Determination of Quinolone Resistance in Escherichia coli Isolates

Abstract

Quinolone resistance in 102 isolates of Escherichia coli from faecal samples of asymptomatic cattle and chickens in Anyigba, Kogi State, Nigeria was determined by antimicrobial susceptibility testing and Polymerase Chain Reaction (PCR) with qnrA primers. Susceptibility of the isolates to two quinolones (ciprofloxacin and nalidixic acid) was conducted using the disc diffusion method. Diameter of zones of inhibition around antimicrobial susceptibility discs were measured and interpreted using the Clinical Laboratory Standard Institute (CLSI) measurements. Plasmid and genomic DNA extracted from antimicrobial resistant isolates were subjected to Polymerase Chain Reaction with qnrA primers for DNA hybridization. Antimicrobial resistance (AMR) to ciprofloxacin observed for isolates from cattle faeces and chicken faecal isolates was 10.6% and 58.2% respectively. AMR to nalidixic acid was 12.8% and 60.0% respectively. Intermediate susceptibility of isolates to nalidixic acid is higher than intermediate susceptibility to ciprofloxacin (26.5% and 49.1%). There is an observed significant difference (p<0.05) in the antimicrobial susceptibility of Escherichia coli isolated from cattle faeces and chicken faeces to these quinolones. Conversely, hybridization of qnrA with plasmid DNA or genomic DNA was not detected in the PCR. The results indicated that Escherichia coli isolates from faeces of these animals are more susceptible to ciprofloxacin than nalidixic acid. Higher resistance observed for isolates from chickens could be a result of more exposure to antimicrobials in feed (as growth promoters and prophylactics) and in treatment of infections. Molecular determinant(s) of resistance in the resistant isolates appears to be genes other than qnrA as may be determined in further studies