Res Microbiol, 1995 Jan, 146(1), 35 - 49 Typing Listeria monocytogenes: a comparison of random amplification of polymorphic DNA with 5 other methods; Boerlin P et al.; One hundred Listeria monocytogenes strains were typed by random amplification of polymorphic DNA (RAPD) with three different primers, and the results were compared with those obtained by serotyping, ribotyping, multilocus enzyme electrophoresis, restriction enzyme analysis and phage typing . The RAPD patterns of strains appear to be stable during epidemics even over periods of several years . Reproducibility of the RAPD patterns was good . The discriminatory power of RAPD typing was the best among all the methods tested . RAPD is therefore a very promising tool in the study of listeriosis epidemiology . However, the problems related to the standardization of the technique first have to be resolved before the wide use of RAPD is possible. Res Microbiol, 1995 Jan, 146(1), 21 - 34 Evaluation of a restriction fragment length polymorphism typing method for Listeria monocytogenes; Ridley AM; The results of an evaluation of restriction fragment length polymorphism (RFLP) typing for Listeria monocytogenes are presented . The method depends on the use of cloned DNA fragments from an L . monocytogenes (serovar 4b) strain to probe Southern blotted NciI restriction fragments derived from L . monocytogenes strains . Analyses of 862 isolates of serogroups 1/2, 3 and 4 were performed and a total of 32 RFLP patterns were observed . Interstrain RFLPs were common within serogroup 1/2 and the numerical index of discriminatory power for this group was 0.883 . Serogroup 4 strains were divided into two major and three minor RFLP types, suggesting a high level of genotypic homogeneity, and the numerical index of discriminatory power was correspondingly low . The technique was found to be highly reproducible, and the stability of patterns was demonstrated by analyses of passaged strains and multiple isolates of the same strain from related specimens . RFLP typing is of value in epidemiological investigations involving strains of serogroup 1/2. Digestion, 1995, 56(2), 159 - 64 Changes in bacterial phagocytosis of macrophages in experimental ulcerative colitis; Ohkusa T et al.; We previously reported that numerous macrophages which phagocytosed dextran sulfate sodium were observed to have accumulated in the mucosal lesions and in the spleen in experimental ulcerative colitis induced in mice with dextran sulfate sodium . In this paper, we investigated the bacterial phagocytic ability of macrophages which were isolated from spleens of mice treated with 3% dextran sulfate sodium for 6 months . In this model, the number of phagocytosed bacteria (Listeria monocytogenes) and the phagocytic index were significantly decreased . The phagocytic ability of splenic macrophages obtained from nontreated mice was also evaluated by incubating with dextran sulfate sodium in vitro, and adding bacteria . The number of phagocytosed bacteria and the phagocytic index were also significantly decreased . These observations suggest that the decrease in bacterial phagocytosis in this model by macrophages that phagocytosed dextran sulfate sodium indicates a decline of the mucosal defense system to bacteria. Cell Motil Cytoskeleton, 1995, 30(1), 38 - 49 Listeria monocytogenes intracellular migration: inhibition by profilin, vitamin D-binding protein and DNase I; Sanger JM et al.; Infection of host cells by Listeria monocytogenes results in the recruitment of cytoplasmic actin into a tail-like appendage that projects from one end of the bacterium . Each filamentous actin tail progressively lengthens, providing the force which drives the bacterium in a forward direction through the cytoplasm and later results in Listeria cell-to-cell spread . Host cell actin monomers are incorporated into the filamentous actin tail at a discrete site, the bacterial-actin tail interface . We have studied the consequences of microinjecting three different actin monomer-binding proteins on the actin tail assembly and Listeria intracellular movement . Introduction of high concentrations of profilin (estimated injected intracellular concentration 11-22 microM) into infected PtK2 cells causes a marked slowing of actin tail elongation and bacterial migration . Lower intracellular concentrations of two other injected higher affinity monomer-sequestering proteins, Vitamin D-binding protein (DBP; 1-2 microM) and DNase I (6-7 microM) completely block bacterial-induced actin assembly and bacterial migration . The onset of inhibition by each protein is gradual (10-20 min) indicating that the mechanisms by which these proteins interfere with Listeria-induced actin assembly are likely to be complex . To exclude the possibility that Listeria recruits preformed actin filaments to generate the tails and that these monomer-binding proteins act by depolymerizing such performed actin filaments, living infected cells have been injected with fluorescently labeled phalloidin (3 microM) . Although the stress fibers are labeled, no fluorescent phalloidin is found in the tails of the moving bacteria . These results demonstrate that Listeria-induced actin assembly in PtK2 cells is the result of assembly of actin monomers into new filaments and that Listeria's ability to recruit polymerization competent monomeric actin is very sensitive to the introduction of exogenous actin monomer-binding proteins. Clin Infect Dis, 1995 Jan, 20(1), 66 - 72 An epidemic of food-borne listeriosis in western Switzerland: description of 57 cases involving adults; Bula CJ et al.; This article describes 57 cases of listeriosis that occurred in adults in western Switzerland during an outbreak associated with the consumption of a soft cheese . Twenty-one percent of the cases were of bacteremia, 40% were of meningitis, and 39% were of meningoencephalitis . Overall, 42% of the patients had an underlying disease and 54% were > 65 years of age . Patients with bacteremia were significantly older than those with meningitis or meningoencephalitis (median ages, 75, 69, and 55 years, respectively) . The epidemic strain, defined by phage typing, was isolated in three-quarters of the listerial cases observed during the epidemic period and did not appear to differ significantly from the nonepidemic strains in terms of virulence . The overall mortality associated with the 57 cases was 32% . Among the patients' characteristics, age and type of clinical presentation were independent predictors of death in a multivariate logistic regression model (pseudo-r2 {coefficient of determination}, .26; both P values < .05), and a presentation of meningoencephalitis was associated with an increased death risk (odds ratio, 6.5; 95% confidence interval, 1.1-39.5; P < .05) . Neurological sequelae developed in 30% of the survivors of CNS listeriosis. J Formos Med Assoc, 1995 Jan-Feb, 94(1-2), 19 - 22 Antibiotic therapy for Listeria monocytogenes bacteremia; Hung CC et al.; Listeria monocytogenes has been recognized as an important pathogen in immunocompromised patients, but it has been rarely reported in Taiwan . We reviewed 13 cases of L . monocytogenes bacteremia at National Taiwan University Hospital over a 12-year period . All of the patients had underlying diseases . Fever was the most common presenting symptom, and neurologic signs were found in 6 patients . Most of the patients received penicillin G, ampicillin or piperacillin with an aminoglycoside . Corticosteroids were used in 9 of 13 patients . The overall mortality directly due to L . monocytogenes bacteremia was 31% . However, patients treated with cephalosporins or oxacillin had higher mortality than those treated with penicillin G, ampicillin or piperacillin (p = 0.05) . Given the increasing number of immunosuppressed patients in Taiwan, it is likely that more cases will be encountered . Physicians in Taiwan should be aware of L . monocytogenes bacteremia and its treatment. Microbiol Immunol, 1995, 39(5), 343 - 9 Correlation between the presence of virulence-associated genes as determined by PCR and actual virulence to mice in various strains of Listeria spp; Nishibori T et al.; Five chromosomal genes, prfA, plcA, hlyA, mpl and plcB, are implicated in the virulence of Listeria monocytogenes and some of these genes have been used for the identification of bacteria by polymerase chain reaction (PCR) . Using 6 strains of L . monocytogenes and 3 L . innocua strains, the relationship was examined between the presence of five virulence-associated genes and actual virulence to mice in terms of 50% lethal dose (LD50), bacterial viability in the organ of infected mice and the intracellular growth in cultured macrophages . None of the five genes could be amplified by PCR in all the L . innocua strains and they were actually avirulent to mice . All L . monocytogenes strains were shown to be virulent and to have intact virulence-associated genes except for the strain ATCC15313 . This particular strain was revealed to be avirulent and defective in hlyA and plcA in PCR amplification . It was suggested that PCR detection of genes prfA, mpl, or plcB may not be sufficient to detect virulent strains of L . monocytogenes . It appeared that the ability to produce listeriolysin O (LLO), which is encoded by hlyA, was critical for the expression of virulence regardless of the amount of LLO produced. Vet Rec, 1994 Dec 24-31, 135(26), 615 - 7 Primary cutaneous listeriosis in adults: an occupational disease of veterinarians and farmers; McLauchlin J et al.; Seventeen cases of cutaneous listeriosis in adults are reviewed . The condition appeared as papular or pustular lesions on the arms or hands, and was most often acquired as an occupational hazard from infected animals . The cases were all mild and were resolved successfully . However, listeric infections are potentially fatal, and as the initial cause of the lesion may be unknown, it is recommended that veterinarians and farmers should have suspect lesions examined microbiologically. J Exp Med, 1994 Dec 1, 180(6), 2209 - 18 Delivery of a viral antigen to the class I processing and presentation pathway by Listeria monocytogenes; Ikonomidis G et al.; Listeria monocytogenes is a facultative intracellular pathogen that grows in the cytoplasm of infected host cells . We examined the capacity of L . monocytogenes to introduce influenza nucleoprotein (NP) into the class I pathway of antigen presentation both in vitro and in vivo . Recombinant L . monocytogenes secreting a fusion of listeriolysin O and NP (LLO-NP) targeted infected cells for lysis by NP-specific class I-restricted cytotoxic T cells . Antigen presentation occurred in the context of three different class I haplotypes in vitro . A hemolysin-negative L . monocytogenes strain expressing LLO-NP was able to present in a class II-restricted manner . However, it failed to target infected cells for lysis by CD8+ T cells, indicating that hemolysin-dependent bacterial escape from the vacuole is necessary for class I presentation in vitro . Immunization of mice with a recombinant L . monocytogenes strain that stably expressed and secreted LLO-NP induced NP-specific CD8+ cytotoxic T lymphocytes . These studies have implications for the use of L . monocytogenes to deliver potentially any antigen to the class I pathway in vivo. Infect Immun, 1994 Dec, 62(12), 5608 - 13 Characterization of Listeria monocytogenes pathogenesis in a strain expressing perfringolysin O in place of listeriolysin O; Jones S et al.; Listeriolysin O (LLO) is a pore-forming cytolysin that enables Listeria monocytogenes to escape from a host cell vacuole . The structural gene for the related cytolysin perfringolysin O (pfo) was cloned downstream from the promoter for hly, the gene encoding LLO, both on a plasmid and on the L . monocytogenes chromosome . Both strains secreted active PFO, although regulation was not identical to that of LLO . The chromosomal PFO-expressing strain was characterized for intracellular growth and cell-to-cell spread . It escaped from a host cell vacuole with 64% efficiency compared with the wild type as determined by immunofluorescent staining of bacteria for F-actin, a marker for entry into the cytoplasm . In addition, it replicated intracellularly with a doubling time similar to that of the wild type for 5 h, after which growth was aborted because of a cytotoxic effect on the host cell and influx of extracellular gentamicin . The chromosomal PFO strain was able to plaque in mouse L2 fibroblasts, but it did so at 20% efficiency compared with the wild type and the plaques were significantly smaller . Both strains expressing PFO were completely avirulent in mice . These results indicate that PFO can mediate escape from a host cell vacuole but cannot complement an hly deletion strain for virulence. J Clin Microbiol, 1994 Dec, 32(12), 2936 - 43 Comparison of ribotyping and multilocus enzyme electrophoresis for subtyping of Listeria monocytogenes isolates; Graves LM et al.; Ribotyping was compared with multilocus enzyme electrophoresis (MEE) for subtyping 305 Listeria monocytogenes isolates from clinical and nonclinical sources . For ribotyping, EcoRI-restricted genomic DNA fragments of L . monocytogenes strains were separated by agarose gel electrophoresis, and Southern blots were probed with a cloned Escherichia coli rrnB operon (plasmid pKK3535) labeled with digoxigenin . The L . monocytogenes isolates were divided into 28 distinct ribotypes, while MEE analysis divided