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PubMed2004

Molecular and physiological analysis of the role of osmolyte transporters BetL, Gbu, and OpuC in growth of Listeria monocytogenes at low temperatures.

Listeria monocytogenes is a ubiquitous food-borne pathogen found widely distributed in nature as well as an undesirable contaminant in a variety of fresh and processed foods. This ubiquity can be at least partly explained by the ability of the organism to grow at high osmolarity and reduced temperatures, a consequence of its ability to accumulate osmo- and cryoprotective compounds termed osmolytes. Single and multiple deletions of the known osmolyte transporters BetL, Gbu, and OpuC significantly reduce growth at low temperatures. During growth in brain heart infusion broth at 7 degrees C, Gbu and OpuC had a more pronounced role in cryoprotection than did BetL. However, upon the addition of betaine to defined medium, the hierarchy of transporter importance shifted to Gbu > BetL > OpuC. Upon the addition of carnitine, only OpuC appeared to play a role in cryoprotection. Measurements of the accumulated osmolytes showed that betaine is preferred over carnitine, while in the absence of a functional Gbu, carnitine was accumulated to higher levels than betaine was at 7 degrees C. Transcriptional analysis of the genes encoding BetL, Gbu, and OpuC revealed that each transporter is induced to different degrees upon cold shock of L. monocytogenes LO28. Additionally, despite being transcriptionally up-regulated upon cold shock, a putative fourth osmolyte transporter, OpuB (identified by bioinformatic analysis and encoded by lmo1421 and lmo1422), showed no significant contribution to listerial chill tolerance. Growth of the quadruple mutant LO28deltaBCGB (deltabetL deltaopuC deltagbu deltaopuB) was comparable to the that of the triple mutant LO28deltaBCGsoe (deltabetL deltaopuC deltagbu) at low temperatures. Here, we conclude that betaine and carnitine transport upon low-temperature exposure is mediated via three osmolyte transporters, BetL, Gbu, and OpuC.

ATP-Binding Cassette Transporters↗
PubMed2001

The use of host cell machinery in the pathogenesis of Listeria monocytogenes.

The bacterial pathogen, Listeria monocytogenes, exploits the host cell's machinery, enabling the pathogen to enter into cells and spread from cell to cell. Three bacterial surface proteins are crucial for these processes: internalin and InlB, which mediate entry into cells, and ActA, which induces actin polymerisation at one pole of the bacterium and promotes intracellular and intercellular motility. Recent studies have identified several of the cellular factors involved in the entry process and major discoveries have unravelled the mechanisms underlying the actin-based motility. Increasing evidence shows that many cellular genes are up- or down-regulated during infection and probably play a role in the establishment of infection, inflammation and induction of the host immune response.

Amino Acid Sequence↗
PubMed2002

A proteomic analysis of the salt stress response of Listeria monocytogenes.

Protein variations in Listeria monocytogenes were analyzed by 2-D electrophoresis. Bacteria were grown either in a rich medium or in a chemically defined medium. Three proteins, which are more expressed in the chemically defined medium than in the rich medium, were identified by mass spectrometry. They are closely related to AppA, Ctc and YvyD. After an osmotic shock, according to the medium and the NaCl concentration, the synthesis rate (P<0.05) of 59 proteins is altered by salinity. Half of them were more expressed, some of these proteins were closely related to Ctc, GbuA and the 30S ribosomal protein S6. Among the proteins which were down-expressed in the presence of salt, two were similar to AckA and PdhD.

Bacterial Proteins↗
PubMed1990

Participation of PBP 3 in the acquisition of dicloxacillin resistance in Listeria monocytogenes.

Purified membranes of Listeria monocytogenes ATCC 15313 contain at least five penicillin-binding proteins. In two dicloxacillin-resistant mutants, derived from a sensitive parent strain, a 16-fold increase in the MIC of dicloxacillin was observed. A less-significant increase was detected in the MICs of other beta-lactam drugs. In the mutants, PBP 3 lost its strong affinity for dicloxacillin, but remained fully susceptible to binding of 125I-penicillin X, as compared with the wild-type strain. PBP 2 could not be detected in one of the mutants. No decrease in affinity for the radioactive tracer or dicloxacillin was detected in any other PBP of the resistant mutants.

Acyltransferases↗
PubMed2002

Salt stress proteins induced in Listeria monocytogenes.

