Dataset Information

Multi-virulence-locus sequence typing of Listeria monocytogenes.

ABSTRACT: A multi-virulence-locus sequence typing (MVLST) scheme was developed for subtyping Listeria monocytogenes, and the results obtained using this scheme were compared to those of pulsed-field gel electrophoresis (PFGE) and the published results of other typing methods, including ribotyping (RT) and multilocus sequence typing (MLST). A set of 28 strains (eight different serotypes and three known genetic lineages) of L. monocytogenes was selected from a strain collection (n > 1,000 strains) to represent the genetic diversity of this species. Internal fragments (ca. 418 to 469 bp) of three virulence genes (prfA, inlB, and inlC) and three virulence-associated genes (dal, lisR, and clpP) were sequenced and analyzed. Multiple DNA sequence alignment identified 10 (prfA), 19 (inlB), 13 (dal), 10 (lisR), 17 (inlC), and 16 (clpP) allelic types and a total of 28 unique sequence types. Comparison of MVLST with automated EcoRI-RT and PFGE with ApaI enzymatic digestion showed that MVLST was able to differentiate strains that were indistinguishable by RT (13 ribotypes; discrimination index = 0.921) or PFGE (22 profiles; discrimination index = 0.970). Comparison of MVLST with housekeeping-gene-based MLST analysis showed that MVLST provided higher discriminatory power for serotype 1/2a and 4b strains than MLST. Cluster analysis based on the intragenic sequences of the selected virulence genes indicated a strain phylogeny closely related to serotypes and genetic lineages. In conclusion, MVLST may improve the discriminatory power of MLST and provide a convenient tool for studying the local epidemiology of L. monocytogenes.

SUBMITTER: Zhang W

PROVIDER: S-EPMC348834 | biostudies-literature | 2004 Feb

REPOSITORIES: biostudies-literature

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Multi-virulence-locus sequence typing of Listeria monocytogenes.

Zhang Wei W Jayarao Bhushan M BM Knabel Stephen J SJ

Applied and environmental microbiology 20040201 2

A multi-virulence-locus sequence typing (MVLST) scheme was developed for subtyping Listeria monocytogenes, and the results obtained using this scheme were compared to those of pulsed-field gel electrophoresis (PFGE) and the published results of other typing methods, including ribotyping (RT) and multilocus sequence typing (MLST). A set of 28 strains (eight different serotypes and three known genetic lineages) of L. monocytogenes was selected from a strain collection (n > 1,000 strains) to repres ...[more]

PMID: 14766571

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Project description:The beta-glucoside cellobiose has been reported to specifically repress the PrfA-dependent virulence genes hly and plcA in Listeria monocytogenes NCTC 7973. This led to the hypothesis that beta-glucosides, sugars of plant origin, may act as signal molecules, preventing the expression of virulence genes if L. monocytogenes is living in its natural habitat (soil). In three other laboratory strains (EGD, L028, and 10403S), however, the effect of cellobiose was not unique, and all fermentable carbohydrates repressed hly. This suggested that the downregulation of virulence genes by beta-glucosides is not a specific phenomenon but, rather, an aspect of a global regulatory mechanism of catabolite repression (CR). We assessed the effect of carbohydrates on virulence gene expression in a panel of wild-type isolates of L. monocytogenes by using the PrfA-dependent phospholipase C gene plcB as a reporter. Utilization of any fermentable sugar caused plcB repression in wild-type L. monocytogenes. However, an EGD variant was identified in which, as in NCTC 7973, plcB was only repressed by beta-glucosides. Thus, the regulation of L. monocytogenes virulence genes by sugars appears to be mediated by two separate mechanisms, one presumably involving a CR pathway and another specifically responding to beta-glucosides. We have identified in L. monocytogenes a 4-kb operon, bvrABC, encoding an antiterminator of the BglG family (bvrA), a beta-glucoside-specific enzyme II permease component of the phosphoenolpyruvate-sugar phosphotransferase system (bvrB), and a putative ADP-ribosylglycohydrolase (bvrC). Low-stringency Southern blots showed that this locus is absent from other Listeria spp. Transcription of bvrB was induced by cellobiose and salicin but not by arbutin. Disruption of the bvr operon by replacing part of bvrAB with an interposon abolished the repression by cellobiose and salicin but not that by arbutin. Our data indicate that the bvr locus encodes a beta-glucoside-specific sensor that mediates virulence gene repression upon detection of cellobiose and salicin. Bvr is the first sensory system found in L. monocytogenes that is involved in environmental regulation of virulence genes.

Dataset Information

Multi-virulence-locus sequence typing of Listeria monocytogenes.

Publications

Multi-virulence-locus sequence typing of Listeria monocytogenes.

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