PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “LISTERIA MONOCYTOGENES”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7Linked to original sources
PubMed1969

Specificity of Acquired Resistance Produced by Immunization with Listeria monocytogenes and Listeria Fractions.

Mice were immunized with 1.0 mg of an attenuated strain of Listeria monocytogenes to determine the period of protection afforded by this strain when the mice were challenged intravenously with 5 MLD of listeria. Protection appeared 2 days after immunization and was still apparent 4 weeks after immunization. If the challenge dose was decreased to 1 MLD, protection was apparent at 10 weeks. Mice immunized with a comparable dose of mycobacterial cells and challenged intravenously with 1 MLD of listeria showed no protection at 10 weeks. The magnitude of the immune response to listeria challenge was not increased in mice immunized with the same virulent strain as that used for challenge. It was also found that resistance to listeria challenge appeared early after listeria immunization if the immunizing dose was large. As the immunizing dose was decreased and the challenge dose increased, resistance appeared later. Listeria killed by heat or ultraviolet irradiation, living but nonmultiplying streptomycin-dependent listeria, or listeria ribosomal fraction gave no protection against listeria challenge. The magnitude of the immune responses after listeria immunization to listeria challenge and to mycobacteria challenge were compared. It was found that protection after listeria challenge was of longer duration. In addition, a 100-fold larger vaccinating dose was required to give comparable protection against tuberculous infection.

Journal Article↗
PubMed1993

A proposed nonpathogenic biological indicator for thermal inactivation of Listeria monocytogenes.

Listeria innocua M1 was developed as a thermal processing indicator organism for L. monocytogenes by selection of a rifampin- and streptomycin-resistant mutant. zetaD values were 5.6 and 5.8 degrees C, and D (68 degrees C) values were 3.8 and 4.9 s for L. monocytogenes and L. innocua, respectively, in skim milk. The advantages of easy selection, similar heat resistance, and nonpathogenicity make L. innocua M1 appropriate for challenge studies designed to evaluate process lethality with respect to L. monocytogenes.

Animals↗
PubMed1995

Evaluation of enrichment broths for their ability to recover heat-injured Listeria monocytogenes.

Listeria selective enrichment broth (LEB), University of Vermont (UVM) broth, modified UVM (MUVM) broth and Fraser broth (FB) were compared for their ability to recover cells of L. monocytogenes from heated tryptose phosphate broth. Three strains of L. monocytogenes were heated at 54 degrees C for 30 min, inoculated into enrichment broths supplemented with 400 micrograms catalase ml-1, and incubated for 8 h at 30 degrees C. After incubation for 4 h, the total viable cell populations either decreased or did not change, whereas the number of healthy (non-injured) cells of all strains increased significantly in all broths except FB inoculated with the LCDC strain. With an increase in incubation time to 8 h, the number of healthy cells of all strains increased in all broths. At 8 h, the difference between populations of total (injured plus healthy cells) and healthy cells detected in LEB inoculated with two strains was not significant. Overall, recovery of heat-treated cells was significantly higher in LEB, followed by MUVM broth, UVM broth and FB. The addition of catalase to enrichment broths significantly enhanced recovery of heat-injured cells. A slight reduction of catalase activity of heated cells of all test strains in all enrichment broths except FB was observed by extending the incubation period from 4 to 8 h. A test strain that produces relatively higher catalase activity compared to the other strains exhibited the greatest resistance to exogenous hydrogen peroxide. Enumeration of viable L. monocytogenes cells in heated foods should be done using LEB supplemented with 400 micrograms catalase ml-1 to maximize the recovery of injured cells.

Catalase↗
PubMed2004

Carrier status for Listeria monocytogenes and other Listeria species in free range farm and market healthy indigenous chickens and ducks.

BACKGROUND: Listeria organisms are documented to be zoonotic; one of the sources of infection is the domestic fowl where it could occur as in apparent infection. The carriage of Listeria monocytogenes and other Listeria in indigenous birds has not been documented in Kenya. OBJECTIVE: To establish whether healthy looking indigenous chickens and ducks could be carriers of Listeria monocytogenes and other Listeria species. DESIGN: Field survey of indigenous chickens and ducks in three districts of Kenya. SETTING: Embakasi and Dagoreti divisions in Nairobi district; Athi river division in Machakos district; and Ngong division in Kajiado district, in Kenya. SUBJECTS: One hundred and thirty six indigenous chickens and 39 ducks reared under free range scavenging system in Nairobi, Machakos and Kajiado districts, in Kenya, were sampled. METHODS: In surveying the birds, the cloacal and pharyngeal swabs were taken from each bird separately using sterile cotton--tipped applicator swabs. The swabs in saline were transported in a coolbox to the laboratory for bacterial isolation and characterization. INTERVENTIONS: None (only compared farmed and the traded birds). MAIN OUTCOME MEASURES: Isolation of Listeria species and pathogenicity of Listeria isolates. RESULTS: Two Listeria monocytogenes and seven other Listeria species were recovered from the oropharyngeal swab samples of farm and market chickens but none from respective cloacal swabs. No Listeria was recovered from either oropharyngeal or cloacal swabs of farmed duck and slaughter chickens. Traded chickens yielded more Listeria isolates as compared to farmed chickens. CONCLUSION: This study shows that indigenous chickens in Kenya are carriers of Listeria monocytogenes and other Listeria species.

