Molecular approaches to the identification of pathogenic and nonpathogenic listeriae.

The genus Listeria consists of a closely related group of Gram-positive bacteria that commonly occur in the environment and demonstrate varied pathogenic potential. Of the 10 species identified to date, L. monocytogenes is a facultative intracellular pathogen of both humans and animals, L.

Listeria monocytogenes serovar 4a is a possible evolutionary intermediate between L. monocytogenes serovars 1/2a and 4b and L. innocua.

The genus Listeria consists of six closely related species and forms three phylogenetic groups: L. monocytogenes- L. innocua, L.

Molecular characteristics and virulence potential of Listeria monocytogenes isolates from Chinese food systems.

In this study, we examined Listeria monocytogenes isolates from Chinese food sources in an attempt to gain further insights on the molecular characteristics and virulence potential of this important foodborne pathogen. Of the 88 L. monocytogenes food isolates recovered, 42 (47.

Listeria-based anti-infective vaccine strategies.

Listeria monocytogenes is a Gram-positive intracellular bacterium that has accounted for a significant proportion of human foodborne infections in recent decades. Although infection with sublethal level of L. monocytogenes generates enduring immunity, it is impractical to apply intact virulent strains as vaccine.

Preparation of Listeria monocytogenes specimens for molecular detection and identification.

Listeria monocytogenes is a common foodborne pathogen that has the capacity to cause severe clinical illness in vulnerable human population groups. The availability of rapid and specific laboratory tests to identify this bacterium is essential for preventing an otherwise easily treated malaise from developing into a life-threatening disease. To this end, a variety of rapid, sensitive and precise nucleic acid-based assays have been developed, contributing to the improved diagnosis of listeriosis.

A multiplex PCR for species- and virulence-specific determination of Listeria monocytogenes.

Listeria monocytogenes internalin gene inlJ has been described previously for differentiation of virulent from avirulent strains. However, a recent report indicated that there exist some unusual lineage IIIB strains (e.g.

Toward an improved laboratory definition of Listeria monocytogenes virulence.

Listeria monocytogenes is an opportunistic foodborne pathogen that encompasses a diversity of strains with varied virulence. The ability to rapidly determine the pathogenic potential of L. monocytogenes strains is integral to the control and prevention campaign against listeriosis.

Characteristics of cell-mediated, anti-listerial immunity induced by a naturally avirulent Listeria monocytogenes serotype 4a strain HCC23.

The characteristics of cell-mediated, anti-listerial immune response initiated by an avirulent Listeria monocytogenes serotype 4a strain HCC23 was assessed. Similar to virulent strain EGD, avirulent strain HCC23 grew readily within macrophage-like J774 cells, but nonhemolytic strain ATCC 15313 did not. Compared with EGD, HCC23 induced a relatively low level of gamma interferon (IFN-gamma) in mice, and ATCC 15313 stimulated no detectable IFN-gamma.

Listeria monocytogenes subgroups IIIA, IIIB, and IIIC delineate genetically distinct populations with varied pathogenic potential.

Listeria monocytogenes lineage III strains belonging to subgroups IIIA (n = 8), IIIB (n = 5), and IIIC (n = 6) were examined along with other known serotype strains (n = 11) by PCR and Southern hybridization using several recently described species-, virulence-, and serotype-specific primers and probes. The virulence of seven representative lineage III strains was then evaluated in mice via the intraperitoneal route. The results suggest that subgroup IIIA consists of typical rhamnose-positive avirulent serotype 4a and virulent serotype 4c strains, subgroup IIIC consists of atypical rhamnose-negative virulent serotype 4c strains, and subgroup IIIB consists of atypical rhamnose-negative virulent non-serotype 4a and non-serotype 4c strains, some of which may be related to serotype 7.

Identification, subtyping and virulence determination of Listeria monocytogenes, an important foodborne pathogen.

Listeria monocytogenes is an opportunistic intracellular pathogen that has become an important cause of human foodborne infections worldwide. Given its close relationship to other Listeria species and its tendency to produce non-specific clinical symptoms, the availability of rapid, sensitive and specific diagnostic tests for the differentiation of L. monocytogenes from other Listeria species is helpful for selecting appropriate treatment regimens.

PCR detection of pathogenic Leptospira genomospecies targeting putative transcriptional regulator genes.

The genus Leptospira comprises multiple genomospecies that demonstrate varied pathogenic potential. The availability of rapid and precise diagnostic procedures to differentiate pathogenic from nonpathogenic Leptospira spp. is therefore essential to prevent an otherwise easily treatable malaise from developing into a life-threatening disease.