the same isolates into 78 electrophoretic types (ETs) . On the basis of their ribotype profiles, the strains were divided into two subgroups . The ribotype alpha (RT alpha) subgroup contained serotypes 1/2a, 1/2c, and 3a, and the ribotype beta (RT beta) subgroup contained serotypes 1/2b, 3b, 4b, and 4ab . This division is in complete agreement with MEE analysis, which divides the species into two subgroups (ET groups A and B), with the same serotype distribution in each subgroup . Overall, MEE was more discriminating than ribotyping . However, in several instances ribotyping discriminated between isolates within the same ET . Ribotyping was more discriminating for serotypes 1/2a, 1/2c, and 3a (Simpson's Index for Diversity {DI} = 0.81) than for serotypes 1/2b and 4b (DI = 0.76) . A substantial proportion (69%) of serotype 1/2b and 4b strains clustered in five ETs and five ribotypes . These data suggest that ribotyping and MEE do not provide adequate discrimination between strains of serotypes 1/2b and 4b . Methods such as pulsed-field gel electrophoresis and random amplified polymorphic DNA analysis should be explored for further discrimination of strains of these serotypes. J Clin Microbiol, 1994 Dec, 32(12), 2929 - 35 Interactions with lectins and agglutination profiles of clinical, food, and environmental isolates of Listeria; Facinelli B et al.; On the basis of preliminary trials with 14 collection strains of Listeria, five lectins (Canavalia ensiformis, concanavalin A; Griffonia simplicifolia lectin I; Helix pomatia agglutinin; Ricinus communis agglutinin; and Triticum vulgaris wheat germ agglutinin) were selected to set up a microtiter agglutination assay . The lectin agglutination profiles of 174 clinical, food, and environmental strains of Listeria monocytogenes, Listeria innocua, and Listeria seeligeri were investigated . Data on the standard determination of the antigenic structure were available for clinical strains; nonclinical isolates were assigned to serogroup 1 or 4 with commercial antisera . The listeria-lectin interaction was related to serological type rather than species; in particular, the strains assigned to serogroup 1 or belonging to serovars 1/2a, 1/2b, 1/2c, 3a, 3b, and 7 were never agglutinated by G . simplicifolia lectin I . The five-lectin set proved to be capable of detecting differences between serologically identical isolates of L . monocytogenes . Of the 150 isolates of this species, 144 were distributed over 15 different lectin agglutination profiles and 6 autoagglutinated, the overall typeability being 96% . However, the profiles encountered among L . monocytogenes isolates were not randomly distributed . With strains assigned to serogroup 1 or belonging to serovars 1/2a, 1/2b, 1/2c, and 3b, the clinical isolates fell into only two of the eight patterns recorded overall; with strains of serogroup 4 and serovar 4b, food and environmental isolates were distributed over eight of the nine patterns found in total, while clinical isolates were distributed over five patterns . In a comparative study of 15 epidemiologically relevant isolates of L . monocytogenes from five distinct outbreaks, strains with identical phage types and/or DNA fingerprints displayed identical lectin profiles . The heterogeneity of agglutination profiles may form the basis of a new approach to L . monocytogenes typing. Immunology, 1994 Dec, 83(4), 524 - 31 Evidence that gamma delta T cells play a limited role in resistance to murine listeriosis; Rakhmilevich AL; A role for alpha beta and gamma delta T cells in protection against primary and secondary infection with Listeria monocytogenes was studied . The results show that mice depleted of either gamma delta T cells with 3A10 monoclonal antibody (mAb), or alpha beta T cells with anti-CD4 plus anti-CD8 mAb, or both types of T cells, remained capable of controlling Listeria multiplication during the first 4 days of primary sublethal infection . Moreover, mice depleted of either or both types of T cells also remained capable of resolving primary infection, although the absence of alpha beta T cells, but not gamma delta T cells, caused resolution to be slower . Likewise, Listeria-immune mice depleted of either alpha beta or gamma delta T cells remained capable of resolving secondary infection with a large inoculum of L . monocytogenes, although depletion of alpha beta T cells, and to a much lesser extent gamma delta T cells, resulted in early exacerbation of infection . However, immune mice depleted of both types of T cells lost their ability to resist a lethal Listeria challenge . Taken together, the results show that whereas neither type of T cell is needed for resistance to sublethal primary listeriosis, alpha beta T cells may act in concert with gamma delta T cells in protecting mice against lethal secondary infection . In addition, the results indicate that the role of gamma delta T cells in anti-Listeria resistance is much less important than the role of alpha beta T cells, and can be demonstrated mainly in the absence of alpha beta T cells. Bioessays, 1994 Dec, 16(12), 885 - 91 Dynamic remodeling of the actin cytoskeleton: lessons learned from Listeria locomotion; Southwick FS et al.; The bacterial pathogen Listeria monocytogenes displays the remarkable ability to reorganize the actin cytoskeleton within host cells as a means for promoting cell-to-cell transfer of the pathogen, in a manner that evades humoral immunity . In a series of events commencing with the biosynthesis of the bacterial surface protein ActA, host cell actin and many actin-associated proteins self-assemble to form rocket-tail structures that continually grow at sites proximal to the bacterium and depolymerize distally . Widespread interest in the underlying molecular mechanism of Listeria locomotion stems from the likelihood that the dynamic remodeling of the host cell actin cytoskeleton at the cell's leading edge involves mechanistically analogous interactions . Recent advances in our understanding of these fundamental cytoskeletal rearrangements have been achieved through a clearer recognition of the central role of oligo-proline sequence repeats present in ActA, and these findings provide a basis for inferring the role of analogous host cell proteins in the force-producing and position-securing steps in pseudopod and lamellipod formation at the peripheral membrane. J Appl Bacteriol, 1994 Dec, 77(6), 702 - 8 Effect of heating rate on the thermal inactivation of Listeria monocytogenes; Stephens PJ et al.; In order to quantify the effect of heating rate on the thermal inactivation of Listeria monocytogenes an accurate means of describing the inactivation kinetics at near instantaneous heating was used . Survivor curves for L . monocytogenes, at near instantaneous heating, were obtained over the temperature range 50-64 degrees C . The use of a linear function to describe the data would have given only a poor approximation of the true inactivation kinetics . With a model based on a logistic algorithm extremely accurate descriptions were made . In processes which had rates of heating < or = 5.0 degrees C min-1, significant deviations of real kill from predicted kill were observed . Predicted kill assumed that heating rate did not affect the inactivation kinetics of a thermal process . At rates of heating between 5.0 and 0.7 degrees C min-1 the deviation greatly increased as the rate of heating decreased; approximately a 1.7 x 10(5)-fold difference at 0.7 degrees C min-1 . Maximum thermotolerance was induced at rates of heating < or = 0.7 degrees C min-1 . The increased thermotolerance during slow rates of heating was analogous to the induction of the heat-shock response . The models described in this work allow for confident assessments of safety to be made not only at near instantaneous heating but also when the heating rate varies. Appl Environ Microbiol, 1994 Dec, 60(12), 4600 - 4 Incidence of Listeria spp . and Listeria monocytogenes in a poultry processing environment and in poultry products and their rapid confirmation by multiplex PCR; Lawrence LM et al.; The incidence of Listeria spp . and Listeria monocytogenes in a poultry processing plant and in raw and cooked poultry products was determined over a 6-month period . Within the raw and cooked poultry processing environments, 46% (36 of 79) and 29% (51 of 173) of the samples contained Listeria spp . while 26% (21 of 79) and 15% (27 of 173) contained L . monocytogenes, respectively . Various sites within the processing environment were found to be consistently positive for L . monocytogenes throughout the entire sampling period . Of the raw and cooked products tested, 91% (53 of 58) and 8% (8 of 96) were found to contain Listeria spp . while 59% (34 of 58) and 0% (0 of 96) contained L . monocytogenes, respectively . Although L . monocytogenes was not detected in the cooked products examined, the presence of other Listeria spp . highlights the potential which exists for postprocessing contamination . Multiplex PCR proved to be a convenient and time-saving technique for rapid confirmation of Listeria spp . and L . monocytogenes in a single reaction. Eur J Immunol, 1994 Dec, 24(12), 3068 - 72 CD8+ T cell-mediated protection against an intracellular bacterium by perforin-dependent cytotoxicity; Kagi D et al.; Growth of Listeria monocytogenes is mainly controlled by macrophages, which are activated by specific T cells . A potential role of CD8+ T cells by direct lysis of infected cells was investigated in perforin-deficient mice generated by homologous recombination . The absence of perforin-mediated cytotoxicity resulted in delayed clearance of Listeria from the spleen but not the liver after primary infection, overall susceptibility to Listeria however was not increased . Protection against a secondary infection was drastically impaired in perforin-deficient mice . Adoptive transfer of immune spleen cells to recipients revealed that anti-Listeria protection by CD8+ T cells from perforin-deficient versus normal mice was about 10-fold reduced in livers and about 100-fold reduced in the spleen of recipients . CD4+ T cells from immune control and perforin-deficient mice conferred comparable protection . These results indicate that the protective effect of CD8+ T cells against an intracellular bacterium mainly evident in secondary infection is mediated by a perforin-dependent pathway, presumably cytotoxicity, and less by other direct or indirect effector mechanisms. Behring Inst Mitt, 1994 Dec, (95), 35 - 41 Soluble IL-4 receptor, potential for therapeutic and prophylactic intervention; Gessner A et al.; Many bacterial, protozoal and viral infections trigger a cell-mediated immune response . Of special importance for the clinical outcome of disease, however, is the relative predominance of T helper (Th) cell populations (Th1 and Th2) secreting different patterns of lymphokines . Preferential development of one Th subset occurs apparent at the early stages of an infection, suggesting that the mechanisms driving the immune response in one direction or the other operate soon after exposure to the antigen . Cytokines are among the most important factors regulating T cell differentiation and expansion of the different T cell subtypes . As in experimental candidiasis, listeriosis, yersiniosis and murine retrovirus induced immunodeficiency syndrome (MAIDS), interleukin-4 (IL-4) is of central importance also for the clinical course of murine cutaneous leishmaniasis . It has been demonstrated that the presence of IL-4 is essential for the development of disease promoting Th2 cells whereas neutralization of IL-4 in vivo led to establishment of protective immunity against leishmania . A naturally occurring antagonist of IL-4 is the soluble IL-4 receptor (sIL-4R), which retains its ligand binding properties and binds IL-4 with high affinity . We therefore examined the immunomodulatory and therapeutic capacity of recombinant sIL-4R in murine cutaneous leishmaniasis . BALB/c mice were treated with recombinant sIL-4+ during the onset of the immune response . This treatment rendered BALB/c mice clinically resistant to Leishmania major (L . major), led to reduced parasite load, shifted the pattern of cytokines towards Th1 type and provided durable resistance against reinfection with L . major.