Listeriosis

Blood, 1993 Sep 15, 82(6), 1695 - 700
Results of fludarabine and prednisone therapy in 264 patients with chronic lymphocytic leukemia with multivariate analysis-derived prognostic model for response to treatment; O'Brien S et al.; Two hundred sixty-four patients with chronic lymphocytic leukemia were treated with fludarabine 30 mg/m2 intravenously for 30 minutes each day for 5 days and with prednisone 30 mg/m2 orally each day for 5 days . Courses were repeated monthly . Of the 264 patients . 125 patients (47%) had Rai stage III-IV disease; 169 patients (64%) were previously treated with a median of 3 prior regimens; and 138 of them (82%) were refractory to therapy with alkylating agents . The overall response (OR) and complete response (CR) rates in the 169 previously-treated patients were 52% and 37%; these were 74% and 63%, respectively, in Rai stage O-II patients and declined to 64% and 46%, respectively, in Rai III-IV disease . Among the previously untreated patients, the OR and CR rates were 79% and 63%, these being 85% and 70%, respectively, in Rai O-II patients, and declining to 64% and 46%, respectively, in Rai III-IV disease . The incidence of minor infections or fever of unknown origin was similar in all patient groups and occurred in 22% of courses . The incidence of sepsis and/or pneumonia was significantly correlated with the extent of prior therapy and with Rai stage, and ranged from 3% of courses in the previously untreated Rai O-II patients, to 13% of courses in the previously treated Rai III-IV patients . Listeria sepsis or Pneumocystis carinii pneumonia was noted in 14 patients . With therapy, CD4 levels were uniformly depressed from a median 1,015/microL pretreatment to a median 159/microL after 3 months of fludarabine therapy . Median time to progression in previously treated patients was 22 months . In previously untreated patients, median time to progression was 30 months for patients who achieved a partial remission and has not been reached in patients who achieved a CR with a median follow-up of 2 years . The median survival was 18 months for previously treated patients and has not been reached for previously untreated patients . Response rates in previously treated and untreated patients, as well as infection rates, were identical to those seen in 110 patients treated with the same dose schedule of fludarabine alone . Logistic regression analysis selected 4 factors to be significantly associated with worse response: Rai III-IV stage disease, prior therapy, older age, and low albumin levels . The regression equation was used to derive a probability of response based on the 4 characteristics . When the model was applied to the same population, patients could be divided into 4 prognostic groups with different outcomes.

Commun Dis Rep CDR Rev, 1993 Sep 10, 3(10), R144 - 6
Listeriosis surveillance: 1992; Newton L et al.; The annual reported totals of cases of listeriosis in England, Wales and Northern Ireland have remained low over the last three years and a total of 108 cases was reported in 1992 . The clinical and epidemiological features reported in 1992 were similar to those in previous years and in other countries, except for a shift in the seasonal peak to the summer (a pattern consistently seen before the upsurge in 1987) and a reduction in the case fatality rate of non pregnancy-associated cases.

Nature, 1993 Sep 2, 365(6441), 53 - 6
Different roles of alpha beta and gamma delta T cells in immunity against an intracellular bacterial pathogen; Mombaerts P et al.; Several bacterial pathogens of medical importance are able to persist and replicate inside host mononuclear phagocytes . Protective immunity depends on specific T lymphocytes that induce granulomatous lesions at the sites of bacterial multiplication . Listeria monocytogenes is an intracellular pathogen that replicates inside mononuclear phagocytes and hepatocytes of mice . Invasion from the phagosomal compartment into the cytoplasmic compartment is the principal mechanism of intracellular survival . Early in infection, resistance against L . monocytogenes is mediated by polymorphonuclear phagocytes which destroy infected liver cells, followed by natural killer cells which activate macrophages by means of interferon-gamma (refs 6, 7) . A specific immune response by T cells then develops which leads to sterile eradication of the microbes . T cells are also responsible for the highly effective protection in vaccinated mice against secondary infections . Although the role of alpha beta T cells has been demonstrated in these immune responses, that of gamma delta T cells is unclear . Here we use mice that selectively lack either alpha beta or gamma delta T cells as a result of targeted germ-line mutations in their T-cell receptor genes to investigate the relative roles of these T-cell populations during experimental infection with L . monocytogenes . We find that in primary listeriosis, either alpha beta or gamma delta T cells are sufficient for early protection . Resistance to secondary infection is mediated mainly by alpha beta T cells but also involves gamma delta T cells . Thus alpha beta T-cell-deficient mice can be rendered partially resistant by vaccination, and gamma delta T cells are shown to be responsible for this protective effect . In infected gamma delta T-cell-deficient mice we noticed the appearance of unusual liver lesions, indicating that gamma delta T cells have a unique regulatory role in this bacterial infection.

Infect Immun, 1993 Sep, 61(9), 3901 - 6
Comparison of gamma interferon, tumor necrosis factor, and direct cell contact in activation of antimycobacterial defense in murine macrophages; Sypek JP et al.; We compared the abilities of gamma interferon (IFN-gamma), tumor necrosis factor alpha (TNF-alpha), and sensitized murine lymph node lymphocytes to activate syngeneic murine peritoneal macrophages to inhibit the growth of intracellular Mycobacterium bovis BCG in vitro . IFN-gamma could activate antimycobacterial defense only when added to macrophage cultures prior to their infection with BCG . TNF-alpha was without any effect . In contrast, BCG-sensitized lymphocytes could induce antimycobacterial defenses when added after macrophages had been infected with BCG . The cell-mediated effect required direct contact between effector lymphocytes and the targets (BCG-infected macrophages), as revealed in studies in which these cell populations were separated by a semipermeable membrane . Cyclosporin A, which inhibits the production of relevant macrophage-activating lymphokines, did not abrogate the ability of sensitized lymphocytes to activate antimycobacterial effects in infected macrophages . Furthermore, only BCG-sensitized lymphocytes, and not Listeria-sensitized lymphocytes, could activate the antimycobacterial effects . These lymphocytes were not cytotoxic to the infected macrophages . The presence of anti-TNF-alpha antibody in cocultures reduced the antimicrobial effects . We propose that the activation of antimycobacterial defense in macrophages can occur by direct physical contact with sensitized lymphocytes . This process may be due to lymphocyte membrane-associated TNF-alpha, as we previously demonstrated in our studies of antileishmanial defense.

Infect Immun, 1993 Sep, 61(9), 3756 - 60
Intracytoplasmic growth and virulence of Listeria monocytogenes auxotrophic mutants; Marquis H et al.; The intracellular growth of several auxotrophic mutants of Listeria monocytogenes was examined in cell culture, and virulence was evaluated in mice by intravenous injection of log-phase bacteria . L . monocytogenes transposon insertion mutants requiring either uracil, phenylalanine, glycine, proline, or nicotinic acid for growth were fully virulent and grew similarly to the parental strain as shown by their growth rates in cell culture . Those requiring all three aromatic amino acids (phenylalanine, tryptophan, and tyrosine) or adenine were 1.5 log10 less virulent than the wild type . A threonine auxotroph, which showed enhanced growth in the presence of threonine-containing peptides as compared with that in the presence of free threonine, was approximately 1 log10 less virulent than the wild type . When host cells were deprived of specific amino acids required by both the host cell and L . monocytogenes, the bacteria continued to grow intracellularly . These studies suggest that the cytoplasm of eucaryotic cells behaves like rich medium, facilitating the growth of an intracellular bacterial pathogen with complex growth requirements . In addition, results related to amino acid deprivation during intracellular growth and specific extracellular growth requirements of a threonine auxotroph suggest that L . monocytogenes may utilize intracellular peptides as a source of amino acids.

Infect Immun, 1993 Sep, 61(9), 3739 - 44
Analysis of cytokine mRNA expression in Listeria-resistant C57BL/6 and Listeria-susceptible A/J mice during Listeria monocytogenes infection; Iizawa Y et al.; This laboratory previously reported that mRNA expression for many cytokines, as determined by reverse transcription-polymerase chain reaction analysis, is induced rapidly in the spleen during murine listeriosis . In the present study, the patterns of cytokine mRNA expression in spleens and livers of Listeria-resistant C57BL/6 and Listeria-susceptible A/J mice were compared . In addition, in situ hybridization was performed to evaluate the distributions of cytokine mRNA-expressing cells in these tissues . Listeria-resistant C57BL/6 mice demonstrated greater expression of gamma interferon (IFN-gamma) and granulocyte-macrophage colony-stimulating factor (GM-CSF) mRNAs in the spleen than Listeria-susceptible A/J mice . Greater numbers of cells expressing IFN-gamma and GM-CSF mRNAs were observed by in situ hybridization in the spleens of C57BL/6 mice than in those of A/J mice . C57BL/6 and A/J mice did not differ in their expression of IFN-gamma mRNA in the liver . Nor did C57BL/6 and A/J mice differ in their expression of tumor necrosis factor alpha, interleukin-1 alpha (IL-1 alpha), IL-2, IL-4, or IL-6 mRNA in the liver or spleen, as determined by reverse transcription-polymerase chain reaction and in situ hybridization . These results indicate that the greater resistance of C57BL/6 mice to Listeria monocytogenes infection is associated with greater expression of IFN-gamma and GM-CSF mRNAs in the spleen and GM-CSF mRNA in the liver.

Infect Immun, 1993 Sep, 61(9), 3664 - 72
Role of complement component C1q in phagocytosis of Listeria monocytogenes by murine macrophage-like cell lines; Alvarez-Dominguez C et al.; Listeria monocytogenes is a facultative intracellular pathogen of a great variety of cells . Among them, macrophages constitute the major effector cells of listerial immunity during the course of an infection . Although the molecular bases of L . monocytogenes attachment and entry to phagocytes are not completely understood, it has been demonstrated that C3b significantly increases L . monocytogenes uptake by macrophages via complement receptor type 3 . The first component of complement, C1q, is present in organic fluids at a relatively high concentration, and C1q receptor sites in macrophages are also abundant . In the present report, results of studies on the role of C1q in the internalization and infectivity of L . monocytogenes by macrophages are presented . L . monocytogenes uptake is enhanced by prior treatment of bacteria with normal sera . Heated serum or C1q-deficient serum abrogates this enhancement . Purified C1q specifically restored uptake . This effect was blocked by the addition of F(ab')2 anti-C1q antibody but not by an irrelevant matched antibody . Direct binding of C1q to L . monocytogenes was specific, saturable, and dose dependent with both fluorescent and radiolabeled C1q . N-Acetyl-D-alanyl-L-isoglutamine, diaminopimelic acid, and L-rhamnose caused a significant dose-dependent inhibition of C1q binding to bacteria, suggesting that these molecules, at least, are involved in the attachment of C1q to L . monocytogenes cell wall . When C1q binding structures on macrophage-like cells were blocked with saturating concentrations of C1q, the uptake of C1q-opsonized bacteria was less than in untreated cells . These experiments demonstrate that, in addition to other reported mechanisms, L . monocytogenes binds C1q, which mediates enhanced uptake by macrophages through C1q binding structures.

J Exp Med, 1993 Sep 1, 178(3), 985 - 96
Intercellular interactions and cytokine responsiveness of peritoneal alpha/beta and gamma/delta T cells from Listeria-infected mice: synergistic effects of interleukin 1 and 7 on gamma/delta T cells; Skeen MJ et al.; Peritoneal gamma/delta T cells from Listeria-immune mice show an enhanced potential to expand when restimulated with antigens or mitogens in vitro (see companion paper {Skeen, M . J., and H . K . Ziegler . 1993 . J . Exp . Med . 178:971}) . When cocultured with peritoneal alpha/beta T cells, the gamma/delta T cell population expanded preferentially even when the in vitro stimulus was specific for the alpha/beta T cell population . Purified gamma/delta T cells did not respond to alpha/beta T cell-specific stimuli . If isolated T cell subsets were recombined in cell mixing experiments, the resulting proliferative response was greater than additive . Irradiated alpha/beta T cells could enhance the proliferation of responding gamma/delta T cells, but the effect was unidirectional; i.e., irradiated gamma/delta T cells did not stimulate responding gamma/delta T cells . This effect appeared to be cytokine mediated and did not require cell-cell contact . Both recombinant interleukin 2 (rIL-2) and rIL-7 could support the expansion of the gamma/delta T cells, while rIL-7 was only minimally stimulatory for the alpha/beta T cells . The magnitude of the response by gamma/delta T cells to rIL-7 exceeded the response to other in vitro stimuli, including immobilized anti-T cell receptor monoclonal antibody, and was 50-100-fold greater than the alpha/beta T cell response to IL-7 . This unique sensitivity of gamma/delta T cells to IL-7 was strongly enhanced by the presence of accessory cells . These cells could be replaced by rIL-1, establishing a synergy for IL-1 and IL-7 as factors that could uniquely stimulate this gamma/delta T cell population . Isolated peritoneal gamma/delta T cells from Listeria-immune mice react to heat-killed Listeria preparations in the presence of macrophages accessory cells in a non-H-2-restricted manner . Considered collectively, these results suggest a potential mechanism by which gamma/delta T cells can predominate in epithelial tissues and at sites of infection.

J Exp Med, 1993 Sep 1, 178(3), 971 - 84
Induction of murine peritoneal gamma/delta T cells and their role in resistance to bacterial infection; Skeen MJ et al.; Previous studies have reported an association of gamma/delta T cells with microbial infection in both human lesions and murine infectious disease models . In this study we provide a comprehensive analysis of the conditions under which the induction of gamma/delta T cells occurs at a site of infection . We found a site-specific induction of gamma/delta T cells after the injection of Listeria monocytogenes in the peritoneal cavity of C3H mice . No changes were seen in the splenic or lymph node populations after these injections . Both the proportion and the absolute number of gamma/delta T cells increased in the peritoneal cavity . Additionally, when peritoneal T cells from Listeria-immune mice were restimulated in vitro, the induced gamma/delta T cells exhibited a greater expansion potential than the alpha/beta T cells . Neither the induced gamma/delta T cells nor those from normal mice expressed CD4 or CD8 on the cell surface . Thy-1 was expressed on only 29% of normal peritoneal gamma/delta T cells, but after intraperitoneal Listeria injection 65% of induced gamma/delta T cells expressed . Thy-1, Pgp-1 and CD45R expression on both normal and induced gamma/delta T cells was consistent with an activation phenotype . Significant increases in peritoneal gamma/delta T cells were not seen until 5-7 d after Listeria injection . The proportion of the CD3+ population expressing the gamma/delta T cell receptor remained elevated for 6-7 wk, while the absolute numbers of peritoneal gamma/delta T cells declined gradually over this time period, reflecting a decrease in both the number of lymphocytes and the percentage of these that were CD3+ . Peak numbers of gamma/delta T cells were seen at day 10 with live microbes such as Listeria . A variety of microbes, toxins, mitogens, antigens, cytokines, and nonspecific inflammatory agents were evaluated for their ability to induce gamma/delta T cells in the peritoneal cavity . Both Gram-positive and Gram-negative bacteria as well as Mycobacteria were able to induce gamma/delta T cells that showed increased in vitro expansion potential . An exotoxin from a Gram-positive organism, listeriolysin-o, and the lipopolysaccharide (LPS) endotoxin from a Gram-negative organism were also effective . gamma/delta T cell responses to LPS were under lps gene control . Peak numbers of gamma/delta T cells were observed at day 3 after injection with exotoxins and endotoxins . Modifications that abrogated the virulence of a bacterial strain also eliminated the inductive effect for gamma/delta T cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Int J Food Microbiol, 1993 Sep, 19(4), 271 - 81
The effects of diacetate with nitrite, lactate, or pediocin on the viability of Listeria monocytogenes in turkey slurries; Schlyter JH et al.; The antilisterial effects of sodium diacetate (0.1, 0.3 and 0.5%) alone or in combination with sodium nitrite (30 ppm), sodium lactate (2.5%) or pediocin (5000 arbitrary units/ml) were evaluated in slurries (25% meat in sterile deionized H2O) prepared from vacuum-packaged, ready-to-eat turkey breast meat and challenged with Listeria monocytogenes . In the absence of food additives, counts of L . monocytogenes increased from 4.5 log10 cfu/ml to ca . 8 log10 cfu/ml within 1 day at 25 degrees C and within 14 days at 4 degrees C . Similarly, the pathogen grew to ca . 8 log10 cfu/ml within 1 d at 25 degrees C and within 28 days at 4 degrees C in slurries containing nitrite or lactate . In the presence of pediocin, after an initial decrease of 0.9 log10 cfu/ml, numbers of the pathogen reached ca . 8 log10 cfu/ml within 5 days at 25 degrees C and within 28 days at 4 degrees C . However, 0.3 and 0.5% diacetate in turkey slurries were listericidal at 4 and 25 degree C, respectively . In the presence of nitrite with diacetate, there was no appreciable difference in growth of L . monocytogenes compared with diacetate alone . Antilisterial activity was potentiated in treatments containing lactate with 0.3% diacetate at 25 degrees C and lactate with 0.1% diacetate at 4 degrees C, compared to similar treatments containing diacetate or lactate alone . A listericidal effect (ca . 7 log10 cfu/ml difference compared to slurries without additives) was observed in treatments containing pediocin with 0.5% diacetate at 25 degrees C and pediocin with 0.3% diacetate at 4 degrees C . The pH of slurries containing 0.3 or 0.5% diacetate was 5.5 and 5.2, respectively, whereas nitrite (pH 6.2), lactate (pH 6.3) or pediocin (pH 6.2) in slurries had a negligible effect on pH compared to the control (pH 6.2) . The increased antilisterial activity in slurries with diacetate in combination with other additives was due to synergistic effects and not just pH . Thus, sodium diacetate alone can be used to delay growth of L . monocytogenes in turkey, and an additional level of safety can be achieved using diacetate in combination with sodium lactate or pediocin.

Appl Environ Microbiol, 1993 Sep, 59(9), 3117 - 9
Development of a random amplification of polymorphic DNA typing method for Listeria monocytogenes; Lawrence LM et al.; The 10-mer primer OPM-01 (5'-GTT GGT GGC T-3') was used to generate random amplification of polymorphic DNA (RAPD) profiles by polymerase chain reaction for 91 strains of Listeria monocytogenes from raw milk, food, and veterinary, medical, and food-environmental sources . The profiles obtained contained 1 to 10 bands within the molecular size range of 0.5 to 5.0 kbp . Reproducibility was enhanced by annealing at low stringency and introducing a 1-min ramp time between annealing and extension temperatures . Thirty-three RAPD profiles were observed, with specific profiles being observed for strains from each source . RAPD profiles allowed discrimination within serogroups, although five RAPD profiles which were not confined to one serotype were found . Within food strains, one RAPD profile was more common than others, suggesting this to be a common type among strains from this source.

Appl Environ Microbiol, 1993 Sep, 59(9), 2914 - 7
Biological inactivation of adhering Listeria monocytogenes by listeriaphages and a quaternary ammonium compound; Roy B et al.; The use of listeriaphages as a means of disinfecting contaminated stainless-steel and polypropylene surfaces was investigated . Surfaces artificially contaminated with L . monocytogenes 10401 and 8427 were sanitized with suspensions of listeriaphages (H387, H387-A, and 2671), all belonging to the Siphoviridae family . Phage suspensions at concentrations of up to 3.5 x 10(8) PFU/ml were at least as efficient as a 20 ppm solution of a quaternary ammonium compound (QUATAL) in reducing L . monocytogenes populations . A synergistic activity was observed when two or more phages were used in combination and when phages were suspended in QUATAL . The biological activity of the three phages was not affected by QUATAL concentrations of 50 ppm and a contact time of 4 h.

Appl Environ Microbiol, 1993 Sep, 59(9), 2817 - 22
Application of multilocus enzyme electrophoresis in studies of the epidemiology of Listeria monocytogenes in Denmark; Norrung B et al.; A total of 245 strains of Listeria monocytogenes were investigated . These strains were isolated from human and animal cases of listeriosis as well as from different kinds of raw and processed foods . Thirty-three electrophoretic types (ETs) were identified among the 245 strains . The strains investigated included all human clinical strains isolated in Denmark during 1989 and 1990 . Seventy-three percent of the strains isolated in this period were assigned to one of only two ETs (ET 1 and ET 4) . ET 1, which was found to be the most frequently occurring ET among strains isolated from human clinical cases, was also found to occur rather frequently in animal clinical cases . ET 1 was, however, found only sporadically among strains isolated from foods and food factories . The data indicate that there might be something distinctive about the physiology or ecology of the ET 1 clone which makes it more likely to bring about disease in human beings either because of high pathogenicity or because of a special ability to multiply to infectious doses in processed foods . Another type, designated ET 4, was found to be the next most frequently occurring ET, after ET 1, among human clinical isolates . This could be explained by the fact that ET 4 was found to be the most frequently occurring ET within food isolates.

J S Afr Vet Assoc, 1993 Sep, 64(3), 133 - 6
Generalised Listeria monocytogenes infection in a dog; Schroeder H et al.; A 6-year-old Doberman bitch was presented for an acute onset of circling, hemiparesis and depression . Clinical examination revealed conjunctivitis, abdominal pain, anaemia, decreased facial sensation, decreased jaw, tongue and pharyngeal tone, decreased conscious proprioception, decreased flexor withdrawal reflexes, and abnormal hemiwalking and hemistanding . Pancytopaenia was evident on haematological evaluation . Bone marrow cytology revealed a bacterial infection . Cerebrospinal fluid analysis was normal . Despite antibiotic treatment, the dog died . On autopsy, widespread multifocal inflammatory lesions were found to be present in the lungs, liver, spleen, meninges, lymph nodes, adrenal glands and kidneys . Listeria monocytogenes was isolated in pure culture from these organs and tissues . Histopathological examination showed numerous gram-positive intracellular rod-shaped bacteria seen in all the above-mentioned organs.

Agents Actions, 1993 Sep, 40(1-2), 119 - 23
Influence of acetylsalicylic acid on a Listeria monocytogenes infection; Hockertz S et al.; The influence of acetylsalicylic acid (ASA, CAS 50-78-2) on the Listeria monocytogenes infection in balb/c mice was investigated . One day prior to lethal or sublethal infection, balb/c mice were treated intravenously with therapeutic concentrations of ASA alone or ASA in combination with murine recombinant interferon gamma, a lymphokine produced by T-helper cells . Three days post-infection, parasite burdens of spleen and liver were determined by the colony-forming unit assay . It was shown that the prophylactic application of ASA in a concentration of 5 mg/kg body weight resulted in a more than 10-fold reduction of viable Listeria monocytogenes in spleen and liver of balb/c mice . In addition, the combination of a suboptimal dosage of interferon gamma with ASA resulted in a significantly higher survival rate compared to the untreated controls.

Mol Microbiol, 1993 Sep, 9(6), 1247 - 54
Induction of phagocytic behaviour in human epithelial cells by Escherichia coli cytotoxic necrotizing factor type 1; Falzano L et al.; Cytotoxic necrotizing factor type 1 (CNF1) from strains of pathogenic Escherichia coli induces in human epithelial HEp-2 cells, a profound reorganization of the actin cytoskeleton into prominent stress fibres and membrane ruffles . We report here that this process is associated with induction of phagocytic-like activity . CNF1-treated cells acquired the ability to ingest latex beads as well as non-invasive bacteria such as Listeria innocua, which were taken as a model system . Uptake of bacteria was similar to pathogen-induced phagocytosis, since L . innocua transformed with DNA coding for the pore-forming toxin listeriolysin O behaved, with respect to intracellular growth, like the invasive, pathogenic species L . monocytogenes . Our results raise the possibility that, in vivo, pathogenic CNF1-producing E . coli may invade epithelia by this novel induced phagocytic-like mechanism.

Mol Microbiol, 1993 Sep, 9(5), 931 - 41
Internalin-mediated invasion of epithelial cells by Listeria monocytogenes is regulated by the bacterial growth state, temperature and the pleiotropic activator prfA; Dramsi S et al.; Entry of Listeria monocytogenes into epithelial cells requires expression of inIA, the first gene of an operon comprising two genes: inIA, which encodes internalin, a 800-amino-acid protein, and inIB, which encodes a 630-amino-acid protein . We report here that the inI locus is transcribed on two transcripts in constant relative ratio: a 5 kb transcript spanning inIA and inIB, and a 2.9 kb transcript that covers only inIA . The promoter is located 397 bp from the GTG initiator of inIA and displays in its -35 region a palindrome similar to that found in promoters controlled by the pleiotropic activator prfA . Transcription of the inI locus is, as are several other L . monocytogenes virulence genes, activated by prfA and regulated by temperature--with higher expression at 37 degrees C versus 25 degrees C--and bacterial growth state . It is maximal during exponential growth and correlates with maximal invasivity of the bacteria in the human epithelial cell line Caco-2 . It also correlates with maximum amounts of internalin present on the bacterial surface . Internalin is also detected in substantial amounts in culture supernatants . Taken together, these data suggest that surface-bound internalin plays an important role in bacterial entry but do not exclude a role for the released form.

J Immunol, 1993 Sep 1, 151(5), 2742 - 52
Isolation of a macrophage-like cell line defective in binding of lipopolysaccharide . Influence of serum and lipopolysaccharide chain length on macrophage activation; Kirikae T et al.; A mutant cell line (J7.DEF.3) derived from murine macrophage-like J774.1 cells, was isolated on the basis of defective specific 125I-labeled LPS-binding in the presence of serum . Although J7.DEF.3 cells still respond to LPS in inducing TNF-alpha release and nitric oxide (NO) formation, these cells nevertheless showed significantly decreased responsiveness to LPS relative to the J774.1 parent . Under serum-free conditions, no differences between J774.1 and J7.DEF.3 cells in response to LPS were observed . The time kinetics of responsiveness to LPS also showed a delay in the onset of TNF-alpha release and NO formation in the mutant cells relative to parent cells . Importantly, this decrease in responsiveness to LPS relative to parental cells was dependent on the length of the polysaccharide portion of LPS . The defect in the mutant cells has been shown to be specific for LPS, in that these cells respond to heat-killed Listeria monocytogenes and to zymosan to a similar extent as do the parental cells . Collectively these results suggest that the defect in the J7.DEF.3 mutant cells may be related to a cellular LPS-binding molecule that, in turn, may depend upon an LPS-binding serum component.

Nature, 1993 Aug 26, 364(6440), 798 - 802
Mice lacking the tumour necrosis factor receptor 1 are resistant to TNF-mediated toxicity but highly susceptible to infection by Listeria monocytogenes; Rothe J et al.; Tumour necrosis factor (TNF), jointly referring to TNF alpha and TNF beta, is a central mediator of immune and inflammatory responses; its activities are mediated by two distinct receptors, TNFR1 (p55) and TNFR2 (p75) (reviewed in refs 1-3) . The cytoplasmic domains of the TNFRs are unrelated, suggesting that they link to different intracellular signalling pathways . Although most TNF responses have been assigned to one or the other of the TNF receptors (mostly TNFR1), there is no generally accepted model for the physiological role of the two receptor types . To investigate the role of TNFR1 in beneficial and detrimental activities of TNF, we generated TNFR1-deficient mice by gene targeting . We report here that mice homozygous for a disrupted Tnfr1 allele (Tnfr1(0)) are resistant to the lethal effect of low doses of lipopolysaccharide after sensitization with D-galactosamine, but remain sensitive to high doses of lipopolysaccharide . The increased susceptibility of Tnfr1(0)/Tnfr1(0) mutant mice to infection with the facultative intracellular bacterium Listeria monocytogenes indicates an essential role of TNF in nonspecific immunity.

Immunology, 1993 Aug, 79(4), 594 - 9
Inhibition of interferon-gamma by an interferon-gamma receptor immunoadhesin; Haak-Frendscho M et al.; Interferon-gamma (IFN-gamma) is an important cytokine which regulates inflammatory and immune response mechanisms . IFN-gamma enhances the presentation and recognition of antigens by inducing the expression of major histocompatibility complex (MHC) proteins, by activating effector T cells and mononuclear phagocytes, and by modulating immunoglobulin production and class selection in B cells . Inappropriate production of IFN-gamma has been implicated in the pathogenesis of several autoimmune and inflammatory diseases and in graft rejection . Here, we describe a recombinant inhibitor of IFN-gamma, termed murine IFN-gamma receptor immunoadhesin (mIFN-gamma R-IgG) . We constructed this immunoadhesin by linking the extracellular portion of the mouse IFN-gamma R to the hinge and Fc region of an IgG1 heavy chain . Murine IFN-gamma R-IgG is secreted by transfected cells as a disulphide-bonded homodimer which binds IFN-gamma bivalently, with high affinity and in a species-specific manner . In vitro, mIFN-gamma R-IgG can block mIFN-gamma-induced antiviral activity and expression of the class I MHC antigen H-2Kk in cultured cells . In vivo, mIFN-gamma R-IgG can block the function of endogenous mIFN-gamma in mouse models of infection with Listeria monocytogenes and of contact sensitivity . These results show that mIFN-gamma R-IgG is an effective and specific inhibitor of mIFN-gamma both in vitro and in vivo . Thus, in general, IFN-gamma receptor immunoadhesins may be useful for investigating the biological functions of IFN-gamma as well as for preventing deleterious effects of IFN-gamma in human disease.

FEMS Immunol Med Microbiol, 1993 Aug, 7(2), 131 - 4
Serological response in rabbits to Listeria monocytogenes after oral or intragastric inoculation; Belen Lopez M et al.; The serological response in rabbits against Listeria monocytogenes after oral or intragastric inoculation was investigated . Both the number of sero-positive animals and the average serum titres were higher in animals inoculated by the oral route . This difference was especially marked in rabbits inoculated with the lower dose (1 x 10(3) colony-forming units (cfu)), which developed a strong serological response (average serum titre of 1280 after 4 inoculations) in most of the inoculated animals (80%), without any clinical signs . The implication of these results in the epidemiology of listeriosis is discussed.

Clin Infect Dis, 1993 Aug, 17(2), 267 - 9
Liver abscess due to Listeria monocytogenes: case report and review; Braun TI et al.; Involvement of the liver in cases of Listeria monocytogenes infection is uncommon but has been manifested as solitary liver abscess, multiple liver abscesses, and hepatitis . We describe a 73-year-old diabetic woman who presented with a solitary liver abscess and prolonged fever, and we review the world literature on hepatic manifestations of L . monocytogenes infection . Patients presenting with solitary liver abscesses uniformly recovered with antimicrobial therapy and abscess drainage, whereas almost all patients presenting with multiple liver abscesses died.

Clin Infect Dis, 1993 Aug, 17(2), 224 - 7
Increased risk of meningitis and bacteremia due to Listeria monocytogenes in patients with human immunodeficiency virus infection; Jurado RL et al.; The incidence, demographics, and clinical outcome of infections due to Listeria monocytogenes in individuals infected with the human immunodeficiency virus (HIV) were evaluated by prospective population-based surveillance . During a 2-year study period, 37 cases of invasive listeriosis occurred in metropolitan Atlanta (annual incidence, 0.8 case per 100,000 population) . Seven of these cases occurred in known HIV-infected individuals (19% of all cases); five had an AIDS-defining illness, and the other two had CD4 lymphocyte cell counts of < 200/microL . The estimated incidence of listeriosis among HIV-infected patients in metropolitan Atlanta was 52 cases per 100,000 patients per year, and among patients with AIDS it was 115 cases per 100,000 patients per year, rates 65-145 times higher than those among the general population . HIV-associated cases occurred in adults who were 29-62 years of age and in postnatal infants who were 2 and 6 months of age . Mortality among the HIV-infected group was 29% . L . monocytogenes serotypes 1/2a, 1/2b, and 4b were isolated from the HIV-infected patients . L . monocytogenes is an important opportunistic pathogen in HIV-infected patients.

J Dairy Res, 1993 Aug, 60(3), 421 - 9
Growth of Listeria monocytogenes in Camembert and other soft cheeses at refrigeration temperatures; Back JP et al.; Listeria monocytogenes survived and, under most conditions, multiplied when inoculated directly into the cheese milk of laboratory made Camembert cheeses . The rate and extent of growth was reduced at lower storage temperatures . Significantly higher rates of growth occurred at the surface compared with the centre of the cheeses, and these were probably associated with increased pH and proteolysis at the cheese surface due to the mould ripening process . Similar results were obtained with Camenbert cheeses surface inoculated after manufacture . There was also temperature-dependent growth of List . monocytogenes on a range of inoculated commercially manufactured soft cheeses . Significant growth occurred in Cambazola, French and English Brie, blue and white Lymeswold, French Camembert and Brie with garlic . Little if any growth occurred in blue and white Stilton, Mycella, Chaume and full fat soft cheese with garlic and herbs at the temperatures examined.

Appl Environ Microbiol, 1993 Aug, 59(8), 2743 - 5
Detection of Listeria monocytogenes with a nonisotopic polymerase chain reaction-coupled ligase chain reaction assay; Wiedmann M et al.; A polymerase chain reaction (PCR)-coupled ligase chain reaction (LCR) assay for the specific detection of Listeria monocytogenes (M . Wiedmann, J . Czajka, F . Barany, and C . A . Batt, Appl . Environ . Microbiol . 58:3443-3447, 1992) has been modified for detection of the LCR products with a nonisotopic readout . When a chemiluminescent or a colorimetric substrate for the nonisotopic detection of the LCR products was used, the PCR-coupled LCR gave a sensitivity of 10 CFU of L . monocytogenes . The detection method with the chemiluminescent substrate Lumi-Phos 530 permitted detection of the LCR products in less than 3 h, so that the whole assay can be completed within 10 h.

Appl Environ Microbiol, 1993 Aug, 59(8), 2690 - 7
A ribosomal DNA fragment of Listeria monocytogenes and its use as a genus-specific probe in an aqueous-phase hybridization assay; Emond E et al.; cDNAs were prepared from the total RNA of Listeria monocytogenes ATCC 19118 and used as probes to screen a genomic library of the same strain . Four clones were identified which contained ribosomal DNA fragments . Recombinant DNA from one of them was fractionated and differentially hybridized with the cDNA probes to RNA of L . monocytogenes and Kurthia zopfii . The resulting hybridization pattern revealed an HpaII fragment of 0.8 kb that was specific for the L . monocytogenes strain . The nucleotide sequence of this fragment showed 159 bases of the 3' end of the 16S rRNA gene, 243 bases of the spacer region, and 382 bases of the 5' end of the 23S rRNA gene . In dot blot hybridization assays, the 32P-labeled 784-bp fragment was specific only for Listeria species . Dot blot assays revealed that the 32P-labeled fragment can easily detect > or = 10 pg of total nucleic acids from pure cultures of L . monocytogenes, which corresponds to approximately 300 bacteria . This fragment was also used as a probe in an assay named the heteroduplex nucleic acid (HNA) enzyme-linked immunosorbent assay . In this system, the biotinylated DNA probe is hybridized in the aqueous phase with target RNA molecules and then specific HNAs are captured by HNA-specific antibodies . Captured HNA molecules are revealed with an enzyme conjugate of streptavidin . In a preliminary HNA enzyme-linked immunosorbent assay, the 784-bp fragment maintained its specificity for Listeria spp . and could detect 5 x 10(2) cells in artificially contaminated meat homogenate.

Eur J Immunol, 1993 Aug, 23(8), 2005 - 10
Variable binding affinities of listeriolysin O peptides for the H-2Kd class I molecule; Wipke BT et al.; Previously we used the peptide-binding motif for the murine class I major histocompatibility complex molecule H-2Kd to identify a nonamer peptide of the Listeria monocytogenes listeriolysin (LLO) protein that was recognized by cytotoxic T lymphocytes (CTL) in association with H-2Kd . Eleven nonamer peptides contained in the LLO sequence were synthesized and one, LLO 91-99, proved to be a CTL target . Using peptide binding competition assays with H-2Kd-restricted CTL, we show that 3 out of the 11 LLO peptides, including the CTL epitope, have a high binding affinity for H-2Kd; 2 of 11 peptides have approximately 10-fold lower affinity, while the remaining 6 peptides have no or very low affinity for H-2Kd . Single residue changes were made in the LLO 91-99 peptide and two other LLO peptides to identify non-anchor amino acids that might interfere with peptide binding . In addition, we used the LLO peptides which bound well to H-2Kd to attempt to restimulate a secondary CTL response from L . monocytogenes-primed spleen cells . Only LLO 91-99 was able to induce such a response . Thus only a fraction of nonamer peptides which fit the original binding motif have a high affinity for the H-2Kd class I molecule, and only a fraction of these serve as CTL epitopes.

