STUDY ON THE GENOTYPIC AND PHENOTYPIC RESISTANCE OF TETRACYCLINE ANTIBIOTIC IN ESCHERICHIA COLI STRAINS ISOLATED FROM FREE RANGING CHICKENS OF ANHUI PROVINCE, CHINA

Abstract

Poultry industry is growing day by day and it is a major and cheap source of animal protein for human beings. Various bacteria cause serious illness and variety of diseases in poultry birds. The use of tetracycline antibiotics has been increased 4 times in recent years to treat such diseases, leading to the development of drug resistant bacteria in veterinary medicine. This study was conducted to evaluate the resistance profile of tetracycline in avian Escherichia coli strains isolated from free ranging chickens of Anhui province, China. For this purpose, disk diffusion method was used to examine the antimicrobial susceptibility of Escherichia coli strains (n=203) against tetracycline, minocycline, and doxycycline. However, PCR analysis was utilized for detection of the tetracycline resistant genes; tetA, tetB, tetC, tetG and tetM. The overall frequency of phenotypic resistance was 29.1%, which was highest to tetracycline (14.3%), followed by minocycline (6.9%), and doxycycline (7.9%). Whereas the genotypic resistance rate was 24.1%, which include 10.3%, 7.9%, 4.4%, 1.0% and 0.5% resistance rate of tetA, tetG, tetC, tetA + tetC + tetG, and tetA + tetC genes, respectively. Conversely, no isolates were positive for the tetB and tetM genes. The rate of phenotypic resistance (29.1%) was almost in line with genotypic resistance rate (24.1%). Our study demonstrates that chickens are not important contributors to bacterial resistance in an extensive farming system. As such, restrictions on the use of antibiotics could prevent the emergence of resistant pathogens. Furthermore, this is first study of the occurrence of antibiotic resistant E. coli strains in free ranging chickens of Anhui province, China.