Antimicrobial resistance in Escherichia coli isolates from faeces and carcass samples of slaughtered cattle, swine and chickens in Kenya

Abstract

Two hundred and thirty five Escherichia coli isolates from cattle, pigs and chickens were investigated for their resistance to seven antimicrobials by the disc diffusion method. Minimum inhibitory concentrations were determined for 154 isolates showing resistance to at least one of the antimicrobials tested. Resistance was found in 65.5% and multi-resistance (resistance to = 2 antibiotics) in 37.9% of the isolates. Resistance was highest in the isolates from chickens (74.0%), followed by pigs (64.8%) and cattle (61.3%). The most common resistance was to ampicillin, streptomycin, tetracycline, sulphamethoxazole/trimethoprim, and kanamycin (42.5-11.9%). Resistance to kanamycin, sulphamethoxazole/trimethoprim, and tetracycline was significantly lower in cattle (2.5-7.5%) than in the other species (12.0-40.0%) (p < 0.01). Resistance to streptomycin and ampicillin were significantly higher in cattle and pigs respectively (p < 0.01). Similar resistance rates were observed among the faecal (29.9%) and carcass swab (33.1%) isolates. Forty resistance patterns were recorded of which only 5 (12.5%) were common among the isolates studied. This study shows that multi-drug resistant E. coli isolates are prevalent in cattle, pigs and chickens in Kenya and that a considerable proportion of E. coli isolates from fresh cattle and pig carcasses is resistant to a variety of antimicrobial agents. Differences in the rates and patterns of resistance were noted, perhaps reflecting differences in antibiotic use regimens among these species. It is recommended that the use of antimicrobials in food animals should follow prudent use guidelines to minimize the selection of resistant bacteria and that slaughter hygiene should be improved to minimize the risk of transfer of antimicrobial resistant bacteria to humans.