Infect Immun, 1998 May, 66(5), 2368 - 73 Roles for tumor necrosis factor and gamma interferon in resistance to enteric listeriosis; Beretich GR Jr et al.; Listeria monocytogenes normally infects the host by translocating from the intestinal lumen . Experiments were carried out to determine if, when, and where tumor necrosis factor (TNF) and gamma interferon (IFN-gamma) function in antibacterial resistance during enteric listeriosis . Groups of normal mice and severe combined immunodeficient (SCID) mice were injected with neutralizing monoclonal antibodies (MAb) specific for each cytokine and then inoculated intragastrically with L . monocytogenes . The course of infection was monitored by enumerating listeriae in gut-associated lymphoid tissues, livers, and spleens . By the third day of infection, bacterial numbers in infected tissues and organs were greatly exacerbated in all mice treated with anti-TNF MAb, whereas bacterial numbers in the organs of mice treated with anti-IFN-gamma MAb did not differ from those present in the respective organs of control mice . However, by the fifth day of infection, bacterial numbers in the organs of anti-IFN-gamma MAb-treated normal mice and SCID mice were much greater than in the corresponding organs of control mice . Experiments with Listeria-immune mice revealed that TNF and IFN-gamma are involved in the expression of anti-Listeria memory immunity; however, it was also found that the anti-IFN-gamma MAb was relatively ineffective in inhibiting the expression of anti-Listeria immunity, whereas a polyclonal anti-IFN-gamma was quite effective. J Clin Microbiol, 1998 May, 36(5), 1318 - 23 Computerized analysis of restriction fragment length polymorphism patterns: comparative evaluation of two commercial software packages; Gerner-Smidt P et al.; Two computerized restriction fragment length polymorphism pattern analysis systems, the BioImage system and the GelCompar system (Molecular Analyst Fingerprinting Plus in the United States), were compared . The two systems use different approaches to compare patterns from different gels . In GelCompar, a standard reference pattern in one gel is used to normalize subsequent gels containing lanes with the same reference pattern . In BioImage, the molecular sizes of the fragments are calculated from size standards present in each gel . The molecular size estimates obtained with the two systems for 12 restriction fragments of phage lambda were between 97 and 101% of their actual sizes, with a standard deviation of less than 1% of the average estimated size for most fragments . At the window sizes used for analysis, the GelCompar system performed somewhat better than BioImage in identifying visually identical patterns generated by electrophoretic separation of HhaI-restricted DNA of Listeria monocytogenes . Both systems require the user to make critical decisions in the analysis . It is very important to visually verify that the systems are finding all bands in each lane and that no artifacts are being detected; both systems allow manual editing . It is also important to verify results obtained in the pattern matching or clustering portions of the analysis. J Immunol, 1998 May 1, 160(9), 4441 - 8 MHC class I/peptide stability: implications for immunodominance, in vitro proliferation, and diversity of responding CTL; Busch DH et al.; Infection of BALB/c mice with Listeria monocytogenes primes CD8+ cytotoxic T cells specific for four different H2-Kd-restricted peptides . In vitro restimulation of L . monocytogenes immune splenocytes with each of these peptides resulted in larger T cell responses to p60 217-225 and mpl 84-92 than to LLO 91-99 and p60 449-457 . Direct frequency analyses of immune splenocytes, however, revealed that LLO 91-99 and p60 217-225 elicit dominant T cell responses, while p60 449-457 and mpl 84-92 elicit minor, subdominant responses . Restimulation of immune splenocytes with a range of peptide concentrations revealed that T cells with dominant specificities respond optimally to low peptide concentrations, while T cells specific for subdominant epitopes expand maximally to high peptide concentrations . This disparity correlates with the stability of H2-Kd/epitope complexes: the two dominant epitopes form stable complexes, while the subdominant epitopes form less stable complexes with H2-Kd . Interestingly, T cells specific for LLO 91-99 and p60 217-225 express more complex TCR-Vbeta repertoires than p60 449-457- and mpl 84-92-specific T cells . Thus, in our system, dominant T cell responses have relatively diverse TCR repertoires and are specific for peptides that form stable complexes with MHC class I molecules . Determining the precise roles of epitope/MHC class I stability and TCR repertoire in the generation of dominant T cell responses will require further investigation. Infect Immun, 1998 May, 66(5), 2284 - 9 Disruption of the cellular inflammatory response to Listeria monocytogenes infection in mice with disruptions in targeted genes; DiTirro J et al.; The results of this study to dissect the nature of the acquired immune response to infection with Listeria monocytogenes in mice with targetted gene disruptions show that successful resolution of disease requires the essential presence of alphabeta T cells and the capacity to elaborate gamma interferon . In the absence of either of these entities, mice experience increasingly severe hepatitis and tissue necrosis and die within a few days . The data from this study support the hypothesis that the protective process is the efficient replacement of neutrophils in lesions by longer-lived mononuclear phagocytes; alphabeta-T-cell-knockout mice died from progressive infection before neutrophil replacement could occur, whereas in gammadelta-T-cell-knockout mice this replacement process in the liver has previously been shown to be much slower . In the present study we attribute this delay to reduced production of the macrophage-attracting chemokine MCP-1 in the gammadelta-T-cell-knockout animals . These data further support the hypothesis that gammadelta T cells are important in controlling the inflammatory process rather than being essential to the expression of protection. Infect Immun, 1998 May, 66(5), 2200 - 6 Production of proinflammatory cytokines and inflammatory mediators in human intestinal epithelial cells after invasion by Trichinella spiralis; Li CK et al.; Epithelial cells are the first point of host contact for invasive intestinal pathogens and may initiate mucosal inflammatory responses via production of proinflammatory cytokines and mediators . The aim of the present study was to investigate in vitro the initial invasion of a parasitic nematode (Trichinella spiralis), to measure the early production of specific epithelial cytokines and inflammatory mediators after invasion, and to compare these responses with those to invasive bacteria . Monolayers of human colonic epithelial cell lines (HT29, T84, and Caco-2) were infected by T . spiralis or Listeria monocytogenes . Bile-activated infective larvae of T . spiralis invaded and migrated into the epithelial cell monolayers, leaving trails of dead cells . Transmission electron microscopy studies of damaged cells along the trail showed a progressive increase in size, disruption of cell membranes, loss or dilution of cytoplasmic proteins, and swelling of mitochondria and nuclei . However, no nuclear fragmentation was observed . With reverse transcription-PCR and an enzyme-linked oligonucleotide chemiluminescent assay, mRNA transcripts of interleukin-1beta (IL-1beta), IL-8, and epithelial neutrophil-activating peptide 78 were shown to increase in epithelial cells invaded by T . spiralis or L . monocytogenes, but only L . monocytogenes elicited increased inducible nitric oxide synthase (iNOS) mRNA . No increase in tumor necrosis factor alpha or transforming growth factor beta mRNA was seen after T . spiralis invasion . Increased levels of IL-8 were also released from the basolateral surfaces of infected monolayers as detected by sandwich enzyme-linked immunosorbent assay . Induction and secretion of proinflammatory cytokines in epithelial cells after nematode or bacterial invasion may initiate the acute inflammatory response of the small intestine . The upregulation of iNOS in bacterial infections may contribute to mucosal defense and may also be associated with subsequent cell death, whereas different mechanisms appear to operate after nematode invasion. Microbiol Immunol, 1998, 42(2), 129 - 32 Sequence analysis of the actA gene of Listeria monocytogenes isolated from human; Moriishi K et al.; The region encoding proline-rich units of actA genes was amplified from 24 strains of Listeria monocytogenes using polymerase chain reaction (PCR) . PCR products of 13 strains showed the expected size of 623 bp, whereas those of 11 strains showed a short size of 518 bp . The shortening of these PCR products resulted from the deletion of one proline-rich unit . These results indicate that ActA proteins are divided into at least two different types which are unrelated to bacterial serotypes. Anal Biochem, 1998 May 1, 258(2), 230 - 5 Evaluation of five imidazopyrazinone-type chemiluminescent superoxide probes and their application to the measurement of superoxide anion generated by Listeria monocytogenes; Shimomura O et al.; Superoxide-triggered chemiluminescence of five new imidazopyrazinone derivatives was investigated using the hypoxanthine-xanthine oxidase system as the source of superoxide anion . The results showed that they are highly sensitive and have favorable properties in measuring superoxide anion . With those new probes, the generation of superoxide anion from the bacteria Listeria monocytogenes was examined . The results confirmed the previous report that L . monocytogenes is an unusual organism that extracellularly and continuously generates a high level of superoxide anion in the presence of acetaldehyde . The data indicated that two of the probes, 3,7-dihydro-2-methyl-6-phenylethynylimidazo{1,2-a}pyrazin-3- one (4) and its methoxy derivative (5), are highly sensitive and useful in the measurements of superoxide anion and are clearly superior to 3,7-dihydro-2-methyl-6-(4-methoxyphenyl)imidazo{1,2-a}pyrazin-3-on e (MCLA), which-has been generally considered the most sensitive superoxide probe in the past . When tested at a probe concentration of 3.3 microM, the luminescence response and the signal-background ratio of compound 4 were 1.5 and 2.5 times those of MCLA, respectively, and the signal-background ratio of compound 5 was almost 15 times that of MCLA, though the luminescence response of this compound was slightly lower than that of MCLA . The low probe concentration used enhances the usefulness of probes in the measurements of superoxide in functioning biological systems. Mol Microbiol, 1998 Mar, 27(6), 1235 - 45 The ClpC ATPase of Listeria monocytogenes is a general stress protein required for virulence and promoting early bacterial escape from the phagosome of macrophages; Rouquette C et al.; Under stress conditions, the facultative intracellular pathogen Listeria monocytogenes produces a ClpC ATPase, which is a general stress protein encoded by clpC and belonging to the HSP-100/Clp family . A ClpC-deficient mutant was obtained by gene disruption in strain LO28, which became highly susceptible to stress conditions in vitro . Intracellular growth of this mutant was restricted within macrophages, one of the major target cells of L . monocytogenes, during the infectious process . A quantitative electron microscope study showed that, contrary to wild-type bacteria that rapidly gain access to the cytoplasm of macrophages, mutant bacteria remained confined to membrane-bound phagosomes . Only a few mutant bacteria disrupted the phagosome membrane after 4h of incubation, then polymerized actin filaments and multiplied within the cytoplasm . The ClpC ATPase, therefore, promotes early bacterial escape from the phagosome of macrophages, thus enhancing intracellular survival . The ClpC ATPase was produced in vivo during experimental infection by wild-type bacteria . The virulence of the ClpC-deficient mutant was severely attenuated in mice, with a three-log decrease in its 50% lethal dose compared with wild-type bacteria . Bacterial growth of mutant bacteria was strongly restricted in organs, presumably because of an impairment of intracellular survival in host tissues . Our results provide evidence that a general stress protein is required for the virulence of L . monocytogenes, which behaves as a virulence factor promoting intracellular survival of this pathogen. Microbiol Immunol, 1998, 42(3), 203 - 9 Protective effect of administration of skim milk on exogenous and endogenous infection in mice; Kobayashi T et al.; In order to minimize the denaturation of proteins in milk, normal cow's milk was pasteurized at 61 C for 20 min . The protective effects of the thus prepared skim milk (low-heat skim milk) on exogenous and endogenous infection were examined as compared with conventional skim milk which was pasteurized at 121 C for 2 sec . The antibody titers to Listeria monocytogenes and Escherichia coli of low-heat skim milk were almost equal to that of raw milk, while no antibody was detected in the conventional skim milk . When mice were given low-heat skim milk or conventional skim milk, the incidence of the translocation of orally inoculated Listeria monocytogenes to the spleen was lower in the low-heat skim milk group than that in the conventional skim milk group . The life span of 7 Gy X-ray irradiated mice given low-heat skim milk was significantly prolonged in comparison to that of mice given conventional skim milk . However, there were no differences in the number of bacteria in the feces or IgA production by Peyer's patch cells between the two groups . These results suggest that antibodies in low-heat skim milk, which still have reactivity to exogenous or indigenous bacteria, may contribute to the protective effects against bacterial infection. Int J Syst Bacteriol, 1998 Jan, 48 Pt 1, 127 - 39 Comparison of PCR-based DNA fingerprinting techniques for the identification of Listeria species and their use for atypical Listeria isolates; Vaneechoutte M et al.; Four PCR-based DNA fingerprinting techniques were compared for their ability to identify at the species level a heterogeneous collection of isolates belonging to the six valid Listeria species . 