Occurrence of toxigenic Vibrio parahaemolyticus strains in shrimp in Iran.

Vibrio parahaemolyticus, a common cause of foodborne gastroenteritis in people, is frequently isolated from a variety of seafood, including shrimp. The virulence of clinical V. parahaemolyticus strains is commonly associated with expression of thermostable direct hemolysin (TDH) and TDH-related hemolysin (TRH), which are encoded by the tdh and trh genes. This study was conducted to determine the prevalence rate of total and toxigenic V. parahaemolyticus in shrimp caught off the south coast of Iran. Three hundred freshly caught shrimp from four different species, Penaeus monodon, Penaeus semisulcatus, Penaeus indicus, and Penaeus merguiensis, were collected in three provinces along Persian Gulf in the south coast of Iran. Shrimp were collected at the end of each month from July 2008 to July 2009. The samples were analyzed for the presence of V. parahaemolyticus and the occurrence of toxigenic strains. Using conventional bacteriological techniques, 29 V. parahaemolyticus isolates were identified in which 28 strains were confirmed by a polymerase chain reaction assay targeting the tlh gene of V. parahaemolyticus. Using polymerase chain reaction assays targeting the tdh and trh genes, five (1.7%) and two (0.7%) isolates were tdh positive and trh positive, respectively. The tdh-positive isolates were commonly detected in summer, whereas no toxigenic strain was isolated in winter. To the best of our knowledge, the present study is the first report of the presence of toxigenic tdh- and trh-positive V. parahaemolyticus strains in the seafood in Iran.