牦牛大肠杆菌的分离鉴定及系统发育分析

Isolation,Identification and Phylogenetic Analysis of E.coli from Yaks

本试验旨在研究牦牛源大肠杆菌的遗传进化关系,明确其与人和其他动物大肠杆菌的亲缘关系。采集来源于四川省甘孜州、阿坝州的60份临床健康成年牦牛肛门棉拭子样本,接种于麦康凯琼脂培养基上进行细菌的分离培养,通过常规形态学、培养特性、生化特征和16SrRNA PCR检测的研究,确定49株为大肠杆菌。对其中9株牦牛源大肠杆菌进行16SrRNA克隆、测序,经系统发育分析发现牦牛菌株组内同源性为98.8%～99.9%,与GenBank中其他菌株的同源性为94.0%～100%。结果表明,牦牛源大肠杆菌与牛源菌株的遗传距离最近,与羊源菌株的遗传距离最远,与人、猪、鸭、鸡源菌株的遗传距离较近,其中有2株菌与人肠出血性大肠杆菌(EHEC)O157∶H7和志贺氏菌聚为一支,从遗传进化的关系看其有可能成为人类的潜在病原菌。

The objective of this paper is to study the genetic evolutionary relationship of E.coli from yaks and identify their genetic relationship with human and other species of animals.A total of 60 anal swabs from healthy adult yaks in Ganzi and Aba prefecture were collected and inoculated in MaConkey agar.Suspected colonies were further identified by morphological observation,cultural character,biochemical assays and 16S rRNA PCR detection,and 49 strains of E.coli were finally obtained.The 16S rRNA of 9 E.coli strains was cloned and sequenced,and the phylogenetic analysis showed that the homology was high up to 98.8% to 99.9% among yak-origin strains,while the homology with other strains in GenBank was 94.0% to 100%.The results in this paper indicate that the yak-origin E.coli strains have close genetic distance with strains from cattle,and have closer distance with the strains from human,pig,duck and chicken,and have farther distance with the caprine strains,in which two strains are gathered to one cluster with human enterohemorrhagic E.coli（EHEC） O157∶H7 and Shigella,and these two strains may be the potential pathogenic bacteria for human being.