16S rDNA-RFLP analysis identified all species and 16S rDNA-SSCP analysis identified almost all species . Also, isolates with unusual biochemical characteristics and/or unusual antigenic composition could be identified correctly . rRNA-intracistronic length polymorphism analysis suffered from high intraspecific variability, a limited number of fragments per profile, and small length differences between the spacers of different species . tRNA-intergenic length polymorphism analysis resulted in identification of all isolates but one, when fluorescent DNA capillary electrophoresis was used such that fragment length differences of 1 bp could be resolved . The four techniques yielded comparable results relevant to the taxonomy of Listeria . They all indicate a high degree of genetic relatedness between L . innocua and L . welshimeri, homogeneity of L . grayi, distinct but clear relatedness of L . grayi to the other Listeria species, a clear distinction between the two subspecies of L . ivanovii, and a clear distinction between Listeria isolates and isolates from closely related taxa or from species which are phenotypically difficult to distinguish from Listeria . New sequence determination of the 16S rRNA gene was necessary to obtain sequences in accordance with the findings of 16S rDNA-RFLP analysis. Immunobiology, 1998 Feb, 198(4), 343 - 60 Activation and suppression of natural cellular immune functions by Pneumocystis carinii; Warschkau H et al.; The regulatory role of soluble cytokines in innate cellular immune responses induced by Pneumocystis carinii was assessed in vitro in direct comparison to induction by Listeria monocytogenes . This report shows that P . carinii organisms, as well as L . monocytogenes, stimulated in whole spleen cell cultures of SCID mice the release of IFN-gamma, TNF-alpha/beta, IL-10, IL-12, and iNO . This response was independent of functional T cells . Both macrophages (M phi) and natural killer (NK) cells were necessary for either microorganism to induce release of these cytokines . Cocultures of purified M phi--including alveolar M phi--and purified NK cells indicated that no other cell population was necessarily involved . Microbial induction of NK cell-derived IFN-gamma has been reported to be mediated by the combined effects of TNF-alpha and IL-12 released by M phi upon adequate microbial stimulation . Interestingly, only L . monocytogenes, but not P . carinii organisms could directly induce detectable amounts of TNF-alpha/beta, IL-12, or iNO in purified M phi cultures . In dose-response experiments, release of IFN-gamma, TNF-alpha/beta, and iNO was reduced at high relative concentrations of either microorganism . This high-dose suppression was at least partially controlled by M phi-produced IL-10 . Our data show that, P . carinii potently induces activating and inhibitory innate cellular immune response mechanisms and indicate that the initial step of macrophage-mediated NK cell activation might also involve other pathways than those described to date. J Vet Med Sci, 1998 Mar, 60(3), 311 - 4 Prevalence of Listeria species in raw milk from farm bulk tanks in Nagano prefecture; Yoshida T et al.; Raw milk samples from bulk tanks of a total of 943 farms, which corresponded to approximately 60% of all dairy farms in Nagano Prefecture were examined for Listeria species between December 1990 and April 1991 . Listeria spp . were isolated from 29 (3.1%) of 943 milk specimens . In the southern, central, eastern and northern areas of the prefecture, Listeria spp . were isolated from 6.1% (22/362), 1.5% (4/272), 1.4% (2/143) and 0.6% (1/166) of samples, respectively . Listeria monocytogenes was isolated from three (0.3%) bulk tanks in the southern area: two of the strains isolated from two different farm bulk tanks were serovar 4b, and the other one was 1/2a . Besides, between February 1991 and January 1992, 504 samples of raw milk from farm bulk tanks were collected nine times from 56 farms in the southern area, where the prevalence of Listeria spp . was the highest, and examined for the seasonal variation in the presence of Listeria spp . The prevalence of Listeria spp . was higher in spring (14.3%) than in autumn (4.8%) . The 56 farms were divided into three groups according to the prevalence of Listeria spp., namely, three farms in Group 1 gave a high contamination rate (50% < or =), 14 farms in Group 2 a low contamination rate and the remaining 39 farms in Group 3 no recovering of Listeria spp . Sixteen strains of L . monocytogenes serovar 4b were isolated from four farms. Jpn J Med Sci Biol, 1997 Apr, 50(2), 63 - 71 Discrimination of Listeria monocytogenes strains of serotype 4b by restriction enzyme analysis of chromosomal DNA; Saito A et al.; Epidemiologically related cheese and environmental strains and epidemiologically unrelated strains of Listeria monocytogenes serotype 4b were examined by restriction enzyme analysis of chromosomal DNA with a total of 10 restriction enzymes . The DNA fingerprint patterns generated from each restriction enzyme digest of total DNA of all strains were classified . The restriction enzyme patterns of seven strains recovered from cheese and environmental samples in the same plant were identical to each other, but differed from those of seven epidemiologically unrelated strains . Two, originating from sporadic human patients, of eight epidemiologically unrelated strains exhibited the identical restriction enzyme patterns . Excepting these two strains, restriction enzyme analysis of the chromosomal DNA of L . monocytogenes serotype 4b can discriminate serologically indistinguishable strains. J Immunol, 1998 Apr 15, 160(8), 4018 - 25 Impaired macrophage function and enhanced T cell-dependent immune response in mice lacking CCR5, the mouse homologue of the major HIV-1 coreceptor; Zhou Y et al.; The CC-chemokine receptor CCR5 has been shown to be the major coreceptor for HIV-1 entry into cells, and humans with homozygous mutation in the ccr5 gene are highly resistant to HIV-1 infection, despite the existence of many other HIV-1 coreceptors . To investigate the physiologic function of CCR5 and to understand the cellular mechanisms of these clinical observations, we generated a CCR5-deficient mouse model (ccr5{-/-}) by targeted deletion of the ccr5 gene . We found that although developed normally in a pathogen-free environment, CCR5-deficient mice showed reduced efficiency in clearance of Listeria infection and exert a protective effect against LPS-induced endotoxemia, reflecting a partial defect in macrophage function . In addition, CCR5-deficient mice had an enhanced delayed-type hypersensitivity reaction and increased humoral responses to T cell-dependent antigenic challenge, indicating a novel role of CCR5 in down-modulating T cell-dependent immune response. J Immunol, 1998 Apr 15, 160(8), 3971 - 7 Effect of antigen-processing efficiency on in vivo T cell response magnitudes; Vijh S et al.; T lymphocytes eradicate and provide long-term immunity to infections caused by intracellular pathogens . The mechanisms that determine in vivo T cell response sizes are poorly understood . Although it is speculated that the relative processing efficiency of different epitopes determines the hierarchy of T cell responses following immunization, this hypothesis has not been rigorously tested . We therefore mutagenized the secreted p60 Ag of Listeria monocytogenes to alter the efficiency of T cell epitope generation . Ag-processing efficiencies in cells infected with the different L . monocytogenes mutants ranged from one H2-Kd-associated p60 217-225 epitope generated per 15 intracellularly degraded p60 molecules (1/15) to one epitope per 350 degraded p60 molecules (1/350), i.e., a spectrum encompassing a 20-fold range of efficiencies . Mice infected with L . monocytogenes secreting inefficiently processed p60 (1/350) did not mount p60 217-225-specific T cell responses . However, increasing the efficiency of Ag processing by a factor of 5 to 1/70 restored the T cell response size to normal, while further increases in the efficiency of p60 217-225 generation to 1/50, 1/35, and 1/17 did not further augment specific T cell responses . Our studies demonstrate an Ag-processing threshold for in vivo T cell activation . Surprisingly, once this threshold is achieved, further enhancement of Ag-processing efficiency does not enhance the size of T cell responses. Eur J Epidemiol, 1998 Feb, 14(2), 205 - 10 Genetic typing of human and food isolates of Listeria monocytogenes from episodes of listeriosis; Franciosa G et al.; Ten clinical and food Listeria monocytogenes strains isolated during the epidemiological investigations of episodes of listeriosis (one outbreak and two sporadic cases) that occurred in northern Italy during 1993-1995 have been examined by DNA macrorestriction pattern analysis obtained by PFGE and RAPD typing, in order to confirm the food vehicle of infections . The same DNA profiles within the isolates from the three episodes were obtained by both techniques . The Apal and Smal PFGE profiles and RAPD patterns with primer OPM-01 confirmed the close relationship between strains from two distinct episodes . However, RAPD analysis with primer UBC-127 distinguished between these L . monocytogenes isolates. Int J Food Microbiol, 1998 Feb 17, 39(3), 231 - 6 Characterization of plasmids from Listeria monocytogenes and Listeria innocua strains isolated from short-ripened cheeses; Margolles A et al.; The plasmid content of 30 isolates of Listeria monocytogenes and 18 isolates of Listeria innocua obtained from short-ripened cheeses was analysed . The isolates of L . monocytogenes serogroup 1 harboured a single plasmid, pLM33 (33.2 kbp), whereas the serogroup 4 isolates did not contain plasmids . One group of L . innocua strains harboured the plasmid pLI71 (71 kbp) and another one contained two plasmids: pLI59 (59.5 kbp) and pLI56 (56.5 kbp) . These plasmid groups were in accordance with clusters previously defined by pulsed-field gel electrophoresis analysis of the chromosomal DNA of Listeria isolates . Plasmids pLM33, pLI71 and pLI59 shared homology regions of at least 20 kbp . Plasmid pLI56 did not encode genes for any known character (such as carbohydrate fermentation, resistance to antibiotics, heavy metals or disinfectants, growth at low pH, NaCl tolerance or thermal inactivation by pasteurisation) and displayed different characteristics to the other three plasmids . It was also the only one cured from the parent strain and the sole plasmid not digested by the restriction enzyme PstI . In addition, its lack of homology with pLM33, pLI71 and pLI59 enhanced the possibility of a different origin for plasmid pLI56. Int J Food Microbiol, 1998 Feb 17, 39(3), 167 - 73 Predictive modelling of inactivation of Listeria spp . in bovine milk during high-temperature short-time pasteurization; Piyasena P et al.; A linear model was derived to describe the thermal inactivation of Listeria innocua in bovine whole milk in a high-temperature short-time pilot scale pasteurizer . Integrated lethal effect, or pasteurization effect (PE), was obtained by converting times at different temperatures in the various sections of the pasteurizer to the equivalent time at the reference temperature (72 degrees C) . PE was then related by a simple linear function to the log10 of the % viable counts with a power transformation of the PE values to improve the linear fit . R2 values for the five L . innocua trials varied from 0.728 to 0.974 . Validation of this model with Listeria monocytogenes confirmed that L . monocytogenes was more heat sensitive . Inter-trial variation was incorporated into the model using the @RISK simulation software . Output from simulations confirmed that pasteurization at the IDF standard conditions of 72 degrees C for 15 sec can ensure at least an 11-log reduction of L . monocytogenes . The results showed that L . innocua may be used as a model microorganism to assess the thermal inactivation of L . monocytogenes, since its heat resistance is at least equal to or greater than that of the pathogenic species. J Immunol, 1998 Jan 1, 160(1), 376 - 84 Chronic Listeria infection in SCID mice: requirements for the carrier state and the dual role of T cells in transferring protection or suppression; Bhardwaj V et al.; Listeriosis in mice with the SCID mutation results in a chronic infection . The chronic infection is characterized by abundant granulomas and neutrophil infiltrates . Both lesions were particularly noticeable in the liver . In the liver, about 95% are granulomas with 5% microabscesses involving intrahepatic infection . The majority of Listeria resided in membrane-bound vacuolar structures of the macrophages and not in the cytosol . Three manipulations resulted in alterations in the equilibrium between