Isolation And Drug Resistance Analysis Of Avian Pathogenic E.coli In Taian, Shandong Province

Avian Colibacillosis is a common epidemic disease in chickens caused by some specific serotype of Escherichia coli(E.coli). It’s one of the main reasons of embryonic death,omphalitis, blood poisoning, perihepatitis, pericarditis, vitelline peritonitis and salpingitis, and brings severe economic loss to poultry industry. Usually, E. coli has resistance against many antibiotics, of which irregular and excessive medication in veterinary clinical further aggravates the development of drug-resistant strains. In the last decades, more and more drug-resistant mutant avian pathogenic E.coli strains had been reported and drug resistance spectra of those strains had been enlarged, even some of those strains could resist new antibiotics which did not widely used in veterinary clinical before, which brought great challenge to the public health.In this study, the epidemiology, drug resistance and drug resistance genes of pathogenic E. coli strains isolated from several enlarged scale chicken farms in Taian, Shandong province were systematically investigated to provide reliable theory basis for the prevention and control of Avian Colibacillosis caused by E. coli in this region. This study includes three parts:Part I: E. coli were isolated from suspected cases collected from 10 chicken farms in Taian, Shandong province during 2013–2014. Bacterial biochemical test showed that 14 strains of avian pathogenic E. coli were isolated. Plate agglutination text was performed to investigate the O serotypes of those strains. Three serotypes(O78, O35, and O1) were identified in them and the most common serotypes were O78(6/14) and O2(6/14), of which occupied 85.71% in all.Part II: In this study, 20 kinds of common antibiotics were used and drug sensitive test was performed to investigate the resistant character of those strains. The result showed that the level of drug resistance was very high and the resistance spectrum was wider in the E. coli strains isolated from other regions. All of those isolated strains had the highly resistant tocephalosporin antibiotics such as cefotaxime, cephalothin, cefuroxime, ceftriaxone and so on.In addition, all of the strains had the highly resistant to gentamicin, streptomycin, amikacin,kanamycin, piperacillin and ampicillin. To those isolates, the most susceptible durg was polymyxin B with the saitivity rate of 100%, cephalosporins with the saitivity rate of 100%and sulfamethoxazole with the saitivity rate of 21.4%.Part III: β-Lactamase resistance genes like TEM, SHV, CTX-M-1, CTX-M-8, 0XA-2,OXA-10 and aminoglycosides resistance genes like ant(3’’)-Ia, acc(6’)-Ib, aph(3’)-IIa, armA,rmtA of the 14 isolated strains were detected by PCR. The results showed that the rate of strains carrying resistance genes was very high. All of the stains carried CTX-M-1 resistance gene and resistance gene acc(6’)-Ib. In addition, nine of the stains carried TEM resistance gene(64.3%), two of them carried aph(3’)-IIa resistance gene(14.3%). All of the results was in accord with those of drug sensitive test, which account for the high drug resistance spectra in the molecular level, and provide theoretical base and scientific foundation for the prevention and control of E. coli.