牛乳房炎致病性大肠埃希氏菌耐药性、毒力基因与生物被膜分析

Analysis of Drug Resistance,Virulence Genes and Biofilms of Pathogenic Escherichia coli Isolated from Bovine Mastitis

为分析宁夏、甘肃部分地区奶牛乳房炎致病性大肠埃希氏菌(E.coli)耐药性、耐药基因、毒力基因、生物被膜及系统发育分型,对临床乳房炎奶牛乳样中分离鉴定的54株E.coli用肉汤稀释法、聚合酶链反应(PCR)和结晶紫染色法,对其进行耐药性、耐药基因、毒力基因、系统发育分型及生物被膜检测。结果表明,54株E.coli对头孢噻肟耐药率高达100%,对氨苄西林、四环素、氟苯尼考、庆大霉素、头孢吡肟、替加环素、恩诺沙星,耐药率依次为74.07%、57.40%、24.07%、18.51%、11.11%、11.11%、5.56%,对美罗培南均表现为敏感;β-内酰胺类耐药基因中blaCTX基因检出率最高94.44%,blaTEM基因检出率为33.33%;四环素类耐药基因中tetB检出率为55.56%,tetA、tetC检出率为1.85%、3.7%,耐药基因高检出率与耐药性表现一致。毒力基因检测结果显示,菌毛黏附素fasA为31.48%,α溶血素hlyA为16.67%,志贺毒素stx1为7.4%;系统发育分型结果显示A型是该地区主要的流行菌株,其携带毒力因子的占比也高于其他菌型,所有受试菌株均可形成生物被膜。表明奶牛乳房炎来源E.coli对常用抗菌药物耐药严重,携带hly与stx1毒力基因的E.coli占比高,需要引起重视。

The purpose of this study was to determine the drug resistance,resistance genes,virulence genes,biofilm and phylogeny of Escherichia coli isolated from bovine mastitis in Ningxia and Gansu.Broth dilution method,crystal violet staining method and polymerase chain reaction(PCR)were used to detect the drug resistance,biofilm,virulence genes and drug resistance genes and phylogenetic typing of 54 E.coli strains.The results showed that 54 strains were resistant to cefotaxime as high as 100%,followed by ampicillin,tetracycline,florfenicol,gentamicin,cefepime,tigecycline and enrofloxacin,the resistance rates were 74.07%,57.40%,24.07%,18.51%,11.11%,11.11%and 5.56%respectively.Remarkably,all strains were sensitive to meropenem.The detection rate of blaCTX gene amongβ-lactam resistance genes was 94.44%,followed by 33.33%of blaTEM gene;the detection rate of tetB among tetracycline resistance genes was 55.56%(30/54),the detection rates of tetA and tetC were 1.85%,3.7%.The high detection rate of drug resistance genes was consistent with the performance of drug resistance.The results showed that 54 strains of E.coli could form biofilms,12.96%had medium biofilm forming ability,and 87.04%had weak biofilm forming ability.The results of the virulence gene test showed that the fasA was 31.48%,theα-hemolysin hly was 16.67%,and the Shiga toxin stal was 7.4%.Phylogenetic typing results showed that type A is the main epidemic strain in these areas,and its proportion of carrying virulence factors is also higher than that of other bacterial types.In summary,this study indicated that mastitis E.coli is highly resistant to common antimicrobials.E.coli carrying hlyA and stal virulence genes account for a high proportion,and its potential threat needs to be taken seriously.