The ability of Listeria monocytogenes to tolerate salt stress is of particular importance, as this pathogen is often exposed to such environments during both food processing and food preservation. In order to understand the survival mechanisms of L. monocytogenes, an initial approach using two-dimensional polyacrylamide gel electrophoresis was performed to analyze the pattern of protein synthesis in response to salt stress. Of 400 to 500 visible proteins, the synthesis of 40 proteins (P < 0.05) was repressed or induced at a higher rate during salt stress. Some of the proteins were identified on the basis of mass spectrometry or N-terminal sequence analysis and database searching. Twelve proteins showing high induction after salt stress were similar to general stress proteins (Ctc and DnaK), transporters (GbuA and mannose-specific phosphotransferase system enzyme IIAB), and general metabolism proteins (alanine dehydrogenase, CcpA, CysK, EF-Tu, Gap, GuaB, PdhA, and PdhD).

Amino Acid Sequence↗
PubMed2001

Synergy between the N- and C-terminal domains of InlB for efficient invasion of non-phagocytic cells by Listeria monocytogenes.

InlB is a Listeria monocytogenes protein promoting entry in non-phagocytic cells, and has been shown recently to activate the hepatocyte growth factor receptor (HGFR or Met). The N-terminal domain of InlB (LRRs) binds and activates Met, whereas the C-terminal domain of InlB (GW modules) mediates loose attachment of InlB to the listerial surface. As HGF activation of Met is tightly controlled by glycosaminoglycans (GAGs), we tested if GAGs also modulate the Met-InlB interactions. We show that InlB-dependent invasion of non-phagocytic cells decreases up to 10 times in the absence of GAGs, and that soluble heparin releases InlB from the bacterial surface and promotes its clustering. Furthermore, we demonstrate that InlB binds cellular GAGs by its GW modules, and that this interaction is required for efficient InlB-mediated invasion. Therefore, GW modules have an unsuspected dual function: they attach InlB to the bacterial surface and enhance entry triggered by the LRRs domain. Our results thus provide the first evidence for a synergy between two host factor-binding domains of a bacterial invasion protein, and reinforce similarities between InlB and mammalian growth factors.

Animals↗
PubMed2006

Cytolysin-dependent delay of vacuole maturation in macrophages infected with Listeria monocytogenes.

The bacterial pathogen Listeria monocytogenes (Lm) evades the antimicrobial mechanisms of macrophages by escaping from vacuoles to the cytosol, through the action of the cytolysin listeriolysin O (LLO). Because of heterogeneities in the timing and efficiency of escape, important questions about the contributions of LLO to Lm vacuole identity and trafficking have been inaccessible. Expression of cyan fluorescent protein (CFP)-labelled endocytic membrane markers in macrophages along with a yellow fluorescent protein (YFP)-labelled indicator of Lm entry to the cytosol identified compartments lysed by bacteria. Lm escaped from Rab5a-negative, lysosome-associated membrane protein-1 (LAMP1)-negative, Rab7-positive, phosphatidylinositol 3-phosphate [PI(3)P]-positive vacuoles. Lm vacuoles did not label with YFP-Rab5a unless the bacteria were first opsonized with IgG. Wild-type Lm delayed vacuole fusion with LAMP1-positive lysosomes, relative to LLO-deficient Lm. Bacteria prevented from expressing LLO until their arrival into LAMP1-positive lysosomes escaped inefficiently. Thus, the LLO-dependent delay of Lm vacuole fusion with lysosomes affords Lm a competitive edge against macrophage defences by providing bacteria more time in organelles they can penetrate.

Animals↗
PubMed1999

Effect of osmotic, alkaline, acid or thermal stresses on the growth and inhibition of Listeria monocytogenes.

Five strains of Listeria monocytogenes (a, b, c, d and e) isolated from industrial plants have been subjected to different osmotic, alkaline, acid or thermal stresses. The effects of these treatments on lag-phase (L) and growth rate (mu) of cells in mid-log phase have been followed using an automated optical density monitoring system. Increasing the osmotic pressure by the addition of different amounts of NaCl increased the lag phase and decreased the growth rate. The same phenomena were observed after decreasing the pH of the medium to 5.8, 5.6 or 5.4 by addition of acetic, lactic or hydrochloric acids. The inhibitory effect was: acetic acid > lactic acid > hydrochloric acid. The addition of NaOH to attain pH values of 9.5, 10.0, 10.5 or 11.0 in the medium produced a dramatic increase of the lag phase at pH 10.5 and 11. Growth rates were also decreased while the maximal population increased with high pH values. These effects varied according to strains. Strains d and e were the most resistant to acidic and alkaline stresses, and e was the most affected by the addition of NaCl. A cold shock of 30 min at 0 degree C had limited effects on growth parameters. On the other hand, hyperthermal shocks (55 or 63 degrees C, 30 min) led to similar increased lag phases and to significant increases of the maximal population in all five strains.

