O157大肠埃希菌食品分离株的特征研究

目的掌握福建省E.coliO157∶H7和O157∶H?食品分离株的毒力基因携带状况、PFGE分型特征、抗生素的药敏谱以及产志贺毒素的E.coliO157∶H7菌株的细胞毒性状况。方法分离菌株经VITEK全自动生化系统鉴定;O157和H7单克隆诊断血清凝集;PCR法检测O157、H7抗原基因及毒力因子基因;菌株的分型用PFGE方法进行;采用CLSI推荐的K-B法对菌株进行15种抗生素的药敏试验;对产志贺毒素的分离株用Vero细胞和Cyto Tox 96R○试剂盒进行细胞毒性检测。结果2株E.coliO157∶H7,其O157、H7及Stx2、Hly、eaeA毒力基因均阳性,Stx1基因均阴性;另3株E.coliO157∶H?,其O157基因阳性,H7和Stx1、Stx2、Hly、eaeA毒力基因均阴性;5株菌的PFGE带型各不相同,2株E.coliO157∶H7的同源性较高,达81%;菌株对15种常用抗生素较为敏感,链霉素、甲氧苄啶敏感率稍低为40%,其余敏感率达60%～100%。2株产志贺毒素的菌株对Vero细胞有毒性作用,细菌细胞比位50:1时细胞毒性百分比分别为61.25%和67.80%。结论本省在外环境动物性食品中存在产志贺毒素的E.coliO157∶H7菌株,提示应加强E.coliO157∶H7的监测,预防该菌在本省人间的感染和流行。

Characterization of Escherichia coli O157 isolated from foodstuffs in Fujian province

The virulence genes,resistance to antimicrobial drugs,PFGE pattern and cytotoxicity of the Shiga toxin-producing Escherichia coli O157 isolated from foodstuffs in Fujian province were investigated in the present study,in which the virulence genes including the stx1,stx2,hly and eaeA of O157∶H7 were examined by PCR;PFGE was used to analyze the pattern of genomic DNAs;resistance to antimicrobial drugs were performed with 15 antibiotics by K-B test and cytotoxicity of the Shiga toxin-producing E.coli O157∶H7 isolates was assayed by using the Cyto Tox 96○R kit.It was found that two out of five isolates were identified as E.coli O 157∶H7 with the presence of the virulence genes stx2,hly and eaeA,but without stx1 gene.In another 3 strains of isolates,the O157 genes were present and no H7 stx1,stx2,hly or eaeA genes could be detected.The PFGE patterns of these 5 strains of isolates were quite different,in which the homology between 2 strains approached up to 81%.The drug-susceptibility of these isolates to 15 commonly used antibiotics was high and the rates of sensitivity were 60-100%,Cytotoxicity to vero cells could be demonstrated in 2 strains of the Shiga toxin-producing isolates in a effector/target cell ratio of 50∶1 with the percentages of cytotoxicity of 61.25% and 67.8% respectively,It is concluded that there exists the Shiga toxin-producing strains of E.coli O157∶H7 with the virulence gene stx2 isolated from foodstuffs in some regions of Fujian province,indicating that the transmission of these bacteria in humans may occur and surveillance on the infection with E.coli O157∶H7 should be considered seriously.