granulomas and liver microabscesses, with massive transfer of the infection to the hepatocyte and dissolution of the granulomas: depletion of neutrophils and neutralization of IFN-gamma and TNF-alpha . We did not find a role for IL-12, IL-10, or nitric oxide . Adoptive transfer studies showed a decisive role for both CD4+ and CD8+ T cells for an effective immune response, i.e., clearance of bacteria, granuloma formation with lymphocytes, and disappearance of microabscess . Clearance of Listeria was induced by transfer of CD8+ T cells from mice with targeted disruption of the IFN-gamma structural gene (IfgTM1KO), even in the presence of neutralizing mAb to IFN-gamma . In marked contrast, transfer of CD4+ T cells from IfgTM1KO mice exacerbated the infection in the chronically infected SCID mice, resulting in increased mortality with dissolution of the granulomas and severe hepatic infection with neutrophil infiltration . Thus, these data indicate that both IFN-gamma-dependent and -independent mechanisms are operative in the context of a chronic listerial infection. J Immunol, 1998 Jan 15, 160(2), 898 - 905 Perforin-deficient CD8+ T cells provide immunity to Listeria monocytogenes by a mechanism that is independent of CD95 and IFN-gamma but requires TNF-alpha; White DW et al.; CD8+ T cells are effective mediators of immunity against Listeria monocytogenes, but the mechanisms by which they provide antilisterial immunity are poorly understood . CD8+ T cells efficiently lyse target cells in vitro by at least two independent pathways . To test the hypothesis that CD8+ T cell-mediated immunity to L . monocytogenes is dependent on perforin or CD95 (Fas, Apo-1), we used C57BI/6 (B6) and perforin-deficient (PO) mice to generate CD8+ T cell lines specific for the L . mono cytogenes-encoded Ag listeriolysin O (LLO) . Both lines specifically produce IFN-gamma and TNF-alpha, and mediate target cell lysis in vitro . Cytolysis mediated by the PO-derived CD8+ T cell line is delayed relative to the B6-derived line and is completely inhibited by anti-CD95 Abs . In vivo, PO-derived CD8+ T cells provide specific antilisterial immunity in B6 hosts, CD95-deficient hosts, and IFN-gamma-depleted hosts . However, PO-derived CD8+ T cells fail to provide antilisterial immunity in hosts depleted of TNF-alpha . These results indicate that single Ag-specific CD8+ T cells derived from PO mice can mediate antilisterial immunity by a mechanism that is independent of CD95 or IFN-gamma, but requires TNF-alpha. Dtsch Med Wochenschr, 1998 Mar 20, 123(12), 347 - 52 {Polyposis of the gastrointestinal tract as a manifestation of diffuse follicular lymphatic hyperplasia}; Storr M et al.; HISTORY AND ADMISSION FINDINGS: A 21-year-old previously healthy Turkish man who had been living in Germany for 15 years was admitted because of worsening cramp-like abdominal pain with nausea, vomiting and watery diarrhoea . Palpation elicited diffuse muscular guarding over the entire abdomen and a mass of about 8 cm in the right lower abdomen . INVESTIGATIONS: Abnormal laboratory results were erythrocyte sedimentation rate (55 mm), C-reactive protein (6.2 mg/dl), total bilirubin (2.1 mg/dl), creatine kinase (137 U/l) and thymidine kinase (5.5 U/l) . There was a slight leucocytosis (13,700/microliter) and mild anaemia (haemoglobin 13.4 g/dl) with a normal differential count . Listeria ivanovii was repeatedly cultured from stool . Ultrasonography and computed tomography of the abdomen demonstrated a 6 cm mass in the right lower abdomen, splenomegaly (15.5 x 5 cm) and several lymphomas, up to 1.8 cm in diameter . Endoscopy revealed dense, in part grass-like, polyps, 3 to 6 mm deep, in the mucosa from the terminal ileum to the rectum, and to a lesser extent also in the duodenum . Histological examination of the polyps demonstrated diffuse follicular hyperplasia without evidence of malignancy . TREATMENT AND COURSE: On antibiotic treatment with ofloxacin (2 x 400 mg intravenously) the symptoms quickly regressed, but the endoscopic findings remained unchanged . CONCLUSION: Diffuse follicular lymphatic hyperplasia manifested itself in this patient as diffuse gastrointestinal polyposis . Listeria ivanovii cannot be ruled out as a causative factor. J Immunol, 1997 Dec 15, 159(12), 5787 - 94 Evidence that the same gamma delta T cells respond during infection-induced and autoimmune inflammation; Mukasa A et al.; Inflammatory responses are induced in both testes of a mouse following injection of Listeria monocytogenes into one testis . Although the uninjected testis contains no detectable bacteria, it undergoes an autoimmune attack . Normally, the testis lacks lymphocytes, but in the infected and autoimmune state, both gamma delta and alpha beta T cells are found as infiltrates . Here, we have examined the repertoire of the infiltrating gamma delta T cells, using two different methods, and found a high frequency of V gamma 6/V delta 1 gamma delta T cells in both infected and autoimmune testes . All of these expressed the invariant V gamma 6/V delta 1 TCR previously reported . However, secondary gamma and delta transcripts present within V gamma 6/V delta 1 hybridomas indicated nonclonality . Interestingly, some of these secondary transcripts were derived from gamma gene rearrangements not previously found in this gamma delta T cell subset, implying a difference in its origin . The increase in V gamma 6/V delta 1 cells observed here in both infected and autoimmune testes, together with our previous finding of a preferential response by the same subset in Listeria-infected liver, indicates that their response is triggered by the inflammation rather than by the infectious agent or because they are already resident in the tissue . We and others have previously reported that the presence of gamma delta T cells during certain inflammatory conditions correlates with less host tissue damage . This result, together with the evidence presented here, further implies that a response by the V gamma 6/V delta 1 subset in some way exerts a controlling influence on the host inflammatory response. Vet Microbiol, 1998 Jan 16, 59(2-3), 193 - 202 The effects of inoculation of Listeria monocytogenes into the ovine mammary gland; Tzora A et al.; In each of two experiments, the effects of inoculation of Listeria monocytogenes into the ovine mammary gland were studied . In the first experiment, ewes were challenged with one or other of five different Listeria spp . isolates to study differences in their pathogenicity . In the second, ewes were challenged with L . monocytogenes serotype 1/2a to study the sequential features of the infection . The reaction of the mammary glands was assessed by bacteriological, cytological and histological methods . No distinct variation in the pathogenicity of L . monocytogenes isolates was evident: all produced subclinical mastitis, independently of their origin or serotype; a L . innocua isolate caused only a transient increase of milk somatic cell counts . After challenge, L . monocytogenes was isolated for 88 days from the milk of inoculated glands, whose milk somatic cell counts were greater than 1.0 x 10(6) cells ml-1 . The organism was also isolated from the mammary lymph nodes, but not from any internal organ of any inoculated ewe . In early stages of the infection neutrophilic infiltration was the predominant histological feature, but hyperaemia, and degeneration of alveolar epithelial cells were also recorded . Later, chronic inflammatory features predominated, with lymphocytes as the principal cell types, destruction of alveoli and fibrous tissue proliferation . In the final stage of the experiment, fibrosis was the salient finding . It is concluded that L . monocytogenes can cause subclinical mastitis after intramammary inoculation into ewes. FEMS Immunol Med Microbiol, 1998 Feb, 20(2), 159 - 64 Neuropeptides in the livers of mice during bacterial infections; Nakane A et al.; Neuropeptides such as substance P (SP) and vasoactive intestinal peptide (VIP) are known to act as immunomodulators . We investigated the induction of SP and VIP in the livers of mice infected with Listeria monocytogenes or injected with Tsukamurella paurometabolum . VIP was detected in the livers of mice after L . monocytogenes infection by an immunohistochemical technique and preproVIP mRNA, which was detected by reverse transcription-polymerase chain reaction (PCR), was induced post infection . However, no SP was detected . In contrast, SP, but not VIP was detected within granulomas in the livers of T . paurometabolum-injected mice, suggesting VIP and SP might be selectively induced in the liver by different bacterial infections. Immunology, 1998 Jan, 93(1), 73 - 9 Effect of granulocyte-macrophage colony-stimulating factor on the number of leucocytes and course of Listeria monocytogenes infection in naive and leucocytopenic mice; Buisman AM et al.; This study concerns the effect of recombinant murine granulocyte-macrophage colony-stimulating factor (GM-CSF) on the number of circulating leucocytes, activation of peritoneal macrophages and proliferation of Listeria monocytogenes in various organs of naive and leucocytopenic mice . Mice were rendered leucocytopenic by sublethal total body irradiation or cyclophosphamide treatment . GM-CSF treatment enhanced the number of granulocytes and monocytes in peripheral blood during L . monocytogenes infection in naive mice, but not in irradiated or cyclophosphamide-treated mice . In naive mice, irradiated and cyclophosphamide-treated mice, GM-CSF did not affect the course of L . monocytogenes infection in thigh muscle, spleen and liver . However, GM-CSF treatment significantly increased the number of macrophages in the peritoneal cavity of naive mice during infection; these macrophages were more enlarged and showed a higher frequency of binucleated and multinucleated cells relative to non-GM-CSF-treated mice . Together, these results demonstrated that GM-CSF increased the number of circulating granulocytes and monocytes, and the number of peritoneal macrophages during infection with L . monocytogenes in naive mice, but did not affect the course of the infection in thigh muscle, spleen or liver of these mice . In leucocytopenic mice, however, GM-CSF did not affect the number of circulating phagocytes, which explains that this factor had no effect on the proliferation of the bacteria in the various organs. Mol Microbiol, 1998 Mar, 27(5), 1077 - 87 The InIB protein of Listeria monocytogenes is sufficient to promote entry into mammalian cells; Braun L et al.; InIB is one of the two Listeria monocytogenes invasion proteins required for bacterial entry into mammalian cells . Entry into human epithelial cells such as Caco-2 requires InIA, whereas InIB is needed for entry into cultured hepatocytes and some epithelial or fibroblast cell lines such as Vero, HEp-2 and HeLa cells . InIB-mediated entry requires tyrosine phosphorylation, cytoskeletal rearrangements and activation of the host protein phosphoinositide (PI) 3-kinase, probably in response to engagement of a receptor . In this study, we demonstrate for the first time that InIB is sufficient to promote internalization . Indeed, coating of normally non-invasive bacteria or inert latex beads with InIB leads to internalization into mammalian cells . In addition, a soluble form of InIB also appears to promote uptake of non-invasive bacteria, albeit at a very low level . Similar to entry of L . monocytogenes, uptake of InIB-coated beads required tyrosine phosphorylation in the host cell, PI 3-kinase activity and cytoskeletal reorganization . Taken together, these data indicate that InIB is sufficient for entry of L . monocytogenes into host cells and suggest that this protein is an effector of host cell signalling pathways. Mol Microbiol, 1998 Mar, 27(5), 915 - 28 Differential interaction of the transcription factor PrfA and the PrfA-activating factor (Paf) of Listeria monocytogenes with target sequences; Dickneite C et al.; The interaction of the purified PrfA transcription factor with the regulatory sequences located upstream of the PrfA-dependent listeriolysin (hly) and internalin (inlA) genes was studied in the presence and in the absence of Paf (PrfA-activating factor)-containing extracts . It is shown that PrfA protein is able to bind, independently of additional factors, to a 109bp DNA fragment including the entire hly promoter sequence with the anticipated PrfA binding site ('PrfA-box') . PrfA alone, but not in combination with Paf, can also bind to a shorter target sequence of 28 bp comprising essentially the PrfA-box of the hly promoter . The addition of a Paf-containing extract does not lead to significant protein binding to these two hly target sequences in the absence of PrfA but converts the complex (CIII) consisting of PrfA and the 109 bp hly DNA fragment to a slower migrating PrfA-Paf-DNA complex (CI) . Incubation of cell-free extracts of wild-type Listeria monocytogenes with the 109 bp DNA fragment leads to the formation of CI . The addition of polyclonal PrfA antibodies causes a supershift of CIII . Purified PrfA and PrfA-Paf also bind to a DNA fragment containing the PrfA-dependent promoter P2 of inlA, albeit at a lower rate when compared with the corresponding hly sequence . In contrast to the hly target DNA, the inlA promoter sequence efficiently binds Paf alone, and this Paf binding reduces that of PrfA and PrfA-Paf to the inlA target DNA . DNase I footprint experiments show that purified PrfA protects sequences of dyad symmetry previously proposed as PrfA binding sites in the hly and in the inlA promoter