Animals↗
PubMed2002

Comparison of the cell surface properties and growth characteristics of Listeria monocytogenes and Listeria innocua.

Growth kinetics and physicochemical surface properties were compared for three Listeria strains with differing degrees of virulence: L. monocytogenes LO28; its isogenic, nonhemolytic mutant L. monocytogenes Bof415; and a nonvirulent species, L. innocua (strain Lin9). The influences of growth stage (mid-exponential phase, early stationary phase, and mid-stationary phase) and culture temperature (20 and 37 degrees C) were assessed by determining the electrical properties and the hydrophobic-hydrophilic and Lewis acid-base characteristics of the three strains. L. innocua, although taxonomically very similar to L. monocytogenes, exhibited physicochemical surface properties that differed significantly from those of L. monocytogenes LO28 and L. monocytogenes Bof415. Indeed, under our experimental conditions, L. innocua cells presented a more marked electronegative character (particularly when cultured at 20 degrees C), as well as greater variability in their Lewis acid-base characteristics as a function of temperature and growth stage. Furthermore, the growth kinetics of the three strains revealed the onset of a decay phase after 16 h of culture at 37 degrees C for the L monocytogenes Bof415 mutant. All of these results demonstrate that under our experimental conditions, the growth and/or physicochemical characteristics of the slightly pathogenic or nonpathogenic Listeria strains (Bof415 and Lin9) differed from those of the virulent strain (L. monocytogenes LO28). Consequently, the use of Listeria strains recognized as nonvirulent appeared to provide a model that was not fully suitable for simulating the bioadhesive behavior of the pathogenic strains involved in foodborne diseases.

Bacterial Adhesion↗
PubMed1994

Protein tyrosine kinase inhibitors block the entries of Listeria monocytogenes and Listeria ivanovii into epithelial cells.

The internalization of Listeria by intestinal epithelial cells is still poorly understood, however it is becoming apparent that microorganisms have developed the ability to interact with host cell receptor molecules to induce their own internalization. In this report we show that inhibition of cell tyrosine phosphorylation by protein tyrosine kinase (PTK) inhibitors blocks L. monocytogenes entry into both finite and immortalized intestinal cell lines. Some differences were observed between the Listeria species. L. monocytogenes entry was inhibited by between 10- to 100-fold by PTK inhibitors competing with the tyrosine residue binding of the kinase as erbstatin or by PTK inhibitors competing with the binding of ATP to the enzyme as genistein and some tyrphostins. On the other hand, L. ivanovii entry was inhibited by erbstatin as observed with L. monocytogenes but poorly by genistein and tyrphostins. The use of these several PTK inhibitors shows that even though both L. monocytogenes and L. ivanovii entered intestinal and other cell lines by stimulating PTK, it seems that L. monocytogenes stimulated a different PTK than L. ivanovii. According to the fact that the number of PTK receptors increases on immortalized cells, the higher L. monocytogenes internalization observed with immortalized cell lines could be related to a higher PTK receptor number on these cells compared to finite cell lines.

Animals↗
PubMed2000

Evaluation of a monoclonal antibody able to detect live Listeria monocytogenes and Listeria innocua.

A monoclonal Listeria antibody, designated B4, was evaluated. The ability of the antibody to bind to viable bacteria belonging to Listeria spp. compared to bacteria of the same species killed by heat treatment, acid or base treatment, sanitizers, and irradiation was examined. The antibody was found to react with viable L. monocytogenes and L. innocua, but not with heat-killed (72 degrees C, 5 min) strains of these organisms. When L. monocytogenes and L. innocua were killed by methods other than heat treatment, it was ambiguous whether the antibody detected the organism or not. It was concluded that the B4 antibody has potential to be used in an immuno capture step to capture live L. monocytogenes and L. innocua from foods prior to identification of L. monocytogenes by polymerase chain reaction (PCR).

Antibodies, Monoclonal↗
PubMed1995

[Phosphatidylinositol specific phospholipase C (PI-PLC) in differentiation of Listeria monocytogenes and Listeria innocua].

Listeria strains were investigated as regard: the production of PI-PLC and lecytinase, haemolytic and CAMP activity survival in mouse tissues. Although all the examined L. monocytogenes strains produced PI-PLC, they showed a very different activity of this enzyme. It was surprising that one of the four L. innocua strains demonstrated a weak activity of PI-PLC. L. monocytogenes bacteria with strong PI-PLC activity survived in mouse spleens for a much longer period of time than L. monocytogenes microbes with only a weak production of this enzyme. However, L. innocua bacteria producing some PI-PLC were quickly eliminated by infected mice.

Animals↗
PubMed1992

DNA sequence heterogeneity in the gene encoding a 60-kilodalton extracellular protein of Listeria monocytogenes and other Listeria species.

