Zh Mikrobiol Epidemiol Immunobiol, 2000 Sep-Oct, (5), 3 - 6 {Autoregulation of expression of secreted proteins in Listeria monocytogenes}; Ermolaeva SA et al.; The spectrum of proteins secreted by L . monocytogenes greatly depends on the composition of the cultivation medium . The introduction of activated charcoal (AC) into brain heart infusion (BHI) leads to the secretion of a number of additional proteins with mol.wt . ranging between 20 and 100 kD, whose production is not observed in pure BHI . The effect depends on the absorption capacity of AC: when adsorption capacity is reduced due to a decrease in the concentration of AC or its preliminary saturation with the components of the cultivation medium a drop in the level of the production of additional proteins is observed . The preliminary treatment of the medium with AC with its subsequent elimination prior to inoculation doses not change the spectrum of secreted proteins, though greatly inhibits the growth of L . monocytogenes . The data obtained in this investigation indicate that the effect produced by AC is based on the elimination of some product of L . monocytogenes vital activity from the cultivation medium; this product acts as the autoregulator of the synthesis of a number of secreted proteins. J Virol, 2001 Mar, 75(6), 2786 - 91 Systemic immunity and mucosal immunity are induced against human immunodeficiency virus Gag protein in mice by a new hyperattenuated strain of Listeria monocytogenes; Rayevskaya MV et al.; Vaccines designed to control chronic infections by intracellular agents such as human immunodeficiency virus type 1 (HIV-1) require the induction of cell-mediated immune responses to rid the host of pathogen-infected cells . Listeria monocytogenes has characteristics that make it an attractive vaccine vector for use against such infections . Here we show that parenteral immunization with a new highly attenuated strain of this organism provided complete protection against systemic and mucosal challenges with a recombinant vaccinia virus expressing HIV-1 gag . Immunization also generated a strong, long-term memory cytotoxic-T-lymphocyte (CTL) response in spleen, mesenteric lymph nodes, and Peyer's patches directed against the gag protein . Oral immunization with this attenuated strain also produced complete, long-lasting protection against the recombinant virus but only against mucosal virus challenge . Curiously, oral immunization was associated with a transient CTL response in the three lymphoid tissues examined. Toxicol Appl Pharmacol, 2001 Mar 1, 171(2), 71 - 84 Ozone-induced modulation of cell-mediated immune responses in the lungs; Cohen MD et al.; Most pulmonary immunotoxicology studies of ambient pollutants have been broadly designed to discern if overall humoral or cell-mediated immunity (CMI) was altered; few have assessed effects on particular aspects of immune function . We hypothesized that effects from ozone (O3) exposure on pulmonary CMI are linked in part to changes in local immune cell capacities to form and/or to interact with immunoregulatory cytokines . Rats exposed to 0.1 or 0.3 ppm O3 4 h/day 5 days/week, for 1 or 3 weeks were assessed for resistance to, and pulmonary clearance of, a subsequent Listeria monocytogenes challenge . In situ cytokine release and immune cell profiles were also analyzed at different stages of the antilisterial response . Although O3 exposure modulated CMI, effects were not consistently concentration- or duration-dependent . Exposure did not effect cumulative mortality from infection, but induced concentration-related effects upon morbidity onset and persistence . All 1-week exposed rats had listeric burdens trending higher than controls; 0.3 ppm rats displayed continual burden increases rather than any onset of resolution . Rats exposed for 3 weeks had no O3-related changes in clearance . No exposure-related effect on neutrophil or pulmonary macrophage (PAM) numbers or percentages was noted . Bacterial burden analyses with respect to cell type showed that Listeria:PAM ratios in 0.3 ppm rats ultimately became greatest compared to all other rats . In situ IL-1alpha and TNFalpha levels were consistently higher in O3-exposed rats . All rats displayed increasing in situ IFNgamma levels as infection progressed, but no constant relationship was evident between IFNgamma and initial IL-1alpha/TNFalpha levels in O3-exposed hosts . It seems that short-term (i.e., 1 week) repeated O3 exposures imparted more effects upon CMI than a more prolonged (i.e., 3 week) regimen, with effects manifesting at the level of the PAM and in the cytokine network responsible for immunoactivation . An Med Interna, 2000 Dec, 17(12), 649 - 51 {Listeriosis: an infrequent infection in patients with HIV}; Valencia Ortega ME et al.; Although resistance to Listeria monocytogenes infection requires intact T-cell mediated immunity, listeriosis is an infrequent problem in patients with HIV infection and only about 50 patients have been reported to date . Only two patients with HIV and L . monocytogenes have been attended in our hospital since the beginning of aids epidemic in 1981 . Case 1: a man with HIV and 364 CD4+ cells/mm3 presented fever and occipital headache . The cerebral scan was normal and L . monocytogenes grew in licuor culture . He was outcome after treatment with ampicillin and tobramycin . Case 2: a 47 years old man with HIV, 44 CD4+ cells/mm3 and hepatic virus C cirrhosis was admitted to the hospital because fever and abdominal distension . He was on menstrual pentamidine prophylaxis for Pneumocystis carinii pneumonia (PCP) . Bacterial peritonitis was diagnosed and the patient begun treatment with ceftriaxone . The patient dead 72 hours later with hepatic encepholopathy . Postmortem L . monocytogenes grew . Listeriosis is an infrequent disease in patients with HIV that causes difficult diagnostic problems, principally in patients without prophylaxis with cotrimoxazole for PCP. Int J Food Microbiol, 2001 Jan 22, 63(1-2), 91 - 8 High incidence of Listeria monocytogenes in European red smear cheese; Rudol M et al.; The incidence of Listeria and Listeria monocytogenes in European red smear cheese was determined in order to assess whether the lack of recent outbreaks of listeriosis associated with cheese is due to improved hygenic conditions in the dairies . Out of European red-smear cheese samples of various types, 15.8% contained organisms of the genus Listeria, 6.4% of the samples were contaminated with L . monocytogenes, 10.6% with L . innocua, and 1.2% with L . seeligeri . Six cheese samples contained two or more Listeria species, including at least one L . monocytogenes isolate . The incidences of L . monocytogenes in cheeses from various countries were: Italy 17.4%, Germany 9.2%, Austria 10%, and France 3.3% . Listeria were found most frequently in soft and semi-soft cheese . Eight samples contained more than 100 L . monocytogenes cfu/cm2 cheese surface, 2 samples had counts above 10(4) cfu/cm2 cheese surface . Surprisingly, a higher incidence of L . monocytogenes was observed in cheeses made from pasteurized milk (8.0%) than in cheeses manufactured from raw milk (4.8%) . Phage-typing of isolated Listeria strains clearly confirmed that (i) contaminations within dairy plants were persistent over a period of several weeks to months and (ii) that cross-contamination within the dairy plant is and important factor . Comparison of our data with past surveys seems to indicate that contamination of red smear soft cheese with L . monocytogenes has not decreased sufficiently over the past 15 years . It is therefore strongly recommended that these products are monitored carefully by cheese-making companies. Int J Food Microbiol, 2001 Jan 22, 63(1-2), 135 - 47 Factors influencing resuscitation and growth of heat injured Listeria monocytogenes 13-249 in sous vide cooked beef; Hansen TB et al.; The growth of Listeria monocytogenes 13-249 in vacuum-packed, minced beef was investigated as a function of degree of heat injury (including no injury i.e . uncooked beef), growth phase (logarithmic and late stationary phase), pH (5.6 and 6.2), and storage temperature (3, 10 and 20 degrees C) during a storage period of 30 days . Late logarithmic and late stationary phase cultures of L . monocytogenes 13-249 showed similar growth in refrigerated, vacuum-packed, raw minced beef with a high pH (6.2) . In normal pH (5.6) beef there was no growth at 3 degrees C while growth at 10 and 20 degrees C was only observed for logarithmic phase cultures . Heat injured late stationary phase cultures with 95-99.9% injured cells in the surviving population (as measured by differential plating on enriched vs . selective media after sous vide cooking) did not grow or repair sublethal injuries in sous vide cooked beef at 3 degrees C while repair and growth took place at 10 as well as at 20 degrees C . In logarithmic phase cultures heat injury occurred very rapidly and > or = 99.9% heat injury was observed in all trials in spite of much lower pasteurization values and fewer log10 reductions compared with late stationary phase cultures . Regardless of growth phase, all cultures where a high degree of heat injury (> or = 99.9%) was observed, did not subsequently grow in the beef product at 3 or 10 degrees C within 30 days . Growth of heat injured cultures preexposed to heat shock (46 degrees C, 30 min) or slowly rising temperatures (0.3 degrees C min(-1)) before heat injury was also investigated . Heat shocked or heat adapted cultures generally responded in the same manner as non-stressed cultures (no growth at 3 degrees C) except that a longer lag phase was observed in beef processed at slowly rising temperatures and in normal pH beef at 10 degrees C . Although processing at slowly rising temperatures may slightly increase the survival of L . monocytogenes 13-249 in cooked beef, there seem to be no indication of an increase in subsequent growth potential of the surviving cells. MMWR Morb Mortal Wkly Rep, 2000 Dec 22, 49(50), 1129 - 30 Multistate outbreak of listeriosis--United States, 2000; Listeriolysin O-induced stimulation of mucin exocytosis in polarized intestinal mucin-secreting cells: evidence for toxin recognition of membrane-associated lipids and subsequent toxin internalization through caveolae; Institut National de la Sante et de la Recherche Medicale, Unite 510, Pathogenes et Fonctions des Cellules Epitheliales Polarisees, Faculte de Pharmacie Paris XI, Chatenay-Malabry, FranceLysteriolysin O (LLO) induces a microtubule-dependent activation of mucin exocytosis in the human mucin-secreting HT29-MTX . Cholesterol inhibits the LLO-induced mucin exocytosis, whereas the oxidized form of cholesterol had no inhibitory effect . LLO-induced mucin exocytosis inhibited by cholesterol can be restored by enzymatic treatment with cholesterol oxidase . Inhibition of cholesterol synthesis in HT29-MTX cells results in a decrease in the LLO-induced mucin exocytosis . Other lipids such as gangliosides are able to inhibit the LLO-induced mucin exocytosis, suggesting that the binding of the toxin occurs at a multiplicity of membrane-associated lipids acting as receptors . Incubation of the toxin with lipids such as cholesterol or gangliosides does not decrease binding of LLO to target membranes . The present work also provides evidence that the LLO-induced mucin exocytosis develops independently of the pore-forming activity of the toxin . Finally, we demonstrated that the toxin associates with detergent-insoluble glycolipid microdomains (DIGs) containing VIP/21 caveolin, allowing internalization of the toxin and subsequent activation of the mucin exocytosis. Cell Microbiol, 2000 Dec, 2(6), 465 - 76 The invasion protein InIB from Listeria monocytogenes activates PLC-gamma1 downstream from PI 3-kinase; Bierne H et al.; Entry of the bacterial pathogen Listeria monocytogenes into non-phagocytic mammalian cells is mainly mediated by the InlB protein . Here we show that in the human epithelial cell line HEp-2, the invasion protein InlB activates sequentially a p85beta-p110 class I(A) PI 3-kinase and the phospholipase C-gamma1 (PLC-gamma1) without detectable tyrosine phosphorylation of PLC-gamma1 . Purified InlB stimulates association of PLC-gamma1 with one or more tyrosine-phosphorylated proteins, followed by a transient increase in intracellular inositol 1,4,5-trisphosphate (IP3) levels and a release of intracellular Ca2+ in a PI 3-kinase-dependent manner . Infection of HEp-2 cells with wild-type L . monocytogenes bacteria also induces association of PLC-gamma1 with phosphotyrosyl proteins . This interaction is undetectable upon infection with a deltainlB mutant revealing an InlB specific signal . Interestingly, pharmacological or genetic inactivation of PLC-gamma1 does not significantly affect InlB-mediated bacterial uptake, suggesting that InlB-mediated PLC-gamma1 activation and calcium mobilization are involved in post-internalization steps. Cell Microbiol, 2000 Apr, 2(2), 127 - 36 A novel function of InIB from Listeria monocytogenes: activation of NF-kappaB in J774 macrophages; Mansell A et al.; Listeria monocytogenes causes a pro-inflammatory response on adhesion to macrophages . Upregulation of inflammation genes involves the transcription factor NF-kappaB . Several components of L . monocytogenes, including lipoteichoic acid (LTA), phospholipases and listeriolysin O (LLO), have since been shown to mediate NF-kappaB activation . Here, we report that purified recombinant InlB, but not internalin (InlA), is a potent activator of NF-kappaB in the mouse macrophage-like cell line J774 . Expression of InlB in Listeria innocua enhances its ability to activate NF-kappaB, while