Detection of Yersinia enterocolitica in frozen and refrigerated foods

Objective To investigate the contamination of Yersinia enterocolitica (YE) in frozen and refrigerated food available in local malls or supermarkets in Liuan city of Anhui province.Methods Totally 523 frozen and refrigerated food samples were collected from several large malls and food counters in supermarkets in urban area of Liuan city during May to October from 2009 to 2014.The isolation and identification of YE in contaminated samples were conducted with biological,biochemical,and molecular biological methods.Results For all the samples,the positive rate of YE was 19.89%;the YE positive rate of the uncooked food samples were significantly higher than that of the cooked samples (30.75%99/232vs.2.49%5/201,χ²=62.03;P<0.01).Among the YE strains isolated,a total of 6 biochemical reaction modes belonging to biochemical type of 1A were identified and the dominant biochemical type was O:8.Virulence genes of ail,ystA,yadA,and virF were detected in all the 4 isolated strains of O:3.The results of pulsed field gel electrophoresis (PFGE) demonstrated that all the isolated pathogenic O:3 strains were K6GNIIC30021,a common poisonous strain in China,and were highly consistent to the O:3 strains isolated from specimens of local diarrhea patients and animal hosts in dendrogram.Conclusion The contaminated frozen and refrigerated food is one of the most important source of YE among the population in Liuan city.