J Immunol, 1993 Aug 1, 151(3), 1401 - 9
IFN-gamma inhibits the replication of Listeria monocytogenes in hepatocytes; Gregory SH et al.; We previously reported that the bulk of Listeria monocytogenes injected intravenously into mice is taken up in the liver and replicates within the parenchymal cells (hepatocytes) . Although IFN-gamma is known to play an important role in host defenses to listerial infections of the liver, the mechanism(s) that underlies this role remains to be fully delineated . In the initial experiments presented here, we demonstrated the elevated expression of IFN-gamma message in the livers of mice during primary listerial infections . Subsequent experiments showed that the listerial burden of the hepatocyte population was increased significantly in mice administered monoclonal anti-IFN-gamma . Conversely, the administration of murine rIFN-gamma resulted in a marked (2 log10) decrease in the number of hepatocyte-associated Listeria . In vitro, IFN-gamma stimulated the listericidal activity of purified hepatocytes . Infected hepatocytes incubated in the presence of > 0.1 U/ml murine rIFN-gamma exhibited a significant reduction in intracellular Listeria . The elevated antilisterial activity of IFN-gamma-treated hepatocytes in culture was abrogated by the presence of compounds that scavenged or inhibited the production of reactive oxygen intermediates . Taken together, these findings suggest that activation of the oxygen-dependent, antimicrobial activity of hepatocytes may constitute a principal effector function of IFN-gamma in host defenses to listerial infections of the liver.

Immunobiology, 1993 Aug, 188(4-5), 355 - 69
The effect of adult thymectomy on immune response to infection with Listeria monocytogenes in mice; Zhang XY et al.; The role of adult thymus in in vivo immune response to infection with Listeria monocytogenes was examined using euthymic mice and adult-thymectomized (ATx) mice which had been thymectomized 2 weeks before . Numbers of T cells in peritoneal cavities and spleens were increased at 2 weeks after inoculation of L . monocytogenes, whereas such increases of T cells were several times higher in euthymic mice than in ATx mice . In flow-cytometric analysis of peritoneal exudate cells, a significant increase of CD3+CD4-CD8- cells bearing gamma/delta type T cell receptor was noted in euthymic mouse after infection compared to ATx mouse . Neither assay of antigen-specific T cell proliferation nor analysis of cell cycle exhibited any superiority of T cells obtained from euthymic mice to those obtained from ATx mice . These findings suggest that the enlargement of T cell population in euthymic mice is attributed largely to T cells which emigrate from the thymus after inoculation of L . monocytogenes . Moreover, in vivo protective immune response against secondarily challenged L . monocytogenes was achieved more efficiently in euthymic mice than in ATx mice, as shown by the clearance of the bacteria from organs and the survival rate of infected mice . Our results indicate the importance of adult thymus-dependent increase of T cells in eliminating the facultative intracellular bacteria such as L . monocytogenes.

Int J Food Microbiol, 1993 Aug, 19(3), 229 - 37
Incidence of Listeria species in raw and pasteurized milk produced in São Paulo, Brazil; Moura SM et al.; The present study evaluated the incidence of Listeria spp . in raw and pasteurized milk from a Brazilian dairy plant . Ten samples of each type of milk (raw types B and C and pasteurized types B and C) were collected monthly from October 1989 to September 1990 (except in December), comprising 440 samples (110 samples of each type of milk) . The recovery of Listeria spp . was carried out using LPM (lithium chloride phenylethanol moxalactam) and MOX (modified Oxford) agars, after a two-step enrichment procedure in Listeria enrichment broth (LEB) and Fraser broth . Overall, 12.7% of raw milk samples, 0.9% of pasteurized milk samples and 6.8% of total of milk samples were positive for Listeria spp., while 9.5% of raw milk samples, none of the pasteurized milk samples and 4.8% of total milk samples, were positive for Listeria monocytogenes . Raw milk also contained L . innocua (9.5%), L . welshimeri (0.9%) and L . grayi (0.4%) . Pasteurized milk contained only L . innocua (0.9%).

Int J Food Microbiol, 1993 Aug, 19(3), 193 - 205
Occurrence and characteristics of Listeria in foods produced in Northern Ireland; Harvey J et al.; The incidence of L . monocytogenes and other Listeria species was determined for 513 food samples produced in Northern Ireland . Selected L . monocytogenes isolates were typed using MEE and RFLP analysis . The overall incidence of Listeria in the foods examined was 35% (Listeria monocytogenes 18.3%) . The incidence of Listeria and L . monocytogenes in four different food categories (graded I-IV according to decreasing extent of processing) being: I, 11.1% Listeria and 4.7% L . monocytogenes; II, 27.1% Listeria and 12.2% L . monocytogenes; III, 89.1% Listeria and 50% L . monocytogenes and IV, 100% Listeria and 100% L . monocytogenes . Within food categories I and II, the incidence of Listeria on occasions varied markedly between similar products produced by different processors . The most frequently isolated species was L . innocua, followed by L . monocytogenes, L . seeligeri and L . welshimeri . The L . monocytogenes isolates were predominantly serogroup 1 . A modified USDA method was the most productive of four enrichment procedures investigated . Over the one-year duration of the survey, a distinctive Listeria microflora could be discerned in products from certain processors and was confirmed in some cases by MEE and RFLP typing of L . monocytogenes isolates.

Appl Environ Microbiol, 1993 Aug, 59(8), 2698 - 705
Production and characterization of anti-DNA-RNA monoclonal antibodies and their application in Listeria detection; Fliss I et al.; Murine monoclonal antibodies (MAbs) specific for DNA-RNA hybrids were successfully produced with two different heteropolymers as antigens, cDNA-mRNA and phi X174 DNA-RNA heteroduplexes . The former was simpler to prepare . Both had shown similar immunogenicities . Two different immunoglobulin M MAbs were isolated . The 20D3 MAb, generated with the phi X174 DNA-RNA hybrid, showed association constants of 1.05 x 10(12), 2.12 x 10(10), and 1.68 x 10(7) for the antigens phi X174 DNA-RNA, cDNA-mRNA, and poly(rA)-poly(dT), respectively . The 6B5 MAb, obtained with the cDNA-mRNA hybrid, showed association constants of 1.59 x 10(5), 5 x 10(12), and 7.1 x 10(8) for the above-described antigens, respectively . With the 20D3 MAb, an immunoassay was developed for the detection of Listeria DNA-RNA hybrids . In brief, a biotinylated rRNA gene probe specific for the genus Listeria was hybridized with rRNA in the solution phase . The hybrids thus formed were then captured in microtiter plate wells precoated with the purified 20D3 MAb, and the probe-target hybrids were detected with a streptavidin-alkaline phosphatase conjugate . This assay was shown to be specific for the genus Listeria and highly sensitive, allowing the detection of as little as 2.5 pg of target rRNA.

Epidemiol Infect, 1993 Aug, 111(1), 71 - 9
Comparison of multilocus enzyme electrophoresis (MEE), ribotyping, restriction enzyme analysis (REA) and phage typing for typing of Listeria monocytogenes; Norrung B et al.; The discriminatory power of four methods for typing of Listeria monocytogenes was compared . The four methods were multilocus enzyme electrophoresis (MEE), ribotyping, restriction enzyme analysis (REA), and a newly developed Danish phage typing system . Ninety-nine human clinical, food and slaughterhouse isolates of Listeria monocytogenes were typed by each method . The most discriminatory single typing method was phage typing with an overall discriminatory index (DI) of 0.88 followed by REA, MEE and ribotyping with DI-values at 0.87, 0.83 and 0.79 respectively . Considering strains from each of the two predominant O-serotypes alone, serotype 1 was best discriminated by the molecular typing methods, in particular REA, which showed a DI of 0.92 . The serotype 4 strains were best discriminated by phage typing (DI = 0.78) . If two or more typing methods were combined, the combination of REA and MEE were found to be the most discriminatory combination . The DI values were 0.96, 0.74 and 0.90 for serotype 1, 4, and both combined, respectively . Phage typing is a rapid and inexpensive typing method but not as reproducible as the molecular typing methods . It is the most suitable method for mass screening . In situations where results are required to be highly reliable, i.e . when studying the relationships between only a few strains, a single or a combination of molecular typing methods should be used, preferable MEE and REA.

Infect Immun, 1993 Jul, 61(7), 3073 - 5
Detection of a prfA-independent promoter responsible for listeriolysin gene expression in mutant Listeria monocytogenes strains lacking the PrfA regulator; Domann E et al.; Expression of listeriolysin, a major virulence factor of pathogenic Listeria monocytogenes, is positively regulated by the pleiotropic virulence regulator PrfA . In this study, we demonstrate that L . monocytogenes strains lacking the prfA regulator gene produce listeriolysin in small, albeit detectable, amounts when analyzed in a hemolysin assay and by immunoblots with listeriolysin-specific monoclonal antibodies . Transcriptional analysis revealed the existence of a PrfA-independent promoter that was responsible for the hemolytic activity expressed by these strains.

Infect Immun, 1993 Jul, 61(7), 3068 - 72
Multiplication of Listeria monocytogenes in a murine hepatocyte cell line; Wood S et al.; Listeria monocytogenes was shown to invade and multiply in a murine hepatocyte cell line (ATCC TIB73) . Hemolytic and nonhemolytic L . monocytogenes strains exhibited similar abilities to invade hepatocytes, but only hemolytic L . monocytogenes multiplied within this cell line . Microscopic evaluation of monolayers stained with Wright stain demonstrated focal necrosis (plaques) in the hepatocyte monolayers, with large numbers of intracellular listeriae visible within the hepatocytes that lined the margins of these plaques . Murine recombinant interleukin-1 alpha, human recombinant tumor necrosis factor alpha, and murine recombinant gamma interferon did not affect the multiplication of L . monocytogenes in the hepatocytes . These data confirm in vivo observations of the intracellular multiplication of L . monocytogenes in hepatic lesions in infected mice.

Infect Immun, 1993 Jul, 61(7), 2793 - 802
Localization of the ActA polypeptide of Listeria monocytogenes in infected tissue culture cell lines: ActA is not associated with actin "comets"; Niebuhr K et al.; The ActA protein of the gram-positive pathogen Listeria monocytogenes is a 90-kDa polypeptide required for interaction of the bacteria with components of the host cell microfilament system to generate intra- and intercellular movement . To study the localization, distribution, and expression of the ActA polypeptide in L . monocytogenes grown either in broth culture or in infected tissue culture cells, we first isolated ActA by monoclonal antibody-based immunoaffinity chromatography . Polyclonal rabbit antisera raised against purified ActA revealed that ActA was associated with the cell wall and exposed on the surface of the bacteria, readily accessible to ActA antibodies . In contrast, a C-terminally truncated ActA1 polypeptide expressed by the isogenic actA1 mutant was detected only in the supernatant fluids . Immunofluorescence microscopy and electron microscopic studies using immunogold labeling showed that ActA was present on the surface of the bacteria infecting PtK2 and J774 cells at all stages of the infection cycle and was not found to be associated with the actin "tail" of individual bacteria . For the isogenic actA1 mutant strain, which grew as microcolonies within infected cells, only diffuse staining of the secreted ActA1 polypeptide in the host cytoplasm was observed . The ActA polypeptide therefore appears to be required in the initiation of actin accumulation by the bacterium and is apparently not directly involved in the generation of the actin tail . Analysis of strains of several L . monocytogenes serotypes indicated microheterogeneity in the molecular weights of the ActA polypeptides of individual strains and led to the detection of a serotype 3a strain that does not produce ActA.

Infect Immun, 1993 Jul, 61(7), 2786 - 92
An anti-CD3 monoclonal antibody protects mice against a lethal infection with Listeria monocytogenes through induction of endogenous cytokines; Nakane A et al.; Mice were protected against a lethal infection with Listeria monocytogenes when treated with low doses of an anti-CD3 monoclonal antibody (MAb) . Injection of anti-CD3 MAb induced rapid production of endogenous tumor necrosis factor (TNF) in the spleens and endogenous gamma interferon (IFN-gamma) in the bloodstreams and spleens of mice . Administration of anti-Thy1.2 MAb or a combination of anti-CD4 MAb and anti-CD8 MAb resulted in suppression of anti-CD3 MAb-induced endogenous cytokine production and antilisterial resistance . Alternatively, in vivo depletion of anti-CD3 MAb-induced TNF and IFN-gamma by the simultaneous administration of antibodies against TNF and IFN-gamma suppressed anti-CD3 MAb-induced antilisterial resistance . Moreover, injection of anti-complement receptor type 3 (Mac-1, CD11b) resulted in inhibition of anti-CD3 MAb-induced antilisterial resistance . These results suggest that the preventive effect of anti-CD3 MAb might be due to activation of phagocytes by TNF and IFN-gamma induced by stimulating CD4+ T cells and CD8+ T cells with the MAb . Furthermore, treatment with anti-CD3 MAb did not inhibit establishment of acquired resistance against secondary infection with L . monocytogenes.

J Cell Sci, 1993 Jul, 105 ( Pt 3), 699 - 710
Polarized distribution of Listeria monocytogenes surface protein ActA at the site of directional actin assembly; Kocks C et al.; The facultative intracellular pathogen Listeria monocytogenes can infect host tissues by using directional actin assembly to propel itself from one cell into another . The movement is generated by continuous actin assembly from one end of the bacterium into a tail, which is left behind in the cytoplasm . Bacterial actin assembly requires expression of the bacterial gene actA . We have used immunocytochemistry to show that the actA gene product, ActA, is distributed asymmetrically on the bacterial surface: it is not expressed at one pole and is increasingly concentrated towards the other . This polarized distribution of ActA was linked to bacterial division: ActA protein was not, or only faintly, expressed at the pole that had been formed during the previous division . On intracellular bacteria ActA was expressed at the site of actin assembly, suggesting that ActA may be involved in actin filament nucleation off the bacterial surface . We predict that the asymmetrical distribution of this protein is required for the ability of intracellular Listeria to move in the direction of the non-ActA expressing pole.

J AOAC Int, 1993 Jul-Aug, 76(4), 831 - 8
Comparison of MICRO-ID Listeria method with conventional biochemical methods for identification of Listeria isolated from food and environmental samples: collaborative study; Higgins DL et al.; Fourteen laboratories participated in a collaborative study to evaluate the ability of the MICRO-ID Listeria identification method to correctly identify Listeria isolated from food and environmental sources . Each collaborator received 60 isolates consisting of 51 Listeria and 9 non-Listeria cultures . All isolates were identified by conventional biochemical analyses in the principal laboratory . Cultures were checked for purity by Gram staining and examined for oxidase and catalase activities . Only Gram positive, oxidase negative, catalase positive cultures were tested with the method . Colonies from trypticase soy agar with 0.6% yeast extract were suspended in 4.6 mL physiological saline to a MacFarland No . 1 turbidity standard and used to inoculate the test strip . In addition, the hemolytic reaction of each isolate was determined by using the Christie-Atkins-Munch-Peterson (CAMP) test and by stabbing sheep blood agar . Identification of Listeria is based on the octal code obtained from the strip and the hemolytic reaction of the isolate . The MICRO-ID Listeria method agreed with conventinal biochemical identification for 98.0% of L . monocytogenes, 77.1% of L . seeligeri, 90.0% of L . ivanovii, 96.4% of L . grayi/L . murrayi, 73.9% of L . welshimeri, and 100% of L . innocua isolates . A large percentage of errors in identification of the L . seeligeri and L . ivanovii cultures was caused by inaccurate reading of the CAMP and hemolysis tests rather than errors in the test strip . The method was adopted first action by AOAC International.

J AOAC Int, 1993 Jul-Aug, 76(4), 822 - 30
AutoMicrobic System for biochemical identification of Listeria species isolated from foods: collaborative study; Harris L et al.; A collaborative study was conducted to evaluate the performance of the AutoMicrobic System Gram-Positive Identification (GPI) and Gram-Negative Identification (GNI) test kits to biochemically characterize Listeria spp . Thirteen laboratories each tested 97 food and environmental isolates, representing the 7 species of Listeria, as well as 11 additional genera of Gram-positive rods . Each collaborator inoculated both a GPI and a GNI card with a pure culture of each organism . The AutoMicrobic System identified the isolates and printed out the biochemical results . The GPI card is used to obtain a species identification and a mannitol reaction result, and the GNI card is used to obtain rhamnose and xylose reaction results . Organisms are classified into species groups and can be further distinguished on the basis of hemolysis or nitrate reduction tests . The AutoMicrobic System method correctly classified 90.8% of the Listeria spp . isolates and 100% of the non-Listeria isolates . The AutoMicrobic System method was adopted first action by AOAC International for the biochemical characterization of Listeria spp . isolated from food and environmental sources.

Biophys J, 1993 Jul, 65(1), 316 - 24
Cellular motions and thermal fluctuations: the Brownian ratchet; Peskin CS et al.; We present here a model for how chemical reactions generate protrusive forces by rectifying Brownian motion . This sort of energy transduction drives a number of intracellular processes, including filopodial protrusion, propulsion of the bacterium Listeria, and protein translocation.

Appl Environ Microbiol, 1993 Jul, 59(7), 2082 - 6
Sodium chloride, potassium chloride, and virulence in Listeria monocytogenes; Myers ER et al.; Virulence, as determined in a mouse model, and the virulence factor activities of catalase, superoxide dismutase, and listeriolysin O were examined in a parental strain (10403S) and in a nonhemolytic mutant strain (DP-L224) of Listeria monocytogenes . The cells were propagated in media containing various concentrations of sodium chloride or potassium chloride . Strains 10403S and DP-L224 exhibited significant increases in catalase activity and listeriolysin O activity when grown in medium containing either salt at 428 mM . The superoxide dismutase activities for both strains increased when they were grown in medium containing either salt . The superoxide dismutase activity was significantly increased only when cells were propagated in medium containing no salt compared with that when they were propagated in medium containing either salt at 1,112 mM . In addition, the listeriolysin O activity was highest for cells propagated in medium containing KCl at 428 mM, while the activity was significantly less for cells propagated in medium containing NaCl at an equal concentration . Virulence was examined in mouse livers and spleens after intravenous infection, and approximate 50% lethal doses were determined after intragastric and intraperitoneal infection . Each method of infection indicated that listeriolysin O is required for virulence, while growth in salt-containing medium or the production of higher levels of catalase, superoxide dismutase, and listeriolysin O do not appear to enhance the virulence of L . monocytogenes.

Arch Int Pharmacodyn Ther, 1993 Jul-Aug, 324, 114 - 23
Effects of buspirone on the resistance, development and passive transfer of immunity to Listeria monocytogenes in mice submitted to stress; Freire-Garabal M et al.; Mice exposed to a chronic auditory stressor and treated chronically with buspirone (1 mg/kg) showed a reduction in stress-induced suppression of the resistance and development of immunity to Listeria monocytogenes . Attempts to passively transfer immunity with spleen cells were also performed . Stressed, immunized mice had a reduced capacity to transfer immunity passively to nonimmunized mice and buspirone was found to partially suppress this inhibitory effect of stress.

Vet Microbiol, 1993 Jul, 36(1-2), 185 - 9
Comparison of a cold enrichment method and the IDF method for isolation of Listeria monocytogenes from animal autopsy material; Eld K et al.; The method most often used in Sweden for isolation of Listeria monocytogenes from animal autopsy material is a cold enrichment method . This method is very slow . The International Dairy Federation (IDF) has recently presented a method for detection of L . monocytogenes in milk and milk products that is complete in one week . During a two year period 69 specimens from dead animals with suspected listeriosis were examined for L . monocytogenes in parallel analyses with both the cold enrichment method and the IDF method . Samples derived from different autopsy material representing a variety of animals . L . monocytogenes was isolated in 27.5% of the samples with the IDF method but only in 4.3% with the cold enrichment method . It is concluded that the IDF method was more sensitive than the cold enrichment method.

J Hepatol, 1993 Jul, 18(3), 284 - 9
Listeria monocytogenes hepatitis in a liver transplant recipient: a case report and review of the literature; Bourgeois N et al.; Listeria is an uncommon cause of hepatitis in adults . We report the case of a liver transplant recipient who presented with a clinical picture of acute hepatitis, 8 months after grafting . Blood cultures yielded Listeria monocytogenes . The patient made a full clinical recovery after adequate antimicrobial therapy (ampicillin and gentamicin intravenously for 4 weeks) . Hepatitis was attributed to the Listeria infection . We believe this is the first reported case of Listeria hepatitis in an organ transplant recipient.

Immunol Lett, 1993 Jul, 37(1), 73 - 6
Production of interleukin 8 (IL-8) by cord blood mononuclear cells induced by Listeria monocytogenes; Serushago B et al.; The defective ability of human newborns to mobilize phagocytes to the site of infection led us to examine the ability of cord blood mononuclear cells to secrete interleukin-8, a major neutrophil chemotactic factor, in response to stimulation with Listeria monocytogenes . Adult or cord blood mononuclear cells were incubated with L . monocytogenes for varying lengths of time, and IL-8 was measured in the culture supernatants by the enzyme-linked immunosorbent assay (ELISA) . Spontaneous IL-8 secretion by unstimulated cells was undetectable or at the minimal detection limit of the assay . By 24 h of cell incubation with L . monocytogenes, newborn cells produced as much IL-8 as adult cells did (300 +/- 113 versus 269 +/- 189 ng/ml, respectively) . Over the next 2-4 days, IL-8 output by adult cells was slightly higher than that by newborn cells, but the difference was not statistically significant . The in vitro results suggested that newborns are as able as adults to produce IL-8, although they are defective in mobilizing neutrophils, the IL-8 target cells, to the site of infection.

Z Geburtshilfe Perinatol, 1993 Jul-Aug, 197(4), 179 - 83
{Effect of Listeria on contractibility of human uterine muscle}; Lechner W et al.; In Austria the prevalence of listeriosis is 2.6 cases per million inhabitants yearly, hence rather rarely the cause of spontaneous abortion or premature birth . On the other hand, Listeria monocytogenes is found in 1% of the asymptomatic population as a component of stool flora . Since the cause of premature labour contractions remains unclear in about half of all cases, we examined 29 listeria strains for their ability to cause myometrial contraction by direct contact using an in-vitro uterine strip-model . Seven of nine L . monocytogenes strains were able to cause contractions; contractions were not inducible by an nonhaemolytic mutane (SLCC 53, avirulent) nor by a rough strain (SLCC 5779, only slightly virulent) . Three of six L . ivanovii isolates also exhibited the ability to induce contractions . None of the apathogenic species (L . innocua, L . seeligeri, L . welshimeri, L . grayi and L . murrayi) was capable of activating contractions in our in-vitro model . Only L . monocytogenes and L . ivanovii cause conjunctivitis after being dropped in rabbit's eyes (positive Anton Test) . The influence of listeria on uterine activity as found in our in-vitro model thus correlates with the classical pathogenicity test . We consider these in-vitro results as an additional argument to oppose the presence of L . monocytogenes in ready-to-eat foods.

Lett Appl Microbiol, 1993 Jul, 17(1), 14 - 6
The effect of pH and temperature on haemolysin production by Listeria species; Khan SA et al.; The ability of three strains of Listeria monocytogenes NCTC 7973, serovar 1/2a, NCTC 5124m serovar 4a, C-274 serovar 4b and one strain of L . seeligeri (SLCC 3954) to grow in TPB (Tryptose phosphate agar) at pH values between 5-9 and produce haemolysin has been investigated at two incubation temperatures . The minimum and maximum pH values at which haemolysin was detected were 5 and 9 respectively, at 20 degrees and 32 degrees C.

Epidemiol Infect, 1993 Jun, 110(3), 543 - 51
The contamination of paté by Listeria monocytogenes in England and Wales in 1989 and 1990; Gilbert RJ et al.; In July 1989, 1834 samples of pate (of which 1698 were from retail displays) were examined by the PHLS for the presence of Listeria monocytogenes . The survey was repeated in July 1990, when 626 pate samples on retail sale were examined . Between the two surveys there was a marked reduction in the proportions of pates contaminated (10% in 1989 and 4% in 1990) and in the numbers of samples from which > 10(3) L . monocytogenes/g were recovered . The higher rate of contamination detected in 1989 was largely due to pate from a single manufacturer . In both surveys, pate sold as loose slices had higher rates of contamination than those prepackaged . Temperature control had improved between the two surveys where 65% of samples in 1989 and 83% in 1990 were stored at < or = 7 degrees C . Although contamination occurred at almost all temperatures, L . monocytogenes was both quantitatively and qualitatively more common in samples stored at > 7 degrees C . The majority of pates had unexpired shelf lives of between 0 and 3 weeks . Although contamination occurred throughout the shelf life of these products, the proportion of samples where L . monocytogenes was recovered was higher in pates with expired sell by dates . There was an association between high total viable counts and the presence of L . monocytogenes . Likely routes of contamination of pate together with possible preventive measured are discussed.

Proc Natl Acad Sci U S A, 1993 Jun 1, 90(11), 5034 - 8
Modulation of the interaction between G-actin and thymosin beta 4 by the ATP/ADP ratio: possible implication in the regulation of actin dynamics; Carlier MF et al.; The interaction of G-actin with thymosin beta 4 (T beta 4), the major G-actin-sequestering protein in motile and proliferating cells, has been analyzed in vitro . T beta 4 is found to have a 50-fold higher affinity for MgATP-actin than for MgADP-actin . These results imply that in resting platelets and neutrophils, actin is sequestered by T beta 4 as MgATP-G-actin . Kinetic experiments and theoretical calculations demonstrate that this ATP/ADP dependence of T beta 4 affinity for G-actin can generate a mechanism of desequestration of G-actin by ADP, in the presence of physiological concentrations of T beta 4 (approximately 0.1 mM) . The desequestration of G-actin by ADP is kinetically enhanced by profilin, which accelerates the dissociation of ATP from G-actin . Whether a local drop in the ATP/ADP ratio can allow local, transient desequestration and polymerization of actin either close to the plasma membrane, following platelet or neutrophil stimulation, or behind the Listeria bacterium in the host cell, while the surrounding cytoplasm contains sequestered ATP-G-actin, is an open issue raised by the present work.

J Infect Dis, 1993 Jun, 167(6), 1364 - 71
Listeria monocytogenes-induced interferon-gamma primes the host for production of tumor necrosis factor and interferon-alpha/beta; Havell EA; Mice acquired an enhanced capacity for the production of tumor necrosis factor (TNF) and the interferons (IFN)-alpha, and -beta shortly after intravenous injection of viable Listeria monocytogenes . By the end of the first day of a sublethal infection, mice were primed to produce 100-1000 times more endotoxin-induced serum TNF than is produced by normal mice . Acquisition of the augmented capacity for TNF production was due to L . monocytogenes-induced IFN-gamma . IFN-gamma also primed infected mice for IFN-alpha/beta production . However, in addition to IFN-gamma, other L . monocytogenes-induced mechanisms endowed the host with an enhanced potential for the production of IFN-alpha/beta . Antibody-mediated depletion of various cell types in vivo revealed that CD8+ cells and NK cells are required for the production of L . monocytogenes-induced IFN-gamma during the first day of listeriosis.

Infect Immun, 1993 Jun, 61(6), 2626 - 31
The cellular source of interleukin-6 during Listeria infection; Liu Z et al.; The cellular source of interleukin-6 (IL-6) during infection of mice with Listeria monocytogenes was investigated both in vitro and in vivo . Peritoneal cells taken at intervals from infected mice and cultured in vitro without added stimulus produced high titers of IL-6 peaking 2 days postinfection in a time course similar to that observed in vivo . Adherent cells with the morphology of macrophages were a major source of this IL-6 . Spleen cells similarly harvested at intervals and cultured with heat-killed Listeria or heat-killed Brucella organisms as specific and nonspecific stimuli, respectively, showed two distinct IL-6 responses: (i) an early-phase response up to 5 days after infection when IL-6 production was elicited by either a specific or nonspecific stimulus, and when depletion of T cells had no effect, and (ii) a later response 7 to 10 days after infection when very high levels of IL-6 were produced in response to a specific stimulus . This response was lost when T cells were depleted in vitro or in vivo or in spleen cell cultures from mice with severe combined immunodeficiency . However, studies in vivo failed to show an important role for T cells governing serum IL-6 . We conclude that most of IL-6 detected in vivo is produced by nonlymphocytes . Whether IL-6 produced by T lymphocytes in local foci of infection has any role in resolution of that infection is unknown.

Rinsho Shinkeigaku, 1993 Jun, 33(6), 637 - 41
{A case of Listeria rhombencephalitis with a secondary vasculitis suggested by MRI}; Tokonami F et al.; We reported a rare case of Listeria rhombencephalitis with meningitis . A 48-year-old healthy man suddenly experienced high fever and headache, then he had lower cranial nerve's palsies and mental dysfunction developed during one week period . On admission, his temperature was 38 degrees C . He was slightly delirious and euphoric . He had nuchal rigidity, mild paresthesia over his left cheek to left upper lip, a right sixth nerve palsy, dysphagia, hiccup, nasal voice and left cerebellar ataxia . His tongue deviated toward the right side on protrusion . A CSF culture grew Listeria monocytogenes . Intravenous antibiotic therapy (PIPC, minocycline hydrochloride) produced improvement in one month except for mild paresthesia and dysphagia . He almost recovered after 7 months of illness . Brain MRI on T2 weighted image demonstrated multiple small ischemic lesions in the left lateral medulla, upper pontine tegmentum in the right side, and pontine tegmentum in the left side . These lesions enhanced by Gd . were assumed to be due to the secondary vasculitis . Listeria rhombencephalitis is extremely rare in human beings . To our knowledge only thirteen cases have been reported . In seven cases, post-mortem pathological findings confirmed necrotizing angitis in brainstem . Clinical aspects of Listeria rhombencephalitis were discussed, and the entity of this disease should be considered as a treatable cause of acute progressive brainstem meningoencephalitis.

J Leukoc Biol, 1993 Jun, 53(6), 651 - 7
Splenic macrophage activation and functions in amyloid enhancing factor-induced secondary amyloidosis . Study of phagocytosis, killing, respiratory burst, and MHC class II surface expression; Reid C et al.; Secondary amyloidosis is a systemic disease characterized by the extracellular tissue deposition of insoluble fibrillar amyloid A protein . Aberrant metabolism of serum amyloid A protein by reticuloendothelial cells is thought to result in the accumulation of fibrils within the tissue . Treatment of mice with amyloid-enhancing factor (AEF) in conjunction with an inflammatory stimulus (i.e., AgNO3) induced amyloid deposition within 48-72 h . The activation state of a macrophage largely defines its enzymatic capabilities . In the studies reported here, we examined the effect of AEF on spleen macrophage activation using both functional and phenotypic assays . We found that while AEF in the presence or absence of AgNO3 has no apparent effect on the ability of spleen and liver macrophages to phagocytose or kill Listeria monocytogenes, it appears to block enhanced respiratory burst function (as measured by O2- production) observed with AgNO3 alone . AEF therefore seems capable of inhibiting certain macrophage activation-associated functions while not affecting others . Our activation phenotype studies, using surface Ia expression, reveal that AEF blocks the increase in number of splenic macrophages expressing Ia seen with AgNO3 alone . Treatment with interferon-gamma was found to restore decreased Ia expression in animals given AEF+AgNO3 but did not prevent amyloid A fibril deposition.

Infect Immun, 1993 Jun, 61(6), 2537 - 44
Regulation of the prfA transcriptional activator of Listeria monocytogenes: multiple promoter elements contribute to intracellular growth and cell-to-cell spread; Freitag NE et al.; The prfA gene product is a transcriptional activator of Listeria monocytogenes determinants of pathogenicity . In this study, we provide direct evidence that the PrfA protein is a site-specific DNA-binding protein . Additionally, we describe the characterization of two classes of L . monocytogenes mutants which contain transposon insertions either in the prfA structural gene (exemplified by strain DP-L1075) or within the prfA promoter region (exemplified by strain DP-L973) . Both mutants are completely avirulent and secrete greatly reduced levels of listeriolysin O and phosphatidylinositol-specific phospholipase C, and both are fully complemented by the introduction of prfA on a multicopy plasmid . The behaviors of the two mutants differ markedly within cultured macrophages . Following infection, no cytoplasmic growth was observed for DP-L1075 whereas DP-L973 escaped from the phagosome and grew in the cell cytoplasm . However, DP-L973 was defective in nucleation of actin filaments and spread to adjacent cells . Transcription of prfA in DP-L973 was directed from a single, previously unidentified promoter (prfAp2) located close to the prfA initiation codon . This promoter is therefore capable of providing sufficient prfA expression for escape from the host cell vacuole but is insufficient for wild-type levels of bacterially induced actin polymerization and cell-to-cell spread . Transcription directed from both prfAp1 and prfAp2 promoters was increased in the absence of a functional prfA gene product, suggesting that PrfA protein contributes to down-regulating its own expression.

Mol Cell Probes, 1993 Jun, 7(3), 199 - 207
A combined modified reverse dot-blot and nested PCR assay for the specific non-radioactive detection of Listeria monocytogenes; Bsat N et al.; A modified reverse dot-blot assay was developed and used in combination with a nested PCR amplification of hly A for the specific detection of Listeria monocytogenes . The deoxynucleotides and digoxygenin-11-dUTP concentrations in the PCR were optimized for maximal sensitivity and economy . For the dot-blot hybridization, digoxygenin-labelled PCR products were directly spotted on nylon membrane-bound poly-dT tailed capture probes and the signal detection was either colorimetric or chemiluminescent . With crude cell lysates, the total assay could be completed in about 6 h with a detection limit between 2 and 25 colony forming units (cfu) per PCR . The assay was then tested for its applicability to environmental sampling of artificially contaminated aluminum surfaces . For environmental sampling, the assay requires an additional overnight enrichment step and has a sensitivity corresponding to 5 cfu per 25 cm2 of inoculated surface.

Clin Invest Med, 1993 Jun, 16(3), 219 - 25
An animal model of foodborne Listeria monocytogenes virulence: effect of alterations in local and systemic immunity on invasive infection; Schlech WF 3rd; Development of foodborne listeriosis is dependent on an interplay between organism-specific virulence factors and host susceptibility . Gastric inoculation of Sprague-Dawley rats was used as a model to explore Listeria-specific virulence and host susceptibility . Gastric inoculation leads to invasive infection with "smooth" hemolytic Listeria monocytogenes but not with "rough" L . monocytogenes or other Listeria species . Infection is dose-dependent with an ID50 of 10(6) virulent Listeria monocytogenes . In these experiments, the ID50 was not altered by pregnancy but invasive infection led to abnormal reproductive outcomes including stillbirth and reabsorption of fetuses . Immunosuppression by cyclosporin A led to more prolonged infection but did not alter the ID50 . Manipulation of intestinal flora with antibiotics suggested increased rates of infection with antibiotics that decreased anaerobic flora . Growth of virulent Listeria in milk at varying temperatures did not enhance virulence . No differences in invasive potential of flagellated vs . non-flagellated L . monocytogenes were found . Oral models of invasive Listeria monocytogenes infection provide a useful tool for studying organism virulence and host susceptibility.

Int J Food Microbiol, 1993 Jun 1, 18(4), 289 - 303
Distribution of Listeria spp . in confectioners' pastries from western France: comparison of enrichment methods; Ferron P et al.; Three hundred samples of pastry from 100 different suppliers in western France, including butter-cream, whipped dairy cream and custard filled cakes from each supplier, were collected and tested for the occurrence of Listeria spp . in 25 g samples . Listeria spp . were detected in 21.7% of he samples: Listeria monocytogenes in 13.7%, Listeria innocua in 10% and Listeria seeligeri in 2.3% . Thirteen samples were contaminated with two species simultaneously . The frequency of contaminated samples was not related to the composition of the pastry filling used, but it seemed to increase with the number of aerobic contaminant microorganisms in the dairy cream-based samples . The contamination rate was dependent on the place of manufacture . The numbers of Listeria spp . and Listeria monocytogenes were estimated on positive samples at the 25 g level as follows: < 0.3/g, Listeria spp . in 47 samples, L monocytogenes in 27; 0.3-30/g, Listeria spp . in 13, L . monocytogenes in nine; 30-300/g, L . monocytogenes in one; 300-3000/g; L . monocytogenes in three; 700,000/g, L . monocytogenes in one . Various detection methods were tested, including two enrichments broths tested in parallel: a modified LEB broth using 10 mg/l acriflavine-HCl and the UVM 1 broth, with incubation at 30 degrees C and streaking onto PALCAM agar . The enrichment procedures were: (a) primary enrichment of 25 g sample and plating after 48 h and 7 days; (b) secondary enrichment by subculturing the primary enrichment broths incubated for 24 h and 6 days, into fresh enrichment broth, then plating after 24 h incubation; (c) pre-enrichment of 25 g sample for 24 h in the basal enrichment broths without inhibitors, followed by subculturing in complete broths which were plated after 24 h and 6 days incubation . In all cases, UVM performed better than the LEB broth . It was unnecessary to extend the primary enrichment period beyond 48 h . Secondary enrichments inoculated from 24-h incubated primary enrichments gave a slightly better isolation rate than primary enrichments . Secondary enrichments made from 6-day incubated primary enrichments gave no additional advantage . The pre-enrichment procedure had an efficiency higher than that obtained by primary enrichment.

