Antimicrobial Susceptibility Patterns and Conjugation Characteristics of Escherichia Coli Isolates from Broiler and Indigenous Chicken in Kericho County, Kenya
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Improper use of antibiotics is a leading factor in promoting emergence, selection and dissemination of drug resistance in human/veterinary medicine. Resistant pathogens can spread to the public through food and environmental routes. Resistance genes are transferable between bacteria. The aim of the study was to determine antibiotic resistance profile of E. coli from rectal swabs of chicken and conjugation characteristics of strains resistant two or more classes of antibiotics. Seven hundred and ten fecal samples were collected from broiler and indigenous chicken from randomly selected farms and inoculated on MacConkey agar. Typical Escherichia coli-like colonies were identified and confirmed using IMViC test and lauryl tryptose mannitol broth. E. coli were exposed to a panel of 20 antibiotics on Mueller-Hinton agar (Oxoid, UK). Inhibition sizes were measured, recorded and resistance profiles studied. Conjugations tests were done on MDR E. coli. Plasmids were extracted using alkaline lysis method and electrophoresis done. Of 710 chicken (broilers, 45.6%; indigenous, 54.4%) sampled, 65.8 %( n=467) harbored E. coli. Overall resistance rates of E. coli were highest against penicillin (92.7%), tetracycline (68.1%) and ampicillin (66.8%). Plasmids containing resistance genes were transferable. Plasmids of varying molecular weight (147kb up to 3.0kb) were common. Prevalence of resistance decreased with increase in bird age in isolates from broiler whereas the trend was opposite for indigenous chicken. In conclusion, there was high resistance to commonly used antibiotics. No significant difference in the rates of antibiotic resistance by isolates from broiler and indigenous chicken noted. Resistance in E. coli decreased with increase in the age of broiler chicken while the opposite was in those from indigenous. Plasmids were transferrable pointing to similar transfers in natural settings. No correlation between rate of resistance and number of plasmids, whereas a positive correlation between rate of resistance and size of plasmid band was found.