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

Bacterial Proteins↗
PubMedDate not supplied

Assurance polyclonal enzyme immunoassay for detection of Listeria monocytogenes and related Listeria species in selected foods: collaborative study.

Six foods representing a variety of food products were analyzed by the Assurance Listeria polyclonal enzyme immunoassay (EIA) and by either the Bacteriological Analytical Manual or the U.S. Department of Agriculture culture method for detecting Listeria monocytogenes and related Listeria species. Samples of each food type, at each inoculation level, were analyzed simultaneously by both methods. A total of 19 laboratories representing federal government agencies and private industry in the United States and Canada participated. Food types were inoculated with Listeria species including L. monocytogenes, with the exception of 3 lots of green beans, which were naturally contaminated. During this study, 1764 samples and controls were analyzed and confirmed, of which 492 were positive and 947 were negative by both methods. There were 159 samples that were positive by culture method but negative by the EIA and 188 that were negative by culture method but positive by EIA. Twenty-two samples were negative by EIA and by culture method but confirmed positive when Assurance selective enrichment broths were subcultured to selective agar. The Assurance polyclonal EIA for detecting L. monocytogenes and related Listeria species in foods has been adopted first action by AOAC INTERNATIONAL.

Animals↗
PubMedDate not supplied

Visual immunoprecipitate assay (VIP) for Listeria monocytogenes and related Listeria species detection in selected foods: collaborative study.

Six foods representing a variety of food products were analyzed by the Visual Immunoprecipitate Assay (VIP) and either the Bacteriological Analytical Manual (BAM) or the U.S. Department of Agriculture culture methods for detection of Listeria monocytogenes and related Listeria spp. Samples of each food type at each inoculation level were simultaneously analyzed by both methods. A total of 23 laboratories representing federal agencies and private industry in the United States and Canada participated in this collaborative study. Foods were inoculated with Listeria species including L. monocytogenes, with the exception of 3 lots of green beans that were naturally contaminated. During this study, 1509 samples and controls were analyzed and confirmed, of which 370 were positive and 921 were negative by both methods. One hundred and fifteen samples were positive by culture methods but negative by VIP. One hundred and thirty-two were negative by culture methods but positive by the VIP. Twenty-nine samples were negative by VIP and by culture methods but confirmed positive when VIP selective enrichment broths were subcultured to selective agars. The VIP method for detection of L. monocytogenes and related Listeria spp. in foods has been adopted first action by AOAC INTERNATIONAL.

Animals↗
PubMed1996

Occurrence of Listeria monocytogenes and other Listeria spp. in raw caprine milk.

Samples of caprine milk from bulk tanks of 405 farms in central Spain were analyzed for Listeria spp. once per season over a 1-yr period. Listeria monocytogenes and Listeria innocua were detected in 2.56 and 1.73% of the 1445 samples, respectively. Listeria ivanovii (0.21% samples) and Listeria seeligeri (0.07% samples) were rarely isolated. Only 6 milk samples were contaminated by more than one Listeria species. Most farms (92.59%) produced milk that was apparently free from L. monocytogenes throughout the sampling period, and 88.40% produced milk that was apparently free from Listeria spp. Milk contamination by Listeria spp. was seasonal; incidence in autumn (9.33%) and winter (5.14%) samples was higher than incidence in spring (0.85%) and summer (0.85%) samples. Occurrence of Listeria spp. was lower in samples from mountain farms (1.25%) than in samples from plateau farms (7.03%).

Animals↗
PubMedDate not supplied

Method extension study to validate applicability of AOAC Official Method 996.14 Assurance polyclonal enzyme immunoassay for detection of Listeria monocytogenes and related Listeria spp. from environmental surfaces: collaborative study.

Test portions from 3 environmental surface types, representative of typical surfaces found in a food production facility, were analyzed by the Assurance Listeria Polyclonal Enzyme Immunoassay (EIA) and the U.S. Department of Agriculture/Food Safety and Inspection Service (USDA/FSIS) culture method for Listeria monocytogenes and related Listeria species. In all cases, naturally contaminated environmental test samples were collected from an actual food production facility by sponge or swab. Test samples from concrete surfaces were collected by both swab and sponge; sponge test samples were collected from rubber surfaces, and swabs were used to sample steel surfaces. Test portions from each surface type were simultaneously analyzed by both methods. A total of 23 collaborators, representing government agencies, as well as private industry in both the United States and Canada, participated in the study. During this study, a total of 550 test portions and controls was analyzed and confirmed, of which 207 were positive and 336 were negative by both methods. Six test portions were positive by culture, but negative by the EIA. Three test portions were negative by culture, but positive by the EIA. Two test portions were negative by EIA and by culture, but confirmed positive when EIA enrichment broths were subcultured to selective agars. The data reported here indicate that the Assurance Listeria EIA method and the USDA/FSIS culture method are statistically equivalent for detection of L. monocytogenes and related Listeria species from environmental surfaces taken by sponges or swabs.

Bacteriological Techniques↗