regions. Microbiology, 1998 Mar, 144 ( Pt 3), 807 - 14 Determination of a 15437 bp nucleotide sequence around the inhA gene of Mycobacterium avium and similarity analysis of the products of putative ORFs; Labo M et al.; A 15437 bp region encompassing the inhA locus from the Mycobacterium avium chromosome was cloned and sequenced . From the sequencing data generated and the results of homology searches, the primary structure of this region was determined . This region contains four known genes (acnA, fabG, inhA and hemH) and two genes, invA and invB, whose products display homology with p60 invasion protein of Listeria monocytogenes . Six proteins encoded by putative ORFs contained an RGD motif (often involved in binding to macrophage integrins), while ORF1 and MoxR are probably transcriptional regulators . The rest of the putative products encoded by ORFs in the sequenced region showed little homology with the proteins contained in the databases and were considered to be unknown proteins. Int Immunol, 1998 Feb, 10(2), 117 - 30 The regulatory role of heat shock protein 70-reactive CD4+ T cells during rat listeriosis; Kimura Y et al.; Protection against infection with Listeria monocytogenes depends primarily on Listeria-specific T cells . We show here that CD4+ TCR alphabeta+ T cells are capable of recognizing the mycobacterial heat shock protein (HSP) 70, that appears in the peritoneal cavity of F344 rats infected i.p . with L . monocytogenes . The HSP70-reactive CD4+ T cells recognized a peptide comprising 234-252 residues as present in the 70 kDa HSP of Mycobacterium tuberculosis in the context of RT1.B MHC class II molecules . Analysis of TCR Vbeta gene expression with RT-PCR revealed that the HSP70-reactive CD4+ T cells predominantly used the Vbeta16 gene segment, whereas the heat-killed Listeria (HKL)-specific T cells expressed a diverse set of Vbeta gene segments . In contrast to the HKL-specific T cells producing IFN-gamma, the HSP70-reactive CD4+ T cells produced TGF-beta1 and IL-10 but neither Th1- or Th2-type cytokines . Adoptive transfer with HSP70-reactive T cells rendered rats susceptible to listerial infection . Collectively, these results proposed that the HSP70-reactive CD4+ T cells appearing during rat listeriosis may be involved in termination of Th1 cell-mediated excessive inflammation after the battle against L . monocytogenes has been won. Vet Clin North Am Food Anim Pract, 1998 Mar, 14(1), 113 - 25 Listeriosis; Cooper J et al.; Listeria monocytogenes is ubiquitous in nature and is part of the normal flora of the distal portion of the intestinal tract of numerous animal species . Listeriosis is an emerging food borne disease that is responsible for approximately 1,700 cases of human illness each year and 650 deaths . Listeria is the cause of three main disease entities in animals and humans: neural, visceral, and reproductive . Clinical signs associated with the three forms are discussed along with diagnosis, therapy, prevention, and control. Immunity, 1998 Mar, 8(3), 353 - 62 Coordinate regulation of complex T cell populations responding to bacterial infection; Busch DH et al.; Bacterial infections activate complex T cell populations that differ in size and antigen specificity . We used tetramerized MHC class I molecules complexed with Listeria monocytogenes-derived epitopes to characterize four distinct CD8+ T lymphocyte populations during bacterial infection . Surprisingly, T cell populations differing in antigen specificity expand, contract, and enter the T cell memory compartment synchronously . Because the four L . monocytogenes epitopes are presented with different efficiencies and have distinct stabilities in infected cells, our findings suggest that these factors do not determine in vivo T cell dynamics . While T cell activation requires antigen presentation, the timing and extent of T cell expansion appear to be regulated in a coordinated fashion independent of antigen quantity and stability. Microb Pathog, 1998 Jan, 24(1), 17 - 23 Mice lacking the murine interleukin-8 receptor homologue demonstrate paradoxical responses to acute and chronic experimental infection with Listeria monocytogenes; Czuprynski CJ et al.; In this study we demonstrate that mice which lack the murine interleukin-8 receptor homologue exhibit enhanced resistance during the early stage of infection (1-4 days after i.v . challenge with Listeria monocytogenes) . This result is surprising in that interleukin-8 and other CXC chemokines are key players in the accumulation of inflammatory neutrophils, which is thought to be critical for resistance to listeriosis . Paradoxically, some of the interleukin-8 receptor knockout mice that survived acute infection with L . monocytogenes demonstrated evidence of chronic infection with L . monocytogenes . J Med Microbiol, 1998 Mar, 47(3), 211 - 5 Killing mechanism of Listeria monocytogenes in activated macrophages as determined by an improved assay system; Ohya S et al.; Exposure of Listeria monocytogenes to gentamicin 5 mg/L for 4 h resulted in the killing of most extracellular bacteria, but had no effect on the survival of bacteria inside macrophages . Higher concentrations of gentamicin caused a reduction in the number of intracellular bacteria . This effect was associated with cellular uptake of gentamicin, but was unaffected by activation of macrophages by interferon-gamma and lipopolysaccharide . In experiments in which exposure to gentamicin 5 mg/L for 4 h was used to kill extracellular bacteria, killing by activated macrophages was impaired when O2- production was inhibited by superoxide dismutase, but not when nitric oxide production was blocked by NG-monomethyl-L-arginine . These data suggest that the reactive oxygen intermediates are more important than nitric oxide in the killing of L . monocytogenes, at least in macrophages activated in vitro. J Med Microbiol, 1997 Aug, 46(8), 681 - 92 Cell proliferation enhances entry of Listeria monocytogenes into intestinal epithelial cells by two proliferation-dependent entry pathways; Velge P et al.; Bacterial entry into intestinal host cells is the result of a fairly sophisticated manipulation of host cell machinery by the pathogens . To study further the potential cell target of Listeria spp., the in-vitro entry of L . monocytogenes strains into intestinal cells was examined in relation to the metabolism, proliferation and differentiation of the cells by the alamarBlue assay, {3H} thymidine incorporation, and brush border-associated enzyme activities, respectively . The study showed that cell metabolism was not involved in the entry of L . monocytogenes in three cell models (two human and one porcine) . On the other hand, entry was closely related to the proliferation process and poorly related to the differentiation state of the cells . The use of L . monocytogenes mutants lacking invasion proteins showed that InlA and InlB acted in synergy to mediate the entry of L . monocytogenes into proliferative cells, whereas InlA alone seemed to be involved in the entry into non-proliferative cells . These two entry pathways could correspond to the two cellular processes used by L . monocytogenes to enter proliferative and non-proliferative cells, as suggested by the use of cytochalasin D, nocodazole, chloroquine and monodansylcadaverine . Taken together, we propose a hypothesis in which the entry of L . monocytogenes is mediated by interaction between randomly distributed E-cadherin on the surface of proliferative cells . In contrast, the entry into non-proliferative cells may involve pp60c-src, a proto-oncogenic tyrosine kinase signal that modifies E-cadherin localisation . In conclusion, these results suggest that L . monocytogenes may preferentially enter crypt cells in vivo by a microfilament-dependent process, whereas the few bacteria that infect villus cells enter by an E-cadherin-internalin interaction that mediates microtubule-dependent endocytosis. Microb Pathog, 1997 Nov, 23(5), 255 - 63 Penetration of Listeria monocytogenes in mice infected by the oral route; Marco AJ et al.; In this study, it is suggested that the Peyer's patches are the most important point of entry of Listeria monocytogenes in the host after subclinical infection by the oral route . Microbiological, histopathological and ultrastructural evidence of infection was obtained in mice inoculated with a sublethal dose of 10(9) cfu . No mortality was observed . L . monocytogenes was isolated from the mesenteric lymph nodes from 6 hours post infection (hpi) through day 7 p.i . and from the liver and spleen from 24 h p.i . until days 5 and 7 p.i . respectively . Lesions were mainly restricted to the dome area of Peyer's patches and consisted of a purulent to pyogranulomatous inflammatory reaction . Scarce and minor lesions were also observed in the mesenteric lymph nodes and liver . L . monocytogenes was detected by immunohistochemistry in the Peyer's patches from 12 h p . i . to day 6 p.i . Ultrastructural study of Peyer's patches showed that the majority of Listeria cells were free within the cytoplasm of neutrophils and macrophages, not surrounded by a phagosomal membrane, and some of them were dividing . Int J Food Microbiol, 1997 Sep 16, 38(2-3), 217 - 27 Inhibition of Listeria monocytogenes on cold-smoked salmon by nisin and carbon dioxide atmosphere; Nilsson L et al.; The bacteriostatic and bacteriocidal effect of nisin in combination with carbon dioxide, NaCl and low temperature on the survival of Listeria monocytogenes was investigated in in vitro model studies and in trials with cold-smoked salmon . Addition of nisin caused various degrees of inhibition and sometimes death of L . monocytogenes in model experiments performed at 10 degrees C . The antilisterial effect of nisin was improved in the presence of 100% CO2 and increasing NaCl concentrations (0.5 to 5.0% w/v) . Minimal bactericidal concentrations (MBC) of nisin varied from 30 to more than 500 IU/ml . The most pronounced effect of nisin was found when 10(2) cfu/ml was grown in media with 5.0% NaCl and incubated in CO2 atmosphere (MBC = 30 IU/ml) . The bactericidal effect of nisin was reduced in air and vacuum, and did not increase systematically with increasing NaCl concentrations . In general, nisin concentration < or = 50 IU/ml resulted in the survival and growth of L . monocytogenes in all combinations with other preservatives (NaCl, CO2) . Addition of nisin (500 or 1000 IU/g) to cold-smoked salmon inoculated with L . monocytogenes and stored at 5 degrees C delayed, but did not prevent growth of L . monocytogenes in vacuum-packs . Numbers of L . monocytogenes increased to 10(8) cfu/g in vacuum packed cold-smoked salmon in 8 days, whereas CO2 packing of cold-smoked salmon resulted in an 8-day lag phase of L . monocytogenes, with numbers eventually reaching 10(6) cfu/g in 27 days . Addition of nisin to CO2 packed cold-smoked salmon resulted in a 1 to 2 log reduction of L . monocytogenes followed by a lag phase of 8 and 20 days in salmon with 500 and 1000 IU nisin/g, respectively . The levels of L . monocytogenes remained below 10(3) cfu/g during 27 days of storage at both concentrations of nisin. Int J Food Microbiol, 1997 Sep 16, 38(2-3), 157 - 67 A model describing the relationship between lag time and mild temperature increase duration; Breand S et al.; When a bacterial population undergoes an unfavourable increase in temperature for a given duration, called stress duration, a death phase followed by a lag and a growth phase are observed . The lag phase is actually of great interest in regard to foodstuff safety in choosing a suitable protocol for the detection of microorganisms which have undergone a mild heat treatment . The extension of lag time with the severity of the increase in temperature has been highlighted by previous papers . Our experimental results concerning Listeria monocytogenes and Escherichia coli revealed that a two phase relationship between lag time and stress duration is observed for a specific increase in temperature . The first phase consists of an increase in lag time up to a peak; the second one consists of a decrease from this peak to a steady threshold . The mathematical model presented, describing the relationship between lag time and stress duration was empirically built from our experimental data concerning L . monocytogenes and E . coli . The fit evaluation carried out led us to consider this model as a good description of the relationship studied . The potential contribution of our model in heat treatment optimization is discussed. Mol Cell Probes, 1997 Dec, 11(6), 459 - 62 Single-strand conformation polymorphism (SSCP) analysis of Listeria monocytogenes iap gene as tool to detect different serogroups; Manzano M et al.; PCR-single-strand conformation polymorphism (PCR-SSCP) analysis is a convenient technique for the detection of mutations . As the mobility of single-stranded DNA is sequence-dependent it could therefore be used to determine serotype-related sequence variations in Listeria monocytogenes . Sero-specific patterns were observed in different L . monocytogenes serogroups. Mol Cell Probes, 1997 Dec, 11(6), 453 - 5 A PCR-microplate capture hybridization method to detect Listeria monocytogenes in blood; Cocolin L et al.; In order to improve the diagnosis of Listeria monocytogenes infection, we have developed a polymerase chain reaction (PCR)-based assay combined with microplate capture hybridization technique . The system is based on selective amplification of L . monocytogenes with two specific primers based on the iap gene . The amplicon produced, with digoxigenin 11-dUTP incorporated during