deletion of InlB from L . monocytogenes marginally decreases its effect on NF-kappaB, possibly because of the presence of NF-kappaB activators such as LTA and LLO . The effect correlates with the rapid degradation of IkappaBalpha, a sustained degradation of IkappaBbeta and increases in tumour necrosis factor alpha (TNF-alpha) and interleukin (IL) 6 production, two cytokines controlled by NF-kappaB . Using a series of anti-InlB monoclonal antibodies and domains of InlB, NF-kappaB activation was shown to be dependent upon the N-terminal 213-amino-acid leucine-rich repeat (LRR) domain of InlB, recently demonstrated to be responsible for InlB-mediated L . monocytogenes invasion and phosphoinositide-3 (PI-3) kinase activation . The effect of InlB was blocked by PI-3 kinase inhibitors, indicating the involvement of PI-3 kinase in this response . This report thus illustrates that InlB not only promotes invasion, but also contributes to the macrophage pro-inflammatory response. Cell Microbiol, 2000 Apr, 2(2), 101 - 14 LaXp180, a mammalian ActA-binding protein, identified with the yeast two-hybrid system, co-localizes with intracellular Listeria monocytogenes; Pfeuffer T et al.; The Listeria monocytogenes surface protein ActA is an important virulence factor required for listerial intracellular movement by inducing actin polymerization . The only host cell protein known that directly interacts with ActA is the phosphoprotein VASP, which binds to the central proline-rich repeat region of ActA . To identify additional ActA-binding proteins, we applied the yeast two-hybrid system to search for mouse proteins that interact with ActA . A mouse cDNA library was screened for ActA-interacting proteins (AIPs) using ActA from strain L . monocytogenes EGD as bait . Three different AIPs were identified, one of which was identical to the human protein LaXp180 (also called CC1) . Binding of LaXp180 to ActA was also demonstrated in vitro using recombinant histidine-tagged LaXp180 and recombinant ActA . Using an anti-LaXp180 antibody and fluorescence microscopy, we showed that LaXp180 co-localizes with a subset of intracellular, ActA-expressing L . monocytogenes but was never detected on intracellularly growing but ActA-deficient mutants . Furthermore, LaXp180 binding to intracellular L . monocytogenes was asymmetrical and mutually exclusive with F-actin polymerization on the bacterial surface . LaXp180 is a putative binding partner of stathmin, a protein involved in signal transduction pathways and in the regulation of microtubule dynamics . Using immunofluorescence, we showed that stathmin co-localizes with intracellular ActA-expressing L . monocytogenes. Cell Microbiol, 1999 Nov, 1(3), 249 - 57 Stability of the Listeria monocytogenes ActA protein in mammalian cells is regulated by the N-end rule pathway; Moors MA et al.; Upon infection of mammalian cells, Listeria monocytogenes lyses the phagosome and enters the cytosol, where it secretes proteins necessary for its intracellular growth cycle . Consequently, bacterial proteins exposed to the cytosol are potential targets for degradation by host cytosolic proteases . One pathway for degradation of host cytosolic proteins, the N-end rule pathway, involves recognition of the N-terminal amino acid and is mediated by the proteasome . However, very few natural N-end rule substrates have been identified . We have examined the L . monocytogenes ActA protein as a potential target for this pathway . ActA is an essential determinant of L . monocytogenes pathogenesis that is required to induce actin-based motility and cell-to-cell spread . We show that the half-life of a secreted form of ActA can be altered in the mammalian cytosol by changing the N-terminal amino acid . Moreover, the introduction of a destabilizing N-terminus into the functional, surface-bound form of ActA results in a small-plaque phenotype in L2 cells, which is partially reversible by an inhibitor of the proteasome . These results indicate that the L . monocytogenes ActA protein is a natural N-end rule substrate, and that optimal function of ActA in mediating cell-to-cell spread is dependent upon its intracellular turnover rate. J Immunol, 2001 Mar 1, 166(5), 3402 - 9 Organ-specific regulation of the CD8 T cell response to Listeria monocytogenes infection; Pope C et al.; The intestinal mucosal CD8 T cell response to infection with Listeria monocytogenes was measured using MHC class I tetramers and was compared with the response in peripheral blood, secondary lymphoid tissue, and liver . To assess the vaccination potential of Listeria and to analyze responses in C57BL/6 mouse strains, a recombinant Listeria expressing OVA (rLM-ova) was generated . The response peaked at 9 days postinfection with a much larger fraction of the intestinal mucosa and liver CD8 T cell pool OVA specific, as compared with the spleen . However, these differences were not linked to bacterial titers in each site . The higher responses in lamina propria and liver resulted in a larger CD8 memory population in these tissues . Furthermore, the level of memory induced was dependent on infectious dose and inversely correlated with the magnitude of the recall response after oral challenge . Recall responses in the tissues were most robust in the lamina propria and liver, and reactivated Ag-specific T cells produced IFN-gamma . Infection of CD40- or MHC class II-deficient mice induced poor CD8 T cell responses in the intestinal mucosa, but only partially reduced responses in the spleen and liver . Overall, the results point to novel pathways of tissue-specific regulation of primary and memory antimicrobial CD8 T cell responses. Infect Immun, 2001 Mar, 69(3), 1883 - 8 Interference between host resistance to Listeria monocytogenes infection and ovalbumin-induced allergic responses in mice; Mizuki D et al.; Listeria monocytogenes promotes the induction of the T-helper 1 (Th1) cell response, while ovalbumin (OVA) induces a Th2 cell response and allergic reactions, such as airway hyperreactivity and immunoglobulin E (IgE) production . When mice were immunized with OVA on day 7 after L . monocytogenes infection, eosinophilia in bronchoalveolar lavage and the production of total IgE, OVA-specific IgE, interleukin-4 (IL-4), and IL-5 in the circulation were markedly suppressed . Cytokine responses, including IL-4, IL-5, IL-10, IL-13, and gamma interferon, to OVA were decreased in the spleen cell cultures obtained from OVA-immunized mice that had been infected with L . monocytogenes . Conversely, when OVA-immunized mice were infected with L . monocytogenes, conversion from the nonlethal infection to the lethal infection occurred . Host resistance to L . monocytogenes infection in OVA-immunized mice was enhanced by the administration of anti-IL-10 monoclonal antibody . The present study indicates that striking interference is observed between Th1-inducing L . monocytogenes infection and Th2-driven OVA-induced airway hyperreactivity. Infect Immun, 2001 Mar, 69(3), 1795 - 807 Aberrant macrophage and neutrophil population dynamics and impaired Th1 response to Listeria monocytogenes in colony-stimulating factor 1-deficient mice; Guleria I et al.; Listeria monocytogenes, a facultative intracellular bacterium, has been used extensively to study innate immune responses . Macrophages act as hosts for this bacterium as well as a major defense against it . Using mice homozygous for a null mutation (Csf1(op)) in the gene for the mononuclear phagocytic growth factor colony-stimulating factor 1 (CSF-1), we have demonstrated that CSF-1-regulated macrophages were essential to defend against a listerial infection . In the absence of CSF-1, monocytes were not recruited to the sites of infection due to the lack of synthesis of the macrophage chemoattractant chemokine MCP-1 . In addition, there was no burst of interleukin-10 (IL-10) synthesis that has been shown to result in the egress of neutrophils from sites of infection . Consequently, neutrophils were not replaced by macrophages, and numerous neutrophil-filled microabscesses developed, followed by tissue destruction and death of the mice . In the CSF-1 nullizygous mice compared to wild-type mice, there was also a very low synthesis of gamma interferon (IFN-gamma), resulting in reduced macrophage activation . However, the concentrations of the IFN-gamma-inducing cytokines IL-12 and IL-18 at this bacterial load were similar in these mutant mice . In contrast, IL-6 concentrations were dramatically reduced . Administration of IL-6 to Csf1(op)/Csf1(op) mice significantly increased the synthesis of IFN-gamma and reduced the bacterial burden to a greater extent than treatment with IFN-gamma alone . These data indicate that IL-6 occupies a central role in the CSF-1-regulated macrophage response to L . monocytogenes. Infect Immun, 2001 Mar, 69(3), 1708 - 13 Non-major histocompatibility complex control of antibody isotype and Th1 versus Th2 cytokines during experimental infection of mice with Mycobacterium avium; Nagabhushanam V et al.; Infection of different strains of mice with Mycobacterium avium has revealed genetic control of the immunoglobulin isotype induced and of the balance between Th1 and Th2 cytokines . Female BALB/c or C57BL/10 mice were infected intranasally with 10(5) M . avium organisms . The antibody response was measured over 18 weeks by enzyme-linked immunosorbent assay and Western blotting, while numbers of cytokine-producing cells were assessed at 12 to 15 weeks by ELISPOT assay . Upon infection, C57BL/10 mice produced a clear Th1 response with strong gamma interferon (IFN-gamma) production, no interleukin-4 (IL-4), and almost entirely immunoglobulin G2a (IgG2a) antibody . In contrast, BALB/c mice developed T cells producing IL-4, as well as those producing IFN-gamma, while the antibody response was a mixture of IgG1 and IgG2a . Antibodies from BALB/c mice were also able to recognize a greater range of antigens than were C56BL/10 mice . B10D2 mice, which carry the BALB/c major histocompatibility complex haplotype on a C57BL/10 background, followed the C57BL/10 cytokine pattern . Mice infected with Listeria monocytogenes did not show a similar response dichotomy. Infect Immun, 2001 Mar, 69(3), 1344 - 50 Listeria monocytogenes-infected phagocytes can initiate central nervous system infection in mice; Drevets DA et al.; Listeria monocytogenes-infected phagocytes are present in the bloodstream of experimentally infected mice, but whether they play a role in central nervous system (CNS) invasion is unclear . To test whether bacteria within infected leukocytes could establish CNS infection, experimentally infected mice were treated with gentamicin delivered by surgically implanted osmotic pumps . Bacterial inhibitory titers in serum and plasma ranged from 1:16 to 1:256, and essentially all viable bacteria in the bloodstream of treated mice were leukocyte associated . Nevertheless, CNS infection developed in gentamicin-treated animals infected intraperitoneally or by gastric lavage, suggesting that intracellular bacteria could be responsible for neuroinvasion . This was supported by data showing that 43.5% of bacteria found with blood leukocytes were intracellular and some colocalized with F-actin, indicating productive intracellular parasitism . Experiments using an L . monocytogenes strain containing a chromosomal actA-gfpuv-plcB transcriptional fusion showed that blood leukocytes were associated with intracellular and extracellularly bound green fluorescent protein-expressing (GFP+) bacteria . Treatment with gentamicin decreased the numbers of extracellularly bound GFP+ bacteria significantly but did not affect the numbers of intracellular GFP+ bacteria, suggesting that the latter were the result of intercellular spread of GFP+ bacteria to leukocytes . These data demonstrate that infected leukocytes and the intracellular L . monocytogenes harbored within them play key roles in neuroinvasion . Moreover, they suggest that phagocytes recruited to infected organs such as the liver or spleen are themselves parasitized by intercellular spread of L . monocytogenes and then reenter the bloodstream and contribute to the systemic dissemination of bacteria. Trends Microbiol, 2001 Feb, 9(2), 86 - 92 Hijacking and exploitation of IL-10 by intracellular pathogens; Redpath S et al.; Macrophages play a central role in infections, as a target for pathogens and in activation of the immune system . Interleukin-10 (IL-10), a cytokine produced by macrophages, is a potent immunosuppressive factor . Some intracellular pathogens specifically target macrophages for infection and use IL-10 to dampen the host immune response and stall their elimination from the host . Certain viruses induce production of cellular IL-10 by macrophages, whereas other viruses encode their own viral IL-10 homologs . Additionally, specific bacteria, including several Mycobacteria spp . and Listeria monocytogenes, can survive and replicate in macrophages while inducing cellular IL-10, highlighting a potential role for IL-10 of macrophage origin in the immunosuppressive etiology of these pathogens . Thus, the exploitation of IL-10 appears to be a common mechanism of immunosuppression by a diverse group of intracellular pathogens that can infect macrophages. Lett Appl Microbiol, 2001 Feb, 32(2), 78 - 82 A new chromogenic medium for the isolation of Listeria spp; Smith PA et al.; A new medium is described for the isolation of Listeria spp . from foods and environmental samples . It is based on a modified Oxford medium in which 3,4-cyclohexenoesculetin-beta-D-glucoside replaces aesculin . Positive colonies are intensely black with the advantage that the pigment does not diffuse into the