Isolation,Virulence And Drug Resistance Detection Of Escherichia Coli From Chickens In Hebei Province

In order to analyze the serotype,virulence and drug resistance of Escherichia coli isolated from chickens in Hebei,samples were collected for routine bacterial isolation and culture,staining microscopy and PCR for identification.Serotype of isolates was identified by glass plate agglutination test,virulence and drug resistance genes of isolates were detected by PCR.The antibiotics of the isolates were detected by K-B drug sensitive paper method.The research contents and results were as follows:1.Isolation and identification of the strain:In this study,225 dead chicken samples collected were isolated and identified in Hebei Province from 2019 to 2020,181 strains of E.coli were isolated,105 strains of E.coli were isolated from 135samples in 2019,the separation rate was 77.78%.76 strains of E.coli were isolated from 90 samples in 2020,the separation rate was 84.44%.The serotypes of 105strains of E.coli preserved in the laboratory in 2018 and 181 strains isolated and identified during 2019?2020 isolates were identified by glass plate agglutination test,the results showed that O₁,O₂,O₇₈and O₁₄₂were the dominant serotypes in 2018,accounting for 20.95%,15.24%,13.33%and 11.43%,respectively.O₂₆?O₁?O₁₈and O₇₈were the dominant serotypes in 2019,accounting for 18.10%,14.29%,12.38%and 9.52%,respectively.O₇₈,O₂and O₁were the dominant serotypes in 2020,accounting for 22.37%,17.11%and 14.47%,respectively.O₁,O₇₈and O₂were the dominant serotypes in the three years,the total detection rates were 16.78%,14.34%and 12.94%,respectively.2.Virulence gene and pathogenicity were detected:The virulence gene of 286strains of E.coli from 2018 to 2020 was tested.20 virulence genes were detected by PCR.The results showed that 16 virulence genes were detected,the total detection rate was 80%.The detection rates of iut A,Iss,fim C,omp T and hly F were very high in2018,The detection rate between 71.43%and 92.38%,while the detection rate of iut B,ast A,Vat and tsh was low,the detection rate between 29.52%and 47.62%.The detection rates of iut A,iro N,hly F,omp T,Iss,fim C and Ecs3703 were very high in2019,between 83.81%and 96.19%,while the detection rates of Vat,colv,iut B and fyu A were relatively low,with a detection rate of 7.62%?48.57%.The detection rates of hly F,iuc D,Iss,omp T,fim C,iut A and Ecs3737 were very high in 2020,between77.63%and 100%,while the detection rate of Vat,iut B,and colv was low,with the detection rate of 2.63%?42.11%.The detection rates of hly F,omp T,fim C,Iss and iut A were relatively high in three years,and the detection rate was 86.36%?89.86%.The virulence genes of pap C,sfa,Ler and eae A were not detected for three consecutive years.The results of the pathogenicity test showed that the incidence rate of chickens in the attack groups were 100%.The mortality of different groups were 60%?100%,The total mortality was 91.82%.3.Detection of drug-resistance phenotype and drug-resistance gene:The 286strains of E.coli from 2018 to 2020 were all resistant to 24 antibiotics to different degrees.And the 286 strains of E.coli had serious multiple cross resistance.The drug resistance rate to cotrimoxazole,sulfadimethoxine,sulfamono methoxine,oxytetracycline,doxycycline,cefradine,amoxicillin and penicillin were relatively high in 2018,between 72.38%and 98.10%,while the drug resistance rate to ceftiofur,norfloxacin,gentamicin,amikacin and spectinomycin were relatively low,ranging from 15.24%to 39.05%.The drug resistance rate of penicillin,ampicillin,doxycycline,oxytetracycline,sulfadimethoxine,lincomycin,tilmicosin,amoxicillin,cotrimoxazole,ceftiofur,flufenicol and ceftriaxone were high in 2019,the detection rate of 70.48%?99.05%,while the drug resistance rate to gentamicin,spectinomycin,amikacin were low,between 24.76%and 38.10%.In 2020,the resistance rate to lincomycin was as high to 100%,and the drug resistance rate to tilmicosin,sulfadimethoxine,penicillin,oxytetracycline,doxycycline,ampicillin,amoxicillin,sulfamono methoxine were 84.21%?98.68%,while the drug resistance rate to spectinomycin,amicosin,and gentamicin were relatively low,ranging from 9.21%to36.84%.Among them,the drug resistance rates of ceftriaxone,tilmicosin,sulfadimethoxine and lincomycin increased year by year.The most obvious change was tilmicosin.The drug resistance rate increased from 38.10%in 2018 to 98.68%in2020.The resistance rates of gentamicin,spectinomycin,and amikacin were lower than 40%for three consecutive years.40 kinds of drug resistance genes of 286 strains of E.coli were detected by PCR,the results showed that CTX-M,sul-2,aad A1,gyr B,tet(C)were very high in 2018,the detection rate was 75.24%?87.62%;Sul-2?aad A1?gyr B,gyr A,par C were very high in 2019,and the detection rate was 75.24%?96.19%.In 2020,the detection rate of oqx A,gyr A and par C were as high to 100%,the detection rate of Oxa-5,Str B,gyr B,sul-2,aad A1 were very high,and both were more than 78.95%.The total detection rates of gyr B,aad A1,gyr A,par C and sul-2 were85.66%,85.31%,84.62%,81.12%and 79.37%,respectively.