PCR, is hybridized in streptavidin-coated microtitre plates prepared with biotinylated specific DNA probe . The method involved requires approximately 6-8 h, and its high sensitivity, rapidity and simplicity should make it valuable for diagnosis and for epidemiological studies of listeriosis. Int J Food Microbiol, 1997 Aug 19, 38(1), 77 - 81 The identification of Listeria species; McLauchlin J; The purpose of this study was to compare methods for the identification of Listeria species . Three hundred and fifty cultures representing the six species of Listeria were tested using conventional sugar fermentation and haemolytic reactions, as well as the hydrolysis of the DL-alanine beta-naphthylamide (DLABN), and the API Listeria identification test kit . Using conventional tests, 99% of cultures were correctly identified: four L . monocytogenes were misidentified as L . innocua . The DLABN hydrolysis test distinguished L . monocytogenes from the remainder of the genus for 98% of the cultures: 6 out of 14 L . ivanovii isolates gave atypical results . There was correct identification for 97% of the cultures using the API Listeria test kit and no misidentifications were obtained: nine cultures (six L . monocytogenes and three L . innocua) gave equivocal profiles which were not ascribed to any species. Int J Food Microbiol, 1997 Aug 19, 38(1), 71 - 6 Addition of 2.5% lactate and 0.25% acetate controls growth of Listeria monocytogenes in vacuum-packed, sensory-acceptable servelat sausage and cooked ham stored at 4 degrees C; Blom H et al.; A study of the inhibitory effects of propylparaben and of a combination of lactate and acetate against growth of Listeria monocytogenes in inoculated liquid medium, sliced servelat sausage and cooked ham, were performed using rifampicin resistant Listeria strains in inoculation experiments . A consumer acceptance test of products produced with and without the compounds was also performed . Propylparaben was found to be effective in a model liquid non-fat medium, but was without effect in the actual products . This illustrates the potential pitfalls in translating results from studies in liquid media to fat-containing food products . The combined inhibitory and sensory results showed that a mixture of 2.5% lactate and 0.25% acetate (w/w, calculated on the water phase), could be used to increase the margins of safety for sliced and spreadable vacuum-packed ready-to-eat cooked meat products stored for 4-6 weeks . In addition, strict control of temperature during production and storage is very important. New Microbiol, 1998 Jan, 21(1), 87 - 92 Classification of Listeria monocytogenes by PCR-restriction enzyme analysis in the two genes of hlyA and iap; Saito A et al.; PCR-restriction enzyme analysis in the two virulence-associated genes was performed . The hlyA gene cording for listeriolysin O and the iap gene cording for an invasion associated factor were amplified with primers SH2 or SI3 . The PCR products obtained were cleaved with 32 restriction enzymes, and restriction profiles from 12 strains, 6 each of serotypes 1/2a and 4b, were compared . We obtained two profiles for the hlyA using 4 restriction enzymes and eight profiles for the iap by using AluI, and the results of the profiles did not correlate with the serotypes . The polymorphism in the iap region was of a higher degree than that in the hlyA region, and the PCR-restriction enzyme analysis of the iap gene with primers SI3 and AluI was confirmed as one of the useful epidemiological analysis methods for listerosis outbreaks. Indian J Dent Res, 1993 Jul-Dec, 4(3-4), 103 - 11 A comparative, qualitative and quantitative antimicrobial efficacies of mouthrinses containing chlorhexidine gluconate and essential oils; Shah HM et al.; A project was launched to evaluate and compare antimicrobial efficacy of Hexidine and Listerine over placebo in 10 day human experimental gingivitis study . A rigid study schedule for subject compliance spanning well over 3 months was sorted out and volunteers recruited for study rinsed all the 3 assigned mouthrinses containing (a) chlorhexidine gluconate, (b) "essential oils" and (c) flavoured distilled water one after the other at certain prefixed intervals . After 10 days of assigned mouthrinse regimen, where the assigned mouthrinse was the only method practiced by the volunteers for oral hygiene, Supragingival Plaque was quantitatively and qualitatively assayed . Qualitatively supragingival plaque was assayed by Gram staining (Direct smear and Thioglycollate Broth) and growth characteristics i.e; Aerobic, Microaerophilic and Anaerobic growth was noted . Quantitatively plaque was assayed by calculating total microbial load per tooth by preparing Mafarland Nephelometer standard and Spectrophotometric analysis . It is concluded that Hexidine and Listerine exert similar antimicrobial efficacy in 10 days experimental gingivitis study . Hexidine and Listerine exert their antimicrobial influence through reduction of total Aerobes and Anaerobes reducing total microbial load per tooth by 58% and 53% respectively as compared to placebo. FEMS Microbiol Lett, 1998 Mar 1, 160(1), 159 - 68 In situ detection of a virulence factor mRNA and 16S rRNA in Listeria monocytogenes; Wagner M et al.; Simultaneous in situ analysis of the structure and function of bacterial cells present within complex communities is a key for improving our understanding of microbial ecology . A protocol for the in situ identification of Listeria spp . using fluorescently tagged, rRNA-targeted oligonucleotide probes was developed . Ethanol fixation and enzymatic pretreatment with lysozyme and proteinase K were used to optimize whole cell hybridization of exponential phase and stationary phase Listeria spp . cells . In parallel, transcript probes carrying multiple digoxigenin molecules were combined with anti-digoxigenin Fab antibody fragments labeled with horseradish peroxidase to detect, via the catalytic deposition of fluorescein-tyramide, the iap-mRNA in single Listeria monocytogenes cells . The iap gene encodes the associated virulence factor p60 . Application of the new signal amplification technique resulted in strong signals comparable in intensity to those obtained with fluorescently labeled rRNA-targeted oligonucleotide probes. FEMS Microbiol Lett, 1998 Mar 1, 160(1), 87 - 90 The microtubule depolymerizing drugs nocodazole and colchicine inhibit the uptake of Listeria monocytogenes by P388D1 macrophages; Kuhn M; Uptake of Listeria monocytogenes by different mammalian cells like macrophages and epithelial cells is dependent on functional actin filaments and hence susceptible to inhibition by cytochalasin . Here we show that phagocytic uptake of L . monocytogenes by P388D1 macrophages is also highly sensitive to treatment with the microtubule depolymerizing drugs nocodazole and colchicine . This sensitivity is cell type specific and much less pronounced in bone marrow-derived macrophages and Caco-2 epithelial cells . In contrast to nocodazole and colchicine, the microtubule stabilizing drug taxol has no significant effect on the uptake of L . monocytogenes by all three cell types tested. Cell, 1998 Feb 20, 92(4), 535 - 45 Compartmentalization of bacterial antigens: differential effects on priming of CD8 T cells and protective immunity; Shen H et al.; Bacterial pathogens synthesize numerous proteins that are either secreted or localized within bacterial cells . To address the impact of antigen compartmentalization on T cell immunity, we constructed recombinant Listeria monocytogenes that express a model CD8T cell epitope as a secreted or nonsecreted fusion protein . Both forms of the antigen, either secreted into the host cell cytoplasm or retained within bacterial cells, efficiently prime CD8 T cell responses . However, epitope-specific CD8 T cells confer protection only against bacteria secreting the antigen but not against the bacteria expressing the nonsecreted form of the same antigen . This dichotomy as a result of antigen compartmentalization suggests that bacterial antigens are presented by multiple MHC class I pathways to prime CD8 T cells, but only the endogenous pathway provides target antigens for CD8 T cell-mediated protective immunity. Mol Gen Genet, 1998 Jan, 257(2), 186 - 97 Sequence comparison of the chromosomal regions encompassing the internalin C genes (inlC) of Listeria monocytogenes and L . ivanovii; Engelbrecht F et al.; We have recently cloned and characterized the inlC gene of Listeria monocytogenes which belongs to the listerial internalin multigene family and codes for a 30-kDa secreted protein containing five consecutive leucine-rich repeats . Here, we show that in L . monocytogenes inlC is located between the rplS gene (encoding the 50S ribosomal protein L19), and the infC gene (encoding the translation initiation factor 3) . By direct and inverse polymerase chain reactions (PCR), we cloned a 5.4-kb region containing a homologous gene (termed i-inlC) from L . ivanovii, the other pathogenic member of the genus Listeria . In this microorganism, the i-inlC gene is preceded by another internalin gene, i-inlD, which seems to be specific for L . ivanovii, as this gene could not be detected in L . monocytogenes by Southern hybridization with an i-inlD gene probe . The i-inlD gene also encodes a small secretory internalin (i-InlD), which shares extended homology with (i-)InlC . Upstream of i-inlD are genes for 23S rRNA and 5S rRNA, and two tRNA genes {Asn-tDNA (GTT) and Thr-tDNA(GTT)} . The 3' terminus of the Thr-tRNA gene appears to be the site of an insertion of a genetic element including i-inlC and i-inlD . A putative transcriptional regulator gene, the product of which contains the TetR family signature, is located downstream of i-inlC . This chromosomal position of the two inlC genes on their respective chromosomes may be due to horizontal transfer of this gene . Transcription of i-inlC and i-inlD is strictly dependent on the transcriptional activator PrfA, which regulates transcription of most of the known virulence genes (including inlC) of L . monocytogenes and of L . ivanovii. Lett Appl Microbiol, 1998 Jan, 26(1), 5 - 8 Fitness costs associated with class IIa bacteriocin resistance in Listeria monocytogenes B73; Dykes GA et al.; In order to assess the potential for the spread of class IIa bacteriocin resistance in natural populations of Listeria monocytogenes, the fitness costs associated with resistance to leucocins A, B and E and sakacin A in L . monocytogenes B73 in the absence of bacteriocin were examined . The resistant phenotype had a lower growth rate (and thus relative fitness) than the sensitive phenotype in monoculture experiments . Furthermore, resistant phenotypes were unable to invade populations of the sensitive strain, even at frequencies of 10(-1) or higher, when grown in co-culture . These results held true for resistant strains that had been exposed to bacteriocin for 25 successive growth cycles . It was concluded that the class IIa bacteriocin-resistant phenotype of L . monocytogenes B73 is unlikely to become stable in natural populations based on this evidence . Due to the possibility of variations in the frequencies of spontaneous mutation and fitness among Listeria strains, however, the extrapolation of these results to the species as a whole should not be made. Infect Immun, 1998 Mar, 66(3), 1106 - 12 Listeria monocytogenes invasion of epithelial cells requires the MEK-1/ERK-2 mitogen-activated protein kinase pathway; Tang P et al.; PD98059, a specific inhibitor of MEK-1 mitogen-activated protein (MAP) kinase kinase, blocked Listeria monocytogenes invasion into HeLa epithelial cells . The effects of PD98059 were reversible, as adherent extracellular bacteria were internalized upon removal of the drug . Previously, we reported that L . monocytogenes could activate ERK-1 and ERK-2 MAP kinases through the action of listeriolysin O (LLO) on the host cell (P . Tang, I . Rosenshine, P . Cossart, and B . B . Finlay, Infect . Immun . 