medium . The medium, when tested alongside the US Department of Agriculture (spiked samples) and Food and Drug Administration (naturally contaminated samples) isolation procedures, performed significantly better than the current formulations (34% more confirmed positives from naturally contaminated samples) with a reduction of 1 d in the assay time for most samples. Immunology, 2001 Jan, 102(1), 94 - 102 Persistent infection with Listeria monocytogenes in the kidney induces anti-inflammatory invariant fetal-type gammadelta T cells; Ikebe H et al.; After intraperitoneal inoculation with Listeria monocytogenes, gammadelta T cells appear in the peritoneal cavity preceding the appearance of alphabeta T cells . Such gammadelta T cells predominantly express T-cell receptor (TCR)Vgamma1/Vdelta6, develop through an extrathymic pathway, and contribute to host defence against the bacteria . We have observed a gradual increase in gammadelta T cells in kidneys of mice after intrarenal inoculation with L . monocytogenes, which resulted in an unusually long-lasting local infection . In this study, we examined the characteristics and the roles of the gammadelta T cells induced in this model . It was found that these gammadelta T cells predominantly expressed TCRVgamma6/Vdelta1 with canonical junctional sequences identical to those expressed on fetal thymocytes . Although depletion of such gammadelta T cells in vivo did not affect the number of bacteria, it resulted in histologically exacerbated inflammation in the kidneys . These results indicate that a persistent infection with L . monocytogenes in kidneys induces a different kind of gammadelta T cell from that induced after intraperitoneal infection . The former expresses invariant fetal-type Vgamma6/Vdelta1+TCR and plays a regulatory role in resolution of inflammation. Clin Microbiol Infect, 2000 Oct, 6(10), 525 - 35 Natural antibiotic susceptibility of Listeria species: L . grayi, L . innocua, L . ivanovii, L . monocytogenes, L . seeligeri and L . welshimeri strains; Troxler R et al.; OBJECTIVE: To investigate the natural susceptibility to 71 antimicrobial agents of 103 Listeria strains belonging to all known Listeria species (L . monocytogenes (N = 21), L . innocua (N = 21), L . seeligeri (N = 21), L . ivanovii (N = 19), L . welshimeri (N = 11), and L . grayi (N = 10)) . METHODS: MICs were determined using a microdilution procedure in H-Medium . RESULTS: All listeriae were naturally sensitive or intermediate to tetracyclines, aminoglycosides, penicillins (except oxacillin), loracarbef, cefazoline, cefaclor, cefotiam, cefoperazone, carbapenems, macrolides, lincosamides, glycopeptides, dalfopristin/quinupristin, chloramphenicol and rifampicin (probably except L . grayi) . Listeria spp . were naturally resistant or intermediate to most 'modern' cephalosporins (cefetamet, cefixime, ceftibuten, ceftazidime, cefdinir, cefpodoxime, cefotaxime, ceftriaxone, cefuroxime), aztreonam, pipemidic acid, dalfopristin quinupristin and sulfamethoxazole . Significant differences in natural susceptibility among the species were seen with the quinolones, trimethoprim, co-trimoxazole, rifampicin, fosfomycin and fusidic acid . It seems likely that L . grayi is naturally resistant to all antifolates; the species was least susceptible to rifampicin and most susceptible to quinolones, whereas L . ivanovii was naturally resistant to most quinolones . L . ivanovii was naturally sensitive to fosfomycin, whereas L . innocua and L . monocytogenes were naturally resistant . L . ivanovii was also the most susceptible species to fusidic acid . CONCLUSIONS: The present study describes a database on the natural susceptibility of Listeria spp . to a wide range of antibiotics, which can be used to validate susceptibility testing results of these microorganisms. Trends Microbiol, 2001 Jan, 9(1), 23 - 8 From evil to good: a cytolysin in vaccine development; Dietrich G et al.; Current vaccination strategies mainly target antigens into the phagosomal, major histocompatibility complex class II antigen-processing pathway and thus lead predominantly to humoral immune responses . The elicitation of cytotoxic T-cell responses instead requires introduction of antigens into the cytosol of professional antigen-presenting cells (APCs) . The intracellular bacterium Listeria monocytogenes gains access to the host cell cytosol by means of a cytolysin, listeriolysin O . Vaccine researchers have successfully employed listeriolysin in novel vaccination approaches to provide access to the cytosol of professional APCs for purified protein antigens, attenuated bacterial vaccine strains, DNA vaccines and liposome contents. Free Radic Biol Med, 2001 Feb 1, 30(3), 268 - 76 Comparison of control of Listeria by nitric oxide redox chemistry from murine macrophages and NO donors: insights into listeriocidal activity of oxidative and nitrosative stress; Ogawa R et al.; The physiological function of nitric oxide (NO) in the defense against pathogens is multifaceted . The exact chemistry by which NO combats intracellular pathogens such as Listeria monocytogenes is yet unresolved . We examined the effects of NO exposure, either delivered by NO donors or generated in situ within ANA-1 murine macrophages, on L . monocytogenes growth . Production of NO by the two NONOate compounds PAPA/NO (NH2(C3H6)(N{N(O)NO}C3H7) and DEA/NO (Na(C2H5)2N{N(O)NO}) resulted in L . monocytogenes cytostasis with minimal cytotoxicity . Reactive oxygen species generated from xanthine oxidase/hypoxanthine were neither bactericidal nor cytostatic and did not alter the action of NO . L . monocytogenes growth was also suppressed upon internalization into ANA-1 murine macrophages primed with interferon-gamma (INF-gamma) + tumor necrosis factor-alpha (TNF-alpha or INF-gamma + lipid polysaccharide (LPS) . Growth suppression correlated with nitrite formation and nitrosation of 2,3-diaminonaphthalene elicited by stimulated murine macrophages . This nitrosative chemistry was not dependent upon nor mediated by interaction with reactive oxygen species (ROS), but resulted solely from NO and intermediates related to nitrosative stress . The role of nitrosation in controlling L . monocytogenes was further examined by monitoring the effects of exposure to NO on an important virulence factor, Listeriolysin O, which was inhibited under nitrosative conditions . These results suggest that nitrosative stress mediated by macrophages is an important component of the immunological arsenal in controlling L . monocytogenes infections. Vaccine, 2001 Jan 8, 19(11-12), 1435 - 45 Evaluation of a recombinant Listeria monocytogenes expressing an HIV protein that protects mice against viral challenge; Mata M et al.; Vaccine strategies that utilize cell mediated immunity to control infection will be a necessary component of human immunodeficiency virus (HIV) vaccines . In previous studies we have shown that a Listeria monocytogenes recombinant expressing HIV-Gag elicits strong CD8+ and CD4+ T cell responses against HIV Gag in addition to its own secreted proteins . Here, we show that Lm-Gag can protect mice against a viral challenge with a recombinant vaccinia virus expressing Gag, in an antigen specific manner, and that this protection is T cell mediated . These results further support the use of L . monocytogenes as a vaccine approach for HIV through the induction of T cell immunity. Curr Opin Cell Biol, 2001 Feb, 13(1), 85 - 91 Actin filament nucleation by endosomes, lysosomes and secretory vesicles; Taunton J; Intracellular pathogens such as Listeria monocytogenes and vaccinia virus propel themselves through the cytoplasm of mammalian cells by nucleating actin filaments . Recently, actin assembly has also been shown to power the movement of intracellular vesicles, and this may be a mechanism underlying endomembrane movement in a variety of physiological contexts . Surprisingly, class I myosins have been found to play important roles in both actin nucleation and endomembrane trafficking. Cell Immunol, 2001 Jan 10, 207(1), 13 - 8 Relationships between IFNgamma, IL-6, corticosterone, and Listeria monocytogenes pathogenesis in BALB/c mice; Kim D et al.; The relationships between Listeria monocytogenes (LM) pathogenesis, based on bacterial load, and serum levels of IL-6, IFNgamma, and corticosterone (CORT) were quantified . Serum IFNgamma levels increased along with the LM burden; however, with LM burdens > or =3 x 10(6) CFU per spleen, the serum IFNgamma level decreased along with a decrease in splenic weight . Serum IL-6 levels exponentially increased with increases of LM, and the CORT level positively correlated with the increase in IL-6 and LM . The serum level of IFNgamma appeared to be a good biomarker of the host's ability to combat the infection only when the LM burden did not exceed a critical level (>3 x 10(6) CFU per spleen) . Interestingly, the LM load at which the IFNgamma level began to decline was near the dose at which the IL-6 concentration exponentially increased, suggesting a transition point shift from stress (assessed as CORT level) being immunoenhancing to becoming immunosuppressive . The IL-6:IFNgamma ratio may be a good indicator of disease severity and/or the ability to cope with an infection . J Immunol, 2001 Feb 15, 166(4), 2651 - 7 Lipopolysaccharide-induced IL-18 secretion from murine Kupffer cells independently of myeloid differentiation factor 88 that is critically involved in induction of production of IL-12 and IL-1beta; Seki E et al.; IL-18, produced as biologically inactive precursor, is secreted from LPS-stimulated macrophages after cleavage by caspase-1 . In this study, we investigated the mechanism underlying caspase-1-mediated IL-18 secretion . Kupffer cells constantly stored IL-18 and constitutively expressed caspase-1 . Inhibition of new protein synthesis only slightly reduced IL-18 secretion, while it decreased and abrogated their IL-1beta and IL-12 secretion, respectively . Kupffer cells deficient in Toll-like receptor (TLR) 4, an LPS-signaling receptor, did not secrete IL-18, IL-1beta, and IL-12 upon LPS stimulation . In contrast, Kupffer cells lacking myeloid differentiation factor 88 (MyD88), an adaptor molecule for TLR-mediated-signaling, secreted IL-18 without IL-1beta and IL-12 production in a caspase-1-dependent and de novo synthesis-independent manner . These results indicate that MyD88 is essential for IL-12 and IL-1beta production from Kupffer cells while their IL-18 secretion is mediated via activation of endogenous caspase-1 without de novo protein synthesis in a MyD88-independent fashion after stimulation with LPS . In addition, infection with Listeria monocytogenes, products of which have the capacity to activate TLR, increased serum levels of IL-18 in wild-type and MyD88-deficient mice but not in caspase-1-deficient mice, whereas it induced elevation of serum levels of IL-12 in both wild-type and caspase-1-deficient mice but not in MyD88-deficient mice . Taken together, these results suggested caspase-1-dependent, MyD88-independent IL-18 release in bacterial infection. J Immunol, 2001 Feb 15, 166(4), 2348 - 56 Direct analysis of the dynamics of the intestinal mucosa CD8 T cell response to systemic virus infection; Masopust D et al.; The CD8 T cell response to vesicular stomatitis virus infection was characterized in the spleen and intestinal mucosa using MHC tetramers . Surprisingly, the primary response persisted in the lamina propria long after the splenic response had declined . Furthermore, the response was characterized by a protracted effector phase in which cytolytic activity in the lamina propria, but not in the spleen, was maintained . The appearance of Ag-specific cells in the intestinal mucosa was largely, though not exclusively, a result of beta(7) integrin-mediated migration . Infection with Listeria monocytogenes or with vaccinia virus also led to sustained mucosal responses . After reinfection of vesicular stomatitis virus-primed mice with a serotypically distinct virus, a sustained recall response was detected in all tissues . In CD40(-/-) mice, the mucosal, but not the splenic, response was compromised, resulting in diminished mucosal memory . The recall response was CD40 independent and correlated with memory levels, indicating that the mucosal and systemic responses operated independently . These findings illustrated the integrated yet distinct nature of systemic vs mucosal immune responses. J Immunol, 2001 Feb 1, 166(3), 1877 - 84 A novel approach of direct ex vivo epitope mapping identifies dominant and subdominant CD4 and CD8 T cell epitopes from Listeria monocytogenes; Geginat G et al.; We used a novel approach for the direct ex vivo identification and characterization of T cell epitopes based on the screening of peptide spot libraries with freshly isolated splenocytes in a sensitive enzyme-linked immunospot (ELISPOT) assay . This technique was applied for the analysis of splenocytes from Listeria monocytogenes-infected BALB/c and C57BL/6 mice . The screening of peptide spot libraries covering the whole listeriolysin O and p60 of L . monocytogenes confirmed all known CD4 and CD8 T cell epitopes of these proteins and additionally revealed six new H-2(d) and six new H-2(b)-restricted T cell epitopes . New epitopes were categorized into CD4 and CD8 T cell epitopes by ex vivo ELISPOT analysis with separated T cell populations . The quantitative analysis of cells reactive with these CD4 and CD8 T cell epitopes revealed the existence of dominant and subdominant CD4 and CD8 T cell populations during L . monocytogenes infection . As a consequence of these data we suggest that ELISPOT-based screening of peptide spot libraries could