Epidemiological Investigation Of Bovine Mastitis In Northern Jiangsu And Correlation Analysis Between Drug Resistance And Virulence Genes Of Escherichia Coli

Cow mastitis is one of the most common diseases with the highest incidence rate in dairy farming.Escherichia coli is the main pathogen causing cow mastitis worldwide.With the application of antibiotics,drug-resistant bacteria can selectively evolve.The emergence of multi drug-resistant strains leads to the increasingly serious problem of drug resistance of Escherichia coli.Antibiotic resistant Escherichia coli is becoming a potential threat to veterinary medicine and public health.In this study,the clinical mastitis milk samples of dairy cows from three large-scale pastures in Northern Jiangsu were collected for epidemiological investigation of pathogens,and the main pathogens were isolated and identified.The drug resistance phenotype,drug resistance gene and virulence gene of Escherichia coli isolates were detected,their phylogenetic typing was identified,and the correlation between drug resistance phenotype,virulence gene and germline developmental typing was discussed.To understand the dominant pathogens of cow mastitis infection in Northern Jiangsu,the distribution of drug resistance and virulence genes of Escherichia coli and their relationship,so as to provide experimental basis for effectively controlling the epidemic and transmission of Escherichia coli cow mastitis in northern Jiangsu.In this study,156 clinical mastitis milk samples from three large-scale pastures in Northern Jiangsu were isolated and identified by bacterial culture and 16SrDNA.The results showed that among the 156 milk samples collected,12 kinds of bacteria were isolated,a total of 289 strains,13 sterile milk samples,and the total detection rate of bacteria was 91.67%;Among them,there were 78 strains of Escherichia coli,the prevalence rate was 26.99%,followed by 67 strains of Klebsiella(23.19%)and 38 strains of Staphylococcus(13.15%).78 strains of Escherichia coli isolated from dairy cow mastitis samples in Northern Jiangsu pasture were tested for drug sensitivity by K-B disk diffusion method.The results showed that they were resistant to lincomycin,penicillin,amoxicillin and cefoxitin.The drug resistance rates of lincomycin,penicillin,cefoxitin and amoxicillin were 66.7%,60.2%,57.7%and 55.1%,respectively;It was most sensitive to gentamicin and tetracycline,with a sensitivity rate of 83.3%,followed by streptomycin and ciprofloxacin,with 73.1%and 71.8%respectively.Detected by PCR β-Lactam blaTEM,blaCTX-M,blaSHV,aminoglycoside armA and armB,tetracycline tetA,tetB,tetC and quinolone qnrS,qepA,oqxA and oqxB.All E.coli carried blaTEM gene,and the detection rate of blaCTX-M was 53.8%.The detection rates of blaSHV(20.5%),armA(9.0%),tetA(26.9%),tetB(2.6%),tetC(20.5%),qnrS(29.5%),oqxA(37.2%)and oqxB(1.3%)were low,and armB and qepA genes were not detected.The phylogenetic typing and 22 virulence genes including f17A,fimH,papC,sfaD,afaD8,afaE-8,stxl,stx2,cnf1,cnf2,LT1,STb,hlyA,iucD,colV,ompC,ompF,irp2,fyuA,eaeA,ler and Ecs3703 were detected by PCR amplification.The results showed that type A accounted for 37.2%,type B1 52.5%,type B2 1.3%and type D 9.0%.Eight virulence genes were detected,including ompC(98.7%),fimH(94.9%),ECs3703(92.3%),ompF(82.1%),irp2(32.1%),fyuA(32.1%),iucD(24.4%)and f17A(1.3%).Among the 78 strains of E.coli,type B1 is the most,and it carries the most kinds of virulence genes.SPSS software and other statistical methods were used to analyze the correlation between drug resistance and virulence genes of 78 strains of Escherichia coli.The results showed that there were different degrees of correlation between drug resistance phenotype,virulence gene and phylogenetic typing.