide gel electrophoresis-separated antigens; Herias MV et al.; Analysis of IgA, IgM, and IgG antibodies against Escherichia coli O6, its lipopolysaccharide (LPS), and Shigella flexneri were performed in the milk of moderately undernourished Guatemalan women receiving either a low or a high calorie supplement, using SDS-PAGE . As expected, the immunostaining analysis of milk antibodies showed that IgA was the predominant isotype in both groups . Concerning the other Igs, antibodies against O6 LPS were mainly of the IgM isotype, whereas IgG antibodies were more prominent than IgM against the bacterial whole cell preparations . Seven to nine distinct bands, ranging in molecular mass from 13.5 to 109 kD were selected for each antigen to compare the milk antibodies between the two groups of women . After a 20-wk supplementation period, the IgA and IgG antibodies to the E . coli, O6 LPS, and S . flexneri were not found negatively affected by a low calorie intake . A significantly lower immunostaining intensity was, however, obtained for the low calorie intake group regarding the IgM antibody activity against four high molecular mass bands of the E . coli whole cell preparation . A decreased immunostaining intensity was also found in the same group for IgM antibodies against two bands of E . coli O6 LPS when analyzing paired samples collected at d 0 and wk 20 . No differences were found for IgM antibodies against any of the S . flexneri antigens . In conclusion, the results suggest that low calorie intake does not significantly affect the production of milk IgA antibodies to E . coli and S . flexneri antigens in these women . Still, IgM antibodies against certain proteins and LPS molecules of E . coli may be decreased . IgG antibodies, although also present in milk, seemed to be directed mainly against bacterial proteins and not to LPS.

Infect Immun, 1997 Nov, 65(11), 4395 - 404
Role of lipopolysaccharide in signaling to subepithelial polymorphonuclear leukocytes; Beatty WL et al.; Polymorphonuclear leukocyte (PMN) infiltration and migration across colonic intestinal epithelia is a hallmark of inflammation in Shigella flexneri-mediated dysentery . To identify bacterial signals associated with this process, potential stimulatory factors mediating initial PMN association with the epithelium and subsequent transepithelial migration were examined in an in vitro model system . Quantitative analyses revealed that purified S . flexneri lipopolysaccharide (LPS) deposited at the apical surface of polarized intestinal epithelial cells transcytosed to the basolateral pole, a process dependent on the stage of epithelial cell differentiation . Transcytosed LPS in the presence of normal human serum (NHS), a source of LPS binding protein and soluble CD14, mediated both interleukin-8 secretion at the basolateral pole and enhanced PMN adherence . In addition, LPS stimulated a significant degree of directed transepithelial migration of PMNs, an event that was further enhanced in the presence of NHS . These results implicate LPS in signaling subepithelial PMN emigration and enhancing PMN-epithelium interactions prior to and during subsequent Shigella-induced transepithelial migration.

J Bacteriol, 1997 Nov, 179(21), 6537 - 50
Positive regulation of Shigella flexneri virulence genes by integration host factor; Porter ME et al.; In Shigella flexneri, expression of the plasmid-encoded virulence genes is regulated via a complex cascade involving DNA topology, specific transactivators, and the nucleoid-associated protein H-NS, which represses transcription under inappropriate environmental conditions . We have investigated the involvement of a second nucleoid-associated protein, integration host factor (IHF), in virulence gene expression . We found that transcription of the invasion-specific genes is repressed in a strain harboring an ihfA mutation, particularly on entry into the stationary phase . Expression of the virB gene, whose product is required for the activation of these structural genes, is also enhanced by IHF in the stationary phase . In contrast, the virF gene, which encodes an activator of virB, is stimulated by IHF in both the logarithmic and early stationary phases of growth, as is another virF-regulated gene, icsA . We have identified regions of the virF, virB, and icsA promoters which form IHF-dependent protein-DNA complexes in vitro and have located sequences within these regions with similarity to the consensus IHF binding site . Moreover, results from experiments in which the virF or virB gene was expressed constitutively confirm that IHF has a direct input at the level of both virF and virB transcription . Finally, we provide evidence that at the latter promoter, the primary role of IHF may be to overcome repression by the H-NS protein . To our knowledge, this is the first report of a role for IHF in controlling gene expression in S . flexneri.

C R Acad Sci III, 1997 Sep, 320(9), 729 - 34
{Molecular and cellular bases of intestinal epithelial cell invasion by Shigella flexneri}; Sansonetti PJ; A key step in the pathogenesis of shigellosis is the capacity of the causative bacteria, shigellae, to invade colonic and rectal epithelial cells in humans . This invasive process encompasses several steps: entry into epithelial cells by induction of a macropinocytic event caused by secreted Ipa proteins . the bacterium then escapes from the vacuole and reaches the cytoplasmic compartment in which it divides rapidly and becomes motile via the expression of a surface protein, IcsA, whose polar localization achieves directed polymerization of actin filaments that push the bacterial body forward . Bacteria then engage the inner face of the cellular membrane in the junctional area and form protrusions allowing their passage into the adjacent cell . Lysis of the double membrane eventually allows access to the cytoplasmic compartment of the adjacent cell, thus providing the bacterium with a very efficient mechanism of epithelial colonization.

Appl Environ Microbiol, 1997 Oct, 63(10), 4123 - 6
Factors controlling acid tolerance of Listeria monocytogenes: effects of nisin and other ionophores; Datta AR et al.; The acid tolerance of a Listeria monocytogenes serotype 4b strain was studied by measuring its ability to survive at an acidic pH at 37 degrees C . The acid tolerance of L . monocytogenes was much lower than those of Escherichia coli O157:H7 and Shigella flexneri strains . This observation suggested a higher infective dose for L . monocytogenes than E . coli O157:H7 and Shigella . The susceptibility of L . monocytogenes to acidic pH was dependent upon growth medium pH and growth phase of the culture . Nisin and some other ionophores reduced the acid tolerance of both stationary-phase and log-phase cultures of L . monocytogenes . These studies indicated that nisin might be a useful candidate for controlling acid tolerance of L . monocytogenes.

Diagn Microbiol Infect Dis, 1997 Aug, 28(4), 165 - 71
Antimicrobial resistance and serotypes of Shigella isolates in Kigali, Rwanda (1983 to 1993): increasing frequency of multiple resistance; Bogaerts J et al.; The serotype distribution and susceptibility to nine antibiotics was determined for 2491 Shigella isolates cultured in the medical laboratory of the Centre Hospitalier de Kigali, Rwanda, during 1983 to 1993 . Overall, Shigella flexneri was the most frequent species, ranking before Shigella sonnei, Shigella boydii, and Shigella dysenteriae . However, the relative frequency of the different Shigella spp . showed an important variability over time . S flexneri increased from 40% in 1983 to 68% of the isolates in 1993 whereas S . dysenteriae Type 1 decreased gradually from 30 to 0.5% of the isolates in 1992 . After the outbreak of severe civil unrest, which caused the displacement of many people to the capital, a new epidemic of dysentery started in the Kigali area and S . dysenteriae Type 1 accounted again for 24% of the isolates in 1993 . In 1983, resistance to tetracycline, streptomycin, and sulfonamides was common among the endemic Shigella spp . Resistance to chloramphenicol was observed in 17% (30/182) of the isolates . Only 10% were resistant to ampicillin and an equal proportion to trimethoprim, whereas 5% of the isolates showed resistance to both products . By 1993, 66% (195/295) of the isolates were resistant to chloramphenicol (for comparison with 1983, p < 0.001), 70% (207/295) to ampicillin (p < 0.001), 67% to trimethoprim (p < 0.001), and 58% had combined resistance to the latter two drugs (p < 0.001) . Resistance patterns differed strongly by species, S . flexneri being more frequently resistant than S . sonnei . In 1983, all S . dysenteriae Type 1 isolates were resistant to ampicillin, chloramphenicol, tetracycline, and sulfonamides . Trimethoprim resistance increased from 31% (25/80) in 1983 to 96% (26/27) of the isolates in 1986 (p < 0.001) . After the introduction of nalidixic acid as an alternative for trimethoprim-sulfamethoxazole, trimethoprim resistance decreased to 87%, during 1987 to 1992, and subsequently to 68% of the isolates in 1993 . However, 20% of the isolates became resistant to nalidixic acid in 1993 . Ampicillin and trimethoprim-sulfamethoxazole are no longer useful for the empirical treatment of shigellosis in Rwanda.

Pediatr Nephrol, 1997 Oct, 11(5), 560 - 4
Post-dysenteric hemolytic uremic syndrome in children during an epidemic of Shigella dysentery in Kwazulu/Natal; Bhimma R et al.; We report 81 of 107 cases of hemolytic uremic syndrome (HUS), admitted between July 1994 and February 1996, following an outbreak of Shigella dysenteriae type 1 dysentery in Kwazulu/Natal . All patients, excluding 1, were black with a mean age of 38 months (range 1-121); 50 (61.7%) were males . The mean duration of dysentery was 11.3 days (range 1-41) and HUS 15 days (range 1-91) . Most patients had acute oliguric renal failure (90.1%), 42 (51.6%) required peritoneal dialysis . Complications included encephalopathy 30 (37.0%), convulsions 12 (14.8%) and hemiplegia 2 (2.3%), gastrointestinal perforation 8 (9.9%), protein losing enteropathy 26 (32.1%), toxic megacolon 4 (4.9%), rectal prolapse 5 (6.2%), hepatitis 11 (13.6%), myocarditis 5 (6.2%), congestive cardiac failure 3 (3.7%), cardiomyopathy 3 (3.7%), infective endocarditis 1 (1.2%), septicemia 15 (18.5%), disseminated intravascular coagulation 17 (21%) . Leukemoid reactions were found in 74 (91.3%) patients, hyponatremia in 56 (69.1%), and hypoalbuminemia in 67 (82.7%) . Stool culture for Shigella dysenteriae type I was positive in only 7 (8.6%) patients; Shiga toxin assays were not performed . Outcome was as follows: recovery 32 (39.5%), impaired renal function 8 (9.9%), chronic renal failure 26 (32.1%), end-stage renal disease 1 (1.2%), and death 14 (17.3%) patients.

Schweiz Med Wochenschr, 1997 Jul 22, 127(29-30), 1229 - 33
{How is hemolytic-uremic syndrome in childhood acquired in Switzerland?}; Kernland KH et al.; Intestinal infections with shigatoxin-producing Escherichia coli or Shigella dysenteriae type I play a major role in the pathogenesis of the hemolytic-uremic syndrome in childhood . Escherichia coli has been repeatedly detected in the intestines of healthy cattle . Twenty-seven children with hemolytic-uremic syndrome were treated at our hospital between June 1990 and March 1997 . Factors indicating a possible previous contact with bovine intestinal content were found in 18 out of the 27 patients: parents stockbreeders (n = 7), recent visit to a cowshed or contact with cowdung or manure (n = 5), residence in a rural cattle-breeding area (n = 5), or consumption of raw milk (n = 1) . The factors mentioned were found in 5 out of 27 control patients (p < 0.01) . Two children experienced hemolytic-uremic syndrome after a stay respectively in Egypt and Tunisia . Our results indicate an important source for acquisition of hemolytic-uremic syndrome in childhood . Observing simple hygienic rules such as washing of hands and pasteurization of milk is likely to have a positive influence on the incidence of this illness . There are also grounds to consider adding the hemolytic-uremic syndrome to the list of travel-related diseases.

J Infect Dis, 1997 Oct, 176(4), 1013 - 8
Utility of a polymerase chain reaction diagnostic system in a study of the epidemiology of shigellosis among dysentery patients, family contacts, and well controls living in a shigellosis-endemic area; Gaudio PA et al.; Polymerase chain reaction (PCR) diagnostic methods have rarely been used in epidemiologic studies of Shigella and enteroinvasive Escherichia coli (EIEC) infections . In this study, amplification of the invasion plasmid antigen H (ipaH) gene by PCR and standard culture methods was used to identify Shigella species or EIEC among 154 patients with dysentery, 154 age-matched controls, and family contacts in Thailand . The ipaH PCR system increased the detection of Shigella species and EIEC from 58% to 79% among patients with dysentery and from 6% to 22% among 527 family contacts; 75% of infections in family members were asymptomatic . Detection of the ipaH gene was statistically associated with dysentery . Household contacts of patients with shigellosis diagnosed only by PCR had significantly higher rates of shigellosis than household contacts of patients who did not have Shigella or EIEC infections . Detection of the ipaH gene by PCR is far more sensitive than detection by standard culture and is highly correlated with evidence of Shigella transmission among family contacts.

Antimicrob Agents Chemother, 1997 Oct, 41(10), 2302 - 4
Involvement of a 43-kilodalton outer membrane protein in beta-lactam resistance of Shigella dysenteriae; Kar AK et al.; A beta-lactam-sensitive strain (C152) of Shigella dysenteriae showed two major outer membrane proteins (OMPs) with M(r)s of 43,000 and 38,000, while the clinical isolate M2 lacked the 43,000-Mr OMP, which acted as a channel for beta-lactam antibiotics . Permeability of beta-lactams across the outer membrane (OM) of M2 was lower than that across the OM of C152 . Mutants deficient in the 43-kDa OMP could be selected in vitro from strain C152 in the presence of cefoxitin . All beta-lactam-resistant strains were sensitive to imipenem.

Infect Immun, 1997 Oct, 65(10), 4075 - 81
The mechanism of cell death in Listeria monocytogenes-infected murine macrophages is distinct from apoptosis; Barsig J et al.; Various pathogenic bacteria with the capacity to live within eukaryotic cells activate an apoptotic program in infected host cells . Induction of apoptosis by Listeria monocytogenes in murine dendritic cells and hepatocytes has been described . Here we address the questions of whether and how the pathogen kills macrophages, its most important habitat . Employing several complementary techniques aimed at discriminating between apoptosis and necrosis, we show that murine bone marrow-derived macrophages (BMM) undergo delayed necrosis but not apoptosis when infected with listeriolysin (Hly)-producing L . monocytogenes . This pathogen failed to elicit apoptotic morphology, DNA fragmentation, and surface annexin V binding of macrophages, in contrast to Shigella flexneri infection or gliotoxin treatment, which were used as positive controls . Furthermore, macrophages infected with L . monocytogenes released lower quantities of interleukin-1beta (IL-1beta) than did Shigella flexneri-infected ones, indicating diminished or even absent activation of IL-1-converting enzyme in macrophages harboring L . monocytogenes . We conclude that murine BMM die by necrosis after several hours of cytoplasmic replication of L . monocytogenes . The pathogen may benefit from this feature by the possibility of taking advantage of cells of "pseudo-healthy" appearance, thus avoiding rapid elimination by other phagocytes.

