ObjectiveTo investigate and characterize the contamination of Vibrio parahaemolyticus(V.parahaemolyticus) in commercial seafoods on Shanghai markets.

MethodsBased on the method of GB/T 4789.7-2008 from "Microbiological Examination of Food Hygiene: Examination of V.parahaemolyticus", the contamination of V.parahaemolyticus in seafoods from different predetermined monitoring sites in Shanghai was quantitatively determined and the occurrence of virulence genesthermostable direct hemolysin (tdh) and TDH-related hemolysin (trh), in 192 seafoods separated V.parahaemolyticus strains were detected by PCR.

ResultsA total of 2 643 seafood samples from wholesale markets, retail markets, supermarkets, catering industriesand online shopping were collected from January to December in the years of 2008 to 2013.V.parahaemolyticus was found in 192 samples (7.3%).Among 192 separated strains, 2.6%(5/192) that carried tdh or trh. 2.1%(4/192)were positive for tdh, and 0.5% (1/192) were positive for trh. The geometric mean densities of V.parahaemolyticus were different significantly in varied seafood species, sampling months, as well as locations(P < 0.05).Especially, geometric mean densities of V.parahaemolyticus in June to October were significantly higher than those in other months(P < 0.05).The detection rate (8.4%) and geometric mean densities(0.209 MPN/g) of V.parahaemolyticus in fishes were significantly higher than those in other seafood(P < 0.05). The geometric mean densities of V.parahaemolyticus in seafoods from wholesale markets, retail markets, supermarkets were higher than those from other sampling resources (P < 0.05).

ConclusionThe contamination of V.parahaemolyticus in seafoods during summer and fall is relatively higher from Shanghai markets. Some separated V.parahaemolyticus strains carry virulence genes tdh and trh. Thus the contamination of V.parahaemolyticus in seafood needs to be intensively monitored and environmental impact factors should be probed.And risk assessment and management should be carried out on high risk points for V.parahaemolyticus contamination.