64:2359-2361, 1996) . We have now found that two other MAP kinase pathways, those of p38 MAP kinase and c-Jun N-terminal kinase, are also activated by wild-type L . monocytogenes . Mutants lacking functional LLO (hly mutants) were still invasive but only activated ERK-2 and only activated it at later (90-min) postinfection times . Two inhibitors of L . monocytogenes invasion, cytochalasin D, which disrupts actin polymerization, and wortmannin, which blocks phosphatidylinositol (PI) 3-kinase activity, did not block ERK-2 activation by wild-type L . monocytogenes and hly mutants . However, genistein, an inhibitor of tyrosine kinases, and PD98059 both blocked invasion and decreased ERK-2 activation . These results suggest that MEK-1 and ERK-2 activities are essential for L . monocytogenes invasion into host epithelial cells . This is the first report to show that a MAP kinase pathway is required for bacterial invasion. Nat Biotechnol, 1998 Feb, 16(2), 181 - 5 Delivery of antigen-encoding plasmid DNA into the cytosol of macrophages by attenuated suicide Listeria monocytogenes; Dietrich G et al.; Eukaryotic expression vectors can be delivered to macrophages using attenuated self-destructing Listeria monocytogenes . L . monocytogenes cells are preferentially lysed in the host cell macrophage cytosol by the production of a PactA-dependent Listeria-specific phage lysin . Efficient expression of the cloned reporter genes by the macrophages and subsequent antigen presentation were achieved after the delivery of eukaryotic expression vectors by the attenuated suicide L . monocytogenes strain . After delivery by L . monocytogenes plasmid DNAs were found to integrate into the macrophage cell's genome at a frequency of about 10(-7). Curr Opin Cell Biol, 1998 Feb, 10(1), 45 - 51 Control of actin dynamics; Carlier MF; Actin-based motility processes are tightly linked to the rapid turnover of actin filaments . Factors that control the steady state of actin assembly, such as capping proteins and actin-depolymerizing factor/cofilin, directly affect motility . Actin-depolymerizing factor increases the treadmilling of actin filaments in vitro and in vivo . Cellular factors that are involved in linking initiation of barbed end assembly to cell signaling are being identified using Listeria monocytogenes and Saccharomyces cerevisiae as model systems. Trends Microbiol, 1998 Jan, 6(1), 11 - 5 Host cell signalling during Listeria monocytogenes infection; Kuhn M et al.; Macrophages and other mammalian cells respond to infection with Listeria monocytogenes by the transient or persistent activation of host cell signal transduction pathways . In addition, L . monocytogenes infection influences expression of various host cell genes, some of which may hinder or favour bacterial replication . The observed host cell responses vary with the different subcellular locations inhabited by L . monocytogenes during its intracellular life cycle. Schweiz Arch Tierheilkd, 1997, 139(11), 490 - 4 {A case of acute disseminated Mucor encephalitis in a heifer}; Schonmann M et al.; The case of a 2 1/2 year old Swiss Braunvieh heifer suffering from an acute disseminated mycotic encephalitis caused by a Mucorales spp . infection is presented . Clinical signs and analysis of cerebrospinal fluid (increased protein concentration and pleocytosis) were typical for an acute encephalitis, probably due to a listeriosis . The histological examination of the brain revealed an acute disseminated thrombo-embolic encephalomyelitis due to a fungi infection, morphologically consistent with Mucorales spp . The occurrence of bovine cerebral mucormycosis is rare and therefore the veterinarian should become aware of a case which was clinically not distinguishable from a listeriosis. Immunol Res, 1998, 17(1-2), 13 - 22 Role of gamma delta T cells in immunity to infectious diseases and the regulation of hematolymphoid cell development; Carding SR; My research interests are twofold . The first is to define the biochemical and molecular mechanisms that regulate hematopoietic cell development . In particular, the role that the cytokine interleukin-2 (IL2) plays in regulating the development and selection of lymphocyte progenitor cells, and in myelopoiesis are primary areas of research . The second is to understand the role that gamma delta T cells play in pathogen-induced immune responses and autoimmunity . Their involvement in the immune response to the intracellular bacteria Listeria monocytogenes in mice and Mycobacteria tuberculosis (Mtb) in humans, in T cell-mediated inflammatory bowel disease in humans, and the nature of the antigens they recognize during these responses are major areas of interest . Research material includes patient-derived tissues as well as both conventional and genetically engineered (transgenic) strains of mice. Biophys Chem, 1997 Oct, 68(1-3), 73 - 82 The role of actin binding proteins in epithelial morphogenesis: models based upon Listeria movement; Golsteyn RM et al.; We summarize recent findings on the organization of the protein actin in eucaryotic cells . In particular we focus on how actin can be used to generate a vectorial force that is required for cell movement . These forces arise from protein molecules that recruit actin to the plasma membrane in such a manner that actin filaments extend outward from the cell body . This type of actin dependent force generation has been described in a nucleation-release model, which is one of several models currently being tested to explain actin dependent cell movement . Data in support of this model has arisen unexpectedly from studies of an intracellular bacteria, Listeria monocytogenes . This bacteria uses actin to propel itself during infection of eucaryotic cells . By studying Listeria movement, the roles of several eucaryotic actin interacting proteins have been identified . One of these is zyxin, a human protein that shares important structural and possibly functional properties with ActA, an actin dependent force generating protein of Listeria . We intend to test the function of these and other actin interacting proteins in a simplified system that should facilitate precise measurement of their properties of force generation in vitro. Microbiology, 1998 Jan, 144 ( Pt 1), 109 - 18 Lectin reactivity and virulence among strains of Listeria monocytogenes determined in vitro using the enterocyte-like cell line Caco-2; Facinelli B et al.; Forty-six cultures of Listeria monocytogenes (including clinical, food and collection strains) were serotyped, characterized for motility, haemolysis and phospholipase activities and tested for lectin agglutination using a four-lectin set . Lectin reactivity (i.e . agglutination by one or more of the four lectins) was observed in all 12 clinical isolates, 16 of the 23 food isolates and eight of the 11 collection strains . Virulence was evaluated in vitro based on strains' ability to invade the human enterocyte-like cell line Caco-2 . In gentamicin survival experiments, recovery of viable intracellular bacteria among lectin-unreactive strains was usually 100-1000-fold lower than among lectin-reactive haemolytic strains, and lower than among nonhaemolytic strains . Considerable cytopathogenic effects were produced by lectin-reactive haemolytic strains in trypan-blue-stained cell monolayers, whereas lectin-unreactive and nonhaemolytic strains produced no detectable cytopathogenic effect . Among lectin-reactive strains, the number of listerial cells associated with Caco-2 monolayers was more than tenfold greater than among lectin-unreactive strains . Cell invasion was inhibited by pretreatment of Caco-2 cells with sugars recognized by the lectins or of listeriae with enzymes which removed the same sugars from the bacterial surface . The results suggest that the study of lectin interactions could be helpful in understanding the pathogenicity potential of isolates of food and environmental origin. Zentralbl Veterinarmed B, 1997 Dec, 44(10), 617 - 24 {Presence of Listeria monocytogenes and Listeria sp . in fresh and cured sausages . Use of different conditions of time and temperature for incubation}; Rota C et al.; Two different temperatures for enrichment of Listeria monocytogenes and related species have been studied (1) cold enrichment at 4 degrees C (2) enrichment at 30 degrees C (FDA method) . Also, two selective media for isolation were tested: Acriflavine-Ceftazidime agar (A.C.) and Palcam agar . We have studied 72 samples of dry-cured sausage (called 'longaniza') at different stages of maturation: fresh, semi-cured and cured samples . The most efficient method was cold enrichment at 4 degrees C during 5 days followed by isolation in Palcam agar, but results were only significant for fresh sausages (P < 0.05). Appl Environ Microbiol, 1998 Feb, 64(2), 800 - 3 Purification and characterization of anti-Listeria compounds produced by Geotrichum candidum; Dieuleveux V et al.; Geotrichum candidum can produce and excrete compounds that inhibit Listeria monocytogenes . These were purified by ultrafiltration, centrifugal partition chromatography, thin-layer chromatography, gel filtration, and high-pressure liquid chromatography, and analyzed by liquid chromatography-mass spectrometry, infrared spectrometry, nuclear magnetic resonance spectrometry, and optical rotation . Two inhibitors were identified: D-3-phenyllactic acid and D-3-indollactic acid. Zh Mikrobiol Epidemiol Immunobiol, 1997 Nov-Dec, (6), 68 - 70 {The effect of Listeria monocytogenes on the blood system}; Iurkina OA et al.; The influence of L . monocytogenes on the hemopoietic system was studied in mouse experiments . All elements of hemopoiesis were damaged . The most pronounced changes developed in erythropoiesis . This was testified by a decrease in erythrocyte count and hemoglobin content in peripheral blood, by the hypoplasia of the hemopoietic erythroid germ in the marrow, as well as by the decrease of yield in culture CFU-E . These changes in the hemopoietic tissue supposedly caused by the direct action of L . monocytogenes and its toxins. Zh Mikrobiol Epidemiol Immunobiol, 1997 Sep-Oct, (5), 78 - 82 {The ecological aspects of listeriosis in the Maritime Territory}; Somov GP et al.; In the process of batch cultivation the strains under study are capable of prolonged growth at low temperature in rich and poor nutrient media (with the term of observation equal to 4 months), while at a temperature of 37 degrees C microbial populations quickly die (in 8-35 days) . In the absence of compounds containing carbon, hydrogen and nitrogen in the nutrient medium, Listeria can proliferate under such conditions . As established with the use of gas chromatography and the radioisotopic method, they can uptake carbon dioxide, hydrogen and nitrogen from the air gas mixture, using carbon of the first gas for the synthesis of the main biopolymers (proteins, lipids, carbohydrates, DNA and RNA) and the second one as the source of energy . During the cultivation of Listeria at low temperature in poor nutrient media (soil microecosystems, synthetic mineral media) they are capable of preserving and under favorable conditions also increasing their virulence . Its increase is facilitated by capsule formation, mobility, chemotaxis, adhesion and invasion enhancing under such conditions. J Gen Virol, 1997 Oct, 78 ( Pt 10), 2633 - 7 Characterization of the vaccinia virus F8L protein; Higley S et al.; Vaccinia virus infection dramatically affects the host actin cytoskeleton by inducing disassembly of actin stress fibres and formation of actin tails which propel the virus intra- and intercellularly . The viral factors responsible for these actin rearrangements remain unknown . Sequence analysis reveals significant homology between the vaccinia F8L ORF and the proline repeats of iActA, the protein which initiates actin tail assembly and motility in the bacterial pathogen Listeria ivanovii . We characterized the F8L gene product to examine its possible role in vaccinia rearrangements of the host actin cytoskeleton . F8L is a approximately 8 kDa protein expressed early during infection and is found throughout the cytoplasm, with no discernible association with viral or cellular structures . Furthermore, the F8L deletion strain, WR deltaF8L, forms particles and actin tails indistinguishable from WR . Our observations demonstrate that F8L is not required for vaccinia virus morphogenesis or the actin rearrangements observed during infection. Ocul Immunol Inflamm, 1997 Dec, 5(4), 245 - 57 Immune privilege in the anterior chamber of the eye is not extended to intraocular Listeria monocytogenes; Li XY et al.; Resistance to many pathogens, such as Listeria monocytogenes, is correlated with the host's capacity to generate a ThI cell-mediated immune response in which delayed-type hypersensitivity (DTH) is activated . A wide variety of antigens induce down-regulation of DTH when introduced into the anterior chamber of the eye . This immunoregulatory phenomenon has been termed anterior chamber-associated immune deviation (ACAID) and is believed to be a primary mechanism for the immune privilege of the anterior chamber . Suppression of DTH, as a result of anterior chamber priming, could carry significant risk to the host's well-being as the resistance to many pathogens relies heavily on DTH-dependent ThI responses . Studies were performed to determine if a bacterial pathogen, L . monocytogenes, introduced into the anterior chamber of the eye would induce a down-regulation of systemic DTH . Intracameral inoculation of infectious L . monocytogenes into genetically susceptible C3H and BALB/c mice did not induce suppression of DTH, but instead resulted in a significant footpad swelling response to bacterial antigens . Likewise, intracameral inoculation of L . monocytogenes into genetically resistant C57BL/6 mice also induced vibrant bacterial-specific DTH . Using an in-vitro model of ACAID, we showed that macrophage suspensions that were simultaneously exposed to L . monocytogenes and bovine serum albumin (BSA) antigens, in the presence of aqueous humor (AH), induced listerial-specific DTH responses, yet simultaneously induced suppression of BSA-specific DTH . Collectively, the results indicate that immune privilege is not extended to all foreign antigens that enter the anterior chamber of the eye, and as a result, some intraocular antigens can provoke strong systemic DTH . However, non-ACAID-inducing antigens do not prejudice the down-regulation of DTH by other antigens which normally induce ACAID. Infect Immun, 1998 Feb, 66(2), 747 - 55 Comprehensive study of the intestinal stage of listeriosis in a rat ligated ileal loop system; Pron B et al.; The intestinal stage of listeriosis was studied in a rat ligated ileal loop system . Listeria monocytogenes translocated to deep organs with similar efficiencies after inoculation of loops with or without Peyer's patches . Bacterial seeding of deep organs was demonstrated as early as 15 min after inoculation . It was dose dependent and nonspecific, as the delta inlAB, the delta hly, and the delta actA L . monocytogenes mutants and the nonpathogenic species, Listeria innocua, translocated similarly to wild-type L . monocytogenes strains . The levels