Genetic Diversity ofVibrio parahaemolyticusfrom Narragansett Bay and Coastal Ponds of Rhode Island

Abstract

Quantitative polymerase chain reaction studies have detected Vibrioparahaemolyticus virulence genes (hemolysins tdh and trh) in Rhode Island oysters and waters. Illness caused by V. parahaemolyticus is currently rare in Rhode Island; however, there is concern over increasing aquaculture and water temperatures. The aim of this study was to characterize further the genetic diversity of V. parahaemolyticus in Rhode Island to determine disease risk. The genetic profile of pathogenic (tdh and/or trh ) strains and environmental (tdh-/trh-) strains of V. parahaemolyticus isolated from Rhode Island oyster and water samples was compared with pandemic and clinical strains using repetitive extragenic palindromic polymerase chain reaction. Of the 291 V. parahaemolyticus colonies isolated, 27 were pathogenic strains, with 25 of 291 (9.0%), tdh-/trh ; 1 of 291 (0.3%), tdh /trh ; and 1 of 291 (0.3%), tdh /trh-. Rhode Island isolates did not cluster closely with pandemic or clinical strains. Isolates containing tdh and/or trh genes from Rhode Island waters were predominantly tdh-/trh , in contrast with a predominance of tdh /trh- or tdh /trh strains in Alaska, the Pacific Northwest, and the Gulf of Mexico. Similar to other studies in the United States, a high level of genetic diversity in pathogenic and environmental strains of V. parahaemolyticus was seen. This study clarified the diversity and virulence gene content (tdh and trh status) of V. parahaemolyticus isolates from Rhode Island waters.