J Clin Microbiol, 1993 Jun, 31(6), 1537 - 40
Kinetics of antibody production against listeriolysin O in sheep with listeriosis; Lhopital S et al.; The kinetics of antibody production against listeriolysin O (LLO), a major virulence factor of the intracellular bacterial pathogen Listeria monocytogenes, was studied by dot blot analysis with highly purified LLO during oral infection of sheep . Specific antibodies appeared as soon as day 9 of an oral infection and peaked by day 20 of infection; specific antibody levels then remained almost stable for at least 4 months . A subclinical infecting dose (approximately 10(6) viable bacteria) was capable of eliciting a significant antibody response to LLO, almost at the same level as that observed with a high-dose oral challenge (approximately 10(10)) . Antibodies to LLO were mostly constituted by immunoglobulin G (IgG), since an IgA response was not detectable and only a transient and inconstant IgM response was observed between day 9 and day 20 of an oral infection . These results show that antibodies to LLO are constantly produced during oral infection even with a low infecting dose, thus confirming that LLO is highly immunogenic . Detection of antibodies to LLO can therefore be used to detect sheep that have been previously exposed to L . monocytogenes.

Immunology, 1993 Jun, 79(2), 196 - 202
Increase of Thy-1 antigen on the thymocytes accompanied with their augmented adhesion capacity to thymic epithelial cells in the mice infected with Listeria monocytogenes; Maeda Y et al.; It becomes increasingly clear that adhesion systems such as CD2/LFA-3 (lymphocyte function-associated antigen-3), LFA-1/ICAM-1 (intercellular adhesion molecule-1) and Thy-1/putative Thy-1 ligand participate in the association between murine thymocytes and thymic epithelial cells . In the present study, thymocytes showed an increase in surface Thy-1 levels in mice infected with Listeria monocytogenes, but no significant changes in the levels of CD2 or LFA-1 . No alteration was found either in the ratio of CD3high/CD3low/CD3- or in that of CD4/CD8 subsets in these thymocytes compared with uninfected control thymocytes which excluded the possibility of enrichment of 'cortical thymocytes' with Thy-1high/CD3low/CD4+ CD8+ in the thymocyte population of infected mice . Moreover such Thy-1high thymocytes exhibited a highly augmented ability of adhesion to a thymic epithelial cell line due to the increase of surface Thy-1 antigens as an adhesion molecule . At such intervals after infection, the total number of thymocytes was found to be reduced . These results suggest that the expression level of surface Thy-1 on thymocytes is regulated in response to in vivo stimulation and may play a role in the intrathymic development of thymocytes by affecting the adhesion of thymocytes with thymic stromal cells . The implication of the enhanced ability of adhesion in the decrease in the number of thymocytes is discussed.

Infect Immun, 1993 Jun, 61(6), 2703 - 7
Leukocyte-mediated lysis of infected hepatocytes during listeriosis occurs in mice depleted of NK cells or CD4+ CD8+ Thy1.2+ T cells; Conlan JW et al.; An important early component of defense against listeriosis in mice is the lysis of infected hepatocytes by leukocytes that accumulate at foci of infection in the liver . This serves to release Listeria monocytogenes from permissive parenchymal cells for ingestion and inactivation by phagocytic cells . It is shown here that lysis of infected hepatocytes is as extensive in mice depleted of T cells or NK cells as it is in control mice . This supports the original interpretation that hepatocyte lysis is mediated mainly by neutrophils.

Clin Exp Immunol, 1993 Jun, 92(3), 473 - 6
Failure of FK 506 to suppress the T cell-mediated immunity of mice to Listeria monocytogenes; Wagner JA et al.; Listeria monocytogenes belongs to the group of intracellular bacteria, which means that they reside and multiply within host cells . The protective immunity against such an infection is mediated by cellular immune mechanisms . Whereas the CD8+ T cell population plays a major role therein, the CD4+ T cells are held to be of minor importance in this defence system . Consequently, one can understand that immune suppression with FK 506 which acts primarily on this latter T cell subset, does not interfere with protective immunity of mice infected with L . monocytogenes . We have demonstrated that the drug blocks neither curing of primary infection, nor formation of granulomas, nor induction of cell populations capable of mediating adoptive transfer of immunity, nor expression of pre-existing immunity.

Appl Environ Microbiol, 1993 May, 59(5), 1289 - 93
Detection of Listeria monocytogenes in cheese with the magnetic immuno-polymerase chain reaction assay; Fluit AC et al.; A new detection system, the magnetic immuno-polymerase chain reaction (PCR) assay (MIPA) has been developed to detect Listeria monocytogenes in food . This method separates Listeria cells from PCR-inhibitory factors present in enrichment broths containing food samples by using magnetic beads coated with specific monoclonal antibodies (MAbs) . The separated bacteria were lysed, and the supernatant containing the bacterial DNA was subjected to the PCR . Detection of L . monocytogenes in three naturally contaminated cheese samples with two different MAbs and PCR primers specific for the gene encoding the delayed-hypersensitivity factor showed that with MAb 55 all three samples were positive whereas with MAb A two samples were positive . A further improvement of the method was obtained by using a PCR step based on the listeriolysin O gene . A MIPA employing MAb 55 and the listeriolysin O gene primer set detected L . monocytogenes after 24 h of culture in Listeria Enrichment Broth samples from Port Salut artificially contaminated with 40 CFU/25 g . We could detect 1 CFU of L . monocytogenes per g of cheese after a second enrichment for 24 h in Fraser broth . The analysis time including both enrichments is approximately 55 h.

Immunology, 1993 May, 79(1), 82 - 8
Murine complement receptor gene expression: Cr2 gene transcripts are depressed during a high dose microbial challenge; Tan SS et al.; The murine Cr2 gene encodes mRNA that produce two protein products predicted to be approximately 145,000 M(r) (Cr2-145) and 190,000 M(r) (Cr2-190) . All cells examined which express the Cr2 gene produce transcripts encoding both the Cr2-145 and Cr2-190 proteins: both transcripts are constitutively expressed by mature B cells . To determine if Cr2 expression could be altered by activating splenic B cells, splenic cultures were incubated with lipopolysaccharide (LPS) and cell surface Ig chains were cross-linked with anti-mu . In the presence of LPS and anti-mu both Cr2 and Oct-2 transcripts were diminished while the control beta-actin transcript levels remained unchanged . However, when LPS alone was added, only the Cr2 transcript levels were diminished . To test if these findings could be reproduced in vivo, animals were provided with a peritoneal injection of either Escherichia coli or Listeria monocytogenes and transcript levels analysed . The quantities of both Cr2 transcripts, as well as those encoding Oct-2, were substantially reduced in splenocytes and peripheral lymphatic tissues obtained from these infected mice while those encoding the mouse Crry protein, the B-cell marker CD19 and beta-actin remained unchanged . These data suggest that when confronted with a major bacterial infection, murine B cells respond by shutting down synthesis of transcripts encoding the Cr2 and Oct-2 gene products.

Clin Infect Dis, 1993 May, 16(5), 689 - 702
Brainstem encephalitis (rhombencephalitis) due to Listeria monocytogenes: case report and review; Armstrong RW et al.; Listerial brainstem encephalitis is a rare disease . Only 62 cases have been reported previously; all were in adults, only 8% of whom were immunosuppressed . The disease has a characteristic biphasic course: a nonspecific prodrome of headache, nausea or vomiting, and fever lasting for several days is followed by progressive asymmetrical cranial-nerve palsies, cerebellar signs, hemiparesis or hypesthesia, and impairment of consciousness . Neck stiffness was initially present in only 55% of the cases described thus far . Studies of cerebrospinal fluid often revealed only mild abnormalities . Cultures of cerebrospinal fluid and blood were positive in 41% and 61% of cases, respectively . Respiratory failure occurred in 41% of cases . Initial computed tomography of the brain often gave normal results; magnetic resonance imaging better demonstrated brainstem abnormalities . Overall mortality was 51% . All untreated patients died . When treatment with ampicillin or penicillin was initiated early, the rate of survival was > 70%; however, neurological sequelae developed in 61% of survivors.

J Infect, 1993 May, 26(3), 301 - 3
Neonatal cross-infection with Listeria monocytogenes; Pejaver RK et al.; Transmission of Listeria monocytogenes by food continues to cause concern . Even so, this is not the only means of transmission and neonatal hospital-acquired infection has been well recorded . We report here two cases of perinatal listeriosis one of which was likely to have been due to cross-contamination in a Special Care Baby Unit (SCBU) with equipment acting as the vehicle.

J Leukoc Biol, 1993 May, 53(5), 525 - 31
Cytokine mRNA expression in livers of mice infected with Listeria monocytogenes; Wagner RD et al.; Temporally distinct groups of cytokine expression was observed by reverse transcription-polymerase chain reaction assay, in situ hybridization, and immunohistochemistry in the livers of Listeria monocytogenes-infected mice . One group consisted of interferon-gamma (IFN-gamma), tumor necrosis factor alpha (TNF-alpha), and interleukin-10 (IL-10), for which mRNAs were induced within 1 day after challenge . A second group consisted of IL-2 and IL-4, for which mRNA was strongly expressed at 1 day but then suppressed at 3 days into the infection . Granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-1 alpha, and IL-6 mRNA constituted a third group, which was increased at 3 days after challenge . Distributions of cytokine mRNA-expressing cells in the liver was observed by in situ hybridization . Cells expressing TNF-alpha and IL-1 alpha mRNA were present throughout liver granulomas, whereas cells that expressed IFN-gamma mRNA were observed mostly along the periphery of granulomas . Cells expressing IL-2, IL-4, IL-6, IL-10, and GM-CSF mRNA were distributed principally in the hepatic sinuses . Cells expressing IL-10 mRNA increased in number early in the infection when L . monocytogenes was multiplying in the liver . We conclude that cytokine mRNA expression during the early phases of L . monocytogenes infection in mice is temporally regulated and that IFN-gamma, TNF-alpha, and IL-1 alpha are expressed by cells associated with hepatic granulomas.

Int J Food Microbiol, 1993 May, 18(3), 223 - 32
Fate of Listeria monocytogenes in raw and cooked ground beef with meat processing additives; Harmayani E et al.; The effect of sodium lactate (1.8% w/w), sodium erythorbate (0.1% w/w), kappa-carrageenan (1% w/w), and the alginate meat binder (0.4% w/w, sodium alginate; 0.6% w/w lactic acid; and 0.075% w/w calcium carbonate) on Listeria monocytogenes survival and growth was determined in raw and cooked ground beef stored aerobically at 4 degrees C . There was no significant (P > 0.05) increase in numbers of L . monocytogenes during storage of raw ground beef . However, L . monocytogenes numbers were generally lower in treatments with sodium lactate, and higher in sodium erythorbate compared to controls and meat with other additives . Increases in total aerobic plate counts were less pronounced in raw meat formulated with sodium lactate and alginate meat binder than with other additives . Cooking meat with initial inoculum levels of 6.52 to 7.03 L . monocytogenes log CFU/g to 65 degrees C resulted in lower destruction (0.56 and 1.18 log CFU/g) in samples with added alginate meat binder and kappa-carrageenan, respectively, compared to the control . Survivors (2.11-3.73 log CFU/g) decreased initially and then increased slightly, but not significantly (P > 0.05), during storage (4 degrees C, 6 days) of the cooked products.

J Med Microbiol, 1993 May, 38(5), 322 - 7
Typing of Listeria spp . by random amplified polymorphic DNA (RAPD) analysis; MacGowan AP et al.; Random amplified polymorphic DNA (RAPD) analysis, a variation of the polymerase chain reaction (PCR) in which a single primer is used, was evaluated for use as a simple and reliable method with which to type Listeria spp . Representatives of six species of Listeria were studied . Five isolates of L . innocua and four isolates of L . seeligeri were all distinguishable from one another, but the four isolates of L . ivanovii tested, although distinguishable from other Listeria spp., were not differentiated . Among L . monocytogenes serovars 1/2a (eight isolates), 1/2b (eight isolates) and 4b (10 isolates), at least six, three and six RAPD patterns were observed, respectively . Fourteen neonatal cross-infection sets of L . monocytogenes isolates, shown to be indistinguishable by serotyping and phage typing, were examined with three different primers . With one primer, three of the sets were shown to consist of closely related, but distinguishable, strains . In the other 11 cases, each set of strains was indistinguishable with all three primers . These preliminary data indicate that RAPD analysis has promise as a method for typing Listeria spp.

J Appl Bacteriol, 1993 May, 74(5), 515 - 20
Acetic, lactic and citric acids and pH inhibition of Listeria monocytogenes Scott A and the effect on intracellular pH; Young KM et al.; The effects of acetic, lactic and citric acids and pH on the growth and intracellular pH (pHin) of Listeria monocytogenes Scott A were documented and compared for total acid concentrations ranging from 50 mmol ml-1 to 250 mmol ml-1 for acetic and lactic acids and from 25 mmol ml-1 to 100 mmol ml-1 for citric acid . Initial pH values ranged from 4.7 to 6.0 . Although the growth rate of L . monocytogenes Scott A was slower when incubated at 25 degrees C than at 37 degrees C, the relative acid and pH inhibition was identical at both temperatures . As the initial pH values decreased and/or the total acid concentrations increased, the growth rates of L . monocytogenes Scott A decreased . Compared at equal initial pH values and on an equimolar total acid basis, the relative inhibition effect was generally acetic > lactic > citric . When based on initial undissociated acid concentrations, the inhibition effect was citric > lactic > acetic . The effect of differing acid and pH environments on pHin was determined . At equimolar total acid concentrations, the pHin of the cell was changed the least by citric acid and the most by acetic acid . Growth rates were influenced by the pHin and the acid used to adjust the system.

Infect Immun, 1993 May, 61(5), 2245 - 8
Characterization of an aromatic amino acid-dependent Listeria monocytogenes mutant: attenuation, persistence, and ability to induce protective immunity in mice; Alexander JE et al.; A transposon insertion mutant of Listeria monocytogenes was shown to be deficient in prephenate dehydratase, an enzyme acting late in the pathway for biosynthesis of phenylalanine . This mutant had reduced virulence in mice . The mutant and parent strains persisted to the same extent in the tissues of infected mice and elicited similar degrees of splenomegaly . Mice vaccinated with the mutant were protected significantly from subsequent challenge with virulent L . monocytogenes.

Infect Immun, 1993 May, 61(5), 2154 - 61
Listeria monocytogenes-induced gamma interferon secretion by intestinal intraepithelial gamma/delta T lymphocytes; Yamamoto S et al.; gamma/delta T cells represent a major proportion of intestinal intraepithelial lymphocytes (IEL), and it has been suggested that these IEL serve as a first immune barrier against microbial invasion and that they do so by destroying infected epithelial cells . In the present study, we confirm that both alpha/beta and gamma/delta IEL from naive mice express potent cytotoxicity and produce gamma interferon (IFN-gamma) after T-cell receptor (TCR) engagement by specific monoclonal antibodies (MAb) . Intraperitoneal administration of the anti-gamma/delta TCR MAb GL3 caused downregulation of the gamma/delta TCR in IEL, and IEL from gamma/delta TCR-modulated mice failed to express cytotoxic activity and to secrete IFN-gamma after gamma/delta TCR engagement . In contrast, alpha/beta IEL from such mice were still cytolytic and secreted IFN-gamma . Mice were infected orally with virulent Listeria monocytogenes at doses which caused bacterial invasion through the intestinal epithelia . Although alpha/beta and gamma/delta IEL from these mice expressed high cytolytic activities in antibody-redirected killer assays, target cells pulsed with listerial antigens were not lysed . In contrast, IFN-gamma secretion by IEL from L . monocytogenes-infected mice was induced not only by anti-TCR MAb but also by target cells pulsed with listerial antigens, whereas irrelevant antigens, including heat shock protein 60, did not induce IFN-gamma secretion . Furthermore, the number of IFN-gamma-secreting IEL, as assessed by the enzyme-linked immunospot technique, was increased during listeriosis . gamma/delta TCR modulation by GL3 administration abrogated antigen-induced IFN-gamma secretion by IEL from infected mice . These findings suggest that L . monocytogenes induced IFN-gamma secretion by gamma/delta IEL from mice suffering from intestinal L . monocytogenes infection and invasion . Thus, the data provide evidence for a role of IFN-gamma-secreting IEL in local resistance against listeriosis and perhaps other food-borne diseases.

AJR Am J Roentgenol, 1993 May, 160(5), 1089 - 93
Mesenrhombencephalitis: MR findings in nine patients; Soo MS et al.; OBJECTIVE . Mesenrhombencephalitis is a serious form of brainstem inflammation predominantly involving the deep and vital portions of the brain, that is, the mesencephalon (midbrain) and rhombencephalon (pons, medulla) . Mesenrhombencephalitis is difficult to diagnose on the basis of clinical and laboratory findings alone, and access to this portion of the brain for surgical biopsy carries high morbidity . We describe the MR appearance of mesenrhombencephalitis and correlate the imaging findings with clinical information . MATERIALS AND METHODS . Unenhanced and contrast-enhanced MR images of nine patients with mesenrhombencephalitis were reviewed retrospectively and correlated with clinical, laboratory, and pathologic data . The patients were categorized according to the cause of the disease: three had herpes simplex, one had Listeria monocytogenes, and five had mesenrhombencephalitis of undetermined cause . The three patients with clinical and MR evidence of herpes simplex mesenrhombencephalitis (one confirmed by brain biopsy) were comatose at presentation, with cranial nerve abnormalities in two and seizures in one . One patient with L . monocytogenes (established by blood culture) had cranial nerve palsies, fever, and pain in the ear . Five additional patients had headache (three), fever (three), nausea and vomiting (four), cranial nerve palsies (three), coma (two), and hyporeflexia (one) or hyperreflexia (four) . Brain biopsy performed in two patients revealed chronic inflammation of unspecified cause; in one, it was compatible with viral encephalitis . RESULTS . MR images in three patients with herpes simplex mesenrhombencephalitis showed T2 signal hyperintensity in the midbrain (two), pons (one), medulla (one), and temporal lobes (three) . Parenchymal foci of hemorrhage (methemoglobin, one patient) and leptomeningeal enhancement (one patient) were identified in the temporal lobes . T2-weighted MR images in one patient with L . monocytogenes showed signal hyperintensity in the brainstem, vermis, midbrain, and internal capsules . On T1-weighted images, low signal was present in these areas, which enhanced with paramagnetic contrast agents . In the remaining five patients, T2-weighted MR images showed patchy signal hyperintensity in the pons, medulla, and thalamus in three each and in the midbrain and temporal lobes in one each . T1-weighted MR images showed normal findings (two) or signal hypointensity in the thalamus and pons in one patient each . Areas of leptomeningeal and parenchymal enhancement were identified in one patient each . Brainstem swelling was seen in three patients, one of whom had petechial hemorrhage in the pons and hydrocephalus . CONCLUSION . Mesenrhombencephalitis is a serious illness that is diagnosed by a combination of imaging, clinical, laboratory, and pathologic studies . MR imaging may be crucial to the early diagnosis of this illness, and radiologists must be familiar with this uncommon entity and its MR findings in order to make timely diagnoses and facilitate treatment.

Med Microbiol Immunol (Berl), 1993 May, 182(2), 87 - 95
Purification and characterization of a 58-kDa cell wall-associated protein from Listeria monocytogenes; Belyi YF et al.; A cell wall protein (P58) was purified from Listeria monocytogenes by detergent extraction and Superose 6 gel chromatography . It had a molecular mass of 58 kDa, was strongly hydrophobic, contained reactive thiol group(s) and was located at least partially on the surface of bacterial cells . Production of this protein varied among different Listeria, being the most prominent in NCTC 7973 of L . monocytogenes, weaker in four other strains of this species and undetectable in tested strains of L . seeligeri and L . innocua . Mice that survived experimental listerial infection produced antibodies against P58 . This fact allowed us to speculate that the described protein can be used as a marker for sero-diagnosing of listeriosis.

Mol Microbiol, 1993 May, 8(4), 653 - 61
Expression of listeriolysin and phosphatidylinositol-specific phospholipase C is repressed by the plant-derived molecule cellobiose in Listeria monocytogenes; Park SF et al.; The primary habitat of the intracellular pathogen Listeria monocytogenes is considered to be soil and decaying vegetation . As an opportunistic pathogen it must be able to recognize its entry into host tissue and, in response, co-ordinately induce the expression of virulence factors . No signature molecule, which facilitates this regulation, has been identified for any human pathogen . Our studies have demonstrated for the first time that the expression of major virulence determinants in L . monocytogenes can be repressed by an environmentally ubiquitous molecule . Transcriptional hlyA and plcA fusions to luxAB were used to monitor virulent gene expression in the presence of various disaccharides . These studies revealed that the expression of listeriolysin O and phosphatidylinositol-specific phospholipase C is repressed specifically by the plant-derived disaccharide, cellobiose.

Res Microbiol, 1993 May, 144(4), 279 - 83
Dependence of fatty acid composition of Listeria spp . on growth temperature; Puttmann M et al.; In Listeria spp., various fatty acids are produced; by far the most common members are C15 and C17 chain length fatty acids . This pattern is rather similar in all species . At low temperatures, most of the Listeria are able to change the relative composition whereby more of the C15 fatty acids are produced, which could increase the fluidity of the bacterial cell membrane under these conditions.

Science, 1993 Apr 23, 260(5107), 547 - 9
Development of TH1 CD4+ T cells through IL-12 produced by Listeria-induced macrophages; Hsieh CS et al.; Development of the appropriate CD4+ T helper (TH) subset during an immune response is important for disease resolution . With the use of naive, ovalbumin-specific alpha beta T cell receptor transgenic T cell, it was found that heat-killed Listeria monocytogenes induced TH1 development in vitro through macrophage production of interleukin-12 (IL-12) . Moreover, inhibition of macrophage production of IL-12 may explain the ability of IL-10 to suppress TH1 development . Murine immune responses to L . monocytogenes in vivo are of the appropriate TH1 phenotype . Therefore, this regulatory pathway may have evolved to enable innate immune cells, through interactions with microbial pathogens, to direct development of specific immunity toward the appropriate TH phenotype.

FEMS Microbiol Lett, 1993 Apr 15, 108(3), 311 - 8
Utilization of transferrin-bound iron by Listeria monocytogenes; Hartford T et al.; It has been demonstrated that under iron-restricted conditions, Listeria monocytogenes can utilize iron-loaded transferrin (Tf) from a range of species as its sole source of iron for growth . Human transferrin conjugated to horseradish-peroxidase (HRP-Tf) bound directly to whole cells of L . monocytogenes . This binding was blocked by apotransferrin indicating that the receptor can bind transferrin in either the iron-bound or iron-free form . Transferrin-binding was not host specific because both bovine and equine transferrin inhibited the binding of HRP-conjugated human transferrin . SDS-PAGE and Western blotting of bacterial surface extracts revealed the presence of a transferrin-binding protein of approximately 126 kDa.

Proc Natl Acad Sci U S A, 1993 Apr 15, 90(8), 3725 - 9
Interleukin 12 and tumor necrosis factor alpha are costimulators of interferon gamma production by natural killer cells in severe combined immunodeficiency mice with listeriosis, and interleukin 10 is a physiologic antagonist; Tripp CS et al.; Listeriosis in mice with the severe combined immunodeficiency (SCID) mutation is an established model in vivo and in vitro of interferon gamma (IFN-gamma)-dependent macrophage activation by natural killer (NK) cells during the development of natural immunity . We demonstrate that IFN-gamma production from SCID splenocytes is stimulated by interleukin (IL) 12, tumor necrosis factor alpha (TNF-alpha), and IL-2 but is inhibited by IL-10, IL-10, IL-12, and TNF are induced by heat-killed Listeria monocytogenes (hk-LM) from SCID splenocytes and peritoneal macrophages . IL-12 production is necessary for hk-LM to stimulate IFN-gamma production by SCID splenocytes since neutralization of IL-12 totally blocks IFN-gamma production in this system . TNF-alpha and IL-2 act synergistically with IL-12 to augment IFN-gamma production . Also, exogenous IL-2 increases the response of NK cells to hk-LM or to IL-12 and TNF-alpha . In contrast, IL-10 inhibits hk-LM-induced IFN-gamma production at two levels: (i) by inhibiting TNF and IL-12 production from these cultures (presumably from the macrophage) and (ii) by inhibiting the stimulatory effects of IL-12 and TNF-alpha on NK-cell IFN-gamma production . Thus, these data indicate that macrophage production of TNF-alpha and IL-12 stimulates the release of IFN-gamma by NK cells and that IL-10 produced in response to hk-LM inhibits this response at the level of the macrophage and the NK cell.

Ann Cardiol Angeiol (Paris), 1993 Apr, 42(4), 203 - 4
{Listeria monocytogenes femoral aneurysm}; Bensaid J et al.; Secondary infection of arterial aneurysms being a constantly possible complication, the bacteriological examination of peroperative specimens appears to be appropriate . Among responsible organisms, the presence of Listeria monocytogenes is very rare since only 13 cases have been reported in the literature . It is for this reason that it was felt to be of interest to report a new, entirely similar case of femoral aneurysm.

New Microbiol, 1993 Apr, 16(2), 189 - 203
Listeria monocytogenes infections: the organism, its pathogenicity and antimicrobial drugs susceptibility; Riviera L et al.; L . monocytogenes can induce serious, life-threatening infections . Multiple clinical manifestations of the disease include neonatal and perinatal listeriosis, infections in adult immunocompromised patients as well as in normal hosts, with the CNS as the more frequent site involved . Many outbreaks are believed to be food-borne in origin, but there can be other means of transmission . The susceptibility of L . monocytogenes to different antimicrobial drugs is reviewed . Many drugs that are highly effective in vitro show only a moderate activity in vivo, due either to their poor ability to enter the phagocytes and destroy the engulfed bacteria, as with the beta-lactams, ampicillin and amoxicillin, or to their bacteriostatic rather than bactericidal activity, as with the fluoroquinolones, or their affinity for a serum glycoprotein, as with the macrolide antibiotics . The bacterial killing appears to be enhanced by some synergistic drug associations, the best therapeutic results being achieved by trimethoprim-cotrimoxazole and ampicillin plus gentamicin . Other more recent antimicrobial drugs and drug combinations are still under clinical evaluation.

Int J Immunopharmacol, 1993 Apr, 15(3), 437 - 46
Immunotoxicity of in vitro vanadium exposures: effects on interleukin-1, tumor necrosis factor-alpha, and prostaglandin E2 production by WEHI-3 macrophages; Cohen MD et al.; Treatment of cultured mouse macrophages with either of two different vanadium compounds was shown to affect the production/release of two major immunoregulatory cytokines . The pentavalent vanadium compound ammonium metavanadate was shown previously to disrupt cell-mediated immunity at the earliest stages of an in vivo anti-Listerial response, in that mice treated with vanadium displayed decreased accessory cell recruitment and numbers of activated macrophages at infection sites . To determine whether these effects were due to vanadium-induced alterations in the production of biologically-active mediators, mouse macrophage-like WEHI-3 cells were treated in vitro with ammonium metavanadate or vanadium pentoxide prior to stimulation with lipopolysaccharide endotoxin (LPS) . After stimulation, monokine (tumor necrosis factor-alpha and interleukin-1) and prostaglandin E2 (PGE2) activities were assessed . Both vanadium compounds decreased recovered monokine activities; measured TNF alpha concentrations were also reduced . Spontaneous release of the IL-1/TNF-regulating prostanoid PGE2 was significantly increased by the highest concentration of vanadate tested, although LPS-stimulated PGE2 production was unaffected by either compound . These results indicate that, in vitro, pentavalent vanadium can interfere with immunoregulatory mediators critical for maintaining host immunocompetence.

Can J Microbiol, 1993 Apr, 39(4), 395 - 401
Pulsed-field gel electrophoresis applied for comparing Listeria monocytogenes strains involved in outbreaks; Buchrieser C et al.; Recent food-borne outbreaks of human listeriosis as well as numerous sporadic cases have been mainly caused by Listeria monocytogenes serovar 4b strains . Thus, it was of interest to find out whether a certain clone or a certain few clones were responsible for these cases and especially for outbreaks . We used pulsed-field gel electrophoresis of large chromosomal DNA restriction fragments generated by ApaI, SmaI, or NotI to analyse 75 L . monocytogenes strains isolated during six major and eight smaller recent listeriosis outbreaks . These strains could be divided into 20 different genomic varieties . Thirteen of 14 strains isolated during major epidemics in Switzerland (1983-1987), the United States (California, 1985) and Denmark (1985-1987) demonstrated indistinguishable DNA restriction patterns . In contrast, strains responsible for the outbreaks in Canada (Nova Scotia, 1981), the United States (Massachusetts, 1983), France (Anjou, 1975-1976), New Zealand (1969), and Austria (1986) and some smaller outbreaks in France (1987, 1988, 1989) were each characterized by particular combinations of DNA restriction patterns . Seventy-seven percent of the tested strains could be classified into the previously described ApaI group A (Brosch et al . 1991), demonstrating a very close genomic relatedness . Because 49% of the epidemic strains selected for this study belonged to phagovar 2389/2425/3274/2671/47/108/340 or 2389/47/108/340, fifty-six additional strains of these phagovars, isolated from various origins, were also typed to determine whether differences in DNA restriction profiles between epidemic and randomly selected strains of the same phagovars could be pointed out . Variations in DNA patterns appeared more frequently within randomly selected strains than within epidemic strains.

Int Immunol, 1993 Apr, 5(4), 371 - 82
Pathogen-induced Th1 phenotype development in CD4+ alpha beta-TCR transgenic T cells is macrophage dependent; Hsieh CS et al.; We used an ovalbumin (OVA)-specific alpha beta-TCR transgenic mouse system to examine the cellular basis of CD4+ T helper (Th) phenotype development in vitro . Heat-killed Listeria monocytogenes (HKLM) strongly promotes the in vitro development of a Th1 phenotype in OVA-specific transgenic T cells . Listeria monocytogenes effects to promote the Th1 phenotype are antigen presenting cell (APC) dependent and occur when splenic APCs, but not the B cell hybridoma TA3, are present during T cell activation . However, addition of FACS-sorted macrophages to TA3 activated cultures restores the ability of Listeria to induce Th1 development . This effect on T cell development does not require MHC-restricted antigen presentation by macrophages, but may act through soluble factors . Although the presence of interferon gamma is necessary for Listeria induction of Th1 development, IFN-gamma alone is insufficient to induce Th1 development . Furthermore, Listeria induction of the Th1 phenotype does not require several known products of activated macrophages, including interleukin-1 (IL-1), tumor necrosis factor (TNF-alpha), IL-6, or nitric oxide . Although transforming growth factor-beta (TGF-beta) may mediate some Listeria effects, it does not fully reconstitute Listeria effects to promote Th1 development . In summary, host interactions with bacterial pathogens can affect the development of specific Th subsets, allowing innate immune cells to direct development of specific immune phenotype . For Listeria monocytogenes, the induction of the Th1 phenotype may involve a novel cytokine distinct from several known factors produced by activated macrophages.

Int J Food Microbiol, 1993 Apr, 18(2), 97 - 106
Five-tube most-probable-number method using the Fung-Yu tube for enumeration of Listeria monocytogenes in restructured meat products during refrigerated storage; Yu LS et al.; The survival of Listeria monocytogenes in cooked, chopped hams stored at 5 degrees C for 5 weeks was studied . Slices of chopped ham (25 g) were inoculated with a three-strain mixture of L . monocytogenes (LM 101M, LM 103M, and Scott A) at levels of < or = 350 cfu/25 g and packaged in Stomacher bags . Prior to inoculation, L . monocytogenes cells were subjected to either heat-injury (56 degrees C, 30 min) or freeze-injury (-18 degrees C, 14 days) . The organisms were detected by a five-tube most-probable-number (MPN) technique using the motility enrichment Fung-Yu tube, and the direct plating method . After storage at 5 degrees C for 1 week, there was a one log10 reduction in counts . Thereafter, Listeria recovered and heat- and freeze-injured cells grew to 10(7) and 10(8) within 5 weeks, respectively . Similar results were obtained from both methods . However, direct plating could not recover L . monocytogenes at low levels (< or = 100/25 g), whereas MPN counts were obtained at these low levels . The pH (6.22 +/- 0.10) of the chopped hams remained constant throughout the study . These results indicated that low numbers of L . monocytogenes surviving sublethal heat- or freeze-injury could initiate growth after recovery in chopped hams . The five-tube MPN method using the Fung-Yu tube was effective in enumerating both low and high levels of L . monocytogenes in food.

Int J Food Microbiol, 1993 Apr, 18(2), 161 - 6
Characterization of Listeria strains isolated from soft cheese; Danielsson-Tham ML et al.; Three soft cheeses were exposed to quantitative analysis for listeria and found to contain a large number of listeria . Thirty-five of the listeria strains isolated from the three cheeses were characterized by use of biochemical tests, serotyping, phagetyping and DNA restriction enzyme analysis . Seven isolates were identified as Listeria innocua and 28 as Listeria monocytogenes . Two to four different clones of L . monocytogenes could be identified from each cheese . In contrast, only one clone could be detected among the L . innocua isolates . From an epidemiological point of view the findings of different clones of L . monocytogenes in the same cheese emphasize the need for typing several listeria isolates from one and the same food sample . It is concluded that the best overview of the population of the listeria strains is obtained after direct plating of the sample followed by enumeration, isolation and extensive typing.

Int J Food Microbiol, 1993 Apr, 18(2), 139 - 49
Modelling bacterial growth of Listeria monocytogenes as a function of water activity, pH and temperature; Wijtzes T et al.; Temperature, pH and water activity are important factors controlling the microbiological safety of foods . To describe the growth rate of Listeria monocytogenes in relation to these factors, two equations have been developed . Both equations are based upon the Ratkowsky equation for temperature and growth rate . The first equation predicts growth rate at sub-optimal pH values, sub-optimal temperatures and sub-optimal water activities, the second model predicts growth throughout the entire pH range . The first model may be used to predict growth rates between pH 4.6-6.7, temperature range 5-35 degrees C and a water activity range of 0.95-0.997 . The second model is valid throughout the pH range of 4.6-7.4 and the same temperature and water activity range as the first model.

Int J Food Microbiol, 1993 Apr, 18(2), 127 - 38
Antilisterial activity of pediocin AcH in model food systems in the presence of an emulsifier or encapsulated within liposomes; Degnan AJ et al.; The listericidal activity of pediocin AcH was evaluated in slurries (5, 10, or 25% in dH2O) of nonfat dry milk, butterfat, beef muscle tissue, or beef tallow . Slurries were inoculated with Listeria monocytogenes (2-strain mixture; 2.5 x 10(6) cfu/ml) and then with pediocin AcH (30,000 arbitrary units (AU) per ml of slurry) . Although pediocin activity was reduced in slurries, sufficient pediocin remained to decrease the listeriae population . For all slurries tested, the greatest decrease in counts of Listeria (1.2-1.8 log10 cfu decrease) and decrease in pediocin activity (12-54% recovery of original activity) occurred within 1.5 min of addition of pediocin to slurries . Thereafter, counts of Listeria did not change appreciably, but pediocin activity continued to decrease in most treatments for up to 60 min . In general, greater activity was recovered from: (i) slurries of lower (5%) compared to higher (25%) concentrations of food; and (ii) dairy- compared to meat-based slurries . Next, pediocin AcH was encapsulated within phosphatidyl-choline-based liposomes before addition to slurries (10%), or was used unencapsulated in slurries (10%) containing the emulsifier Tween 80 . Greater pediocin activity (29-62% increase; average over all concentrations) was recovered from slurries containing encapsulated compared to free pediocin AcH . Likewise, greater pediocin activity was recovered from slurries containing an emulsifier (4-90% increase; average over all concentrations) compared to otherwise similar slurries without Tween 80 . The additional recovery of pediocin activity afforded by liposomes or Tween 80 underscores the potential for direct application of biopreservatives to provide another hurdle for L . monocytogenes in foods.

