1株多重耐药致病性大肠杆菌的分离鉴定与分子分群

2017年1月,新疆博乐某牛场犊牛群出现腹泻疫情,本试验旨在调查病因并制定相应的防控措施。采集6头腹泻犊牛的肛拭子和新鲜粪便样本,先用Speed V-Diar4^TM试纸进行轮状病毒、冠状病毒、隐孢子虫和大肠杆菌F5(K99)的检测,再对样本进行病原菌的分离鉴定和分子分群,最后对分离菌进行致病力及耐药性的检测。结果显示,所有粪便样本的试纸检测结果均为阴性,从6份样品中共得到6株大肠杆菌和1株爱德华氏菌,分子分群PCR检测结果显示6株大肠杆菌中A群占83.3%(5/6),F群占16.7%(1/6)。半数致死量结果显示,只有1株大肠杆菌(菌株XJ-B1)具有致病性,可致小白鼠腹泻和死亡。药敏试验结果显示,7株分离菌对这18种抗生素产生不同程度的耐药性,其中致病性大肠杆菌XJ-B1耐药程度最严重,对β-内酰胺类、磺胺类和多肽类抗生素耐药,为多重耐药菌。由此可见,这株致病性大肠杆菌可能是引起本次犊牛腹泻的病因之一,也是本试验首次分离到牛源的F群大肠杆菌,该菌的多重耐药性增加了临床治疗的难度,而本试验结果为该牛场治疗此次犊牛腹泻提供了依据。

Isolation,Identification and Phylogenetic Group of a Strain of Multidrug-resistant Pathogenic Escherichia coli

In January 2017,a diarrhea epidemic occurred in calves of a cattle farm in Bole,Xinjiang.The purpose of this study was to investigate the etiology and formulate corresponding prevention and control measures.Anal swabs and stool samples from 6 diarrhoeal calves were collected,rotavirus,coronavirus,Cryptosporidium and Escherichia coli F5 (K99) were detected by Speed V-Diar 4^TM test paper.Then the samples were isolated,identified and molecular clustering,the pathogenicity and drug resistance of the isolated bacteria were detected.The test results of all stool samples were negative.6 strains of Escherichia coli and 1 strain of Edwardsiella tarda were obtained from 6 samples.Phylogenetic PCR analysis showed that 6 strains of Escherichia coli A group accounted for 83.3%(5/6),F group accounted for 16.7%(1/6).Half the lethal dose result showed that only one strain of Escherichia coli (strain XJ-B1) was pathogenic,and could cause diarrhea and death in mice.The results of drug sensitivity test showed that 7 isolates had different degrees of resistance to the 18 antibiotics,and Escherichia coli XJ-B1 was the most serious drug-resistant strain.It was multidrug-resistant to beta-lactams,sulfonamides and polypeptide antibiotics.Therefore,this pathogenic Escherichia coli might be one of the causes of this diarrhea in calves,and it was also the first group F Escherichia coli isolated from cattle.The multi-drug resistance of the bacteria increased the difficulty of clinical treatment.This results provided a basis for the cattle farm to treat the calf diarrhea.