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Allele distribution and genetic diversity of VNTR loci in Salmonella enterica serotype Enteritidis isolates from different sources.

ABSTRACT: Salmonella enterica serotype Enteritidis (S. Enteritidis) is a zoonotic pathogen, which can be found in many sources including animals and the environment. However, little is known about the molecular relatedness among S. Enteritidis isolates from different sources. We have applied multiple-locus variable number tandem repeat analysis (MLVA) to study the genetic diversity of S. Enteritidis isolates from human and non-human sources.We identified 38 unique MLVA types using nine VNTR loci markers for discrimination between 145 S. Enteritidis isolates from different sources including humans (n = 41), chickens (n = 45), and eggs (n = 40). There were 20 distinct MLVA types identified from human isolates, 17 distinct MLVA types from chicken isolates, and 5 from egg isolates. We compared allele distribution and frequency for each VNTR marker and measured allelic polymorphism within each VNTR locus of S. Enteritidis isolates from the sources using Nei's diversity index (D). Differences in allele distribution and frequency were detected in most loci of study isolates. Different genetic diversity for certain loci was identified in isolates from different sources. The average of genetic diversity (D) was lower in egg isolates (0.16) compared to human (0.41) and chicken (0.30). However, for loci SE3, SE7, and SE9, human isolates showed significantly higher diversity than both chicken and egg isolates. Whereas for loci SE5 and SE10, chicken isolates had significantly higher diversity than both human and egg isolates. Minimum-spanning tree (MST) comprised one major cluster, a minor cluster, and four clonal expansions. MLVA application enabled a cluster analysis by the MST of the S. Enteritidis isolates by sources, which allows a great insight into the genetic relatedness and the possible flow of these organisms between different reservoirs and humans.Differences in allele distribution and genetic diversity of VNTR loci in S. Enteritidis isolates from different sources were found. Polymorphism in most of the VNTR loci was more frequent among human S. Enteritidis isolates than isolates from chickens or eggs. Therefore, VNTR profiles of S. Enteritidis isolates from a specific source should be further evaluated as potential markers in epidemiologic investigations to trace S. Enteritidis to their probable source.

SUBMITTER: Cho S

PROVIDER: S-EPMC2561042 | biostudies-literature | 2008 Sep

REPOSITORIES: biostudies-literature

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Allele distribution and genetic diversity of VNTR loci in Salmonella enterica serotype Enteritidis isolates from different sources.

Cho Seongbeom S Whittam Thomas S TS Boxrud David J DJ Bartkus Joanne M JM Saeed A Mahdi AM

BMC microbiology 20080915

<h4>Background</h4>Salmonella enterica serotype Enteritidis (S. Enteritidis) is a zoonotic pathogen, which can be found in many sources including animals and the environment. However, little is known about the molecular relatedness among S. Enteritidis isolates from different sources. We have applied multiple-locus variable number tandem repeat analysis (MLVA) to study the genetic diversity of S. Enteritidis isolates from human and non-human sources.<h4>Results</h4>We identified 38 unique MLVA t ...[more]

PMID: 18793420

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Project description:Salmonella enterica serovar Enteritidis (S. Enteritidis) has caused major epidemics of gastrointestinal infection in many different countries. In this study we investigate genome divergence and pathogenic potential in S. Enteritidis isolated before, during and after an epidemic in Uruguay.266 S. Enteritidis isolates were genotyped using RAPD-PCR and a selection were subjected to PFGE analysis. From these, 29 isolates spanning different periods, genetic profiles and sources of isolation were assayed for their ability to infect human epithelial cells and subjected to comparative genomic hybridization using a Salmonella pan-array and the sequenced strain S. Enteritidis PT4 P125109 as reference. Six other isolates from distant countries were included as external comparators.Two hundred and thirty three chromosomal genes as well as the virulence plasmid were found as variable among S. Enteritidis isolates. Ten out of the 16 chromosomal regions that varied between different isolates correspond to phage-like regions. The 2 oldest pre-epidemic isolates lack phage SE20 and harbour other phage encoded genes that are absent in the sequenced strain. Besides variation in prophage, we found variation in genes involved in metabolism and bacterial fitness. Five epidemic strains lack the complete Salmonella virulence plasmid. Significantly, strains with indistinguishable genetic patterns still showed major differences in their ability to infect epithelial cells, indicating that the approach used was insufficient to detect the genetic basis of this differential behaviour.The recent epidemic of S. Enteritidis infection in Uruguay has been driven by the introduction of closely related strains of phage type 4 lineage. Our results confirm previous reports demonstrating a high degree of genetic homogeneity among S. Enteritidis isolates. However, 10 of the regions of variability described here are for the first time reported as being variable in S. Enteritidis. In particular, the oldest pre-epidemic isolates carry phage-associated genetic regions not previously reported in S. Enteritidis. Overall, our results support the view that phages play a crucial role in the generation of genetic diversity in S. Enteritidis and that phage SE20 may be a key marker for the emergence of particular isolates capable of causing epidemics.

Dataset Information

Allele distribution and genetic diversity of VNTR loci in Salmonella enterica serotype Enteritidis isolates from different sources.

Publications

Allele distribution and genetic diversity of VNTR loci in Salmonella enterica serotype Enteritidis isolates from different sources.

Similar Datasets

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