(ABSTRACT TRUNCATED AT 250 WORDS) Int J Food Microbiol, 1994 Dec, 24(1-2), 283 - 93 Growth suppression of Listeria monocytogenes in a meat product; Qvist S et al.; Bologna-type sausages were manufactured using standard industry processes and four different formulations: (a) standard commercial formulation (control), (b) with 2% sodium lactate, (c) with 2% lactate and 0.25% glucono-delta-lactone (GDL), (d) with 2% lactate and 0.5% GDL . The sliced sausages were inoculated with a mixture of L . monocytogenes serotype 1 and 4 (approximately 100 cfu/g) . The samples were vacuum-packaged and stored at 5 degrees C and 10 degrees C for 35 days . Rapid growth of L . monocytogenes was observed in control samples stored at 5 degrees C and in control samples and lactate treated samples (without GDL) stored at 10 degrees C . In sausages containing GDL (both levels) growth did not occur within 35 days at either 5 degrees C or 10 degrees C . Thus the presence of GDL at low level seemed sufficient to prevent growth of L . monocytogenes, although pH in the product was as high as 6.3 . In samples with 2% lactate and without GDL, growth was suppressed for 28 days at 5 degrees C . Results indicate that it is possible to suppress growth of L . monocytogenes in chilled cooked meat products by using suitable amounts of sodium lactate combined with lowering of pH . However, when using GDL as a pH lowering agent, off-flavours may be registered by some individuals at high levels of GDL. Int J Food Microbiol, 1994 Dec, 24(1-2), 113 - 23 Modelling growth rates of Listeria innocua as a function of lactate concentration; Houtsma PC et al.; The effect of sodium lactate (NaL) concentration on growth of Listeria innocua in a yeast-extract/peptone broth at pH 5.5, 6.0, 6.5 and 7.0 at 4, 10, 20 and 30 degrees C was modelled with the modified Gompertz model . NaCl was used as a reference to distinguish between the water activity effect and the specific inhibitory effect of NaL . Minimum inhibitory concentrations (MIC) of NaCl appeared to be significantly higher than MIC values of NaL, indicating that NaL had a specific inhibitory effect on growth of L . innocua . The MIC values of NaL and NaCl were not much influenced by the temperature . The pH of the growth medium was shown to have influence on the MIC values of NaL but not on the MIC values of NaCl . Total growth inhibition of L . innocua at low pH (5.5) took place at lower NaL concentrations (217 mM) than at neutral pH (1071-1339 mM), indicating that the undissociated lactic acid plays a role in the mechanism of inhibition . However, MIC values for undissociated acid increased with decreasing pH from 0.8 mM at pH 7 to 5 mM at pH 5.5 . It is therefore likely that besides acidification of the cytoplasm due to diffusion of undissociated acid into the cell, other mechanisms are involved . Growth rates at NaL concentrations between 0 and the MIC value decreased progressively with increasing concentrations down to 0 at the MIC value, and were strongly influenced by both temperature and pH . Growth rates in the presence of NaCl were influenced by the temperature only . It was shown that a modified Monod equation with three parameters was effective for description of growth rates of L . innocua at NaL and NaCl concentrations over the whole experimental range. J Immunol, 1994 Dec 1, 153(11), 5141 - 7 TNF-alpha and IFN-gamma stimulate a macrophage precursor cell line to kill Listeria monocytogenes in a nitric oxide-independent manner; Leenen PJ et al.; Macrophages are important effector cells for resolving infection with the facultative intracellular bacterium Listeria monocytogenes . However, not all macrophages have the ability to kill this organism . Certain factors, such as cytokines, are apparently required for induction of macrophage bactericidal activity . In vivo studies have shown that both TNF-alpha and IFN-gamma play important roles in resistance against Listeria . Yet whether they act directly on macrophages has been difficult to determine, because homogeneous populations of cells that can be induced to express microbicidal activity have not been available . Instead, bactericidal macrophages are typically found in heterogeneous exudates, such as those elicited by inflammatory agents . In this study we show that sequential stimulation with TNF-alpha and IFN-gamma induces the nonphagocytic, nonbactericidal mouse macrophage precursor hybrid cell line W1C3 to phagocytose and kill Listeria efficiently . This provides the first direct evidence that TNF-alpha and IFN-gamma are both necessary and sufficient to induce macrophages to kill Listeria, and that they act directly on macrophages . Data presented here also show that TNF-alpha and IFN-gamma induced the macrophages to produce large amounts of reactive nitrogen intermediates (RNI), but complete inhibition of RNI generation did not decrease bactericidal activity . This indicates that induction of listericidal activity in these cells does not require generation of RNI . Taken together, these findings suggest that TNF-alpha and IFN-gamma act in synergy directly on at least some macrophages to induce them to express listericidal activity in a RNI-independent manner. Appl Environ Microbiol, 1994 Nov, 60(11), 4186 - 8 Correlation of bioenergetic parameters with cell death in Listeria monocytogenes cells exposed to nisin; Winkowski K et al.; In Listeria monocytogenes, nisin induced ATP efflux, reduced the intracellular ATP concentration within 1 min, and dissipated the proton motive force within 2 min . Efflux accounted for only 20% of the ATP depletion, suggesting that ATP hydrolysis also occurred . ATP efflux depended on nisin concentration and followed saturation kinetics . These results suggest that nisin breaches the membrane permeability barrier in a manner more consistent with pore formation than with a nonspecific detergent-like membrane destabilization. Appl Environ Microbiol, 1994 Nov, 60(11), 4001 - 8 A novel strictly anaerobic recovery and enrichment system incorporating lithium for detection of heat-injured Listeria monocytogenes in pasteurized milk containing background microflora; Mendonca AF et al.; Heat-injured cells of Listeria monocytogenes were recovered from heated raw milk containing noninjured Enterococcus faecium by combining a simple method for obtaining strict anaerobiosis with a novel enrichment broth, Penn State University broth (PSU broth) . Strictly anaerobic conditions were rapidly achieved by adding 0.5 g of filter-sterilized cysteine per liter to PSU broth and then purging the preparation with N2 gas . Little resuscitation or growth occurred in strictly anaerobic PSU broth without lithium chloride because of overgrowth by E . faecium . The growth of E . faecium decreased dramatically with increasing LiCl concentration; LiCl concentrations of 8 and 10 g/liter were completely bacteriostatic . The mechanism of inhibition by LiCl appeared to involve competition with the divalent cations Ca2+ and Mg2+ . Heat-injured L . monocytogenes consistently recovered and grew rapidly in strictly anaerobic PSU broth containing 4, 6, or 7 g of LiCl per liter . The use of strictly anaerobic PSU broth containing 7 g of LiCl per liter permitted detection of severely heat-injured L . monocytogenes in one simple recovery-enrichment step by eliminating oxygen toxicity and inhibiting the growth of background microflora, without preventing the resuscitation and subsequent growth of heat-injured L . monocytogenes . L . monocytogenes heated in raw milk at 62.8 degrees C for 10, 15, and 20 min could be consistently recovered from strictly anaerobic PSU broth enrichment cultures at 30 degrees C after 48, 96, and 144 h, respectively, and hence, use of PSU broth may result in better recovery of both injured and noninjured cells from foods than currently used U.S . Department of Agriculture and Food and Drug Administration preenrichment procedures. Infect Immun, 1994 Nov, 62(11), 5161 - 3 Administration of antigranulocyte monoclonal antibody RB6-8C5 prevents expression of acquired resistance to Listeria monocytogenes infection in previously immunized mice; Czuprynski CJ et al.; Recent studies have established the importance of neutrophils in innate resistance to Listeria monocytogenes infection in mice . The purpose of this study was to determine the importance of neutrophils in acquired resistance to L . monocytogenes infection . Previously immunized mice that were depleted of neutrophils by administration of the antigranulocyte monoclonal antibody RB6-8C5 demonstrated less resistance to L . monocytogenes challenge than did nonimmunized control mice . In contrast, immunized control mice exhibited a heightened resistance to rechallenge, as expected . These results suggest that neutrophils make previously unrecognized contributions to acquired immunity to a facultative intracellular pathogen. Infect Immun, 1994 Nov, 62(11), 5102 - 11 Mammalian cells transfected with the listeriolysin gene exhibit enhanced proliferation and focus formation; Demuth A et al.; Mouse 3T6 and 3T3 fibroblasts and rat epithelial L2 cells were transfected with recombinant plasmids containing the listeriolysin gene (hly) of Listeria monocytogenes . This bacterial gene (with and without the 5' signal sequence) was cloned under the control of a murine metallothionein promoter, resulting in elevated transcription of both forms of the hly gene after induction with ZnSO4 . However, the gene product could be observed only when the listeriolysin gene lacking the 5' signal sequence was used . Intact listeriolysin could not be detected in the cytoplasm or in the supernatant of the hly-transfected cells . 3T6 and L2 cells transfected with the intact hly gene exhibited significantly increased cell proliferation and increased formation of actin microfilaments upon induction of hly expression with ZnSO4 . Both cell types are not contact inhibited and formed large piles of spherical cells after transfection with hly . In contrast, contact-inhibited 3T3 cells transfected with the hly gene showed increased proliferation but no formation of such cell aggregates . When 3T6 fibroblasts were transfected with the hly gene without the 5' signal sequence, inhibition of growth, lack of cell layer confluency, and altered (spherical) cell morphology were observed. Infect Immun, 1994 Nov, 62(11), 4990 - 6 Vaccination with Brucella abortus rough mutant RB51 protects BALB/c mice against virulent strains of Brucella abortus, Brucella melitensis, and Brucella ovis; Jimenez de Bagues MP et al.; Vaccination of BALB/c mice with live Brucella abortus RB51, a stable rough mutant, produced protection against challenge with virulent strains of Brucella abortus, Brucella melitensis, and Brucella ovis . Passive-transfer experiments indicated that vaccinated mice were protected against B . abortus 2308 through cell-mediated immunity, against B . ovis PA through humoral immunity, and against B . melitensis 16M through both forms of immunity . Live bacteria were required for the induction of protective cell-mediated immunity; vaccination with whole killed cells of strain RB51 failed to protect mice against B . abortus 2308 despite development of good delayed-type hypersensitivity reactions . Protective antibodies against the heterologous species were generated in vaccinated mice primarily through anamnestic responses following challenge infections . Growth of the antigenically unrelated bacterium Listeria monocytogenes in the spleens of vaccinated mice indicated that nonspecific killing by residual activated macrophages contributed minimally to protection . These results encourage the continued investigation of strain RB51 as an alternative vaccine against heterologous Brucella species . However, its usefulness against B . ovis would be limited if, as suggested here, epitopes critical for protective cell-mediated immunity are not shared between B . abortus and B . ovis. Bone Marrow Transplant, 1994 Nov, 14(5), 799 - 803 Unusual infections following allogeneic bone marrow transplantation for chronic lymphocytic leukemia; Zomas A et al.; Unusually severe infections phenomena were observed in three patients with chronic lymphocytic leukemia (CLL) who had undergone allogeneic bone marrow transplantation (BMT) from matched sibling donors . The first developed three episodes of cytomegaloviremia requiring anti-viral therapy; the third episode accompanied by cytomegalovirus hepatitis which required prolonged therapy with foscarnet . Another had Listeria monocytogenes meningitis which was difficult to eradicate and required prolonged maintenance antimicrobial therapy with oral trimethoprim-sulfamethoxazole and intrathecal gentamicin until death due to chronic graft-versus-host disease . The third patient had cytomegaloviremia lasting 47 days, which did not clear within 4 weeks of full-dose ganciclovir . Although the number of patients is small, in our experience the problems encountered were unusually severe compared with patients allografted for other disease . We conclude that CLL patients undergoing allogeneic BMT may be at a higher risk of infectious complications than patients allografted for other diseases, and require careful monitoring. FEMS Immunol Med Microbiol, 1994 Nov, 10(1), 1 - 9 Naturally occurring virulence-attenuated isolates of Listeria monocytogenes capable of inducing long term protection against infection by virulent strains of homologous and heterologous serotypes; Chakraborty T et al.; Experimental infections of mice with strains of Listeria spp . isolated from contaminated food sources allowed discrimination of strains into those either exhibiting high, attenuated or low virulence . Compared to the highly virulent L . monocytogenes strain EGD, an attenuated strain such as L99 persisted for shorter times (5 versus 10 days) in the infected host . Using a tissue culture cell model of infection, we found that, although strain L99 was capable of accumulating actin like its virulent counterpart following invasion, it was unable to generate the polarized actin tails required for intracellular and cell-to-cell movement . Immunoblot analysis using specific antiserum to the ActA polypeptide, a molecule that is necessary for movement of the bacterium within the eucaryotic cell, indicated that a slightly truncated form of this polypeptide was produced in the L99 strain . Despite its reduced virulence, the attenuated strain L99 was just as effective in generating protection in immune mice as the highly virulent strains, albeit with a 1000-fold higher infective dose . Based on the results obtained from this study, we suggest that one of the mechanisms accounting for widespread resistance