Molecular characterization of clinical and environmental Vibrio parahaemolyticus isolates in Taiwan

Vibrio parahaemolyticus is the most prevalent foodborne pathogen in Taiwan and it is frequently recovered from seafood. In this study, V. parahaemolyticus that was isolated in recent years from aquacultural environments and clinical specimens were comparatively analyzed by NotI-restricted pulsed-field gel electrophoresis (PFGE) and polymerase chain reaction, targeting common toxin genes (tdh, trh, ureC), MTase gene, toxR regulator, markers for pandemic strains (ORF8, group-specific toxRS) and representative genes of type three secretion systems T3SS1 (vcrD1, VP1680, vopD) and T3SS2α (vcrD2, vopD2, vopB2, vopP, vopC, vopT). Among the 48 clinical isolates and 93 environmental isolates that were analyzed by PFGE, a total of 26 and 76 pulsetypes were identified and grouped into six and nine clusters, respectively, at 80% similarity. The pandemic O3:K6 clones and other clinical and environmental isolates were further characterized according to the distribution of these examined target genes. The MTase gene and the vopB2, vopP, vopC and vopT genes of T3SS2α were present at a significantly higher frequency (>90%) in the pandemic clones than in other clinical isolates. The MTase gene and some other virulence-associated genes were also present in a few of the environmental isolates, and these results suggest the horizontal transfer of these genes in the clinical and environmental isolates of this species.