Listeria monocytogenes serotype 4b strains belonging to lineages I and III possess distinct molecular features.

A collection of Listeria monocytogenes serotype 4b strains belonging to lineages I and III were examined by PCR and Southern blot analysis using species-, virulence-, and serotype-specific primers and probes. Whereas four serotype 4b lineage I strains reacted in PCR with the serotype 4b-, 4d-, and 4e-specific ORF2110 and virulence-specific lmo1134 and lmo2821 primers, all nine serotype 4b lineage III strains were negative by ORF2110 and lmo1134 primers. In addition, the nine serotype 4b lineage III strains formed two separate groups through their reactions in PCR with virulence-specific lmo2821 primers.

PCR amplification of a species-specific putative transcriptional regulator gene reveals the identity of Enterococcus faecalis.

Enterococcus faecalis, an opportunistic bacterial pathogen, has become prominent in recent decades due to its ability to develop resistance to various antibiotics. The ability to rapidly identify E. faecalis, followed by prompt treatment, is therefore vital for the control of this pathogen.

Rapid identification of Streptococcus pyogenes with PCR primers from a putative transcriptional regulator gene.

Streptococcus pyogenes (GAS) is a common bacterial pathogen that has emerged as an increasingly important health concern in many parts of the world. Although GAS may appear harmless in healthy individuals, the ability of this bacterium to take advantage of a weakened or compromised host defense system is extraordinary. Following the recent publication of the genome sequences of several S.

Isolation and PCR amplification of a species-specific oxidoreductase-coding gene region in Listeria grayi.

Listeria grayi is a nonpathogenic Gram-positive bacterium that demonstrates considerable similarities to other members in the genus Listeria, including the foodborne human pathogen Listeria monocytogenes and the animal pathogen Listeria ivanovii. A rapid diagnostic test to identify and diagnose listeriosis would be valuable, especially in cases where the presence of L. grayi may complicate diagnosis.

Comparative assessment of acid, alkali and salt tolerance in Listeria monocytogenes virulent and avirulent strains.

Listeria monocytogenes is an opportunistic bacterial pathogen of man and animals that has the capacity to survive under extreme environmental conditions. While our knowledge on L. monocytogenes and its ability to sustain within wide pH and temperature ranges and salt concentrations has been largely built on the virulent strains of this species, relatively little is known about avirulent strains in this regard.

Species-specific PCR determination of Listeria seeligeri.

Listeria seeligeri is a non-pathogenic bacterium coming under the genus Listeria. As this bacterium resembles other Listeria species such as L. monocytogenes and L.

Specific PCR identification of Pasteurella multocida based on putative transcriptional regulator genes.

Pasteurella multocida is an important animal pathogen that may also infect humans through animal bites and scratches. After comparison of transcriptional regulator gene sequences from the P. multocida genome with other DNA sequences at GenBank, we identified two genes (i.

PCR detection of a putative N-acetylmuramidase gene from Listeria ivanovii facilitates its rapid identification.

Listeria ivanovii is a Gram-positive bacterial pathogen that is capable of causing abortions and stillbirths in farm animals, particularly sheep and cattle. In terms of morphological, biochemical and molecular characteristics, L. ivanovii resembles other Listeria species such as L.

Listeria monocytogenes: comparative interpretation of mouse virulence assay.

Being an opportunistic bacterial pathogen, Listeria monocytogenes demonstrates significant strain variations in virulence and pathogenicity. The availability of laboratory procedures to ascertain the pathogenic potential of L. monocytogenes bacteria would greatly enhance the control and prevention of listerial infections.

Use of PCR primers derived from a putative transcriptional regulator gene for species-specific determination of Listeria monocytogenes.

Listeria monocytogenes is an opportunistic bacterial pathogen that has accounted for an important portion of human foodborne diseases worldwide. In this study, through comparative analysis of L. innocua and L.

Characterization of virulent and avirulent Listeria monocytogenes strains by PCR amplification of putative transcriptional regulator and internalin genes.

Listeria monocytogenes is an opportunistic bacterial pathogen that is an important cause of human food-borne illness worldwide. However, L. monocytogenes strains demonstrate considerable variation in pathogenic potential.

Identification of Listeria innocua by PCR targeting a putative transcriptional regulator gene.

Listeria innocua is a common, non-pathogenic bacterial species that shares morphological, biochemical and molecular characteristics with the pathogenic species L. monocytogenes. The presence of L.