Drug resistance among Escherichia coli isolates from typical lesions of poultry colibacillosis and detection of florfenicol (floR, fexA, cfr) and colistin (mcr-1) resistance genes

Escherichia coli is the causative agent of colibacillosis in poultry leading to heavy economic losses and increased antibacterial use in poultry flocks with a consequence of increased drug resistance. In order to reduce drug resistance, as a global problem, and to establish better health among humans, animals and environment, a periodical monitoring of drug resistance rate is required. The aims of this study were to investigate the resistance of Escherichia coli isolates to different antimicrobial agents and also to detect florfenicol (cfr, fexA, floR) and colistin (mcr-1) resistance genes among isolates. One hundred Escherichia coli isolates originated from typical lesions of colibacillosis were collected from poultry referred to a private laboratory in Tehran and University bacterial collection and the drug resistance of isolates to 16 antimicrobial agents including ampicillin, neomycin, gentamicin, enrofloxacin, flumequine, difloxacin, chloramphenicol, florfenicol, Fosbac, erythromycin, colistin, tetracycline, oxytetracycline, trimethoprime+sulfa, linco-spectin and doxycycline was determined by using disk diffusion method. Then, the chromosomal and plasmid DNA were extracted and florfenicol (cfr, fexA, floR) and colistin (mcr-1) resistance genes were detected among all isolates by using polymerase chain reaction test (PCR). Based on antimicrobial susceptibility test, the highest resistance was observed to erythromycin, doxycycline and tetracycline and the lowest resistance rate was found to linco-spectin, gentamicin and Fosbac. All isolates were resistant to at least one and 10% of isolates were resistant to at least 12 antimicrobial agents. The 16% of the isolates belonged to one identical pattern and 35% of isolates each belonged to a separate pattern. Among 85 tested isolates, 40 and 52.94% of the isolates showed floR gene on their plasmid and chromosomal locations, respectively. However, no isolate was positive for fexA, cfr and mcr-1 resistance genes. The findings of this study demonstrated the high frequency of resistance to commonly used antimicrobial agents among E. coli isolated from colibacillosis. Detection of resistance genes increases the researchers’ knowledge on the epidemiology of drug resistance. This information indicates the necessity for implementation of the right management programs for poultry farms and rational antimicrobial therapy besides periodic antimicrobial susceptibility monitoring.