be a general approach for the rapid identification and characterization of pathogen-specific T cell populations during various infectious diseases. Infect Immun, 2001 Feb, 69(2), 1093 - 100 Neural route of cerebral Listeria monocytogenes murine infection: role of immune response mechanisms in controlling bacterial neuroinvasion; Jin Y et al.; The pathologic features of cerebral Listeria monocytogenes infection strongly suggest that besides hematogenous spread, bacteria might also spread via a neural route . We propose that after snout infection of recombination activating gene 1 (RAG-1)-deficient mice, L . monocytogenes spreads to the brain via a neural route . The neural route of invasion is suggested by (i) the immunostaining of L . monocytogenes in the trigeminal ganglia (TG) and brain stem but not in other areas of the brain; (ii) the kinetics of bacterial loads in snout, TG, and brain; and (iii) the increased resistance of mice infected with a plcB bacterial mutant (unable to spread from cell to cell) . Gamma interferon (IFN-gamma) plays a protective role in neuroinvasion; inducible nitric oxide synthase (iNOS) accounts only partially for the protection, as shown by a comparison of the susceptibilities of IFN-gamma receptor (IFN-gamma R)-deficient, iNOS-deficient, and wild-type mice to snout infection with L . monocytogenes . The dramatically enhanced susceptibility of RAG-1-deficient, IFN-gamma R gene-deficient mice indicated the overall importance of innate immune cells in the release of protective levels of IFN-gamma . The source of IFN-gamma appeared to be NK cells, as shown by use of RAG-1-deficient, gamma-chain receptor gene-deficient mice; NK cells played a relevant protective role in neuroinvasion through a perforin-independent mechanism . In vitro evidence indicated that IFN-gamma can directly induce bacteriostatic mechanisms in neural tissue. Infect Immun, 2001 Feb, 69(2), 897 - 905 Human endothelial cell activation and mediator release in response to Listeria monocytogenes virulence factors; Rose F et al.; The interaction of Listeria monocytogenes with endothelial cells represents a crucial step in the pathogenesis of listeriosis . Incubation of human umbilical vein endothelial cells (HUVEC) with wild-type L . monocytogenes (EGD) provoked immediate strong NO synthesis, attributable to listerial presentation of listeriolysin O (LLO), as the NO release was missed upon employment of a deletion mutant for LLO (EGD hly mutant) and was reproduced by purified LLO . Studies of conditions lacking extracellular Ca(2+) suggested LLO-elicited Ca(2+) flux as the underlying mechanism . In addition, HUVEC incubation with EGD turned out to be a potent stimulus for sustained (>12-h) upregulation of proinflammatory cytokine generation (interleukin 6 {IL-6}, IL-8, and granulocyte-macrophage colony-stimulating factor) . Use of deletion mutants for LLO (EGD hly mutant), listerial phosphatidylinositol-specific phospholipase C (EGD plcA mutant), broad-spectrum phospholipase C (EGD plcB mutant) and internalin B (EGD inlB mutant), as well as purified LLO, identified LLO as largely responsible for the cytokine response . Endothelial cells responded with diacylglycerole and ceramide generation as well as nuclear translocation of NF-kappa B to the stimulation with the LLO-producing strains EGD and Listeria innocua . The endothelial PC-phospholipase C inhibitor tricyclodecan-9-yl-xanthogenate as well as two independent inhibitors of NF-kappa B activation, pyrolidine dithiocarbamate and caffeic acid phenethyl ester, suppressed both the NF-kappa B translocation and the upregulation of cytokine synthesis . We conclude that L . monocytogenes is a potent stimulus of NO release and sustained upregulation of proinflammatory cytokine synthesis in human endothelial cells, both events being largely attributable to LLO presentation . LLO-induced transmembrane Ca(2+) flux as well as a sequence of endothelial phospholipase activation and the appearance of diacylglycerole, ceramide, and NF-kappa B are suggested as underlying host signaling events . These endothelial responses to L . monocytogenes may well contribute to the pathogenic sequelae in severe listerial infection and sepsis. J Clin Microbiol, 2001 Feb, 39(2), 485 - 93 Purification and characterization of PCR-inhibitory components in blood cells; Al-Soud WA et al.; In a recent study, immunoglobulin G in human plasma was identified as a major inhibitor of diagnostic PCR (W . Abu Al-Soud, L . J . Jonsson, and P . Radstrom . J . Clin . Microbiol . 38:345-350, 2000) . In this study, two major PCR inhibitors in human blood cells were purified using size exclusion and anion-exchange chromatographic procedures . Based on N-terminal amino acid sequencing and electrophoretic analysis of the purified polypeptides, hemoglobin and lactoferrin were identified as PCR-inhibitor components in erythrocytes and leukocytes, respectively . When different concentrations of hemoglobin or lactoferrin were added to PCR mixtures of 25 microl containing 10 different thermostable DNA polymerases and 1 ng of Listeria monocytogenes DNA as template DNA, AmpliTaq Gold, Pwo, and Ultma were inhibited in the presence of < or = 1.3 microg of hemoglobin and < or = 25 ng of lactoferrin, while rTth and Tli were found to resist inhibition of at least 100 microg of hemoglobin . In addition, the quantitative effects of seven low-molecular-mass inhibitors, present in blood samples or degradation products of hemoglobin, on real-time DNA synthesis of rTth using the LightCycler Instrument were investigated . A reaction system based on a single-stranded poly(dA) template with an oligo(dT) primer annealed to the 3' end was used . It was found that the addition of 0.25 to 0.1 mg of bile per ml, 2.5 mM CaCl2, 0.25 mM EDTA, 5 microM FeCl3, and 0.01 IU of heparin per ml reduced the fluorescence to approximately 76, 70, 46, 17, and 51%, respectively . Finally, the effects of nine amplification facilitators were studied in the presence of hemoglobin and lactoferrin . Bovine serum albumin (BSA) was the most efficient amplification facilitator, so that the addition of 0.4% (wt/vol) BSA allowed AmpliTaq Gold to amplify DNA in the presence of 20 instead of 1 microg of hemoglobin and 500 instead of 5 ng of lactoferrin . Including 0.02% (wt/vol) gp32, a single-stranded-DNA binding protein, in the reaction mixture of AmpliTaq Gold was also found to reduce the inhibitory effects of hemoglobin and lactoferrin. J Bacteriol, 2001 Feb, 183(4), 1133 - 9 A novel serotype-specific gene cassette (gltA-gltB) is required for expression of teichoic acid-associated surface antigens in Listeria monocytogenes of serotype 4b; Lei XH et al.; Listeria monocytogenes serotype 4b strains account for about 40% of sporadic cases and many epidemics of listeriosis . Mutations in a chromosomal locus resulted in loss of reactivity with all three monoclonal antibodies (MAbs) which were specific to serotype 4b and the closely related serotypes 4d and 4e . Here we show that this locus contains a serotype 4b-4d-4e-specific gene cassette (3,071 bp) which consists of two genes, gltA and gltB, and is flanked by palindromic sequences (51 and 44 nucleotides) . Complete loss of reactivity with the three serotype-specific MAbs resulted from insertional inactivation of either gltA or gltB . The gltA and gltB mutants were characterized by loss and severe reduction, respectively, of glucose in the teichoic acid, whereas galactose, the other serotype-specific sugar substituent in the teichoic acid, was not affected . Within L . monocytogenes, only strains of serotypes 4b, 4d, and 4e harbored the gltA-gltB cassette, whereas coding sequences on either side of the cassette were conserved among all serotypes . Comparative genomic analysis of a serotype 1/2b strain showed that the 3,071-bp gltA-gltB cassette was replaced by a much shorter (528-bp) and unrelated region, flanked by inverted repeats similar to their counterparts in serotype 4b . These findings indicate that in the evolution of different serotypes of L . monocytogenes, this site in the genome has become occupied by serotype-specific sequences which, in the case of serotype 4b, are essential for expression of serotype-specific surface antigens and presence of glucose substituents in the teichoic acids in the cell wall. Appl Environ Microbiol, 2001 Feb, 67(2), 840 - 7 Characterization of recurrent and sporadic Listeria monocytogenes isolates from raw milk and nondairy foods by pulsed-field gel electrophoresis, monocin typing, plasmid profiling, and cadmium and antibiotic resistance determination; Harvey J et al.; Following previous surveys to assess the incidence of Listeria monocytogenes in raw milk and nondairy foods processed in Northern Ireland, isolates were characterized as recurrent or sporadic on the basis of multilocus enzyme electrophoresis (MEE) analysis and restriction fragment length polymorphism typing . In the present study, 45 representative recurrent and sporadic electrophoretic types (ETs) previously identified by MEE were subjected to pulsed-field gel electrophoresis (PFGE) of genomic DNA macrorestriction fragments, monocin typing, plasmid profiling, and an examination of resistance to cadmium and nine different antibiotics . Although PFGE proved to be capable of subdividing a number of recurrent and sporadic ETs, the grouping of strains arrived at by PFGE and MEE were in broad agreement, and previous conclusions regarding the designation of L . monocytogenes strains as recurrent or sporadic remained unaltered . It is considered that PFGE was able to detect minor genetic changes in recurrent ETs which occurred during the time period in which food surveys were carried out . Production of type E monocin (Types A to E were found among the 45 strains), plasmid carriage, and resistance to cadmium occurred more frequently in recurrent than in sporadic strains and may be important with regard to the ability of L . monocytogenes to persist in food and food-processing environments . Only 2 of 45 strains showed resistance to any of the nine antibiotics tested: two sporadic strains were resistant to tetracycline (MIC, 64 microg x ml(-1)). Appl Environ Microbiol, 2001 Feb, 67(2), 646 - 53 Characterization and pathogenic potential of Listeria monocytogenes isolates from the smoked fish industry; Norton DM et al.; This study was designed to evaluate the hypothesis that some of the Listeria monocytogenes subtypes associated with foods, specifically smoked fish, may have an attenuated ability to cause human disease . We tested this hypothesis by using two different approaches: (i) comparison of molecular subtypes found among 117 isolates from smoked fish, raw materials, fish in process, and processing environments with subtypes found among a collection of 275 human clinical isolates and (ii) the evaluation of the cytopathogenicity of industrial isolates . Ribotyping and PCR-restriction fragment length polymorphism typing of the hlyA and actA genes differentiated 23 subtypes among the industrial isolates and allowed classification of the isolates into three genetic lineages . A significantly higher proportion of human isolates (69.1%) than industrial isolates (36.8%) were classified as lineage I, which contains human sporadic isolates and all epidemic isolates . All other industrial isolates (63.2%) were classified as lineage II, which contains only human sporadic isolates . Lineage I ribotypes DUP-1038B and DUP-1042B represented a significantly higher proportion of the human isolates than industrial isolates (5.1%) . Lineage II ribotypes DUP-1039C, DUP-1042C, and DUP-1045, shown previously to persist in the smoked fish processing environment, represented nearly 50% of the industrial isolates, compared to 7.6% of the human isolates . Representatives of each subtype were evaluated with a tissue culture plaque assay . Lineage I isolates formed plaques that were significantly larger than those formed by lineage II isolates . Isolates from the smoked fish industry representing three ribotypes formed no plaques or small plaques, indicating that they had an impaired ability to infect mammalian cells . While L . monocytogenes clonal groups linked to human listeriosis cases and outbreaks were isolated, our data also suggest that at least some L . monocytogenes subtypes present in ready-to-eat foods may have limited human-pathogenic potential. J Immunol, 2000 Apr 15, 164(8), 4063 - 70 Differing roles of inflammation and antigen in T cell proliferation and memory generation; Busch DH et al.; Recent studies have demonstrated that viral and bacterial infections can induce dramatic in vivo expansion of Ag-specific T lymphocytes . Although presentation of Ag is critical for activation of naive T cells, it is less clear how dependent subsequent in vivo T cell proliferation and memory generation are upon Ag . We investigated T cell expansion and memory generation in mice infected alternately with strains of Listeria monocytogenes that contained or lacked an immunodominant, MHC class I-restricted T cell epitope . We found substantial differences in the responses of effector and memory T cells to inflammatory stimuli . Although effector T cells undergo in vivo expansion in response to bacterial infection in the absence of Ag, memory T cells show no evidence for such bystander activation . However, Ag-independent expansion of effector T cells does not result in increased memory T cell frequencies, indicating that Ag presentation is critical for effective memory T cell generation . Early reinfection of mice with L . monocytogenes before the maximal primary T cell response induces typical memory expansion, suggesting that the capacity for a memory