in humans to infection by Listeria may be due to asymptomatic infections by naturally occurring strains attenuated for virulence. Int J Food Microbiol, 1994 Nov, 23(3-4), 377 - 90 Growth of Listeria monocytogenes on vacuum-packed cooked meats: effects of pH, aw, nitrite and ascorbate; Duffy LL et al.; Slices of cooked meats were inoculated with Listeria monocytogenes strain Murray B, vacuum-packed and stored at either 0 or 5 degrees C . Decreases in pH (6.9-5.9) and aw (0.993-0.960; adjusted with sodium chloride) of the cooked meats increased the lag time and reduced the growth rate at 5 degrees C . The type of meat (beef, pork, chicken or turkey) had no effect on the growth of the organism after allowance was made for pH . Sodium tripolyphosphate (0.3%) increased growth by increasing the pH of the cooked meat . Sodium nitrite reduced the growth rate and increased the lag time . Three microM of residual undissociated nitrite doubled the time taken for a 3 log increase in numbers of L . monocytogenes . The effectiveness of nitrite was significantly increased by sodium ascorbate (0.042%) . In the absence of nitrite, ascorbate had no detectable effect on growth . The extent of growth at 0 degree C was similarly influenced by the interaction of pH, aw, nitrite and ascorbate, and was considerably less than at 5 degrees C . Quadratic equations were developed to describe some of the combined effects of pH, aw and residual nitrite on lag, growth rate and time for a 3 log increase in numbers of L . monocytogenes. Int Immunol, 1994 Nov, 6(11), 1727 - 37 CD4+ T cell associated cytokine gene expression during experimental infection with Listeria monocytogenes: the mRNA phenotype of granuloma formation; Ehlers S et al.; In murine listeriosis, elimination of bacteria and immunity to re-infection critically depend on Thy-1+CD4- cells, while cell-mediated inflammatory phenomena like delayed-type hypersensitivity and granuloma formation are mediated by CD4+ T cells . In an attempt to correlate T cell phenotype and function with a particular set of cytokines produced in vivo, we examined the cytokine gene expression profile associated with the presence or absence of CD4+ and/or CD8+ cells in the livers of mice during experimental infection with Listeria monocytogenes . T cell subset depletion was achieved by i.p . administration of saturating amounts of the appropriate mAbs, and mRNA detection was carried out using a qualitative and semi-quantitative polymerase chain reaction-based mRNA amplification protocol . In both primary and secondary infection, the presence of CD4+ cells was a prerequisite for granuloma formation, and was found to be closely associated with mRNA expression for IL-2, IL-3 and IL-4, a 5-fold increase in expression of tumor necrosis factor (TNF)-alpha and granulocyte macrophage colony stimulating factor, and a 25-fold increase in expression of IFN-gamma and TNF-beta mRNAs, suggesting a role for these cytokines in granuloma formation . In striking contrast, depletion of CD8+ cells did not result in reduced mRNA expression for any one of the cytokines studied, implying that CD8+ T cell mediated cure and prevention of listeriosis may operate via qualitatively distinct mechanisms. J Clin Periodontol, 1994 Nov, 21(10), 680 - 3 Antioxidative activities of some chemotherapeutics . A possible mechanism in reducing gingival inflammation; Firatli E et al.; Inflammatory periodontal diseases are related to dental plaque formation . Increase in the perfusion of the inflamed tissue results in increased oxygen supply . Although oxygen has healing effects, it is bound to be a mediator of peroxidation in biological membranes . Chemotherapeutic agents such as chlorhexidine, listerine, sanguinarine, and cetylpridinium chloride and oral antibiotics such as tetracycline HCl and doxycyline were tested for their antioxidative activities . While doxycycline has the highest antioxidant activity in lower volumes (0.1 ml), sanguinarine, listerine and a pace after them, tetracycline HCl, had similar effects in higher volumes (0.3 and 0.4 ml) . The results showed that in addition to their antiseptic or antimicrobial effects, these preparations have an antioxidative activity against spontaneous oxidation. J AOAC Int, 1994 Nov-Dec, 77(6), 1472 - 89 Enzyme-linked immunoassay for detection of Listeria monocytogenes in dairy products, seafoods, and meats: collaborative study; Curiale MS et al.; A collaborative study was conducted to evaluate Listeria-Tek, an enzyme-linked immunosorbent assay (ELISA) for detection of Listeria monocytogenes and other Listeria spp . in foods . The present ELISA method was compared to the U.S . Food and Drug Administration culture method for detection of L . monocytogenes in dairy products and seafoods and to the U.S . Department of Agriculture Food Safety and Inspection Service method for detection of L . monocytogenes in meats . Replicate samples of 6 food types (frankfurters, roast beef, Brie cheese, 2% milk, raw shrimp, and crab meat) inoculated with L . monocytogenes and uninoculated control samples were analyzed by the collaborators . L . monocytogenes was identified in 593 samples by the ELISA method and in 574 samples using culture procedures . Identical results were obtained for 506 positive samples and 419 negative samples using the ELISA and culture methods for an overall agreement rate of 85.6% . The enzyme-linked immunoassay for detection of L . monocytogenes in dairy, seafood, and meat products has been adopted first action by AOAC INTERNATIONAL. Res Microbiol, 1994 Nov-Dec, 145(9), 677 - 82 Listeria monocytogenes infection of Caco-2 cells: role of growth temperature; Conte MP et al.; The aim of the present study was to evaluate the role of temperature in the virulence of Listeria monocytogenes, a Gram-positive facultative intracellular food-borne pathogen . The capacity of bacteria grown at 37, 25 and 4 degrees C to develop haemolytic activity, to enter the Caco-2 enterocyte-like cell line and to multiply intracellularly was investigated . We demonstrated that L . monocytogenes penetration was not significantly influenced by the growth temperature of cultures and that bacteria grown at low temperature were capable of synthesizing internalin and, during the infection process, of restoring the haemolytic phenotype which is normally lacking in the extracellular environment at 4 and 25 degrees C . It can be concluded that L . monocytogenes, frequently present in numerous environmental sources and also in refrigerated food products, produces at low temperature, the virulence factors necessary to invade intestinal cells. In Vivo, 1994 Nov-Dec, 8(5), 879 - 84 Ethylene dibromide: evidence of systemic and immunologic toxicity without impairment of in vivo host defenses; Ratajczak HV et al.; Ethylene dibromide was administered intragastrically on 14 consecutive days to B6C3F1 female mice . Host resistance was not altered after challenge with B16F10 tumor cells, Listeria monocytogenes, influenza, or Herpes simplex viruses . In contrast, decreases were seen in relative thymus and spleen weights, red blood cells, hemoglobin, hematocrit, and in alveolar macrophage, natural killer cell, T-cell, and mixed lymphocyte culture responses . Increases occurred in relative kidney and liver weights, cholesterol, peripheral neutrophils, resident peritoneal exudate cells (with increased phagocytosis) and plaque-forming cells . There was little difference between the dose that caused immune modulation and that which produced significant toxicity. Vet Microbiol, 1994 Nov, 42(2-3), 245 - 53 Listeria innocua isolated from a case of ovine meningoencephalitis; Walker JK et al.; This paper reports a naturally occurring case of meningoencephalitis associated with Listeria innocua in a Polled-Dorset ewe . The ewe was one of a housed group of twenty-five, fed ad lib . on wrapped baled silage . L . innocua was isolated after one week from cold enrichment culture of brain and pituitary tissue . Its identity was confirmed by conventional biochemical tests, API Listeria (BioMerieux UK Ltd), the absence of hly and prfA genes using PCR assay and sequencing two variable regions of 16S rDNA . Histological examination demonstrated lesions of vasculitis and perivascular cuffing in the midbrain which were consistent with listeriosis although limited in distribution and severity. Int Immunol, 1994 Nov, 6(11), 1751 - 7 NADPH diaphorase staining suggests a transient and localized contribution of nitric oxide to host defence against an intracellular pathogen in situ; Flesch IE et al.; Nitric oxide (NO) is formed constitutively in neurons by the constitutive enzyme NO synthase (cNOS) and acts as a neurotransmitter . It has already been shown that cNOS-containing neurons are identical to neurons staining for NADPH diaphorase and vice versa . Effector cells of the immune response produce high NO levels after appropriate stimulation and this NO is formed by inducible NO synthase (iNOS) . The NO produced by macrophages is considered an important effector molecule of antimicrobial host defence . We have applied NADPH diaphorase staining for the detection of NO producing cells in situ during infection with an intracellular pathogen . Macrophages which produce NO in vitro are stained for NADPH diaphorase . Expression of iNOS mRNA and macrophage NADPH diaphorase staining was inhibited by iNOS-specific antisense oligonucleotides . These data suggest coincidental similarity between NADPH diaphorase activity and NO production by macrophages . Cells staining for NADPH diaphorase were identified in cryostat frozen sections of livers from mice infected with the intracellular pathogen, Listeria monocytogenes, and co-localized with cells labelled by MAC-1 mAbs . The purple-blue reaction product of NADPH diaphorase staining was visible in discrete granulomatous lesions but was absent from the liver parenchyma . Our results provide direct evidence for localized and transient participation of NO in antimicrobial immunity in the infected organ . This restriction may focus NO production to lesions, leaving unrelated tissue sites unaffected. FEMS Microbiol Lett, 1994 Oct 15, 123(1-2), 119 - 23 The 126 kDa iron-regulated protein of Listeria monocytogenes is not a transferrin binding protein; Bhatt R et al.; It has been reported that a 126 kDa protein of Listeria monocytogenes binds human transferrin . It is evident from results presented here that this is not so and that the observation of others resulted from interaction of this 126 kDa protein with streptavidin. Rev Prat, 1994 Oct 15, 44(16), 2177 - 81 {Meningo-encephalitis with clear cerebrospinal fluid in adults}; Stahl JP et al.; Meningitis with a clean cerebrospinal fluid are most often benign and related to a wide variety of viruses with spontaneous favourable outcome . Measles and rubella are dramatically decreasing, because of the systematic vaccination . The main problem is heptic meningoencephalitis, leading to an empiric treatment with aciclovir . The other urgent question is the possibility of Listeria infection, leading also to an empiric antibiotherapy . Tuberculosis should not be neglected, but the treatment is not so urgent . The various hypotheses are often formulated because of epidemiological data or underlying disease . The biological data are most often too late to be interesting for the initial therapeutic decision. J Immunol, 1994 Oct 1, 153(7), 3101 - 15 Immune protection and control of inflammatory tissue necrosis by gamma delta T cells; Fu YX et al.; Host defenses against experimental listeriosis in mice involve neutrophils, macrophages, NK cells, and alpha beta T cells . Recently gamma delta T cells have also been implicated in antilisterial resistance . However, their specific role has remained unclear . Here we show that efficient resistance to infection by this bacterium depends on the functions of both alpha beta and gamma delta T cells in both primary and secondary responses . We also present evidence that these functions are complementary . In the livers of alpha beta T cell-depleted mice, bacteria grow to large numbers within hepatocytes but are infrequently found extracellularly . Granulomatous lesions are more frequent and somewhat larger than in normal controls, but remain focal . Neutrophils are absent from liver lesions in these mice . In contrast, the livers of gamma delta T cell-depleted mice contain many extracellular bacteria, but do not show hepatocytes containing large numbers of Listeria . Liver lesions in gamma delta T cell-depleted mice are far more extensive than in normal controls or in alpha beta T cell-depleted mice, and contain large numbers of neutrophils . Particularly in secondary listeriosis, gamma delta T cell-depleted mice show vast coalescent areas of necrotic liver parenchyma within 48 h after infection . Because the bacterial numbers in gamma delta T cell-depleted mice remain lower than in alpha beta T cell-depleted mice, increased mortality in the former may be in part caused by liver failure . We conclude that gamma delta T cells are required to control inflammatory reactivity and to prevent excessive liver damage during the immune response to Listeria monocytogenes. J Appl Bacteriol, 1994 Oct, 77(4), 353 - 8 Comparison of the fluorescent redox dye 5-cyano-2,3-ditolyltetrazolium chloride with p-iodonitrotetrazolium violet to detect metabolic activity in heat-stressed Listeria monocytogenes cells; Bovill RA et al.; The fluorogenic redox indicator 