Abstract
The genetic diversity and population structure of Vibrio vulnificus isolates from Korea and Taiwan were investigated using PCR-based assays targeting putative virulence-related genes and multilocus sequence typing (MLST). BOX-PCR genomic fingerprinting identified 52 unique genotypes in 84 environmental and clinical V. vulnificus isolates. The majority (> 50%) of strains had pathogenic genotypes for all loci tested; moreover, many environmental strains had pathogenic genotypes. Although significant (p < 0.05) inter-relationships among the genotypes were observed, the association between genotype and strain source (environmental or clinical) was not significant, indicating that genotypic characteristics alone are not sufficient to predict the isolation source or the virulence of a given V. vulnificus strain and vice versa. MLST revealed 23–35 allelic types per locus analyzed, resulting in a total of 44 unique sequence types (STs). Two major monophyletic groups (lineages A and B) corresponding to the two known lineages of V. vulnificus were observed; lineage A had six STs that were exclusively environmental, whereas lineage B had STs from both environmental and clinical sources. Pathogenic and nonpathogenic genotypes predominated in MLST lineages B and A, respectively. In addition, V. vulnificus was shown to be in linkage disequilibrium (p < 0.05), although two different recombination tests (PHI and Sawyer’s tests) detected significant evidence of recombination. Tajima’s D test also indicated that V. vulnificus might be comprised of recently sub-divided lineages. These results suggested that the two lineages revealed by MLST correspond to two distinct ecotypes of V. vulnificus.
Highlights
Vibrio vulnificus is a halophilic, Gram-negative, curved, rod-shaped bacterium frequently found in marine environments as well as in molluscan shellfish as part of the normal microflora [1,2,3]
Biotype 3 strains have been reported to cause wound infection in Genetic Diversity of Vibrio vulnificus humans, to date these infections have been limited to persons handling fish in Israel at freshwater fish farming sites [66, 99]
We hypothesize that the clonal population structure of VV, which comprised sequence types (STs) with some recombination potential, may be influenced by ecological factors that restrict the breakdown of linkage disequilibrium
Summary
Vibrio vulnificus is a halophilic, Gram-negative, curved, rod-shaped bacterium frequently found in marine environments (e.g., estuarine and coastal waters) as well as in molluscan shellfish (e.g., oysters and clams) as part of the normal microflora [1,2,3]. V. vulnificus is an important human pathogen, infection by which mainly occurs through the consumption of contaminated seafood and occasionally through open wounds exposed to contaminated.
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