上海市一例肠出血性大肠埃希菌O157∶H7感染病例的病原学分析

Etiologic analysis on enterohemorrhagic Escherichia coli O157∶H7 from an infection case in Shanghai

目的通过流行病学调查与病原菌鉴定,并结合既往相关菌株资料,对2016年6月上海市腹泻病综合监测中报告的1例肠出血性大肠埃希菌(EHEC)O157∶H7感染病例进行病原学分析。方法对患者开展流行病学调查。采集标本后进行菌株分离培养、生化鉴定并确定血清型;利用聚合酶链式反应(PCR)检测所携带的毒力基因;采用微量肉汤稀释法进行药敏试验;应用脉冲场凝胶电泳(PFGE)技术进行分子分型;通过全基因组测序获取序列信息进行多位点序列分型(MLST)及单核苷酸多态性分析。结果流行病学调查未发现可疑传染源。患者样本分离出EHEC O157∶H7;携带eae、stx2基因;对进行试验的16种抗生素均敏感;菌株图谱带型与以往监测中分离菌株带型均不相同;MLST分型为ST11型,与以往分离菌株核心基因组差异较大。结论上海市较长时间无检出EHEC O157∶H7菌株的病例记录,通过对此次分离的菌株的全面检测,确定了其毒力基因、耐药性和MLST型别,并发现新的PFGE带型,其核心基因组与以往菌株呈现出一定差异,值得进一步关注。

Objective To understand the etiologic characteristics of an infection case of enterohemorrhagic Escherichia coli(EHEC) O157∶H7 in June,2016 in Shanghai.Methods The patient information was collected by epidemiological investigation.Two strains were isolated from case’s stool samples and identified by biochemical analysis and serologic tests.Polymerase chain reaction was conducted to detect the virulence related genes and microdilution broth method was used to analyze the antibiotic resistance.Pulsed-field gel electrophoresis(PFGE),multi-locus sequence typing(MLST) and single nucleotide polymorphisms(SNP) were conducted for further analysis on the strain’s characteristics.Results No suspected sources of infection were found by epidemiological investigation.The strains were confirmed to be EHEC O157∶H7 carrying eae and stx2,and they were sensitive to 16 kinds of antibiotics tested.Two strains were classified to ST11 while showed a new PFGE pattern.Compared with the reference strain,they showed more SNPs than the previously identified strains by core genome alignment.Conclusion No EHEC O157∶H7 has been isolated from patient for about ten years in Shanghai since2006.The virulence related genes,the antibiotic resistance and the ST type of the strains were confirmed in this study.They were more different from the previously identified strains according to the genome sequence alignment and PFGE results,further attention should be paid to it.