Purpose: The aim of this study was to profile the presence of V. parahaemolyticus in seafood obtained from the market in Shanghai, China, identify the seafood item most susceptible to contamination of V. parahaemolyticus, and determine whether the post-harvest handling affecting the prevalence and levels of this pathogen.
Methods: Seafood samples (shrimp, crab, scallop, oyster, and mussel) were collected at sea wharf and retail stores in Shanghai from July to December of 2015. Each sample (25 g) was incubated at 37°C for 8 h for most probable number analysis. V. parahaemolyticus was identified by streaking samples from MPN tubes on thiosulfate-citrate-bile salts-sucrose agar, followed by on CHROMagar Vibrio agar, and confirmed with real-time RT-PCR targeting three hemolytic genes, tlh, tdh and trh.
Results: A total of 35 samples were collected at sea wharf and 32 samples tested positive for V. parahaemolyticus (prevalence rate of 91.4%) with levels as high as 2.2 log CFU/g, whereas the prevalence rate was 95.8% (91/95) with levels as high as 3.4 log CFU/g for samples collected at the marketplace. Among the variety of seafood, shrimp had the highest prevalence rate and level of V. parahaemolyticus. The highest prevalence rate was 100% in samples collected in August, which was the warmest month in Shanghai area. Results show that shrimps are of a particular concern of V. parahaemolyticus contamination and the post-harvest practices increase the prevalence rate and level of V. parahaemolyticus in seafood marketed in Shanghai.
Significance: The finding suggests that improved post-harvest hygiene practices and proper refrigeration are critical in reducing V. parahaemolyticus hazards in seafood.