5-cyano-2,3-ditolyltetrazolium chloride (CTC) was compared with the chromogenic p-iodonitrotetrazolium violet (INT) and conventional methods to assess cellular viability . Mild heat treatment was used as well-controlled method for producing non-viable and sub-lethally injured cells . CTC gave an underestimation of the viability of Listeria monocytogenes cells when compared with classical plating methods whereas INT gave an overestimation . However, CTC proved to be a sensitive indicator of uninjured cells . The difference between the total count and the CTC count was equivalent to the injured cell population . The fluorescent formazan formed on reduction of CTC was readily detected with a charge coupled device and cells enumerated automatically using image analysis. Appl Environ Microbiol, 1994 Oct, 60(10), 3870 - 3 Glucose uptake by Listeria monocytogenes Scott A and inhibition by pediocin JD; Christensen DP et al.; Glucose uptake by Listeria monocytogenes Scott A was inhibited by the bacteriocin pediocin JD and by the protonophore carbonyl cyanide m-chlorophenyhydrazone . Experiments with monensin, nigericin, chlorhexidine diacetate, dinitrophenol, and gramicidin, however, showed that glucose uptake could occur in the absence of a proton motive force . L . monocytogenes cell extracts phosphorylated glucose when phosphoenolpyruvate (PEP) was present in the assay mixture, and whole cells incubated with 2-deoxyglucose accumulated 2-deoxyglucose-6-phosphate, indicating the presence of a PEP-dependent phosphotransferase system in this organism . Glucose phosphorylation also occurred when ATP was present, suggesting that a proton motive force-mediated glucose transport system may also be present . We conclude that L . monocytogenes Scott A accumulates glucose by phosphotransferase and proton motive force-mediated systems, both of which are sensitive to pediocin JD. Appl Environ Microbiol, 1994 Oct, 60(10), 3854 - 61 Sensitization of heat-treated Listeria monocytogenes to added lysozyme in milk; Kihm DJ et al.; Listeria monocytogenes was highly resistant to hen egg white lysozyme in whole milk but was sensitive in media and in phosphate buffer . Methods to sensitize the pathogen to lysozyme in milk were investigated . Treatment of whole milk by cation exchange to remove minerals, particularly Ca2+ and Mg2+, slightly promoted inactivation of L . monocytogenes by lysozyme at 4 degrees C over a period of 6 days . Heat treatment (62.5 degrees C for 15 s) strongly sensitized L . monocytogenes to lysozyme in demineralized milk and in MES {2-(N-morpholino)ethanesulfonic acid} buffer . Addition of Ca2+ or Mg2+ to the demineralized milk restored resistance to lysozyme . Cells were more rapidly heat inactivated at 55 degrees C in demineralized milk containing lysozyme, and addition of Ca2+ to the demineralized milk restored the resistance to heat . The results indicate that minerals or mineral-associated components protect L . monocytogenes from inactivation by lysozyme and heat in milk, probably by increasing cell surface stability . The heat treatment of foods containing added lysozyme can probably play a significant role in producing microbiologically safe foods. Appl Environ Microbiol, 1994 Oct, 60(10), 3560 - 5 Influence of preadsorbed milk proteins on adhesion of Listeria monocytogenes to hydrophobic and hydrophilic silica surfaces; al-Makhlafi H et al.; The adsorption of beta-lactoglobulin, bovine serum albumin, alpha-lactalbumin, and beta-casein for 8 h and beta-lactoglobulin and bovine serum albumin for 1 h at silanized silica surfaces of low and high hydrophobicity, followed by incubation in buffer and contact with Listeria monocytogenes, resulted in different numbers of cells adhered per unit of surface area . Adhesion to both surfaces was greatest when beta-lactoglobulin was present and was lowest when bovine serum albumin was present . Preadsorption of alpha-lactalbumin and beta-casein showed an intermediate effect on cell adhesion . Adsorption of beta-lactoglobulin for 1 h resulted in a generally lower number of cells adhered compared with the 8-h adsorption time, while the opposite result was observed with respect to bovine serum albumin . The adhesion data were explainable in terms of the relative rates of arrival to the surface and postadsorptive conformational change among the proteins, in addition to the extent of surface coverage in each case. Appl Environ Microbiol, 1994 Oct, 60(10), 3548 - 52 Monoclonal antibodies with a high degree of specificity for Listeria monocytogenes serotype 4b; Kathariou S et al.; Strains of Listeria monocytogenes serotype 4b account for a large fraction of sporadic listeriosis cases, as well as all major food-borne epidemics attributed to this pathogen . We have identified a set of three monoclonal antibodies which showed a high degree of specificity for strains of L . monocytogenes serotype 4b . Two of these antibodies (c74.33 and c74.180, isotypes immunoglobulin M {IgM} and IgG3, respectively) recognized all serotype 4b strains, whereas antibody c74.22 (isotype IgG1) failed to recognize certain epidemic-associated strains . The corresponding antigens were located on the surface of the bacteria and were expressed following bacterial growth in different media and over a wide range of temperatures (4, 22, and 37 degrees C) . Heating L . monocytogenes cells at 80,90, or 100 degrees C abolished reactivity for c74.22 but not for c74.33 MAb . These MAbs were negative for all of the non-Listeria strains tested, including representatives of several gram-negative and gram-positive species . The surface antigen recognized by c74.22 appeared to be associated with the ability of the bacteria to enter (invade) mammalian cells in culture. J Cell Sci, 1994 Oct, 107 ( Pt 10), 2951 - 60 Exploitation of microfilament proteins by Listeria monocytogenes: microvillus-like composition of the comet tails and vectorial spreading in polarized epithelial sheets; Temm-Grove CJ et al.; Effective cell-to-cell spreading of the facultative intracellular pathogen Listeria monocytogenes requires the interaction between bacteria and the microfilament system of the host cell . By recruiting actin filaments into a 'comet tail' localized at one pole of the bacterial cell wall, Listeria become mobile and propel themselves through the cytoplasm . They create protrusions at the plasma membrane that can invaginate adjacent cells . In this work, we have analysed the structural composition of Listeria-recruited microfilaments in various epithelial cell lines by immunofluorescence microscopy . The microfilament-crosslinking proteins alpha-actinin, fimbrin and villin were localized around bacteria as soon as actin filaments could be detected on the bacterial surface . Surprisingly, the same was found for ezrin/radixin, proteins involved in linking microfilaments to the plasma membrane . We found that in a polarized cell line derived from brush border kidney epithelium (LLC-PK1), the actin filaments surrounding intracytoplasmic motile bacteria show the same immunoreactivity as the brush border-like microvilli, when analysed by a specific actin antibody . The successful invasion of polarized LLC-PK1 islets is vectorial, i.e . it progresses predominantly from the periphery of the islets towards the centre . Infection of the peripheral cells is sufficient for infiltration of the entire cellular islets, without any further contact with the extracellular milieu . This is in contrast to nonpolarized epithelial sheets, which can be invaded from the apical surface of any individual cell . The importance of active bacterial motility in this vectorial spreading is emphasized by our finding that an isogenic Listeria mutant that is unable to recruit actin filaments cannot colonize polarized epithelial layers but accumulates in the peripheral cells of the islets. Int J Food Microbiol, 1994 Oct, 23(2), 227 - 30 Influence of the inoculum concentration on the recovery of Listeria from meat by L-Palcamy enrichment; Balimandawa M et al.; Concentration of the inoculum in L-Palcamy broth enrichment had a marked influence on the recovery of Listeria from meat samples . A 1/100 dilution of ground meat yielded twice as many positive samples as the usually recommended tenfold dilution, whereas no such effect was observed with cheese or vegetables. Zentralbl Hyg Umweltmed, 1994 Oct, 196(3), 237 - 44 Study of the prevalence of Listeria spp . in surface water; Bernagozzi M et al.; The quantity of Listeria species was determined in 49 samples of various types of water (river, brackish water, urban wastewater) . Twenty nine strains of Listeria were isolated . These were mainly identified as Listeria monocytogenes (72,4%), but Listeria innocua, Listeria grayi, Listeria ivanohovii and Listeria welshimeri were also present . With the exception of water taken from the estuary, 74.4% of samples contained Listeria in mean concentrations of between 2 MPN/100 ml and 1320 MPN/100 ml in fresh surface water and untreated sewage respectively. Immunology, 1994 Oct, 83(2), 302 - 7 Neutrophils as effector cells of T-cell-mediated, acquired immunity in murine listeriosis; Appelberg R et al.; The control of the infections caused by Listeria monocytogenes, considered an example of an intracellular parasite, is thought to involve co-operation between antigen-specific T cells and activated macrophages . Here we investigated the participation of polymorphonuclear leucocytes in the mechanisms of resistance during the immune phase of the antimicrobial response to L . monocytogenes infection . We found that BALB/c mice were unable to express T-cell-mediated (acquired) immunity to this pathogen in the absence of granulocytes . We propose that neutrophils should be included in the concept of cell-mediated immunity and that their antimicrobial role is not exclusively expressed during the early phases of a primary infection. Lett Appl Microbiol, 1994 Oct, 19(4), 258 - 60 The repression of listeriolysin O expression in Listeria monocytogenes by the phenolic beta-D-glucoside, arbutin; Park SF; Expression of the listeriolysin O, a key virulence factor for Listeria monocytogenes, was monitored using a hlyA-luxAB transcriptional fusion . The phenolic beta-D-glucoside, arbutin, was found to repress the expression of the listeriolysin O at the level of transcription . In contrast, the structurally similar beta-glucoside salicin did not prevent expression of listeriolysin. Rev Argent Microbiol, 1994 Oct-Dec, 26(4), 183 - 8 {Isolation of Listeria seeligery from cecum of vizcacha (Lagostomus maximus maximus)}; Laciar AL et al.; Recent food listeriosis outbreaks confirm that more faithful isolation and identification methods for Listeria monocytogenes or other potentially pathogen microorganisms are required . Furthermore, the human and animal reservoir role in the ecology of this disease must be established . Listeria spp . in the vizcacha intestinal content was determined by two isolation procedures, starting from 10 g of homogenized samples in 40 ml of PBS . I)0.1 ml was stripped on phenylethanol agar, selective agar for Listeria and acryflavin ceftazidin agar, then incubated at 37 degrees C for 48 h, suspected colonies were identified by preliminary tests (Gram, hemolysis, catalase, esculin hydrolisis and motility at 22 degrees C) and confirmatory tests (indol, methyl red, Voges Proskauer, nitrate and carbohydrate fermentation) (Table 1) . Antibiotic susceptibility, protein profile by PAGE and pathogenic power in mice were determined . II) The remaining homogenate was incubated at 4 degrees C in 100 ml of Donnelly and Baigent enrichment broth, weekly or monthly with subcultures until 30 days or 6-8 months, respectively . The subcultures were followed up as in I) . A L . seeligeri strain, susceptible to antibiotics suggested for L . monocytogenes and exhibiting resistance to some second and third generation cephalosporins, was isolated (Table 2) . The protein profile of both species was coincident, but L . seeligeri was not virulent for mice . The finding of L . seeligeri in an animal (4.0%) used as human feeding source is of interest due to its potential pathogen power. Circ Shock, 1994 Oct, 44(2), 51 - 6 Phenotypic analysis of TNFR1-deficient mice and characterization of TNFR1-deficient fibroblasts in vitro; Rothe J et al.; In order to analyse the physiological relevance of the 55 kDa tumor necrosis factor receptor 1 (TNFR1) and its role in various TNF related pathological conditions, such as septic shock, we have generated mice by gene targeting deficient for TNFR1 expression . The TNFR1-deficient mice are unable to cope with Listeria monocytogenes infections but mount an apparently normal immune response when challenged with Vaccinia or LCMV viruses . They are resistant to the lethal effects of lipopolysaccharide (LPS) after sensitization with D-galactosamine (D-GalN) but remain sensitive to very high doses of LPS given alone . We have analyzed functions relevant to inflammatory processes, such as adhesion, secondary factor release, and proliferation in fibroblasts derived from these mice . We show that the TNFR1 virtually monopolises TNF-mediated signaling in all these situations and that the 75 kDa TNFR2 seems to be largely restricted to an accessory role, which is compatible with the previously established "ligand passing" hypothesis. J Immunol, 1994 Oct 1, 153(7), 3116 - 22 Studies with MHC-deficient knock-out mice reveal impact of both MHC I- and MHC II-dependent T cell responses on