大肠埃希菌O157血清型分离株的脉冲场凝胶电泳分型

Pulse field gel electrophoresis analyses in Escherichia coli O157 isolates

目的了解杭州地区分离的产志贺毒素和不产志贺毒素大肠埃希菌O157菌株的分子流行病学特征。方法对杭州地区于1997～2005年间自散发腹泻患者和动物中分离的10株大肠埃希菌O157血清型菌株,PCR检测毒力基因stx1、stx2、eae和ehxA,eae阳性者进行eae基因分型;按标准化的脉冲场凝胶电泳法(pulsefieldgelelectrophoresis,PFGE)进行分子分型,并与国内其他省份分离的产志贺毒素大肠埃希菌(Shigatoxin_producingEscherichiacoli,STEC)O157∶H7菌株进行比较。结果杭州分离菌株HZ1_11携带毒力基因stx2、γ型eae和ehxA,为浙江省检获的首株STECO157∶H7;3株杭州O157∶NM分离菌株(2_1、26_1和SR05株)仅携带β型eae基因;其他6株杭州O157∶H?分离菌株中,均未检出毒力基因。PFGE揭示,在杭州人源O157菌株中,STECO157∶H7HZ1_11株与近年江苏和安徽分离STECO157∶H7菌株密切近缘,且其图谱与江苏菌株几乎完全相同;3株eae阳性的O157∶NM分离菌株聚类成与STECO157∶H7菌株较远的一簇,杭州1株stx阴性的O157∶H?(1_68株)则处于另一独立的一簇。5株杭州O157∶H?动物分离菌株与其他人源菌株图谱差异极大。结论浙江省首株STECO157∶H7可能是源自近年在江苏流行的STECO157∶H7菌株。β型eae阳性的大肠埃希菌O157∶NM菌株可能具有引起散发腹泻的能力。

Objective To understand the molecular epidemiological characteristic of Escherichia coli 0157 isolates with or without Shiga toxin found in Hangzhou, Zhejiang province, China. Methods In 10 E. coli 0157 isolates from sporadic diarrheal patients or swines during 1997 to 2005, virulence genes, including stxl, stx2, eae, and ehxA, were examined by PCR assays. For the eae positive isolates, eae genes were typed by PCR using specific primers for the 3＇ variable regions of eae. Pulse field gel electrophoresis（PFGE） analyses of these 10 isolates and some representive isolates of Shiga toxin-producing E. coli （STEC） O157：H7 from Jiangsu and Anhui provinces were performed according to the standardized protocol of PulseNet USA. Results One isolate （HZ1-11） from a sporadic diarrheal infant in Hangzhou was identified as STEC O157：H7 with stx2, ehxA and γ-eae positive and sorbitol negative. Three O157：NM isolates from diarrheal patients in Hangzhou merely harbored β-eae. In other 6 isolates of O157： H？ from Hangzhou, any of these 3 virulence genes was not found. The PFGE pattern of the isolate HZ1-11 was very close to these of the recent STEC O157：H？ isolates from Jiangsu and Anhui provinces, especially indistinguishable from that of one isolate from Jiangsu. Three O157： NM isolates with β-eae were categorized within one cluster distant to the cluster of STEC O157 ： H？ isolates. One stx-O157：H？ isolate from a diarrheal patient was located on another independent branch. The PFGE patterns of all Five O157： H？ isolates from swines were different significantly to these of all O157 isolates from patients. Conclusion The fLrst STEC O157 ： H7 isolate HZ1-11 in Zhejiang might derive from one clone group of STEC O157： H7 prevailing in Jiangsu recently. E. coli O157：NM isolates with β-eae may have potential to cause human sporadic diardaea.