T cell response exists within the primary effector population . Our findings demonstrate that T cell effector proliferation and memory generation are temporally overlapping processes with differing requirements for Ag. J Biol Chem, 2000 Apr 14, 275(15), 11181 - 90 Monitoring cellular responses to Listeria monocytogenes with oligonucleotide arrays; Cohen P et al.; Listeria monocytogenes is a pathogenic intracellular microorganism whose infection induces pleiotropic biological changes associated with host cell gene expression regulation . Here we define the gene expression profiles of the human promyelocytic THP1 cell line before and after L . monocytogenes infection . Gene expression was measured on a large scale via oligonucleotide microarrays with probe sets corresponding to 6,800 human genes . We assessed and discussed the reproducibility of the hybridization signatures . In addition to oligonucleotide arrays, we also performed the large scale gene expression measurement with two high-density membranes, assaying for 588 and 18,376 human genes, respectively . This work allowed the reproducible identification of 74 up-regulated RNAs and 23 down-regulated RNAs as a consequence of L . monocytogenes infection of THP1 . The reliability of these data was reinforced by performing independent infections . Some of these detected RNAs were consistent with previous results, while some newly identified RNAs encode gene products that may play key roles in L . monocytogenes infection . These findings will undoubtedly enhance the understanding of L . monocytogenes molecular physiology and may help identify new therapeutic targets. Int J Food Microbiol, 2000 Dec 20, 62(3), 267 - 74 Control options for Listeria monocytogenes in seafoods; Huss HH et al.; At least three outbreaks of listeriosis associated with seafood have been reported . Listeria monocytogenes is widely distributed in the general environment including fresh water, coastal water and live fish from these areas . Contamination or recontamination of seafood may also take place during processing and low levels (< 100 cfu/g) of L . monocytogenes are frequently found on seafood including ready-to-eat (RTE) products . Apart from heat treatment, which is very effective, there are few options for eliminating L . monocytogenes from foods and equipment . It is essential therefore, that growth of L . monocytogenes in the final product be inhibited . The preventive measures include the formulation of a cleaning and sanitising program specifically designed at reducing the presence of L . monocytogenes in the factory environment, the safe elimination of L . monocytogenes from heat treated products and prevention of growth in RTE products within the normal shelf life and conditions stated on the label . If any sampling is required, the sampling plans suggested by the International Commission on Microbiological Specifications for Foods {Int . J . Food Microbiol., 22 (1994) 89-96} are useful. Int J Food Microbiol, 2000 Dec 20, 62(3), 253 - 60 Risk assessment used to evaluate the US position on Listeria monocytogenes in seafood; Elliot EL et al.; Human listeriosis has been associated with consumption of food including seafood . Surveillance information on the presence of Listeria monocytogenes in seafood products is presented as a background for steps that are being taken to inform risk managers of risks associated with particular food products . United States policy for L . monocytogenes in food has been shaped by our increasing knowledge of the epidemiology of outbreaks and sporadic cases of human listeriosis, the potentially severe public health consequences, and the characteristics of the organism . A quantitative risk assessment of the scientific knowledge we have about the organism and the epidemiology of listeriosis should be the basis for changes in this policy . Risk assessment uses quantitative scientific and epidemiological information in a structured format to determine the risks associated with particular hazards . A quantitative risk assessment is being performed using currently available data by the US Food and Drug Administration, in collaboration with the US Food Safety and Inspection Service, to determine the risk of listeriosis from various foods, including seafood, for specific intervention methods, and for general and at-risk population groups . The questions being considered include those on level of consumption, epidemiology, dose response, and the virulence, biology, and ecology of the organism . Risk managers can use the resulting information to form a defendable science-based policy on L . monocytogenes in food. Int J Food Microbiol, 2000 Dec 20, 62(3), 247 - 51 Present situation in Canada regarding Listeria monocytogenes and ready-to-eat seafood products; Farber JM; The present situation regarding Listeria monocytogenes and ready-to-eat (RTE) seafood is discussed . An updated regulatory policy on L . monocytogenes directs inspection and compliance action to those RTE foods capable of supporting growth of the organism and is based on a combination of inspection, environmental sampling and product testing . The incidence of L . monocytogenes in imported seafood products in 1996-1997 and 1997-1998 was 0.88 and 0.3%, respectively . With respect to domestic products, an analysis of 347 RTE foods in 1997-1998 and 1998-1999, at one of the large fish inspection labs in the Maritimes, revealed an absence of L . monocytogenes . The only seafood product linked to suspect cases of listeriosis in Canada was imported. Int J Food Microbiol, 2000 Dec 20, 62(3), 231 - 45 Predictive modelling of the growth and survival of Listeria in fishery products; Ross T et al.; Predictive microbiology provides a powerful tool to aid the exposure assessment phase of 'quantitative microbial risk assessment' . Using predictive models changes in microbial populations on foods between the point of production/harvest and the point of eating can be estimated from changes in product parameters (temperature, storage atmosphere, pH, salt/water activity, etc.) . Thus, it is possible to infer exposure to Listeria monocytogenes at the time of consumption from the initial microbiological condition of the food and its history from production to consumption . Predictive microbiology models have immediate practical application to improve microbial food safety and quality, and are leading to development of a quantitative understanding of the microbial ecology of foods . While models are very useful decision-support tools it must be remembered that models are, at best, only a simplified representation of reality . As such, application of model predictions should be tempered by previous experience, and used with cognisance of other microbial ecology principles that may not be included in the model . Nonetheless, it is concluded that predictive models, successfully validated in agreement with defined performance criteria, will be an essential element of exposure assessment within formal quantitative risk assessment . Sources of data and models relevant to assessment of the human health risk of L . monocytogenes in seafoods are identified . Limitations of the current generation of predictive microbiology models are also discussed . These limitations, and their consequences, must be recognised and overtly considered so that the risk assessment process remains transparent . Furthermore, there is a need to characterise and incorporate into models the extent of variability in microbial responses . The integration of models for microbial growth, growth limits or inactivation into models that can predict both increases and decreases in microbial populations over time will also improve the utility of predictive models for exposure assessment . All of these issues are the subject of ongoing research. Int J Food Microbiol, 2000 Dec 20, 62(3), 223 - 9 Risk assessment of Listeria monocytogenes in fish products: some general principles, mechanism of infection and the use of performance standards to control human exposure; Notermans S et al.; Risk assessment is increasingly used as a scientific process to assess the potential for adverse health effects to occur and as a basis for management of unacceptable risks . For each risk assessment activity, the purpose of the assessment should be clearly stated . For Listeria monocytogenes, the purpose of risk assessment may be providing information on the relative contribution of listeriosis to infectious diseases . For control purposes, the emphasis may be put on factors contributing to the risk of occurrence in a food or to inform risk managers that they should be setting food safety objectives . For an adequate risk assessment of L . monocytogenes, sound scientific data are necessary . This especially applies both to exposure assessment and hazard characterisation . Surveillance data indicates that cold storage to prolongs product shelf-life has opened an ecological window for the growth of L . monocytogenes . Assessment of dose-response relationship is often regarded as a key element in risk characterisation . Due to the large variability of the current assessed dose-response data, their contribution to assessing risks is low . The use of epidemiological data on incidence rate, types of food involved in listeriosis, etc . may be good alternatives . The use of performance standards or criteria, such as inactivation by heat or by fermentation, combined with processes that prevent outgrowth of the organism should be reconsidered . Presently, performance standards can simply be assessed since mathematical tools for their calculations are becoming increasingly available. Int J Food Microbiol, 2000 Dec 20, 62(3), 217 - 21 Microbiological criteria for Listeria monocytogenes in foods under special consideration of risk assessment approaches; Norrung B; This paper shortly summarizes data related to risk assessment of Listeria monocytogenes . From available data on risk assessment, it is concluded that the levels of L . monocytogenes consumed is an important factor affecting the incidence of listeriosis . Foods that do not support the growth of L . monocytogenes are unlikely to be a source of listeriosis, whereas foods that support the growth to high levels, should be the target of risk management efforts . Based on current epidemiological information from several countries, a concentration of L . monocytogenes not exceeding 100/g of food at the time of consumption is of low risk to the consumers . In order not to exceed these levels at the point of consumption, lower levels may need to be applied at the port of entry, for those foods in which growth can occur within the shelf life . In order to establish such levels, knowledge of the shelf life and behaviour of L . monocytogenes in the food during prevailing storage and distribution conditions is needed. Int J Food Microbiol, 2000 Dec 20, 62(3), 211 - 5 Potential of Listeria hazard in African fishery products and possible control measures; Ababouch L; Africa contributes 5.54 million MT (4.5%) to the world harvest of aquatic organisms . Fisheries represent a vital sector for many countries in Africa, both for domestic food supply, employment opportunities and foreign exchange earnings . Despite the low level of African fish production and export in comparison with the other continents, fish represent the major protein Source in many countries (36-58% of animal proteins in C te d'Ivoire, Congo, Senegal, Angola) and fishing is a vital activity for Senegal, Mauritania, Morocco, Ghana, Tunisia and other countries . In fact, it is the main sector for foreign exchange earnings in countries such as Senegal and Mauritania (Ababouch, 1998b; 1999) . Consequently, expansion of export and development and production of value-added products in Africa for export are strategic keys for future economic development . This will require the implementation of reliable in-plant HACCP-based quality and safety control systems . Unfortunately, very little in known about the prevalence and ecology of Listeria in food, especially as it relates to seafood safety . This paper discusses the potential of Listeria hazard from African fishery products and speculates on some possible control measures. Int J Food Microbiol, 2000 Dec 20, 62(3), 197 - 209 Epidemiology of human listeriosis and seafoods; Rocourt J et al.; While rarely diagnosed prior to 1960, more than 10,000 cases of listeriosis were recorded in the medical literature between 1960 and 1982, and thousands more have been reported annually world-wide {Rocourt J., 1991 . Human listeriosis, 1989 . WHO/HPP/FOS/91.3, World Health Organization, Geneva, Switzerland; Rocourt, J., Brosch, R., 1992 . Human listeriosis, 1990 . WHO/HPP/FOS/92.3, World Health Organization, Geneva, Switzerland; Rocourt, J., Jacquet, Ch., Bille, J., 1997 . Human listeriosis, 1991/1992 . WHO/FNU/FOS/97.1, World Health Organization, Geneva, Switzerland} . This widespread increase in reporting is most likely due to demographic trends and changes in food production, processing and storage, especially the extended cold food chain and the ability of Listeria monocytogenes to grow at low temperatures: L . monocytogenes is a bacterium responsible for opportunistic infections, preferentially affecting individuals whose immune system is perturbed, including pregnant women, newborns, people over 65 years, immunocompromised patients, such as cancer victims, transplant recipients, people on hemodialysis and AIDS patients . Thus, the increasing lifespan and medical progress allowing immunodeficient individuals to survive, partially explains the increasing incidence of listeriosis . Moreover, L . monocytogenes is ubiquitous and can grow at temperatures