Appl Environ Microbiol, 1993 Apr, 59(4), 1247 - 50
A proposed nonpathogenic biological indicator for thermal inactivation of Listeria monocytogenes; Fairchild TM et al.; Listeria innocua M1 was developed as a thermal processing indicator organism for L . monocytogenes by selection of a rifampin- and streptomycin-resistant mutant . zetaD values were 5.6 and 5.8 degrees C, and D (68 degrees C) values were 3.8 and 4.9 s for L . monocytogenes and L . innocua, respectively, in skim milk . The advantages of easy selection, similar heat resistance, and nonpathogenicity make L . innocua M1 appropriate for challenge studies designed to evaluate process lethality with respect to L . monocytogenes.

J Appl Bacteriol, 1993 Apr, 74(4), 480 - 3
Bactericidal activity of disinfectants on Listeria; Van de Weyer A et al.; The bactericidal activity on Listeria spp . of nine disinfectants used in the food industry was studied by previously published methods . The disinfectants were diluted to the test concentration in sterile standard hard water . Various types of chemical agents were evaluated, including phenolic compounds, alcohols, quaternary ammonium compounds, surface-active agents, aldehydes and disochlorine tablets . The following strains isolated from cheese were studied: Listeria innocua, L . welshimeri, L . monocytogenes 1/2a, 1/2b, 1/2c and 4b . The results show that the listerias are not particularly resistant to disinfectants but the efficacy of some agents is affected by organic matter.

J Appl Bacteriol, 1993 Apr, 74(4), 428 - 32
Heat resistance of Listeria monocytogenes by two recovery media used with and without cold preincubation; Sorqvist S; Three strains of Listeria monocytogenes were heat-treated at three temperatures in physiological saline by a capillary tube method . Recovery of heat-treated bacteria was performed on blood agar and on tryptose phosphate agar with ferric citrate and aesculin (TPA-FE) . Both media were used in two ways: (1) incubation at 37 degrees C for 7 d, and (2) preincubation at 4 degrees C for 5 d in order to obtain repair of heat-injured bacteria, followed by incubation at 37 degrees C for 7 d . D and z values were determined . In both incubation procedures, better average recovery was obtained on blood agar than on TPA-FE . Thus, higher D values were recorded when blood agar was used . In most cases the differences were statistically significant . Repair at 4 degrees C of heat-injured bacteria occurred on both media but the proportions of repaired bacteria were higher on blood agar . The repair on this medium was generally reflected in higher D values for preincubated samples . Some significant differences in heat resistance were noted between the strains.

J Clin Periodontol, 1993 Apr, 20(4), 279 - 81
Effect of rinsing time on antiplaque-antigingivitis efficacy of listerine; Ross NM et al.; This double-blind, controlled clinical study compared the effectiveness of 30- and 60-s listerine rinses in both inhibiting the development of, and reducing existing, supragingival plaque and gingivitis, using an experimental gingivitis model . 94 subjects completed this study . For each subject, a modified gingival index, modified Quigley-Hein plaque index and Eastman interdental bleeding index were recorded at baseline and at 2 weeks . Following the baseline examinations, subjects received half-mouth prophylaxes, and began 2 x daily supervised rinsing either with listerine for 30 or 60 s or with a control mouthrinse for 30 s as their sole oral hygiene measure . Statistical analysis (ANCOVA) showed that both the 30- and 60-s listerine rinses were significantly (p < 0.01) more effective than the control in inhibiting and reducing plaque, gingivitis and gingival bleeding . Although 60-s rinses with listerine were significantly more effective (p < 0.01) than 30-s rinses in controlling plaque, the 2 rinse durations were similarly effective in controlling interdental bleeding and gingivitis . This study confirms the recommendation of 2x daily rinsing with listerine for 30 s as an effective regimen for gingivitis control.

Scand J Immunol, 1993 Apr, 37(4), 443 - 6
Differences in the rate of intracellular killing of catalase-negative and catalase-positive Listeria monocytogenes by normal and interferon-gamma-activated macrophages; van Dissel JT et al.; Intracellular killing of catalase-positive bacteria by murine resident macrophages requires the presence of extracellular serum, whereas killing of catalase-negative bacteria can occur in the absence of serum . To find out whether the intracellular killing of bacteria by rIFN-gamma-activated macrophages also requires serum stimulation, we investigated the handling of ingested catalase-negative and -positive Listeria monocytogenes by peritoneal macrophages of normal Swiss mice and mice injected i.p . with 1 x 10(4) U rIFN-gamma 18 h earlier . In the absence of extracellular serum, rIFN-gamma-activated macrophages killed ingested catalase-negative Listeria more efficiently (P < 0.01) than normal resident macrophages . Maximal killing of catalase-negative bacteria by rIFN-gamma-activated macrophages required an extracellular serum concentration of only 1.0 to 2.5% compared with the 10% needed by normal macrophages . No differences were observed in the rates of intracellular killing of catalase-positive Listeria by rIFN-gamma-activated and normal resident macrophages: both populations of macrophages required 10% extracellular serum for maximal killing of these bacteria, and killing was minimal in the absence of serum . The rIFN-gamma-activated macrophages displayed enhanced O2-consumption after stimulation with phorbol myristate acetate and heat-killed Listeria compared with macrophages from normal mice . These findings indicate that, under suboptimal stimulation by extracellular serum, rIFN-gamma enhances the intracellular killing of catalase-negative Listeria which lack endogenous catalase acting as a scavenger of reactive oxygen intermediates . The mechanism underlying the enhancement is probably the amplification of the respiratory burst by IFN-gamma.

Infect Immun, 1993 Apr, 61(4), 1334 - 9
Membrane damage and interleukin-1 production in murine macrophages exposed to listeriolysin O; Yoshikawa H et al.; To obtain some insight into the interaction between listeriolysin O (LLO) and the macrophage membrane, we examined the effect of purified Listeria monocytogenes hemolysin on the viability and functions of mouse peritoneal exudate macrophages . The study showed that purified LLO impaired a variety of functions of the macrophages . First, it suppressed the luminol-dependent chemiluminescence response of macrophages . Second, it suppressed the phagocytic ingestion of opsonized sheep erythrocytes and latex beads . Third, exposure of macrophages to LLO resulted in an increase in dead cells, as determined by the trypan blue dye exclusion method . An interesting observation of this study is that the LLO-induced production of interleukin-1 from macrophages could not be blocked by preincubation with cholesterol, while the membrane-damaging ability could be blocked by cholesterol . The dissociation of the blocking effects of cholesterol suggests that the interleukin-1-inducing ability of LLO may be distinct from its membrane-damaging ability.

Microbiologia, 1993 Apr, 9(1), 69 - 7
{Comparison of 3 enrichment media for the study of Listeria monocytogenes in foods}; Vandevenne CA; Analysis organised by the BCR (Bureau Communautaire de Reference) using material in form of capsules containing a strain of Listeria monocytogenes of known concentrations in various types of foods were carried out within the interlaboratory trials . In this work, it is demonstrated that the LEB (Listeria enrichment broth) medium is, of the three media assayed, the most adequate to investigate this organism in foods.

Mol Microbiol, 1993 Apr, 8(1), 143 - 57
Dual roles of plcA in Listeria monocytogenes pathogenesis; Camilli A et al.; The plcA gene of Listeria monocytogenes encodes a secreted phosphatidylinositol-specific phospholipase C (Pl-PLC) . Recent studies have established that transposon mutations within plcA result in avirulence for mice and pleiotropic effects when examined in tissue-culture models of infection . Genetic analysis reveals that many of the effects of the transposon insertions are due to loss of readthrough transcription from plcA into the downstream gene prfA, which encodes an essential transcription factor of numerous L . monocytogenes virulence genes . Construction of an in-frame deletion within plcA had no effect on expression of prfA thus allowing direct assignment of a role of the Pl-PLC in pathogenesis . Pl-PLC was shown to play a significant role in mediating escape of L . monocytogenes from phagosomes of primary murine macrophages . Interestingly, this defect manifested itself in vivo in the liver but not in the spleen of infected mice.

Infect Immun, 1993 Apr, 61(4), 1576 - 80
The zinc metalloprotease of Listeria monocytogenes is required for maturation of phosphatidylcholine phospholipase C: direct evidence obtained by gene complementation; Poyart C et al.; The maturation of the 33-kDa proenzyme to the 29-kDa phosphatidylcholine phospholipase C (PC-PLC) of Listeria monocytogenes requires the production of the zinc metalloprotease encoded by mpl, the proximal gene of the lecithinase operon . We recently described a low-virulence lecithinase-deficient mutant of L . monocytogenes EGD-SmR, designated JL762, generated by a single insertion of transposon Tn1545 in mpl . This mutant failed to produce the 29-kDa PC-PLC, an exoenzyme probably involved in cell-to-cell spreading . The role of the product of the mpl gene in production of PC-PLC was investigated in trans-complementation experiments . The entire mpl gene was cloned in a plasmid able to replicate in L . monocytogenes . This recombinant plasmid was introduced into JL762 and restored the lecithinase phenotype on egg yolk agar and the production of the active 29-kDa PC-PLC in culture supernatants and partially restored the level of virulence . These results demonstrate that zinc-dependent metalloprotease of L . monocytogenes is involved in the virulence of this bacteria at least through its action on PC-PLC.

Mol Pharmacol, 1993 Apr, 43(4), 542 - 7
Mechanism of hepatic cytochrome P450 modulation during Listeria monocytogenes infection in mice; Armstrong SG et al.; There have been numerous reports of altered drug clearance during episodes of viral infection and during the clinical use of recombinant interferons, but there have been very few reports regarding the effect of active bacterial infections on cytochrome P450-mediated metabolism . The objective of this study was to determine the mechanism by which the Gram-positive bacteria Listeria monocytogenes causes a depression of cytochrome P450-mediated biotransformation in mice . After induction with beta-napthoflavone, hepatic microsomal cytochrome P450 levels were reduced by 40% and ethoxyresorufin-O-dealkylase (EROD) activity was decreased by 65% in mice infected for 48 hr . The loss of EROD activity was accompanied by losses of cytochrome P450IA apoenzyme and cytochrome P450IA mRNA . Listeria infection did not affect total mRNA levels, as determined by oligo(dT)18 hybridization . The time course of these effects demonstrated that an up-regulation of cytochrome P450IA preceded the loss of this isozyme and that changes in cytochrome P450IA mRNA preceded the changes in apoenzyme levels and EROD activity . In hepatic microsomes from uninduced mice, cytochrome P450 levels and the rates of dealkylation of ethoxyresorufin, benzyloxyresorufin, pentoxyresorufin, and aminopyrine were significantly reduced, by 40-60%, after 48 hr of infection . The decrease in aminopyrine-N-demethylase activity was accompanied by a loss of cytochrome P450IID9 mRNA after 48 hr of infection . Cytochrome P450IID9 mRNA levels returned to normal after 96 hr of infection, whereas aminopyrine-N-demethylase activity was still decreased at this time . No up-regulation of cytochrome P450IID9 occured before the loss of this isozyme . The results of this study indicate that the changes in the levels of cytochrome P450IA and cytochrome P450IID9 that are observed during L . monocytogenes infection occur at a pretranslational step . If other bacteria have a similar capacity to depress cytochrome P450 by such a mechanism, then drugs with narrow therapeutic indices should be administered with caution during infectious diseases caused by bacteria or viruses.

Zentralbl Bakteriol, 1993 Apr, 278(2-3), 334 - 47
Listeria monocytogenes--a model system for studying the pathomechanisms of an intracellular microorganism; Goebel W et al.; Virulence of Listeria monocytogenes is determined by a cluster of five genes in the order plcA, hly, mpl, actA and plcB, which are coordinately regulated by a transcriptional activator, termed PrfA . The gene for PrfA is located in front of plcA . Mutations within each of these genes reduce the virulence considerably and render the mutants unable to properly multiply and/or spread within the infected host cells . Under growth-limiting conditions PrfA-dependent proteins are preferentially synthesised . These studies indicate the existence of additional PrfA-regulated proteins in L . monocytogenes . The synthesis of catalase, superoxide dismutase, LmaA and p60 is not under the control of PrfA . These proteins seem to be also associated with virulence of L . monocytogenes . P60-related proteins are found as major extracellular proteins in all Listeria species but only p60 of L . monocytogenes is able to restore the failure of R-mutants (exhibiting a drastically reduced synthesis of p60) to adhere to 3T6 mouse fibroblasts . Adherence of L . monocytogenes to the epithelial Caco-2 cells seem to be independent of p60 . The p60 protein of L . monocytogenes differs characteristically from the p60-related proteins of the nonvirulent Listeria species.

Mol Microbiol, 1993 Apr, 8(2), 219 - 27
Surface-associated, PrfA-regulated proteins of Listeria monocytogenes synthesized under stress conditions; Sokolovic Z et al.; The expression of the five clustered genes of Listeria monocytogenes: plcA, hly, mpl, actA and plcB is under the control of the positive regulation factor PrfA . Listeriolysin, encoded by the hly gene, is the only prominent PrfA-controlled gene product observed when L . monocytogenes strain NCTC 7973 is cultured in a rich medium at 37 degrees C to the logarithmic growth phase . Stress conditions such as heat-shock or stationary culture conditions lead to the induction of additional PrfA-dependent proteins (PdPs): ActA (92 kDa), a 38 kDa protein of unknown function and a 34 kDa protein which probably represents PlcA . Under nutrient-stress conditions PdPs are preferentially synthesized and in addition to the already known PdPs at least five new, not yet functionally identified PdPs are detected . All PdPs are either secreted or are localized at the cell surface . Differences in the amount as well as the sizes of the PdPs are observed in different L . monocytogenes strains.

J Comp Pathol, 1993 Apr, 108(3), 241 - 60
Neuropathological findings in cattle with clinically suspect but histologically unconfirmed bovine spongiform encephalopathy (BSE); McGill IS et al.; Neuropathological observations were made in 200 clinically suspected cases of bovine spongiform encephalopathy (BSE) in which pathognomonic vacuolar changes were absent . Routine histological and immunocytochemical techniques were applied to formalin-fixed, paraffin-embedded sections of the central nervous system . Significant neuropathological findings were detected in 85 (42.5 per cent) cases . The most frequent lesion, detected in 46 (23 per cent) cases, was a focal white matter vacuolation principally affecting the substantia nigra, but its clinical significance was unclear . Listeriosis was diagnosed in 17 (8.5 per cent) cases . In three of seven cases of non-suppurative encephalitis, lesions suggested sporadic bovine encephalomyelitis, a disease not previously reported in the UK . Suppurative thromboembolic or granulomatous lesions accounted for other inflammatory changes . Neuroectodermal tumours were present in five cases (2.5 per cent); three were identical in form and considered to be atypical ependymoma . Cerebrocortical necrosis, oedema or both were detected in four cases . The remaining cases (4.5 per cent), comprised those in which the changes were minor and of doubtful significance . Incidental pathological findings included occasional degenerating or vacuolated neurones, which occurred in the red nucleus in 105 brains, in the habenular nucleus in 71 brains, and singly at other sites in 17 brains . In sections of 37 brains immunostained with antiserum to prion protein (PrP), no evidence of PrP accumulation was found, providing some evidence that the series did not contain bovine prion disease cases which, based on the histological diagnosis, had given a false negative result . It is suggested that, of 115 cases (57.5 per cent) which lacked significant histological lesions, some were suffering from metabolic disorders . The study identified diseases and lesions which feature in the differential diagnosis of BSE . Their more accurate diagnosis may become particularly important if, as predicted, the BSE epidemic declines.

Trends Microbiol, 1993 Apr, 1(1), 35 - 8
Do nonclassical, class Ib MHC molecules present bacterial antigens to T cells?
Pamer EG, Bevan MJ, Lindahl KF.
Immune responses to bacterial antigens that appear unrestricted by the MHC may involve oligomorphic MHC class Ib molecules . One example is H-2M3, which binds N-formylated peptides and presents a Listeria peptide to cytotoxic T cells from infected mice . Lack of polymorphism makes these molecules a promising target for peptide vaccines.

Trends Microbiol, 1993 Apr, 1(1), 25 - 31
The wily ways of a parasite: induction of actin assembly by Listeria; Tilney LG et al.; The intracellular pathogen Listeria has a spectacular mode of transport within and between host cells . By inducing host cell actin to assemble from its surface, the bacterium forms a tail composed of many short, crossbridged actin filaments . With this tail Listeria is propelled across the cytoplasm like a comet streaking across the sky . Here we discuss the antics of Listeria and some of the bacterial genes instrumental in maintaining it in the host.

J Hosp Infect, 1993 Apr, 23(4), 299 - 304
An epidemiological study of listeriosis complicating a bone marrow transplant; Want SV et al.; Following an unrelated-donor bone marrow transplant a six-year-old child with severe aplastic anaemia developed Listeria monocytogenes septicaemia and meningitis . Cook-chill foods consumed during his stay in hospital were found to contain strains of L . monocytogenes and other Listeria species . Whole cell protein SDS-PAGE was performed on all isolates . No food isolates were found that were identical to the patient's strain by this technique or by serotyping . The usefulness of whole cell protein SDS electrophoresis for listeria strain differentiation is discussed.

J Immunol, 1993 Apr 1, 150(7), 2901 - 9
Reactive nitrogen intermediates suppress the primary immunologic response to Listeria; Gregory SH et al.; Reactive nitrogen intermediates (RNI), e.g., nitric oxide derived from a terminal guanido nitrogen atom of L-arginine, exhibit potent antimicrobial activity in vitro . The function of these intermediates in host defenses in vivo, however, is presently unclear . Experiments were undertaken to determine the role of RNI in the resolution of primary listerial infections of the liver . Serum RNI levels were elevated significantly in mice infected with Listeria monocytogenes . Moreover, a marked increase in RNI production was found in cultures of the parenchymal, as well as the nonparenchymal, liver cells obtained from Listeria-infected mice . RNI did not kill Listeria treated directly, however, nor were they a factor in the listericidal activity exhibited by hepatic cells . Rather, the elevated production of RNI during primary infection appeared to promote the replication of Listeria in vivo . Mice administered NG-monomethyl-L-arginine, a competitive inhibitor of RNI production, exhibited a 10- and a 100-fold reduction in the number of Listeria in their lives on days 3 and 7 postinfection, respectively . In vitro, NG-monomethyl-L-arginine stimulated the Ag-specific proliferation of T lymphocytes derived from Listeria-infected mice at concentrations that inhibited RNI production . These latter findings suggest that the elevated production of RNI during primary listerial infections suppresses host defenses by diminishing the proliferation and, consequently, the biologic response of immune cell populations.

Science, 1993 Mar 19, 259(5102), 1742 - 5
Immune response in mice that lack the interferon-gamma receptor; Huang S et al.; Interferon-gamma (IFN-gamma) exerts pleiotropic effects, including antiviral activity, stimulation of macrophages and natural killer cells, and increased expression of major histocompatibility complex antigens . Mice without the IFN-gamma receptor had no overt anomalies, and their immune system appeared to develop normally . However, mutant mice had a defective natural resistance, they had increased susceptibility to infection by Listeria monocytogenes and vaccinia virus despite normal cytotoxic and T helper cell responses . Immunoglobulin isotype analysis revealed that IFN-gamma is necessary for a normal antigen-specific immunoglobulin G2a response . These mutant mice offer the possibility for the further elucidation of IFN-gamma-mediated functions by transgenic cell- or tissue-specific reconstitution of a functional receptor.

Eur J Clin Microbiol Infect Dis, 1993 Mar, 12(3), 162 - 9
Characterization of Listeria strains from a foodborne listeriosis outbreak by rDNA gene restriction patterns compared to four other typing methods; Nocera D et al.; The rDNA gene restriction patterns of 134 isolates of Listeria species were determined with pKK3535--a pBR322 derived plasmid containing an Escherichia coli rRNA operon--used as a probe following digestion of chromosomal DNA by EcoRI endonuclease . Nineteen reference and type strains representing all species and serotypes of Listeria showed 17 distinct ribotypes . One hundred and fifteen wild strains of Listeria monocytogenes were ribotyped and the results were compared to those of serotyping, phage typing, multilocus enzyme electrophoresis (MEE) and restriction endonuclease analysis (REA) . Ninety-six Listeria monocytogenes serotype 4b wild strains displayed six distinct ribotypes (I-VI), 72% (69/96) of them clustering in two very close rDNA patterns (I and II) of eight and nine bands, respectively . The same 96 strains displayed six REA patterns and eight MEE electrotypes . Among the 96 Listeria monocytogenes 4b isolates, the 34 epidemic strains defined by phage typing and by epidemiological data all belonged to one ribotype (ribotype I) representing 56% of the strains belonging to this ribotype . These same 34 epidemic strains were also grouped by REA and MEE typing in a unique profile (REA-A) and MEE electrotype (ET 1) . Twenty-two Listeria monocytogenes strains of serogroup 1/2 analyzed by rDNA typing showed nine distinct ribotypes . For the 96 Listeria monocytogenes 4b strains studied, the discriminatory index was highest for phage typing and for any combination including phage typing . Ribotyping appears to be a well reproducible molecular typing method and could be a useful complement to other typing methods for the epidemiological study of listeriosis.

Eur J Clin Microbiol Infect Dis, 1993 Mar, 12(3), 157 - 61
Incidence of listeriosis in Barcelona, Spain, in 1990 . The Collaborative Study Group of Listeriosis of Barcelona; Nolla-Salas J et al.; A population-based register of cases of listeriosis admitted to acute-care hospitals has been established in Barcelona, Spain, in order to estimate the basal incidence of sporadic cases and to facilitate epidemiological surveillance of potential epidemics . Eleven acute-care hospitals reported all cases of listeriosis to a central unit following a standardized protocol . During 1990, 31 patients with listeriosis were identified, 18 of whom were residents of the city, resulting in an annual incidence of 10.95 cases per million inhabitants . Twelve of the 31 cases occurred in the period from July to September 1990, ten of them being community-acquired . The incidence of listeriosis was higher in elderly (> or = 65 years) and immunosuppressed persons . Forty-two percent of the cases were considered to be nosocomial infections . The overall mortality rate was 51.6% . The incidence of listeriosis in the present study is one of the highest reported in the literature . A high sensitivity of the reporting system with good case identification techniques, or demographic and environmental characteristics related to Listeria monocytogenes infection in our area, might be possible reasons for this geographic variation.

APMIS, 1993 Mar, 101(3), 249 - 56
Effect of Legionella pneumophila sonicate on killing of Listeria monocytogenes by human polymorphonuclear neutrophils and monocytes; Rechnitzer C et al.; Legionella pneumophila shares with other intracellular pathogens the ability to resist intracellular killing within phagocytes . An increasing number of cellular components of L . pneumophila are proposed as pathogenic factors of the organism . At the site of infection, the phagocytic cells will be exposed to bacterial components, either expressed on the surface of the organisms or released in the environment upon cell lysis . In this study, we have investigated the effect of water-soluble bacterial components present in L . pneumophila sonicate on the phagocytosis and bactericidal activity of human polymorphonuclear neutrophils and monocytes . Preincubation of neutrophils with L . pneumophila sonicate did not affect phagocytosis of L . monocytogenes, whereas Listeria killing was significantly inhibited at sonicate concentrations of 1 and 2 mg/ml . The phenol phase of a phenol-water extraction, containing most of the lipopolysaccharide (LPS), had no inhibitory effect on the listericidal activity of neutrophils . Killing of Listeria by monocytes was inhibited in a similar manner . The inhibitory activity was mainly recovered in the sonicate fraction above 100 kDa, suggesting that components organized in larger molecular complexes are most likely to represent the inhibitory factors . The inhibitory activity of L . pneumophila sonic extract appears to be related to inhibition of killing mechanisms since uptake of Listeria was not affected by the sonicate . Our observations indicate that as Legionella infection progresses, bacterial components liberated by cell lysis could exert a detrimental effect on the antimicrobial function of phagocytes, stressing the importance of early treatment of Legionnaires' disease to reduce bacterial numbers in the infected tissues.

Infection, 1993 Mar-Apr, 21(2), 125 - 6
Listeria monocytogenes infection of a prosthetic vascular graft; Van Noyen R et al.; A 75-year-old man was admitted for acute ischaemia of his right leg for which he had undergone vascular prosthetic surgery at another hospital, ten and three years before . Cultures of the thrombosed graft and the clots removed on re-operation were positive for Listeria monocytogenes . After parenteral treatment with amoxicillin-clavulanic acid and gentamicin, the patient died from cardiorespiratory failure.

Br Vet J, 1993 Mar-Apr, 149(2), 165 - 70
A field study of ovine listerial meningo-encephalitis with particular reference to cerebrospinal fluid analysis as an aid to diagnosis and prognosis; Scott PR; In a field study of listerial meningo-encephalitis involving 21 sheep from six silage-fed flocks, the neurological signs included profound depression, circling, involvement of the trigeminal and facial cranial nerves and lateral recumbency with propulsive limb movements . Within the six flocks the incidence of listerial meningo-encephalitis did not exceed 1% of the adult sheep at risk . Eleven of 18 (61%) adult animals were 2 years old . Evidence of an intrathecal inflammatory response in suspected listerial meningo-encephalitis cases was indicated by an increased cerebrospinal fluid (CSF) protein concentration greater than 0.4 g/l in 18 of 21 cases (86%), increased white cell count above 0.012 x 10(9)/l in 17 cases (81%) and lymphocyte percentage below 50% in all animals . None of the CSF parameters proved to be a reliable prognostic indicator because of the range of CSF values obtained and the small number of sheep which recovered.

Rev Clin Esp, 1993 Mar, 192(5), 226 - 7
{Listeria monocytogenes infection in HIV patients: 2 new cases}; Lopez-Gomez M et al.; Two new cases of infection due to Listeria monocytogenes in two females with HIV are discussed, one of them with full blown AIDS and the other pregnant and without knowledge of her seropositivity until that moment . Its clinical manifestation as a meningeal manifestation and bacteremia, coincide with the few cases described until now; different hypothesis invoked until now are reviewed to justify this infrequent association HIV-Listeria.

J Natl Med Assoc, 1993 Mar, 85(3), 225 - 8
Listeria-associated pericarditis in an AIDS patient; Ferguson R et al.; Listeria monocytogenes is a pathogenic, facultative intracellular gram-positive rod, generally seen in cell-mediated immunocompromised states . In acquired immunodeficiency syndrome (AIDS), it most commonly presents as bacteremia or meningitis . An association with pericarditis has not been described previously in this group of patients . This article describes a case of pericarditis secondary to listeriosis involving a focal pancarditis and necrosis of the A-V node with subsequent refractory ventricular tachyarrhythmias in an immunodeficient patient presenting with altered mental status . Infectious etiologies should be considered for "benign" appearing pericardial effusions in AIDS patients and the diagnosis of listeriosis excluded in the presence of "diphtheroid-like" organisms.

J Gen Microbiol, 1993 Mar, 139 ( Pt 3), 609 - 16
Cell-surface location of Listeria-specific protein p60--detection of Listeria cells by indirect immunofluorescence; Ruhland GJ et al.; A specific polyclonal antiserum was prepared against a gel-purified 60 kDa extracellular protein of Listeria monocytogenes ATCC 19111 corresponding to protein p60 previously detected in culture broths of L . monocytogenes strains Mackaness and EGD {Kuhn, M . & Goebel, W . (1989), Infection and Immunity 57, 55-61} . Indirect immunogold labelling combined with transmission electron microscopy and high-resolution scanning electron microscopy were used to investigate the location and distribution of p60 on the bacterial cell surface . In bacteria grown to the early stationary phase about 25% of the extracellular protein was estimated to be associated with the cell surface . The anti-p60 antiserum proved to be Listeria-specific . In an indirect immunofluorescence test the antiserum reacted with Listeria strains representing all species and different serotypes, except L . seeligeri, L . welshimeri, L . grayi and L . murrayi . No immunological cross-reactions were observed with 27 strains of bacteria from 16 other genera . The value of the anti-p60 antiserum in developing a diagnostic assay for Listeria cells in environmental samples and foods is discussed.

Int J Food Microbiol, 1993 Mar, 18(1), 15 - 24
A model of food-borne Listeria monocytogenes infection in the Sprague-Dawley rat using gastric inoculation: development and effect of gastric acidity on infective dose; Schlech WF 3rd et al.; Recent epidemiological evidence suggests that Listeria monocytogenes (LM) is a food-borne pathogen in humans . A model of LM infection was developed using the Sprague-Dawley (SD) rat to study the interaction of LM with gastrointestinal epithelium as the first step in the pathogenesis of invasive listeriosis . Conventionally raised, juvenile female SD rats were given 10(2)-10(9) virulent L . monocytogenes, serotype 4b or nonpathogenic Listeria species . Only rats given virulent LM developed dose-dependent invasive infection of the liver and spleen . Light and electron microscopic studies suggested attachment to and invasion of the gastrointestinal mucosa by virulent LM . Because the development of invasive listeriosis in humans has been epidemiologically associated with a decrease in gastric acidity, the effect of decreasing gastric acidity on dose-dependent infection was studied . Rats were pretreated with cimetidine (50 mg/kg) by intraperitoneal injection prior to oral inoculation of 10(2)-10(9) virulent L . monocytogenes . Cimetidine significantly lowered the infective dose of virulent L . monocytogenes (P < 0.05) . This oral model should allow further study of host and organism-specific virulence factors mediating the gastrointestinal phase of invasive LM infection, an increasingly important public health problem.

J Clin Microbiol, 1993 Mar, 31(3), 749 - 50
Evaluation of the API Coryne system for identification of Listeria species; Kerr KG et al.; The API Coryne system, a commercially available system for the identification of coryneform bacteria, was used to identify 103 strains of Listeria spp . from clinical and environmental sources . All isolates were identified correctly to the genus or species level, although complete characterization also required tests for beta-hemolysis and CAMP reaction.

Arch Surg, 1993 Mar, 128(3), 318 - 25
Administration of dehydroepiandrosterone to burned mice preserves normal immunologic competence; Araneo BA et al.; Burned individuals display a reduced ability to elicit cellular and humoral immune responses and a depression in the vitro production of certain T-cell lymphokines . Treatment of burned mice with 100 micrograms of dehydroepiandrosterone within 1 hour after injury resulted in preserving a completely normal capacity to produce T-cell-derived lymphokines and to generate cellular immune responses . In addition, dehydroepiandrosterone-treated thermally injured mice demonstrated an above-normal ability to resist an induced infection with the intracellular pathogen, Listeria monocytogenes . Dehydroepiandrosterone-treated animals also did not exhibit the sustained plasma levels of interleukin 6 that normally accompany thermal injury and infection . Because of its antiglucocorticoid effects and positive immunoregulatory influences, we believe dehydroepiandrosterone to be a beneficial form of therapy for thermally injured individuals.

Infect Immun, 1993 Mar, 61(3), 1113 - 6
Listeria monocytogenes infection in beta 2 microglobulin-deficient mice; Roberts AD et al.; beta 2 microglobulin-deficient mice, in which the beta 2m gene has been disrupted by homologous recombination, lack functional CD8 T cells and are able to contain but not resolve an intravenous immunizing inoculum of Listeria monocytogenes . We present evidence that compensatory immunity in such immunodeficient mice was mediated by a population of gamma delta T-cell receptor-positive cells; in contrast, neither CD4 cells nor natural killer cells appeared to play any part in this process . These data further support the emerging hypothesis that immune cells other than those bearing the alpha beta T-cell receptor type can also play an important role in acquired resistance to listeriosis.

Zentralbl Bakteriol, 1993 Feb, 278(1), 58 - 68
A method for typing Listeria monocytogenes strains by classification of listeriocins and phage receptors; Lebek G et al.; A method for typing Listeria monocytogenes (L.m.) strains was developed which is based on two different approaches . First, strains were classified according to the phage receptors specific to their mitomycin-induced prophages . The frequency of lysogenic strains ranged between 63 and 80%, depending on the serotype . For non-lysogenic strains, a reversed phage-receptor analysis was applied based on the susceptibility of the strains to be typed against bacteriophages from selected, inducible indicator strains . As a second method, typing of mitomycin-induced listeriocins was shown to be practicable as well . By this approach, it was possible to distinguish 11 different listeriocins when using a set of 7 selected indicator strains . Only two of these listeriocins were probably produced by L.m . strains of serotype 4b . A combination of the two approaches described raises the number of types . When applied to 20 human isolates of L.m . belonging to serotype 4b, 17 different types were demonstrated . 46 L.m . strains of serotype 1/2b could be differentiated into 38 types of which 18 clinical isolates represented 17 different types . 26 L.m . strains of serotype 1/2a isolated from various food products showed a large heterogeneity, with 22 different types . The power of discrimination of the method outlined recommends its application in epidemiological investigations.

Zentralbl Bakteriol, 1993 Feb, 278(1), 112 - 9
Comparative activities of macrolide derivatives on murine listeriosis; Bauer J et al.; The new macrolide derivatives such as clarithromycin, roxithromycin and azithromycin have only slightly stronger in vitro antibacterial activity on Listeria monocytogenes than the older derivatives such as erythromycin and spiramycin . In vivo, however, the new macrolides exert a much better therapeutic action on murine listeriosis . Among the new derivatives, clarithromycin is the most active . Azithromycin has one characteristic advantage: it is still active several days after cessation of therapy because of its long half-life . This strong therapeutic activity may be due to the known intracellular accumulation of macrolides in macrophages, which is essential for the eradication of intracellular bacteria such as L . monocytogenes . In spite of the strong intracellular accumulation the effector function of the defense system is not impaired, because the course of infection with a macrolide-resistant strain of L . monocytogenes in mice was not enhanced by macrolide treatment.

APMIS, 1993 Feb, 101(2), 160 - 7
A new Danish Listeria monocytogenes phage typing system; Gerner-Smidt P et al.; A phage typing system was developed for Listeria monocytogenes . Phages were released from clinical and from food strains of L . monocytogenes by mitomycin C induction . The system consists of two subsystems, one of which is used to type L . monocytogenes serotype 1 strains, containing 12 phages, and a second which is used to type serotype 4 strains, containing 14 other phages . For the serotype 1 subsystem, the reproducibility was > or = 90%, the typability 92%, and the discriminatory power, as judged by the discriminatory index, 80% . The corresponding figures for the serotype 4 subsystem were: reproducibility > or = 94%, typability 87%, and discriminatory index 87% . The performance of the whole typing system is sufficient for it to be used for screening purposes.

Appl Environ Microbiol, 1993 Feb, 59(2), 617 - 9
Comparison of conventional and reversed phage typing procedures for identification of Listeria spp; Estela LA et al.; Of 225 Listeria isolates evaluated, 199 had the same bacteriophage patterns by both the conventional (A . Audurier, A.G . Taylor, B . Carbonelle, and J . McLaughlin, Clin . Invest . Med . 7:229-232, 1984) and the new, easier to apply, "reversed" (M . J . Loessner, Appl . Environ . Microbiol . 57:882-884, 1991) phage typing procedures, 5 had different phage reactions, and the remaining 21 isolates were untypeable . Thus, the overall typeability rate was 90.7%, and 97.6% of the typeable isolates had the same phage patterns by both procedures.

South Med J, 1993 Feb, 86(2), 225 - 8
Recurrent nocardiosis in a renal transplant recipient; King CT et al.; As the case presented here illustrates, nocardiosis, like other infections in which cell-mediated immunity plays a large defensive role, can relapse after apparent cure and occasionally at times remote from the original infection . Although relapse in patients with transplants has been cited as a reason for continued prophylaxis, only a few of these cases are adequately documented . This case supports the advice of those authors who give suppressive antibiotic therapy for the duration of immunosuppression in transplant recipients recovering from infections due to Nocardia sp . Alternatively, many transplant centers are routinely using TMP/SMX chemoprophylaxis in all solid organ transplantations to prevent opportunistic infections with Pneumocystis and Listeria sp . Primary prophylaxis has also been associated with a decreased incidence of nocardial infections.

J Med Microbiol, 1993 Feb, 38(2), 122 - 8
Genetic characterisation of isolates of Listeria monocytogenes from man, animals and food; Trott DJ et al.; Multilocus enzyme electrophoresis was used to assess genetic relationships between 95 isolates of Listeria monocytogenes, most of which were isolated in Australia and New Zealand from man, animals and food . The isolates were separable into two major genetic divisions; the majority of those from human patients and animals were in division I, and the majority from those foods that were not specifically associated with human listeriosis were in division II . Isolates in division I were virulent, whereas many isolates from food were probably less virulent and did not pose a large threat to human health . However, isolates from certain foods, particularly pate, were indistinguishable from those causing disease in man, and the consumption of these products represented a clear risk factor for infection . Isolates from infected human patients in Australia and New Zealand belonged to the same clone of serotype 4b that has been responsible for major epidemics in the northern hemisphere . However, a separate clone of serotype 1/2b strains, present in both Australia and New Zealand, was responsible for two major outbreaks that occurred in Western Australia in 1978-80 and 1990-91.

