北京地区腹泻病患者致泻性大肠埃希菌感染类型及其流行特征

Study on the genotype and epidemic characteristics of diarrheagenic Escherichia coli isolated from diarrheal patients in Beijing

目的：了解北京地区腹泻人群中致泻性大肠埃希菌（DEC）毒力基因的分布及流行特征。方法对2012-2013年监测医院的腹泻患者粪便样本进行分离培养，再采用实时荧光PCR检测毒力基因。结果6370份粪便标本有253份阳性，共分离到DEC 262株，阳性检出率为4.0%（253/6370），9份标本发现两种不同型别的DEC混合感染。肠致病性大肠埃希菌（EPEC）为42.8%，其中非典型EPEC占42.0%，典型EPEC占0.8%；肠产毒性大肠埃希菌（ETEC）为38.9%，其中耐热肠毒素基因st阳性占24.8%，不耐热型肠毒素基因lt阳性占9.9%，st和lt均阳性占4.2%；肠聚集性大肠埃希菌（EAEC）为15.3%；肠侵袭性大肠埃希菌（EIEC）为2.7%；检出1株产志贺毒素大肠埃希菌（STEC），血清型为O26∶K60。ETEC感染具有明显的年龄分布特征；各型DEC全年均有检出，且呈季节性变化。结论北京地区腹泻病患者DEC感染类型以EPEC和ETEC为主，且EPEC分离株多为非典型，并存在混合感染，不同型别DEC感染具有年龄和季节性分布特征。

Objective To understand the distribution of virulence gene and the epidemiological characteristics of diarrheagenic Escherichia（E.） coli （DEC） from diarrheal patients in Beijing. Methods Stool specimens from diarrheal patients were cultured which were collected from the hospitals under sentinel surveillance program,during 2012-2013. DNA was examined by real-time PCR. Results 253 out of 6 370 specimens were positive for DEC detection with the rate as 4.0%. A total number of 262 DEC strains were isolated. Two different pathotypes of DEC strains with mixed infection,were isolated from 9 specimens. Different pathotypes would show the following profiles：42.8% for enteropathogenic E. coli （EPEC） including 42.0% atypical and 0.8% typical;38.9% for enterotoxigenic E. coli（ETEC）including 24.8%st positive,9.9%lt positive and 4.2%st and lt both positive;15.3% for enteroaggregative E. coli（EAEC）;2.7% for enteroinvasive E. coli（EIEC）;one strain STEC with serotype O26 ∶ K60. ETEC had obvious characteristics on age. All kinds of DEC were isolated throughout the year with seasonal fluctuation. Conclusion DEC isolates from diarrheal patients in Beijing were dominated by EPEC and ETEC,with atypical ones accounted for the majority of EPEC. One specimen was found under mixed infection. Pathotypes DEC were found to have different age and seasonal distributions.