as low as 0 degrees C . At this temperature growth is very slow . The expansion of the agro-food industry, the widespread use of systems of cold storage and changes in consumers demands have led to a large increase in the pool of Listeria that can cause foodborne infections. Int J Food Microbiol, 2000 Dec 20, 62(3), 191 - 6 Incidence and significance of Listeria in fish and fish products from Latin America; Destro MT; The incidence and importance of Listeria spp . in fish and fishery products in Latin American countries is reviewed . There are very few papers dealing with this subject, however it is known that Listeria can be an important problem even for fisheries of tropical countries . The importance of GMP and HACCP implementation is also discussed. Int J Food Microbiol, 2000 Dec 20, 62(3), 183 - 90 Listeria monocytogenes in the smoked salmon industry; Rorvik LM; Smoked salmon is sporadically contaminated with Listerial monocytogenes . Contamination levels are normally low and consumers are probably seldom exposed to risk concentrations . No clones of L . monocytogenes seem to be specific to smoked salmon, some clones found in smoked salmon having been isolated from several sources, including patients . Cold-smoking has been shown to eliminate L . monocytogenes in challenge tests at temperatures from 17.1 to 21.1 degrees C, while from 22.2 to 30 degrees C the bacteria survived . Under natural cold-smoking conditions (19 to 22 degrees C) the frequency and level of L . monocytogenes seems to decrease . Hot-smoking seems to eliminate the bacteria when smoke is applied during the whole heating process . The prevention of recontamination of both cold-smoked and hot-smoked salmon is therefore of great importance . L . monocytogenes multiply considerably in smoked salmon during storage . Growth is faster in challenge tests than in naturally-contaminated smoked salmon . The declared shelf-life under refrigeration should be shorter than that customarily stipulated by many producers . While the sources of L . monocytogenes in smoked salmon processing plants have still to be determined, raw salmon does not seem to be an important source . The main issue for producers is to prevent colonization of the processing environment and spread of the bacteria to products . This should be achieved by the systemic implementation of hygienic measures, including the HACCP approach. Int J Food Microbiol, 2000 Dec 20, 62(3), 177 - 81 Listeria in tropical fish and fishery products; Karunasagar I et al.; Listeria monocytogenes is considered to be a ubiquitous organism occurring in both terrestrial and aquatic habitats . This organism has been isolated from fish and fishery products from different parts of the world and interestingly the incidence rate reported from tropical fish is rather low . Varying methodologies have been used by different investigators to study the incidence of L . monocytogenes in fish . Data on virulence of seafood-associated strains are lacking . For quality assurance in the fish processing industry, rapid and sensitive methods for the detection of L . monocytogenes are required. Int J Food Microbiol, 2000 Dec 20, 62(3), 173 - 5 Lessons from an outbreak of listeriosis related to vacuum-packed gravad and cold-smoked fish; Tham W et al.; The first lesson learned from this outbreak was that vacuum-packed rainbow trout is not only an excellent medium for the growth of Listeria monocytogenes, but may also cause human listeriosis . Another lesson is that one single fish processing plant may spread multiple clonal types of L . monocytogenes by selling contaminated products to consumers . Thus, when investigating fish-borne outbreaks of listeriosis one should identify and type several isolates of L . monocytogenes from each food and environmental sample, since multiple clonal types might be present . The outbreak described in this paper involved at least eight human cases, three clonal types of L . monocytogenes, and lasted for 11 months . During the outbreak investigation, L . monocytogenes was also isolated from another brand of rainbow trout found in the refrigerator of one of the patients . These latter isolates belonged to a clonal type not associated with the outbreak . However, this clonal type is of considerable interest since it has been associated with foodborne outbreaks of listeriosis in several countries, and is also the second most common clonal type among human clinical isolates of L . monocytogenes in Sweden . Besides the described outbreak, it is likely that vacuum-packed, cold-smoked and gravad rainbow trout have been involved in additional cases of foodborne listeriosis in Sweden. Curr Opin Immunol, 2001 Feb, 13(1), 96 - 103 The use of host cell machinery in the pathogenesis of Listeria monocytogenes; Cossart P et al.; The bacterial pathogen, Listeria monocytogenes, exploits the host cell's machinery, enabling the pathogen to enter into cells and spread from cell to cell . Three bacterial surface proteins are crucial for these processes: internalin and InlB, which mediate entry into cells, and ActA, which induces actin polymerisation at one pole of the bacterium and promotes intracellular and intercellular motility . Recent studies have identified several of the cellular factors involved in the entry process and major discoveries have unravelled the mechanisms underlying the actin-based motility . Increasing evidence shows that many cellular genes are up- or down-regulated during infection and probably play a role in the establishment of infection, inflammation and induction of the host immune response. Inhal Toxicol, 2001 Jan, 13(1), 85 - 102 Strain-related differences of nonspecific respiratory defense mechanisms in rats using a pulmonary infectivity model; Antonini JM et al.; A number of animal studies have assessed pulmonary host defense mechanisms by inoculating the lungs with the bacterial agent, Listeria monocytogenes . Most studies use only a single strain of the animal to be tested; however, strain-related differences in responsiveness to pulmonary toxicants have been well documented . It was the goal of this current investigation to measure the pulmonary defense responses of two different strains of rats in a lung infectivity model . Fischer 344 (F344) and Sprague-Dawley (SD) rats were instilled intratracheally with 5 x 10(3) or 5 x 10(5) L . monocytogenes, and the effect on mortality, lung injury and inflammation, pulmonary bacterial clearance, and alveolar macrophage (AM) function was determined at 3, 5, and 7 days after bacteria treatment . Pulmonary inoculation with the higher (5 x 10(5) L . monocytogenes) dose proved to be highly pneumotoxic to the F344 rats as evidenced by an increase in mortality and more severe lung injury and inflammation when compared with the SD rats . After intratracheal instillation with the lower (5 x 10(3) L . monocytogenes) dose, pulmonary bacterial clearance was slowed and an increase in pulmonary responsiveness was observed for the F344 rats as compared to the SD rats . Specifically, the total number of neutrophils recovered from the lungs and tumor necrosis factor-alpha secreted by AMs were elevated for the F344 group throughout the 7 days, while cellular chemiluminescence, an index of reactive oxygen species production, and lung albumin and lactate dehydrogenase, indicators of injury, were increased at 3 and 5 days after bacterial instillation . This study demonstrated that respiratory defense function was compromised in F344 rats as evidenced by elevated mortality, slowed pulmonary bacterial clearance, and altered AM function . F344 rats may then represent a sensitive model for the examination of respiratory defense mechanisms after bacterial challenge. Diagn Microbiol Infect Dis, 2000 Dec, 38(4), 259 - 61 In vitro activities of 22 antimicrobial agents against Listeria monocytogenes strains isolated in Barcelona, Spain . The Collaborative Study Group of Listeriosis of Barcelona; Marco F et al.; The in vitro activity of 22 antimicrobial agents against 82 human Listeria monocytogenes strains isolated in Barcelona from 1994 to 1998 was determined . Ampicillin and gentamicin showed good in vitro activity against all strains (MIC90: 1 and < or = 0.25 microg/ml, respectively) . No resistance to rifampin or co-trimoxazole was detected and only one strain was resistant to tetracycline . Of the nine fluoroquinolones tested, clinafloxacin and gemifloxacin were the most active compounds (MIC90: 0.12 and 0.25 microg/ml, respectively) . No increasing MICs values were observed during the five-year period. J Immunol, 2001 Jan 15, 166(2), 1132 - 40 Variable immunodominance hierarchies for H2-M3-restricted N-formyl peptides following bacterial infection; Kerksiek KM et al.; H2-M3-restricted presentation of N-formyl methionine (f-Met) peptides to CD8(+) T cells provides a mechanism for selective recognition of bacterial infection . In this report we demonstrate that Listeria monocytogenes infection induces distinct CD8(+) T cell populations specific for each of the known Listeria-derived formyl methionine peptides presented by M3 . The sum H2-M3-restricted, Listeria-specific T cell response constitutes a major fraction of the total CD8(+) T cell response to primary infection . H2-M3-restricted T cell populations expand synchronously in vivo and achieve peak frequencies approximately 2 days earlier than MHC class Ia-restricted T cell populations . Although cross-recognition of different f-Met peptides by M3-restricted T cells was previously described, costaining of CD8(+) T cells ex vivo with H2-M3 tetramers complexed with different f-Met peptides shows that the majority of Listeria-specific, M3-restricted CD8(+) T cells are peptide specific . In contrast to the highly predictable size and immunodominance hierarchies of MHC class Ia-restricted T cell responses, the magnitudes of T cell responses specific for H2-M3-restricted peptides are remarkably variable between genetically identical mice . Our findings demonstrate that H2-M3-restricted T cell responses are distinct from classically restricted T cell responses to bacterial infection. Am J Pathol, 2001 Jan, 158(1), 179 - 88 Role of macrophage scavenger receptors in response to Listeria monocytogenes infection in mice; Ishiguro T et al.; Type I and type II macrophage scavenger receptors (SR-A I/II) recognize a variety of polyanions including bacterial cell-wall products such as lipopolysaccharide, suggesting a role for SR-A I/II in immunity against bacterial infection . SR-A I/II-deficient (MSR-A-/-) mice were more susceptible to infection with listeriolysin-O (LLO)-producing Listeria monocytogenes . After infection, Kupffer cells in wild-type (MSR-A+/+) mice phagocytized larger numbers of Listeria than those in MSR-A-/- mice . The number and the diameter of hepatic granulomas were larger in MSR-A-/- mice than MSR-A+/+ mice . L . monocytogenes replicated at higher levels in the liver of MSR-A-/- mice compared with MSR-A+/+ mice, and macrophages from MSR-A-/- mice showed impaired ability to kill Listeria in vitro . However, macrophages from MSR-A+/+ and MSR-A-/- mice showed similar levels of listericidal activity against isogenic mutant L . monocytogenes with an inactivated LLO gene . The listerial phagocytic activities of MSR-A+/+ macrophages treated with an anti-SR-A I/II antibody (2F8) and MSR-A-/- macrophages were significantly impaired compared with untreated MSR-A+/+ macrophages, indicating that SR-A I/II function as a receptor for L . monocytogenes . Electron microscopy revealed that most L . monocytogenes had been eliminated from the lysosomes of MSR-A+/+ macrophages in vivo and in vitro . In contrast, L . monocytogenes rapidly lysed the phagosomal membrane and escaped to the cytosol in MSR-A-/- macrophages and in MSR-A+/+ macrophages treated with 2F8 before phagosome-lysosome fusion . These findings imply that SR-A I/II plays a crucial role in host defense against listerial infection not only by functioning as a receptor but also by mediating listericidal mechanisms through the regulation of LLO-dependent listerial escape from the macrophages. Int J Food Microbiol, 2000 Dec 5, 62(1-2), 57 - 63 Occurrence of and a possible mechanism for resistance to a quaternary ammonium compound in Listeria monocytogenes; Aase B et al.; In a study of 200 Listeria monocytogenes isolates, 10% were determined to be resistant to benzalkonium chloride (BC) . Serial subcultivation of initially BC sensitive (BC(S)) and BC resistant (BC(R)) isolates in sublethal concentrations of BC resulted in enhanced and approximately equal resistance of all strains to the compound . Fifty per cent of the BC(R) isolates showed resistance to ethidium bromide (EB) as well . A proton motive force (pmf)-dependent efflux of EB was demonstrated in BC(R) isolates, and in originally sensitive strains adapted to grow in BC . This efflux was not found in BC(S) strains . The result indicate that BC can induce a broad resistance mechanism based on a pmf-driven efflux pump . There was no indication that this type of resistance was related to resistance to antibiotics. Int J Food Microbiol, 2000 Dec 5, 62(1-2), 155 - 9 Pulsed-field gel electrophoresis (PFGE) typing of Listeria strains isolated from a meat processing plant over a 2-year period; Senczek D et al.; As part of a hygiene monitoring program in a meat processing plant a total of 131 Listeria isolates were detected by sampling different processing areas and meat products within a 2-year period . The isolates were differentiated by means of phenotypic characteristics . Furthermore, the genomic ApaI and SmaI fragment patterns of all isolates were examined by pulsed-field gel electrophoresis (PFGE) . PFGE using