新疆奶牛乳房炎大肠杆菌种系分类群和基因相似性研究

Phylogenetic analysis and genetic similarity of E.coli isolated from Xinjiang

为了研究新疆地区奶牛乳房炎病例中大肠杆菌的种系分类群及其基因相似性,从新疆4个地区7个牛场奶牛乳房炎奶样分离的大肠杆菌中选出90株,用PCR扩增具有种系分类群标记的chuA、yjaA基因和TSPE4.C2 DNA片段。试验结果显示,所检测菌株中A群占93.33%,B1群占6.67%,未检测到属于B2和D群的肠外毒力株。进一步用RAPD技术分别以3个随机引物对这些菌株进行基因相似性分析并构建系统发育树,当相对基因相似性为0.25时,被检菌株分为10(A-J)个亚群,其中41.1%的菌株属于A亚群,21.1%的属于B亚群,17.8%的属于C亚群,其它20%的菌株不均匀的分布在7(D-J)个亚群中。其中,乌鲁木齐周边3个牛场50%的菌株、伊犁地区55.6%的菌株分布在A亚群,昌吉地区2个牛场66.7%分离菌株平均分布在A亚群和B亚群,库尔勒地区牛场25%分离菌株分布在A亚群,58.3%分布于C亚群。根据种系分类群标记研究结果显示,本次从奶牛乳房炎奶样中分离出的被检菌株均属于共生性大肠杆菌。基因相似性研究结果显示,大部分菌株分布在3个亚群中,不同地区分离菌株的基因相似性存在差异。

To investigate the phylogenetic relationship and genetic similarity of E.coli isolated in Xinjiang, 90 E.coli isdates collected from cow mastitis samples of 7 dairy cow herds in 4 different districts of Xinjiang were PCR amplified for genetic markers of chuA, yjaA and TSPE4.C2. The result showed that 93.33 % E.coli isolates belonged to group A and 6.67 % to group B1, none belonged to B2 and D groups. Analysis by random amplifed polymorphic DNA （RAPD） and construction of the phylogenetic dendrogram showed that these strains could be distributed in 10 subgroups from A-J, among which 41.1% in subgroup A, 21.1% in subgroup B, 17.8 % in subgroup C, and another 20 % of strains clustered into subgroup D-J. These results indicate that genetic similarity among E.coli isolates varies in different areas.