Surveillance Of Vibrio Parahaemolyticus In Shanghai And Screening Of Its Hamelysin Genes

Vibrio parahaemolyticus (VP) is a kind of gram-negativepathogenic bacteria which can cause food poisoning. This bacteriawidely exist in shellfishes, fishes, shrimps and other seafood.Surveillance of V. parahaemolyticus in seafood is necessary for foodsafety control. It contributes to government departments to make thelaws and regulations of food safety at the same time, it can also providetheoretical basis for the study to V. parahaemolyticus, and give somehelpful suggestions for consumers.In this study, the surveillance of V. parahaemolyticus in seafood inShanghai was carried out from August2012to July2013. The tdh/trhgenes was identificated by ERIC-PCR typing.The major contributions of the research were described as follows:1The detection of V. parahaemolyticus in seafood in ShanghaiTo investigate prevalence of the contamination, total257sampleswere collected from local markets and supermarkets in Xuhui, Pudong,Minhang, Huangpu, Baoshan, Zhabei, Luwan districts, including oysters,clams and so on. V. parahaemolyticus was isolated from samplesaccording to the National Standard Method (GB/T4789.7-2008)combining with selective media including Thiosulfate-citrate-bilesalts-sucrose agar (TCBS) and CHROMagarTMVibrio (CV). In thissection,119suspected V. parahaemolyticus isolates were screened. This results suggested that the seafood was heavily contaminated with V.parahaemolyticus.2Identification of the suspected isolatesIn this study, V. parahaemolyticus was identified by combining themethod of biochemical tests with PCR. In the biochemical test, thesuspected isolates were identified by a kit. In the PCR test, thesuspected strains were identified by the irgB gene (vp2603), whichscreened by Shuijing Yu in our lab, coding for iron-regulated virulenceregulatory protein. In the biochemical test,105V. parahaemolyticusisolates were identified. While in the PCR test,107V. parahaemolyticusisolates were identified. The results from two methods were notconsistent. Finally,105V. parahaemolyticus isolates were confirmed.3The surveillance of V. parahaemolyticus in oyster from asteadfast retail store in Minhang.There were three times to sample each month from a steadfastretail store in Minhang during August2012to July2013. The number ofV. parahaemolyticus in oysters was quantificated by total colonycounting method. In this section, the results showed that we can separateV. parahaemolyticus were found in the samples in twelve monthes ofwhole year. There was a high pollution rate of V. parahaemolyticus insummer (July, August, Septemper). Oppositly, there was a low pollutionrate of V. parahaemolyticus in oyster in winter (January, February,March).4Screening to mainly virulence genes tdh and trhIn this study, the haemolysin genes, including tdh and trh, wereidentified by PCR. The positive strains of tdh gene were9strains, andthe positive strain of trh gene was1strain. One isolate harbors bothgenes. As the positive rate of V. parahaemolyticus is very high inseafood from the retail markets, more resgulations and food safety controls are required.5The method of ERIC-PCR to type105V. parahaemolyticusEnterobacterial repetitive intergenic consensus (ERIC) PCR was used totype105V. parahaemolyticus isolates. When the similarity index is over75%, these isolates can be divided into74ERIC types,22groups. The resultsillustrated that the food-borne V. parahaemolyticus strains had a highdiversity.