SmaI and ApaI yielded 15 (Listeria monocytogenes), 20 (Listeria innocua) and six (Listeria welshimeri) pulsotypes . Of the environmental Listeria monocytogenes isolates the predominating PFGE-type B was clearly associated with processing area A whereas PFGE-type E predominated in the meat products . Moreover, the study showed the persistence of closely related Listeria strains over a 2-year period in the environment of this meat processing plant. Int J Food Microbiol, 2000 Dec 5, 62(1-2), 149 - 53 Behaviour of Listeria monocytogenes during the manufacture and ripening of Manchego and Chihuahua Mexican cheeses; Solano-Lopez C et al.; The ability of Listeria monocytogenes to survive the Mexican Manchego and Chihuahua cheese-making processes and its persistence during the ripening stages of both cheeses was examined . Commercial pasteurized and homogenized whole milk was inoculated with Listeria monocytogenes (strain ATCC 19114) to a level between 2 x 10(6) and 9 x 10(6) CFU/ml . The milk was used to make Mexican Manchego and Chihuahua cheeses in a 25-l vat . Mexican Manchego cheese was ripened for 5 days and Chihuahua cheese for 6 weeks at 12 degrees C and 85% RH . Listeria present in the cheese was enumerated by diluting samples in sterile 0.1% peptone water and plating on Oxford agar . Duplicate samples were taken at each step of the manufacturing process . During the first week of ripening samples were taken daily from both cheeses . For Chihuahua cheese, samples were taken weekly after the first week of the ripening stage . During the manufacture of Mexican Manchego cheese, Listeria counts remained relatively constant at 10(6) CFU/ml, while with Chihuahua cheese there was a one log decrease in numbers (10(6) to 10(5) CFU/ml) . After pressing both curds overnight, numbers of bacteria decreased in Mexican Manchego cheese to 8.2 x 10(5) but increased in Chihuahua cheese from 1.7 x 10(5) to 1.2 x 10(6) CFU/ml . During the ripening stage, counts of Listeria remained constant in both cheeses . However, since the Chihuahua cheese ripening stage is about 6 weeks, the number of bacteria decreased from 2 x 10(6) to 4 x 10(4) CFU/g . The results show that Listeria monocytogenes is able to survive the manufacture and ripening processes of both Mexican cheeses. Appl Environ Microbiol, 2001 Jan, 67(1), 198 - 205 Molecular studies on the ecology of Listeria monocytogenes in the smoked fish processing industry; Norton DM et al.; We have applied molecular approaches, including PCR-based detection strategies and DNA fingerprinting methods, to study the ecology of Listeria monocytogenes in food processing environments . A total of 531 samples, including raw fish, fish during the cold-smoking process, finished product, and environmental samples, were collected from three smoked fish processing facilities during five visits to each facility . A total of 95 (17.9%) of the samples tested positive for L . monocytogenes using a commercial PCR system (BAX for Screening/Listeria monocytogenes), including 57 (27.7%) environmental samples (n = 206), 8 (7.8%) raw material samples (n = 102), 23 (18.1%) samples from fish in various stages of processing(n = 127), and 7 (7.3%) finished product samples (n = 96) . L . monocytogenes was isolated from 85 samples (16.0%) using culture methods . Used in conjunction with a 48-h enrichment in Listeria Enrichment Broth, the PCR system had a sensitivity of 91.8% and a specificity of 96.2% . To track the origin and spread of L . monocytogenes, isolates were fingerprinted by automated ribotyping . Fifteen different ribotypes were identified among 85 isolates tested . Ribotyping data established possible contamination patterns, implicating raw materials and the processing environment as potential sources of finished product contamination . Analysis of the distribution of ribotypes revealed that each processing facility had a unique contamination pattern and that specific ribotypes persisted in the environments of two facilities over time (P < or = 0.0006) . We conclude that application of molecular approaches can provide critical information on the ecology of different L . monocytogenes strains in food processing environments . This information can be used to develop practical recommendations for improved control of this important food-borne pathogen in the food industry. J Appl Microbiol, 2000 Dec, 89(6), 944 - 50 Effect of various environmental parameters on the recovery of sublethally salt-damaged and acid-damaged Listeria monocytogenes; Gnanou Besse N et al.; The influence of supplementing the culture medium with magnesium sulphate, D-glucose, L-cysteine, catalase or lithium chloride, of incubation temperature and of oxygen availability on the recovery of salt- or acid-damaged Listeria monocytogenes, was studied on a solid repair medium according to a Hadamard matrix, with seven parameters varying between a high and a low level . The most important factors for repair of stressed Listeria were further studied with complete factorial design experiments . Results show that conditions promoting resuscitation of acid- or salt-injured cells are stress-specific, and differ in part from those described in the literature for heat-stressed Listeria. J Immunol, 2001 Jan 1, 166(1), 466 - 72 Listeria monocytogenes modulates macrophage cytokine responses through STAT serine phosphorylation and the induction of suppressor of cytokine signaling 3; Stoiber D et al.; Macrophage activation as part of natural resistance to infection is caused by stimulation with IFN-gamma and by the invading microorganisms or microbial products . Infection of macrophages with the Gram-positive bacterium LISTERIA: monocytogenes for short periods before activation with IFN-gamma increased the phosphorylation of transcription factor STAT1 at S727 and thereby the expression of IFN-gamma-induced genes . By contrast, persistent infection with viable bacteria or treatment with heat-killed LISTERIA: diminished IFN-gamma-stimulated transcription and the phosphorylation of STAT1 at Y701 . Decreased IFN-gamma signaling correlated with the induction of suppressor of cytokine signaling 3 (SOCS3) mRNA and protein . Contrasting our previous findings with LPS, maximal synthesis of SOCS3 required both the immediate signals from LISTERIA: receptors on the cell surface and the activity of a polypeptide secreted in response to bacterial infection . SOCS3 induction by the secreted protein could not be blocked by neutralizing Abs to IL-10 and it did not require the presence of STAT1 . Consistent with the induction of SOCS3 activity, LISTERIA: also inhibited activation of STAT5 by GM-CSF . The p38 mitogen-activated protein kinase was rapidly activated upon infection of macrophages with L . monocytogenes . Inhibition of p38 mitogen-activated protein kinase with the pyridinyl imidazol SB203580 abrogated both STAT1 S727 phosphorylation and the expression of SOCS3 . The data suggest that STAT1 serine kinase and SOCS3 activity are hallmarks of immediate and delayed phases of influence by bacterial signals on signal transduction in response to IFN-gamma. J Immunol, 2000 Dec 15, 165(12), 6833 - 9 Early programming of T cell populations responding to bacterial infection; Mercado R et al.; The duration of infection and the quantity of Ag presented in vivo are commonly assumed to influence, if not determine, the magnitude of T cell responses . Although the cessation of in vivo T cell expansion coincides with bacterial clearance in mice infected with Listeria monocytogenes, closer analysis suggests that control of T cell expansion and contraction is more complex . In this report, we show that the magnitude and kinetics of Ag-specific T cell responses are determined during the first day of bacterial infection . Expansion of Ag-specific T lymphocyte populations and generation of T cell memory are independent of the duration and severity of in vivo bacterial infection . Our studies indicate that the Ag-specific T cell response to L . monocytogenes is programmed before the peak of the innate inflammatory response and in vivo bacterial replication. Brain Behav Immun, 2000 Dec, 14(4), 305 - 17 Immunotoxic effects of inorganic lead on host resistance of mice with different circling behavior preferences; Kim D et al.; We have observed differential immune responses in mice with different circling preferences, which are posited to reflect interindividual immune response differences influenced by brain laterality effects on neuroimmune circuits . In this study, we have investigated the influence of inorganic lead (Pb) and/or Listeria monocytogenes (LM) infection on the cytokine and corticosterone (CORT) levels of mice grouped by lateralized behavior . Pb increased the LM susceptibility of mice with both left (LC)- and right-circling (RC) preferences; however, Pb did not inhibit the host resistance of mice with no circling preference (NP mice) . The basal serum IFNgamma levels were lowered in all groups after Pb exposure, which coincided with a decrease in host resistance in LC and RC mice, but not NP mice . Pb also altered the basal serum CORT levels, and these changes appear to correlate better with changes in the host resistance of all groups . The basal CORT levels were significantly lowered by Pb in mice with a circling preference, and Pb significantly suppressed the host resistance of mice with a circling preference . However, Pb slightly increased the serum CORT level of NP mice, and their host resistance was slightly improved by Pb . After infection, the increase in CORT levels was associated with an increase in the serum IL-6 levels, which may reflect cytokine influences on the hypothalamic-pituitary-adrenal axis . At 3 days after infection, the serum IL-6 level seems to be a good indicator of the severity of the infection . We suggest that environmental stressors can reorder the observed differential susceptibility to LM in mice with different circling preferences, in that relatively resistant mice (RC mice) become more susceptible than NP mice after exposure to Pb . The results suggest that environmental stressors may have differential effects among individuals with endogenous differences in their neuroimmune circuits, since brain laterality is known to influence immune functions. Epidemiol Infect, 2000 Oct, 125(2), 303 - 8 Comparative investigations of Listeria monocytogenes isolated from a turkey processing plant, turkey products, and from human cases of listeriosis in Denmark; Ojeniyi B et al.; Listeria monocytogenes was isolated from critical control points in a Danish turkey processing plant, from turkey products and from cases of human listeriosis . During processing in the plant the prevalence of L . monocytogenes ranged from 25.9 to 41.4% . Cleaning and disinfection decreased the prevalence to 6.4% . Isolates of L . monocytogenes were characterized by pulsed-field gel electrophoresis (PFGE) using restriction endonuclease ApaI . Identical DNA types were obtained from turkey products and the processing line even after cleaning and disinfection . Two identical DNA types were demonstrated among isolates from turkey products and human cases of listeriosis . The prevalence of L . monocytogenes in turkey products ranged from 7.3 to 17.4% for ready-to-eat products and raw products, respectively . Since none of the 27 flocks examined before slaughter sampled positive for L . monocytogenes and the prevalence increased during processing, the potential risk from turkey meat was apparently due to factory hygiene rather than intrinsic contamination of the turkeys. Clin Immunol, 2000 Dec, 97(3), 193 - 202 Allergen immunotherapy: novel approaches in the management of allergic diseases and asthma; Campbell D et al.; Currently available pharmacotherapies for allergic diseases and asthma, which are serious public health problems, are aimed primarily at neutralizing effector molecules and inflammatory mediators such as histamine and leukotrienes or at inhibiting the function of inflammatory cells such as eosinophils and Th2 lymphocytes . While this approach is effective in controlling symptoms, these therapies have a limited capacity to alter the natural course of allergic diseases and asthma, and discontinuation of medications results in the redevelopment of symptoms on reexposure to the offending allergens . In contrast, immune-based allergen immunotherapies modify and correct the underlying pathological immune responses in allergy and asthma in an antigen-specific manner . These immunotherapies replicate the regulatory processes that occur in nonallergic individuals and allow patients to tolerate exposure to allergens . Current and future methodologies for immunotherapy involve immunization with allergen, modified allergen, peptides of allergen, cDNA of allergen, with adjuvants, including immunostimulatory DNA sequences, cytokines, and bacterial products such as Listeria monocytogenes . This form of therapy can provide a long-lasting cure for allergic diseases without the need for continuous therapeutic intervention and without causing generalized immunosuppression or immune augmentation . Int Microbiol, 1998 Mar, 1(1), 11 - 8 The sophisticated survival strategies of the pathogen Listeria monocytogenes; Wehland J et al.; The function of the ActA protein of Listeria monocytogenes has been partially elucidated . These results illustrate the sophistication with which intracellular pathogens like Listeria use the host cell to their advantage, and have provided new insights into some of the molecular mechanisms of complex cell functions such as actin-promoted cell motility . The clarification of these processes is of fundamental importance not only for understanding elementary processes such