Listeria monocytogenes infection; Ladel CH et al.; Mutant mice with a defined genetic defect in the beta 2-microglobulin (beta 2m) or the H2-I-A beta chain, which are virtually devoid of functional CD8 or CD4 alpha beta T cells, respectively, were employed for analyzing immune mechanisms involved in acquired resistance against Listeria monocytogenes . Although the lethal dose of L . monocytogenes was markedly lower for either mouse mutant as compared with their heterozygous control littermates, both beta m -/- and A beta -/- mutants were able to resolve low dose infection . However, in both mouse mutants, the course of disease was exacerbated and clearance was markedly delayed . Vaccine induced immunity against a secondary high dose infection lethal for naive animals was also impaired in beta 2m -/- and A beta -/- mice . However, both mutant mice were still capable of controlling secondary infection . Based on numbers of L . monocytogenes organisms in spleens, beta 2m -/- mutants suffered more dramatically from primary and secondary infection than A beta -/- mice . Ag-induced IFN-gamma secretion was impaired during the early phase of infection in beta 2m -/- mice and at later stages in A beta -/- mice . Modulation of gamma delta T cells by mAb treatment led to significant increase in bacterial load of spleens in both beta 2m -/- and A beta -/- mice . Finally, the development of granulomatous lesions was markedly affected in both mutants . In beta 2m -/- mutants, infiltrative lesions appeared and in A beta -/- mice few inflammatory islets with necrotic centers developed . These data demonstrate the importance of both MHC I- and MHC II-dependent immune mechanisms in acquired resistance to L . monocytogenes and point to the necessity of a coordinated interaction between CD8 and CD4 alpha beta T cells (and probably gamma delta T cells) in anti-L . monocytogenes resistance. Immunobiology, 1994 Oct, 191(4-5), 509 - 19 Role of T cell subsets in immunity against intracellular bacteria: experimental infections of knock-out mice with Listeria monocytogenes and Mycobacterium bovis BCG; Kaufmann SH et al.; The generation of knock-out mice with targeted gene deletions has already proven its enormous value for our understanding of the antimicrobial immune response . Here, we describe studies with knock-out mice deficient in the TCR-beta gene, lacking alpha/beta T cells; in the TCR-delta gene, lacking gamma/delta T cells; in the beta 2m gene, lacking beta 2-microglobulin, and hence cell surface expressed MHC class I and functional CD8 T cells; and in the H-2I-A beta gene, lacking cell surface expressed MHC class II and hence functional CD4 T cells . These mice were infected with Listeria monocytogenes or Mycobacterium bovis BCG as representative microbes which primarily activate CD8 T cells or CD4 T cells, respectively . Data described in this treatise demonstrate that the different gene deletions had an impact of varying degree on antibacterial defense and on the formation of granulomatous lesions . At the same time, the data point to a compensatory potential of the incomplete immune system . We assume that deletions in the major immune effector cells promote the emergence of a second line of defenders which frequently remain silent in the normal immune system . Thus, our data illustrate an enormous redundancy of the immune system, which, however, is not abundant since it takes over essential functions in the immunodeficient situation. Immunobiology, 1994 Oct, 191(4-5), 474 - 7 Adhesion molecules mediating recruitment of monocytes to inflamed tissue; Patarroyo M; Three families of cell-surface proteins are largely responsible for the adherence of leukocytes to cells and matrices: integrins, immunoglobulin (Ig)-related molecules and selectins . Blood monocytes express beta 1 integrins VLA-4, -5 and -6 and beta 2 integrins CD11a/CD18, CD11b/CD18 and CD11c/CD18 . These cells also express the Ig-related molecules ICAM-1, -2 and -3, ligands for the beta 2 integrins . In addition, monocytes express L-selectin and the oligosaccharides Lex and sialyl Lex, ligands for the endothelial selectins E- and P- . In vitro studies with blocking antibodies have identified adhesion molecules participating in the adherence of monocytes to one another, to T lymphocytes and to vascular endothelial cells . These antibodies also block adhesion-dependent monocyte activities, such as cytotoxicity of tumor cells, antigen presentation, phagocytosis of large particles, induction of cytokine secretion, formation of multinucleated giant cells and HIV-induced syncytium formation . In vivo studies in animals have demonstrated participation of L-selectin and CD11b/CD18 in monocyte accumulation in inflamed peritoneum . Moreover, treatment with anti-CD11b antibodies potentiates primary listeriosis and inhibits the macrophage recruitment and granuloma formation, and anti-CD18 antibodies block ear swelling in Mycobacterium tuberculosis-immunized animals following challenge with PPD . Adhesion molecules may also play key roles in the pathogenesis of tuberculosis and AIDS. Immunobiology, 1994 Oct, 191(4-5), 432 - 40 The mRNA-phenotype of granuloma formation: CD4+ T cell-associated cytokine gene expression during primary murine listeriosis; Ehlers S et al.; In murine listeriosis, elimination of bacteria and immunity to reinfection critically depend on Thy1+ CD4- cells, while cell-mediated inflammatory phenomena such as DTH and granuloma formation are mostly mediated by CD4+ T cells . In an attempt to correlate T cell phenotype and function with a particular set of cytokines produced, we examined the cytokine gene expression profile associated with the presence or absence of Thy1+, CD4+ and/or CD8+ cells in the livers of mice during a primary infection with L . monocytogenes . The presence of CD4+ cells was found to be closely associated with mRNA expression for IL-2, IL-3 and IL-4, a 5-fold increase in expression of TNF-alpha and GM-CSF and a 25-fold increase in expression of IFN-gamma and TNF-beta mRNAs, and temporally coincided with the development of granulomatous lesions . In vivo neutralization of TNF-alpha and, to a lesser extent, IFN-gamma resulted in abrogation of granuloma formation . A similar correlation between the presence of CD8+ cells and mRNA expression for any one of the cytokines studied did not exist, pointing to a qualitatively different mechanism of CD8+ T cell mediated cure of listeriosis. Immunobiology, 1994 Oct, 191(4-5), 424 - 31 Macrophage activation and innate resistance to infection in SCID mice; Bancroft GJ et al.; Resistance to infection against a variety of pathogens requires the co-ordinated interaction of both the innate and acquired immune responses . Mice bearing the SCID mutation are devoid of T and B cells but retain elements of the innate immune system including natural killer (NK) cells, macrophages, granulocytes and complement proteins . Using the SCID model we have identified a T cell independent mechanism of macrophage activation mediated by the secretion of IFN-gamma from NK cells . This process occurs in response to a variety of parasites and bacteria including Listeria monocytogenes, and is strictly regulated both in vitro and in vivo by cytokines such as IL-2 and IL-10 . Here we discuss the mechanisms of NK cell activation and regulation and describe a new model of opportunistic infection in SCID mice with the AIDS related pathogen Cryptosporidium parvum. Blood, 1994 Sep 15, 84(6), 1737 - 46 Mice lacking granulocyte colony-stimulating factor have chronic neutropenia, granulocyte and macrophage progenitor cell deficiency, and impaired neutrophil mobilization; Lieschke GJ et al.; Mice lacking granulocyte colony-stimulating factor (G-CSF) were generated by targeted disruption of the G-CSF gene in embryonal stem cells . G-CSF-deficient mice (genotype G-CSF-/-) are viable, fertile, and superficially healthy, but have a chronic neutropenia . Peripheral blood neutrophil levels were 20% to 30% of wild-type mice (genotype G-CSF+/+) and mice heterozygous for the null mutation had intermediate neutrophil levels, suggesting a gene-dosage effect . In the marrow of G-CSF-/- mice, granulopoietic precursor cells were reduced by 50% and there were reduced levels of granulocyte, macrophage, and blast progenitor cells . Despite G-CSF deficiency, mature neutrophils were still present in the blood and marrow, indicating that other factors can support neutrophil production in vivo . G-CSF-/- mice had reduced numbers of neutrophils available for rapid mobilization into the circulation by a single dose of G-CSF . G-CSF administration reversed the granulopoietic defect of G-CSF-/- mice . One day of G-CSF administration to G-CSF-/- mice elevated circulating neutrophil levels to normal, and after 4 days of G-CSF administration, G-CSF+/+ and G-CSF-/- marrows were morphologically indistinguishable . G-CSF-/- mice had a markedly impaired ability to control infection with Listeria monocytogenes, with diminished neutrophil and delayed monocyte increases in the blood and reduced infection-driven granulopoiesis . Collectively, these observations indicate that G-CSF is indispensible for maintaining the normal quantitative balance of neutrophil production during "steady-state" granulopoiesis in vivo and also implicate G-CSF in "emergency" granulopoiesis during infections. J Infect Dis, 1994 Sep, 170(3), 693 - 6 A point-source foodborne listeriosis outbreak: documented incubation period and possible mild illness; Riedo FX et al.; Listeria bacteremia occurred in 2 pregnant women whose only common exposure was attendance at a party . The incubation period, the possibility of mild disease due to Listeria infection, and foods associated with risk of disease were evaluated . Ten (28%) of 36 party attenders met a case definition, which included isolation of Listeria monocytogenes from blood or stool or two of the following: fever, musculoskeletal symptoms, nausea, vomiting, diarrhea . One of 25 stool cultures was positive . The 2 blood isolates and 1 stool isolate were serotype 4b and identical by enzyme typing . The incubation periods for illness in the 2 pregnant women were 19 and 23 days . Consumption of large amounts of shrimp, nonalcoholic beverages, Camembert cheese, and cauliflower was significantly associated with illness . Eating shrimp remained a significant risk factor for illness after controlling for consumption of other foods . This study suggests a milder illness may exist in healthy persons who consume foods contaminated with L . monocytogenes and demonstrates a prolonged incubation period for disease. Infect Immun, 1994 Sep, 62(9), 3649 - 54 Cytokine gene expression in mice at an early stage of infection with various strains of Listeria spp . differing in virulence; Xiong H et al.; By using reverse transcription-PCR, cytokine gene expression was examined in mice 24 h after infection with various strains of Listeria spp . differing in virulence as determined by in vivo growth and 50% lethal dose values . All the virulent strains of Listeria monocytogenes induced the expression of mRNAs specific for interleukin-1 alpha (IL-1 alpha), gamma interferon (IFN-gamma), and tumor necrosis factor alpha (TNF-alpha) in the spleen of mice, while an L . monocytogenes strain incapable of producing listeriolysin O and strains of Listeria innocua induced the expression of TNF-alpha mRNA only . The levels of expression of IL-1 alpha and IFN-gamma mRNAs were proportional to the levels of listeriolysin O produced by each strain . Those strains which induced the expression of IFN-gamma were capable of generating protective immunity in the infected host, suggesting that the virulence-related induction of some cytokine at the initial stage of infection plays a role in the induction of acquired cellular resistance to L . monocytogenes. J Immunol, 1994 Sep 1, 153(5), 2093 - 101 Endogenous IL-1 is required for neutrophil recruitment and macrophage activation during murine listeriosis; Rogers HW et al.; By using a mixture of neutralizing mAbs to IL-1 alpha, IL-1 beta, and to the type I IL-1R, we previously documented a regulatory role for IL-1 in the development of anti-Listeria responses in mice . Both normal C.B-17 and severe combined immunodeficiency (SCID) mice injected with this mixture of Abs exhibit decreased resistance to Listeria . In this study, we demonstrate that the neutralization of IL-1 activity in SCID mice results in a major defect in neutrophil migration to the peritoneum, in response to Listeria infection . Moreover, anti-IL-1 treatment also inhibits Listeria-induced peripheral blood leukocytosis at all time points examined . We also show that mice injected with anti-IL-1 Abs failed to elaborate class II MHC-positive peritoneal macrophages in vivo at any time during Listeria infection . Even though peritoneal macrophages from anti-IL-1-treated Listeria-infected mice are not activated to express MHC class II molecules, IFN-gamma production in vivo is normal . Moreover, the macrophages are unresponsive to IFN-gamma in vitro, as assayed by MHC class II expression, even when rIL-1 is added . rIL-1 also is unable to increase the expression of IFN-gamma-induced surface class II MHC molecules on resident peritoneal macrophages in vitro . These results indicate that endogenously produced IL-1 plays an important role in Listeria-dependent neutrophil migration, increase in blood leukocyte number, generation of MHC class II-positive macrophages in vivo, and macrophage