不同来源STECO157:H7生物学特性研究

Study on biological characteristics of Shiga toxin-producing Escherichia coli O157:H7 from different sources

目的探讨浙江省产志贺毒素大肠埃希菌O157:H7菌株PFGE分型及携带毒力基因以及耐药情况。方法菌株生化、血清鉴定按API20E鉴定系统;大肠杆菌O157:H7诊断血清凝集试验;采用聚合酶链反应(PCR)法检测O、H抗原及毒力基因SLT1、SLT2、Hly、eaeA;STECO157:H7分型用脉冲场凝胶电泳(pulse field gel electrophoresis,PFGE)方法进行;14种抗生素进行药敏试验采用K-B法。结果5株可疑菌株经生化和血清鉴定符合O157:H7特性;毒力基因检测所有分离株SLT2、Hly、eaeA三种毒力基因均阳性而SLT1均阴性;脉冲场凝胶电泳分型结果显示,有2株菌PFGE电泳条带完全相同,其余3株菌电泳条带不同,5株菌共分为4个带型;经耐药性分析,菌株对头孢噻吩、头孢噻肟、庆大霉素、环丙沙星100%敏感;对复方新诺明、氨苄西林100%耐药。结论STEC 0157:H7菌株在浙江省一些地区存在,并且携带SLT2毒力基因,PFGE型别较多,同时也有人间感染病例的出现,提示应加强O157:H7监测力度,防止该菌在人间的感染和流行。

Objective The present study was conducted to find out the pulsed field gel electrophoresis （PFGE） patterns, virulence genes and drug resistance of Shiga toxin-producing Escherichia coli （STEC O157：H7） in Zhejiang Province. Methods The biochemistry and the serotype of STEC O157：H7 was identified by the API 20E identification system and slide agglutination test with diagnostic antiserum specific for O157：H7, respectively. O antigen, H7 antigen of suspicious STEC O157：H7 and its virulence genes, including stxl, stx2, hly and eae, were examined by routine PCR.The pulse field gel electrophoresis （PFGE） was used to analyze the pattern of the genomic DNA, digested by Xbal. Antimicrobial susceptibility tests were performed with 14 antibiotics by K-B test. Results 5 suspicious strains were identified as STEC O157：H7 with biochemical and serological test. PCR results shows that SLT2, hly and eaeA were positive and SLT1 was negative. There were 4 PFGE patterns of the 5 STEC O157：H7 strains. The PFGE patterns of 2 Jinghua isolates were homologous and that of the other 3 strains were apparently different. Analysis on drug-resistance shows the isolates were susceptible to Cefalotin, Claforan, Gentamicin, and Ciprofloxacin （100%）, but resistant to co-trimoxazole and Ampcillin（100%）. Conclusion In some regions in Zhejiang Province there exists STEC O157：H7 with the virulence gene SLT2, which takes on multiple PFGE patterns. Transmission of the infection among human beings may be likely to occur, and surveillance on O157：H7 should be taken seriously to prevent the bacteria from being transmitted among human beings.