Acetic Acid↗
PubMed1981

[Listeria monocytogenes meningitis (author's transl)].

Listeria monocytogenes meningitis was observed in a 24-year-old obese patient. Morphology and serology of CSF bacterial isolates indicated beta-haemolytic streptococci group B first. However, further differentiation permitted certain classification as Listeria monocytogenes serovar 4b. Treatment with erythromycin (2 g/d) and gentamicin (40 mg t.i.d.) led to rapid improvement of clinical symptoms.

Adult↗
PubMed1988

Survival of Listeria monocytogenes in ground beef.

Listeria monocytogenes, due to its association with animals and animal products and its proven pathogenicity, is an organism of potential importance to the meat industry. The survival of L. monocytogenes in ground beef held at 4 degrees C for 2 weeks was investigated. The ground beef was inoculated with L. monocytogenes type 1 or type 4 at a level of 5 x 10(5) to 7 x 10(6) CFU/g and then packaged in either oxygen-permeable or oxygen-impermeable bags. Packages were sampled at random at 0, 2, 3, 5, 7, 11, and 14 days post-inoculation, and assayed for L. monocytogenes counts and pH. The number of L. monocytogenes in ground beef remained constant throughout the sampling period, and survival was not affected by package permeability to oxygen. Listeriae were not isolated from the control ground beef. The pH of the meat increased slightly during storage, but was always in the range of pH 5.6 to 5.9. It appears that L. monocytogenes in ground beef can survive without any substantial increase or decrease in viable cell population during refrigerated storage for 14 days.

Animals↗
PubMed2000

Substantial in vivo proliferation of CD4(+) and CD8(+) T lymphocytes during secondary Listeria monocytogenes infection.

In mice Listeria monocytogenes infection induces a strong T cell response. In an attempt to quantitatively analyze the magnitude and kinetics of the CD4(+) and CD8(+) T cell response during L. monocytogenes infection in vivo we used a T cell transfer system that is independent of in vitro cell culture techniques and information about the identity of immunogenic T cell epitopes. Our results demonstrate substantial expansion of the in vivo primed and transferred T cell populations in response to L. monocytogenes. At the peak of response, transferred T cells represented more than one third of the total CD4(+) and CD8(+) T cell populations in blood and spleen of recipient mice. After stimulation in vitro, 40 % of these CD4(+) T cells responded to heat-killed listeriae with the production of IFN-gamma. Thus, our results reveal that in addition to the large CD8(+) T cell population an almost equally large population of Listeria-reactive CD4(+) T cells is generated in response to L. monocytogenes infection.

Adoptive Transfer↗
PubMed2005

Consequences of the development of nisin-resistant Listeria monocytogenes in fermented dairy products.

Wild Listeria isolates representing serovars found in artisanal cheeses commercialized in Asturias (northern Spain) were assessed for their susceptibility to several bacteriocins. Pediocin PA-1 was the most active bacteriocin followed by enterocin AS-48, nisin, and plantaricin C. However, some Listeria monocytogenes and Listeria innocua strains were already highly resistant to PA-1. Among the wild L. monocytogenes populations, the frequency of development of nisin resistance ranged from 10(-6) up to 10(-3), depending on the strain. Highly stable mutants with increased nisin resistance (two- to fourfold) were isolated and tested for potential cross-resistance to lysozyme, EDTA, and various NaCl concentrations and pH values. All mutants were cross-resistant to lysozyme but sensitive to EDTA. In contrast, no clear correlation could be established between nisin resistance and an altered susceptibility to NaCl or pH changes. Nisin-resistant variants were able to survive and even to multiply in milk fermented by a nisin-producing Lactococcus, but the growth of the wild-type strain was inhibited. The different phenotypes evaluated in this study are indicative of the unpredictability of the consequences of the development of nisin resistance in a dairy environment. This resistance should be considered when making a risk assessment of the long-term use of nisin to control L. monocytogenes.

Anti-Bacterial Agents↗
PubMed2005

[Listeria monocytogenes in women of reproductive age].

