Antimicrobial resistance of non-clinical Escherichia coli strains from chicken in Nsukka, South-east Nigeria

This study was carried out to determine resistance profiles of Escherichia coli strains isolated from clinically healthy chickens in Nsukka, southeast Nigeria. A total of 324 E. coli strains isolated from cloaca swabs from 390 chickens were tested against 16 antimicrobial agents using the disc diffusion method. The antibiotics used in the study were: ampicillin (25µg), amoxycillin-clavulanic acid (30µg), gentamicin (10µg), streptomycin (30µg), cefuroxime (20µg), cephalexin (10µg), nalidixic acid (30µg), ciprofloxacin (5µg), norfloxacin (10µg), ofloxacin (5µg), pefloxacin (5µg), tetracycline (30µg), chloramphenicol (10µg), cotrimoxazole (50µg), colistin (25µg) and nitrofurantoin (100µg). The strains demonstrated high rates of resistance (34.6% – 66.1%) to ampicillin, tetracycline, nitrofurantoin, cefuroxime and cotrimoxazole. None of the isolates was resistant to colistin, ofloxacin and pefloxacin. For each antimicrobial agent (except cephalexin), strains from the intensively reared chickens (layers and broilers) displayed higher resistance frequencies than those from the local birds. A total of 49 resistant patterns were recorded for the 228 strains resistant to at least one antimicrobial drug, with AmTeCoS and AmTeCfN being the predominant patterns. Because of the great variation in the drug resistance patterns of the Esherichia coli strains, use of antimicrobial agents in the management of E. coli infections in the study area should be based on results of sensitivity tests. Keywords: Antimicrobial, resistance, patterns, Escherichia coli, chicken.