Infect Immun, 1997 Oct, 65(10), 4005 - 10
Secretion of Ipa proteins by Shigella flexneri: inducer molecules and kinetics of activation; Bahrani FK et al.; The type III Mxi-Spa secretion machinery of Shigella flexneri is responsible for secretion of Ipa proteins, which are involved in the entry of bacteria into epithelial cells . Ipa proteins accumulate within bacteria growing in laboratory media, and their secretion is activated upon contact of bacteria with eukaryotic cells . In this study, we have identified a group of chemical compounds, including Congo red, Evans blue, and direct orange, which are able to induce secretion of Ipa proteins by bacteria suspended in phosphate-buffered saline . Parameters of kinetics of activation of Ipa secretion by Congo red were determined by measuring by enzyme-linked immunosorbent assay the amount of IpaC secreted and by investigating the increase in susceptibility of Ipa proteins to proteinase K degradation . Ipa secretion occurred at 37 degrees C, was obtained with 5 to 10 microM Congo red, and was complete within 30 min . In addition, activation of Ipa secretion by Congo red was observed with bacteria harvested throughout the exponential phase of growth but not with bacteria in the stationary phase . The interactions of Congo red and Congo red-related compounds with the Mxi-Spa secretion apparatus might be specific hydrophobic interactions similar to those involved in binding of Congo red to amyloid proteins.

Am J Public Health, 1997 Sep, 87(9), 1547 - 51
Shigellosis on Indian reserves in Manitoba, Canada: its relationship to crowded housing, lack of running water, and inadequate sewage disposal; Rosenberg T et al.; OBJECTIVES: This study compares incidence and hospitalization rates for shigellosis between Indians and the rest of the population in Manitoba, Canada . It examines the relationship between shigellosis and environmental conditions on reserves . METHODS: Rates were calculated with surveillance data and a survey of environmental infrastructure was done . RESULTS: Indians had shigellosis incidence and hospitalization rates that were 29 and 12 times as high, respectively, as those of the rest of the population . Household crowding, lack of piped water, and inadequate sewage disposal were significantly associated with an increased incidence of shigellosis on reserves . CONCLUSIONS: Many cases of shigellosis may be prevented by improving living conditions on Indian reserves.

Mol Microbiol, 1997 Aug, 25(4), 771 - 84
Characterization of an exported protease from Shiga toxin-producing Escherichia coli; Djafari S et al.; The gene for a novel, high molecular weight protein secreted by Shiga toxin-producing Escherichia coli (STEC) has been cloned, sequenced and characterized with respect to its activity . This gene, designated pssA, is localized on the large plasmid that also harbours the STEC haemolysin operon . Sequencing of a region comprising 10630nt revealed that the sequences flanking the pssA gene are composed of several remnants of different insertion elements . The PssA protein is produced as a 142kDa precursor molecule that, after N- and C-terminal processing, is released into the culture supernatant as a mature polypeptide of approximately 104kDa . The primary sequence of PssA is highly related to a family of autonomously transported putative virulence factors from different Gram-negative pathogens, which includes the Tsh protein of an avian-pathogenic E . coli strain, the SepA protein from Shigella flexneri and the EspC protein from enteropathogenic E . coli . A common motif present in all four proteins is reminiscent of the catalytic centre of certain serine proteases . PssA (protease secreted by STEC) indeed shows serine protease activity in a casein-based assay and is moreover cytotoxic for Vero cells . This activity of PssA and probably of other proteins of the Tsh family may be of functional importance during infection of the mucosal cell layer by the bacterial pathogen.

J Diarrhoeal Dis Res, 1997 Mar, 15(1), 21 - 4
Reactive arthritis associated with Shigella dysenteriae type 1 infection; Mazumder RN et al.; Shigella dysenteriae type 1 causes the most severe form of bacillary dysentery . The spectrum of illness ranges from mild watery diarrhoea to severe bloody diarrhoea . Shigellosis is often associated with intestinal complications, including intestinal perforation, intestinal obstruction, toxic dilatation of the colon, and prolapse of the rectum; systemic complications include septicaemia, hyponatraemia, hypoglycaemia, seizure, encephalopathy, haemolytic-uraemic syndrome, and malnutrition . Arthritis and conjunctivitis are rare extra-intestinal complications of shigellosis . Annually, about 110,000 patients receive treatment in the Dhaka Hospital of the International Centre for Diarrhoeal Disease Research, Bangladesh for diarrhoea and diarrhoea-associated illnesses, of which 11% are due to shigellosis . However, arthritis associated with shigellosis has not been reported from this population . Arthritis has been reported in association with infection due to S . flexneri and S . sonnei from other places . We are unaware of any reported case of arthritis in association with S . dysenteriae type 1 infections . In this report, we describe the clinical and laboratory features of a young woman who developed arthritis following S . dysenteriae type 1 infection.

Gene, 1997 Aug 22, 195(2), 217 - 27
Molecular characterization of the genes involved in O-antigen modification, attachment, integration and excision in Shigella flexneri bacteriophage SfV; Huan PT et al.; Bacteriophage SfV is a temperate phage of Shigella flexneri responsible for converting serotype Y (3,4) to serotype 5a (V; 3,4) through its glucosyl transferase gene . The glucosyl transferase (gtr) gene of SfV has been cloned and shown to partially convert S . flexneri serotype Y to serotype 5a . In this study, we found that the serotype-converting region of SfV was approximately 2.5 kb in length containing three continuous ORFs . The recombinant strain carrying the three complete ORFs expressed the type V and group antigen 3,4, both indistinguishable from that of S . flexneri 5a wild-type strain . The interruption of orf5 or orf6 gave partial conversion in the S . flexneri recombinant strain indicated by the incomplete replacement of group antigen 3,4 . The region adjacent to the serotype-conversion genes was found to be identical to the attP-int-xis region of phage P22 . Altogether, an approximately 2.2-kb sequence covering a portion of the serotype-conversion (approximately 500 nt)-attP-int-xis regions of SfV was remarkably similar to that of P22.

Gene, 1997 Aug 22, 195(2), 207 - 16
Shigella flexneri type-specific antigen V: cloning, sequencing and characterization of the glucosyl transferase gene of temperate bacteriophage SfV; Huan PT et al.; With lysogeny by bacteriophage SfV, Shigella flexneri serotype Y is converted to serotype 5a . The glucosyl transferase gene (gtr) from bacteriophage SfV of S . flexneri, involved in serotype-specific conversion, was cloned and characterized . The DNA sequence of a 3.7 kb EcoRI-BamHI fragment of bacteriophage SfV which includes the gtr gene was determined . This gene, encoding a polypeptide of 417 aa with 47.67 kDa molecular mass, caused partial serotype conversion of S . flexneri from serotype Y to type V antigen as demonstrated by Western blotting and the sensitivity of the hybrid strain to phage Sf6 . The deduced protein of the partially sequenced open reading frame upstream of the gtr showed similarity to various glycosyl transferases of other bacteria . Orf3, separated from the gtr by a non-coding region and transcribed convergently, codes for a 167 aa (18.8 kDa) protein found to have homology with tail fibre genes of phage lambda and P2.

Mol Microbiol, 1997 Aug, 25(3), 451 - 62
Disruption of IcsP, the major Shigella protease that cleaves IcsA, accelerates actin-based motility; Shere KD et al.; Shigella pathogenesis involves bacterial invasion of colonic epithelial cells and movement of bacteria through the cytoplasm and into adjacent cells by means of actin-based motility . The Shigella protein IcsA (VirG) is unipolar on the bacterial surface and is both necessary and sufficient for actin-based motility . IcsA is inserted into the outer membrane as a 120-kDa polypeptide that is subsequently slowly cleaved, thereby releasing the 95-kDa amino-terminal portion into the culture supernatant . IcsP, the major Shigella protease that cleaves IcsA, was identified and cloned . It has significant sequence similarity to the E . coli serine proteases, OmpP and OmpT . Disruption of icsP in serotype 2a S . flexneri leads to a marked reduction in IcsA cleavage, increased amounts of IcsA associated with the bacterium and altered distribution of IcsA on the bacterial surface . The icsP mutant displays significantly increased rates of actin-based motility, with a mean speed 27% faster than the wild-type strain; moreover, a significantly greater percentage of the icsP mutant moves in the cytoplasm . Yet, plaque formation on epithelial monolayers by the mutant was not altered detectably . These data suggest that IcsA, and not a host protein, is limiting in the rate of actin-based motility of wild-type serotype 2a S . flexneri.

Microbios, 1997, 90(362), 17 - 22
Active site peptide of beta-lactamase from Shigella flexneri UCSF-129; Campos M et al.; The peptide containing the catalytic serine of beta-lactamase from Shigella flexneri was determined as V-D-E-R-F-P-M-M-S*-T-F-K . It is a local pathogenic strain which produces intestinal problems, especially in children . The highly purified enzyme was prepared by affinity chromatography in phenylboronic acid-agarose gels . The peptide was obtained by tryptic hydrolysis, with further purification by Bio-Gel P-4, Sephadex QAE-25 and Sephadex SP-25 . The relevance of the serine, lysine and arginine residues was mainly shown by the loss of enzymatic activity after specific chemical modifications . Finally, this enzyme was classified as A, according to the similarity of this peptide with that of class A beta-lactamases such as R-TEM 1 and 2.

J Cell Biol, 1997 Sep 22, 138(6), 1255 - 64
Vinculin proteolysis unmasks an ActA homolog for actin-based Shigella motility; Laine RO et al.; To generate the forces needed for motility, the plasma membranes of nonmuscle cells adopt an activated state that dynamically reorganizes the actin cytoskeleton . By usurping components from focal contacts and the actin cytoskeleton, the intracellular pathogens Shigella flexneri and Listeria monocytogenes use molecular mimicry to create their own actin-based motors . We raised an antibody (designated FS-1) against the FEFPPPPTDE sequence of Listeria ActA, and this antibody: (a) localized at the trailing end of motile intracellular Shigella, (b) inhibited intracellular locomotion upon microinjection of Shigella-infected cells, and (c) cross-reacted with the proteolytically derived 90-kD human vinculin head fragment that contains the Vinc-1 oligoproline sequence, PDFPPPPPDL . Antibody FS-1 reacted only weakly with full-length vinculin, suggesting that the Vinc-1 sequence in full-length vinculin may be masked by its tail region and that this sequence is unmasked by proteolysis . Immunofluoresence staining with a monoclonal antibody against the head region of vinculin (Vin 11-5) localized to the back of motile bacteria (an identical staining pattern observed with the anti-ActA FS-1 antibody), indicating that motile bacteria attract a form of vinculin containing an unmasked Vinc-1 oligoproline sequence . Microinjection of submicromolar concentrations of a synthetic Vinc-1 peptide arrested Shigella intracellular motility, underscoring the functional importance of this sequence . Western blots revealed that Shigella infection induces vinculin proteolysis in PtK2 cells and generates p90 head fragment over the same 1-3 h time frame when intracellular bacteria move within the host cell cytoplasm . We also discovered that microinjected p90, but not full-length vinculin, accelerates rates of pathogen motility by a factor of 3 +/- 0.4 in Shigella-infected PtK2 cells . These experiments suggest that vinculin p90 is a rate-limiting component in actin-based Shigella motility, and that supplementing cells with p90 stimulates rocket tail growth . Earlier findings demonstrated that vinculin p90 binds to IcsA (Suzuki, T.A., S . Saga, and C . Sasakawa . 1996 . J . Biol . Chem . 271:21878-21885) and to vasodilator-stimulated phosphoprotein (VASP) (Brindle, N.P.J., M . R . Hold, J.E . Davies, C.J . Price, and D.R . Critchley . 1996 . Biochem . J . 318:753-757) . We now offer a working model in which proteolysis unmasks vinculin's ActA-like oligoproline sequence . Unmasking of this site serves as a molecular switch that initiates assembly of an actin-based motility complex containing VASP and profilin.

J Bacteriol, 1997 Sep, 179(18), 5777 - 82
The modified nucleoside 2-methylthio-N6-isopentenyladenosine in tRNA of Shigella flexneri is required for expression of virulence genes; Durand JM et al.; The virulence of the human pathogen Shigella flexneri is dependent on both chromosome- and large-virulence-plasmid-encoded genes . A kanamycin resistance cassette mutation in the miaA gene (miaA::Km Sma), which encodes the tRNA N6-isopentyladenosine (i6A37) synthetase and is involved in the first step of the synthesis of the modified nucleoside 2-methylthio-N6-isopentenyladenosine (ms2i6A), was transferred to the chromosome of S . flexneri 2a by phage P1 transduction . In the wild-type bacterium, ms2i6A37 is present in position 37 (next to and 3' of the anticodon) in a subset of tRNA species-reading codons starting with U (except tRNA(Ser) species SerI and SerV) . The miaA::Km Sma mutant of S . flexneri accordingly lacked ms2i6A37 in its tRNA . In addition, the mutant strains showed reduced expression of the virulence-related genes ipaB, ipaC, ipaD, virG, and virF, accounting for sixfold-reduced contact hemolytic activity and a delayed response in the focus plaque assay . A cloned sequence resulting from PCR amplification of the wild-type Shigella chromosome and exhibiting 99% homology with the nucleotide sequence of the Escherichia coli miaA gene complemented the virulence-associated phenotypes as well as the level of the modified nucleoside ms2i6A in the tRNA of the miaA mutants . In the miaA mutant, the level of the virulence-associated protein VirF was reduced 10-fold compared with the wild type . However, the levels of virF mRNA were identical in the mutant and in the wild type . These findings suggest that a posttranscriptional mechanism influenced by the presence of the modified nucleoside ms2i6A in the tRNA is involved in the expression of the virF gene . The role of the miaA gene in the virulence of other Shigella species and in enteroinvasive E . coli was further generalized.

Infect Immun, 1997 Sep, 65(9), 3686 - 92
Virulence plasmid instability in Shigella flexneri 2a is induced by virulence gene expression; Schuch R et al.; Expression of the predominantly plasmid-encoded virulence regulon of Shigella flexneri 2a is induced by growth at 37 degrees C and repressed by growth at 30 degrees C . During growth at 37 degrees C, spontaneous S . flexneri mutants arise which have undergone virulence plasmid curing or rearrangement and no longer display the virulent phenotype . In the laboratory, the unstable nature of the virulence plasmid causes complete loss of virulence in a growing population . We have undertaken an analysis of virulence plasmid instability, classifying events which produced individual avirulent derivatives within a virulent population and identifying the factor(s) which controlled conversion . Multiplex PCR analysis of DNA obtained from spontaneous avirulent derivatives indicated that virF and virB were deleted or otherwise inactivated in over 97% of the isolates . The virF and virB loci encode regulatory proteins required for transcriptional activation of the virulence regulon . Inactivation of these key regulatory loci in the vast majority of avirulent derivatives which arose during growth at 37 degrees C suggested that virulence gene expression induced virulence plasmid instability . Consistent with this hypothesis, we observed stable virulence plasmid maintenance during growth of a wild-type strain at 30 degrees C where virulence gene expression was repressed . The virulence plasmid was also stably maintained in virF and virB mutants grown at 37 degrees C . Conversely, virulence plasmid destabilization was induced at 30 degrees C and accelerated at 37 degrees C through expression of VirF or VirB from multicopy plasmids . These results indicate that exposure of S . flexneri to conditions favoring induction of the virulent phenotype also favor its loss . The significance of this paradox of Shigella pathogenicity is discussed.

