Molecular characterizations of pathogenic Vibrio parahaemolyticus isolated from Southern Taiwan oyster-growing environment

Ninety-four virulent strains of Vibrio parahaemolyticus containing tdh and/or trh genes isolated from seawater, sediment, and oysters collected in Penghu, Tainan, and Changhua Lukang coastal water were characterized by analyses of O-group antigens, pulsed-field gel electrophoresis (PFGE) after digestion with SfiI enzyme, and randomly amplified polymorphic DNAs (RAPD). Analysis of virulence markers (tdh and trh) revealed that 60.6% of the isolates possessed only tdh, 13.8% of them possessed only trh, and 25.5% of them possessed both tdh and trh. Ten O-group serotypes (O1, O2, O3, O4, O5, O6, O7, O8, O10, and O11) were identified among the isolates with O1 group (28 isolates) being the most prevalent, followed by the O3 group (16 isolates) and O5 group (15 isolates). PFGE typing of the isolates revealed 94 patterns while RAPD analyses categorized the isolates into five major groups. Both PFGE and RAPD analyses showed high index of discrimination (DI) values. This study identified diverse serotypes and genotypes of virulent V. parahaemolyticus distributed in the oyster-growing environments, which can be used for risk assessment of V. parahaemolyticus infection associated with oyster consumption in Taiwan.