Clin Exp Immunol, 1993 Feb, 91(2), 277 - 81
Differential mechanisms of intracellular killing of Mycobacterium avium and Listeria monocytogenes by activated human and murine macrophages . The role of nitric oxide; Bermudez LE; Murine peritoneal macrophages activated with interferon-gamma (IFN-gamma) produce large quantities of nitric oxide and are efficient in the killing of certain intracellular pathogens . To examine the role of this mechanism in the killing of Mycobacterium avium by murine and human macrophages, we infected mouse peritoneal macrophages and human monocyte-derived macrophages with M . avium and Listeria monocytogenes and stimulated the cells with recombinant tumour necrosis factor (TNF), granulocyte-macrophage colony-stimulating factor (GM-CSF) or IFN-gamma, in the presence or absence of N-monomethyl-L-arginine (NMA) or arginase . Neither competitive inhibition with NMA nor depletion of arginine by arginase had any effect on the inhibition of growth/intracellular killing of M . avium by activated human and murine macrophages . In contrast, activation of murine but not human macrophages infected with L . monocytogenes by IFN-gamma was significantly inhibited by the addition of NMA/arginase . Furthermore, murine macrophages produced large concentrations of nitric oxide following stimulation with recombinant cytokines, although no significant increase of nitric oxide production was observed with human monocyte-derived macrophages.

J Immunol, 1993 Feb 1, 150(3), 888 - 95
Release of nitric oxide during the T cell-independent pathway of macrophage activation . Its role in resistance to Listeria monocytogenes; Beckerman KP et al.; Immunodeficient mice are remarkably resistant to Listeria monocytogenes (LM) infection . We examined the role that nitric oxide (NO.) plays in the CB-17/lcr SCID (SCID) response to LM . SCID spleen cells produced large quantities of NO . (as measured by nitrite formation) when incubated in the presence of heat-killed LM . NO . production was dependent on the release of IFN-gamma by the SCID NK cells . When tested directly, macrophages produced large quantities of nitrite in response to LM, but only in the presence of IFN-gamma . The production of NO . induced by LM was not affected by neutralizing antibodies to TNF or IL-1 . The production of NO . was inhibited by addition of either of two inhibitors of NO.synthase, NG-monomethyl arginine, or aminoguanidine . In a different situation, NK cells that were stimulated by TNF and Listeria products to release IFN-gamma did not produce NO. . Macrophages cultured with IFN-gamma killed live LM . This increased killing of LM was significantly inhibited by amino-guanidine . In vivo, administration of aminoguanidine resulted in a marked increase in the mortality and spleen bacterial loads of LM-infected SCID or immunocompetent control mice . We conclude that NO . is a critical effector molecule of T cell-independent natural resistance to LM as studied in the SCID mouse, and that the NO.-mediated response is essential for both SCID and immunocompetent host to survive after LM infection.

FEMS Microbiol Lett, 1993 Jan 15, 106(2), 177 - 82
Reduced ribosomal thermal denaturation in Listeria monocytogenes following osmotic and heat shocks; Stephens PJ et al.; Increased thermotolerance of Listeria monocytogenes induced by exposure to a high NaCl concentration or a sublethal heat shock was concurrent with increased thermal stability of the 30S ribosomal subunit as measured by differential scanning calorimetry . It is proposed that protection of the 30S subunit is a critical mechanism for increased thermotolerance.

J Neurol, 1993, 240(4), 235 - 42
Early symptoms and outcome of Listeria monocytogenes rhombencephalitis: 14 adult cases; Uldry PA et al.; Listeria monocytogenes rhombencephalitis has never been studied in a significant group of patients . We describe 14 adult cases who were seen over a 10-year period . A biphasic illness was characteristic: (1) prodromes (5-15 days) with malaise, fatigue, headache, nausea or vomiting, and fever; (2) cranial nerve palsy with facial palsy, diplopia, dysphagia, dysarthria, usually multiple . Meningism and hemi- or tetraparesis were present in 11 patients and cerebellar dysfunction in 9 patients . In 4 cases, CT showed widening of the brain stem with disappearance of the surrounding cisterns . The cerebrospinal fluid was abnormal in all patients in whom this investigation was done (pleocytosis, elevation in protein content) . The patients received antibiotic therapy for 2-6 weeks . In the 9 patients who recovered, the neurological dysfunction improved within 2 days to 1 week of the initiation of therapy . There were 5 deaths . At autopsy in 2 cases, there was severe purulent meningitis and rhombencephalitis with predominantly polymorphonuclear cellular infiltration in 1 case, while numerous microabscesses in the midbrain, pons and medulla were observed in the other . We conclude that L . monocytogenes infection should be considered in patients who develop fever and focal neurological signs particularly localized to the brain stem.

Annu Rev Immunol, 1993, 11, 129 - 63
Immunity to intracellular bacteria; Kaufmann SH; Intracellular bacteria are endowed with the capacity to survive and replicate inside mononuclear phagocytes (MP) and, sometimes, within certain other host cells . MP are potent effectors cells that are able to engulf and kill many bacterial invaders . Therefore, intracellular bacteria had to exploit potent evasion mechanisms that allow their survival in this hostile environment . At the early phase, natural killer cells activate antibacterial defense mechanisms . During intracellular persistence, microbial proteins are processed and presented, thus initiating T cell activation . By secreting interleukins, CD4 alpha/beta TH1 cells activate MP, converting them from a habitat to a potent effector cell; TH2-dependent activities seem to be of minor importance . Cytolytic CD8 T cells represent a further element of protection . In the case of Listeria monocytogenes, the gene products responsible for virulence and for the introduction of antigens into the MHC class I pathway are being characterized . Increasing evidence points to a role of gamma/delta T lymphocytes in antibacterial immunity, although their precise function remains to be elucidated . Protection in the host is a local event focussed on granulomatous lesions . MP accumulate at the site of microbial growth and become activated through the CD4 T cell-interleukin-MP axis . Lysis of incapacitated MP and other host cells by CD8 T cells allows release and subsequent uptake by more efficient phagocytes, thus contributing to host protection . At the same time, lysis of host cells promotes microbial dissemination and causes tissue injury, which represent pathogenic aspects of the same mechanism . Research on the immune response against intracellular bacteria not only helps us to better understand how the immune system deals with "viable antigens" in constant trans-mutation, it also forms the basis for the rational design of control measures for major health problems.

FEMS Microbiol Lett, 1993 Jan 1, 106(1), 85 - 92
A 16S rRNA-based DNA probe and PCR method specific for Listeria ivanovii; Wang RF et al.; A 16S rRNA-based DNA probe and polymerase chain reaction (PCR) method was developed for identification and rapid detection of Listeria ivanovii . The probe (R-1) is 5'-GTAGTGACGCATGTCATCAC-3' corresponding to positions 185-204 in the L . ivanovii 16S rRNA sequence . DNA hybridization results indicated that R-1 probe only reacted with L . ivanovii, and not with six other species of Listeria or other bacteria tested . The PCR method using R-1 and a reverse primer, R-2, was positive with all eight strains of L . ivanovii tested but was negative with six other species of Listeria, including nine strains of L . monocytogenes, and 20 other taxonomically related bacteria tested . In our PCR method, starting with whole bacterial cells, only 3 h were required for the PCR assay and 1 h for electrophoresis without any additional time for DNA isolation and DNA hybridization . This PCR method detected as few as 4 cells of L . ivanovii in pure cultures and 4-40 cells of L . ivanovii in inoculated and diluted mouse feed, blood, or faeces samples.

Appl Environ Microbiol, 1993 Jan, 59(1), 304 - 8
Differentiation of Listeria monocytogenes and Listeria innocua by 16S rRNA genes and intraspecies discrimination of Listeria monocytogenes strains by random amplified polymorphic DNA polymorphisms; Czajka J et al.; Differences in the 16S rRNA genes (16S rDNA) which can be used to discriminate Listeria monocytogenes from Listeria innocua have been detected . The 16S rDNA were amplified by polymerase chain reaction with a set of oligonucleotide primers which flank a 1.5-kb fragment . Sequence differences were observed in the V2 region of the 16S rDNA both between L . monocytogenes Scott A and L . innocua and between different L . monocytogenes serotypes . Although L . monocytogenes SLCC2371 had the same V2 region sequence as L . innocua, the two species were different within the V9 region at nucleotides 1259 and 1292, in agreement with previous studies (R.-F . Wang, W.-W . Cao, and M.G . Johnson, Appl . Environ . Microbiol . 57:3666-3670, 1991) . Intraspecies discrimination of L . monocytogenes strains was achieved by using the patterns generated by random amplified polymorphic DNA primers . Although some distinction can be made within the L . monocytogenes species by their 16S rDNA sequence, a far greater discrimination within species could be made by generating random amplified polymorphic DNA patterns from chromosomal DNA . By using a number of 10-bp primers, unique patterns for each isolate which in all cases examined differentiate between various L . monocytogenes serotypes, even though they may have the same 16S rRNA sequences, could be generated.

Appl Environ Microbiol, 1993 Jan, 59(1), 144 - 9
Identification and enumeration of Listeria monocytogenes by nonradioactive DNA probe colony hybridization; Datta AR et al.; A plasmid containing the cloned listeriolysin gene of Listeria monocytogenes was used as a probe to identify Listeria strains by DNA colony hybridization . The probe DNA was labeled with horseradish peroxidase in the presence of glutaraldehyde . After the hybridization and wash procedures, the hybrid molecules were detected by luminescence, which resulted from the oxidation of luminol by a horseradish peroxidase-hydrogen peroxide-coupled reaction . Of the 150 Listeria strains and 16 non-Listeria strains examined, the probe hybridized only with L . monocytogenes . The technique was also used to enumerate L . monocytogenes in artificially contaminated foods.

Fundam Appl Toxicol, 1993 Jan, 20(1), 30 - 7
Immunotoxic effects of the color additive caramel color III: immune function studies in rats; Houben GF et al.; Administration of the color additive caramel color III (AC) may cause a reduction in total white blood cell counts in rats due to reduced lymphocyte counts . Beside lymphopenia, several other effects in rat have been described . The effects are caused by the imidazole derivative 2-acetyl-4(5)-(1,2,3,4-tetrahydroxybutyl)imidazole (THI) and occur in rats fed a diet low in vitamin B6 . In the present paper, immune function studies on AC and THI with rats fed a diet low, but not deficient in vitamin B6 are presented and discussed . Rats were exposed to 0.4 or 4% AC or to 5.72 ppm THI in drinking water during and for 28 days prior to the start of immune function assays . Resistance to Trichinella spiralis was examined in an oral infection model and clearance of Listeria monocytogenes upon an intravenous infection was studied . In addition, natural cell-mediated cytotoxicity of splenic and nonadherent peritoneal cells and the antibody response to sheep red blood cells were studied . From the results it is concluded that exposure of rats to AC or THI influenced various immune function parameters . Thymus-dependent immunity was suppressed, while parameters of the nonspecific resistance were also affected, as shown by a decreased natural cell-mediated cytotoxicity in the spleen and an enhanced clearance of L . monocytogenes.

Int J Syst Bacteriol, 1993 Jan, 43(1), 26 - 31
Optical DNA-DNA homology in the genus Listeria; Hartford T et al.; Twenty-three strains of the seven recognized Listeria species were studied by using DNA-DNA optical hybridization . The level of error in the data was low . Our results supported the results of Rocourt et al . (J . Rocourt, F . Grimont, P . A . D . Grimont, and H . P . R . Seeliger, Curr . Microbiol . 7:383-388, 1982), although there was some overlap between Listeria monocytogenes and Listeria innocua . We suggest that there may be more than one cluster in the species L . monocytogenes or the species may form a large spectrum of relatedness . The level of intraspecies homology in L . monocytogenes is very broad, as determined in both this study and other studies.

Infect Immun, 1993 Jan, 61(1), 162 - 9
Listeria ivanovii is capable of cell-to-cell spread involving actin polymerization; Karunasagar I et al.; Listeria ivanovii has been considered to be pathogenic to animals but has rarely been found associated with human infections . It has been claimed that L . ivanovii lacks the actA gene, which in L . monocytogenes encodes a protein required for interaction with host cell actin . Using fluorescence microscopy and electron microscopy, we demonstrate that L . ivanovii can invade mammalian cells, lyse the phagosomal membrane, polymerize host cell actin, reorganize actin to form tails, and spread from cell to cell . However, no DNA homologous to the actA gene could be detected by polymerase chain reaction . Further, L . ivanovii lacks the 90-kDa surface protein which in L . monocytogenes is encoded by actA . Despite the ability to spread from cell to cell, L . ivanovii differed significantly from L . monocytogenes in being unable to form plaques on monolayers of 3T3 fibroblast cells.

Biotherapy, 1993, 6(2), 113 - 24
Free versus liposome-encapsulated muramyl tripeptide phosphatidylethanolamide (MTPPE) and interferon-y (IFN-y) in experimental infection with Listeria monocytogenes; Melissen PM et al.; The effect of free and liposome-encapsulated muramyl tripeptide phosphatidylethanolamide (MTPPE) and interferon-y (IFN-y) on the resistance against Listeria monocytogenes infection in mice was investigated . It was shown that administration of MTPPE or IFN-y at 24 h before bacterial inoculation led to increased resistance against L . monocytogenes infection in terms of a decrease in bacterial numbers in liver and spleen . Encapsulation of MTPPE and IFN-y in liposomes increased their efficacy 33- or 66-fold, respectively . In addition, liposomal encapsulation led to a more rapid decrease in bacterial numbers . The immunomodulator to lipid ratio appeared to be very important in the antibacterial effect of LE-MTPPE and LE-IFN-y . When nontherapeutic doses of liposome-encapsulated MTPPE or IFN-y were administered in a larger amount of lipid (so at higher lipid: immunomodulator ratio), these doses became effective . Exposure of macrophages in monolayer infected with L . monocytogenes in vitro to MTPPE had no effect, whereas exposure to IFN-y only led to growth inhibition of the intracellular bacteria . However, incubation of macrophages with a combination of MTPPE and IFN-y resulted in killing of the intracellular bacteria . Exposure of macrophages in vivo to both immunomodulators in combination can be effected by using liposomes as carriers . It was observed that administration of MTPPE and IFN-y co-encapsulated in liposomes resulted in a synergistic enhanced antibacterial resistance against L . monocytogenes . Both reactive oxygen and nitrogen intermediates seemed to play a role in the killing of L . monocytogenes by macrophages activated with a combination of MTPPE and IFN-y.

Rev Neurol (Paris), 1993, 149(1), 61 - 4
{Weber syndrome caused by Listeria abscess}; Milandre L et al.; A 63-year old diabetic man presented with left Weber's syndrome and meningitic syndrome . CSF examination showed moderate lymphocytic pleocytosis and elevated proteins with normal glucose content and sterile culture . Blood cultures yielded Listeria monocytogenes and the patient received ampicillin . While his neurological condition had partially improved, he died of heart failure . Several mesencephalic abscesses were found at autopsy.

Res Microbiol, 1993 Jan, 144(1), 47 - 54
Comparison of "Gen-Probe" DNA probe and PCR for detection of Listeria monocytogenes in naturally contaminated soft cheese and semi-soft cheese; Niederhauser C et al.; A comparison was made of three approaches for the detection of Listeria monocytogenes in naturally contaminated soft cheese and semi-soft cheese after enrichment . Enrichment broths were tested by plating them onto different selective agars, by "Gen Probe" DNA hybridization and by the polymerase chain reaction (PCR) . Based on two-step enrichment, all three approaches showed high specificities (90% or more) in detecting L . monocytogenes . In contrast, the sensitivity of the Gen-Probe test was low (33% or less), whereas high sensitivities were obtained with selective plating and PCR (83% or more) . Based on one-step enrichment, specificities again were high for selective plating and PCR assay (100%), whereas for the Gen-Probe assay the specificity was lower (88% or more) . The best sensitivities were observed with selective plating (67%) and PCR (75%) . In terms of sensitivity, specificity and analysis time, PCR applied to a two-step enrichment was the most powerful assay for detecting L . monocytogenes in soft and semi-soft cheese.

Microbios, 1993, 76(309), 231 - 5
Observations on listerias at dysgenesic concentrations of NaCl; Espejo J et al.; Interesting morphological and Gram-stain changes of listerias in relationship to the concentration of NaCl were observed . When incubated at 23 degrees C at a concentration of 6% (w/v) the listerias tended to form chains, and in concentrations of 10-11% NaCl they presented aberrant forms as long filaments, some of them forming circles, and they lose affinity for Gram stain . Similar changes were observed, but at different concentrations of NaCl, when incubation was at 37 degrees C.

Dev Biol Stand, 1993, 80, 119 - 21
Surveillance for lesions of bovine spongiform encephalopathy in U.S . cattle; Miller LD et al.; The appearance of bovine spongiform encephalopathy (BSE) as a new disease of cattle in 1985-1987 increased worldwide interest in various aspects of human and animal spongiform encephalopathies . In the United States, a part of the surveillance effort has been directed toward prospective examination of bovine brain specimens for lesions of BSE . One focus area has been to obtain specimens from cattle that (1) are two years of age or older, (2) have documented signs of neurologic disease, and (3) have received protein supplement as a substantial part of the i.v . ration . Another focus area has been to examine rabies-suspect cases that were rabies-negative . A third area has been to obtain the results of bovine neuropathology examinations being conducted at other state and regional laboratories . Specimens have been obtained by direct submission and by referral from other public health and veterinary diagnostic laboratories . Many of the cases have been classified as having (1) inflammatory lesions such as listeriosis, pseudorabies, brain abscesses and inflammation of undetermined cause, (2) degenerative lesions such as polio-encephalomalacia, lead poisoning, Wallerian degeneration, siderocalcinosis, and lipofuscinosis, (3) neoplastic lesions such as meningioma and Schwannoma, and (4) no significant findings . Other case results were reported as inflammation or no significant findings . Of the 459 cases reported here none has contained lesions with the characteristics and distribution typical of BSE.

Acta Vet Scand, 1993, 34(2), 145 - 9
Isolation of Listeria monocytogenes from goat cheese associated with a case of listeriosis in goat; Eilertz I et al.; Listeria monocytogenes was isolated from the brain of a goat, which was euthanized due to listeriosis . A few weeks later a similar subtype of L . monocytogenes was isolated from an on-farm manufactured fresh cheese which did not contain any milk from the goat which had suffered from listeriosis . A similar subtype was also found on 1 of the shelves in the refrigerator where cheeses were stored . Prior to the onset of listeriosis, 1 fresh cheese had been made of milk from the actual goat, which may have excreted L . monocytogenes in her milk . Thus, the cheese made of this milk may have contaminated the shelves in the refrigerator which then has served as a Listeria reservoir for new cheeses during several weeks.

Neuroradiology, 1993, 35(7), 495 - 6
MRI of an abscess of the cervical spinal cord in a case of Listeria meningoencephalomyelitis; King SJ et al.; A case of Listeria meningoencephalomyelitis is described and the MRI appearances of an abscess of the cervical spinal cord are presented . The MRI appearances did not allow a definitive diagnosis before death.

Med Dosw Mikrobiol, 1993, 45(1), 55 - 9
{Protective action of anti-listeria IgG}; Chmiela M et al.; It was found that single injection into mice of 70 micrograms IgG against Listeria innocua protected them against lethal action of virulent cell of L . monocytogenes, if antibodies were injected 1-3 weeks before infection . Immune IgG did not exert the protective effect when injected one day before infection . Mice T lymphocytes receiving immune IgG three weeks before infection, exhibited increased ability to direct interactions (cluster formation) with dendritic cells presenting Listeria antigen (LA) . At the same time, sera obtained from these animals were blocking the reaction of indirect haemagglutination occurring between antibodies against L . innocula and LA-covered sheep erythrocytes . These results suggest that anti-listerial IgG are inducing in mice production of anti-idiotypic antibodies . Most probably, some of these immunoglobulins imitate determinants of Listeria antigens, copying their three-dimensional structure . They could activate T cells specific against bacterial antigens (1st signal of activation) . Introduction of virulent L . monocytogenes cells into mice possessing T cells activated by anti-idiotypic antibodies, could create a second antigenic signal, resulting in intensive elimination of bacteria by mechanisms of specific cellular immunity.

Med Dosw Mikrobiol, 1993, 45(1), 51 - 4
{Weakness of cellular response to Listeria antigens in pregnant mice}; Klink M et al.; It was found that pregnant mice exhibit increased susceptibility to lethal action of Listeria monocytogenes, although there was no correlation between increase of susceptibility of animals to lethal effect of bacteria and weakening of elimination of microorganisms from the spleen . Increased susceptibility of animals to listeriosis was accompanied by weakening of some parameters of cellular immunity . In pregnant mice of strains C57Bl/6, naturally resistant to infections, inhibition of II-1 by macrophages was found which at the same time exhibited depression of chemotaxis . Weakening of these macrophage functions did not influence the development of delayed hypersensitivity to Listeria antigen (LA) in C57Bl/6 mice--the reaction which was suppressed in pregnant mice of A/J strain which is characterized by natural susceptibility to listeriosis . Inhibition of development of delayed hypersensitivity to LA in A/J pregnant mice was caused by defective function of dendritic cells and T lymphocytes . Dendritic cells of A/J pregnant mice exhibited limited ability of presentation of LA to immune T lymphocytes isolated from animals infected with L . monocytogenes or L . innocula . On the other hand, immune T cells of A/J mice cultured with LA exhibited inhibition of proliferation and production of MIF.

Leuk Lymphoma, 1993, 10 Suppl, 139 - 45
Nucleoside analogs in treatment of chronic lymphocytic leukemia; Keating MJ et al.; The nucleoside analogs fludarabine monophosphate, 2-chlorodeoxyadenosine, and 2-deoxycoformycin (pentostatin) all have activity in chronic lymphocytic leukemia . The most widely studied drug is fludarabine which is able to obtain complete or partial responses in more than 50% of previously treated patients . The response rate is 44% for 2-CDA and approximately 25% for pentostatin . Fludarabine has also been used to treat patients as initial therapy, and has resulted in overall response rate of 79% with 75% of the patients achieving complete remission . The NCI and International Working Group for CLL criteria for complete remission allow for persistent nodules or lymphoid infiltrates in the bone marrow biopsy . Studies have now demonstrated persistent lymphoid aggregates are associated with a shorter time to progression for responders but no survival disadvantage . There is a strong association of documented refractoriness to alkylating agents with probability of response to fludarabine and also survival . The major morbidity associated with the use of these drugs are infections, which, in some circumstances, are associated with neutropenia but in other circumstances are probably related to the hypogammaglobulinemia and T-cell immunodeficiency which are part of the disease . The T-cell immunodeficiency is aggravated by the nucleoside analogs . Even after discontinuation of therapy the immunodeficiency as measured by CD4 cell number is sustained for 12 to 24 months . Opportunistic organisms such as herpes simplex, herpes zoster, Listeria monocytogenes, and pneumocystis carinii are being noted in patients treated with these agents . The potency of these drugs and low incidence of toxicities to other organs suggests that they will be effectively combined with other agents.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunology, 1993 Jan, 78(1), 22 - 7
Characterization of T-cell receptor gamma delta T cells appearing at the early phase of murine Listeria monocytogenes infection; Matsuzaki G et al.; It has been shown that T-cell receptor (TcR) gamma delta + CD4- CD8- T cells increase in number and have an important role in early protection in murine Listeria monocytogenes infection . In this report, to characterize further the phenotype of the gamma delta T cells in listeriosis, we analysed V region gene usage and in vitro antigen recognition of the TcR gamma delta T cells in the peritoneal cavity of mice at the early phase after i.p . infection with a sublethal dose of L . monocytogenes . The gamma delta T cells predominantly expressed V delta 6 which has been reported to be expressed by TcR gamma delta-bearing foetal thymocyte hybridomas specific to mycobacterial and self heat-shock protein (hsp) 60 . These early appearing CD3+ CD4- CD8- T cells in Listeria-infected mice, which were reported to be TcR gamma delta T cells, increased in proportion and in size by in vitro stimulation with recombinant hsp 60 from Mycobacterium bovis and purified protein derivative from M . tuberculosis but not by stimulation with heat-killed L . monocytogenes . A 65,000 MW molecule was detected in the lysate of viable L . monocytogenes but not in the lysate of heat-killed L . monocytogenes by a monoclonal antibody (mAb) raised against mycobacterial hsp 60 . These results suggest that the V delta 6-bearing peripheral gamma delta T cells are activated by recognizing listerial hsp 60 expressed by viable L . monocytogenes . The hsp 60-reactive V delta 6-bearing T cells may have an important role in protection against L . monocytogenes and other parasites that express hsp 60 at high level.

Immunology, 1993 Jan, 78(1), 28 - 34
T cells expressing both L-selectin and CD44 molecules increase in number in peritoneal exudate cells and in vitro-stimulated spleen cells from mice immunized intraperitoneally with Listeria monocytogenes; Li XY et al.; L-selectin, which was first reported as MEL-14 antigen in mice, is a type of animal lectin and expressed on lymphocytes, neutrophils and macrophages . L-selectin has been reported to be a homing receptor of lymphocytes to peripheral lymph nodes and to have an important role in initial adhesion of lymphocytes and neutrophils to endothelial cells activated by inflammatory cytokines . On the other hand, it has been reported that naive T cells express L-selectin while memory T cells and in vitro antigen-stimulated T cells lose its expression . If all memory T cells lack L-selectin, trafficking of memory T cells into inflammatory sites would be difficult . To know whether all memory T cells lack L-selectin expression, kinetics of expression of L-selectin was analysed on memory T-cell subsets, which are detected by expression of CD44, in mice after intraperitoneal immunization with a sublethal dose of viable Listeria monocytogenes . T cells expressing both L-selectin and CD44 were detected in splenocytes and peritoneal exudate cells (PEC) from untreated mice, though at low levels . L-selectin+ CD44+ T cells increased in PEC, which are known to be highly enriched in antigen-primed T cells, and reached maximum level on day 14 after immunization . Furthermore, we found increases not only of L-selectin- CD44+ but also of L-selectin+ CD44+ T cells by in vitro Listeria antigen stimulation of Listeria-immune spleen cells on day 14 . These results showed that T cells expressing both L-selectin and CD44 increase after antigen stimulation in vivo and in vitro . The L-selectin+ CD44+ T cells may be a subset of memory T cells which retain their capacity of trafficking to inflammatory sites.

Vet Med (Praha), 1992 Dec, 36(12), 745 - 50
{Listeria monocytogenes in food}; Mickova V; As in recent years laboratory diagnostics of listeria has become part of food microbiology, the frequency of occurrence of the bacteria Listeria monocytogenes has been followed in various kinds of foods for a year . A total of 51 strains of L . monocytogenes (7.2%) was isolated from 700 kinds of samples (raw milk, pasteurized milk, meat surface, poultry, cheeses, thermally not treated meat products, food--industry machinery) . As can be seen in Tab . I, the highest number of strains was isolated from meat surfaces (13.5%), followed by meat--industry machinery (12.72%), poultry (10%) and cheeses (5%) . The lower numbers of strains were found out in thermally not treated meat products (3.8%) and in raw milk (3.3%) . Pasteurized milk did not contain any strains . Our findings in raw milk (3.3%) and in pasteurized milk (0) are in agreement with the data cited e . g . by authors from the USA (Lovett et al., 1987), who mention the value of 4.2% in raw milk and the zero value in pasteurized milk . The percentage of strains monitored in cheeses (5%) can be evaluated as low as the assortment of investigated cheeses was small (all strains were isolated from soft ripening cheeses) . German authors (Tham et al., 1988) speak about the 2.5% percentage of L . monocytogenes strains; this is in keeping with our findings . The findings in thermally not treated meat products (3.8%) can be evaluated as low although the number of strains found in raw meat was high.(ABSTRACT TRUNCATED AT 250 WORDS)

Appl Environ Microbiol, 1992 Dec, 58(12), 4055 - 9
Assessment of the Accuprobe Listeria monocytogenes culture identification reagent kit for rapid colony confirmation and its application in various enrichment broths; Ninet B et al.; The Accuprobe Listeria monocytogenes Culture Identification Reagent Kit, a nonradioactive probe, was evaluated as a colony confirmation test and in different selective or nonselective enrichment broths . The probe was 100% sensitive and 100% specific when applied to isolated colonies . The minimal detection limit in physiological saline was established to be about 10(5) CFU of L . monocytogenes . Hybridization done directly in broths seeded with L . monocytogenes showed variable results . Three nonselective broths (Todd-Hewitt broth, brain heart infusion broth, and tryptic soy broth) and one selective broth (FDA) gave positive reactions at an inoculum of 5 x 10(6) CFU, whereas two other selective broths (UVM, and PALCAMY) gave negative reactions with up to 10(8) and 10(9) CFU . In FDA broth, the level of detection of L . monocytogenes was not modified by the presence of other organisms in mixed cultures.

Appl Environ Microbiol, 1992 Dec, 58(12), 3991 - 4000
Determination of virulence of different strains of Listeria monocytogenes and Listeria innocua by oral inoculation of pregnant mice; Lammerding AM et al.; A pregnant mouse model was developed to follow the course of infection after peroral inoculation with six different strains of Listeria monocytogenes and one strain of Listeria innocua . Tissues were sampled and analyzed by microbiologic and histologic methods for 5 days postinoculation . In gnotobiotic pregnant BALB/c mice, L . monocytogenes Scott A (SA), serotype 4b, colonized the gastrointestinal tract, translocated to the livers and spleens of mice by day 1 postinoculation, and multiplied in these tissues until day 4 . Infection of the placental tissues occurred by days 3 and 4 and was followed by infection of the fetuses . Little damage of colonic and cecal tissues was evident by histologic examination . Livers and spleens showed a cellular immune response; a similar immune response was not detected in the placentas or fetuses . A rough variant of L . monocytogenes SA which was as virulent as the parent strain in mice when injected intraperitoneally was less virulent perorally and did not consistently infect the fetuses . L . monocytogenes ATCC 19113, serotype 3a, did not colonize the gastrointestinal tract, nor was it isolated from any internal tissue . L . monocytogenes strains of serotypes 1/2a and 1/2b behaved like the SA strain in this mouse model . L . innocua colonized the gastrointestinal tract and translocated to the livers and spleens but did not survive in these organs and rapidly disappeared without infecting placental and fetal tissues . In comparison with gnotobiotic mice, conventional pregnant mice inoculated with L . monocytogenes strains showed less consistent infection . These results suggest that the gnotobiotic pregnant mouse is a useful model for detecting differences in virulence relating to colonization, invasiveness, and uteroplacental infection which cannot be detected by intraperitoneal inoculation of mice.

Appl Environ Microbiol, 1992 Dec, 58(12), 3959 - 63
Effect of sodium chloride on the intracellular solute pools of Listeria monocytogenes; Patchett RA et al.; The concentrations of intracellular solutes in Listeria monocytogenes were examined in cells grown at various concentrations of NaCl . At 5% NaCl, cells contained elevated concentrations of potassium and glycine betaine compared with concentrations in cells grown without NaCl . At 7.5% NaCl, cells contained increased concentrations of K+, glycine betaine, glycine, alanine, and proline . Only glycine betaine, choline, or glycine promoted growth on a solidified defined medium containing 4% NaCl; there was no growth at higher concentrations of NaCl in the defined medium.

J Bacteriol, 1992 Dec, 174(24), 8166 - 71
Structural and functional properties of the p60 proteins from different Listeria species; Bubert A et al.; The major extracellular protein p60 of Listeria monocytogenes seems to be required for this microorganism's adherence to and invasion of 3T6 mouse fibroblasts but not for adherence to human epithelial Caco-2 cells . Western blot analysis with polyclonal antibodies against p60 of L . monocytogenes indicated the presence of cross-reacting proteins in the culture supernatants of all Listeria species . Protein p60 of L . monocytogenes could restore adhesion of the L . monocytogenes mutant RIII (impaired in the synthesis of p60) to mouse fibroblasts more efficiently than that of Listeria grayi . The amino acid sequences of the p60-related proteins of L . innocua, L . ivanovii, L . seeligeri, L . welshimeri, and L . grayi indicated highly conserved regions of about 120 amino acids at both the N-terminal and the C-terminal ends . The middle portions of these proteins, consisting of about 240 amino acids, varied considerably . These parts include the repeat domain consisting of repetitions of Thr (T) and Asn (N) which was present only, albeit in different arrangements, in the p60 proteins of L . monocytogenes and L . innocua . The p60-related proteins of L . grayi, L . ivanovii, L . seeligeri, and L . welshimeri each contained an insertion of 54 amino acids which was absent in the p60 proteins of L . monocytogenes and L . innocua.

Postgrad Med, 1992 Dec, 92(8), 191 - 3
Listerial meningitis . Which patients are vulnerable?
Ashinsky D.
The physician's index of suspicion for infection with Listeria monocytogenes should be elevated if a patient presents with symptoms of meningitis and has impaired cell-mediated immunity . Although diagnosis is aided by detection of an elevated white blood cell count and protein level in the cerebrospinal fluid, it requires isolation of the organism from the cerebrospinal fluid . Appropriate antibiotic treatment leads to recovery in most cases.

Infect Immun, 1992 Dec, 60(12), 5107 - 12
Endogenous tumor necrosis factor alpha is required for enhanced antimicrobial activity against Toxoplasma gondii and Listeria monocytogenes in recombinant gamma interferon-treated mice; Langermans JA et al.; In vitro studies have shown that macrophages stimulated with recombinant gamma interferon (rIFN-gamma) produce tumor necrosis factor alpha (TNF-alpha), which in an autocrine fashion activates these cells . The aim of the present study was to determine whether endogenously formed TNF-alpha also is required for rIFN-gamma-induced macrophage activation and enhanced antimicrobial activity in vivo . After an intraperitoneal injection of rIFN-gamma into CBA/J mice, their peritoneal macrophages released enhanced amounts of NO2- and inhibited the intracellular proliferation of Toxoplasma gondii . Injection of neutralizing antibodies against TNF-alpha simultaneously with the rIFN-gamma completely inhibited both the release of NO2- by macrophages and their toxoplasmastatic activity . Similar results were observed after intraperitoneal injection of a competitive inhibitor of L-arginine, NG-monomethyl-L-arginine, together with rIFN-gamma, demonstrating that in vivo L-arginine-derived reactive nitrogen intermediates are essential for the induction of toxoplasmastatic activity . Intravenous injection of rIFN-gamma inhibited the growth of Listeria monocytogenes in the livers and spleens of mice; this effect was abrogated by antibodies against TNF-alpha . Intravenous injection of a large dose of rTNF-alpha resulted in a decrease in the number of bacteria in the liver and spleen, but an injection of rIFN-gamma and rTNF-alpha did not result in enhanced inhibition of the proliferation of L . monocytogenes . Together, the results of the present study are the first to demonstrate that endogenous TNF-alpha is required in vivo for the expression of macrophage activation with respect to the release of reactive nitrogen intermediates and toxoplasmastatic activity and for enhanced listericidal activity in the livers and spleens of mice stimulated with rIFN-gamma.

Lett Appl Microbiol, 1992 Dec, 15(6), 248 - 52
Ultra sensitive detection of Listeria monocytogenes in milk by the polymerase chain reaction (PCR); Starbuck MA et al.; The polymerase chain reaction (PCR) has been used to detect Listeria monocytogenes in whole milk at a level of 0.1 cfu per 30 ml . This high degree of sensitivity has been achieved following enzymatic digestion, polysulphonone membrane filtration and amplification of a nucleotide sequence within the promoter region of hlyA . Key elements of the procedure are the absence of enrichment culture and a complete solubilization of the membrane filter, ensuring total nucleic acid recovery . The simplicity of the protocol coupled with high sample volumes and exquisite sensitivity extends the relevance of PCR within food and environmental microbiology.

Proc Natl Acad Sci U S A, 1992 Dec 1, 89(23), 11612 - 6
CD8 T cells can protect against an intracellular bacterium in an interferon gamma-independent fashion; Harty JT et al.; Specific T-cell immunity to Listeria monocytogenes is thought to occur through the action of lymphokines which activate phagocytes to ingest and kill microorganisms . Interferon gamma (IFN-gamma) has been shown to be an effective mediator of this type of macrophage activation in vivo and in vitro . The monoclonal antibody H22.1 efficiently neutralizes endogenous IFN-gamma, exacerbates disease in a mouse model of L . monocytogenes infection, and inhibits the in vivo protective activity of a Listeria antigen-specific CD4 T-cell line . In contrast, in vivo protection by Listeria-immune CD8 T cells is not inhibited by the neutralizing anti-IFN-gamma monoclonal antibody . These results suggest that CD8 T cells can protect against an intracellular pathogen in an IFN-gamma-independent manner.