JAMA, 1997 Aug 6, 278(5), 396 - 8
An outbreak of Shigella dysenteriae type 2 among laboratory workers due to intentional food contamination; Kolavic SA et al.; CONTEXT: Shigella dysenteriae type 2 is rare in the United States, and outbreaks associated with this pathogen are uncommon . OBJECTIVE: To determine the magnitude and source of an outbreak of S dysenteriae type 2 . DESIGN: Retrospective cohort . SETTING: Laboratory of a large medical center . PATIENTS: Case patients were identified as laboratory workers who had diarrhea on or after October 28 and a positive stool culture or temperature greater than 37.8 degrees C . Laboratory workers with diarrhea only were probable case patients . MAIN OUTCOME MEASURES: We interviewed laboratory staff and performed identification, serotyping, and pulsed-field gel electrophoresis on isolates from case patients, implicated food, and laboratory stock culture . RESULTS: From October 29 through November 1, a total of 12 (27%) of 45 laboratory staff developed severe, acute diarrheal illness; 8 had S dysenteriae isolated from stool and 4 were hospitalized . All case patients reported having eaten muffins or doughnuts placed in the staff break room on October 29 . Pulsed-field gel electrophoresis showed stool isolates from 9 case patients were indistinguishable from S dysenteriae type 2 recovered from an uneaten muffin and from the laboratory's stock strain, a portion of which was missing . CONCLUSIONS: The source of the outbreak was most likely the laboratory's stock culture, which was used to contaminate the pastries . Results of this investigation underscore the need for adequate precautions to prevent inadvertent or intentional contamination from highly pathogenic laboratory specimens.

Pediatr Nephrol, 1997 Aug, 11(4), 508 - 12
Renal problems in black South African children; Thomson PD; Black South African children have an increased prevalence of acute post-streptococcal glomerulonephritis, focal glomerulosclerosis, hepatitis B-associated membranous nephropathy, congenital syphilis, congenital nephrotic syndrome with Alport-like basement membrane changes and Takayasu's arteritis, but a paucity of reflux nephropathy, polycystic kidney disease and non-shigella-induced haemolytic uraemic syndrome . However, in recent years, the haemolytic uraemic syndrome has become more prevalent in black children; this is usually due to Shigella dysenteriae type 1, and could indicate a different emphasis in the pathogenic mechanism . Focal glomerulosclerosis is the commonest reason for renal failure requiring transplantation in black children with rapidly progressive glomerulonephritis (usually streptococcal induced) being second . Transplantation has been somewhat problematic with a scarcity of kidneys at times, many mismatches and poor compliance in the lower socio-economic groups . The association of tuberculosis with focal glomerulosclerosis and Takayasu's arteritis in black South African children is intriguing . The progression of focal glomerulosclerosis is accelerated in those patients with evidence of previous tuberculosis, and in Takayasu's arteritis the association is almost absolute as experienced locally, with the data suggesting an autoimmune reaction.

South Med J, 1997 Aug, 90(8), 833 - 5
Brodifacoum rodenticide ingestion in a patient with shigellosis; Stanziale SF et al.; Factitious disorders are characterized by the intentional feigning or induction of signs and/or symptoms in order to assume the sick role . The spectrum of diseases and symptoms simulated is extensive . Although some patients may seek only the gratifications of the sick role, typically patients seek health care for their afflictions . We report the case of a woman with a history of numerous unexplainable illnesses and laboratory findings who had shigellosis . On routine evaluation, a severe prothrombin coagulopathy was discovered and later determined to be caused by brodifacoum, a "superwarfarin" drug found in potent rodenticides . The patient was successfully treated with daily vitamin K . She continued to deny intentional or accidental ingestion but did consent to psychiatric treatment.

Infect Immun, 1997 Aug, 65(8), 3337 - 44
Sensitization of human umbilical vein endothelial cells to Shiga toxin: involvement of protein kinase C and NF-kappaB; Louise CB et al.; Infection of humans with Shiga toxin-producing Escherichia coli O157:H7 and Shigella dysenteriae 1 is strongly associated with vascular endothelial cell damage and the development of hemolytic-uremic syndrome . The cytotoxic effect of Shiga toxins on vascular endothelial cells in vitro is enhanced by prior exposure to bacterial lipopolysaccharide (LPS) or either of the host cytokines tumor necrosis factor alpha (TNF) and interleukin-1beta (IL-1) . The purpose of this study was to examine individual signal transduction components involved in the sensitization of human umbilical vein endothelial cells (HUVEC) to Shiga toxin 1 . The results demonstrate that class I and II protein kinase C (PKC) isozymes are required for sensitization of HUVEC to Shiga toxin by phorbol myristate acetate (PMA) or LPS but not by TNF or IL-1 . Thus, the specific competitive inhibitor of class I/II PKC, 1-O-hexadecyl-2-O-methyl-rac-glycerol (AMG), prevented only the action of PMA and LPS on HUVEC . Additional data obtained with ATP binding site inhibitors which affect all PKCs (i.e., classes I, II, and III) suggest that TNF may utilize class III PKC isozymes in the Shiga toxin sensitization of HUVEC . Transcriptional activator NF-kappaB did not appear to be involved in the sensitization of HUVEC to Shiga toxin by LPS, TNF, IL-1, or PMA . Thus, the specific serine protease inhibitor L-1-tosylamido-2-phenylethyl chloromethyl ketone (TPCK) did not inhibit the sensitization of HUVEC to Shiga toxin by LPS, TNF, IL-1, or PMA despite its ability to inhibit NF-kappaB activation and the induction of the NF-kappaB-dependent tissue factor gene by these agents . Finally, all-trans retinoic acid partially inhibited the sensitization of HUVEC to Shiga toxin, by unknown mechanisms which also appeared to be independent of NF-kappaB activation . These results indicate that PKC plays a role in the sensitization of HUVEC to Shiga toxin in response to some, but not all, sensitizing agents . In contrast, NF-kappaB activation appears not to be involved in the sensitization of HUVEC to Shiga toxin by LPS, TNF, IL-1, or PMA.

Biochim Biophys Acta, 1997 Jul 10, 1361(1), 75 - 91
Calcium and protein kinase C play a significant role in response to Shigella toxin in rabbit ileum both in vivo and in vitro; Kaur T et al.; The role of second messengers in Shigella toxin (STx) induced fluid secretion in rabbit ileum was evaluated . In vivo and in vitro studies were carried out in presence or absence of following modulators: Ca2+ ionophore A23187 (15 microM), l-verapamil (200 microM), phorbol-12-myristate-13-acetate (PMA, 200 ng), 1-(5-isoquinolinyl-sulphonyl)-2-methyl-piperazine (H-7, 15 microg) and indomethacin (20 microM) . In in vivo studies, the fluid accumulation into rabbit ileal loops in response to STx was measured in presence or absence of these modulators . In in vitro studies, unidirectional fluxes of Na+ and Cl- were carried out in presence or absence of these modulators . The addition of Ca2+ ionophore A23187 along with STx further increases the amount of fluid already induced by STx . Whereas the presence of l-verapamil along with STx did not decrease the amount of fluid induced by STx . In vitro findings were in consonance with the in vivo studies . A significant increase in inositol triphosphate (IP3) levels was observed in enterocytes isolated from STx treated rabbit ileum . The addition of PMA into rabbit ileal loops in presence of STx mimicked the effect of STx while the presence of H-7 reversed the secretion caused by STx to absorption . Similar results were obtained while determining unidirectional fluxes of Na+ and Cl- in presence of PMA and also with H-7 . A significant increase in PKC levels was observed in the membrane fraction of enterocytes isolated from STx treated rabbit ileum as compared to control . Further a marked decrease in PKC levels was observed in the presence of H-7 in membrane fraction of enterocytes isolated from STx treated rabbit ileum . The addition of indomethacin into rabbit ileal loops reversed the secretion (caused by STx) to absorption . In vitro findings were in consonance with in vivo studies . Besides, there was a significant increase in PG-E levels in enterocytes isolated from STx treated rabbit ileum as compared to control . These findings suggested that STx induced enteritis involves the role of PKC, intracellular calcium stores and prostaglandins . The extracellular calcium pool probably does not play a significant role in this process.

New Microbiol, 1997 Jul, 20(3), 227 - 31
The molecular epidemiology of trimethoprim-sulphamethoxazole- resistance of Shigella flexneri in the Trakya region of Turkey; Otkun M et al.; Trimethoprim-sulphamethoxazole (SXT) resistance increased among Shigella flexneri isolates in 1995 relative to previous years, in the Trakya region, the European part of Turkey . Since this region is the entrance to Turkey from northern countries, a heavy traffic of travellers passing through should have been importing or exporting the resistant isolates . We studied the genetic basis and epidemiology of this resistance and monitored the clonal changes which have taken place in the meanwhile . During the study period, a total of 70 Shigella spp . were isolated . Of these 58 were S . flexneri, 10 were S . sonnei and two were S . boydii . S . dysenteriae was not isolated . Of S . flexneri isolates 32 were SXT, ampicillin, chloramphenicol and tetracycline resistant (pattern I), while two isolates were found to be resistant only to SXT (Pattern II) . Transconjugation experiments revealed that an approximately 80 Kbp self-transmissible plasmid carried the SXT resistance genes in both groups . However, EcoRI and HindIII restriction patterns of the plasmids from resistance pattern I and resistance pattern II were different . Ribotypes of three randomly selected isolates from pattern I were identical and were distinguishable from the ribotype of the isolate from pattern II . We concluded that at least two different clones with different plasmids and resistance patterns were spreading in our territory.

J Bacteriol, 1997 Jul, 179(14), 4493 - 500
Cloning and characterization of the region III flagellar operons of the four Shigella subgroups: genetic defects that cause loss of flagella of Shigella boydii and Shigella sonnei; Al Mamun AA et al.; To detect genetic defects that might have caused loss of flagella in Shigella boydii and Shigella sonnei, the region III flagellar (fli) operons were cloned from certain strains and analyzed with reference to the restriction maps and genetic maps of Escherichia coli fli operons . S . boydii NCTC9733 (strain C5 in this paper) had the 988-bp internal deletion in the fliF gene that encodes a large substructural protein of the basal body . Two strains (C1 and C8) had deletions of the entire fliF operon, and the remaining three (C3, C4, and C9) differed in the size of the restriction fragments carrying the fliF and fliL operons . Loss of flagella in S . boydii appears to originate in some defect in the fliF operon . S . sonnei IID969 lacked the fliD gene and, in place of it, carried two IS600 elements as inverted repeats . Genes downstream from fliD were not detected in the cloned fragment despite its large size but did appear elsewhere in the chromosome . The fliD gene encodes a cap protein of the flagellar filament, and its deletion results in overexpression of class 3 operons by the increased amount of FliA (sigmaF) caused by the excess export of the anti-sigma factor FlgM . Three other strains also had the fliD deletion, and two of them had another deletion in the fliF-fliG-fliH region . The fliD deletion might be the primary cause of loss of flagella in S . sonnei . The lack of FliF or FliD in each subgroup is discussed in connection with the maintenance of virulence and bacterial growth . We also discuss the process of loss of flagella in relation to transposition of IS elements and alterations of the noncoding region, which were found to be common to at least three subgroups.

J Bacteriol, 1997 Jul, 179(13), 4411 - 4
Identification of a fourth gene involved in dTDP-rhamnose synthesis in Streptococcus mutans; Tsukioka Y et al.; We had isolated three genes (rmlA, rmlB, and rmlC) involved in dTDP-rhamnose synthesis in Streptococcus mutans and found that three genes were insufficient for dTDP-rhamnose synthesis (Y . Tsukioka, Y . Yamashita, T . Oho, Y . Nakano, and T . Koga, J . Bacteriol . 179:1126-1134, 1997) . The rmlD gene of S . mutans, encoding the enzyme which catalyzes the last step of dTDP-rhamnose synthesis, has been cloned and sequenced . The cell extract of Escherichia coli expressing the rmlD gene of S . mutans exhibited enzymatic activity corresponding to its counterpart in Shigella flexneri, a gram-negative bacterium . Rhamnose was not detected in the cell wall preparation purified from the mutant in which the cloned gene was insertionally inactivated . Rabbit antiserum against S . mutans serotype c-specific antigen did not react with autoclaved extracts from the mutant . The rmlD gene product of S . mutans compensated for the incompleteness of dTDP-rhamnose synthesis by the three previously isolated genes . These results indicate that the rmlD gene product is indispensable for the dTDP-rhamnose pathway and subsequently for the synthesis of serotype-specific antigen in S . mutans . Furthermore, conservation of the rmlD gene in Streptococcus species was demonstrated by Southern blot analysis.

Lancet . 1997 Jun 7;349(9066):1670.
Enterohaemorrhagic Escherichia coli in Central African Republic; Germani Y et al.; PIP: A dysentery outbreak in the Central African Republic village of Zemio was diagnosed as "Shigella flexneri" by the Pasteur Institute in Bangui (IPB) in February 1996; 2 months later there was an outbreak of hemorrhagic colitis . 108 patients presented with bloody diarrhea; cramping abdominal pain, fever, nausea, and vomiting were uncommon . The illness lasted between 5 days and 3 weeks (average, 8 days) . Antibiotics were ineffective . Four patients died and several developed hemolytic-uremic syndrome . Stool cultures done at IPB tested negative . PCR was used to detect enterohemorrhagic Shiga-like toxin (SLT) 1 and 2, the invasivity gene ipaH, and the attaching and effacing gene eaeA . DNA fragments of 130 and 494 nucleotides corresponding to amplified SLT1 and eaeA were found in 80% of the specimens tested . No amplification was obtained for SLT2 or for ipaH in specimens collected during the second epidemic . These results suggest the presence of enterohemorrhagic Escherichia coli and the absence of Shigella . The number of reported cases of acute bloody diarrhea in infants and adults in Bangui has increased since 1996 . E . coli O157:H7 was isolated from two fatal adult cases . Smoked zebu meat was suspected in several hospital cases (bloody diarrhea, hemolytic anemia, and renal insufficiency) in which non-fermenting sorbitol E . coli O157:H7 was not isolated . In two cases of acute diarrhea, other serotypes of E . coli were indicated by retrospective PCR on stools which were positive for SLT1 and for eaeA and negative for invasivity . A study was conducted in Bangui on 290 cases (33 with bloody diarrhea) and 140 controls . Patients were not paired because of civil unrest in the city . The questionnaire included demographic and socioeconomic characteristics, environmental factors, and habitual food consumption . The major contributing factor was consumption of locally made meat pies (kanda), which were made with smoked zebu meat . Kanda is stored at ambient temperature, often for days, before it is sold in markets or along roads . Before 1996, E . coli was not reported as a cause of bloody diarrhea in the Central African Republic .

