青海腹泻牦牛大肠杆菌分离株的生物学特性研究

Study on Biological Characteristics of Escherichia coli Isolated from Yaks with Diarrhea in Qinghai Plateau

牦牛大肠杆菌病是一种严重危害牦牛养殖业发展的重要疾病,大肠埃希氏菌是主要病原。为了查明青海地区牦牛的大肠杆菌菌株中存在的毒力基因类型、血清型及耐药关系,本研究收集了青海高原腹泻牦牛292份肛拭子,采用纸片扩散试验、平板凝集试验、PCR试验评估大肠杆菌分离株的耐药性、毒力基因、血清型和进化分型。结果显示:大肠杆菌分离株中多重耐药率占97%,至少含有一种毒力基因;10种毒力基因(sfa、eae A、cnf1、etr A、pap C、hly A、aer、fae G、rfc和sep A)中优势毒力基因sfa占96.9%;一些抗性表型和毒力基因之间显著正相关(P<0.05,OR﹥1);大部分大肠杆菌属于A型(79.5%),其他属于B1(7.5%)、D(4.1%)、B2(5.8%)和F型(0.7%);在所有检测到的大肠杆菌菌株中,血清型O91和O145最为普遍,分别占15.4%和14.4%。结果表明,腹泻牦牛大肠杆菌分离株耐药性较高,携带毒力基因种类多,这给大肠杆菌的防治带来较大挑战。

Yaks serve as one of the most important reservoirs for pathogenic Escherichia coli.It’s the main pathogenic bacteria in yaks with diarrhea.Therefore,from a clinical and human health perspective,it is important to know which virulence genes,phylogenetic groups,serogroups,and antibiotic resistance patterns are present in E.coli strains in yaks with diarrheic infections.Two-hundred and ninety-two rectal swabs were collected from diarrheic yaks in Qinghai Plateau,China.The antimicrobial sensitivity of each resulting isolate was evaluated according to the disk diffusion method,and different PCR assays were performed for the detection of virulence genes and different phylogroups.Among the E.coli isolates tested,most of the isolates were multidrug resistant(97%)and harbored at least one virulence gene(100%).We observed ten virulence genes(sfa,eaeA,cnf1,etrA,papC,hlyA,aer,faeG,rfc,and sepA),of which sfa was the most commonly found(96.9%).Significant positive associations between some resistance phenotypes and virulence genes were observed(P<0.05,OR>1).The majority of the E.coli isolates belonged to phylogroup A(79.5%),and the others belonged to phylogroups B1(7.5%),D(4.1%),B2(5.8%),and F(0.7%).Among all the E.coli strains tested,serogroups O91 and O145 were the most prevalent,accounting for 15.4 and 14.4%,respectively.Our results suggest that yaks with diarrhea serve as a reservoir of pathogenic E.coli carrying various virulence genes and resistance phenotypes.Therefore,clinicians and relevant authorities must ensure the regulatory use of antimicrobial agents and prevent the spread of these organisms.