Int Immunol, 1992 Dec, 4(12), 1413 - 8
Induction of protective CD8+ T lymphocytes by an attenuated Listeria monocytogenes actA mutant; Goossens PL et al.; We tested the ability of an attenuated actA mutant of Listeria monocytogenes to induce protective immunity in mice . This mutant can enter and multiply in the cytosol of the infected host cell, but is deficient in actin-dependent cell-to-cell spread . It was found to be of attenuated virulence for inbred C3H mice: the LD50 after i.v . injection was 1000-fold higher than that of the wild-type strain . Mutant bacteria multiplied up to the fourth day in the liver, but only for 1 day in the spleen . A single infection with the maximum sublethal dose of the actA mutant induced long-lasting immunity; the LD50 of virulent wild-type L . monocytogenes increased 100-fold and growth of wild-type L . monocytogenes was controlled in liver and spleen of these mice . The presence of Listeria-reactive T cells in spleen of C3H mice infected 7 days previously with the actA mutant was monitored, through their ability to protect naive syngeneic recipients against wild-type L . monocytogenes . Protection was mainly conferred by Thy-1+ CD8+ T lymphocytes; depletion of CD4+ T cells had no significant effect on the level of transferred protection . Such attenuated mutants may be used to develop live vector vaccines for delivery of heterologous proteins into the cytosol, thereby favoring the induction of a CD8+ T cell response.

Commun Dis Rep CDR Rev, 1992 Nov 6, 2(12), R142 - 4
Listeriosis surveillance: 1991; Newton L et al.; A total of 130 cases of listeriosis was reported in England, Wales and Northern Ireland in 1991 . This represents a slight increase on the 1990 total of 118 reports but a marked decline compared with the peak incidence of reporting of 291 in 1988, which was part of an upsurge of cases between 1987 and mid 1989 . Two epidemiological features of note in 1991 were the reappearance of a late summer-autumn peak in cases (commonly seen prior to 1987) and an increase in the number of reports among younger patients and children . The decline in listeriosis observed during the second half of 1989, which followed government health warnings about the consumption of pate, and the continued low level of reporting since 1989 may be due to the disappearance of a common food source . However, in the light of the recent outbreak of listeriosis in France it is important that diagnostic vigilance and warnings about high risk foods are maintained.

Antimicrob Agents Chemother, 1992 Nov, 36(11), 2375 - 80
Comparison of the antibacterial efficacies of ampicillin and ciprofloxacin against experimental infections with Listeria monocytogenes in hydrocortisone-treated mice; van Ogtrop ML et al.; The efficacies of ciprofloxacin and ampicillin against Listeria monocytogenes in an immunosuppressed mouse model of listeriosis were compared . Immunosuppression was achieved by administration of 2.5 mg of hydrocortisone acetate daily . Both ciprofloxacin and ampicillin were effective in reducing the number of viable L . monocytogenes cells in the liver and spleen . After treatment with 100 mg of ampicillin per kg of body weight every 6 h for 3 days, virtually no L . monocytogenes could be recovered from the livers and spleens of the mice . In contrast, after treatment with 100 mg of ciprofloxacin per kg every 6 h for 3 days, a geometric mean of 5 x 10(4) CFU of L . monocytogenes was recovered from the spleens and 1 x 10(5) CFU was recovered from the livers of the mice . Results of the study show that the antibacterial efficacy of ampicillin is far superior to that of ciprofloxacin in our animal model of listeriosis.

Nutrition, 1992 Nov-Dec, 8(6), 426 - 9
Enriched feeding formula and immune responses and outcome after Listeria monocytogenes challenge in mice; Chandra RK et al.; Immunocompromised malnourished patients are at high risk of developing serious opportunistic infection . This study examined the effect of feeding a special nutrient-enriched formula (Immun-Aid) on immune responses and mortality in mice challenged with Listeria monocytogenes . Two protocols were followed . In the first protocol, the animals were challenged with microorganisms when the experimental formula was introduced as the sole source of their nutrition . There was no significant effect on total T-lymphocyte number, but the proportion of helper T cells increased by day 7, resulting in a higher helper/suppressor (H/S) T lymphocyte ratio as well . Response to the mitogen phytohemagglutinin (PHA) was slightly higher on day 3 but came down and was comparable with that of control animals by day 7 . Natural killer cell activity was slightly higher on day 7 . Other immunologic parameters were unchanged . There was no significant difference in mortality between the two groups . In the second protocol, the animals were fed the experimental diet for 7 days before the infectious challenge . There was a slight increase in the total number of T lymphocytes on day 7 . The numbers of helper and suppressor T lymphocytes were unchanged, but H/S was slightly higher on day 3 in the experimental group . Response to PHA was again higher on day 3 but plateaued on day 7 . Natural killer cell activity was not altered . Mortality after infectious challenge was slightly but significantly decreased in the group of animals fed the enriched special formula . These results indicate a slight enhancement of selected parameters of immunity in mice fed the specially enriched formula and show that prior feeding with this formula for several days may partly protect against infectious challenge, resulting in reduced mortality.

Q J Med, 1992 Nov-Dec, 85(307-308), 911 - 5
Listeria monocytogenes meningitis in previously healthy adults: long-term follow-up; Zuniga M et al.; A few cases of Listeria meningitis in healthy individuals have been recorded in the world literature . The lack of a prolonged follow-up in most of these cases makes it difficult to exclude the existence of an underlying disease . The clinical and CSF data of four previously healthy patients with meningitis due to Listeria monocytogenes are presented . These patients were followed prospectively over 2-6 years; during this time none developed any disease associated with immunosuppression, including HIV infection, and none died . Listeria meningitis in an otherwise healthy person is, therefore, not always a sign of underlying immunosuppressive disease, and does not necessarily have a poor prognosis.

Appl Environ Microbiol, 1992 Nov, 58(11), 3508 - 13
Production of bacteriocin inhibitory to Listeria species by Enterococcus hirae; Siragusa GR; A bovine intestinal bacterial isolate, identified as Enterococcus hirae, was found to produce a bacteriocin (designated hiraecin S) inhibitory to Listeria monocytogenes and other Listeria spp . Identification to species level was determined by comprehensive biochemical and morphological tests which were verified by DNA-DNA homology assays . The antimicrobial agent was inactivated by pronase and papain and was insensitive to catalase . The antimicrobial activity was not due to hydrogen peroxide or acid formation, nor was lysozyme or muramidase activity observed in cell-free bacteriocin preparations . Inhibition of selected gram-negative bacteria was not observed . Other enterococci were sensitive to the bacteriocin, and except for Listeria spp., no other gram-positive bacteria tested were inhibited.

Appl Environ Microbiol, 1992 Nov, 58(11), 3443 - 7
Discrimination of Listeria monocytogenes from other Listeria species by ligase chain reaction; Wiedmann M et al.; A ligase chain reaction assay based on a single-base-pair difference in the V9 region of the 16S rRNA gene (16S rDNA) was developed to distinguish between Listeria monocytogenes and other Listeria species . For this purpose, two pairs of primers were designed, with one primer of each pair being radioactively labeled . The ligated product was separated from the primers by denaturing polyacrylamide gel electrophoresis and then detected by autoradiography . To achieve a higher sensitivity, the 16S rDNA was initially amplified by polymerase chain reaction prior to the ligase chain reaction . The ligase chain reaction was tested on 19 different Listeria species and strains and proved to be a highly specific diagnostic method for the detection of L . monocytogenes.

Immunology, 1992 Nov, 77(3), 354 - 61
Intravenous injection of interferon-gamma inhibits the proliferation of Listeria monocytogenes in the liver but not in the spleen and peritoneal cavity; Langermans JA et al.; In the present study the effects of intravenous administration of recombinant interferon-gamma (IFN-gamma) on both the proliferation of Listeria monocytogenes in the liver and spleen of mice and the listericidal activity of their peritoneal macrophages were investigated . A single intravenous injection of 1 x 10(6) U or three injections of 2 x 10(5) U recombinant IFN-gamma (rIFN-gamma) induced optimal activation of resident and exudate peritoneal macrophages, as judged by their ability to inhibit the intracellular proliferation of Toxoplasma gondii and their enhanced release of H2O2 and NO2- . The rate of intracellular killing of L . monocytogenes by the rIFN-gamma-activated resident and exudate macrophages was not higher than that by resident macrophages . Addition of 10 ng lipopolysaccharides (LPS) to the rIFN-gamma also did not enhance the bactericidal activity of the activated peritoneal macrophages . The decrease in the number of L . monocytogenes in the peritoneal cavity of mice that had received an i.p . injection of 1 x 10(4) U rIFN-gamma was similar to that in control mice . Intravenous administration of 1 x 10(5) rIFN-gamma activated cells in the liver, as indicated by the increased expression of Ia antigen, and reduced the rate of proliferation of L . monocytogenes in the liver relative to that in control mice when 0.1 LD50 or 1 LD50 L . monocytogenes were injected . However, when 10 LD50 L . monocytogenes were administered there was no effect on their proliferation . The number of L . monocytogenes found initially in the spleen of rIFN-gamma-treated mice was 20-30% of that in the spleen of control mice, but the rate of proliferation of L . monocytogenes was not reduced . These divergent results for the proliferation of L . monocytogenes in the liver, spleen and peritoneal cavity indicate that cells other than macrophages and/or as yet unknown local factors play an important role in the listericidal activity.

Prostaglandins Leukot Essent Fatty Acids, 1992 Nov, 47(3), 231 - 8
Cytokine modulation of immune activation associated suppression of macrophage cyclooxygenase activity in vivo; Beckerman KP et al.; Intraperitoneal infection with Listeria monocytogenes (LM) results in activation of the peritoneal macrophage population which displays increased surface expression of major histocompatibility (MHC) Class II (Ia) antigen and markedly suppressed prostaglandin (PG) synthesis . We demonstrate here that this decrease in PG production is also seen after treatment by mitogen (Con A) and endotoxin (LPS), and can be explained by reduced cyclooxygenase activity in these cell populations . We show that, whereas Ia expression was augmented at all doses of LM and Con A tested, it displayed a biphasic response to LPS in vivo: increase at the lowest dose and inhibition at higher doses . In order to identify possible endogenous mediators of these responses, we used highly purified preparations of recombinant murine (rMu) cytokines and neutralizing cytokine specific monoclonal antibodies (MAbs) to examine whether interferon-gamma (IFN-gamma) and/or tumor necrosis factor (TNF) down-regulate macrophage cyclooxygenase activity in vivo . We found that IFN-gamma induced Ia expression but had no effect on PG secretion . In contrast, TNF-alpha suppressed PG synthesis and inhibited Ia surface expression . Similarly, in our model of Con A-induced peritoneal macrophage activation, pretreatment of animals with a neutralizing MAb to rMuIFN-gamma completely blocked the induction of Ia positive macrophages by Con A but did not affect Con A-dependent suppression of PG synthesis . Pretreatment with MAb to TNF had no effect on Con A-induced Ia levels, but significantly inhibited suppressed PG synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcohol, 1992 Nov-Dec, 9(6), 459 - 63
Effects of ethanol on parameters of cellular immunity and host defense mechanisms to infectious agents; Jerrells TR et al.; Results of several studies have associated ethanol abuse with an increased incidence of infections, including opportunistic infections and those caused by microorganisms, as well as of certain types of cancer . Research findings from several laboratories clearly indicate that one possible mechanism in this association is an effect of ethanol on the immune system . We have developed an animal model fo ethanol ingestion in a liquid diet to study the effects of ethanol on immune responses . In most of the studies, we have used a pair-feeding design in which control animals are given a liquid diet that is isocaloric to the ethanol diet by the addition of either sucrose or dextran-maltose . Here, we discuss data obtained from in vivo studies of cellular function . We have studied the effects of ethanol on activation of T lymphocytes in vivo after intravenous injection of monoclonal antibody to CD3 . The stimulation of cells in the spleen was assessed by measuring levels of cytokine RNA . We have also assessed the ability of animals to respond to a sublethal dose of Listeria monocytogenes to determine whether ethanol alters host defense mechanisms . Our findings indicate that ethanol ingestion reduced the ability of mice to respond to anti-CD3 and to resist infection with a bacterium that predominantly infects the liver.

An Med Interna, 1992 Nov, 9(11), 560 - 2
{Fulminant meningoencephalitis due to Listeria monocytogenes}; Manzanares R et al.; We present a case of meningoencephalitis due to Listeria monocytogenes type IV in a patient in which the diagnosis of small-cells malignant diffuse non-Hodgkin's lymphoma had been established . He was hospitalized with vague clinical manifestations and without showing any neurological focus . Hours later, he presented clinical brain stem semiology . Within a 24-hour period, Listeria monocytogenes was isolated from blood and cephalorhachidian fluid (being the first time that this microorganism had been isolated for the past 20 years in our laboratory) . The patient evolved to a state of coma, with Cheyne-Stokes's respiration, abolition of pupillary reflexes, decerebration position and exitus laetalis . The affection of the central nervous system has been fully documented . However, its fulminant presentation, as in the case that we present here, is less frequent, although it has been described in the literature by other authors, like Finegold et al., with cases in which the interval between the onset of the neurological focality and death ranged from 8 to 16 hours . The antibiogram showed a wide sensibility to several groups of drugs, despite the fast evolution of the disease that prevented the modification of the initial antibiotherapy (Vancomicine and imipenem).

Neurologia, 1992 Nov, 7(9), 270 - 3
{Rhombencephalitis caused by Listeria monocytogenes}; Prieto JM et al.; The observation of an abscess in the brain stem and cerebellum due to Listeria monocytogenes is presented . The patient was a 55 year old diabetic, alcoholic, gastrectomized male in whom a febrile and meningeal syndrome developed . Three days later he had a progressive unilateral dysfunction of the cranial nerves . The cerebrospinal fluid showed pleocytosis of the polymorphonuclear cells, an increase in proteins and low glucose in relation with the glycemia . No parenchymatous lesion was observed upon emergency computerized tomography . Magnetic resonance imaging showed a hyper-signal lesion in the brain stem and cerebellum with a contrast enhancement in ring . Following antibiotic treatment the clinical evolution of the patient was favorable with slight focal sequelae persistent at discharge . A review of the epidemiology, clinical manifestations and treatment of this infection is carried out.

J Exp Med, 1992 Nov 1, 176(5), 1439 - 47
Gemfibrozil enhances the listeriacidal effects of fluoroquinolone antibiotics in J774 macrophages; Rudin DE et al.; J774 macrophage-like cells express organic anion transporters that promote the efflux of fluoroquinolone antibiotics such as norfloxacin (NFX) from these cells . Gemfibrozil (GFZ) blocks organic anion transport in J774 cells, thereby facilitating the intracellular accumulation of NFX (Cao, C., H.C . Neu, and S.C . Silverstein . 1991 . J . Cell Biol . 115:467a {Abstr.}) . To determine whether GFZ enhances the efficacy of fluoroquinolone antibiotics against intracellular bacterial pathogens, J774 cells were infected with Listeria monocytogenes and incubated in medium containing a fluoroquinolone antibiotic in the presence or absence of GFZ . Intracellular growth of L . monocytogenes was evaluated by lysing J774 cells and assaying for colony-forming units of Listeria . GFZ intensified the bacteriostatic effect of 4 micrograms/ml NFX and rendered 8 micrograms/ml bactericidal for L . monocytogenes . GFZ had a similar potentiating effect when used in combination with 2 micrograms/ml ciprofloxacin (CFX) . CFX plus GFZ was bactericidal for intracellular L . monocytogenes . Treatment of J774 cells with NFX plus GFZ markedly reduced the cytotoxic effect of the bacteria on these cells . Over 55% of cells treated with 8 micrograms/ml NFX alone were dead 16 h after infection, whereas only 5% of cells treated with 8 micrograms/ml NFX plus GFZ were dead at 16 h . Similarly, GFZ potentiated the ability of 2 micrograms/ml to protect J774 cells against the cytocidal effect of Listeria . NFX in combination with GFZ limited cell-to-cell spread of L . monocytogenes . In antibiotic-free medium, > 99% of J774 cells contained intracellular L . monocytogenes at 14 h after infection . NFX alone in the medium did not change this outcome . However, 4 micrograms/ml NFX plus GFZ decreased bacterial spread by approximately 40% at 24 h postinfection, and 8 micrograms/ml NFX plus GFZ prevented all spread beyond the initially infected cell population . These results suggest that GFZ could be used clinically to enhance the efficacy of fluoroquinolone and of other anionic antibiotics against bacteria that grow and/or reside within macrophages and/or other cells.

J Immunol, 1992 Nov 1, 149(9), 3016 - 22
Kinetic analysis of cytokine gene expression in the livers of naive and immune mice infected with Listeria monocytogenes . The immediate early phase in innate resistance and acquired immunity; Ehlers S et al.; The anamnestic response to infection with Listeria monocytogenes is characterized by the rapid elimination of normally lethal doses of bacteria and accelerated granuloma formation . These phenomena are mediated by listeria-specific memory T cells within the first 24 h after reinfection . In order to elucidate the mechanisms operative during this decisive phase of infection, we conducted a comprehensive kinetic and quantitative analysis of cytokine gene expression in the livers of naive and immune mice . Organs were removed at 30 min, and 1, 2, 6, and 24 h after primary and secondary infections, and PCR3-assisted messenger RNA (mRNA) amplification was performed on matched samples using primers specific for IL-1 beta, IL-6, M-CSF, GM-CSF, TNF-alpha, IFN-gamma, IL-10, IL-4, IL-2, IL-3 and I1-2Rp55 . The cytokine pattern characteristic of secondarily infected animals differed qualitatively by the expression of mRNA for IL-2, IL-2Rp55, IL-3, and IL-4, demonstrating the accumulation and activation of specific T cells in the livers as early as 1 to 2 h after reinfection . Combined in vivo depletion of both CD4+ and CD8+ T cells before reinfection almost completely abrogated the differentiated cytokine profile typical of the anamnestic response . Using competitive PCR for semiquantitative determination of mRNA levels, the amount of IL-1 beta and IL-6 mRNA was found to be very similar during primary and secondary infection, whereas TNF-alpha mRNA was found to be increased by approximately 10-fold 2 h and IFN-gamma mRNA by approximately 50 to 100-fold 6 h after reinfection when compared with a primary challenge . Combined in vivo depletion of both CD4+ and CD8+ T cells before reinfection resulted in a substantial (approximately 10-fold) decrease in IFN-gamma mRNA expression . To correlate these findings with cytokine secretion, spleen cells from naive and immune as well as normal and CD4+ and CD8+ cell depleted mice infected 6 h previously were cultured for 48 h, and supernatants were analyzed for the amount of the above mentioned cytokines . Semiquantitative PCR-assisted mRNA amplification is demonstrated to be a superior tool in dissociating the mediators of innate resistance from those operative in protective immunity and granuloma formation.

J Cell Biol, 1992 Nov, 119(3), 531 - 42
Class II MHC molecules are present in macrophage lysosomes and phagolysosomes that function in the phagocytic processing of Listeria monocytogenes for presentation to T cells; Harding CV et al.; Phagocytic processing of heat-killed Listeria monocytogenes by peritoneal macrophages resulted in degradation of these bacteria in phagolysosomal compartments and processing of bacterial antigens for presentation to T cells by class II MHC molecules . Within 20 min of uptake by macrophages, Listeria peptide antigens were expressed on surface class II MHC molecules, capable of stimulating Listeria-specific T cells . Within this period, degradation of labeled bacteria to acid-soluble low molecular weight catabolites also commenced . Immunoelectron microscopy was used to evaluate the compartments involved in this processing . Upon uptake of the bacteria, phagosomes containing Listeria fused rapidly with both lysosomes and endosomes . Class II MHC molecules were present in a tubulo-vesicular lysosome compartment, which appeared to fuse with phagosomes, as well as in the resulting phagolysosomes containing internalized Listeria; these compartments were all positive for Lamp 1 and cathepsin D and lacked 46-kD mannose-6-phosphate receptors . In addition, class II MHC and Lamp 1 were co-localized in vesicles of the trans Golgi reticulum, where they were segregated from 46-kD mannose-6-phosphate receptors . Vesicles containing both Listeria-derived components and class II MHC molecules were also observed; some of these may represent vesicles recycling from phagolysosomes, potentially bearing processed immunogenic peptides complexed with class II MHC . These results support a central role for lysosomes and phagolysosomes in the processing of bacterial antigens for presentation to T cells . Tubulo-vesicular lysosomes appear to represent an important convergence of endocytic, phagocytic and biosynthetic pathways, where antigens may be processed to allow binding to class II MHC molecules and recycling to the cell surface.

J Bacteriol, 1992 Nov, 174(22), 7098 - 103
Physical map of the Listeria monocytogenes chromosome; Michel E et al.; The circular physical map of the pathogenic bacterium Listeria monocytogenes LO28 (serovar 1/2c) was established by using pulsed-field gel electrophoresis . The L . monocytogenes chromosome contains eight NotI fragments of 1,100, 940, 400, 335, 280, 45, 30, and 20 kb in size and eight Sse8387I fragments of 860, 680, 680, 370, 335, 130, 70, and 25 kb . Therefore, the total length of the genome is 3,150 kb . To order the NotI fragments on the chromosome, we used a strategy which can be of general use . We first cloned chromosomal HindIII or EcoRI fragments in pBR322 . DNA extracted from the total libraries was digested by NotI and ligated to a NotI-kanamycin resistance cassette obtained by cutting Tn5 with NotI . After transformation in Escherichia coli, kanamycin-resistant clones originating from NotI-containing EcoRI or HindIII fragments were isolated . The two EcoRI-NotI or HindIII-NotI fragments of each recombinant plasmid were isolated and used as probes on Southern blot hybridizations to identify and link the corresponding NotI fragments . Seven NotI fragments were ordered in this way . The last junction was demonstrated by partial digest analysis . All L . monocytogenes genes identified so far as well as the six rRNA operons were localized on the NotI map . Regions homologous to genes from closely related bacteria were also detected and localized . Southern blot analysis of simple Sse8387I digests or double Sse8387I-NotI digests probed with the various NotI probes allowed us to align the Sse8387I fragments and localize the single SfiI site, resulting in the establishment of the first genetic and physical map of the L . monocytogenes chromosome.

Int Immunol, 1992 Oct, 4(10), 1129 - 36
The appearance and role of gamma delta T cells in the peritoneal cavity and liver during primary infection with Listeria monocytogenes in rats; Hasegawa T et al.; We have previously reported that gamma delta T cells play important roles in protection during the early stage of infection with Listeria monocytogenes in mice . To generalize the protective roles of gamma delta T cells in listerial infection to different species, we examined the appearance of gamma delta T cells during infection with L . monocytogenes in Fisher F344 rats . The numbers of bacteria in the peritoneal cavity and liver increased to a maximum level on day 3 and then decreased to an undetectable level by day 10 after an intraperitoneal infection with a sublethal dose (1 x 10(8)) of viable L . monocytogenes in rats . CD3+ alpha beta- T cells in the peritoneal cavity and liver began to increase on day 3, reached a maximum level on day 6, and thereafter decreased gradually by day 10 after infection . Northern blot analysis confirmed that the CD3+ alpha beta- T cells expressed TCR delta and gamma gene messages . In vivo treatment with anti-TCR alpha beta mAb, which suppressed most of the alpha beta T cells in the periphery and impaired resistance during the late stage of listerial infection, did not affect the host defense by day 6 after infection . A significantly increased number of gamma delta T cells was detected in the peritoneal cavity of the TCR alpha beta-suppressed rats on day 6 after infection . These results suggest that the early appearing gamma delta T cells may contribute to the host defense at a relatively early stage during listeriosis in rats.

Mol Microbiol, 1992 Oct, 6(20), 2919 - 29
Cloning and characterization of a gene encoding flagellin of Listeria monocytogenes; Dons L et al.; The gene, flaA, encoding the flagellin protein of Listeria monocytogenes (strain 12067) has been isolated from an expression library in Escherichia coli using a flagellin-specific monoclonal antibody . DNA sequence analysis of a positive clone revealed the presence of an open reading frame of 287 amino acid residues with a calculated molecular mass of 30.4 kDa . Comparison of this sequence with flagellins from other bacteria showed a significant degree of homology in both the N- and C-terminal parts of the protein . The flagellin mRNA was determined to be 1 kb in size, which is the expected size for a monocistronic mRNA, and the temperature-dependent expression of flagellin was found to be regulated at the transcriptional level . Southern blot analysis, using the flagellin gene as probe, indicated that L . monocytogenes can be divided into two groups . These groups correspond to the flagellar antigens AB and ABC, respectively, as well as to the two types of L . monocytogenes based on the DNA sequence of the listeriolysin gene.

J Chemother, 1992 Oct, 4(5), 276 - 80
Correlation between the in vivo and in vitro antimicrobial properties of commercially available mouthwash preparations; Moneib NA et al.; The effectiveness of six commercially available mouthwashes against common buccal organisms was studied . The minimum inhibitory concentrations (MIC) for two of the studied mouthwashes (Corsodyl and Oraldene) against buccal organisms were determined in Todd Hewitt medium with or without 5% serum . The concentration of the active substance in these two mouthwashes was in excess of the corresponding MIC . When the medium was supplemented with serum, lower MIC values were observed . Kill-time determinations, used at half the concentration of the normal preparation, revealed a rapid lethal effect for all tested mouthwashes . The slowest lethal effect was observed with Fluocaril mouthwash . When mouthwashes were tested in volunteers, an immediate significant fall in salivary bacterial counts was produced by all except Fluocaril . With the latter mouthwash the decrease was significant 2-30 minutes after rinsing . The bacterial levels returned to pre-rinse levels after 30 minutes for Listerine, after 90 minutes for both Oraldene and Mint and after 180 minutes for Corsodyl, Fluocaril and Sansilla mouthwashes . The results indicate that there is a good correlation between in vivo efficacy and in vitro determination of all mouthwash preparations.

J Clin Gastroenterol, 1992 Oct, 15(3), 251 - 5
Acute hepatitis by Listeria monocytogenes in an HIV patient with chronic HBV hepatitis; De Vega T et al.; We report a young male IVDA with CAH caused by HBV who was infected with HIV and who contracted listeriosis in the form of acute hepatitis and bacteremia, with epithelioid granulomas in the liver . Treatment with ampicillin and a aminoglycoside for 3 weeks was followed by rapid and maintained improvement . Involvement of the liver is unusual in listeriosis and, as far as we are aware, it has not been described previously in patients with HIV infection.

Vet Immunol Immunopathol, 1992 Oct, 34(1-2), 149 - 58
Effect of aflatoxin B1 on in vitro production of interleukin-1 by bovine mononuclear phagocytes; Kurtz RS et al.; In this study we examined the effects of preincubation with aflatoxin B1 (AFB1) on the ability of bovine monocytes to produce the immunological mediator interleukin-1 (IL-1) . Monocytes preincubated for 6-24 h with 10 micrograms ml-1 AFB1 demonstrated a diminished capacity to release IL-1 activity in response to bacterial lipopolysaccharide (LPS) . Preincubation for less time, or with lower concentrations of AFB1, did not affect IL-1 release . Pretreatment of monocytes with AFB1 also resulted in diminished release of IL-1 activity in response to in vitro infection with Listeria monocytogenes . Incubation with AFB1 reduced the amount of IL-1 beta mRNA in LPS-stimulated bovine monocytes; however, this was observed only at high concentrations of AFB1 that non-specifically reduced steady-state transcription of actin mRNA . We therefore concluded that AFB1 does not specifically suppress monocyte release of IL-1, other than through its general inhibition of mRNA transcription.

Pediatr Res, 1992 Oct, 32(4), 460 - 4
Role of tumor necrosis factor-alpha and interferon-gamma in newborn host defense against Listeria monocytogenes infection; Bortolussi R et al.; The fetus and newborn are particularly susceptible to Listeria monocytogenes infection . We used a newborn rat animal model to investigate neonatal host defense against Listeria . In this animal model, newborn (3-d-old) rats are more susceptible to L . monocytogenes than older animals . Juvenile (23-d-old) L . monocytogenes-infected rats pretreated with lipopolysaccharide (LPS) had a lower bacterial load in blood than control animals, whereas LPS pretreated newborn rats had a higher bacterial load . Because LPS is a potent inducer of tumor necrosis factor (TNF) and TNF enhances host defense against this organism in adult animals, we assessed TNF content in splenic homogenates for animals of different ages . The age at which TNF was detectable in L . monocytogenes-Infected rats corresponded to the age at which LPS became active in preventing severe bacteremia . TNF was less than 1 unit/mL in splenic homogenates taken from rats less than 8 d of age, whereas 16-d-old rats infected with L . monocytogenes 1 d earlier had greater than 80 units/mL (p less than 0.0001 for 3-d-old versus 16-d-old rats) . We also assessed the responsiveness of rats to exogenous TNF-alpha . Juvenile rats pretreated with TNF-alpha before L . monocytogenes infection had decreased bacterial load in spleen (p less than 0.02 versus controls) and better survival at 7 d (p less than 0.05 versus controls), whereas newborn rats did not improve with TNF-alpha pretreatment (p greater than 0.05 treated versus controls for splenic bacterial load and 7-d survival).(ABSTRACT TRUNCATED AT 250 WORDS)

Int J Exp Pathol, 1992 Oct, 73(5), 565 - 72
Measurements of blood flow and histometry of the cellular infiltrate in tuberculin skin test responses of the typical Koch type and the non-turgid variant form (Listeria-type) in pulmonary tuberculosis patients and apparently healthy controls; Potts RC et al.; The typical turgid Koch type and the non-turgid variant form (Listeria-type) of the tuberculin skin test responses were studied in 76 newly diagnosed pulmonary tuberculosis patients and 29 apparently healthy factory worker controls from Surabaya in Indonesia; in general, the patients had more intense responses than the controls . The blood flow velocity (RBCflux) at the centre of the reaction was similar in all groups, but central relative slowing (a presumed forme fruste of severe ischaemia) was much more common in the Koch-type reactions in tuberculosis patients . In both groups of subjects, the overall density of cellular infiltrate (and the major populations of inflammatory cells) was greater in the typical Koch-type reactions than in the non-turgid variant reactions . Thus the Koch-type reactions were indubitably more intense in inflammatory terms than the non-turgid variant form, but the results of this study do not exclude the possibility that there were underlying qualitative differences in pathogenesis between reactions of the two types as well as the obvious difference in severity.

South Med J, 1992 Oct, 85(10), 957 - 60
Listerial infections in patients with systemic lupus erythematosus; Harisdangkul V et al.; Infection with Listeria monocytogenes is known to occur more frequently in immunosuppressed patients, including those receiving high-dose prednisone or cytotoxic therapy for collagen vascular disease . We reviewed three cases of listeriosis and systemic lupus erythematosus (SLE) seen at our institution, in addition to five cases reported in the English literature . Seven of the eight patients had non-CNS listerial infections . All patients but one had associated risk factors of either renal failure or pregnancy . From our review, we found that listeriosis is uncommon in SLE, and patients without renal failure or pregnancy do not seem to be at increased risk for listeriosis . Although most patients were treated with high-dose prednisone, with or without cytotoxic drugs, the role of immunosuppression by these drugs as a risk factor for listeriosis remained unclear.

J Clin Microbiol, 1992 Oct, 30(10), 2705 - 8
Purification of listeriolysin O and development of an immunoassay for diagnosis of listeric infections in sheep; Low JC et al.; A protein of 58,000-Da molecular mass was purified from the supernatant fluid of a dialysis sac culture of Listeria monocytogenes by cation-exchange chromatography . The purified protein, homogeneous by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and possessing the characteristics of listeriolysin O (LLO), was used to develop an indirect enzyme-linked immunosorbent assay . Anti-LLO antibodies were shown to be consistently produced in sheep after experimental challenge with L . monocytogenes serovar 4b . The assay also successfully detected and measured specific anti-LLO antibodies in the sera of silage-fed sheep among which listeric enteritis and abortions had occurred.

Infect Immun, 1992 Oct, 60(10), 4402 - 6
Recombinant interleukin-6 protects mice against experimental bacterial infection; Liu Z et al.; Because of reports of high levels of interleukin-6 (IL-6) in patients during infection, we studied the role of IL-6 in experimental infection . Mice infected with the facultative intracellular pathogen Listeria monocytogenes displayed high levels of IL-6 in their sera and tissues, particularly the spleen, 1 to 3 days after infection . At this time, the IL-6 titers correlated with bacterial numbers in individual mice and in groups of mice given graded doses of Listeria organisms . However, the presence of IL-6 in serum declined after 4 days, even when a large initial dose of bacteria meant that bacterial numbers were still increasing at this time . Recombinant mouse IL-6 injected intraperitoneally before infection protected mice in a dose-dependent manner . It was effective when given 4 h before infection but not when administration was delayed for 24 h postinfection . It is therefore believed that IL-6 plays a role in early priming of the immune response to infection . Its exact function in this model is being investigated.

Infect Immun, 1992 Oct, 60(10), 4335 - 42
Leishmania donovani infection in scid mice: lack of tissue response and in vivo macrophage activation correlates with failure to trigger natural killer cell-derived gamma interferon production in vitro; Kaye PM et al.; Infection of immunocompetent mice with Leishmania donovani is characterized by the development of a tissue granulomatous response, in vivo macrophage activation, and a predominantly Th1-type CD4+ T-cell response . To determine whether a recently described T-cell-independent pathway of gamma interferon (IFN-gamma) production involving the collaboration of macrophages and natural killer (NK) cells contributed to this pattern of events, we have investigated the responses of scid mice to L . donovani infection . The multiplication of parasites in the livers of scid mice progressed at a rate equivalent to that seen in BALB/c mice over the first 14 days of infection, but by day 28 scid mice had a fivefold-higher parasite burden . This infection was not, however, accompanied by any demonstrable histological response in the liver or by elevated major histocompatibility complex class II expression on splenic macrophages . In vitro, L . donovani was unable to trigger IFN-gamma production from scid spleen cell cultures under conditions which allowed efficient triggering by bacterial stimuli . Although L . donovani also failed to stimulate the release of tumor necrosis factor, an important macrophage-derived cofactor for IFN-gamma secretion by NK cells, exogenous recombinant tumor necrosis factor alpha could not restore the IFN-gamma response . Even with the potent synergistic effect of exogenous interleukin-2, L . donovani was unable to stimulate this pathway to the same extent as Listeria monocytogenes . Indeed, L . donovani inhibited the response to L . monocytogenes in a dose-dependent fashion . Experiments involving the transfer of supernatants and the use of neutralizing monoclonal antibodies have failed to find evidence that interleukin-10 is involved in this inhibition . These data suggest that NK cell-derived IFN-gamma is unlikely to participate in the early regulation of visceral leishmaniasis in the mouse.

Infect Immun, 1992 Oct, 60(10), 4068 - 73
Early expression of cytokine mRNA in mice infected with Listeria monocytogenes; Iizawa Y et al.; Protective immunity first becomes evident at 3 to 4 days after inoculation of mice with a sublethal dose of Listeria monocytogenes . Recent evidence suggests that production of gamma interferon (IFN-gamma) occurs earlier (within the first 24 h of infection) . The purpose of this study was to define better the sequence of cytokine mRNA expression during the early stages of L . monocytogenes infection . Cytokine mRNA expression was detected by polymerase chain reaction-assisted amplification of RNA extracted from the spleen cells of individual mice euthanized at 0.5 to 120 h after L . monocytogenes challenge . By using this method, mRNAs for tumor necrosis factor alpha, interleukin-1 alpha (IL-1 alpha), IL-2, IL-4, IL-5, and IFN-gamma were detected in RNA from the spleen cells of uninfected mice . The intensity of the bands for IFN-gamma, however, was increased greatly at 16 h after intravenous injection of 5 x 10(4) CFU (nearly 1 50% lethal dose) of L . monocytogenes . IL-6 and granulocyte-macrophage colony-stimulating factor mRNAs were not detected in spleen cell RNA from uninfected mice but were induced within 30 and 60 min, respectively, after inoculation with L . monocytogenes . Increased amounts of mRNAs for IFN-gamma, IL-6, and granulocyte-macrophage colony-stimulating factor were detected after injection of viable, but not killed, L . monocytogenes . IL-3 mRNA was not detected at any time in RNA extracted from the spleen cells of uninfected or L . monocytogenes infected mice . These results suggest that infection with L . monocytogenes elicits a detectable cytokine mRNA response within the first few hours of infection.