Vaccine, 1997 Jun, 15(8), 804 - 7
Attenuated bacteria as a DNA delivery vehicle for DNA-mediated immunization; Sizemore DR et al.; Previously, Shigella carrier 15D was shown to deliver a mammalian DNA expression plasmid to cultured cells with subsequent production of the plasmid-encoded foreign protein . In this study, we report in vivo delivery of a DNA expression plasmid to mucosal tissue results in the stimulation of immune responses against the plasmid-encoded foreign antigen . Splenocytes from mice receiving two intranasal inoculations of 15D carrying pCMV beta showed proliferative responses to the plasmid-encoded Escherichia coli beta-galactosidase . In addition, antibody specific for beta-galactosidase was detected in pooled sera collected from 15D (pCMV beta) infected mice.

Microb Pathog, 1997 Jun, 22(6), 363 - 76
Construction and characterization of genetically-marked bivalent anti-Shigella dysenteriae 1 and anti-Shigella flexneri Y live vaccine candidates; Klee SR et al.; Bivalent vaccine candidates were developed against Shigella dysenteriae 1 and Shigella flexneri, which are among the most frequent causative agents of shigellosis in developing countries . The rfp and rfb gene clusters, which code for S . dysenteriae serotype 1 O-antigen biosynthesis, were inserted into an arsenite resistance minitransposon and randomly integrated into the attenuated S . flexneri aroD serotype Y strain SFL124 . Nine recombinant clones that efficiently expressed both homologous and heterologous O-antigens were obtained . Southern blot analysis showed that in one clone the S . dysenteriae 1 genes had integrated into the chromosome, whereas in all the others they had integrated into the virulence plasmid . All recombinant clones exhibited normal growth characteristics, were able to invade and survive within eukaryotic cells to the same extent as the parental strain, and expressed efficiently the recombinant lipopolysaccharide within invaded cells . Immunization of mice with two of the recombinant clones resulted in the production of antibodies specific for both homologous and heterologous O-antigens . The recombinant clones constitute promising vaccine candidates which can readily be distinguished from endemic shigellae by their non-antibiotic resistance marker.

Infect Immun, 1997 Jun, 65(6), 2462 - 7
Characterization of Shigella type 1 fimbriae: expression, FimA sequence, and phase variation; Snellings NJ et al.; This study documents the presence of type 1 fimbriae on Shigella and confirms these mannose-sensitive adherence structures to be bona fide components of the Shigella surface . While laboratory-passaged Shigella strains and lyophilized clinical isolates failed to express type 1 fimbriae, 6 of 20 recent clinical isolates, including 4 Shigella flexneri strains, 1 Shigella boydii strain, and 1 Shigella dysenteriae strain, produced type 1 fimbriae as detected by mannose-sensitive hemagglutination (MSHA) and electron microscopy . Optimal production of a predominantly Fim+ population required serial passage every 48 to 72 h in unshaken brain heart infusion broth at 37 degrees C . Fim+ Shigella cultures were capable of reversibly switching to a non-MSHA, afimbriated phase during serial aerobic cultivation on tryptic soy agar plates . The amino acid sequence of S . flexneri type 1 FimA contained 18 substitutions compared to that of Escherichia coli fimbrillin . Indirect immunoelectron microscopy suggested the presence of both shared and unique epitopes on E . coli and S . flexneri type 1 fimbriae . Random phase variation between fimbriated and afimbriated states in Shigella was accompanied by the genomic rearrangement associated with phase variation in E . coli.

Infect Immun, 1997 Jun, 65(6), 2112 - 8
Construction and characterization of a live attenuated vaccine candidate against Shigella dysenteriae type 1; Klee SR et al.; Vaccine candidates against Shigella dysenteriae type 1, which is associated with the most severe cases of bacillary dysentery, were constructed . The rfp and rfb gene clusters, which code for S . dysenteriae 1 O antigen biosynthesis, were randomly integrated into either the chromosome or the virulence plasmid of the rough attenuated Shigella flexneri aroD strain SFL124-27 with a minitransposon carrying an arsenite resistance selection marker . The recombinant clones efficiently expressed the recombinant O antigen, exhibited a normal growth pattern, were able to invade and survive within eukaryotic cells to the same extent as the parental strain, and expressed the recombinant antigen within invaded cells . A clone was selected as the vaccine candidate, which was demonstrated to be immunogenic and safe in animal models, leading to 47% full protection and 53% partial protection against challenge with the wild-type strain.

Nucleic Acids Res, 1997 Jun 1, 25(11), 2114 - 20
Specific binding of sso II DNA methyltransferase to its promoter region provides the regulation of sso II restriction-modification gene expression; Karyagina A et al.; The regulation of the Sso II restriction-modification system from Shigella sonnei was studied in vivo and in vitro . In lacZ fusion experiments, Sso II methyltransferase (M . Sso II) was found to repress its own synthesis but stimulate expression of the cognate restriction endonuclease (ENase) . The N-terminal 72 amino acids of M . Sso II, predicted to form a helix-turn-helix (HTH) motif, was found to be responsible for the specific DNA-binding and regulatory function of M . Sso II . Similar HTH motifs are predicted in the N-terminus of a number of 5-methylcytosine methyltransferases, particularly M . Eco RII, M.dcm and M . Msp I, of which the ability to regulate autogenously has been proposed . In vitro, the binding of M . Sso II to its target DNA was investigated using a mobility shift assay . M . Sso II forms a specific and stable complex with a 140 bp DNA fragment containing the promoter region of Sso II R-M system . The dissociation constant (Kd) was determined to be 1.5x10(-8) M . DNaseI footprinting experiments demonstrated that M . Sso II protects a 48-52 bp region immediately upstream of the M . Sso II coding sequence which includes the predicted -10 promoter sequence of M . Sso II and the -10 and -35 sequences of R . Sso II.

EMBO J, 1997 May 15, 16(10), 2717 - 29
Modulation of bacterial entry into epithelial cells by association between vinculin and the Shigella IpaA invasin; Tran Van Nhieu G et al.; Shigella flexneri is the causative agent of bacillary dysentery in humans . Shigella invasion of epithelial cells is characterized by cytoskeletal rearrangements and formation of cellular projections engulfing the bacterium in a macropinocytic process . We show here that vinculin, a protein involved in linking actin filaments to the plasma membrane, is a direct target of Shigella during cell invasion . IpaA, a Shigella protein secreted upon cell contact, rapidly associates with vinculin during bacterial invasion . Although defective for cell entry, an ipaA mutant is still able to induce foci of actin polymerization, but differs from wild-type Shigella in its ability to recruit vinculin and alpha-actinin . Presumably, IpaA-vinculin interaction initiates the formation of focal adhesion-like structures required for efficient invasion.

Diagn Microbiol Infect Dis, 1997 May, 28(1), 19 - 25
A simple polymerase chain reaction technique to detect and differentiate Shigella and enteroinvasive Escherichia coli in human feces; Houng HS et al.; A simple polymerase chain reaction (PCR) procedure using IS630-specific primers was developed as a general diagnostic probe to detect Shigella and enteroinvasive Escherichia coli (EIEC) . However, IS630 and the other two previously reported molecular probes, ipaH and ial, cannot be used to differentiate among Shigella serotypes and EIEC strains that cause dysentery . The sensitivity of PCR protocol was determined to be 100-200 shigellae for each PCR reaction . An enrichment incubation would allow the detection of shigellae in stool samples with low bacterial concentration; i.e., < 10(4) CFU/gram . Serotype-specific primers derived from the rfc genes of differentiate among Shigella serotypes in the laboratory, such as S . sonnei, S . flexneri, and S . dysenteriae 1 . It was demonstrated further that the multiplex PCR system containing rfc-specific primers can efficiently identify the most prominent Shigella serotypes in raw stool samples of acute diarrheal patients.

Kansenshogaku Zasshi, 1997 May, 71(5), 412 - 6
{Shigella dysenteriae strains possessing a new serovar isolated from imported diarrheal cases in Japan}; Matsushita S et al.; Two Shigella strains (93-119 and 95-619) isolated from stool cultures of imported diarrheal cases in Japan, did not react to any antisera of the established SHigella serovars . These strains had the typical biochemical characteristics of Shigella dysenteriae, and were biochemically identical to each other . Both strains were positive in the Sereny test and other tests for invasiveness; these indicate that they can cause shigellosis in humans . The results of antigenic analysis showed that they did not belong to any of the recognized or provisional serovars, and were serologically indistinguishable . Strain 93-119 is designated as the test strain for this new serovar.

Mol Microbiol, 1997 May, 24(4), 779 - 91
Effect of mutations in Shigella flexneri chromosomal and plasmid-encoded lipopolysaccharide genes on invasion and serum resistance; Hong M et al.; This study shows that both length and distribution of lipopolysaccharide (LPS) are important for Shigella flexneri invasion and virulence . Mutants were generated in the chromosomal LPS synthesis genes rfa, rfb, and rol, and in a plasmid-encoded O-antigen chain-length regulator, cld(pHS-2) . LPS analysis showed that mutations in rfb genes and in a candidate rfaL gene either eliminated the entire O-antigen side chains or produced chains of greatly reduced length . Mutation in a previously unidentified gene, rfaX, affected the LPS core region and resulted in reduced amounts of O-antigen . Mutants defective in cld(pHS-2) or rol had different distributions of O-antigen chain lengths . The results of tissue-culture cell invasion and plaque assays, the Sereny test, and serum-sensitivity assay suggested roles for the different LPS synthesis genes in bacterial survival and virulence; rfaL, rfaX and rfb loci are required for serum resistance and intercellular spread, but not for invasion; cld(pHS-2) is required for resistance to serum killing and for full inflammation in the Sereny test, but not for invasion or intercellular spread, while rol is required for normal invasiveness and plaque formation, but not for serum resistance . Thus, O-antigen synthesis and chain-length regulation genes encoded on both the chromosome and the small plasmid pHS-2 play important roles in S . flexneri invasion and virulence.

Trends Microbiol, 1997 May, 5(5), 201 - 4
Apoptosis as a proinflammatory event: what can we learn from bacteria-induced cell death?
Zychlinsky A, Sansonetti PJ.
Infection of cells by some pathogenic bacteria triggers host cell apoptosis . Bacteria-induced apoptosis appears to promote an inflammatory response that causes tissue damage and further bacterial colonization . Shigella pathogenesis offers a paradigm for the role of apoptosis in bacterial infections.

Ann Intern Med, 1997 May 1, 126(9), 697 - 703
Treatment of shigellosis: V . Comparison of azithromycin and ciprofloxacin . A double-blind, randomized, controlled trial; Khan WA et al.; BACKGROUND: Treatment of shigellosis is currently limited by the high prevalence of multidrug-resistant strains of Shigella . OBJECTIVE: To determine the efficacy of azithromycin in the treatment of shigellosis . DESIGN: Randomized, double-blind clinical trial . SETTING: Diarrhea treatment center in Dhaka, Bangladesh . PATIENTS: 70 men with shigellosis that had lasted 72 hours or less . INTERVENTIONS: Patients stayed in the hospital for 6 days . Thirty-four patients were randomly assigned to receive 500 mg of azithromycin on study day 1, followed by 250 mg once daily for 4 days; 36 patients were assigned to receive 500 mg of ciprofloxacin every 12 hours for 5 days . MEASUREMENTS: Clinical treatment failure was considered to have occurred if frank dysentery persisted for 72 hours after therapy began or if on study day 5 a patient had more than six stools, had any bloody-mucoid stools, had more than one watery stool, or had an oral body temperature exceeding 37.8 degrees C . Bacteriologic treatment failure was considered to have occurred if Shigella strains could be isolated from a stool sample after study day 2 . Therapy was considered either clinically or bacteriologically successful in patients who completed therapy and did not meet criteria for failure . RESULTS: Therapy was clinically successful in 28 (82%) patients who received azithromycin and 32 (89%) patients who received ciprofloxacin (difference, -7% {95% Cl, -23% to 10%}) . Therapy was bacteriologically successful in 32 (94%) patients receiving azithromycin and 36 (100%) patients receiving ciprofloxacin (difference, -6% {Cl, -14% to 2%}) . Peak serum concentrations of azithromycin were equal to the minimum inhibitory concentration (MIC) of the infecting Shigella strains, whereas serum concentrations of ciprofloxacin were 28 times the MIC . Stool concentrations of both drugs were more than 200 times the MIC . CONCLUSION: Azithromycin is effective in the treatment of moderate to severe shigellosis caused by multidrug-resistant Shigella strains.

J Infect Dis, 1997 May, 175(5), 1128 - 33
Characterization and quantitative analysis of serum IgG class and subclass response to Shigella sonnei and Shigella flexneri 2a lipopolysaccharide following natural Shigella infection; Robin G et al.; The IgG subclass response to Shigella sonnei and Shigella flexneri 2a lipopolysaccharide (LPS) was examined in subjects naturally exposed to these organisms . Affinity-purified LPS antibodies obtained using a column of Shigella LPS bound to epoxy-activated Sepharose 6B were used as standards to calibrate the serum antibody response to natural Shigella infection . The geometric mean concentrations of specific IgG in sera from those not exposed to Shigella organisms were 7.9 microg/mL against S . sonnei LPS and 18.6 microg/mL against S . flexneri 2a LPS . After natural exposure to S . sonnei or S . flexneri 2a, the concentrations rose to 30.3 and 127.9 microg/mL, respectively . IgG2 was the major component in the anti-S . flexneri subclass response, while the anti-S . sonnei response was dominated by IgG1 . High levels of IgG1 antibodies before exposure to organisms from either Shigella serogroup correlated with a lower risk of developing symptomatic infection.

