Monitoring the prevalence of the tetracycline efflux genes among E. coli isolated from chicken colibacillosis

BACKGROUND: Avian colibacillosis can lead to important economic losses in the poultry industry. Escherichia coli, the causative agent of this disease has acquired resistance to different antibiotics, including tetracycline. OBJECTIVES: This study was carried out to detect the distribution of tetracycline Group І efflux genes among E.coli isolates from from avian colibacillosis in Iran by PCR assay. METHODS: A total of 50 E. coli isolates from chicken colibacillosis were characterized by cultural, biochemical and PCR methods. Kirby-Bauer disk diffusion method was used to define the resistance of isolates to tetracycline, then the Frequencies of tetracycline resistance genes (tetA, tetB, tetC, tetG, tetH, tetZ and tetE) were also determined using PCR method. RESULTS: According to biochemical and molecular experiments, 50 isolates from 237 chicken samples were recognized as E. coli. Seventy-six (76%) of the isolates, however, were resistant to tetracycline. The distribution of tetracycline-resistance genes among E. coli isolates included tetB (34%), tetA (26%), tetE (16%), tetC (15%), tetH (12%), tetG (12%) and tetZ (6%). CONCLUSIONS: The present study highlights the prevalence of tetracycline resistant E. coli among chickens which is due to extensive use of this antibiotic for growth promotion in poultry industry.