Detection and differentiation of V ibrio vulnificus and V . sinaloensis in water and oysters of a G ulf of M exico estuary

Summary V ibrio vulnificus is a potentially lethal human pathogen that occurs naturally in estuarine waters and shellfish. V ibrio vulnificus was quantified in water and oysters from F lorida's G ulf C oast by plating on mCPC agar, enrichment and plating, and quantitative PCR ( qPCR ). V ibrio vulnificus was detected in 19%, 29%, and 97% of samples respectively by direct plating, qPCR , and enrichment. Only 8% of typical colonies from direct plating were confirmed by PCR for vvhA ; others yielded no or atypically sized amplicons. Sequencing of the 16 S rDNA of 16 vvhA ‐ negative isolates with colony morphology typical of V . vulnificus identified 75% as V . sinaloensis. In vitro growth curves showed that V . sinaloensis grew more rapidly than V . vulnificus in seawater at temperatures ≤ 30°C. In contrast, the growth rate of V . vulnificus in alkaline peptone water was greater than that of V . sinaloensis , suggesting that these species can outcompete one another under conditions that are relevant to environmental parameters or regulatory monitoring regimes respectively. The virulence potential and ecology of V . sinaloensis are poorly understood; however, its phenotypic resemblance to V . vulnificus and the possibility that it could outcompete the pathogen in warm, estuarine waters argue for the need for a better understanding of this newly described V ibrio species.