Serotyping for Clinical Vibrio Parahaemolyticus Isolates and Analysis of Their Virulence Genes

Vibrio parahaemolyticus is one of the most important foodborne pathogens in China. Fish and shellfish are the main vehicles for the transmission of this pathogen. In recent years, foodborne outbreaks have significantly increased, which were resulted from V. parahaemolyticus associated with consumption of raw or undercooked shellfish, contaminated food. The clinical V. parahaemolyticus isolates(n=158), which came from Pudong, Jinshan, zhoushan and Ningbo in 2006-2009, were serotyped with 11 O antibodies and 8 K antibodies. In addition, the virulence-related genes of all isolates were analyzed, including tdh(Thermostable direct hemolysin) and trh(Thermostable direct hemolysin-related haemolysin). The results showed that those isolates could be divided into 22 serotypes. V. parahaemolyticus O3:K6 isolates were the epidemic strains(107/158). Other serotypes of these isolates were O1:K6, O3:K68, O1:K25, O1:K56, O2:K3, and so on. V. parahaemolyticus isolates from Jinshan were the most diversity. On the other hand, those from Zhoushan were the most unitary. The analysis results of their virulence genes demonstrated that most strains contained tdh gene (153/158) and trh gene (6/158). Six out of 158 isolates were both (tdh+/trh+), 147 were(tdh+/trh-), and 5 were (tdh-/trh-). In conclusion, almost all clinical isolates contained the pathogenic genes. The strains isolated from the four places present the diversity of serotypes and V. parahaemolyticus O3:K6 was epidemic serotype of these isolates.