as development and growth, but also for the treatment of both diseases caused by cytopathogenic bacteria such as Listeria and pathophysiological processes arising from disorders in cell motility and cell adhesion. J Gastroenterol Hepatol, 2000 Oct, 15(10), 1145 - 50 Detection of Listeria monocytogenes by polymerase chain reaction in intestinal mucosal biopsies from patients with inflammatory bowel disease and controls; Chen W et al.; BACKGROUND AND AIMS: Components of the intestinal microflora are believed to play an important role in the pathogenesis of inflammatory bowel disease (IBD) in genetically susceptible hosts acting either as a non-specific antigenic stimulus or as a specific pathogen . Listeria monocytogenes has been suggested as an organism with the potential to cause IBD . The objective of the present study was to investigate the prevalence of L . monocytogenes DNA in intestinal biopsies from patients with IBD and from non-IBD controls by using nested polymerase chain reaction (PCR) . METHODS: The DNA was extracted from 274 colonoscopic biopsies, which were obtained from 23 patients with Crohn's disease (CD), 28 with ulcerative colitis (UC) and 39 non-IBD control patients . Nested PCR amplification was used to detect the presence of the L . monocytogenes listeriolysin O (hly) gene . The sequences of positive PCR products were determined and compared with databases . RESULTS: The sensitivity of our nested PCR was 10 fg L . monocytogenes DNA . Overall, L . monocytogenes DNA was detected in 13.0% patients with CD, 17.9% patients with UC and 25.6% non-IBD control patients or in 29 of 274 (10.6%) endoscopic biopsies . Among them, L . monocytogenes DNA was detected in four of 67 (6%) biopsies from patients with CD, five of 94 (5.3%) biopsies from patients with UC and 20 of 113 biopsies (17.7%) from non-IBD control patients . Sequence analysis of positive PCR products demonstrated more than 95% similarity to the hly gene sequence of L . monocytogenes, confirming the authenticity of our PCR products . CONCLUSION: Listeria monocytogenes DNA was detected in the intestine of both patients with IBD and in non-IBD control patients, probably reflecting the widespread presence of this organism in the environment . The low yield of positive biopsies in our IBD patients (5-6%) and the fact that the detection rate of L . monocytogenes DNA was similar in endoscopic biopsies from IBD patients and non-IBD controls does not support a direct role for L . monocytogenes in the pathogenesis of IBD, at least in New Zealand patients. Immunopharmacol Immunotoxicol, 2000 Nov, 22(4), 721 - 40 Stimulatory action of Pluchea quitoc extract on the hematopoietic response during murine listeriosis; Queiroz ML et al.; The importance of both granulocytes and macrophages in the response to Listeria monocytogenes infection make this infection a suitable choice to investigate the effects of Pluchea quitoc on hematopoiesis . A significant depletion of bone marrow granulocyte-macrophage progenitor cells (CFU-GM) was observed at 48 and 72 h after intraperitoneal infection of mice with 1 x 10(4) L . monocytogenes . However, the treatment of infected animals with P . quitoc ethanolic extract (250, 500 or 1000 mg/kg) given orally for 3 consecutive days prior to infection produced a stimulatory effect on myelopoiesis, restoring the number of CFU-GM to normal . This same dose-schedule also increased colony formation in normal mice as compared to controls . In addition, P . quitoc significantly enhanced survival of infected mice . Thus, it is probable that the ability of P . quitoc to induce a higher reserve of granulocyte-macrophage precursors in the bone marrow is of major significance in determining early resistance to infection. FEMS Microbiol Lett, 2000 Dec 1, 193(1), 155 - 9 Effect of acid-adaptation on Listeria monocytogenes survival and translocation in a murine intragastric infection model; Saklani-Jusforgues H et al.; Acid tolerance response mechanisms can greatly influence Listeria monocytogenes survival in low pH foods . In the present paper, the effect of acid-adaptation together with control of gastric pH level on L . monocytogenes survival and translocation was analyzed after intragastric inoculation in the BALB/c mouse model . Our results showed that acid-adaptation led to an increase in resistance to the first barrier constituted by the low gastric pH and that inoculation at alkaline pH had a synergistic effect . It resulted in a higher live bacterial load reaching the next intestinal compartments and was correlated with increased translocation rates to the mesenteric lymph nodes, both at the frequency and quantitative levels . Our results in this murine model suggest that acid-adaptation of L . monocytogenes in low pH foods, together with control of gastric pH level through dietary practices, or use of inhibitors of gastric acid secretion, may be potential aggravating risk factors to food-borne listeriosis. Curr Treat Options Neurol, 1999 May, 1(2), 147 - 156 Bacterial Meningitis; Roos KL; Initial empiric therapy for community-acquired bacterial meningitis should be based on the possibility that penicillin-resistant pneumococci may be the etiologic organisms and, hence, should include a combination of third-generation cephalosporin (cefotaxime or ceftriaxone) and vancomycin . Ampicillin should be included if the patient has predisposing factors that are associated with a risk for infection with Listeria monocytogenes . Bacterial isolates from the cerebrospinal fluid should be tested for antimicrobial susceptibility . Understanding the significance of inflammatory cytokines in the pathophysiology of bacterial meningitis leads to an understanding of the need to prevent their formation . Dexa- methasone inhibits synthesis of the inflammatory cytokines, interleukin-1 and tumor necrosis factor . Results of clinical trials and meta-analysis suggest that dexamethasone therapy improves the outcome for patients with bacterial meningitis . Dexamethasone should be administered before or with the first dose of antibiotics . The development of therapeutic modalities to downregulate host inflammatory responses, such as those of monoclonal antibodies to cytokines, is of utmost importance. Eur J Immunol, 2000 Dec, 30(12), 3447 - 56 Human dendritic cells infected by Listeria monocytogenes: induction of maturation, requirements for phagolysosomal escape and antigen presentation capacity; Paschen A et al.; An important feature of microbial infections is the ability of the microorganisms to interfere with and modulate the induction of host immune reactions . However, little is known about the effects of broad host range pathogens such as Listeria monocytogenes on similar cell types in different hosts . Here we examine the effects of the human and animal pathogen L . monocytogenes on human dendritic cells (DC) since this type of cells is essential for the initiation of immune responses . Listeria are phagocytosed efficiently by immature human DC and the bacteria escape from the phagolysosome quickly . Lack of the pore-forming activity of listeriolysin, which was found to be essential for the vacuolar escape of this bacterium in other cell types, retarded but did not prevent egress from the vacuole . Treatment of cultures of immature DC with L . monocytogenes resulted in rapid changes in morphology and cellular constitution followed by maturation of the DC . This could be judged by the appearance of maturation-specific cell surface markers . Antigen presentation to CD4 T cells was apparently not impaired by the infection . These results are in clear contrast to results obtained previously in the mouse system (Guzman et al., Mol . Microbiol . 1996 . 20: 119 - 126; Darji et al., Eur . J . Immunol . 1997 . 27: 1696 - 1703.). J Bacteriol, 2000 Dec, 182(24), 7083 - 7 Role of sigma(B) in adaptation of Listeria monocytogenes to growth at low temperature; Becker LA et al.; The activity of sigma(B) in Listeria monocytogenes is stimulated by high osmolarity and is necessary for efficient uptake of osmoprotectants . Here we demonstrate that, during cold shock, sigma(B) contributes to adaptation in a growth phase-dependent manner and is necessary for efficient accumulation of betaine and carnitine as cryoprotectants. J Immunol, 2000 Dec 1, 165(11), 6472 - 9 Depletion of a gamma delta T cell subset can increase host resistance to a bacterial infection; O'Brien RL et al.; Gammadelta T lymphocytes have been shown to regulate immune responses in diverse experimental systems . Because distinct gammadelta T cell subsets, as defined by the usage of certain TCR V genes, preferentially respond in various diseases and disease models, we have hypothesized that the various gammadelta T cell subsets carry out different functions . To test this, we compared one particular gammadelta T cell subset, the Vgamma1(+) subset, which represents a major gammadelta T cell type in the lymphoid organs and blood of mice, to other subsets and to gammadelta T cells as a whole . Using LISTERIA: monocytogenes infection as an infectious disease model, we found that bacterial containment improves in mice depleted of Vgamma1(+) gammadelta T cells, albeit mice lacking all gammadelta T cells are instead impaired in their ability to control LISTERIA: expansion . Our findings indicate that Vgamma1(+) gammadelta T cells reduce the ability of the innate immune system to destroy LISTERIA:, even though other gammadelta T cells as a whole promote clearance of this pathogen. Infect Immun, 2000 Dec, 68(12), 7061 - 8 ClpC ATPase is required for cell adhesion and invasion of Listeria monocytogenes; Nair S et al.; We studied the role of two members of the 100-kDa heat shock protein family, the ClpC and ClpE ATPases, in cell adhesion and invasion of the intracellular pathogen Listeria monocytogenes . During the early phase of infection, a clpC mutant failed to disseminate to hepatocytes in the livers of infected mice whereas the invasive capacity of a clpE mutant remained unchanged . This was confirmed by a confocal microscopy study on infected cultured hepatocyte and epithelial cell lines, showing a strong reduction of cell invasion only by the clpC mutant . Western blot analysis with specific antisera showed that the absence of ClpC, but not that of ClpE, reduced expression of the virulence factors InlA, InlB, and ActA . ClpC-dependent modulation of these factors occurs at the transcriptional level with a reduction in the transcription of inlA, inlB, and actA in the clpC mutant, in contrast to the clpE mutant . This work provides the first evidence that, in addition to promoting escape from the phagosomes, ClpC is required for adhesion and invasion and modulates the expression of InlA, InlB, and ActA, further supporting the major role of the Clp chaperones in the virulence of intracellular pathogens. Science, 2000 Nov 17, 290(5495), 1354 - 8 Regulation of antigen-specific CD8+ T cell homeostasis by perforin and interferon-gamma; Badovinac VP et al.; T cell memory depends on factors that regulate expansion and death of these cells after antigenic stimulation . Mice deficient in perforin and interferon-gamma (IFN-gamma) exhibited increased expansion, altered immunodominance, and decreased death of antigen-specific CD8+ T cells after infection with an attenuated strain of Listeria monocytogenes, which was cleared from these mice . Expansion of CD8+ T cells was controlled by perforin, whereas IFN-gamma regulated immunodominance and the death phase . Thus, perforin and IFN-gamma regulate distinct elements of CD8+ T cell homeostasis independently of their role as antimicrobial effector molecules. Cell, 2000 Oct 27, 103(3), 501 - 10 InIB-dependent internalization of Listeria is mediated by the Met receptor tyrosine kinase; Shen Y et al.; The Listeria monocytogenes surface protein InlB promotes bacterial entry into mammalian cells . Here, we identify a cellular surface receptor required for InlB-mediated entry . Treatment of mammalian cells with InlB protein or infection with L . monocytogenes induces rapid tyrosine phosphorylation of Met, a receptor tyrosine kinase (RTK) for which the only known ligand is Hepatocyte Growth Factor (HGF) . Like HGF, InlB binds to the extracellular domain of Met and induces "scattering" of epithelial cells . Experiments with Met-positive and Met-deficient cell lines demonstrate that Met is required for InlB-dependent entry of L . monocytogenes . InlB is a novel Met agonist that induces bacterial entry through exploitation of a host RTK pathway. Int J Food Microbiol, 2000 Nov 1, 61(2-3), 169 - 75 Effects of combinations of lactoperoxidase system and nisin on the behaviour of Listeria monocytogenes ATCC 15313 in skim milk; Boussouel N et al.; Individual or combined effects of nisin (100 or 200 IU/ml) and the lactoperoxidase system (LPS) were analysed against 1 x 10(4) cfu/ml Listeria monocytogenes ATCC 15313 cells in skim milk, at 25 degrees C for 15 days . Nisin induced an immediate bactericidal effect and LPS a 48 h bacteriostatic phase which in both cases was followed by re-growth of L . monocytogenes . LPS and nisin added together at t0 showed a synergistic and lasting bactericidal effect which after 8 days and until 15 days resulted in no detectable cells in 1 ml of milk . When LPS was added to cells already in contact with 100 or 200 IU/ml nisin for a period of 4 h, the inhibitory activity was enhanced with no L . monocytogenes detectable after 72 or 48 h, respectively, and until 15 days . When LPS was added after 12 h, the nisin bactericidal phase was followed by re-growth . When nisin, 100 or 200 UI/ml, was added to cells already in contact with LPS over 24 h, L . monocytogenes was no