Infect Immun, 1997 May, 65(5), 1599 - 605
Functional analysis of the Shigella flexneri IpaC invasin by insertional mutagenesis; Barzu S et al.; The ability of Shigella to enter epithelial cells, to escape from the phagocytic vacuole, and to induce apoptosis in macrophages requires the IpaB, IpaC, and IpaD proteins . An extracellular complex containing IpaB and IpaC can promote the uptake of inert particles by epithelial cells . To determine whether the function of IpaC is to act as an extracellular chaperone for IpaB in the Ipa complex or as an effector of entry involved in a direct interaction with the cell surface, we have constructed eight IpaC recombinant proteins by inserting the coding sequence for a 12- to 14-amino-acid fragment into restriction sites scattered within the ipaC gene . We have investigated the ability of recombinant proteins to bind IpgC in the bacterial cytoplasm and IpaB in the extracellular medium and to complement an ipaC null mutant for entry into HeLa cells, lysis of erythrocytes, and escape from the phagocytic vacuole in infected macrophages . Most recombinant proteins were produced and secreted at a level similar to that of wild-type IpaC and did not exhibit altered susceptibility to proteolysis by trypsin, and all were able to bind IpgC and IpaB . Some recombinant proteins did not complement the ipaC mutant for entry into HeLa cells, lysis of erythrocytes, or escape from the phagocytic vacuole, which indicates that IpaC plays an active role in these processes and does not act solely as a chaperone for IpaB . In addition, some insertions which were located outside of the hydrophobic region of IpaC differentially affected the abilities of Shigella to enter epithelial cells and to lyse cell membranes.

J Clin Microbiol, 1997 May, 35(5), 1061 - 5
Molecular epidemiology of multiply antibiotic-resistant Shigella flexneri in Fortaleza, Brazil; Lima AA et al.; In northeastern Brazil, strains of Shigella flexneri resistant to multiple antibiotics are often found in patients in both urban areas and community hospitals . This study used pulsed-field gel electrophoresis (PFGE) and plasmid analysis to further analyze the molecular epidemiology of Shigella flexneri strains isolated from hospitals and an urban community in Fortaleza, Brazil . Twenty-six strains of S . flexneri from three distinct areas in the city of Fortaleza, Brazil, were examined: 14 strains from people with diarrhea who lived in an urban community of 2,000 persons, 5 strains from patients in the university hospital, and 7 strains from children in a pediatric hospital . PFGE identified six unique groups of S . flexneri circulating among patients during the 45-month study . Seven strains were further studied for antibiotic resistance plasmid profiles . Three unique antibiotic resistance plasmid profiles were found . Strains collected from the hospitalized patients demonstrated the variety of PFGE and antibiotic resistance patterns in the area . Strains collected from the patients living in the urban community setting demonstrated the persistence of certain PFGE patterns as well as the acquisition of multiple antibiotic resistance plasmids . Effective interventional strategies for such geographic locations as Fortaleza, Brazil, will be more complex than those for single-strain outbreak situations.

Voen Med Zh, 1997 Apr, 318(4), 42 - 6, 80
{Methodological approaches to the study and prevention of shigellosis among the troops}; Perepelkin VS; In article the methodical approaches to study of regularity of occurrence and distribution of shigellosis are revealed from positions of the theory of etiologic selectivity of main ways of transfers, its unequivalentness at the various nosologic forms of dysentery . A complex of antiepidemiologic measures under conditions of means of prophylaxis is proved . On the basis of analysis of etiologic structure of shigellosis a main problem of the Armed Forces, causing dysentery is designated.

Gut, 1997 Apr, 40(4), 505 - 11
Effect of shigella enterotoxin 1 (ShET1) on rabbit intestine in vitro and in vivo; Fasano A et al.; BACKGROUND: Shigella enterotoxin 1 is a novel enterotoxin elaborated by Shigella flexneri 2a that causes fluid accumulation in rabbit ileal loops and a rise in short circuit current in Ussing chambers . AIMS: To gain insights into the mechanism of action of shigella enterotoxin 1 . METHODS: Supernatants from genetically engineered clones either overexpressing shigella enterotoxin 1 or producing deletion mutants of the toxin were tested in rabbit ileum both in vitro and in vivo . RESULTS: In rabbit ileum shigella enterotoxin 1 induced an irreversible rise in short circuit current that was not mediated by any of the recognised intracellular mediators of secretion . Deletion of 90% of the A subunit of the holotoxin ablated its enterotoxicity . In the in vivo perfusion model, the toxin induced a time dependent decrease in water absorption, whereas no changes were detected in the segment perfused with supernatants obtained from the deletion mutant . Finally, partially purified toxin induced a dose dependent increment in short circuit current that reached its plateau at a toxin concentration of 4 x 10(-6) M . CONCLUSIONS: Shigella enterotoxin 1 induces a time and dose dependent intestinal secretion in the rabbit animal model, suggesting that it may be responsible for the watery phase of Shigella flexneri 2a infection.

Lett Appl Microbiol, 1997 Apr, 24(4), 306 - 10
A rapid sample preparation method for PCR detection of food pathogens based on buoyant density centrifugation; Lindqvist R et al.; The use of buoyant density centrifugation (BDC) to prepare samples for PCR analysis of food pathogens is described . Blue cheese and milk homogenates were inoculated with Shigella flexneri and layered on top of Percoll media . After BDC, the food homogenates remained in the upper part of the centrifuge tube, separated from the bacteria, which retained viability and were concentrated below the lighter Percoll layer . PCR inhibitors stayed in the homogenate and PCR analyses of treated samples consistently detected 10(4) cfu g-1 of blue cheese and 500 cfu ml-1 of milk, respectively . Differences in the density of live and killed Sh . flexneri and Yersinia enterocolitica were detected by BDC but were dependent on the mechanism of killing.

Mol Med, 1997 Apr, 3(4), 260 - 72
Antigen-dependent B cell differentiation in the synovial tissue of a patient with reactive arthritis; Schroder AE et al.; BACKGROUND: Reactive arthritis (ReA) can develop as a consequence of a bacterial infection with organisms such as Chlamydia trachomata, Shigella flexneri, or Yersinia enterocolitica . Although the mechanism underlying the induction of a chronic synovitis is unknown, the expression of HLA-B27 seems to play a crucial role in the etiology of the disease . Bacterial antigens induce a humoral immune response, but little is know about the impact of B cells on the inflammatory processes developing in the synovial membrane . MATERIALS AND METHODS: Cryostat sections were prepared from the synovial tissue (ST) of patients with ReA and stained with antibodies specific for T, B, and follicular dendritic cells . Lymphoid infiltrates were directly isolated by microdisection and DNA was prepared from them . The rearranged V genes were amplified by polymerase chain reaction (PCR), cloned, and sequenced . RESULTS: Histological staining showed that germinal, center-like structures develop in the ST of patients with ReA . B cells with a heterogenous repertoire were isolated from these lymphoid infiltrates . The majority of V regions carried somatic mutations indicating that sequences are derived from memory B cells . Genealogical trees demonstrate clonal expansion and diversification of the B cell repertoire in the ST . CONCLUSIONS: The finding of local V-region diversification suggests that in the ST of patients with ReA, an antigen-driven, T cell-dependent differentiation of B cells occurs . This local B cell response may contribute to the progress of the disease . Whether B cells are specific for the bacteria inducing the synovitis or for self-determinants present in the ST remains to be determined.

Infect Immun, 1997 Apr, 65(4), 1486 - 96
Human monocyte-derived macrophages infected with virulent Shigella flexneri in vitro undergo a rapid cytolytic event similar to oncosis but not apoptosis; Fernandez-Prada CM et al.; Infection of human monocyte-derived macrophages in vitro with virulent Shigella flexneri resulted in cell death which involved rupture of the plasma membrane, cell swelling, disintegration of ultrastructure, and generalized karyolysis . These features bore resemblance to oncosis and are in striking contrast to previously described observations of mouse macrophages, where a similar infection by virulent Shigella resulted in cell death by apoptosis . Cell death by oncosis in human macrophages was confirmed by lactate dehydrogenase release, light microscopy, electron microscopy, terminal deoxynucleotidyltransferase end labeling of DNA ends, DNA fragmentation assays, and fluorescence-activated cell sorter analysis of propidium-labeled nuclei . Thus, the phenomena of cell death induced by virulent Shigella in human and mouse macrophages reflect different biochemical pathways . Interleukin-1beta (IL-1beta) was released in culture supernatants of human macrophages infected with virulent bacteria . Inhibition with IL-1beta-converting enzyme inhibitors indicated, however, that this release occurred as a passive event of cell lysis . The patterns of intracellular survival of Shigella strains within human and mouse macrophages reflect differences that exist not only between Shigella serotypes but also between the two different macrophage cell types.

J Infect Dis, 1997 Apr, 175(4), 864 - 70
Characterization of endemic strains of Shigella sonnei by use of plasmid DNA analysis and pulsed-field gel electrophoresis to detect patterns of transmission; Litwin CM et al.; Shigellosis is hyperendemic in Utah . Most isolates are Shigella sonnei, making it difficult to identify epidemiologic clustering . To better define transmission, molecular markers and epidemiologic data were examined for 90 cases . Plasmid analysis and pulsed-field gel electrophoresis (PFGE) of the S . sonnei isolates identified 11 and 4 patterns, respectively . Plasmid pattern I infections occurred in 8 day care centers over a 6-month period, suggesting spread between centers . Plasmid pattern III was isolated from children at 3 additional centers and pattern IV was associated with another day care center, suggesting different outbreaks . By PFGE, plasmid groups I and XI appeared identical, as were plasmid groups II and V; plasmid group X had a unique pattern . Plasmid groups III, IV, and VII-IX were closely related PFGE subtypes . Both plasmid analysis and PFGE allow better characterization of S . sonnei transmission patterns of "endemic" strains and could lead to improved control measures.

J Bacteriol, 1997 Apr, 179(7), 2421 - 5
Influence of different rol gene products on the chain length of Shigella dysenteriae type 1 lipopolysaccharide O antigen expressed by Shigella flexneri carrier strains; Klee SR et al.; Introduction of the rol genes of Shigella dysenteriae 1 and Escherichia coli K-12 into Shigella flexneri carrier strains expressing the heterologous S . dysenteriae type 1 lipopolysaccharide resulted in the formation of longer chains of S . dysenteriae 1 O antigen . In bacteria producing both homologous and heterologous O antigen, this resulted in a reduction of the masking of heterologous O antigen by homologous lipopolysaccharide and an increased immune response induced by intraperitoneal immunization of mice by recombinant bacteria . The rol genes of S . dysenteriae 1 and E . coli K-12 were sequenced, and their gene products were compared with the S . flexneri Rol protein . The primary sequence of S . flexneri Rol differs from both E . coli K-12 and S . dysenteriae 1 Rol proteins only at positions 267 and 270, which suggests that this region may be responsible for the difference in biological activities.

Zh Mikrobiol Epidemiol Immunobiol, 1997 Mar-Apr, (2), 6 - 10
{The role of Shigella dysenteriae toxin formation at different stages in the forming of the cellular immune response in experimental animals}; Nikolaeva TN et al.; The immunomodulating action of genetically related pairs of strains of S . dysenteriae 1, differing by the presence of high molecular plasmid with a mol . wt . of 140 mD and transposon-mediated mutation in the tox-gene chromosome (4 phenotypes: Inv+ Tox+; Inv+ Tox-; Inv- Tox+; Inv- Tox-), was studied . The study was carried out with the use of the experimental intraperitoneal infection of CBA mice with live Shigella cells in a dose of 5x10(7) microbial cells . For the first time the role of Shiga toxin synthesis at different stages of the formation of cell-mediated immune response was demonstrated in vivo . This response was manifested by the stimulation of hematopoiesis, pronounced sensitization of effectors of delayed hypersensitivity and an immunomodulating effect on immunocompetent B lymphocytes, synthesizing antibodies, specific to S . dysenteriae 1 LPS and non-specific to heterologous antigen (sheep red blood cells).

East Afr Med J, 1997 Mar, 74(3), 179 - 82
Shigella serogroups identified from adult diarrhoeal out-patients in Addis Ababa, Ethiopia: antibiotic resistance and plasmid profile analysis; Mache A et al.; Fifty shigella strains were isolated from 700 diarrhoeal samples collected from adult diarrhoeal out-patients in Addis Ababa . Among the isolates, serogroup A comprised 28%, B 44%, C 18% and D 10% . Among all shigella serogroups, highest resistance was encountered to tetracycline (74%), ampicillin (70%), cephalothin (64%), trimethoprim-sulfamethoxazole (52%) and chloramphenicol (50%) while least resistance was observed to gentamicin (0%), polymyxin B (10%) and nalidixic acid (14%) . Gentamicin, polymyxin B and nalidixic acid were found to be the drugs of choice for cases of shigellosis . All drug resistant isolates analysed for plasmids contained multiple plasmids ranging from 1.8 to greater than 21 Kilobases.

East Afr Med J, 1997 Mar, 74(3), 143 - 6
Drug resistance and plasmid profile of Shigella organisms from different outbreaks in Trinidad and Tobago in 1994; Orrett FA; The plasmid profiles of 16 Shigella species isolated from cases of bacillary dysentery from different areas of Trinidad and Tobago during one calendar year, and their resistance pattern to eight antibiotics were analysed . All isolates except one S . sonneistrain, were multiple resistant . Two strains (both S . sonnei) had nine plasmid bands which were the maximum found . There were several plasmid bands common among resistant strains with multiple or single resistant profiles . Resistance to ampicillin and sulphonamide were the most common (93.8%), followed by trimethroprim (25.0%), and tetracycline (6.25%) . The results indicate that the outbreaks may not be related.

Cent Eur J Public Health, 1997 Mar, 5(1), 21 - 3
New serovars of plesiomonas shigelloides--1996; Aldova E; Eight new 0 (91-98) and H (46-49) antigens are described . Their reference strains come from Czech Republic, Cuba and USA . The majority of reference strains are of human origin . Some of the new antigens have been found in other strains coming mostly from water.

J Infect, 1997 Mar, 34(2), 107 - 11
An outbreak of Shiga bacillus dysentery in KwaZulu/Natal, South Africa; Pillay DG et al.; An outbreak of Shiga bacillus (Shigella dysenteriae type 1) infection has been detected for the first time in South Africa . Forty-eight cases of this epidemic that presented to a referral hospital were clinically evaluated . Patients presented with dysentery from all age groups and 16 (33%) were admitted to hospital . There were two geographical regions where 32 (67%) of the patients resided . The isolates were demonstrated to be pathogenic by in vitro testing for invasion and toxin production, and were found to be resistant to first line antibiotics that have been used for the treatment of shigellosis i.e . ampicillin, cotrimoxazole, tetracycline and chloramphenicol . However, they were susceptible to nalidixic acid, ceftriaxone and ciprofloxacin . Urgent, public health measures are needed to prevent further spread of this epidemic.

