Investigation of antibiotic resistance patterns in Escherichia coli isolated from broiler chickens with colibacillosis to ten antibacterial agents commonly used in the Iranian poultry industry

Colibacillosis is one of the most important of bacterial diseases in poultry industry with huge economic losses that is caused by Escherichia coli. Various antimicrobial agents were used in order to reduce the losses associated with colibacillosis infection. But in recent years, enormous use of antibiotics in poultry medicine has been increased antimicrobial resistance among bacterial strains that lead to reduce efficacy of drugs. The purpose of this study was to determine the Antibiotic resistance rate of 178 E. coli isolated from 40 broiler flocks with clinical signs of colibacillosis in Ardabil province, northwest of Iran. The Antibiotic resistance pattern of isolates to ten antibacterial agents commonly used in the Iranian poultry industry was determined by disc diffusion test. According to the results, resistance rates to tetracycline, erythromycin, trimethoprim - sulphadiazine (sultrim), enrofloxacin, neomycin, danofloxacin, colistin, ampicillin, florfenicol and lincospectine were 99.43%, 97.75%, 80.34%, 77.53%, 75.84%, 69.66%, 68.54%, 60.11%, 58.99% and 36.52%, respectively. There were 51 drug resistance patterns among 178 E. coli isolates to ten antibacterial agents commonly used in the poultry industry that 142 isolates (79.78%) belonged to more than one pattern, whereas 36 isolates (20.22%) each isolate belonged to one pattern only. The results of this study show the high frequency of resistance to antimicrobial agents commonly used in the Iranian poultry industry. So, National monitoring programs is strongly needed for antimicrobial resistance and rational use of antibiotics.