中文摘要：

收集江苏地区养殖场及农贸市场动物粪便及食品样品700份,经显色培养基筛选、PCR鉴定大肠杆菌O157,并分析其进化分群、毒力基因、生物被膜形成能力、耐药性和耐药基因,了解O157污染情况。分离得到16株大肠杆菌O157,在粪便和食品中的分离率分别为2.6%（13/500）和1.5%（3/200）,进化分群显示D群占68.75%（11/16）为优势分群,68.75%（11/16）分离株能形成生物被膜。毒力基因stx1、stx2、hly A、eae的分布率分别为25%、37.5%、68.75%、63.16%。综合分析显示,不同来源菌株进化分群及毒力基因型相似。分离株的耐药率在56%以上,且至少同时耐受7种药物;耐药基因tet A、TEM、floR、cml A、aph3、aad A1、aad A2检测率50%-63%,其他耐药基因检测率小于30%。本研究表明动物粪便作为大肠杆菌O157的贮库,可能由养殖场感染动物并污染食品,威胁人类健康。

英文摘要：

To determine the extent of food contamination by Escherichia coli O157 in Jiangsu Province,a total of 700 animal fece and food samples were screened for E. coli O157 by selective culture medium and PCR amplification for O157 lipopolysaccharide O-antigen synthesis gene rfb E. Then,phylogenetic group,virulence genes distribution,biofilm formation,and antibiotic sensitivity were determined. E. coli O157 was detected in 2. 6%（ 13 / 500） animal fece samples and 1. 5%（ 3 / 200） food samples. Phylogenetic typing showed most isolates were classified to D group,and 68. 75%（ 11 / 16） isolates could produce biofilm. The stx1,stx2,hly A and eae genes were present in 25%,37. 5%,68. 75% and 63. 16% of O157 isolates,respectively. Moreover,the isolates from animal feces and food possessed the same gene combination.Antibiotic sensitivity test indicated more than 56% of E. coli O157 isolates were resistant to the commonly used antibiotics. Moreover,all isolates were even resistant to at least 7 different antibiotics. The detection results of antibiotic resistant genes showed that 50-63% isolates harbor the antibiotic resistant genes tet A,TEM,floR,cml A,aph3,aad A1 and aad A2,whereas the prevalence of other antibiotic resistant genes is less than 30%. Our results indicated that animal feces serve as reservoirs for food contamination by E. coli O157,which was a potential harm to human health.