Distribution, serological and molecular characterization of Vibrio parahaemolyticus from shellfish in the eastern coast of China

To investigate the prevalence of Vibrio parahaemolyticus in shellfish, a total of 288 samples from retail markets in four coastal provinces of eastern China were collected and analyzed monthly from December 2008 to November 2009. Altogether 172 isolates were isolated and identified, of which 2 isolates were tdh+ and 5 were trh+. The levels of V. parahaemolyticus were estimated by most probable number procedure and results suggested that the distribution of V. parahaemolyticus was disparity in season. Serotyping was performed among all isolates, 157 isolates were grouped into 9 O-groups and 42 isolates were determined by specific K-typing. Two tdh+ isolates were identified as O3:K6 and O4:K68 serovars. Random amplified polymorphic DNA (RAPD) was performed to assess the genetic diversity of all isolates. The results showed that there were 73 different patterns, which were clustered into 18 groups except 6 miscellaneous patterns. The two tdh+ isolates and two clinical isolates were grouped into the same cluster. This study demonstrated that V. parahaemolyticus from shellfishes were of high antigenic and genetic diversity. Comparison with serological method, RAPD might be a more efficient vehicle for epidemiology and risk assessment of V. parahaemolyticus.