Infect Immun, 1992 Oct, 60(10), 4059 - 67
Purification and characterization of Listeria monocytogenes phosphatidylinositol-specific phospholipase C; Goldfine H et al.; We have purified to homogeneity the 33-kDa phosphatidylinositol-specific phospholipase C (PI-PLC) from the culture fluid of Listeria monocytogenes, a facultative intracellular pathogen . The protein was overexpressed, and secretion of PI-PLC was further enhanced by the addition of divalent cations to the culture medium . The basic protein (pI, approximately 9.4) was complexed with anionic proteins in the crude culture fluid . It bound to DEAE-Sepharose and was eluted from Sephacryl S-200 near the void volume in low-ionic-strength buffer, suggesting aggregates of greater than or equal to 150 kDa . Gel filtration chromatography on Sephacryl S-200 in the presence of 1 M ammonium sulfate resulted in disaggregation and complete separation of PI-PLC, which interacted with the column matrix . Amino-terminal sequencing of the pure protein gave results consistent with the previously deduced sequence and showed that the signal cleavage site was between alanine 29 and tyrosine 30 . The enzyme was specific for PI and showed no activity with phosphatidylethanolamine, phosphatidylcholine, or phosphatidylserine . It did not cleave PI-4-phosphate or PI-4,5-bisphosphate, but it was active on the membrane form of the variable surface glycoprotein from Trypanosoma brucei, a PI-glycan-anchored protein . When assayed with deoxycholate-mixed micelles of PI, activity was highly dependent on added salt . Activation by salt was also observed with Triton X-100-mixed micelles . The optimal concentration of CaCl2 or MgCl2 was lower than that of KCl or (NH4)2SO4, but activity was not specifically dependent on divalent cations and was not inhibited by addition of EDTA . With deoxycholate, the optimum pH was 7.0 . A broader pH optimum ranging from 5.5 to 6.5 was observed with Triton X-100-mixed micelles . These results are consistent with a postulated role for secreted PI-PLC in the acidified primary phagocytic vesicle of infected cells.

FEMS Microbiol Lett, 1992 Sep 15, 75(2-3), 219 - 24
Studies on the ribosomal RNA operons of Listeria monocytogenes; Thompson DE et al.; A 23S rRNA gene of Listeria monocytogenes was cloned into pUC19 on a 6.2-kb Pst I fragment . Hybridisation studies demonstrated the presence of the 5S and partial 16S rRNA genes within the clone . The nucleotide sequence of the region encoding the 23S rRNA was found to be highly homologous with those of other low G + C Gram-positive bacteria . The 16S-23S intergenic spacer region was amplified using PCR technology and revealed two product sizes, the larger of which contained tRNA(Ala) and tRNA(Ileu) genes . Further tRNA genes were found downstream of the 5S rRNA gene.

Ann Intern Med, 1992 Sep 15, 117(6), 466 - 9
Listeriosis in patients with chronic lymphocytic leukemia who were treated with fludarabine and prednisone; Anaissie E et al.; OBJECTIVE: To determine whether therapy with fludarabine plus prednisone in patients with chronic lymphocytic leukemia increases the risk for developing listeriosis . DESIGN: Retrospective cohort study based on hospital surveillance data . SETTING: Referral cancer center . PARTICIPANTS: A total of 795 patients with chronic lymphocytic leukemia who received care at The University of Texas M . D . Anderson Cancer Center between 1980 and 1990 . INTERVENTIONS: Patients were treated with fludarabine alone or fludarabine and prednisone . MEASUREMENTS: The listeriosis attack rate was analyzed according to the type of treatment received . RESULTS: Seven of 408 patients in the fludarabine group developed listeriosis (1.7%; 95% Cl, 0.2% to 6%) compared with 0 of 387 patients who received conventional chemotherapy alone (0% to 0.9%; P = 0.015) . The 7 patients were among 248 patients who were treated with both fludarabine and prednisone; none of 160 patients treated with fludarabine alone developed listeriosis (P = 0.045 by the Fisher exact test) . A dramatic reduction in CD4 counts occurred in patients after fludarabine and prednisone treatment and coincided with the development of listeriosis . CONCLUSION: The administration of fludarabine plus prednisone is associated with an increased incidence of listeriosis in patients with chronic lymphocytic leukemia . The depletion of CD4 cells may underlie the pathogenesis.

Gene, 1992 Sep 1, 118(1), 121 - 5
A gene encoding a superoxide dismutase of the facultative intracellular bacterium Listeria monocytogenes; Brehm K et al.; A gene (lmsod) encoding superoxide dismutase (SOD; EC 1.15.1.1) of the facultative intracellular pathogen, Listeria monocytogenes, was cloned by functional complementation of an SOD-deficient Escherichia coli mutant . The nucleotide sequence was determined and the deduced amino acid (aa) sequence (202 aa) showed close similarity to manganese-containing SOD's from other organisms . Subunits of the recombinant L . monocytogenes SOD (re-SOD) and of both E . coli SODs formed enzymatically active hybrid enzymes in vivo . DNA/DNA-hybridization experiments showed that this type of recombinant re-sod gene is conserved within the genus Listeria.

Infect Immun, 1992 Sep, 60(9), 3609 - 19
Host cell actin assembly is necessary and likely to provide the propulsive force for intracellular movement of Listeria monocytogenes; Sanger JM et al.; Listeria monocytogenes is able to escape from the phagolysosome and grow within the host cell cytoplasm . By 3 h after initiation of infection, actin filaments begin to concentrate at one end of the bacterium . Polarization of F-actin is associated with intracellular bacterial movement, long projections of actin filaments forming directly behind the moving bacteria . New actin monomers are added to the region of the projection in proximity to the bacterium . The rate of new actin filament growth correlates closely with the speed of bacterial migration . This actin structure is anchored within the cytoplasm, serving as a fixed platform for directional expansion of the actin filament network . The actin projection progressively lengthens as the bacterium migrates . Cytochalasin blocks both elongation of the projection and bacterial movement but does not result in complete depolymerization of the bacterially induced actin structure, residual actin and alpha-actinin persisting in proximity to one end of the bacterium . Bacteria initially migrate within the cortical cytoplasm but later move to the peripheral membrane, where they form filopodiumlike structures which pivot and undulate in the extracellular medium . In the filopodia, bacteria are occasionally seen to abruptly change direction, turn 180 degrees, and move back into the medullary region of the host cell . All filopodium movement ceases once the bacterium containing the F-actin projection returns to the cortical cytoplasm . These results indicate that host cell actin polymerization is necessary for intracellular migration of listeriae and suggest that directional actin assembly may in fact generate the propulsive force for bacterial and filopodial movement.

Zentralbl Veterinarmed B, 1992 Sep, 39(7), 513 - 8
A direct plating method for monitoring the contamination of Listeria monocytogenes in silage; Fernandez-Garayzabal JF et al.; Twenty-two silage samples were analyzed for the presence of L . monocytogenes using five Listeria selective plating media, with and without previous selective enrichment step . L . monocytogenes was recovered from 3 samples by both procedures, but direct plating allowed the quantification of Listeria population . Two of these positive samples were implicated in outbreaks of listeriosis in sheep; the L . monocytogenes population in these samples was about 10(6) cells/g . The L . monocytogenes population in the other positive sample was 10(3) cells/g . Direct isolation of L . monocytogenes was only possible from LPM, PALCAM and LSAMm media . MOX and LSM media were not selective enough to allow direct Listeria isolation . In our hands, LSAMm was the most suitable plating medium for the direct isolation and specific quantification of L . monocytogenes from silage employing a red blood cells overlay technique.

Zentralbl Veterinarmed B, 1992 Sep, 39(7), 473 - 84
{The diagnosis of listeria encephalitis in ruminants using cultural and immunohistologic methods . II . Immunohistologic studies in formalin-fixed paraffin sections}; Peters M et al.; The unlabelled peroxidase-antiperoxidase (PAP)-technique was compared with the avidin-biotin-peroxidase-complex (ABC)-technique in the identification of Listeria antigen in formalin-fixed paraffin sections of 58 ruminant brains, 44 of which showed histopathological lesions typical for listeric encephalitis . Rabbit hyperimmune serum, obtained by immunization with a Listeria monocytogenes strain of serotype 1/2 a, served as primary serum in the immunohistochemical investigations . The antiserum was tested for specificity using formalin-fixed smears of various bacterial species . Listeria antigen was demonstrated in 40 of the 44 brains with histopathological CNS alterations, as seen in listeriosis, using the ABC method, whereas their identification with the PAP method only succeeded in 34 of the brains . Despite the higher dilution of the primary antibody, the ABC method distinguished itself further, in comparison with the PAP method, through more intense immunohistochemical staining of Listeria antigen . Listeria spp, could be isolated from 46 of 52 brains, which were also examined bacteriologically . They could be isolated from 14 brains, which showed no histopathological lesions indicative of listeriosis . In contrast to this, Listeria antigen was only detected immunohistologically in brains with typical histological listeric CNS alterations . In three cases the presumptive histological diagnosis could not be confirmed immunohistologically.

Surv Ophthalmol, 1992 Sep-Oct, 37(2), 117 - 24
Elevated intraocular pressure, pigment dispersion and dark hypopyon in endogenous endophthalmitis from Listeria monocytogenes; Eliott D et al.; Listeria monocytogenes endophthalmitis occurred in an immunologically competent patient with no identifiable extraocular septic focus . The patient presented with a dark hypopyon and markedly elevated intraocular pressure, and the diagnosis was established by culture and histopathologic examination of ocular fluid . Four of the fourteen reported cases of Listeria monocytogenes endophthalmitis also presented with a dark hypopyon, and all cases had markedly elevated intraocular pressure . The presence of a dark hypopyon and elevated intraocular pressure may indicate endogenous intraocular infection with Listeria monocytogenes, even in an apparently healthy host.

Appl Environ Microbiol, 1992 Sep, 58(9), 3183 - 6
Plasmids in Listeria monocytogenes in relation to cadmium resistance; Lebrun M et al.; One hundred and seventy-three unrelated Listeria monocytogenes strains isolated from humans, animals, the environment, and food were analyzed for the presence of plasmids . Extrachromosomal DNA was found in 28% of the strains . Plasmid DNA was extracted more frequently from L . monocytogenes serogroup 1 strains (35%) than from serogroup 4 strains (15%) . Among strains from food and the environment, 40% and 29%, respectively, harbored plasmids, whereas only 13% of the strains from humans and animals with listeriosis bore plasmids . We also investigated the susceptibility of 90 strains to seven antibiotics and four heavy-metal salts . No antibiotic resistance could be detected, but 95.3% of the plasmid-positive strains and only 12.7% of the plasmid-negative strains were resistant to cadmium . The plasmid-determined genetic basis of cadmium resistance was proven by conjugation between strains of L . monocytogenes and by cure of the plasmid . This is the first time that plasmids of L . monocytogenes have been shown to be associated with cadmium resistance.

Appl Environ Microbiol, 1992 Sep, 58(9), 3177 - 9
Evaluation of the ability of primary selective enrichment to resuscitate heat-injured and freeze-injured Listeria monocytogenes cells; Budu-Amoako E et al.; Resuscitation rates of injured Listeria monocytogenes on conventional selective Listeria enrichment broth and nonselective Trypticase soy broth containing 0.6% yeast extract were compared . Cells were heated to 60 degrees C for 5 min or frozen at -20 degrees C for 7 days . Inoculation of Trypticase soy broth-yeast extract with the stressed cells resulted in growth that was superior to that in Listeria enrichment broth . Injured cells were fully recovered at 6 to 8 h.

Appl Environ Microbiol, 1992 Sep, 58(9), 2827 - 31
16S rRNA-based probes and polymerase chain reaction method to detect Listeria monocytogenes cells added to foods; Wang RF et al.; A rapid polymerase chain reaction (PCR) method was developed for detection of Listeria monocytogenes in foods . This method used a pair of primers based on a unique region in the 16S rRNA sequence of L . monocytogenes, which were previously reported by us to yield a specific nucleic acid probe . Our method included use of a shorter denaturing time, a shorter annealing time, a rapid transition, and an increase in the number of cycles, resulting in good sensitivity . Just 3 h for PCR plus 1 h for electrophoresis was required . Additional time for DNA isolation and DNA hybridization was not needed . This method detected as few as 2 to 20 CFU of L . monocytogenes in pure cultures and as few as 4 to 40 CFU of L . monocytogenes in inoculated (10(8) CFU), diluted food samples . Seven of eight foods, including four poultry products, gave positive results . Only one food sample, soft cheese, gave interference . An internal probe hybridization test was used to confirm that the PCR products were from L . monocytogenes . A specificity test indicated that this PCR method was positive for all 13 strains of L . monocytogenes tested but negative for the other 6 species of Listeria, including 6 strains of L . innocua, and negative for 17 other gram-positive and gram-negative bacteria tested.

Pediatr Pathol, 1992 Sep-Oct, 12(5), 665 - 71
Fetal listeriosis during the second trimester of gestation; Lallemand AV et al.; Listeriosis is common and is implicated in about 3% of second-term abortions examined in our laboratory . Maternal fever was followed rapidly in all instances by the expulsion of a nonmacerated fetus . Chorioamnionitis was always present and was associated with placental microabscesses . Leukocytic infiltrates were frequent in fetal tissues, being present in adrenal, lung, and skin . Listeria monocytogenes was isolated from 8 of the 205 abortions that had microbiological cultures (3.9%) . The clinical features and morphological lesions were so characteristic that the diagnosis of listeriosis could be made in 5 of the 217 fixed abortuses received during the same period, but without culture . In contrast to the third trimester of pregnancy, there were no inflammatory lesions in the central nervous system in our small series.

An Med Interna, 1992 Sep, 9(9), 425 - 7
{Meningitis from Listeria monocytogenes in the adult}; Laguna F et al.; We describe the characteristics of 6 adult patients with meningitis by Listeria monocytogenes . Five of them had previous disease and only one of these was being treated with immunosuppressors . All of them presented meningeal syndrome with cephalorhachidean fluid's pleocytosis and five of them, polymorphonuclear predominance . The empirical treatment was correct only in two cases . The mortality rate reached 50%.

Rev Inst Med Trop Sao Paulo, 1992 Sep-Oct, 34(5), 475 - 8
Listeriosis and AIDS: case report and literature review; da Silva LJ et al.; Listeriosis is a not uncommon infection in humans, usually associated with immunodeficient states and with newborns . However, relatively few cases have been reported in HIV-infected patients . This scarcity of reported cases has aroused interest in the association of listeriosis and AIDS . In this paper we present a case of meningitis and septicemia caused by Listeria monocytogenes in a female patient with AIDS . A review of recent medical literature indicates that association of listeriosis and AIDS may be more common than it seems . Recent research in host-parasite interaction in listerial infection suggests an important role for tumor necrosis factor (TNF) and for integralin, a bacterial protein, in modulating listerial disease in AIDS patients . Inadequate diagnosis may be in part responsible for the scarcity of reports.

Appl Environ Microbiol, 1992 Aug, 58(8), 2625 - 32
The homologous and heterologous regions within the iap gene allow genus- and species-specific identification of Listeria spp . by polymerase chain reaction; Bubert A et al.; The iap gene of Listeria species encodes protein p60 . The comparison of iap-related genes from different Listeria species indicated common and variable regions within these genes which appeared to be specific for each Listeria species . On the basis of the iap gene sequences, pairs of polymerase chain reaction (PCR) primers which allowed the unambiguous identification of all members of the genus Listeria, of groups of related Listeria species, and of L . monocytogenes, exclusively, were selected . The PCR primers specific for L . monocytogenes yielded PCR products which represented essentially the repeat region of the iap gene . The size of these PCR products allowed an estimate of the number of the TN repeat units within the repeat region of the p60 protein of an L . monocytogenes strain . The data indicated that the number of repeat units differed among L . monocytogenes isolates.

J Clin Microbiol, 1992 Aug, 30(8), 1931 - 6
Development of polymerase chain reaction assays for detection of Listeria monocytogenes in clinical cerebrospinal fluid samples; Jaton K et al.; In order to improve the diagnosis of Listeria meningitis or meningoencephalitis, especially in patients who have received antibiotics before their cerebrospinal fluid (CSF) has been examined, two assays for the detection of Listeria monocytogenes based on the polymerase chain reaction (PCR) were evaluated . After a standard PCR, the amplified DNA was detected either by a second round of PCR with internal primers followed by gel electrophoresis and ethidium bromide staining (nested PCR) or by dot blot hybridization to an internal digoxigenin-labeled probe (PCR-dot blot) . For PCR, two sets of primers within the invasion-associated protein gene (iap gene) were chosen . They allowed for the highly specific detection of all L . monocytogenes reference strains tested (serotypes 1/2a, 1/2b, 1/2c, 3a, 3b, 3c, 4a, 4b, 4c, 4d, and 7) . These primers did not detect amplification products from various other gram-positive or gram-negative bacterial DNAs or human DNA . The sensitivities of both assays were assessed on sterile CSF samples that were artificially seeded with serial dilutions of L . monocytogenes serotype 4b cells . By both methods the limit of detection was less than 10 cells in the initial reaction . Since the nested PCR is more prone to contamination because of manipulation of the amplified products, a standard PCR assay followed by dot blot hybridization was applied to 52 CSF samples in a retrospective study . Of 28 CSF samples which were sterile or positive for bacteria other than Listeria species, 24 were PCR negative . In contrast, from 17 patients with culture-proven Listeria meningitis, 14 of 17 initial CSF samples were PCR positive, as were 3 of 7 culture-negative followup CSF samples taken after patients received antibiotics . These results support the usefulness of this approach in the diagnosis of Listeria meningitis, in particular, when antibiotic administration precedes culture of CSF.

Can J Microbiol, 1992 Aug, 38(8), 865 - 70
DNA sequence heterogeneity in the gene encoding a 60-kilodalton extracellular protein of Listeria monocytogenes and other Listeria species; Gutekunst KA et al.; Chromosomal DNA sequences from the 60 kilodalton protein gene of Listeria monocytogenes, amplified by the polymerase chain reaction, were used for restriction fragment length polymorphism differentiation of L . monocytogenes serotypes and other Listeria species . All 24 strains of L . monocytogenes examined produced an extracellular protein of molecular weight 60,000 (p60) as determined by Western blot analysis . Four of six other Listeria species had a protein that cross-reacted to antibodies to p60, but all differed in molecular weight, ranging from approximately 50,000 to 65,000 . The gene encoding p60 was amplified from chromosomal DNA in all strains using polymerase chain reaction with a single primer pair . Restriction enzyme digestion with HindIII of the amplified product revealed a restriction pattern that was distinct between serotypes 1/2a and either 4b or 1/2b of L . monocytogenes . Of the other Listeria species, four strains that produced a cross-reacting protein likewise produced a polymerase chain reaction amplification product with the primer pair . Listeria innocua alone had a restriction pattern similar to that of Listeria monocytogenes serotype 4b and 1/2b . Genotypic heterogeneity, as revealed by DNA amplification and restriction endonuclease digestion of the p60 open reading frame, correlates with "electrophoretic type" grouping and may be related to differences in virulence mechanisms of Listeria monocytogenes and other Listeria species.

Can J Microbiol, 1992 Aug, 38(8), 843 - 51
A filamentous-like mutant of Listeria monocytogenes with reduced expression of a 60-kilodalton extracellular protein invades and grows in 3T6 and Caco-2 cells; Gutekunst KA et al.; We describe a spontaneous rough mutant of Listeria monocytogenes that produces reduced amounts of a 60-kilodalton major extracellular polypeptide (p60) as shown by sodium dodecyl sulfate--polyacrylamide gel electrophoresis and Western blot analysis . The cells of this mutant are filamentous, do not give rise to smooth wild-type colonies, and produce listeriolysin O in amounts equal to that of the wild-type cells, but they show a reduced virulence in the mouse LD50 model and in the Caco-2 tissue culture virulence assay . Light and electron microscopic studies show that this mutant invades and remains filamentous during in vivo growth in both Caco-2 and 3T6 tissue culture monolayers . The reduced virulence of the rough mutant is not due to the inability of its filamentous forms to invade or to grow in nonprofessional phagocytes since invasion and growth of the smooth wild-type and the rough mutants are comparable in both Caco-2 and 3T6 monolayers.

Int J Food Microbiol, 1992 Aug, 16(4), 323 - 35
Minimal water activity levels for growth and survival of Listeria monocytogenes and Listeria innocua; Nolan DA et al.; Following initial range-finding experiments, total count determinations were used to determine minimal water activity (aW) levels for the growth and survival of Listeria monocytogenes (L.m.) and L . innocua (L.i.) . Media containing three different humectants; NaCl, sucrose or glycerol were used to determine minimal aW levels for growth in the above media which were 0.92, 0.92 and 0.90 respectively . The growth minima for L.i . were similar, or slightly higher than for L.m . in these media . Survival rates were generally lower in NaCl-adjusted media than in systems adjusted with sucrose or glycerol . Survival of L.m . and L.i . in these experiments was similar.

Int J Food Microbiol, 1992 Aug, 16(4), 283 - 92
Bacteriocin (monocin) interactions among Listeria monocytogenes strains; Curtis GD et al.; Monocin interactions of 97 strains of Listeria monocytogenes were assessed using an improved production method and standardisation of the monocins against the type strain of L . ivanovii . Monocins were resistant to trypsin, sensitive to heating at 56 degrees C for 30 min and stable at 4 degrees C . Only serovar 4 strains acted as indicators . A typing system using 8 producer and 11 indicator strains showed poor discrimination.

Rev Esp Cardiol, 1992 Aug-Sep, 45(7), 483 - 5
{Listeria monocytogenes endocarditis in a patient with mitral prosthesis, left auricular thrombus and adenocarcinoma of the colon}; Segura J et al.; A case of Listeria monocytogenes endocarditis in a patient with mitral prosthetic valve, left atrial thrombus and colonic adenocarcinoma is reported . Vegetations were not demonstrated by transesophageal echocardiography and the clinical course was benign and without complications . Cure was achieved with antibiotic therapy, and surgery was not required . These features suggest that atrial thrombus could be the source of infection.

Eur J Clin Microbiol Infect Dis, 1992 Aug, 11(8), 744 - 7
Choroiditis and meningitis in experimental murine infection with Listeria monocytogenes; Prats N et al.; In a study of central nervous system involvement in experimental listeriosis 27 Swiss CD1 mice were inoculated subcutaneously with Listeria monocytogenes . Systemic infection developed, as shown by the isolation of Listeria monocytogenes and histopathological lesions in the spleen and liver . In the central nervous system a mixed inflammatory infiltration in the ventricular system, especially in the choroid plexus, and leptomeningitis were the most relevant lesions . Inflammatory lesions were associated with the presence of Listeria monocytogenes, as demonstrated by a positive anti-Listeria monocytogenes immunoperoxidase reaction within phagocytic cells . It is suggested that choroiditis and meningitis developed as a consequence of hematogenous dissemination of Listeria monocytogenes within mononuclear phagocytes and penetration of these cells into the ventricular system through the choroid plexus.

Zentralbl Veterinarmed B, 1992 Aug, 39(6), 410 - 20
{The diagnosis of Listeria encephalitis in ruminants using cultural and immunohistological techniques . I . Comparison of different selective media and culture techniques for the detection of Listeria from ruminant brains}; Peters M et al.; The selective L-PALCAMY differential enrichment broth, the Listeria enrichment broth of the International Dairy Federation, Oxford Listeria selective agar, and PALCAM Listeria selective agar were comparatively examined in the cultural isolation of Listeria spp . from ten ruminant brains . The L-PALCAMY medium proved to be superior to the IDF broth in both selectivity and productivity for Listeria spp . in the brain samples, which were also contaminated with other bacteria . The Oxford and PALCAM agars corresponded in their productivity for Listeria spp . The latter, however, was more selective than the Oxford agar . Bacterial counts of up to 1.2 x 10(9) CFU/g of brain stem sample were made from Listeria monocytogenes (L.m.), and up to 6.2 x 10(4) CFU/g from Listeria innocua . A total of 164 brains from ruminants showing CNS disturbances and/or pathoanatomical CNS alterations were examined using L-PALCAMY medium, and Oxford and PALCAM agar . L.m . could be isolated from 29 of the brains, and Listeria innocua from five . Cultural isolation of both Listeria spp . occurred in one brain . Of 27 brains containing L.m., which were also examined using cold enrichment, L.m . was isolated in 59.3% of the cases with direct culture, in 81.5% of the cases using selective warm enrichment, and in 77.8% of the cases by means of selective cold enrichment . Five cases each were identified solely by cold or warm enrichment, respectively . In investigations of further 69 ruminant brains the number of brains shown to contain L.m . could be increased from seven to 13 by means of selective cold enrichment for three months.

J Antimicrob Chemother, 1992 Aug, 30(2), 173 - 9
Effect of nanoparticle-bound ampicillin on the survival of Listeria monocytogenes in mouse peritoneal macrophages; Forestier F et al.; The efficacy of ampicillin bound to polyisohexylcyanoacrylate nanoparticles was studied in vitro in mouse peritoneal macrophages infected with Listeria monocytogenes . Nanoparticles containing ampicillin 1 mg/L were more effective after 30 h than free ampicillin at the same concentration, with viable counts of 3.68 and 5.43 log10 cfu/mL, respectively . The nanoparticles acted on the intracellular bacteria after a lag period of 6-9 h; this time was apparently required for the degradation of the polymer . At the doses used in these experiments, empty nanoparticles had neither an anti-listeria nor a cytotoxic effect.

Immun Infekt, 1992 Aug, 20(4), 125 - 7
{Thirty years of cellular immunity}; Finger H et al.; Mackaness' original article about cellular resistance to infection, published in 1962, is recalled . These experiments laid the foundation of the analysis of immune mechanisms against infection with facultatively intracellular microorganisms . Based on a simple murine model with Listeria monocytogenes, an array of data was compiled during three decades, clarifying the mechanism of inborn resistance and acquired immunity to this type of parasites . The idea of various immune cell populations cooperating via cytokines was developed and experimentally proven . Different forms of immunodeficiencies were conceived in the same model, and therapeutic approaches were evaluated . Thus, thirty years after the first publication, Mackaness' concept of cell-mediated immunity to infection is solidly based on experimental data, and is an integral part of our understanding of the mammal immune system.

Lett Appl Microbiol, 1992 Aug, 15(2), 80 - 2
The antibacterial activity of Virkon measured by colony growth and bioluminescence of lux recombinant Listeria monocytogenes; Walker AJ et al.; Concentration exponents for the broad spectrum antimicrobial Virkon were determined for Listeria monocytogenes using both plate counts and bioluminescence measurements; the values of 3.15 and 2.6 indicate a close equivalence between these two measurement procedures . Virkon is an effective biocide for L . monocytogenes at the manufacturer's in-use concentration of 1%.

J Clin Periodontol, 1992 Aug, 19(7), 509 - 20
A model for studying the effects of mouthrinses on de novo plaque formation; Ramberg P et al.; The aim of the present study was to describe a 4-day no oral hygiene model to assess the pattern of de novo plaque formation and to use this model to appraise the potential of some mouthwash preparations to retard or inhibit plaque formation in the human dentition . 10 subjects were recruited for the trial . During a preparatory period, the participants were exposed to repeated professional plaque control and given oral hygiene instruction to eliminate signs of gingivitis . At the end of the preparatory period, each participant received a final professional tooth cleaning and was subsequently told to abstain from mechanical plaque control efforts for the next 4 days . They were asked to rinse twice daily for 60 s with 10 ml varying test solutions . On Day 4, the volunteers were exposed to a new clinical examination and the presence and amount of plaque were examined by the use of the plaque index system (P1I) . The participants were subsequently given a professional tooth cleaning and asked to exercise proper self performed plaque control during the next 10 days . A new test period was then initiated . 6 different mouthwash preparations were tested in each subject namely, (1) placebo (a negative control rinse), (2) Veadent mouthrinse, (3) Listerine mouthrinse, (4) 0.06% triclosan + polyvinyl phosphonic acid (PVPA), (5) 0.06% triclosan + phenolic flavor and (6) 0.12% chlorhexidine digluconate (a positive control rinse) . The results from the study revealed that the mean P1I values for individuals, groups of teeth and tooth surfaces provide an adequate but gross overall estimation of the potential of a given mouthrinse to retard/inhibit plaque build up . More detailed information on the effects of the test rinses could be obtained by data describing the % distribution of different P1I score categories; a high frequency of score 0 describes the potential of a mouthrinse to maintain tooth surfaces free from plaque while a low frequency of score 2/3 describes the ability of a treatment to retard/prevent gross plaque formation . The plaque pattern displays finally allowed assessment of the magnitude of plaque prevention, in comparison to the positive and negative controls, that could be achieved by a given compound in various parts and surfaces of the dentition . In this model, all test rinses (i) were significantly more effective than the placebo rinse in retarding de novo plaque build up and (ii) had a minor effects on plaque build up in the maxillary molars and at the approximal surfaces.(ABSTRACT TRUNCATED AT 400 WORDS)

J Leukoc Biol, 1992 Aug, 52(2), 228 - 35
Macrophage function in response to PGE2, L-arginine deprivation, and activation by colony-stimulating factors is dependent on hematopoietic stimulus; Rutherford MS et al.; Different macrophage preparations were compared for functional capacity in conditions of high prostaglandin E2 (PGE2) or low L-arginine concentrations . Macrophages derived in vitro from bone marrow progenitor cells (bone marrow-derived macrophages, BMDMs) using colony-stimulating factor 1 (CSF-1) as the myelopoietic stimulus displayed a greater sensitivity to PGE2-induced suppression of tumor necrosis factor alpha (TNF-alpha) secretion than did macrophages derived using granulocyte-macrophage colony-stimulating factor (GM-CSF) . Neither BMDM population was inhibited by PGE2 for the direct cytolysis of L929 cells (TNF-alpha sensitive), and only GM-CSF-derived macrophages showed decreased killing of TNF-alpha-resistant K562 targets . Exogenous cAMP inhibited TNF-alpha secretion, but not nitrite secretion, by both BMDM populations . GM-CSF-derived macrophages accumulated less cAMP following PGE2 treatment than did CSF-1-derived macrophages . Removing L-arginine from the medium did not inhibit cytotoxicity or PGE2 secretion, but the listeriacidal activity specific to interferon-gamma plus lipopolysaccharide (LPS)-activated GM-CSF-derived macrophages was blocked by removal of L-arginine . Treatment with CSF-1 or GM-CSF alone did not activate the macrophages, but GM-CSF efficiently primed both BMDM populations for augmented TNF-alpha secretion in response to secondary stimulation using LPS . However, GM-CSF augmented the LPS-induced production of nitrite and PGE2 by CSF-1-derived macrophages only . These results demonstrate the potential for differential macrophage function within inflammatory sites based on the hematopoietic stimulus under which the macrophage is derived and the specific conditions present in the lesion.

Int J Food Microbiol, 1992 Aug, 16(4), 303 - 12
Direct application to dairy foods of a Listeria-specific oligonucleotide probe to 16S rRNA; Brooks JL et al.; A potentially Listeria-specific 28 base oligonucleotide probe was designed from 16S rRNA sequence data . Using either 32P or non-radioactive (alkaline phosphatase) labels, the probe was shown to be highly specific as it hybridised to RNA extracted from all of the species of Listeria but not to any of the other bacteria tested . Both probe methods were highly sensitive and ca 10(2) cfu/ml Listeria could be detected in pure cultures . A rapid procedure for extracting RNA from milk, Camembert and cottage cheese was developed . This allowed the direct application of the probe to these foods and gave a rapid and specific method of detecting > 10(2) cfu/g or ml Listeria in these foods.

Cell, 1992 Jul 24, 70(2), 215 - 23
H-2M3 presents a Listeria monocytogenes peptide to cytotoxic T lymphocytes; Pamer EG et al.; We report evidence that a major histocompatibility complex-encoded nonclassic class I molecule presents a foreign peptide to cytotoxic T lymphocytes (CTL) during an infection . Mice immunized with virulent Listeria monocytogenes generate CD8+ CTL with alpha beta receptors specific for a bacterial peptide presented by a conserved class I molecule encoded in the M region of the major histocompatibility complex . The Listeria peptide is digested by carboxypeptidase Y but resists aminopeptidase M, and only peptides with N-formyl methionine competitively block its presentation to CTL . Transfection with the H-2M3d gene enables a negative (H-2w17) cell line to present the bacterial peptide . One function, therefore, of H-2M3 is to present bacterial peptides to CTL during infection.

J Immunol, 1992 Jul 15, 149(2), 568 - 73
Sequential analysis of T cells in the liver during murine listerial infection; Hiromatsu K et al.; Phenotypes and functions of T cells in the liver were studied after an i.p . inoculation with viable Listeria monocytogenes in mice . T cells in the liver of untreated C3H/HeN mice (C3H; H-2k, Mls-2a) contain Thy-1.2+TCR-alpha beta + cells as a majority and Thy-1.2+TCR-gamma delta + cells and Thy-1.2-TCR-gamma delta + cells as minorities . The liver of untreated C3H mice did not contain T cells expressing V beta 3 and V beta 11, which are potentially autoreactive against self-superantigens of Mls-2a and Dvbl, respectively . On days 3 to 6 after infection, Thy-1.2-CD4lowTCR-alpha beta + T cells or Thy-1.2-TCR-gamma delta + T cells increased significantly in number and proportion in the liver whereas T cells with these phenotypes were hardly detected in the spleen, lymph nodes, peripheral blood, and peritoneal cavity during the course of the infection . The Thy-1.2-CD4lowTCR-alpha beta T cells contained V beta 3 or V beta 11-bearing cells in high frequencies . The potentially autoreactive V beta 3- or V beta 11-bearing T cells disappeared from the liver on day 7 after infection . Furthermore, the V beta 3+ and V beta 11+ cells but not V beta 8+ cells disappeared after culture for 24 h at 37 degrees C . In vitro stimulation of liver T cells using anti-V beta 11 mAb showed no proliferative response . These results suggest that the potentially autoreactive clones with Thy-1.2-CD4low phenotypes, which increased in number after listerial infection, may be anergized after interaction with self-Ag and may be programmed to die . These potentially autoreactive clones induced in the liver of Listeria-infected mice may not be functionally relevant to the host defense against Listeria.

J Leukoc Biol, 1992 Jul, 52(1), 70 - 9
Listericidal and nonlistericidal mouse macrophages differ in complement receptor type 3-mediated phagocytosis of L . monocytogenes and in preventing escape of the bacteria into the cytoplasm; Drevets DA et al.; Listeria monocytogenes is a facultative intracellular bacterium that escapes phagocytic vesicles and replicates in the cytoplasm, where it becomes coated with F-actin . Macrophages, important anti-Listeria effector cells, are heterogeneous in their ability to kill Listeria . Complement receptor type 3 (CR3) mediates most phagocytosis of Listeria by listericidal macrophages . Experiments described here tested whether nonlistericidal macrophages also phagocytosed Listeria through CR3 and whether the ability of Listeria to escape into the cytoplasm correlated with lack of listericidal activity . We show here that CR3 mediated an average of 66% of the phagocytosis of serum-opsonized Listeria by listericidal peptone-elicited macrophages but only 35% by nonlistericidal thioglycolate-elicited macrophages . In thioglycolate-elicited macrophages, most Listeria were cytoplasmic and actin coated, whereas in peptone-elicited macrophages most were retained in the phagosome . These results indicate that listericidal and nonlistericidal macrophages phagocytose Listeria through different receptors and that nonlistericidal macrophages allow Listeria to escape into the cytoplasm.

J Leukoc Biol, 1992 Jul, 52(1), 130 - 2
Monoclonal antibody NIMP-R10 directed against the CD11b chain of the type 3 complement receptor can substitute for monoclonal antibody 5C6 to exacerbate listeriosis by preventing the focusing of myelomonocytic cells at infectious foci in the liver; Conlan JW et al.; Treatment of mice with a monoclonal antibody (mAb) designated NIMP-R10, directed against the CD11b polypeptide of the CD18/CD11b heterodimeric type 3 complement receptor (CR3), exacerbates listeriosis by preventing myelomonocytic cells from focusing at sites of infected hepatocytes in the liver . Under these conditions an otherwise sublethal Listeria inoculum grows unrestrictedly within hepatocytes and causes death in 3 days . The results obtained with NIMP-R10 are similar to those previously obtained with a different anti-CD11b mAb (5C6), although mAb NIMP-R10 is more effective at enhancing infection . Therefore, both mAbs can be used to analyze host antibacterial defenses in vivo.

