Investigation of diversity of Vibrio parahaemolyticus in molluscs

Objective To understand the serotypes of Vibrio parahaemolyticus in mollusks. Methods Molluscs samples were treated according to GB/T 4789.7. Ten V. parahaemolyticus colonies were picked up from each positive sample and their serotypes were detected. PCR was conducted to detect tdh, trh, GS-PCR and phage f237. Results In 75 molluscs samples, 24.0% were contaminated with V. parahaemolyticus, and 5.6% of V. parahaemolyticus strains were trh positive, no tdh positive strains were detected. A total of 180 colonies of V. parahaemolyticus were obtained from 18 positive molluscs samples, which could be classified into 42 serotypes. Three O3:K6 strain and 1 O1:K33 strain were detected, but they didn't belonged to circulating strain. The serotype number varied with samples, the highest was 9 and the average was 6.1. Variants of phage f237 with orf8 complete deletion were detected in 47 (26.1%) colonies. Conclusion Variant of phage f237 with orf8 complete deletion was widely distributed in molluscs. Molluscs is naturally contaminated with multiple types of V. parahaemolyticus. V. parahaemolyticus detected in human are rare in food, so it is necessary to conduct serotyping and genotyping in V. parahaemolyticus detection in food samples.