Prevalence And Characterization Of Salmonella Serovars Isolated From Retailed Farm Products In Shanghai

Salmonella is a major bacterial pathogen that causes foodborne illness worldwide.Farm products,including raw meat,vegetables,and eggs,were important vehicles for transmitting foodborne pathogens.The contaminated produce,therefore,is a threat to human health.The main research results were as follows:Firstly,the prevalence of Salmonella was investigated and characterized,which was isolated from retailed farm products in Shanghai.A total of 344 samples were randomly collected.Using the Chinese National Standard method(GB 4789.4-2010),83 samples were positive for Salmonella,including 81 meat samples and 2 vegetable samples.All egg and raw milk samples were negative for Salmonella.Secondly,90 strains were isolated from the positive samples,and 12 serovars were identified.Enteritidis,Typhimurium and Derby were the predominant serovars.Thirdly,all isolates were characterized by multilocus sequence typing(MLST)and subtyped by pulsed-field gel electrophoresis(PFGE).Thirteen sequence types(ST)were identified by MLST.The results of PFGE showed that 73 PFGE patterns were generated from the isolates.Finally,Salmonella growth in pork at different temperatures was determined.Based on the data,a growth model was established.The internal and external validation results demonstrated that the established models were useful to predict the growth of Salmonella in pork.According to the theory of EGT,the concentration of Salmonella in pork could be calculated by the growth model under fluctuating temperatures.After validation,the growth model could predict the growth condition of Salmonella in pork well.In conclusion,Salmonella contamination was common among retailed farm products in Shanghai.The diversity of the isolates was high.