Virulence And Resistance Analysis Of The Echerichia Coli Isolated From Diarrhea Piglets

Neonatal piglet diarrhea is one of the most common diseases in swine industry.Its high morbidity and mortality caused enormous economic losses to farmers.Enterotoxigenic Escherichia coli(ETEC)is considered as a major pathogen that causing piglet diarrhea and the pathogenicity of ETEC is closely related to its virulence factors.Because of the limited protection of the vaccine designed base on the ETEC's virulence factors,antibiotics are widely used in the clinical veterinary for the prevention and treatment of diarrhea piglets.However,the use of antibiotics will accelarate the emergence of drug-resistant strains.At the same time,drug resistance genes can also spread to the environment through horizontal transmission,which pose a potential threat to human health.This study was conducted to obtain the basic data of virulence genes,drug resistance and resistance genes of Escherichia coli isolates from the diarrhea piglets in Jilin and Henan regions,and evaluate the ability of horizontal transmission of the virulence genes and resistance genes in ESBLs strains.Above of these studies aim to provide a foundation for developing a targeted treatment and control technology.From 2015 to 2016,a total of 105 fecal swabs were collected from newborn diarrhea piglets in Jilin and Henan province.195 E.coli strains were isolated and identified ultimately.Seven virulent genes were detected including eae?sta?stb?EAST1?F4?bfp and irp-2.The detection rate of EAST1 gene was the highest in Jilin and Henan districts and were both above 31.7%.The result of the phylogenetic background showed that most of the isolates belonged to group A and B1,14.4% E.coli isolates belonged to group B2 and D which were pathogenic.There were 93.8% multi-drug resistant strains among the 195 E.coli isolates and 102 strains were ESBLs.On the whole,in the two regions,over 80.0% isolates were resistant to gentamicin,ampicillin,piperacillin,sulfamethoxazole,moxifloxacin and tetracycline and less than 30.0% strains were resistant to amikacin,ceftazidime,amoxicillin-clavulanic acid,piperacillin-tazobactam and colistin.All of the strains were susceptible to imipenem and meropenem.The result of SPSS analysis shows that,in addition to imipenem,meropenem and tetracycline,the resistance rate of the isolates in Henan was higher than that in Jilin,and the detection rate of ESBLs strains in Henan(87.0%)was much higher than that in Jilin(33.3%).By detecting the resistant genes of ESBLs strains,bla CTX-M-1G and bla CTX-M-9G were found in these two regions.bla CTX-M-55 and bla CTX-M-65 were the popular genotypes in Henan area,while bla CTX-M-55 and bla CTX-M-14 were the popular genotypes in Jilin.The detection rates of bla TEM-1?bla OXA-1?MCR-1?aac(6')-Ib-cr and bla OXA-10 of the isolates from Henan were all higher than that in Jilin except for oqx AB and qnr S genes.Besides,qnr B and qeq A were only detected in Henan,while bla CTX-M-2G?bla SHV?qnr A?qnr C and qnr D were not detected both in Henan and Jilin.Conjugation experiments were conducted with 102 ESBLs strains,67 conjugants were obtained finally.It indicated that most of the bla CTX-M(bla CTX-M-1G subgroup and bla CTX-M-9G subgroup)of the donor strains located on the conjugative plasmid.All of the conjugants were multi-drug resistant strains that illustrated multidrug resistance genes were co-transferred with conjugative plasmid.Resistant phenotype of cefazolin,ampicillin,piperacillin,amikacin,gentamicin,tetracycline,chloramphenicol,moxifloxacin,colistin,sulfamethoxazole,ciprofloxacin and levofloxacin were co-transferred with cefotaxime resistant phenotype.In addition to the other ?-lactams antibiotic resistant phenotype,resistant phenotype of amikacin and gentamicin which belong to aminoglycoside antibiotic had the higher frequency to co-transferred with cefotaxime resistant phenotype.The results of this study showed that there was a correlation between virulence genes(EAST1 and irp-2)and bacterial drug resistance.Conjugative plasmids play an important role in the horizontal transmission of virulence genes and resistance genes.