OBJECTIVE: Listeria monocytogenes (LM) is gram-positive bacteria linear shaped which grows good also at refrigerator temperature (4 degrees C). The bacteria is resistant on high and low temperatures. This bacteria can be found in the dirt, rotted vegetation, vegetables and fruit, milk and dairy products, and also in the meat and processed meat. This bacteria cause disease called Listeriosis. This bacteria attacks at first people with weak immune system like infants, pregnant women, people with chronic diseases, people with HIV and people who are 60 and over. Pregnant women can transfer Listeria through the placenta, from mother to child and that can cause premature delivery, premature birth, early rupture of placenta or still born. GOAL: Find out if there is serological respond by female patients in the reproductive age who had spontaneous abortion and female patients in the reproductive age who never had the spontaneous abortion. By agglutination serologic method it had been researched if there is any antibody on Listeria monocytogenes. RESULTS: Two groups were included in testing: experimental and control group with a total of 60 patients. In experimental group there were 18 (60%) positive samples. In control group there were 8 (26.70%) positive samples. CONCLUSION: The results investigations have shown that there is serological respond to Listeria monocytogenes in the women of reproductive age. The number of positive patients was greater in women who had spontaneous abortion compared to women who never had the spontaneous abortion.

Abortion, Spontaneous↗
PubMed1994

Presence, detection and growth of Listeria monocytogenes in seafoods: a review.

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.

Bacteriological Techniques↗
PubMed1997

A gerbil model for rhombencephalitis due to Listeria monocytogenes.

Rhombencephalitis due to Listeria monocytogenes is a frequent complication of human listeriosis, inducing a high mortality and severe neurological sequelae despite antibiotic therapy. However, there is no animal model which consistently reproduces clinical rhombencephalitis. Here, we present a model of Listeria rhombencephalitis in gerbils. Animals were inoculated in the middle ears with a low infective dose of L. monocytogenes, thus creating prolonged otitis media with persistent bacteremia. Gerbils developed a severe rhombencephalitis with circling syndrome, paresia, ataxia, rolling movements. The invasion of the central nervous system was visualized on living animals by resonance magnetic imaging and characterized by bacterial growth in the brain, reaching about 10(7) bacteria in the rhombencephalum by day 12 of infection. The histological lesions were mainly located in the brainstem, and consisted in coalescent, necrotic abscesses with perivascular sheaths, mimicking those observed in human rhombencephalitis. Bacteria were detected by electronmicroscopy inside infectious foci, either free in necrotic material or inside inflammatory cells, mainly polymorphonuclear cells. This gerbil model of Listeria rhombencephalitis will be useful to study the molecular mechanisms allowing bacteria to cross the blood-brain barrier, and to evaluate the intracerebral efficacy of antibiotics.

Animals↗
PubMed1992

Spontaneous bacterial peritonitis caused by Listeria monocytogenes: two case reports and literature review.

Two new cases of spontaneous bacterial peritonitis (SBP) caused by Listeria monocytogenes are reported. Listeria monocytogenes was recovered from the ascitic fluid but not from the blood cultures of two adult diabetic inpatients with hepatic cirrhosis and SBP that had been treated empirically with cefotaxime. These two cases add to the 17 cases of Listeria monocytogenes SBP reported previously, stressing the relevance of this microorganism to this clinical condition. The recovery of Listeria monocytogenes from blood has been achieved in only half of the cases reported, suggesting the possibility of a direct translocation mechanism. Combinations of amino- or ureidopenicillins with beta-lactamase inhibitors or carbapenems might be more effective as empiric therapy of SBP in cirrhotic patients.

Aged↗
PubMed1990

Transferable plasmid-mediated antibiotic resistance in Listeria monocytogenes.

A strain of Listeria monocytogenes, isolated from a patient with meningoencephalitis, was resistant to chloramphenicol, erythromycin, streptomycin, and tetracycline. The genes conferring resistance to these antibiotics were carried by a 37-kb plasmid, pIP811, that was self-transferable to other L monocytogenes cells, to enterococci-streptococci, and to Staphylococcus aureus. The efficacy of transfer and the stability of pIP811 were higher in enterococci-streptococci than in the other gram-positive bacteria. As indicated by nucleic acid hybridisation, the genes in pIP811 conferring resistance to chloramphenicol, erythromycin, and streptomycin were closely related to plasmid-borne determinants that are common in enterococci-streptococci. Plasmid pIP811 shared extensive sequence homology with pAM beta 1, the prototype broad host range resistance plasmid in these two groups of gram-positive cocci. These results suggest that emergence of multiple antibiotic resistance in Listeria spp is due to acquisition of a replicon originating in enterococci-streptococci. The dissemination of resistance to other strains of L monocytogenes is likely.

Chloramphenicol Resistance↗