北京市朝阳区腹泻患者致泻性大肠埃希菌流行特征及毒力基因携带情况分析

Epidemiological characteristics and virulence genes of diarrheagenic Escherichia coli from diarrheal patients in Chaoyang district of Beijing

目的分析北京市朝阳区感染性腹泻样本中致泻性大肠埃希菌(DEC)流行特征及毒力基因携带情况。方法收集2014—2017年北京市朝阳区哨点医院感染性腹泻样本,分离培养后应用real-time PCR方法检测DEC的主要毒力基因。其中利用eae、stx1、stx2、lt、st、aggR和ipaH 7种毒力基因进行DEC的分型鉴定,此外,检测并分析bfpA、astA、escV、pic、perA、ehxA、pet和ipaBCD等重要的毒力基因分布情况。结果从1 977份腹泻样本中共分离出94株DEC,检出率为4.75%。DEC的检出率具有随年龄增加而升高的趋势。0～5岁年龄组肠聚集性大肠埃希菌(EAEC)和肠致病性大肠埃希菌(EPEC)构成比分别是59.62%、23.08%。5岁以上年龄组肠产毒性大肠埃希菌(ETEC)构成比是59.52%。81.25%EPEC(13/16)未携带bfpA,为非典型EPEC(aEPEC)。38株EAEC中astA、pic和pet的携带率分别为39.47%、68.42%和92.11%。30株ETEC的st、lt和astA携带率分别是46.67%、56.67%和53.33%;仅1株(3.33%)ETEC同时含有st和lt。4株EHEC全部携带eae、escV和ehxA。6株肠侵袭性大肠埃希菌(EIEC)中ipaBCD、astA携带率为16.67%和33.33%。结论北京市朝阳区流行的DEC以EAEC、ETEC和EPEC为主,其中EPEC主要为aEPEC。婴幼儿主要感染EAEC,成年人主要感染ETEC。DEC中存在多种毒力基因,其中astA广泛存在于多种DEC中。

Objective To understand the epidemiological characteristics and the distribution of virulence genes of diarrheagenic E.coli(DEC)isolated from diarrheal patients in Chaoyang district of Beijing.Methods Stool specimens collected from diarrheal patients in sentinel hospitals in Chaoyang were cultured during 2014–2017.The virulence genes were tested by real-time PCR,diarrheagenic E.coli were identified by detecting seven genes,including eae,stx1,stx2,lt,st,aggR and ipaH,the distribution of other important genes,including bfpA,astA,escV,pic,perA,ehxA,pet and ipaBCD were also detected.Results A total of 94 DEC strains were isolated from 1 977 stool specimens(4.75%),the proportion of DEC isolation was increased along with age group increasing.The proportion of enteroaggregative E.coli(EAEC)and enteropathogenic E.coli(EPEC)in the isolates from age group 0–5 years was 59.62%and 23.08%.The proportion of enterotoxigenic E.coli(ETEC)in the isolates from age group>5 years was 59.52%.Up to 81.25%EPEC(13/16)strains carried no bfpA,belonging to atypical EPEC(aEPEC).Among 38 EAEC strains,39.47%carried astA,68.42%carried pic,92.11%carried pet.Among 30 ETEC strains,46.67%carried st,56.67%carried lt,53.33%carried astA,and 3.33%carried both st and lt.All 4 enterohemorrhagic E.coli(EHEC)strains carried eae,escV and ehxA.Among 6 enteroinvasive E.coli(EIEC)strains,16.67%carried ipaBCD,33.33%carried astA.Conclusion The DEC isolates from diarrheal patients in Chaoyang were dominated by EAEC,ETEC and EPEC,aEPEC accounted for the majority of EPEC.Infants and young children were mainly infected with EAEC,and adults were mainly infected with ETEC.The virulence genes of diarrheagenic E.coli showed diversity,and astA existed in multi-types of diarrheagenic E.coli.