Identification And Analysis Of Virulence Genes Of Escherichia Coli From Cow Milk In A Cattle Farm In Southern Xinjiang

In recent years,the proportion of mastitis induced by E.coli in southern Xinjiang has been increasing.Thus,a survey of E.coli from cow milk in southern Xinjiang was carried.In this study,the isolation and identification of E.coli,the drug sensitivity analysis of E.coli,the detection of biofilm formation ability,and the detection and analysis of the virulence gene of E.coli were explored.Biochemical tests,16 S rRNA gene sequencing,and specific PCR amplification was used to isolate and identify E.coli.The drug sensitivity of the isolated E.coli to 13 antibacterial drugs was tested by K-B method.The ability of biofilm formation was detected by the microplate semi-quantitative method.PCR amplification of 9 virulence genes was done.The results showed that 20 strains of E.coli were isolated from 80 milk samples.The 20 tested strains had the highest resistance rate to amoxicillin(85%),and showed the same resistance rate to ampicillin,chloramphenicol,and sulfa(75%).The drug resistance rates to florfenicol,kanamycin,gentamicin,enrofloxacin,tetracycline(and polymyxin),and ofloxacin were70%,65%,50%,25%,20% and 15%,respectively.The sensitivity rate to ceftazidine and meropenem was100%,and the drug resistance rate was 0%.The biofilm-forming ability of E.coli was detected in this study was weak,and no strains had a strong biofilm-forming ability,indicating that the E.coli isolated in this study is likely to be an opportunistic pathogen and a source of intestinal bacteria that contaminates milk.During the breeding process of dairy cows,due to human factors such as incomplete disinfection of milking equipment,poor sanitation of dairy cows,or poor management by staff,E.coli invades the breast tissue,which may cause E.coli mastitis in dairy cows.Such pathogenic bacteria have weak biofilm formation ability.Among the 9 tested virulence genes,all strains contained 5 genes,including lsr B,lsr R,aer,omp A and trat,were with a detection rate of 100%;none of the strains detected two genes of eae and mtn.14 strains contained iuc D and the detection rate was 70%.2 strains contained lux S and the detection rate was 10%.It suggested that the virulence genes distribution of E.coli isolated in this farm be relatively complicated,which could bring challenges to clinical treatment.