| Escherichia coli(E.coli),can cause diarrhea,salpingitis,cellulitis,balloon disease,peritonitis and neuroencephalopathy in chickens.Antimicrobial agents are effective for the treatment of infections caused by E.coli.However,due to the unreasonable use and even abuse of antimicrobial agents.Antibiotic resistance in bacteria has become increasingly serious,and drug-resistant strains,especially multidrug-resistant strains,have brought great security risks to public safety.In order to protect the public safety,bacterial resistance monitoring has got an increasing attention in recent years.In this study,the minimal inhibitory concentration(MIC)of 12 antimicrobial agents against 90 E.coli isolates was determined by microbroth dilution method.The drug resistance of 90 Escherichia coli isoaltes was analyzed combined with multilocus sequence typing(MLST).The results displayed that the resistance rates of 90 isolates to doxycycline,amoxicillin,ampicillin and florfenicol were 57.78%,56.67%,55.56% and 54.44% respectively,and the isolates was susceptible to amikacin with a susceptible rate at 86.67%.The results also showed that 15.55%(14/90)of E.coli isolates were susceptible to all antimicrobial agents,21.11%(19 / 90)were non-susceptible to no more than one drug,and 43.33%(39 / 90)were nonsusceptible to at least to six drugs.The results of multilocus sequence typing indicated that there were 41 ST genotypes in 90 isolates,which showed the complexity of E.coli isolates from broilers in Liaoning.ESBLs-producing E.coli isolates were screened by ESBL selective medium,and 55 and 35 isolates were non-ESBLs-producing and ESBLs-producing isolates,respectively.Among the 55 non-ESBLs-producing E.coli isolates,the virulence genes,type I and type II integrase genes and gene cassettes were detected by PCR;the results showed that the detection rates of Ecs3703?Col V?irp2 and fyu A genes were 70.91%,32.73%,14.55% and 14.55%,respectively;the positive rate of type I integrase gene was 25.45%;four gene cassettes were detected,and they were dfr A7,aad A2,aad A5-dfr A17 and aac A4-cat B3-dfr A 17.The whole genome sequencing was selected to detect drug resistance genes and virulence genes among 35 ESBLs-producing isolates.The results indicated that 9 drug-resistant genes were detected,including TEM-1,CTX-M-123,CTX-M-65,CTX-M-14,CTX-M-55,CTX-M-64,OXA-1,OXA-10 and CTX-M-3.The rate for TEM-1 gene was the highest with 51.43%,while CTX-M-123 gene was the lowest detection rate with 2.86%.The detection rates of CTX-M-65,CTX-M-14,CTX-M-55,CTX-M-64,OXA-1,OXA-10 and CTX-M-3 were 14.29%,17.14%,31.43%,14.29%,22.86%,14.29% and 5.71%,respectively.Thirteen gene cassettes were detected,which were APH(3)-IIa,aac(6)-IIb,aac(6)-Ib-cr,APH(4)-?a,AA(c)-?,dfr A12,dfr A1,dfr A14,aad A2,cat I,cat B3,dfr A17,and aad A5.The detection rates of APH(3)-IIa and dfr A14 were the highest with 25.71%,while the detection rates of AA(c)-?,dfr A17 and dfr A1 were the lowest(2.86%).The detection rates of irp2,fyu A and pap C genes all were 11.43%.PCR was used to amplify the type I and type II integrase genes among ESBLs-producing E.coli isolates.Thirty-two isoaltes were positive for type I integrase gene,the detection rate was 91.43%,and 5 strains were positive for type II integrase gene(9.09%).The resistance rates of E.coli from broilers to amikacin and gentamicin were low in Liaoning Province,and the carrying rates of virulence genes Ecs3703?Col V?irp2 and fyu A were high,and the drug-resistant gene TEM-1 of ESBLs-producing E.coli was the highest.The detection of virulence genes and antimciorbial resistance detection of E.coli from broilers in Liaoning,this study will provide a theoretical basis for the rational use of antimicrobial agents in the prevention and treatment of diseases caused by E.coli isolates. |
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