Epidemiological Investigation And Drug Resistance Of Avian Pathogenic Escherichia

1.Isolation and identification of avian pathogenic Escherichia coliDiseased and dead poultry(chickens and ducks)were submitted from facilities in the Jiangsu,Shandong,Zhejiang,Shanghai and Anhui regions from 2007 to 2014.Animal specimens were diagnosed via the clinical presentation with lesions typical of E.coli infections.The livers,spleens and lungs were collected aseptically to serve as diseased tissue sources.Samples of the diseased tissues were used to inoculate MacConkey agar.After growth,the suspect bacterial colonies were used in PCR identification.Strains which were identified by PCR as E.coli were culture identified on triple sugar iron agar and additional identifications were made using glucose,lactose,maltose,mannitol and sucrose fermentation tests.An IMViC test battery was used to confirm these strains as E.coli.The results showed that 189 strains suspected of being E.coli were isolated,120 strains were from chickens and 69 strains were from ducks.PCR and agglutination tests were used to identify the O-serogroup(s)of the 189 isolated strains.PCR genotyping results showed that the serogroups of 175 strains belonging to O78?O2?O18?O88?O9?O24?O38 and O1.The other 14 strains were unserogroupable.Rating the occurrence of serogroups from different sources,the predominant serogroups for chickens were 078 and 088,078 and 018 for ducks.2.Detection of virulence-associated genes of avian pathogenic Escherichia coliPCR primers targeting virulence-associated genes were designed according to the literature for the detection of 12 E.coli virulence genes.PCR were used to identify the virulence-associated genes of the 189 isolated strains.According to the distribution of 12 virulence-associated genes of the 189 strains of APEC isolates,the test results showed that the ompA and fimC genes had detection rates of 98.41%and 95.77%,respectively.The lowest occurrence of virulence genes were papC(5.29%)and hlyE(4.76%).Rates of detection of the remaining 8 virulence genes ranged from 71.96%to 19.58%.These experimental data might provide a reference for the future study of APEC,revealed its pathogenesis,and then put forward effective control measures.3.Drug susceptibility testing of avian pathogenic Escherichia coliTo find out the effect on clinic germ's drug resisitance,referring to the CLSI standard,189 avian pathogenic Escherichia coli isolates were tested antimicrobial resistance to 18 antibiotic.Based on the experimental data of the results of drug sensitivity test,the isolates were generally resistant to antibioticswhich have been clinically applied over a long time span by veterinary specialists.Resistance rates to ampicillin,streptomycin,tetracycline,nalidixic acid,trimethoprim,sulfamethoxazole compounds,and sulfisoxazole were above 60%,but there was a low resistance rate to new antibiotics like cephalosporins(cefotaxime,ceftriaxone,ceftazidime),carbapenems(ertapenem)and monobactam(aztreonam).Among the 189 isolates,146 were multi-drug-resistant(MDR)strains(77.25%).These results indicate that the antibiotic should be reasonablely used to prevention for infection.This is very important to reduce the occurrence of bacterial resistance.