Appl Environ Microbiol, 1992 Jul, 58(7), 2255 - 9
Depletion of proton motive force by nisin in Listeria monocytogenes cells; Bruno ME et al.; The basal proton motive force (PMF) levels and the influence of the bacteriocin nisin on the PMF were determined in Listeria monocytogenes Scott A . In the absence of nisin, the interconversion of the pH gradient (Z delta pH) and the membrane potential (delta psi) led to the maintenance of a fairly constant PMF at -160 mV over the external pH range 5.5 to 7.0 . The addition of nisin at concentrations of greater than or equal to 5 micrograms/ml completely dissipated PMF in cells at external pH values of 5.5 and 7.0 . With 1 microgram of nisin per ml, delta pH was completely dissipated but delta psi decreased only slightly . The action of nisin on PMF in L . monocytogenes Scott A was both time and concentration dependent . Valinomycin depleted only delta pH, whereas nigericin and carbonyl cyanide m-chlorophenylhydrazone depleted only delta psi, under conditions in which nisin depleted both . Four other L . monocytogenes strains had basal PMF parameters similar to those of strain Scott A . Nisin (2.5 micrograms/ml) also completely dissipated PMF in these strains.

Tijdschr Diergeneeskd, 1992 Jul 1, 117(13), 375 - 9
{Results of studies with aborted cattle fetuses}; Akkermans JP et al.; The laboratory of the Animal Health Service of South Holland investigated 2410 cases of spontaneous abortion (twins (112) were considered one case) . Seventy-eight afterbirths without foetuses were also examined . The aim of the study was not only to find the cause of abortion but also to see whether there was a relation between the results of the different bacteriological, virological and histological tests used . The presence of IgG in the blood of foetuses older than 5 months was also determined . A micro-organism was isolated from 25% of the foetuses . On the basis of results of other tests, it is probable that microbial infection played a role in a further 21% of the abortions . BHV was isolated in 2.5% of the cases . Actinomyces pyogenes was found in 6% of the foetuses and fungi in 3.5% . More infections with Actinomyces pyogenes, Listeria monocytogenes and fungi were observed when the cattle were kept indoors . It is emphasised that both foetuses as well as placental membranes should be examined, and both foetuses of twins . In stable enzooties in the Netherlands, the following infections should be taken into consideration: Brucella abortus, BHV, BVD, Chlamydia psittaci and Leptospira hardjo . The authors stress the need for a more standardised approach to research, the more so because the results could have consequences not only for monitoring activities (checks for Br . abortus) but also for liability.

J Cell Biol, 1992 Jul, 118(1), 83 - 93
How Listeria exploits host cell actin to form its own cytoskeleton . II . Nucleation, actin filament polarity, filament assembly, and evidence for a pointed end capper; Tilney LG et al.; After Listeria, a bacterium, is phagocytosed by a macrophage, it dissolves the phagosomal membrane and enters the cytoplasm . The Listeria than nucleates actin filaments from its surface . These newly assembled actin filaments show unidirectional polarity with their barbed ends associated with the surface of the Listeria . Using actin concentrations below the pointed end critical concentration we find that filament elongation must be occurring by monomers adding to the barbed ends, the ends associated with the Listerial surface . If Listeria with tails are incubated in G actin under polymerizing conditions, the Listeria is translocated away from its preformed tail by the elongation of filaments attached to the Listeria . This experiment and others tell us that in vivo filament assembly must be tightly coupled to filament capping and cross-bridging so that if one process outstrips another, chaos ensues . We also show that the actin filaments in the tail are capped on their pointed ends which inhibits further elongation and/or disassembly in vitro . From these results we suggest a simple picture of how Listeria competes effectively for host cell actin . When Listeria secretes a nucleator, the host's actin subunits polymerize into a filament . Host cell machinery terminate the assembly leaving a short filament . Listeria overcomes the host control by nucleating new filaments and thus many short filaments assemble . The newest filaments push existing ones into a growing tail . Thus the competition is between nucleation of filaments caused by Listeria and the filament terminators produced by the host.

J Cell Biol, 1992 Jul, 118(1), 71 - 81
How Listeria exploits host cell actin to form its own cytoskeleton . I . Formation of a tail and how that tail might be involved in movement; Tilney LG et al.; After Listeria is phagocytosed by a macrophage, it dissolves the phagosomal membrane and enters the cytoplasm . The Listeria then nucleates actin filaments from its surface . These actin filaments rearrange to form a tail with which the Listeria moves to the macrophage surface as a prelude to spreading . Since individual actin filaments appear to remain in their same positions in the tail in vitro after extraction with detergent, the component filaments must be cross-bridged together . From careful examination of the distribution of actin filaments attached to the surface of Listeria and in the tail, and the fact that during and immediately after division filaments are not nucleated from the new wall formed during septation, we show how a cloud of actin filaments becomes rearranged into a tail simply by the mechanics of growth . From lineage studies we can relate the length of the tail to the age of the surface of Listeria and make predictions as to the ratio of Listeria with varying tail lengths at a particular time after the initial infection . Since we know that division occurs about every 50 min, after 4 h we would predict that if we started with one Listeria in a macrophage, 16 bacteria would be found, two with long tails, two with medium tails, four with tiny tails, and eight with no tails or a ratio of 1:1:2:4 . We measured the lengths of the tails on Listeria 4 h after infection in serial sections and confirmed this prediction . By decorating the actin filaments that make up the tail of Listeria with subfragment 1 of myosin we find (a) that the filaments are indeed short (maximally 0.3 microns in length); (b) that the filament length is approximately the same at the tip and the base of the tail; and (c) that the polarity of these filaments is inappropriate for myosin to be responsible or to facilitate movement through the cytoplasm, but the polarity insures that the bacterium will be located at the tip of a pseudopod, a location that is essential for spreading to an adjacent cell . Putting all this information together we can begin to unravel the problem of how the Listeria forms the cytoskeleton and what is the biological purpose of this tail . Two functions are apparent: movement and pseudopod formation.

J Immunol, 1992 Jul 1, 149(1), 53 - 9
Induction of a cellular immune response to a foreign antigen by a recombinant Listeria monocytogenes vaccine; Schafer R et al.; A recombinant strain of Listeria monocytogenes that stably and constitutively expresses Escherichia coli beta-galactosidase was used as a live vaccine vector . BALB/c mice were immunized orally or parenterally with the recombinant L . monocytogenes, and their cellular and humoral immune responses to beta-galactosidase were measured . Spleen cells taken 1 week after oral inoculation or 5 weeks after oral or parenteral inoculation (with a boost at 4 weeks) showed beta-galactosidase-specific CTL responses . The CTL line derived from mice immunized i.p . was also shown to be class I restricted and Thy-1.2+, CD8+, and TCR alpha beta+ . All mice immunized with the recombinant L . monocytogenes had positive delayed-type hypersensitivity responses to heat-killed L . monocytogenes, but only 15% had a positive delayed-type hypersensitivity reaction to beta-galactosidase . Individual serum samples from mice immunized i.p . or i.v . were tested for antibody to beta-galactosidase . Approximately 11% had low positive titers for beta-galactosidase antibodies . These results demonstrate that both oral and parenteral immunization with recombinant L . monocytogenes results in a cellular immune response to the foreign protein, which is primarily a specific CD8+ CTL response.

J Immunol, 1992 Jul 1, 149(1), 188 - 93
Primary listerial infections are exacerbated in mice administered neutralizing antibody to macrophage colony-stimulating factor; Gregory SH et al.; The serum and tissue levels of macrophage colony-stimulating factor (M-CSF) are elevated in mice during a primary immunologic response to infection by Listeria monocytogenes . Experiments were performed to determine the specific role of M-CSF in the resolution of listerial infections . The bulk of Listeria injected into a mouse i.v . is deposited in the liver . The expression of M-CSF mRNA in the liver increased markedly within 2 h postinfection . Maximum expression was dependent upon the dose of Listeria inoculated . The administration of anti-M-CSF mAb reduced the percentage of Mac-1+ mononuclear phagocytes subsequently found in the livers of infected animals . This reduction correlated inversely with an increase in the number of Listeria associated with both the parenchymal and NPC populations . These results suggest that M-CSF may play an important role in the primary immunologic response to Listeria in the liver by stimulating the production, mobilization, and/or biologic activity of Mac-1+ mononuclear phagocytes.

J Appl Bacteriol, 1992 Jul, 73(1), 53 - 9
A combined PCR and selective enrichment method for rapid detection of Listeria monocytogenes; Fitter S et al.; Development of a routine detection assay for Listeria monocytogenes in foods that uses the polymerase chain reaction (PCR) and enrichment cultures was investigated . Oligonucleotide primers were chosen to amplify a 3' region of L . monocytogenes hlyA gene spanning a conserved HindIII site . PCR detection sensitivity for L . monocytogenes in dilutions of pure enrichment cultures was between 50 and 500 colony forming units . A short enrichment period before PCR amplification allowed detection of the organisms in a range of complex foods contaminated with 10(4) cfu/g . Detection sensitivity for the assay in the presence of chicken skin and soft cheese was determined at 10-100 cfu/g . Utilization of enrichment cultures and PCR allowed identification of the organism within 24 h or 2 days.

J Appl Bacteriol, 1992 Jul, 73(1), 23 - 30
An investigation of the antibacterial effect of carrot on Listeria monocytogenes; Nguyen-The C et al.; Carrot slices immersed in a potassium phosphate buffer (0.1 mol/l, pH 7.0) or carrot tissue macerated in the buffer had a lethal effect on Listeria monocytogenes . This antilisterial activity was suppressed by anaerobiosis, thiol compounds (1 mmol/l) and bovine serum albumin (0.05%) but was not affected by sodium ascorbate (200 mmol/l), propyl gallate (25 mmol/l), catalase (1100 U/ml), superoxide dismutase (357 U/ml), or chelating agents (10 mmol/l) . Free-radical scavengers had no effect at 10 mmol or 50 mmol/l but histidine and diazabenzocyclooctane at 100 mmol/l reduced the antilisterial activity . The addition of Tween 20, 0.05% (v/v), to carrot macerates improved the recovery of the activity in the supernatant liquid after centrifugation at 10,000 g for 2 min . The addition of higher concentrations of the detergent to the macerate reduced the antilisterial activity.

Lab Anim, 1992 Jul, 26(3), 200 - 5
Lymphatic drainage of Listeria monocytogenes and Indian ink inoculated in the peritoneal cavity of the mouse; Marco AJ et al.; The lymphatic drainage of the peritoneal cavity has been investigated by intraperitoneal inoculation of an intracellular bacterium (Listeria monocytogenes) and an inert marker (Indian ink) . The results reveal that both agents are transported, either after phagocytosis by intraperitoneal macrophages or in suspension in the lymph, towards the cranial sternal lymph nodes (Lymphonodi sternales craniales) of the ventral thoracic lymphocentrum (Lymphocentrum thoracicum ventrale) and to the lymph nodes of the mediastinal lymphocentrum (Lymphocentrum mediastinale), prior to systemic dissemination . This mechanism of peritoneal lymph drainage has relevance on experimental studies involving the inoculation of pathogens, and on the investigation of metastatic diffusion of neoplasms from the peritoneum.

Int J Food Microbiol, 1992 Jul, 16(3), 247 - 60
Differentiation of Listeria monocytogenes isolates by using plasmid profiling and multilocus enzyme electrophoresis; Kolstad J et al.; Three hundred and seven Listeria monocytogenes isolates from various origins (clinical sources, raw chicken, seafoods, dairy and meat products and processing environments) were screened for plasmids . The overall frequency of L . monocytogenes isolates containing plasmids was 77% . The highest percentages of plasmid positive isolates were found from meat (89%), chicken (81%) and dairy products (64%), while clinical isolates had the lowest plasmid percentage (28%) . Seven sizes of plasmids (21, 24, 27, 35, 40, 47 and 52 MDa) were distinguished . All sizes were represented in the meat isolates, clinical isolates contained only two of the plasmid sizes, while several different sizes of plasmids were found in the isolates from other origins . Plasmid profiling divided the isolates into ten plasmid pattern types . Multilocus enzyme electrophoresis of 75 isolates demonstrated 12 distinctive multilocus genotypes (ETs) which clustered into two groups: cluster A including serotype 1 and 4 isolates, and isolates not typable by Difco antisera serotype 1 and 4, and cluster B containing only serotype 1 isolates . No relationship between ETs and plasmid profiles could be demonstrated.

Int J Food Microbiol, 1992 Jul, 16(3), 173 - 82
Is any strain of Listeria monocytogenes detected in food a health risk?
Hof H, Rocourt J.
Listeria spp . have been isolated from various food items . This fact does not mean in any case a true health risk . A balanced appraisal should be based on quantitative as well as qualitative aspects . Actually, there is still an open debate whether a limited number of Listeria has to be tolerated at least in certain food items . In addition, the pathogenic potency of an isolate may be put into account . Pathogenicity of various Listeria spp . definitely varies . Most Listeria spp., except Listeria monocytogenes, can be regarded as harmless to man . Also, not all strains of L . monocytogenes are pathogenic: rough variants possess only reduced virulence; non-hemolytic mutants have completely lost their pathogenic potency . Furthermore, several other virulence factors may be lost under natural conditions, so that among the majority of hemolytic, pathogenic isolates there may be others which are non-pathogenic or of low virulence only . Unfortunately, these strains actually cannot be recognized and characterized by common laboratory tests, so that animal pathogenicity seems to be the only way to get a final conclusion on the health risk of an isolate of L . monocytogenes from any food . The problem raised by this is which animal test is able to predict a true health risk either for normal hosts or for immunocompromised patients?

J Comp Pathol, 1992 Jul, 107(1), 1 - 9
A microbiological, histopathological and immunohistological study of the intragastric inoculation of Listeria monocytogenes in mice; Marco AJ et al.; The course of murine infection after intragastric inoculation of L . monocytogenes was investigated by immunocytochemical, histopathological and microbiological techniques . L . monocytogenes antigen was observed in epithelial cells of intestinal mucosa overlying Peyer's patches, but not in mucosa devoid of them . This suggests that penetration of L . monocytogenes into the host organism may take place through epithelium overlying Peyer's patches . The efficiency of bacterial penetration appeared to be low, as shown by the small amounts of L . monocytogenes antigen detected and the low counts of bacteria in organs . Gross or histopathological lesions in the intestinal tract were not observed . The presence of L . monocytogenes in spleen, liver and in maxillary and mesenteric lymph nodes, confirmed that the systemic course of infection by this route of inoculation is similar to that of the parenteral routes . The results emphasize the subclinical character of murine listeriosis by the oral route.

Res Vet Sci, 1992 Jul, 53(1), 64 - 7
Pyrolysis mass spectrometry of Listeria monocytogenes isolates from sheep; Low JC et al.; Forty-eight isolates of Listeria monocytogenes from sheep and silage, involved in five small outbreaks of listeriosis, were compared by pyrolysis mass spectrometry (PyMS) . The method clustered isolates from single animals, and showed that epidemiologically associated isolates were closely related to each other . PyMS is a simple technique capable of analysing large numbers of samples daily, and its application in veterinary studies should help to elucidate the epidemiology of listeriosis.

Microb Pathog, 1992 Jul, 13(1), 25 - 35
Dissociation of macrophage cytolysis and ability to transfer anti-listeria resistance by concanavalin A-stimulated spleen cells; Roll JT et al.; In this study, we determined whether spleen cells from Listeria monocytogenes-immunized mice were cytolytic for Listeria-infected macrophages . Spleen cells freshly obtained from immunized donors were unable to lyse Listeria-infected macrophages unless they were first stimulated in vitro for 2-3 days with Concanavalin A (ConA) or L . monocytogenes . Spleen cells from non-immunized mice developed cytolytic activity after incubation with ConA, but not with L . monocytogenes . Cytolytic spleen cells demonstrated an equivalent ability to lyse uninfected and Listeria-infected thioglycollate elicited peritoneal macrophages . Maximal cytolysis required co-incubation of effector and target cells for 18-20 h . Spleen cell culture supernatants did not lyse macrophages, suggesting that cytolysis required direct contact . Preincubation of immune spleen cells with ConA decreased their ability to transfer anti-listeria resistance in the spleens, but not the livers of recipient mice . Depletion of CD4+ or CD8+ cells did not significantly reduce the ability of ConA-incubated Listeria-immune spleen cells to transfer resistance . Despite being cytolytic for Listeria-immune infected macrophages, ConA-stimulated non-immune spleen cells did not transfer anti-listeria resistance . These results indicate that cytolytic cells can be generated by short-term incubation of spleen cells with antigen or mitogen . The dissociation between in vitro cytolytic activity and ability to transfer protection, however, suggests that the two biological activities are not inextricably linked.

J Immunol, 1992 Jun 15, 148(12), 3978 - 85
Administration of anti-IL-4 monoclonal antibody 11B11 increases the resistance of mice to Listeria monocytogenes infection; Haak-Frendscho M et al.; The role of endogenous IL-4 in resistance to Listeria monocytogenes infection was investigated by in vivo administration of an anti-IL-4 mAb (11B11) . Mice treated with 0.01 to 0.4 mg of anti-IL-4 mAb before L . monocytogenes challenge demonstrated a significantly reduced peak bacterial burden in their livers and spleens and accelerated bacterial clearance from these organs . In addition, histopathologic damage to the liver was reduced . Maximal protection was achieved by i.p . injection of 0.1 mg of anti-IL-4 mAb 2 or 24 h before L . monocytogenes challenge; treatment with anti-IL-4 mAb after injection of L . monocytogenes had no effect on antilisterial resistance . Anti-IL-4 mAb-treated and control Listeria-infected mice exhibited similar patterns of IFN-gamma, IL-2, and IL-4 mRNA, as determined by polymerase chain reaction amplification of RNA extracted from spleen cells . In both anti-IL-4 mAb-treated and control mice, IFN-gamma, IL-2, and IL-4 mRNA were produced within 4 h after challenge . Cytokine mRNA levels were similar for anti-IL-4 mAb-treated and control mice, except for the greater amount of IFN-gamma mRNA in the anti-IL-4 mAb-treated mice at 4 h after L . monocytogenes challenge . IFN-gamma and IL-2 mRNA levels were sustained for at least 5 days, whereas IL-4 mRNA was undetectable by 3 days after challenge . There were no significant differences in the amounts of IL-4 and IFN-gamma detected in culture supernatants of spleen cells from anti-IL-4 mAb-treated and control Listeria-infected mice . These results suggest that endogenous IL-4, a cytokine thought to be produced principally by Th2 cells, has a deleterious effect on host defense against the facultative intracellular pathogen L . monocytogenes . Administration of an anti-IL-4 mAb increases antilisterial resistance without causing a detectable shift to a Th1 type of cytokine response.

J Vet Med Sci, 1992 Jun, 54(3), 461 - 3
Prevalence of Listeria (spp.) in wild rats captured in the Kanto area of Japan; Inoue S et al.; In the Kanto area a total of 245 wild rats were captured . All rats captured in Ikebukuro (110 rats) and 9 out of 41 rats in Yokohama were Rattus rattus, and all other 126 rats were Rattus norvegicus . In Kashima and Ikebukuro, listeria was isolated from 28 rats (77.8%) and 27 rats (24.5%), respectively, but in the other 4 areas listeria was isolated from 0-7% rats . Listeria monocytogenes was isolated from 12 rats (10.9%) captured in Ikebukuro and 2 rats in Kashima and Numazu . The frequent isolation of L . monocytogenes in buildings suggests the possibility of R . rattus as a reservoir of L . monocytogenes and the continual environmental contamination in buildings by L . monocytogenes.

Biomed Environ Sci, 1992 Jun, 5(2), 142 - 8
Altered host resistance to Listeria monocytogenes in mice exposed to 1-chloroacetophenone (CN) vapours; Kumar P et al.; Short term repeated exposure of 1-chloroacetophenone (CN) vapours at a concentration of 0.153 mg per litre for 15 minutes daily on 10 consecutive days in Swiss albino male mice resulted in increased mortality to Listeria monocytogenes . Significantly elevated bacterial growth was observed in the spleen and liver of the CN exposed animals . The increased bacterial count in these organs was evident within 4-6 days post challenge as compared to vehicle exposed infected and unexposed infected animals . Increased susceptibility to infection has been considered to be the function of immune alteration due to cumulative short term effects of CN vapour inhalation . This may be attributed to immunotoxic effects of CN on T-cells mediated macrophage functions.

Appl Environ Microbiol, 1992 Jun, 58(6), 2096 - 8
Thermotolerance of heat-shocked Listeria monocytogenes in milk exposed to high-temperature, short-time pasteurization; Bunning VK et al.; The effect of prior heat shock (48 degrees C for 15 min) on the thermotolerance of Listeria monocytogenes at the minimal high-temperature, short-time (71.7 degrees C for 15 s) parameters required by the Pasteurized Milk Ordinance was examined . The mean D71.7 degrees C value for heat-shocked L . monocytogenes was 4.6 +/- 0.5 s (control D = 3.0 +/- 1.0 s); the ratio of D to control D was 1.5 . The increased thermotolerance of heat-shocked Listeria cells was not significant and appeared unlikely to have practical implications, in terms of risk assessment, for the safety of pasteurized milk.

Appl Environ Microbiol, 1992 Jun, 58(6), 2011 - 5
Evaluation of the Organon-Teknika MICRO-ID LISTERIA system; Bannerman E et al.; The MICRO-ID LISTERIA system, designed to identify Listeria isolates to species level within 24 h, was compared with conventional biochemical identification . MICRO-ID LISTERIA used in combination with the CAMP test correctly identified 409 (98.8%) of 414 strains isolated from human, animal, food, and environmental sources belonging to the seven species currently defined within the genus Listeria . The kit was easy to use and simple to interpret . However, 8 of the 15 tests (i.e., phenylalanine deaminase, hydrogen sulfide, indole, ornithine decarboxylase, lysine decarboxylase, malonate, urease, and o-nitrophenyl-beta-D-galactopyranoside) were considered superfluous for the differentiation of Listeria spp . The CAMP test was indispensable when using the MICRO-ID LISTERIA system, in particular to differentiate CAMP test-positive L . monocytogenes from the nonhemolytic, rhamnose-positive L . innocua . The hemolytic L . seeligeri and L . ivanovii strains and the nonhemolytic, non-rhamnose-acidifying L . welshimeri strains could also be differentiated from one another only on the basis of their CAMP test results . The very few strains of L . grayi and L . murrayi were easily differentiated from the other nonhemolytic species . Catalase-negative cocci should not be tested, because 12 out of 19 catalase-negative strains (all enterococci) in our test were misidentified as Listeria spp . The MICRO-ID LISTERIA system identified strains within 18 to 24 h and is thus less time-consuming than conventional tests . The system could, therefore, be used together with correctly done CAMP tests for the rapid identification of Listeria isolates, especially food and environmental isolates, for which rapid species differentiation is important.

Appl Environ Microbiol, 1992 Jun, 58(6), 1924 - 9
Monoclonal antibody specific for Listeria monocytogenes associated with a 66-kilodalton cell surface antigen; Bhunia AK et al.; A monoclonal antibody (MAb), EM-7G1, specific for Listeria monocytogenes was developed by using a previously developed MAb, C11E9 (A . K . Bhunia, P . H . Ball, A . T . Fuad, B . W . Kurz, J . W . Emerson, and M . G . Johnson, Infect . Immun . 59:3176-3184, 1991), to mask epitopes shared by L . monocytogenes and Listeria innocua in a 66-kDa cell surface protein . MAb EM-7G1 was an immunoglobulin subclass G1 antibody with kappa light chains . This MAb reacted with all 34 strains of L . monocytogenes tested and showed no cross-reaction with other Listeria spp . or other gram-positive or gram-negative organisms tested by enzyme-linked immunosorbent assay, dot blotting, and colony blotting . A second MAb, EM-6E11, reacted with all Listeria spp . tested but no other bacteria . In a Western blot (immunoblot) assay, EM-7G1 reacted with a crude cell surface protein of 66 kDa with a pI value of 6.7, while EM-6E11 reacted with two protein bands of 43 and 94 to 97 kDa with pI values of 4.0 and 4.3, respectively . Results with trypsin or pronase treatments indicated that the cell antigen reacting with EM-7G1 was on the surface of L . monocytogenes V7 and Scott A cells.

Appl Environ Microbiol, 1992 Jun, 58(6), 1857 - 60
API Listeria, a new and promising one-day system to identify Listeria isolates; Bille J et al.; API Listeria is a new 10-test strip for 24-h biochemical identification of Listeria isolates . With this commercial system, 85% of 646 Listeria strains, including atypical isolates selected for this study, were recognized at the species and subspecies level without a complementary test . A new test differentiates Listeria monocytogenes from L . innocua on the basis of the absence of arylamidase from the former . With this system, 97.7% (252 of 258) of the L . monocytogenes strains tested were correctly identified and differentiated from 99.4% (175 of 176) of the L . innocua strains also tested . Gram-positive bacteria other than Listeria spp . gave quite different biochemical patterns . This system considerably reduced the time needed for conventional identification, since results were available within 18 to 24 h.

Clin Exp Immunol, 1992 Jun, 88(3), 492 - 8
Effect of macrophage activation on killing of Listeria monocytogenes . Roles of reactive oxygen or nitrogen intermediates, rate of phagocytosis, and retention of bacteria in endosomes; Higginbotham JN et al.; The role of macrophage activation in the killing of L . monocytogenes is unclear . Some studies suggest that activation for enhanced production of reactive oxygen and nitrogen intermediates may not be of central importance . Recent data have indicated an important role for interferon-gamma (IFN-gamma) induced retention of L . monocytogenes in endosomes . Data from the present study indicate that proteose peptone-elicited macrophages from DBA2/J, CD-1, and C3H/HeN mice are listericidal . Activation of these cells in vitro for 20 h by IFN-gamma (20 or 500 U/ml) increased H2O2 or nitrite production, but did not increase the number of L . monocytogenes killed during a subsequent 6-h or 7-h culture . Incubation of macrophages with IFN-gamma plus lipopolysaccharide (LPS) caused greater activation and increased the number of Listeria killed during a 6-h or 7-h culture . However, this seems primarily attributable to enhanced phagocytosis . Proteose peptone-elicited macrophages were significantly more effective than resident macrophages in preventing the escape of L . monocytogenes from endosomes into the cytoplasm . This capability was not significantly enhanced by IFN-gamma in vitro, but was enhanced by IFN-gamma plus LPS . This correlates well with the effects of these activation stimuli on killing of L . monocytogenes by proteose peptone-elicited macrophages . These results indicate that enhanced retention of L . monocytogenes in endosomes is induced by proteose peptone elicitation and that further macrophage activation in vitro by IFN-gamma does not improve listericidal activity.

J Infect Dis, 1992 Jun, 165(6), 1094 - 102
Diminished in vitro production of interleukin-1 and tumor necrosis factor-alpha during acute visceral leishmaniasis and recovery after therapy; Ho JL et al.; Disturbance of T cell-mediated immunity has been reported in acute visceral leishmaniasis (AVL) . In a study of 16 patients with AVL, defective production of interleukin-1 (IL-1) by peripheral blood mononuclear cells was demonstrated in response to leishmania antigens, heat-killed Listeria organisms, and lipopolysaccharide when compared to posttherapy values or controls . This global defect in IL-1 production was corrected after successful therapy . Twelve of 16 patients responded with a greater than or equal to 2.5-fold increase in IL-1 production that correlated with clinical cure, P less than .01 . Depressed production of tumor necrosis factor (TNF) was leishmania antigen-specific and similarly recovered after therapy . In vitro TNF production during the follow-up period did not correlate with clinical status but high serum levels were associated with AVL . Since T cells are activated by processed antigens presented on class II major histocompatibility molecules and by newly synthesized IL-1, defective IL-1 production may contribute to the immunosuppression observed in AVL.

Res Microbiol, 1992 Jun, 143(5), 507 - 12
A comparative study of randomly amplified polymorphic DNA analysis and conventional phage typing for epidemiological studies of Listeria monocytogenes isolates; Mazurier SI et al.; The analysis of RAPD profiles generated by PCR with a single 10-mer, HLWL74, was compared to bacteriophage susceptibility data for epidemiological typing of Listeria monocytogenes strains . A total of 104 L . monocytogenes strains was screened, all from serogroup 1 or serotype 4b . Of these, 53 had been isolated during 6 different listeriosis outbreaks . The remaining 51 strains were chosen randomly from our collection . A total of 38 RAPD types were observed, although each epidemic group of strains isolated during one of these outbreaks displayed a specific RAPD profile . For 98% of the strains isolated during outbreaks, the correlation between RAPD typing and phage typing was complete . Only one strain, typed as epidemic by phage typing, was clearly distinguishable from the others by RAPD analysis . Among the 51 strains not related to an outbreak, 12 were linked to epidemic groups by RAPD analysis . Two of these rearrangements were supported by phage typing . The remaining 10 strains could be excluded by phage typing from any of the epidemic groups studies . Considering all 104 isolates, the decision to relate a strain to a particular epidemic group or to exclude a strain from any epidemic group was the same for 92 isolates, using either phage typing or RAPD analysis . The RAPD analysis, which is quick, simple and suited for automation, is proposed as an attractive alternative for phage typing in epidemiological studies of listeriosis.

Res Microbiol, 1992 Jun, 143(5), 499 - 505
Typing of Listeria strains by random amplification of polymorphic DNA; Mazurier SI et al.; The polymerase chain reaction (PCR) was used to obtain randomly amplified polymorphic DNA (RAPD) profiles for typing of Listeria strains . In this procedure, whole cells were incubated in the reaction mixture . The discriminating ability of a randomly designed 10-mer primer, HLWL74, was assessed . A total of 60 collection strains of Listeria, encompassing all 7 Listeria species and all known serovars was submitted to PCR with the primer HLWL74 . Upon agarose gel electrophoresis, 29 different banding profiles were reproducibly obtained . No common profiles were recorded for strains from different Listeria species . For various groups of strains sharing the same serotype (e.g . 4b, 1/2a, 1/2b), RAPD analysis could generate further subdivision . On the other hand, some strains from different serotypes produced identical RAPD profiles with the primer HLWL74 . The RAPD typing method from whole cells is proposed as an attractive alternative for other Listeria typing systems, and the 10-mer HLWL74 as a primer to include in a forthcoming set of standard primers for RAPD typing of Listeria isolates.

Res Microbiol, 1992 Jun, 143(5), 489 - 98
Immunoaffinity purification, stabilization and comparative characterization of listeriolysin O from Listeria monocytogenes serotypes 1/2a and 4b; Matar GM et al.; We developed a simple and highly effective procedure for stabilizing the haemolytic activity of listeriolysin O (LLO) from Listeria monocytogenes after immunoaffinity purification . The haemolytic activity of LLO was stabilized by eluting it directly into tubes containing an alkaline buffer (5 mM lysine, 140 mM KCl, 50% ethylene glycol, pH 11.5) . The purified LLO retained 100% of its haemolytic activity after 6 weeks of storage at -20 degrees C . LLO purified from a strain of L . monocytogenes serotype 1/2a (ATCC 43249) and LLO purified from a strain of L . monocytogenes serotype 4b (F 2365) isolated from a Mexican-style cheese, showed no significant differences in pH and temperature stability . When incubated in buffers at pH values from 4 to 12 at 4 degrees C and 25 degrees C, LLO from serotypes 1/2a and 4b retained maximal haemolytic activity at pH 8 after 4 h of incubation . LLO from both serotypes lost their haemolytic activity after incubation at 50 degrees C for 25 min.

Int J Food Microbiol, 1992 Jun, 16(2), 157 - 60
The incidence of Listeria species in retail foods in Japan; Ryu CH et al.; Meat, fish and vegetable products obtained at retail shops in or around Tokyo were examined for Listeria contamination . Listeria spp . were isolated from 43 (56.6%) out of 76 samples of meat products . L . monocytogenes occurred in 26 (34%) of the samples, L . monocytogenes was isolated from 7 (6.1%) out of 114 samples of fish and fish products including 'ready-to-eat' foods . Listeria was not isolated from any of 21 samples of vegetable and vegetable product including 'ready-to-eat' foods investigated.

Int J Food Microbiol, 1992 Jun, 16(2), 153 - 6
Incidence of Listeria monocytogenes in fresh foods in Barcelona (Spain); de Simon M et al.; From September 1989 to March 1990, a study of Listeria spp . was carried out on 311 samples of raw foodstuffs from markets and other establishments in the city of Barcelona . These foodstuffs included vegetables (103 samples), minced meats from pork, beef and poultry (168 samples) and bivalve molluscs (40 samples) . L . monocytogenes was isolated in 7.8% of the vegetable samples, 17.3% of the minced meats and in 7.5% of bivalve molluscs . The most frequent serovars were 1/2 and 4 . Other species isolated were L . innocua, L . welschimeri and L . seeligeri.

J Exp Med, 1992 Jun 1, 175(6), 1531 - 8
CD8+ T cells specific for a single nonamer epitope of Listeria monocytogenes are protective in vivo; Harty JT et al.; Class I major histocompatibility complex (MHC)-restricted CD8+ T cells have been demonstrated to be effective mediators of both acquired and adoptive immunity to the intracellular bacterium Listeria monocytogenes . We have recently determined that L . monocytogenes-infected H-2d mice recognize a nonamer peptide, residues 91-99, of the secreted protein listeriolysin O (LLO), in a H-2Kd-restricted fashion . In this report we have generated CD8+ T cell lines with specificity for LLO 91-99 in the context of H-2Kd by in vitro stimulation with P815 (H-2d) cells transfected with LLO . These CD8+ lines have been generated from immune donors after sublethal infection with L . monocytogenes, or after in vivo immunization with syngeneic spleen cells coated with synthetic LLO 91-99 peptide . LLO-specific CD8+ T cells derived from either protocol were capable of significant protection against L . monocytogenes infection . The in vivo protection by these CD8+ T cell lines has been shown to be solely due to recognition of LLO 91-99 in the context of H-2Kd . These studies demonstrate that CD8+ T cell immunity to a single, naturally produced peptide epitope has the potential for significant protection in a bacterial infection . Thus, the allele-specific motif approach to epitope prediction has identified a naturally produced bacterial epitope with biological relevance.

J Nutr, 1992 Jun, 122(6), 1219 - 31
Dietary fat influences Ia antigen expression and immune cell populations in the murine peritoneum and spleen; Huang SC et al.; Peritoneal cells (PEC) and splenocytes were obtained from Listeria monocytogene (LM)-infected or noninfected mice fed a 20% fat diet rich in either (n-3) polyunsaturated fatty acids {(n-3) PUFA diet}, linoleate {(n-6) PUFA diet}, oleate (MONO diet), or saturated fatty acids (SAT diet) for 6 wk and were assessed for T cells, B cells, macrophages and Ia expression by flow cytometric analysis . In the peritoneum of noninfected mice, dietary fat did not affect total cell yield or the percentage of B cells, macrophages or Ia+ cells, but the (n-3) PUFA-fed group had a greater percentage of T cells than did the other groups . Among the LM-infected mice, the (n-3) PUFA-fed group generally had the highest percentage of B cells and the lowest percentages of T cells, macrophages and Ia+ cells in the peritoneum . Listeria monocytogene infection elevated peritoneal T cell numbers in all mice except the (n-3) PUFA-fed group . The density of Ia molecules on PEC was 40% lower in mice fed the (n-3) PUFA diet . In the spleen, dietary fat also influenced the immune cell populations and Ia+ cells . Two-color staining of spleen cells revealed that Ia+ splenocytes were predominately B cells . These data demonstrate that dietary fats influence Ia expression and immune cell populations and that the effects observed in one immune tissue or cell type may not be readily extrapolated to others.

Nature, 1992 May 21, 357(6375), 257 - 60
The rate of actin-based motility of intracellular Listeria monocytogenes equals the rate of actin polymerization; Theriot JA et al.; The Gram-positive bacterium Listeria monocytogenes is a facultative intracellular pathogen capable of rapid movement through the host cell cytoplasm . The biophysical basis of the motility of L . monocytogenes is an interesting question in its own right, the answer to which may shed light on the general processes of actin-based motility in cells . Moving intracellular bacteria display phase-dense 'comet tails' made of actin filaments, the formation of which is required for bacterial motility . We have investigated the dynamics of the actin filaments in the comet tails using the technique of photoactivation of fluorescence, which allows monitoring of the movement and turnover of labelled actin filaments after activation by illumination with ultraviolet light . We find that the actin filaments remain stationary in the cytoplasm as the bacterium moves forward, and that length of the comet tails is linearly proportional to the rate of movement . Our results imply that the motile mechanism involves continuous polymerization and release of actin filaments at the bacterial surface and that the rate of filament generation is related to the rate of movement . We suggest that actin polymerization provides the driving force for bacterial propulsion.

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