产志贺样毒素和肠毒素大肠杆菌分子流行病学

[目的]人和动物腹泻的主要病原菌为大肠杆菌,本文主要研究贵州省致腹泻大肠杆菌毒力因子的分布类型.[方法]采用PCR技术对各毒力因子的基因分布进行研究.[结果]共分离到333株大肠杆菌,其中产肠毒素大肠杆菌(ETEC)在腹泻的人、猪、牛群中占优势,分别为:人群73(n=112),猪群82(n=106),牛群18(n=115).在ETEC菌株中检测到热敏肠毒素(lt)和不耐热肠毒素(st)基因,还存在lt/st并存现象.从人、猪、牛群中还检测到产志贺样毒素大肠杆菌(STEC),其中源自猪的STEC的检出率最高.大部分STEC同时携带lt、st或lt和st同时并存.编码F18菌毛的主亚基由fedA基因编码.对所分离大肠杆菌F18菌毛进行的研究结果表明,fedA基因主要与肠毒素基因共存,与stx基因并存的类型较少,25份猪源STEC菌株中仅有4份检测到fedA基因.[结论]贵州省人群、猪群和牛群致腹泻病原菌中以带F18菌毛的ETEC为主,STEC主要分布在腹泻的猪群中.

Prevalence of Shiga toxin- and enterotoxin-producing Escherichiacoli in patients and animals in Guizhou, China

[Objective]: To assess the public health risk, we studied the prevalence of enterotoxigenic Escherichia coli (ETEC) and Shiga toxin-producing E. coli (STEC) among pig, cattle and human in Guizhou Province. [Methods]: E. coli isolates from fecal samples were investigated for their virulence markers by polymerase chain reaction (PCR) assays. [Results]: Of 333 E. coli isolates, ETEC was predominant and detected in 73 of 112 isolates from patients, 82 of 106 isolates from pigs, and 18 of 115 isolates from cattle. The distribution of genes st, lt, and st/lt was equivalent in ETEC isolates. The detection rate of STEC from pig isolates was higher than that from patient and cattle isolates, most of which carried genes for st or lt or both. Furthermore, we analyzed the presence of the fedA gene encoding the major subunit of F18 fimbriae in E. coli isolates. Although most isolates were negative in the PCR, the presence of F18 fimbriae in the E. coli isolates was always associated with enterotoxin genes. In 25 stx-positive STEC isolates, however, only 4 STEC from pigs with diarrhea detected fedA. [Conclusion]: These results indicate that ETEC, coexisting with F18 fimbriae, is common in patients, cattle, and pigs, while STEC is dominant in pigs in Guizhou Province, China.