responsiveness to IFN-gamma. Plast Reconstr Surg, 1994 Sep, 94(3), 531 - 3; discussion 534-5 Listeria infection of silicone breast implant; Gnanadesigan N et al.; A case of breast implant infection with L . monocytogenes is presented . The nature of this organism, its usual mode of transmission, and factors predisposing to the development of listeriosis are reviewed . We speculate that, in this case, the organism was acquired during a natural period of depressed immunity due to pregnancy, and it initiated a low-grade infection around the breast prosthesis . Possible implications of this scenario are discussed. J Appl Bacteriol, 1994 Sep, 77(3), 242 - 50 RAPD typing for distinguishing species and strains in the genus Listeria; Farber JM et al.; The randomly amplified polymorphic DNA (RAPD) technique was employed in the development of a typing protocol for Listeria isolates, particularly Listeria monocytogenes strains . A single strain of L . monocytogenes was used and 200 random decamer primers were screened for their discriminatory abilities by visualizing the amplification products electrophoretically . Three candidate primers displaying potentially useful banding patterns were selected and tested against 52 L . monocytogenes strains, encompassing 11 serotypes, and 12 other strains representing five other Listeria spp . Thirty-four banding profiles were obtained with one particular primer . RAPD analysis allowed differentiation between Listeria spp . and was found to further subdivide strains of the same serotype . Where only one primer was used strains from different serotypes were occasionally found to produce identical banding profiles . RAPD analysis, which in our hands proved to be reproducible, shows much promise as a molecular alternative to traditional L . monocytogenes typing protocols. Appl Environ Microbiol, 1994 Sep, 60(9), 3198 - 203 Evaluation of lactic acid bacterium fermentation products and food-grade chemicals to control Listeria monocytogenes in blue crab (Callinectes sapidus) meat; Degnan AJ et al.; Fresh blue crab (Callinectes sapidus) meat was obtained from retail markets in Florida and sampled for viable Listeria monocytogenes . The pathogen was found in crabmeat in three of four different lots tested by enrichment and at levels of 75 CFU/g in one of the same four lots by direct plating . Next, crabmeat was steam sterilized, inoculated with a three-strain mixture of L . monocytogenes (ca . 5.5 log10 CFU/g), washed with various lactic acid bacterium fermentation products (2,000 to 20,000 arbitrary units {AU}/ml of wash) or food-grade chemicals (0.25 to 4 M), and stored at 4 degrees C . Counts of the pathogen remained relatively constant in control samples during storage for 6 days, whereas in crabmeat washed with Perlac 1911 or MicroGard (10,000 to 20,000 AU), numbers initially decreased (0.5 to 1.0 log10 unit/g) but recovered to original levels within 6 days . Numbers of L . monocytogenes cells decreased 1.5 to 2.7 log10 units/g of crabmeat within 0.04 day when washed with 10,000 to 20,000 AU of Alta 2341, enterocin 1083, or Nisin per ml . Thereafter, counts increased 0.5 to 1.6 log10 units within 6 days . After washing with food-grade chemicals, modest reductions (0.4 to 0.8 log10 unit/g) were observed with sodium acetate (4 M), sodium diacetate (0.5 or 1 M), sodium lactate (1 M), or sodium nitrite (1.5 M) . However, Listeria counts in crabmeat washed with 2 M sodium diacetate decreased 2.6 log10 units/g within 6 days . In addition, trisodium phosphate reduced L . monocytogenes counts from 1.7 (0.25 M) to > 4.6 (1 M) log10 units/g within 6 days.(ABSTRACT TRUNCATED AT 250 WORDS) Appl Environ Microbiol, 1994 Sep, 60(9), 3120 - 7 Synthetic peptides derived from the Listeria monocytogenes p60 protein as antigens for the generation of polyclonal antibodies specific for secreted cell-free L . monocytogenes p60 proteins; Bubert A et al.; All species of the genus Listeria secrete a major extracellular protein called p60 . A comparison of the deduced amino acid sequences of all listerial p60 proteins previously indicated there were only a few regions which were unique to the pathogenic, food-borne species Listeria monocytogenes . Two of these p60 regions were chosen for the development of antibodies specific for the facultative intracellular species L . monocytogenes . Initially, these regions were characterized via epitope mapping, and this led to the development of two different synthetic peptides . Rabbits immunized with these synthetic peptides generated polyclonal antibodies that were then used in Western blot (immunoblot) analyses . Antiserum against peptide A (PepA) recognized the p60 protein in the supernatants collected from most L . monocytogenes serotypes except for several strains belonging to serotypes 4a and 4c . No p60-related protein was detected in the supernatants from other Listeria species with this anti-PepA antiserum . Antibodies raised against peptide D (PepD) reacted with p60 from all L . monocytogenes serotypes, including all 4a and 4c strains that were tested, and also showed no cross-reactivity with supernatant proteins from other Listeria species . Both antisera also detected p60 in supernatants of a large number of environmental isolates of L . monocytogenes . Besides Western blot analyses, these antisera to PepA and PepD reacted with secreted p60 in an enzyme-linked immunosorbent assay, indicating recognition of the native antigen in addition to the denatured form . These data suggest that synthetic peptides derived from the variable region of the L . monocytogenes p60 protein may be useful for the development of an immunological diagnostic assay. FEMS Microbiol Lett, 1994 Sep 1, 121(3), 287 - 91 Transposon-induced mutants of Listeria monocytogenes incapable of growth at low temperature (4 degrees C); Zheng W et al.; Transposon mutagenesis was used to pursue the molecular basis of cold resistance in Listeria and its possible involvement in pathogenesis . We have generated transposon-induced mutants of Listeria monocytogenes which were unable to grow at 4 degrees C but grew at 8 degrees C, 22 degrees C and 37 degrees C . The transposon was localized in the same 1.8-kb EcoRI fragment in two independently derived mutants . Mutants which carried single transposon insertions had normal hemolytic activity, motility and invasion of cultured fibroblasts . These results indicate that in L . monocytogenes cold sensitivity can be single transposon insertions and that loss of cold resistance may not interfere with other phenotypes, including invasion in a cell culture model. Cell Immunol, 1994 Sep, 157(2), 403 - 14 The role of B cells in in vitro induction of IFN-gamma-producing CD4+ T cells specific to Listeria monocytogens: positive and IL-10-mediated negative regulation; Song F et al.; We have reported that Listeria monocytogenes-specific IFN-gamma-producing CD4+ T cells are induced by in vitro 5-day culture of naive spleen cells with viable L . monocytogenes (VLM), but not induced by culture with heat-killed L . monocytogenes (HKLM) . In the present study, the role of B cells in the regulation of induction of IFN-gamma-producing CD4+ T cells in the in vitro system was investigated . We found that L . monocytogenes-specific IFN-gamma-producing CD4+ T cells were not generated when B cells were depleted from spleen cells before culture with VLM although Ag-specific proliferative response was retained . IFN-gamma production by CD4+ T cells was restored by addition of B cells cultured with VLM to the culture of B cell-depleted spleen cells and VLM . In contrast, B cells cultured with HKLM could not restore the induction of IFN-gamma production when added in culture of B cell-depleted spleen cells and VLM . Analysis of cytokine gene expression by reverse transcription-polymerase chain reaction method revealed that expression of interleukin-10 (IL-10) was higher but TNF-alpha was lower in B cells cultured with HKLM when compared with that in B cells cultured with VLM . Furthermore, addition of neutralizing anti-IL-10 mAb into culture of naive spleen cells with HKLM resulted in appearance of IFN-gamma-producing cells . These results suggest that B cells have positive and negative roles in the induction of IFN-gamma-producing CD4+ T cells . The inhibition of induction of IFN-gamma-producing CD4+ T cells may depend on B cell-derived IL-10. Diagn Microbiol Infect Dis, 1994 Sep, 20(1), 21 - 5 Assessment of the bactericidal activity of sparfloxacin, ofloxacin, levofloxacin, and other fluoroquinolones compared with selected agents of proven efficacy against Listeria monocytogenes; Cherubin CE et al.; The search for alternative therapeutic agents for listeriosis includes the quinolone group . Accordingly, the bactericidal activity of ciprofloxacin, levofloxacin, lomefloxacin, ofloxacin, sparfloxacin, and temofloxacin, in comparison with that of ampicillin and sulfamethoxazole-trimethoprim, was evaluated against Listeria monocytogenes at 24 and 48 h of incubation using time-kill kinetic methodology . The inhibitory concentrations for each agent fell into a narrow range comparable with ampicillin . For example, the minimum inhibitory concentration (MIC) ranges, MIC90 (24 h), and MIC90 (48 h) of the most active quinolone, sparfloxacin, were 0.25-2, 2, and 2 micrograms/ml, respectively, with 4 micrograms/ml achieving > or = 99.9% killing of the inoculum at 24 h with no regrowth by 48 h . At 2-4 times the MIC, bactericidal activity for all quinolones tested was noted at 24 h, unlike the action of ampicillin, which only becomes bactericidal at 48 h . These concentrations are within the achievable range of serum concentrations for a number of these agents . Because selected new fluoroquinolones at two to four times the MIC show bactericidal activity at 24 h, these agents may prove useful as therapeutic alternatives for the treatment of listeriosis. Med J Malaysia, 1994 Sep, 49(3), 217 - 22 Incidence of Listeria spp . in vegetables in Kuala Lumpur; Tang MY et al.; From April 1992 to September 1992, 280 samples of 10 different fresh vegetables, bought from four different market outlets in Kuala Lumpur were examined for the presence of Listeria spp . Most of the market produce were locally grown with the exception of carrots . The isolation procedure was based on the Food & Drug Administration method (modified) used for the detection of Listeria spp . Isolation media used were Listeria Selective medium and LiCl- phenylethanol-Moxalactam agars . The identification of isolates was by means of conventional biochemical tests and API Listeria identification system . Five out of the 280 samples showed Listeria contamination, Listeria monocytogenes was isolated in lettuce, sengkuang (Pachyrrhizus erosus) and selom Oenanthe javanica) and Listeria innocua was isolated from sengkuang (Pachyrrhizus erosus) and pegaga (Hydrocotyle asiatica). Int J Food Microbiol, 1994 Sep, 23(1), 17 - 34 Presence, detection and growth of Listeria monocytogenes in seafoods: a review; Ben Embarek PK; Listeria monocytogenes and other Listeria spp . have been isolated from seafoods on a regular basis since 1987 . A relatively high incidence of the organism (6-36%) in ready-to-eat cold smoked salmon and cooked fish products has raised concern about the survival and growth potential of this organism in seafoods, as these products are not processed further before consumption . L . monocytogenes grows well at refrigeration temperature on most seafoods, but the sources of contamination in ready-to-eat fish products are still unknown . This paper reviews the knowledge available in order to make recommendations on control options and avenues for future research. Int J Food Microbiol, 1994 Sep, 23(1), 117 - 21 Prevalence of Listeria monocytogenes in foods in Malaysia; Arumugaswamy RK et al.; A total of 234 samples of food, consisting of 158 of raw and 76 samples of ready-to-eat food were examined for the presence of Listeria monocytogenes . The frequencies of L . monocytogenes contamination in raw foods were: chicken portions (60%), liver (60%) and gizzard (62%), beef (50%), beansprout (85%), prawns (44%), kupang (dried oysters) (33%), bean cake (25%), satay (48%) and leafy vegetables (22%) . Of the ready-to-eat foods: satay (26%), prawns, squids, clams and chicken dishes (22%), cucumber (80%) and peanut sauce (20%) were found to yield L . monocytogenes. Int J Immunopharmacol, 1994 Sep, 16(9), 747 - 54 Factors involved in the down-regulation of cytochrome P450 during Listeria monocytogenes infection; Armstrong SG et al.; The activation of host defense mechanisms has been shown to cause a depression in hepatic cytochrome P450-mediated metabolism in rodents and humans . In a previous study, it was demonstrated that the Gram-positive bacteria Listeria monocytogenes causes a down-regulation of hepatic cytochrome P450 and related substrate metabolism as a result of a pretranslational depression of apoprotein synthesis . The objectives of this study were to determine whether the effect of listeria on hepatocyte cytochrome P450 involves hepatic nonparenchymal cells and whether the hemolysin, secreted only by hemolytic forms of the bacteria, plays any part in mediating this effect . Total cytochrome P450 levels as well as ethoxyresorufin-O-dealkylase (EROD) and benzyloxyresorufin-O-dealkylase (BROD) activities were significantly reduced in hepatic microsomes isolated from mice infected in vivo for 48 h with 15U listeria, whereas the same dose of the