Am J Trop Med Hyg, 1997 Mar, 56(3), 258 - 64
Epidemiology of shigellosis among children exposed to cases of Shigella dysentery: a multivariate assessment; Ahmed F et al.; We followed 1,756 young, rural Bangladeshi children less than five years of age for one month after identification of sentinel Shigella patients in their neighborhoods . Two hundred nineteen (12%) children developed Shigella diarrhea (shigellosis) and 227 (13%) developed culture-negative dysentery . Shigella flexneri (60%) and S . dysenteriae, type 1 (15%) were the most common isolates among shigellosis cases . Within individual neighborhoods, there was poor agreement (Kappa = 0.21) between Shigella species isolated from sentinel patients and from additional cases detected during surveillance . The risk of shigellosis increased substantially after infancy and peaked in the second year of life . Severe stunting, as assessed by height-for-age, was associated with an increased risk of shigellosis (adjusted odds ratio {ORa} = 1.67, 95% confidence interval {CI} = 1.09-2.57, P < 0.05), while breast-feeding was protectively associated (ORa = 0.40, 95% CI = 0.24-0.69, P < 0.001) . Only 43% of the shigellosis cases reported bloody stools; frank dysentery occurred more frequently in S . dysenteriae 1 infections than in S . flexneri infections (ORa = 5.04, 95% CI = 1.76-14.48, P < 0.01), and was also associated with severe stunting (ORa = 2.16, 95% CI = 1.01-4.58, P < 0.05) . Our findings show that the high risk of shigellosis in residentially exposed Bangladeshi children results from multiple Shigella strains circulating concurrently within the same neighborhood; demonstrate that the risk is notably modified by host age, nutritional status, and dietary patterns; and illustrate that the classic picture of dysentery is relatively infrequent and is correlated with the infecting species and with host nutritional status.

Infection, 1997 Mar-Apr, 25(2), 106 - 8
Utilization of salivary concentrations of ciprofloxacin in subjects with cystic fibrosis; Smith A et al.; Ciprofloxacin, an orally-absorbed fluoroquinolone is effective against multiply resistant Pseudomonas aeruginosa in cystic fibrosis patients . It is the only practicable agent against extraintestinal salmonellosis and shigellosis in developing countries . However, concern with the risk of arthropathy in young children has restricted its use in pediatrics . Pharmacokinetic studies with ciprofloxacin are limited in the pediatric population . As a result, the dose and frequency of administration are not established in children . In this study the possibility of using salivary concentrations as surrogate measure of serum concentrations was investigated . A pediatric formulation of the drug (125 mg per capsule) was prepared and compared to 250 mg tablets . Relative bioavailability was 105% (tablet/capsule) . The time to peak salivary concentration and elimination rate from saliva were significantly different from serum (p < 0.01 and p < 0.05 respectively) . The linear regression analysis of post-peak concentrations in serum and saliva yielded a slope of 1.25 and correlation coefficient of 0.83 . It was also found that salivary concentrations may be contaminated from drug retained in the oral cavity . The conclusion was drawn that salivary concentrations could not be reliably used as a surrogate measure of serum levels for therapeutic drug monitoring.

Acta Paediatr, 1997 Mar, 86(3), 319 - 20
Double-blind, randomized clinical trial for safety and efficacy of norfloxacin for shigellosis in children; Bhattacharya K et al.; In a randomized, double-blind clinical trial, the efficacy and safety of norfloxacin were compared with nalidixic acid in the treatment of shigellosis in children . Out of 59 cases, Shigella spp . were isolated from 8 cases in the nalidixic acid group and 14 cases in the norfloxacin group . The norfloxacin group had significantly less duration of diarrhoea and presence of blood in stool as compared to the nalidixic acid group . No joint problem was encountered in this study at up to 4 months follow-up . Norfloxacin is safe and effective and showed no cartilage toxicity on short-term follow-up.

Nippon Rinsho, 1997 Mar, 55(3), 635 - 40
{Enterohemorrhagic Escherichia coli and its infection: from 1977 to 1995}; Takede Y; In 1997, Konowalchuk and coworkers reported a toxin produced by Escherichia coli that was cytotoxic to Vero cells . This toxin(Vero toxin, VT) was subsequently found to be an important virulence factor of E . coli associated with an outbreak of hemorrhagic colitis due to E . coli O157:H7 which occurred in the state of Oregon and Michigan in US . E . coli O157:H7 was then found to produce VT, which was cross-reactive with Shiga toxin produced by Shigella dysenteriae . VT(Shiga-like toxin Shiga toxin, Shiga toxin family) is the toxin which contributes to the symptoms of hemorrhagic colitis and hemolytic uremic syndrome . This article presents a historical perspective on EHEC and also reviews the structure and function of VT as well as epidemiological aspects of outbreak and sporadic cases of EHEC in American continent and in our county.

Mol Microbiol, 1997 Mar, 23(5), 1063 - 73
SopA, the outer membrane protease responsible for polar localization of IcsA in Shigella flexneri; Egile C et al.; The spreading ability of Shigella flexneri, a facultative intracellular Gram-negative bacterium, within the host-cell cytoplasm is the result of directional assembly and accumulation of actin filaments at one pole of the bacterium . IcsA/VirG, the 120 kDa outer membrane protein that is required for intracellular motility, is located at the pole of the bacterium where actin polymerization occurs . Bacteria growing in laboratory media and within infected cells release a certain proportion of the surface-exposed IcsA after proteolytic cleavage . In this study, we report the characterization of the sopA gene which is located on the virulence plasmid and encodes the protein responsible for the cleavage of IcsA . The deduced amino acid sequence of SopA exhibits 60% identity with those of the OmpT and OmpP outer membrane proteases of Escherichia coli . The construction and phenotypic characterization of a sopA mutant demonstrated that SopA is required for exclusive polar localization of IcsA on the bacterial surface and proper expression of the motility phenotype in infected cells.

Genetics, 1997 Mar, 145(3), 551 - 62
Bacterial interspersed mosaic elements (BIMEs) are a major source of sequence polymorphism in Escherichia coli intergenic regions including specific associations with a new insertion sequence; Bachellier S et al.; A significant fraction of Escherichia coli intergenic DNA sequences is composed of two families of repeated bacterial interspersed mosaic elements (BIME-1 and BIME-2) . In this study, we determined the sequence organization of six intergenic regions in 51 E . coli and Shigella natural isolates . Each region contains a BIME in E . coli K-12 . We found that multiple sequence variations are located within or near these BIMEs in the different bacteria . Events included excisions of a whole BIME-1, expansion/deletion within a BIME-2 and insertions of non-BIME sequences like the boxC repeat or a new IS element, named IS 1397 . Remarkably, 14 out of IS 1397 integration sites correspond to a BIME sequence, strongly suggesting that this IS element is specifically associated with BIMEs, and thus inserts only in extragenic regions . Unlike BIMEs, IS 1397 is not detected in all E . coli isolates . Possible relationships between the presence of this IS element and the evolution of BIMEs are discussed.

J Infect Dis, 1997 Mar, 175(3), 734 - 6
Entamoeba histolytica and Entamoeba dispar infection in children in Bangladesh; Haque R et al.; The prevalence of infection by the invasive parasite Entamoeba histolytica and the noninvasive parasite Entamoeba dispar was determined in 2000 children in Bangladesh . Antigen detection identified more cases of E . histolytica-E . dispar infection than did culture or microscopy . Microscopic identification of E . histolytica-E . dispar complex infection in stool did not equate with the diagnosis of amebic dysentery because most amebic infections in this population were due to E . dispar: Urban children with diarrhea had a 4.2% prevalence of E . histolytica infection and a 6.5% prevalence of E . dispar infection; rural asymptomatic children had a 1.0% prevalence of E . histolytica infection and a 7.0% prevalence of E . dispar infection . Shigella dysenteriae and Shigella flexneri infections were more frequent in children who also had Entamoeba infection, a potentially important consideration for the empiric treatment of dysentery in this population.

Schweiz Rundsch Med Prax, 1997 Feb 25, 86(9), 348 - 51
{Molecular biology detection and antibiotic sensitivities of Shigella spp . and entero-invasive Escherichia coli (EIEC) in patients returning from the tropics}; Altwegg M et al.; 1579 stool samples from patients with travel-associated diarrhea were examined by conventional culture methods to detect Shigella spp . (48 positive samples or 3.2%) and by PCR to detect shigellae and enteroinvasive Escherichia coli (EIEC) (87 positive samplers or 5.8%) . The numerical relation of shigellae to EIEC in PCR-positive samples was about 60 to 40% . However, the lack of discrimination between shigellae and EIEC is not important for the physician because the choice of antibiotics remains the same.

Mol Microbiol, 1997 Feb, 23(4), 825 - 33
Haem iron-transport system in enterohaemorrhagic Escherichia coli O157:H7; Torres AG et al.; In this study, we identified the iron-transport systems of Escherichia coli O157:H7 strain EDL933 . This strain synthesized and transported enterobactin and had a ferric citrate transport system but lacked the ability to produce or use aerobactin . It used haem and haemoglobin, but not transferrin or lactoferrin, as iron sources . We cloned the gene encoding an iron-regulated haem-transport protein and showed that this E . coli haem-utilization gene (chuA) encoded a 69 kDa outer membrane protein that was synthesized in response to iron limitation . Expression of this protein in a laboratory strain of E . coli was sufficient for utilization of haem or haemoglobin as iron sources . Mutation of the chromosomal chuA and tonB genes in E . coli O157:H7 demonstrated that the utilization of haemin and haemoglobin was ChuA- and TonB-dependent . Nucleotide sequence analysis of chuA revealed features characteristic of TonB-dependent, Fur-regulated, outer membrane iron-transport proteins . It was highly homologous to the shuA gene of Shigella dysenteriae and less closely related to hemR of Yersinia enterocolitica and hmuR of Yersinia pestis . A conserved Fur box was identified upstream of the chuA gene, and regulation by Fur was confirmed.

Mol Microbiol, 1997 Feb, 23(4), 765 - 75
Regulation of O-antigen chain length is required for Shigella flexneri virulence; Van den Bosch L et al.; It is shown that Shigella flexneri maintains genetic control over the modal chain length of the O-antigen polysaccharide chains of its lipopolysaccharide (LPS) molecules because such a distribution is required for virulence . The effect of altering O-antigen chain length on S . flexneri virulence was investigated by inserting a kanamycin (Km)-resistance cassette into the rol gene (controlling the modal O-antigen chain length distribution), and into the rfbD gene, whose product is needed for synthesis of dTDP-rhamnose (the precursor of rhamnose in the O-antigen) . The mutations had the expected effect on LPS structure . The rol::Km mutation was impaired in the ability to elicit keratoconjunctivitis, as determined by the Sereny test . The rol::Km and rfbD::Km mutations prevented plaque formation on HeLa cells, but neither mutation affected the ability of S . flexneri to invade and replicate in HeLa cells . Microscopy of bacteria-infected HeLa cells stained with fluorescein isothiocyanate (FITC)-phalloidin demonstrated that both the rol::Km and rfbD::Km mutants were defective in F-actin tall formation: the latter mutant showed distorted F-actin tails . Plasma-membrane protrusions were occasionally observed . Investigation of the location of IcsA (required for F-actin tail formation) on the cell surface by immunofluorescence and immunogold electron microscopy showed that while most rol mutant bacteria produced little or no cell-surface IcsA, 10% resembled the parental bacterial cell (which had IcsA at one cell pole; the rfbD mutant had IcsA located over its entire cell surface although it was more concentrated at one end of the cell) . That the O-antigen chains of the rol::Km mutant did not mask the IcsA protein was demonstrated by using the endorhamnosidase activity of Sf6c phage to digest the O-antigen chains, and comparing untreated and Sf6c-treated cells by immunofluorescence with anti-IcsA serum.

Mol Microbiol, 1997 Feb, 23(4), 751 - 63
Characterization of the locus encoding the Streptococcus pneumoniae type 19F capsular polysaccharide biosynthetic pathway; Morona JK et al.; We have previously reported the nucleotide sequence of the first six genes of the Streptococcus pneumoniae type 19F capsular polysaccharide biosynthesis locus (cps19f) . In this study we used plasmid insertion/rescue and inverse polymerase chain reaction (PCR) to clone an additional 10 kb downstream region containing the remainder of the cps19f locus, which was then subjected to sequence analysis . The cps19f locus is located in the S . pneumoniae chromosome between dexB and aliA, and consists of 15 open reading frames (ORFs), designated cps19fA to cps19fO, that appear to be arranged as a single transcriptional unit . Insertion-duplication mutants in seven out of the nine new ORFs have been constructed in a smooth type 19F strain, all of which resulted in a rough (nonencapsulated) phenotype, confirming that the operon is essential for capsule production . Comparison with sequence databases has allowed us to propose functions for 12 of the cps19f gene products, and a biosynthetic pathway for type 19F capsular polysaccharide . T7 expression studies confirmed that cps19fH, cps19fK, cps19fL, cps19fM and cps19fN directed the production of polypeptides of the expected size in Escherichia coli . The function of the cps19fK product was confirmed by its ability to complement a mutation in nfrC (rffE) in E . coli, as judged by restoration of sensitivity to bacteriophage N4 . Interestingly, the last four genes of the locus (cps19fL-O) exhibit very strong homology (up to 70% amino acid identity) to a portion of the Shigella flexneri rfb gene cluster encoding biosynthesis of dTDP-rhamnose . When expressed in E . coli, cps19fL-O were capable of complementing a mutation deleting the respective Shigella flexneri homologues . Southern hybridization analysis indicated that cps19fA and cps19fB were the only cps genes found in all 16 S . pneumoniae serotypes/groups tested . The region from cps19fG to cps19fK was found only in members of serogroup 19, and, within this, cps19fl was unique to type 19F.

FEMS Immunol Med Microbiol, 1997 Feb, 17(2), 73 - 8
Detection of virulent Shigella and enteroinvasive Escherichia coli by induction of the 43 kDa invasion plasmid antigen, ipaC; Shamlal R et al.; The invasion plasmid antigen, ipaC (43 kDa) of Shigella spp . and enteroinvasive Escherichia coli (EIEC) could be induced in vitro by growing them in the presence of Congo red . An enzyme-linked immunosorbent assay (ELISA) using antibodies to the 43 kDa protein of Shigella has been developed for specific detection of virulent Shigella spp and EIEC . The test is independent of initial isolation of individual colonies . As few as 10(2) CFU/ml of virulent Shigella present in mixed cultures could be detected and concurrently their susceptibility to antibiotics could be analysed after an initial growth of 8-16 h in Congo red-containing medium . The test may prove useful in the diagnosis and treatment of bacillary dysentery caused either by Shigella or EIEC through their rapid identification and proper antimicrobial therapy.

FEMS Microbiol Lett, 1997 Feb 1, 147(1), 163 - 72
Virulence gene deletion frequency is increased in Shigella flexneri following conjugation, transduction, and transformation; Porter ME et al.; Some commonly used methods for introducing DNA provoke spontaneous loss of expression of a virulence gene located on the high molecular mass plasmid in Shigella flexneri . The introduction of plasmid DNA by calcium chloride-mediated transformation in strains harbouring wild-type or mutated copies of regulatory genes resulted in the loss of expression of an mxiC-lacZ reporter gene at high frequency, approaching 100% in some cases . Lac- segregants arose whether or not the introduced plasmids harboured S . flexneri virulence gene sequences . Conjugation and generalised transduction with bacteriophage P1 were also found to provoke the appearance of Lac- mutants at high frequency . The Lac- mutants described in this report had deletions of the regulatory genes virF or virB, or more extensive deletions which included structural genes . The frequency of mutation was greatly reduced when electroporation was used to introduce DNA into the strains used in this study, suggesting that this is the best method to use when transforming them.