of uptake of listeriae by Peyer's patches and villous intestine were similar and low, 50 to 250 CFU per cm2 of tissue . No listeria cells crossing the epithelial sheet of Peyer's patches and villous intestine were observed by transmission electron microscopy . The lack of significant interaction of listeriae and the follicle-associated epithelium of Peyer's patches was confirmed by scanning electron microscopy . The follicular tissue of Peyer's patches was a preferential site of Listeria replication . With all doses tested, the rate of bacterial growth was 10 to 20 times higher in Peyer's patches than in villous intestine . At early stages of Peyer's patch infection, listeriae were observed inside mononuclear cells of the dome area . Listeriae then disseminated throughout the follicular tissue except for the germinal center . The virulence determinants hly and, to a lesser extent, actA, but not inlAB, were required for the completion of this process . This study suggests that Peyer's patches are preferential sites for replication rather than for entry of L . monocytogenes, due to the presence of highly permissive mononuclear cells whose nature remains to be defined. Infect Immun, 1998 Feb, 66(2), 620 - 6 The role of sialic acid in opsonin-dependent and opsonin-independent adhesion of Listeria monocytogenes to murine peritoneal macrophages; Maganti S et al.; The adhesion of listeriae to host cells employs mechanisms which are complex and not well understood . Listeria monocytogenes is a facultative intracellular pathogen responsible for meningoencephalitis, septicemia, and abortion in susceptible and immunocompromised individuals . Subsequent to colonization and penetration of the gut epithelium, the organism attaches to resident macrophages and replicates intracellularly, thus evading the humoral immune system of the infected host . The focus of these studies was to investigate the attachment of the organism to murine peritoneal macrophages in an opsonin-dependent and opsonin-independent fashion . Assessment of competitive binding experiments by immunofluorescence and enzyme-linked immunosorbent assays showed that adhesion of the organism to macrophages in the presence or absence of opsonins was inhibited (90%) by N-acetylneuraminic acid (NAcNeu) . In addition, the lectin from Maackia amurensis, with affinity for NAcNeu-alpha(2,3)galactose, blocked binding of L . monocytogenes to host cells . Oxidation of the surface carbohydrates on the organism by using sodium metaperiodate resulted in a dose-dependent reduction (up to 98%) in adherence to macrophages . Monoclonal antibody to complement receptor 3 did not prevent listeriae from binding to mouse macrophages or from replicating within the infected cells whether or not normal mouse serum was present . Based on our results, we propose the involvement of NAcNeu, a member of the sialic acid group, in the attachment of L . monocytogenes to permissive murine macrophages. FEMS Microbiol Lett, 1998 Jan 1, 158(1), 45 - 50 Evidence for expressional crosstalk between the central virulence regulator PrfA and the stress response mediator ClpC in Listeria monocytogenes; Ripio MT et al.; Virulence is a multifactorial trait which depends on the coordinated expression of many bacterial products, hence it is to be expected that the regulatory circuits that control the relevant genetic determinants are somehow interconnected . Two pleiotropic regulatory elements acting at different levels, the transcription factor PrfA which controls virulence gene expression and the potential chaperone ClpC which is involved in tolerance to environmental stress, are required for Listeria monocytogenes survival within the host . We analyzed the influence of PrfA on clpC expression in L . monocytogenes . clpC transcription is maximal under heat-shock conditions, i.e . at 42 degrees C, and is very weak or undetectable at 37 degrees C . In a prfA* mutant which constitutively overexpresses PrfA and PrfA-dependent virulence genes, clpC transcription dropped to basal levels during exponential growth at 42 degrees C . This repression was not observed during stationary phase, indicating growth phase-dependent regulation of clpC . Culture in charcoal-treated medium, which triggers in wild-type strains the transcriptional activation of the PrfA regulon, also caused a strong downregulation of clpC . Moreover, in a prfA deletion mutant, clpC transcription during exponential growth at 37 degrees C was clearly enhanced, reaching the same high levels of the wild-type at 42 degrees C . Overall, our results indicate that clpC expression is negatively controlled at the transcriptional level, directly or indirectly, by the central virulence regulator PrfA. Eur J Clin Microbiol Infect Dis, 1997 Nov, 16(11), 827 - 33 In vitro extracellular and intracellular activity of two newer and two earlier fluoroquinolones against Listeria monocytogenes; Facinelli B et al.; Two new fluoroquinolones (trovafloxacin and sparfloxacin) with enhanced activity against gram-positive pathogens and two earlier compounds (ciprofloxacin and ofloxacin) were tested for their in vitro inhibitory and bactericidal activity against 80 strains of Listeria monocytogenes . All strains were uniformly highly susceptible to trovafloxacin, the MIC90 being 0.25 mg/l . Resistance to sparfloxacin was not detected, however the MIC90 of sparfloxacin was eight times that of trovafloxacin . A few strains were resistant to ciprofloxacin and ofloxacin (MIC90 4 mg/l for both drugs) . MBCs usually exceeded MICs by 2 to 4 times . The MBC90 of trovafloxacin (1 mg/l) was lower than that of the other three drugs (8 mg/l) . After checking their ability to enter and grow within human enterocyte-like Caco-2 cells, four strains were used to study the intracellular activity and eradicating power of the four quinolones . Trovafloxacin was more active than sparfloxacin and the earlier fluoroquinolones in terms of both intracellular killing and inhibition of a cytopathogenic effect . The uniform high-level activity of trovafloxacin against Listeria monocytogenes isolates in conventional in vitro assays and its extracellular and intracellular killing of invasive strains suggest that this and maybe other new fluoroquinolones should be further investigated as possible anti-listerial agents. Blood, 1998 Feb 1, 91(3), 863 - 9 Essential roles for granulocyte-macrophage colony-stimulating factor (GM-CSF) and G-CSF in the sustained hematopoietic response of Listeria monocytogenes-infected mice; Zhan Y et al.; The in vivo roles of granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte (G)-CSF were studied in factor-deficient gene-targeted knockout mice infected with the facultative intracellular bacterium Listeria monocytogenes . Previous results showed that G-CSF-/- mice had an underlying selective deficiency in granulopoiesis, but GM-CSF-/- mice had little disturbance in resting hematopoiesis . Nevertheless, in this study it is revealed that 3 days after intraperitoneal infection with 2 x 10(5) Listeria, GM-CSF-/- mice harbored 50-fold more organisms in their spleen and liver than similarly infected wild-type mice . This was accompanied by a severe depletion of bone marrow hematopoietic cells and a deficient inflammatory response in their peritoneal cavity . Thus, GM-CSF is essential for emergency, but not resting, hematopoiesis . In contrast, G-CSF-/- mice were markedly susceptible to low doses (2 x 10(4)) of Listeria intraperitoneally . After infection, the acute (1 day) granulocyte infiltration to the peritoneal cavity was normal compared with wild type, but the more prolonged monocyte response was deficient, reflecting a continued decrease in bone marrow cellularity and hematopoiesis over 3 days, which was not observed in infected wild-type mice . It is thus apparent that G-CSF deficiency affects monocytopoiesis as well as granulopoiesis during infection. Microbiol Immunol, 1997, 41(11), 847 - 53 The host response to Listeria monocytogenes mutants defective in genes encoding phospholipases C (plcA, plcB) and actin assembly (actA); Rudnicka W et al.; Several genes involved in the determination of Listeria monocytogenes pathogenesis have been identified . Among them, plcA gene encodes phosphatidylinositol-specific phospholipase C (PI-PLC), plcB gene encodes a broad-range phospholipase C (PC-PLC), and actA encodes a protein contributing to actin assembly in infected cells . The interaction of L . monocytogenes wild type (LO 28) strain and two derivative mutants, plcA- (BUG 206) and actA-/plcB- (LUT 12), with macrophages and T lymphocytes was investigated in a mouse model of listeriosis . Both mutants showed evidence of attenuation . The plcA- mutant, but not the plcB- mutant, expressed an increase in susceptibility to the anti-listerial activity of macrophages . Both mutants showed a decreased ability to induce IL-12 production by bone marrow macrophages when co-stimulated with E . coli LPS or IFN-gamma . In vivo, L . monocytogenes plcA- mutant was found to be a more effective stimulator of T cells than the wild LO 28 strain. Annu Rev Genet, 1997, 31, 113 - 38 Host-pathogen interactions during entry and actin-based movement of Listeria monocytogenes; Ireton K et al.; Listeria monocytogenes is a pathogenic bacterium that induces its own uptake into mammalian cells, and spreads from one cell to another by an actin-based motility process . Entry into host cells involves the bacterial surface proteins InlA (internalin) and InlB . The receptor for InlA is the cell adhesion molecule E-cadherin . InlB-mediated entry requires activation of the host protein phosphoinositide (PI) 3-kinase, probably in response to engagement of a receptor . Actin-based movement of L . monocytogenes is mediated by the bacterial surface protein ActA . The N-terminal region of this protein is necessary and sufficient for polymerization of host cell actin . Other host proteins involved in bacterial motility include profilin, Vasodilator-Stimulated Phosphoprotein (VASP), the Arp2/Arp3 complex, and cofilin . Studies of entry and intracellular movement of L . monocytogenes could lead to a better understanding of receptor-ligand signaling and dynamics of actin polymerization in mammalian cells. Toxicol Appl Pharmacol, 1997 Dec, 147(2), 180 - 9 Interleukin-12 promotes enhanced resistance to Listeria monocytogenes infection of lead-exposed mice; Kishikawa H et al.; The heavy metal lead (Pb) has been shown to downregulate various parameters of cell-mediated immune (CMI) responses . This inhibition of CMI responses by Pb is exemplified by a higher mortality rate upon infections with sublethal doses of a variety of pathogens . Unlike Pb, which lowers host resistance, interleukin-12 (IL-12) exerts a substantial stimulatory influence on the host response to intracellular bacteria such as Listeria monocytogenes . To explore the influence of IL-12 in mice rendered susceptible to Listerial infection by oral exposure to Pb, we determined bacterial burdens and production of interferon gamma (IFN-gamma) . As expected, Pb-exposed mice had increased morbidity due to higher Listerial titers as compared to control mice . However, administration of exogenous IL-12 reversed the Pb-induced inhibition of host defense and boosted the resistance of the non-Pb-treated mice . The enhanced CMI responses observed in both IL-12-treated groups were accompanied with elevations of IFN-gamma in the sera and spleens . Significant reduction in the number of viable Listeria in Pb-exposed mice upon IL-12 administration suggests that the processes downstream of IL-12 production were intact in the Pb-exposed mice and that the inhibition by Pb was due to the lack of functional IL-12 . Alternatively, the exogenous IL-12 may have overcome a downstream effect by enhancing an secondary pathway . Support for the former hypothesis is based on the observation that Pb induced elevated levels of p40 splenic messenger RNA since increased p40 expression would result from lack of IL-12 formation . Contrary to the IFN-gamma levels, significantly higher levels of IL-6 and corticosterone were observed in the sera and spleens of Pb-exposed mice upon infection, suggesting heightened stress in the absence of IL-12 . Overall, the results suggest that an environmental pollutant such as Pb can enhance the stress response, which naturally occurs during an infection, and can further compromise health by lowering host resistance by altering cytokine levels. Poult Sci, 1997 Dec, 76(12), 1661 - 4 Effects of gamma irradiation on the survival of Listeria monocytogenes and on its growth at refrigeration temperature in poultry and red meat; Gursel B et al.; Gamma irradiation sensitivity of a strain of Listeria monocytogenes was determined in trypticase soy broth supplemented with yeast extract (TSB-YE), in a slurry of chicken breast meat and in raw ground beef . D10 values in these different media were 0.364, 0.599, and 0.699 kGy, respectively . This organism appeared most sensitive in TSB-YE, more resistant in minced fresh chicken breast meat, and most resistant in fresh minced beef . It was found that irradiation at 2.5 kGy prior to refrigeration is an efficient way for the preservation of meat products contaminated at 10(3) to 10(4) per gram initial load of L . monocytogenes for about 7 d . However, with this initial load, the injured cells might repair themselves and cause a health hazard during storage at 4 C in the presence of air after 7 d. J Dairy Sci, 1997 Dec, 80(12), 3445 - 8 Mycobacterium paratuberculosis: a potential food-borne pathogen? Collins MT. Mycobacterium paratuberculosis commonly infects