avirulent non-hemolytic M3D strain had no effect . Listeria (15U) significantly depressed hepatocyte EROD and BROD activities after 24 h incubations with liver cell cultures containing hepatocytes and nonparenchymal cells, as the result of both a direct effect on the hepatocyte and an interaction of listeria with hepatic nonparenchymal cells . The M3D strain of listeria had no effect on cytochrome P-450-mediated metabolism in isolated cells, confirming that hemolysin is an essential component of the mechanism responsible for the down-regulation of cytochrome P450 during listeria infections. Minerva Pediatr, 1994 Sep, 46(9), 395 - 9 {Fatal neonatal listeriosis after maternal infection acquired with ingestion of fresh home-made cheese}; Negri F et al.; The authors report on a newborn admitted to the Intensive Care Unit of Gaslini Institute for serious respiratory insufficiency who died on the third day of life because of a sepsis due to Listeria monocytogenes . The authors focus on the patient's history and clinical picture and on the histological evaluation of the lesions observed . The importance of infection in pregnancy and the possible severe consequences of listeriosis on the foetus are underlined, stressing the need for early diagnosis and adequate treatment. Arch Latinoam Nutr, 1994 Sep, 44(3), 158 - 63 {Occurrence of Listeria monocytogenes in raw milk, pasteurized type C milk and minas frescal cheese commercialized in Piracicaba-São Paulo}; Casarotti VT et al.; Samples of raw milk, pasteurized C type milk and minas frescal cheese were analyzed for the presence of Listeria monocytogenes by a method developed for dairy products by Lovett (1) and by Lovett & Hitchins (2) . A total of 20 samples of each product and from different commercial brands were analyzed, obtained from various retail stores in Piracicaba, SP . According to the pattern of sampling and methodology adopted, none of the samples of the aforesaid products was positive for the presence of L . monocytogenes or another species of the genus . It was possible to observe differences in the degree of selectivity of the selective media utilized, notwithstanding the LPM agar showing to be superior to MMA . Based on the literature and on the result obtained, becomes evident the need of a more suitable method for the detection and isolation of L . monocytogenes from foods, even when the patogen appears in low numbers, with purpose to obtain rapid, reliable and reproducible results. Microb Pathog, 1994 Sep, 17(3), 175 - 86 Recombinant interleukin-12 enhances resistance of mice to Listeria monocytogenes infection; Wagner RD et al.; The effect of recombinant murine IL-12 (rIL-12) or anti-IL-12 antibody administration on resistance to murine listeriosis was investigated . Mice given a single 0.5 micrograms dose of rIL-12 had 1.5 log10 fewer listeriae in their spleens and livers as compared with control infected mice 3 days after L . monocytogenes challenge . Conversely, administration of anti-IL-12 IgG caused an equivalent increase in the cfu of L . monocytogenes recovered from the spleens and livers as compared to control mice . This is the first report of such a protective effect from a single dose of rIL-12 . Treatment of uninfected mice with rIL-12 induced IFN-gamma mRNA production in their livers . Infection of mice with L . monocytogenes caused a similar increase in IFN-gamma mRNA levels that was not increased further by concurrent treatment with rIL-12 . Treatment of mice with an anti-IFN-gamma MAb eliminated the protective effect of IL-12 on Listeria infection . Expression of TNF-alpha, IL-10 and IL-12p40 mRNA in L . monocytogenes-infected mice were not significantly altered by administration of either anti-IL-12 IgG or rIL-12 . rIL-12 administration was associated with increased serum AST levels, a measure of liver damage, 1 day after treatment in L . monocytogenes-infected mice . In addition, rIL-12 administration was associated with the increased presence of small inflammatory foci and necrotic hepatocytes in both infected and uninfected mice, suggesting a proinflammatory role for IL-12 in the liver. Immunity, 1994 Sep, 1(6), 479 - 89 Efficiency of MHC class I antigen processing: a quantitative analysis; Villanueva MS et al.; Listeria monocytogenes is an intracellular pathogen that secretes proteins into host cell cytosol . One such protein, the murein hydrolase p60, is processed by the host cell into the nonamer peptide p60 217-225 and presented to cytotoxic T lymphocytes by the H-2Kd MHC class I molecule . Using strains of L . monocytogenes that secrete different amounts of p60, we show that the rate of p60 217-225 production is proportional to the quantity of intracellular antigen . The appearance of p60 217-225 is coupled to the degradation of newly synthesized p60 . By accounting for the rate of intracellular antigen secretion and degradation, we estimate that approximately 35 p60 molecules are degraded to produce one p60 217-225 epitope . These findings provide an estimate of the efficiency of antigen processing and shed light on the capacity of the MHC class I antigen processing pathway to accommodate foreign antigens. Appl Environ Microbiol, 1994 Sep, 60(9), 3416 - 8 Enhanced sensitivity in PCR detection of Listeria monocytogenes in soft cheese through use of an aqueous two-phase system as a sample preparation method; Lantz PG et al.; A sample treatment method based on an aqueous two-phase system containing polyethylene glycol and dextran was developed for enhancing sensitivity in the detection of Listeria monocytogenes in soft cheese with PCR . The results suggest that the improved detection sensitivity following partitioning of the cheese homogenate in an aqueous two-phase system may be due to partitioning of the PCR inhibitors to the polyethylene glycol phase. Appl Environ Microbiol, 1994 Aug, 60(8), 3023 - 6 Detection of multiple virulence-associated genes of Listeria monocytogenes by PCR in artificially contaminated milk samples; Cooray KJ et al.; The inhibitory effect of milk in the PCR detection of Listeria monocytogenes could be overcome by washing the contaminated milk sample with phosphate-buffered saline and concentrating the bacteria to 1/10 of the original volume . In order to avoid a possible failure in the detection of virulent L . monocytogenes, a one-step procedure which enabled demonstration of three virulence-associated genes, prfA, hlyA, and plcB, simultaneously in a single PCR mixture was developed. J Leukoc Biol, 1994 Aug, 56(2), 174 - 81 Differentiated U937 cells exhibit increased bactericidal activity upon LPS activation and discriminate between virulent and avirulent Listeria and Brucella species; Caron E et al.; In the study of interactions between facultative intracellular pathogens and macrophages, monocytic cell lines have the advantages of showing defined states of activation and lacking genetic variation among donors, thus yielding reproducible results . Nonpathogenic Escherichia coli K12 were killed at similar rates in the U937 cell line differentiated into macrophage-like cells by phorbol myristate acetate (PMA) or by the combination of retinoic acid (RA) and vitamin D3 (VD) . Complete elimination was reached only when cells were activated by lipopolysaccharide for 30 min prior to infection, and it was further enhanced when bacteria were opsonized by specific immunoglobulin G . Both types of differentiation led to intracellular multiplication of virulent Listeria monocytogenes and to elimination of the animal pathogen Listeria ivanovii . For both strains, conditions for intracellular survival were more favorable in PMA-differentiated U937 . During infection, RA/VD-differentiated U937 could discriminate between the human pathogen Brucella suis S1, which strongly multiplied, and the animal pathogen Brucella canis, which survived without multiplication . U937 cells differentiated by RA and VD therefore represent a basic model in bacteria-human macrophage interactions. J Am Dent Assoc, 1994 Aug, 125 Suppl 2, 29S - 32S Expanded and future uses of mouthrinses; Ciancio S; The use of antimicrobial mouthrinses is important to dental professionals and their patients . Listerine Antiseptic was found to greatly decrease the anaerobic and aerobic bacteria associated with bacteremia, when used as a subgingival irrigant prior to scaling . Furthermore, preprocedural rinsing with either Listerine or chlorhexidine gluconate (Peridex) can greatly decrease the number of bacteria aerosolized during many dental procedures . Studies have shown that both Listerine and chlorhexidine have anti-Candida properties and therefore are helpful to patients who are immunosuppressed and subject to the opportunistic infection of candidiasis . Chlorhexidine has also been shown to decrease the incidence and severity of mucositis during cancer chemotherapy . Healing of the wounds and aiding in plaque control following periodontal surgery are further benefits of chlorhexidine and Listerine . Finally, each of these antimicrobials can be adjuncts to implant maintenance. J Am Dent Assoc, 1994 Aug, 125 Suppl 2, 20S - 22S A clinician's perspective on antimicrobial mouthrinses; Fischman SL; Today's dental professional must advise patients as to the antimicrobial mouthrinse appropriate for their periodontal condition . Considerations such as chemical nature, mechanism of action, efficacy, and safety of mouthrinses are important to the clinician . Taste and cost are equally important considerations to the patient . No ideal antimicrobial mouthrinse exists; yet, chlorhexidine gluconate (Peridex), Listerine, and two of its generic equivalents have the American Dental Association's Seal of Acceptance . An expanded role of antimicrobial mouthrinses that holds promise is that of preprocedural rinsing . This protocol can decrease the number of microorganisms aerosolized during numerous dental procedures. J Am Dent Assoc, 1994 Aug, 125 Suppl 2, 2S - 10S Antimicrobial mouthrinses: overview and update; Mandel ID; The Seal of Acceptance of the American Dental Association's Council on Dental Therapeutics has been awarded to Listerine and chlorhexidine gluconate (Peridex) . The mechanism of action of Listerine involves bacterial cell wall destruction, bacterial enzymatic inhibition, and extraction of bacterial lipopolysaccharides . Chlorhexidine has the property of substantivity, i.e . the ability to bind to hard and soft tissue with slow release . Antibacterial mouthrinses/dentifrices containing triclosan hold promise for the reduction of plaque and gingivitis but are not yet available in the United States . The quaternary ammonium compounds and sanguinarine compounds (Viadent) have some merit, but studies of their efficacy in plaque and gingivitis reduction are mixed . New products containing various fluorides and oxygenating agents may have potential for the future as antiplaque and antigingivitis agents. Crit Care Nurse, 1994 Aug, 14(4), 22, 25 - 30, quiz 31-2 Listeria meningitis: a case study; Mickles LI et al.; This case illustrates that L monocytogenes should always be considered as a potential cause of clinical meningitis, especially in an immunocompromised patient . The incidence of undetected or misdiagnosed Listeria organisms (as revealed in autopsies) is high enough that extra caution should be taken to ensure that an organism is not simply disregarded as a contaminant. Infect Immun, 1994 Aug, 62(8), 3554 - 8 Ultrastructural study of Listeria monocytogenes entry into cultured human colonic epithelial cells; Karunasagar I et al.; Evidence that Listeria monocytogenes enters Caco-2 cells through the apical surface is presented . Attachment of bacteria to host cells seems to induce modifications of microvilli which are either in direct contact with the bacterial surface or in close vicinity, resulting in the formation of lamellipodia involved in the cellular uptake of the bacteria . Such modifications are not induced by L . monocytogenes SLCC 53, which carries a deletion in the prfA gene, although attachment of this mutant to Caco-2 cells occurs . Listeria innocua does not attach well to Caco-2 cells and also fails to cause structural alterations of the microvilli . Treatment of confluent monolayers of Caco-2 cells with ethylene glycol-bis(beta-aminoethyl ether)- N,N,N1,N1-tetraacetic acid (EGTA), which disrupts intercellular junctions, greatly reduced the uptake of Listeria cells . Attachment and invasion of L . monocytogenes was not accompanied by accumulation of filamentous actin around the entering bacterial cell. Infect Immun, 1994 Aug, 62(8), 3550 - 3 The virulence gene cluster of Listeria monocytogenes is also present in Listeria ivanovii, an animal pathogen, and Listeria seeligeri, a nonpathogenic species; Gouin E et al.; Most known Listeria monocytogenes virulence genes cluster within a 9.6-kb chromosomal region . This region is flanked on one end by two uncharacterized open reading frames (ORF A and ORF B) and ldh, an ORF presumably encoding the L . monocytogenes lactate dehydrogenase (J.-A . Vazquez-Boland, C . Kocks, S . Dramsi, H . Ohayon, C . Geoffroy, J . Mengaud, and P . Cossart, Infect . Immun . 60:219-230, 1992) . We report here that the other end is flanked by prs, and ORF homologous to phosphoribosyl PPi synthetase genes . ORF B and prs were detected in all Listeria species and thus delimit the virulence region . This virulence gene cluster was detected exclusively in hemolytic Listeria species, Listeria ivanovii, an animal pathogen, and Li