Antimicrob Agents Chemother, 1997 Feb, 41(2), 468 - 70
Transferable hyperproduction of TEM-1 beta-lactamase in Shigella flexneri due to a point mutation in the pribnow box; Siu LK et al.; TEM-1 hyperproduction in two ampicillin-sulbactam-resistant Shigella flexneri strains was studied . In both strains the blaTEM gene was encoded as a single copy on a large conjugatively transferable plasmid . A single G-->T transversion at position 1 of the -10 consensus sequence was identified to be the mechanism of TEM-1 hyperproduction.

Curr Opin Cell Biol, 1997 Feb, 9(1), 62 - 9
Actin and cell pathogenesis; Higley S et al.; The bacterial pathogens Listeria monocytogenes and Shigella flexneri recruit host factors that enable them to use actin polymerization as the driving force to facilitate their spread into neighbouring cells . It is now becoming clear that other pathogens, including viruses, have developed a number of different strategies to use the actin cytoskeleton of the host to their advantage during the infection process.

Infect Immun, 1997 Feb, 65(2), 818 - 21
Expression of aerobactin genes by Shigella flexneri during extracellular and intracellular growth; Headley V et al.; The expression of the Shigella flexneri chromosomal aerobactin genes during growth of the bacterium within tissue culture cells was assayed . During intracellular growth, aerobactin promoter activity was repressed relative to the level observed in bacteria grown extracellularly, even when the bacteria had been starved for iron prior to infection . Similarly, the level of one of the proteins encoded by this operon, the aerobactin outer membrane receptor, Iut, was reduced in the intracellular environment . These studies indicate that the aerobactin system is not highly expressed by bacteria within host cells, suggesting that siderophore-independent iron acquisition systems can provide essential iron during intracellular multiplication.

Infect Immun, 1997 Feb, 65(2), 801 - 5
Production of monoclonal antibodies to the non-membrane-damaging cytotoxin (NMDCY) purified from Vibrio cholerae O26 and distribution of NMDCY among strains of Vibrio cholerae and other enteric bacteria determined by monoclonal-polyclonal sandwich enzyme-linked immunosorbent assay; Saha PK et al.; The distribution of a newly described secretogenic non-membrane-damaging cytotoxin (NMDCY) among strains of Vibrio cholerae and other enteric bacteria was determined . To accomplish this, monoclonal antibodies against NMDCY were prepared and a sandwich monoclonal-polyclonal enzyme-linked immunosorbent assay (ELISA) was developed . By the sandwich ELISA, it was determined that 55.6% of the 412 strains of V . cholerae examined produced NMDCY at varying concentrations while 76, 37.9, and 15.6% of the clinical strains of Vibrio parahaemolyticus, Aeromonas spp., and Shigella spp., respectively, produced NMDCY . Because of its enterotoxigenic potential and based on its widespread distribution among strains of V . cholerae, we believe that NMDCY may constitute an important virulence determinant in the cascade of events which enable the organism to precipitate the disease.

Infect Immun, 1997 Feb, 65(2), 787 - 93
IpaB, a Shigella flexneri invasin, colocalizes with interleukin-1 beta-converting enzyme in the cytoplasm of macrophages; Thirumalai K et al.; Shigellae are the most prevalent etiological agents of dysentery . A crucial step in shigella pathogenesis is the induction of macrophage apoptosis . The invasion plasmid antigen B (IpaB) is necessary and sufficient to induce macrophage programmed cell death . IpaB activates apoptosis by binding to interleukin-1 beta (IL-1 beta)-converting enzyme (ICE) or a highly homologous protease . Here, we show that IpaB is disseminated throughout the cytoplasm of shigella-infected macrophages as detected by both immunofluorescence and immunoelectron microscopy . The cytoplasmic distribution of IpaB requires phagosome escape, and it is specific to IpaB, since lipopolysaccharide, used here as a bacterial marker, remains closely associated with the bacteria . In double-labeling experiments, we show that IpaB and ICE colocalize in the cytoplasm of the macrophage, suggesting that soon after secretion, IpaB binds to ICE to initiate apoptosis and to promote the cleavage of IL-1 beta.

Infect Immun, 1997 Feb, 65(2), 774 - 82
Secretion of Shigella flexneri Ipa invasins on contact with epithelial cells and subsequent entry of the bacterium into cells are growth stage dependent; Mounier J et al.; Upon contact with the surface of epithelial cells, Shigella flexneri secretes Ipa proteins through the Mxi-Spa type III secretion apparatus . Among the Ipa proteins, IpaB and IpaC form a soluble complex in the bacterial supernatant which appears to be sufficient to initiate the cellular rearrangements necessary to achieve bacterial entry . Here, we provide the first evidence that efficiency of bacterial entry into cells depends on the stage of bacterial growth . Bacteria in the early phase of exponential growth are six times more invasive than those in the stationary phase . The entry efficiency of the bacteria present on the cell surface appears to correlate with the percentage of those that are able to secrete their invasins . This suggests that the capacity to activate the Mxi-Spa apparatus is a major factor in the regulation of bacterial entry efficiency . Consistent with these observations, we have further shown that bacteria which have reached the stage of division secrete Ipa proteins more often than those that have not . Also, initial secretion occurs essentially in the area of the septation furrow . The Ipa proteins, secreted in the vicinity of the septation furrow, seem to initiate the early stages of reorganization of the host cell cytoskeleton.

Infect Immun, 1997 Feb, 65(2), 739 - 49
In situ characterization of inflammatory responses in the rectal mucosae of patients with shigellosis; Islam D et al.; Shigella species cause bacillary dysentery in humans by invading epithelial cells of the colonic mucosa leading to colonic epithelial cell destruction and inflammation . For further analysis of local gut inflammation, morphological changes and the potential involvement of mediators in regulatory mechanisms of cell activation and cell proliferation were studied immunohistochemically in rectal mucosal biopsies taken from patients during the acute phase of shigellosis and at convalescence . Rectal biopsies from 25 Shigella dysenteriae-1 and 10 Shigella flexneri-infected patients and from 40 controls were studied . The frequencies of proliferative cells (Ki67-positive cells), p53-immunostaining cells, and cells coexpressing Ki67 with CD3 or with p53 were analyzed . Immunostaining for the inducible nitric oxide synthase (iNOS) and the endothelial NOS was assessed . In addition, the frequencies of apoptotic cells and CD68+ cells that engulf apoptotic cells were assessed . By morphological grading, 20% of the patients had advanced inflammation (grade 3) in the acute phase; mild inflammation (grade 1) was seen in 37% of the patients at convalescence as well as in 10% of the controls . The findings in the present study suggest that in the acute phase of shigellosis inflammation is characterized by increased cell turnover in the lamina propria (LP) and the epithelium, increased iNOS expression in the surface epithelium, and apoptosis, which seems to be associated with LP macrophages . The findings also suggest that neither p53 nor iNOS are important factors for the induction of apoptosis in shigellosis . Expression of p53 may be related to early cell activation in crypt epithelium . Moreover, there is an indication of an active, low-level inflammatory process at convalescence . The results thus indicate that Shigella-induced inflammation is associated with a complex series of cellular reactions in the rectal gut mucosa which persist long after clinical symptoms have resolved.

FEBS Lett, 1997 Jan 3, 400(2), 149 - 54
Purification of IpaC, a protein involved in entry of Shigella flexneri into epithelial cells and characterization of its interaction with lipid membranes; De Geyter C et al.; Entry of Shigella flexneri into epithelial cells and lysis of the phagosome involve the secreted IpaA-D proteins . A complex containing IpaC and IpaB is able to promote uptake of inert particles by epithelial cells . This suggested that Ipa proteins, either individually or as a complex, might interact with the cell membrane . We have purified IpaC and demonstrated its interaction with lipid vesicles . This interaction is modulated by the pH, which might be relevant to the dual role of Ipa proteins, in induction of membrane ruffles upon entry and lysis of the endosome membrane thereafter.

J Biol Chem, 1997 Jan 3, 272(1), 332 - 6
Cloning, purification, and characterization of the Shigella boydii dGTP triphosphohydrolase; Quirk S et al.; The nucleotide sequence of the Shigella boydii dgt gene, which encodes the enzyme deoxyguanosine triphosphate triphosphohydrolase (dGTPase, EC 3.1.5.1), has been determined . The 1515-nucleotide Shigella dgt open reading frame has been subcloned into a T7 RNA polymerase-based expression vector . The resulting expressed protein has been purified to homogeneity using a novel single-day chromatographic regime . The protocol includes ion exchange, affinity, and hydrophobic interaction chromatography . The purified 505-amino acid (59.4 kDa) protein exists in solution as a heat-stable homotetramer, and enzymatic assays reveal that the expressed enzyme is fully active . Substrate specificity can be explained by the array of potential hydrogen bond donors/acceptors displayed on the base moiety of the (deoxy)nucleoside triphosphate . Shigella dGTPase can be inhibited by the addition of stoichiometric amounts of reducing agents . The loss of activity is both time- and concentration-dependent and is accompanied by a decrease in the thermal stability of the enzyme . Shigella dGTPase in the fully reduced form is destabilized by 1.8 kcal/mol compared with the oxidized form . Hence, disulfide bonds play a pivotal role in the maintenance of dGTPase stability and enzymatic functionality . Initial Shigella dGTPase protein crystals have been formed.

Zh Mikrobiol Epidemiol Immunobiol, 1997 Jan-Feb, (1), 31 - 5
{Shigellosis in Moscow: new trends in the epidemiological process and their social determinants}; Solodovnikov IuP et al.; In Moscow for a long time morbidity in acute enteric infections, and in Shigella infections as their main constituent, steadily decreased . In recent years the opposite tendency was noted: a rise in morbidity . A pronounced tendency for Shigella infections, especially Flexner's dysentery, to affect older ages was observed . New risk groups, including adults busy in "shuttle" commerce and different asocial elements, appeared . The number of lethal cases considerably increased . Unusual manifestations of the epidemic process are socially determined and reflect a decrease in the living standards of the population, sharp social changes in its way of life and social instability in the country . Sporadic morbidity with low focality prevails . The so-called chronic multifactor alimentary route of infection transmission is mainly realized; its neutralization presents great objective difficulties.

Plasmid, 1997, 37(3), 159 - 68
Identification of a chromosomal Shigella flexneri multi-antibiotic resistance locus which shares sequence and organizational similarity with the resistance region of the plasmid NR1; Rajakumar K et al.; The ampicillin resistance gene from Shigella flexneri 2a strain YSH6000 was cloned and shown by Southern hybridization analysis to be closely linked to the previously cloned streptomycin, chloramphenicol, and tetracycline resistance determinants, which are borne on a chromosomally integrated 99-kb element . Analysis of this chromosomal multi-antibiotic resistance locus revealed that it had a high level of sequence and organizational similarity to an equivalent region of the Shigella R-plasmid, NR1 . However, the chromosomal locus exhibited several differences, including the presence of two stretches of sequence derived from IS elements, the precise insertion of a beta-lactamase encoding oxal cassette into the Tn21-borne integron In2, a possible 17.5-kb deletion, and the loss or inactivation of the mercury resistance determinant . Based on these data, it is proposed that the chromosomal locus arose following integration of an NR1-like plasmid.

Mikrobiol Z, 1997 Jan-Feb, 59(1), 77 - 81
{The inductive immunosuppressive activity of the nonspecific lipopolysaccharide fraction of virulent Shigella sonnei}; Borisova EV et al.; The influence of lipopolysaccharide (LPS) fraction (molecular weight 50-70 kD) of virulent Shigella sonnei on bacterium ability to suppress delayed-type hypersensitivity (DTH) to xenogenic test-antigen in mice has been studied . It is found that single injection of LPS-fraction or bacteria does not inhibit DTH . Intraperitoneal injection of LPS-fraction together with avirulent S . sonnei causes DTH inhibition in mice and at the same time the injection of LPS-fraction together with Staphylococcus or Pseudomonas (extracellular parasites) does not render influence on DTH levels . There is a possibility of LPS-fraction conversion from active to non-active state and back after treatment by trichloracetic acid, phenol or redox system . It is assumed that in Shigella sonnei infection avirulent enteroinvasive bacteria can be involved in immunopathological process due to activity of non-specific fraction of S . sonnei LPS.

Cell Motil Cytoskeleton, 1997, 37(1), 44 - 53
Shigella actin-based motility in the absence of vinculin; Goldberg MB; Reports on the role of vasodilator-stimulated phosphoprotein (VASP) and proline-rich sequences in actin-based motility of Listeria and potentially of Shigella flexneri have led to the suggestion that vinculin might be an essential docking protein on the surface O2 motile Shigella . Therefore, whether vinculin had a functional role in Shigella actin-based motility was tested by examining Shigella infection of the vinculin-deficient F9 cell line variant 5.51 . Shigella are able to form actin tails and surface protrusions in 5.51 cells that are indistinguishable from those they produce in F9 cells, and Shigella rates of intracellular movement and protrusion formation are similar in the two cell lines . These data disprove the model of Shigella actin-based motility in which vinculin is an essential docking protein for either the formation of actin tails or the acceleration of motile bacteria.

Bull World Health Organ, 1997, 75(1), 45 - 53
A household survey of dysentery in Burundi: implications for the current pandemic in sub-Saharan Africa; Birmingham ME et al.; To characterize the epidemiology of dysentery (defined as bloody diarrhoea) in Burundi, we reviewed national surveillance data and conducted a household cluster survey including two case--control studies: one at the household, the other at the individual level . We estimated that community incidences for dysentery (per 1000 residents) in Kibuye Sector were 15.3 and 27.3, and that dysentery accounted for 6% and 12% of all deaths, in 1991 and 1992, respectively . Factors associated (P < or = 0.05) with contracting dysentery were being female, using a cloth rag after defecation, a history of recent weight loss, and not washing hands before preparing food . The attributable risk, at the household level, of not washing hands before preparing food was 30% . Secondary household transmission accounted for at most 11% of dysentery cases . This study suggests that Shigella dysenteriae type 1 may be one of the leading causes of preventable mortality in Burundi and other African countries where effective antimicrobial agents are no longer affordable . Since hands were the most important mode of transmission of S . dysenteriae in this study, community-based interventions aimed at increasing hand washing with soap and water, particularly after defecation and before food preparation, may be effective for controlling dysentery epidemics caused by S . dysenteriae type 1 in AfricaPIP: National surveillance data were reviewed and a household cluster survey conducted including two case-control studies at the household and individual levels to characterize the epidemiology of dysentery (bloody diarrhea) in Burundi . Community incidences for dysentery per 1000 residents in Kibuye Sector were estimated at 15.3 and 27.3, with dysentery accounting for 6% and 12% of all deaths in 1991 and 1992, respectively . Being female, using a cloth rag after defecation, a history of recent weight loss, and not washing hands before preparing food were associated with contracting dysentery . The attributable risk, at the household level, of not washing hands before preparing food was 30% . Secondary household transmission accounted for at most 11% of dysentery cases . These findings suggest that Shigella dysenteriae type one may be one of the leading causes of preventable mortality in Burundi and other African countries where effective antimicrobial agents are no longer affordable .

