Detection Of Cephalosporins Resistance Genes Among Pathogenic Escherichia Coli From Broilers

Colibacillosis, a disease infected with Escherichia coli, was detected in varieties oflivestock and poultry, with more susceptible for young animals. This disease commonlycauses severe diarrhea and septicaemia, influences growth and development, and even leadsto death with severe infection, leaving aquaculture facing economic disaster and seriouslyhindering the development of poultry. Currently, controlling colibacillosis mainly usesantibiotics, however, serious drug-resistance of E. coli was induced due to overreliance onantibiotics. To understand resistance and drug-resistant genes against cephalosporin,pathogenic E. coli were isolated and identified from some large-scale broiler farms in Shaanxiprovince, and these isolates were then used for antimicrobial susceptibility test and PCR todetect drug-resistant genes. The research contents and results are as followed:A total of160E. coli isolates were isolated and identified from sickened and diedchicken in some large-scale broiler farms in Yangling and Baoji in Shaanxi province, with108pathogenic E. coli isolates in1-day-old chicks screened by pathogenicity test. The drugsusceptibility against seven β-lactam drugs for chicken-originated pathogenic E. coli isolateswere determined using K-B disk diffusion method, which showed that the drug-resistancerates of chicken-originated pathogenic E. coli isolates were83.3%,18.5%,72.2%,92.6%,88.9%,90.1%and95.7%for cefoperazone, ceftazidime, cefotaxime, cephazolin, ceftriaxone,zinacef and cefalotin, respectively.88.9%of them were resistant to more than three drugs.Four drug-resistant genes of β-lactamase, namely shv, tem, cmy-2and ctx-m, weredetected for108pathogenic E. coli isolates using PCR method, with98.1%and74.1%positive amplifications for tem and ctx-m, respectively, and no amplification for shv andcmy-2gene. The similarities between both tem and ctx-m sequences obtained and thatavailable in GenBank were more than98%.The results in the present study showed that the β-lactam resistance was widely existedin pathogenic E. coli isolated from fast and large broilers in Shaanxi province with mainlymulti-resistance. The detection rates of tem and ctx-m were positive correlation withresistance.