dairy cattle, leading to Johne's disease, which is also known as paratuberculosis . The infection is chronic progressive, and incurable . As the infection progresses, excretion of M . paratuberculosis in feces and milk occurs, and the bacterium spreads through the blood to multiple internal organs . Consequently, raw products originating from cattle may harbor M . paratuberculosis . Thermal treatments, such as pasteurization, are commonly relied on to kill food-borne bacterial pathogens that can infect humans . The small number of studies conducted to determine the thermal resistance of M . paratuberculosis suggest that it is less susceptible to destruction by heat killing than are milkborne zoonotic bacterial pathogens such as Listeria spp . or Mycobacterium bovis . Published reports concerning the thermal resistance of M . paratuberculosis in milk are reviewed herein, and key issues concerning the efficacy of pasteurization for elimination of M . paratuberculosis from milk are summarized. Environ Health Perspect, 1998 Feb, 106(2), 71 - 7 Risk assessment for the harmful effects of UVB radiation on the immunological resistance to infectious diseases; Goettsch W et al.; Risk assessment comprises four steps: hazard identification, dose-response assessment, exposure assessment, and risk characterization . In this study, the effects of increased ultraviolet B(UVB, 280-315 nm) radiation on immune functions and the immunological resistance to infectious diseases in rats were analyzed according to this strategy . In a parallelogram approach, nonthreshold mathematical methods were used to estimate the risk for the human population after increased exposure to UVB radiation . These data demonstrate, using a worst-case strategy (sensitive individuals, no adaptation), that exposure for approximately 90 min (local noon) at 40 degrees N in July might lead to 50% suppression of specific T-cell mediated responses to Listeria monocytogenes in humans who were not preexposed to UVB (i.e., not adapted) . Additionally, a 5% decrease in the thickness of the ozone layer might shorten this exposure time by approximately 2.5% . These data demonstrate that UVB radiation, at doses relevant to outdoor exposure, may affect the specific cellular immune response to Listeria bacteria in humans . Whether this will also lead to a lowered resistance (i.e.,increased pathogenic load) in humans is not known, although it was demonstrated that UVB-induced immunosuppression in rats was sufficient to increase the pathogenic load . Epidemiology studies are needed to validate and improve estimates for the potential effects of increased UVB exposure on infectious diseases in humans. Appl Environ Microbiol, 1998 Jan, 64(1), 231 - 7 Nisin resistance in Listeria monocytogenes ATCC 700302 is a complex phenotype; Crandall AD et al.; Nisin resistance in Listeria monocytogenes ATCC 700302 is a complex phenotype involving alterations in both the cytoplasmic membrane and the cell wall and a requirement for divalent cations . In addition to a lower ratio of C15 to C17 fatty acids than in the wild-type strain (A . S . Mazzotta and T.J . Montville, J . Appl . Microbiol . 82: 32-38, 1997), this nisin-resistant (Nisr) strain contained significantly more zwitterionic phosphatidylethanolamine and less anionic phosphatidylglycerol and cardiolipin . The extraction of cardiolipin was enhanced by a penicillin-lysozyme step to disrupt the cell wall . This study is the first to quantify the phosphatidylethanolamine component of the L . monocytogenes cytoplasmic membrane . While these cytoplasmic membrane changes were induced by nisin, the Nisr strain also showed altered sensitivities to cell wall-acting compounds, even when grown in the absence of nisin, suggesting a constitutive alteration in the strain's cell wall . A model which integrates the roles of the cell membrane, cell wall, and divalent cations is presented . Finally, nisin resistance in L . monocytogenes ATCC 700302 conferred cross-resistance to the class IIa bacteriocin pediocin PA-1 and the class IV leuconocin S. Respirology, 1996 Jun, 1(2), 127 - 32 Effect of antibacterial antibody on bactericidal activities of superoxide and lysosomal enzyme from alveolar macrophages in rabbits; Suga M et al.; Alveolar macrophages (AM) have many Fc receptors for IgG, but are less reactive to lymphokines . They have a well-developed oxidative metabolism and contain large amounts of lysosomal enzyme . This suggests that the antibacterial antibody plays an important role in early resistance by AM to intracellular bacterial infection and that a bactericidal agent, dependent on oxygen and lysosomal enzyme, participates in the effects of the antibacterial antibody on bactericidal activities of superoxide (O2-) and lysosomal enzyme from rabbit AM . The number of Listeria monocytogenes in AM increased after pretreatment with saline or normal IgG but decreased by 60% after pretreatment with anti-Listeria and 120 min incubation . Alveolar macrophage-phagocytized Listeria monocytogenes and Bacille Calmette Guerin (BCG) bound with antibacterial antibody enhanced release of O2-, and nitroblue tetrazolium (NBT) formazan reduced by O2- was observed around the bacteria in the phagosomes of AM . We also confirmed that Listeria and BCG were killed extracellularly by O2-released by a superoxide-generating system in vitro and/or by lysosomal concluded that the antibacterial antibody of the IgG class enhances the antibacterial activity of AM thereby increasing the production of 02- and lysosomal enzyme in the phagosome . This finding may be important in the early resistance to intracellular bacteria infection by AM in the alveolar spaces. Arch Latinoam Nutr, 1996 Dec, 46(4), 292 - 4 {Presence of various pathogenic microorganisms in fresh vegetables in Costa Rica}; Monge R et al.; This study reports the occurrence of some pathogenic microorganisms in vegetable consumed on a daily basis by Costa Ricans . Cryptosporidium sp . oocysts were found in 5.2% (4/80) of cilantro leaves, in 8.7% (7/80) of cilantro roots and 2.5% of lettuce samples . A 1.2% (1/80) incidence was found in other vegetables samples (carrot, cucumber, radish and tomatoe) . Oocysts of this parasite were absent in cabbage . Giardia intestinalis was only detected in 5.2% (4/80) of cilantro leaves and in 2.5% (2/ 80) of cilantro roots . Entamoeba histolytica cysts were found in 6.2% (5/80) of cilantro leaves, in 2.5% (2/80) cilantro roots, in 3.8% (3/80) lettuce and in 2.5% (2/80) radish samples . At least a 2% incidence of this amoeba was found in other vegetable samples (carrot, cucumber, cabbage and tomatoe) . Listeria monocytogenes was isolated in 20% (10/50) of the samples of cabbage salad . Hepatitis A virus and Rotavirus were evidenciated in three of the lettuce pooles, suggesting that at least three of the samples were contaminated with these viruses. Rev Argent Microbiol, 1997 Apr-Jun, 29(2), 63 - 7 {Effect of different dairy products on the growth of Listeria monocytogenes in selective media}; Santillan MA et al.; We have studied the influence of the incorporation of milk cream and skim milk on the growth kinetic of Listeria monocytogenes in listeria enrichment broth with 15 mg/l or 7.5 mg/l of acriflavine . Acriflavine was responsible, at least partially, for delayed growth of Listeria monocytogenes in the enrichment broths . A longer lag phase of the growth was produced by the addition of milk cream or skim milk to the enrichment broth containing 7.5 mg/l of acriflavine . However, the maximum population obtained at 48 h did not show significant differences . In the presence of 15 mg/l of acriflavine, we observed a decrease of the viable counts during the early phase of the growth cycle, which was enhanced by the addition of milk cream or skim milk . Moreover, the maximum growth rate was reduced by the addition of skim milk and maximum population was not reached at 48 h . These results suggest the need to validate the methodology of recuperation of Listeria monocytogenes from each dairy product, since its efficiency may be affected by product composition, specially when the sample biocharge is low. Rev Argent Microbiol, 1997 Apr-Jun, 29(2), 109 - 13 {Listeria monocytogenes and Listeria sp in heat-processed products}; Tobia MB et al.; Presence of Listeria monocytogenes in thermoprocessed food which is vacuum packaged, refrigerated stored and eaten uncooked or minimally heated was investigated . Thirty samples including sausage, large sausage with ham, spring large sausage, liverwurst and bologna were examined . Listeria monocytogenes was isolated and identified according to USDA-FSIS method for meat products, simultaneously with McBride agar . Seven out of 30 samples were found to contain listeriae . Five isolates were identified as Listeria monocytogenes through Gram coloration, culture appearance, biochemical test and serotyping . This product results potentially risky for the susceptible population . The presence of this microorganism in this kind of product suggests environmental post-process contamination or insufficient thermal process. Infect Immun, 1998 Jan, 66(1), 232 - 8 Listeria monocytogenes virulence factors that stimulate endothelial cells; Drevets DA; Listeria monocytogenes infection of endothelial cells upregulates surface expression of adhesion molecules and stimulates neutrophil adhesion to infected cell monolayers . The experiments presented here tested the roles of specific bacterial virulence factors as triggers for this inflammatory phenotype and function . Human umbilical vein endothelial cell (HUVEC) monolayers were infected with wild-type L . monocytogenes or L . monocytogenes mutants; then surface expression of E-selectin and neutrophil adhesion were measured . The results showed that delta hly and prfA mutants were the most crippled, requiring 100-fold more mutant bacteria than wild-type bacteria for analogous stimulation . By comparison, L . monocytogenes mutants with deletions of actA, inlA, inlB, inlAB, plcA, and plcB resembled their parent strains, and a delta plcA delta plcB mutant displayed decreased intracellular growth rate but only a minor decrease in stimulation of E-selectin or neutrophil adhesion . Other experiments showed that cytochalasin D-treated HUVEC monolayers bound bacteria, but internalization and increased surface E-selectin and intercellular adhesion molecule-1 expression were profoundly inhibited . However, cytochalasin D had no effect on the HUVEC response to stimulation with lipopolysaccharide or tumor necrosis factor alpha . These data suggest that listeriolysin O production by infecting L . monocytogenes contributes to increased expression of surface E-selectin and intercellular adhesion molecule-1, but neither it nor intracellular replication are directly responsible for this event . Nonetheless it is possible that listeriolysin O potentiates the effect(s) of an other molecule(s) that directly triggers this response . Additionally, cellular invasion by L . monocytogenes appears to be critical for initiating the HUVEC response, potentially by providing a signal which results in upregulation of the necessary bacterial genes. J AOAC Int, 1997 Nov-Dec, 80(6), 1208 - 14 Comparison of antibody-direct epifluorescent filter technique with the most probable number procedure for rapid enumeration of Listeria in fresh vegetables; Tortorello ML et al.; The antibody-direct epifluorescent filter (Ab-DEFT) technique was evaluated as a rapid alternative to the most probable number (MPN) method for enumeration of artificially inoculated Listeria monocytogenes in ready-to-eat packaged salads and other fresh vegetables . Ab-DEFT was performed by homogenization of food in mesh-lined Stomacher bags, followed by prefiltration of homogenate through a 5 microns pore nylon filter, and passage of filtrate through a 0.4 micron pore black polycarbonate filter to collect and concentrate Listeria cells . After cells were stained with a fluorochrome-labeled polyclonal antibody to Listeria, the filter surface was examined by epifluorescence microscopy, and fluorescent cells were counted . A 3-tube MPN procedure was performed by successive enrichments of homogenized foods in Listeria enrichment and Fraser broths, followed by selective plating . Ab-DEFT provided quantitative determinations of Listeria cells that correlated with plate counts and MPN estimates in a linear response over a range of cell concentrations from 10 to 10(7) colony forming units (CFU)/mL . Microbial backgrounds as high as 10(8) CFU/mL did not affect performance of Ab-DEFT . In contrast to the MPN method, which required 5 days to perform, quantitation by Ab-DEFT could be completed in less than 1 h . Despite cross-reactivities demonstrated by the polyclonal fluorescent antibody, the potential of Ab-DEFT as a rapid alternative to MPN for microbial cell enumeration was evident. J Infect Dis, 1998 Jan, 177(1), 155 - 60 Listeriosis outbreak associated with the consumption of rillettes in France in 1993; Goulet V et al.; An outbreak of listeriosis involving 38 patients occurred in France between 18 June and 5 October 1993 . The epidemic clone was characterized by serovar 4b, phagovar 2671:108:312, and DNA macrorestriction patterns 12 and 13 . Thirty-one case-patients were materno-neonatal patients and 7 patients were nonpregnant adults . Preliminary analysis of a case-control study implicated a pork product, rillettes, of a particular brand (odds ratio, 18; 95% confidence interval, 2.2-208) as the vehicle of infection . Rillettes is a ready-to-eat food prepared with ham meat cooked with grease . The implicated lots of rill