Arkh Patol, 1997 Jan-Feb, 59(1), 41 - 5
{Morphologic characterization of the contemporary dysentery caused by Shigella flexneri 2A}; Tsinzerling VA et al.; There is a tendency in St . Petersburg since 1990s to an increase of dysentery morbidity and lethality mainly caused by Flexner Shigella 2a . Morphology of the disease in adults is given on the material of 286 necropsies in 1993-1994 in the S . P . Botkin Infectious Hospital . Males (mean age 50 years) and among them chronic alcoholics prevailed; females (mean age 70 years) were frequently with a grave cardiovascular pathology . Advanced inflammation (fibrinous, ulcerative and hemorrhagic) of all colon and distal part of the small bowel was a common finding . Hemorrhagic infarctions of the ileum which were not described so far were observed in 10% of the cases.

S Afr Med J, 1997 Jan, 87(1), 48 - 51
Epidemic shigella dysentery in children in northern KwaZulu-Natal; Chopra M et al.; OBJECTIVES: To describe the epidemiology, clinical features, management and outcome of children with Shigella dysenteriae type I infection admitted to a rural district hospital . DESIGN: Prospective cohort study . SETTING: Hlabisa Hospital, KwaZulu-Natal . SUBJECTS: Children aged under 12 years admitted with a history of bloody mucoid diarrhoea between February and December 1995 . MAIN OUTCOME MEASURES: Number of admissions, age, sex, clinical features, complications and outcome . RESULTS: Between February and December 1995, 158 cases of bloody diarrhoea were admitted, compared with 6 the previous year . Shigella dysenteriae type I, resistant to ampicillin, tetracycline, chloramphenicol, trimethoprim and sulphamethoxazole, but susceptible to nalidixic acid and ceftriaxone, was isolated . The mean age of patients was 30 months . Patients typically presented with frequent bloody mucoid diarrhoea, fever, abdominal pain and dehydration . One hundred and sixteen (73%) recovered, 17 (11%) were transferred for tertiary care, 4 (3%) absconded, and 21 died (case fatality rate = 13%; 95% confidence interval (CI) 8-20) . Seventeen (11%) developed haemolytic uraemic syndrome and 4 (3%) a protein-losing enteropathy . The malnourished (adjusted relative risk (RR) 3.3, 95% CI 1.6-7.1; P < 0.01) and those aged less than 2 years (adjusted RR 4.2; 95% CI 1.0-17.2; P = 0.05) were more likely to die . Dysentery deaths accounted for 19% of total paediatric hospital mortality . CONCLUSION: A serious epidemic of shigella dysentery has established itself and is having a significant impact in this area . The virulence and drug resistance of the organism has resulted in high levels of morbidity and mortality . Broad public health measures will be needed to contain the epidemic . Further community-based surveillance is urgently needed, as is research to determine modes and risk factors for transmission.

J Nutr, 1997 Jan, 127(1), 51 - 4
Early feeding of an energy dense diet during acute shigellosis enhances growth in malnourished children; Mazumder RN et al.; In a controlled clinical trial, we examined the effect of the short-term feeding of an energy-dense milk cereal formula in malnourished children with clinically severe dysentery due to acute shigellosis . Seventy-five malnourished children, aged 12-48 mo, passing blood or blood with mucous in the stool for < or = 96 h, were offered a hospital diet . In addition, study children (n = 36) were offered a milk-cereal formula with an energy of 5 kJ/g (an 11% protein diet); similarly, control children (n = 39) were offered a milk-cereal formula with an energy content of 2.5 kJ/g (an 11% protein diet) . Patients were admitted to the metabolic ward of the Clinical Research and Service Centre, Dhaka, at the International Centre for Diarrhoeal Disease Research, Bangladesh . Patients were studied for 10 hospital days and were then followed up at home after 30 d . After 10 d of dietary intervention, children in the study group had a significantly greater increase vs . controls in weight-for-age (6 vs . 3%, P < 0.001) and in weight-for-height (7 vs . 3%, P < 0.001) . Serum prealbumin concentrations were significantly higher (study vs . control) after 5 d (0.214 vs . 0.170 g/L, P = 0.01) and after 10 d (0.244 vs . 0.193 g/L, P = 0.006) of the study . Greater weight-for-age was sustained at home 1 mo after discharge (8 vs . 5%, P = 0.005) from the hospital . Similarly, higher weight-for-height was sustained 1 mo after discharge (8 vs . 5%, P = 0.01) . During their stay at home, there was no dietary intervention . The results of this study suggest that short-term feeding of an energy-dense diet enhances growth in malnourished children with acute dysentery due to shigellosis.

Int J Food Microbiol, 1997 Jan, 34(1), 51 - 66
Computational neural networks for predictive microbiology . II . Application to microbial growth; Hajmeer MN et al.; The growth of a specific microorganism on a certain food is influenced by a number of environmental factors such as temperature, pH, and salt concentration . Methods that delineate the history of the growth of microorganisms are always subject to a considerable debate and scrutiny in the field of predictive microbiology . Regardless of its types, a growth model (e.g., modified Gompertz model) contains several parameters that vary depending on the microorganisms/food combination and the associated prevailing environmental conditions . The growth model parameters for a set of operating conditions are commonly determined from expressions developed via multiple linear regressions . In the present study, a substitute for the nonlinear regression-based equations is developed using computational neural networks . Computational neural networks are applied herein on experimental data pertaining to the anaerobic growth of Shigella flexneri . Results have indicated that predictions by neural networks offer better agreement with experimental data as compared to predictions obtained via corresponding regression equations.

Infect Immun, 1997 Jan, 65(1), 110 - 5
Shigella flexneri is trapped in polymorphonuclear leukocyte vacuoles and efficiently killed; Mandic-Mulec I et al.; We examined the bactericidal activity of polymorphonuclear leukocytes (PMN) against an invasive wild-type strain of Shigella flexneri (M90T) and a plasmid-cured noninvasive derivative (BS176) . Both Shigella strains, as well as a rough strain of Escherichia coli, were killed with similar efficiencies by intact inflammatory PMN in room air and under N2 (i.e., killing was O2 independent) . Bacterial killing by PMN extracts was substantially inhibited by antibodies to the bactericidal/permeability-increasing protein (BPI) . Whereas wild-type Shigella escapes from the phagosome to the cytoplasm in epithelial cells and macrophages, wild-type Shigella was trapped in the phagolysosome of PMN as visualized by electron microscopy . The efficient killing of Shigella by PMN suggests that these inflammatory cells may not only contribute initially to the severe tissue damage characteristic of shigellosis but also ultimately participate in clearance and resolution of infection.

J Biol Chem, 1996 Dec 27, 271(52), 33670 - 7
A pathogen-specific epitope inserted into recombinant secretory immunoglobulin A is immunogenic by the oral route; Corthesy B et al.; Oral administration of rabbit secretory IgA (sIgA) to adult BALB/c mice induced IgA+, IgM+, and IgG+ lymphoblasts in the Peyer's patches, whose fusion with myeloma cells resulted in hybridomas producing IgA, IgM, and IgG1 antibodies to the secretory component (SC) . This suggests that SC could serve as a vector to target protective epitopes into mucosal lymphoid tissue and elicit an immune response . We tested this concept by inserting a Shigella flexneri invasin B epitope into SC, which, following reassociation with IgA, was delivered orally to mice . To identify potential insertion sites at the surface of SC, we constructed a molecular model of the first and second Ig-like domains of rabbit SC . A surface epitope recognized by an SC-specific antibody was mapped to the loop connecting the E and F beta strands of domain I . This 8-amino acid sequence was replaced by a 9-amino acid linear epitope from S . flexneri invasin B . We found that cellular trafficking of recombinant SC produced in mammalian CV-1 cells was drastically altered and resulted in a 50-fold lower rate of secretion . However, purification of chimeric SC could be achieved by Ni2+-chelate affinity chromatoraphy . Both wild-type and chimeric SC bound to dimeric IgA, but not to monomeric IgA . Reconstituted sIgA carrying the invasin B epitope within the SC moiety triggers the appearance of seric and salivary invasin B-specific antibodies . Thus, neo-antigenized sIgA can serve as a mucosal vaccine delivery system inducing systemic and mucosal immune responses.

Ned Tijdschr Geneeskd, 1996 Dec 14, 140(50), 2510 - 3
{High percentage of antibiotic resistance in Shigella infections in children in Curaçao}; Wolfs TF et al.; OBJECTIVE: To evaluate antimicrobial treatment and resistance in clinical childhood shigellosis . DESIGN: Retrospective . SETTING: St . Elisabeth Hospital, Willemstad, Curacao, Dutch Antilles . METHOD: From September 1991 through August 1995 shigellosis was diagnosed in 93 children out of 456 hospitalised with gastroenteritis (S . flexneri in 60, S . sonnei in 32, S . dysenteriae in 1) . From hospital and laboratory records, the clinical presentation, antibiotic treatment and duration of hospitalization were indexed as well as the antibacterial resistance pattern of shigellae . RESULTS: Of the hospitalised children 52 (56%) were treated with antibiotics . Ampicillin was given most frequently (71%), followed by the combination trimethoprim-sulfamethoxazole (25%) . Isolated shigellae were resistant to ampicillin in 52% and to trimethoprim-sulfamethoxazole in 34%; 42% of the antibiotic treatments were in accordance with susceptibility of the isolated Shigella . CONCLUSION: A high percentage of shigellae isolated on Curacao was resistant to the most frequently used antibiotics ampicillin and trimethoprim-sulfamethoxazole.

Kansenshogaku Zasshi, 1996 Dec, 70(12), 1266 - 70
{Rapid detection of the hemolysin genes in Aeromonas sobria by the polymerase chain reaction}; Shibata M et al.; The hemolysin of Aeromonas sobria is one of the important virulence factors in this organism . Rapid detection and identification test for A . sobria is important for early and specific diagnosis of this infectious disease . We evaluated the polymerase chain reaction (PCR) for the rapid detection of A . sobria . Two pairs of synthetic oligonucleotide primers (ASA1-s and a; AerAAS-s and a) were used in PCR technique to detect the different hemolysin genes (ASA1 and aerAAS) in A . sobria . The PCR identified 91% of ASA1-positive and 23.4% of aerAAS-positive strains in beta-hemolytic A . sobria . Other species of Aeromonas, Plesiomonas shigelloides, Vibrio cholerae O1 and V . parahaemolyticus tested were negative in the PCR with two pairs of primers . The PCR technique for detection of two hemolysin genes suggested the possibility of application of this method for detection of A . sobria in A . sobria-associated infections.

Isr J Med Sci, 1996 Dec, 32(12), 1271 - 5
Induction of tumor necrosis factor and nitric oxide by Shigella strains isolated from patients with or without neurologic manifestations; Mor M et al.; The pathogenesis of the Shigella-associated neurological symptoms is unclear . We examined the potential role of host factors . Sonicates of Shigella strains isolated from children with and without neurologic disturbances were compared regarding their ability to induce tumor necrosis factor (TNF) and nitric oxide (NO) in vitro, in mouse macrophage J744 cell line . The mean concentrations of TNF (14.6 vs . 4.4 ng/ml) and NO (7.4 vs . 3.7 microM) induced were higher in response to strains isolated from children with neurologic complications; the differences were not statistically significant . TNF was also measured in plasma of children with shigellosis, and was found to be elevated in all patients . The mean concentration of TNF in plasma of children with neurologic manifestations was higher than that of children with no neurologic symptoms (450 vs . 138 pg/ml, P <0.05) . It is concluded that TNF and NO may play a role in the development of neurologic manifestations of shigellosis.

Protein Expr Purif, 1996 Dec, 8(4), 401 - 8
Cloning, expression, and affinity purification of recombinant Shigella flexneri invasion plasmid antigens IpaB and IpaC; Picking WL et al.; Shigella flexneri and related enteropathogenic bacteria are important agents of bacillary dysentery, a potentially life-threatening illness for children in underdeveloped regions of the world . Onset of shigellosis stems from S . flexneri invasion of colonic epithelial cells, leading to localized cell death and inflammation . Invasion plasmid antigens (Ipa) B, C, and D are three secreted proteins encoded by the large virulence plasmid of S . flexneri that have been implicated as essential effectors of this cell invasion process . These proteins are expressed as part of the ipa operon and are among the major targets of the host immune response to shigellosis . Biochemical characterization of the Ipa invasins has been complicated by the fact they have not been purified in the quantities needed for detailed in vitro analysis . Here we describe the first cloning, expression, and extensive purification of IpaB and IpaC fusion proteins from Escherichia coli for use in dissecting of the protein biochemistry of S . flexneri pathogenesis . A variety of approaches were used to prepare significant quantities of these proteins in their soluble forms, including the use of different host cell lines, modification of bacterial growth conditions, and the use of alternative plasmid expression vectors . Now that these Ipa proteins are available in a highly pure form, it will be possible to initiate studies on their important biological and immunological properties as well as their recruitment into high-molecular-weight protein complexes . Together with IpaD (purified as part of a previous study), these purified proteins will be useful for: (a) exploring properties of the host immune response to S . flexneri invasion, (b) elucidating the specific biochemical properties that lead to pathogen internalization, (c) analyzing the importance of specific Ipa protein complexes in host cell invasions, and (d) monitoring, or perhaps even augmenting, the efficacy of live oral vaccines in human trials.

Infect Immun, 1996 Dec, 64(12), 5357 - 65
In vivo apoptosis in Shigella flexneri infections; Zychlinsky A et al.; Shigella flexneri, an etiological agent of bacillary dysentery, causes apoptosis in vitro . Here we show that it also induces apoptosis in vivo . We were able to quantify the number of apoptotic cells in rabbit Peyer's patches infected with S . flexneri by detecting cells with fragmented DNA . Infection with virulent S . flexneri results in massive numbers of apoptotic cells within the lymphoid follicles . In contrast, neither an avirulent strain nor an avirulent strain capable of colonizing Peyer's patches increases the background level of apoptotic cells . Macrophages, T cells, and B cells are shown to undergo apoptosis in vivo . These results indicate that apoptosis may play a crucial role in the pathogenesis of shigellosis.

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