Antimicrobial resistance profiles of E. coli isolated from pooled samples of Sick, Farm and Market chickens in Nairobi County, Kenya

Abstract

Background: Antimicrobial resistance (AMR) is an emerging global threat to both human and animal health. This is mainly because the same antimicrobial molecules are used for treatment and prophylaxis in both humans and animals; and about 60% of human pathogens are shared with animals. Thus, a “One health” approach towards combating AMR is critical for the prevention and control of AMR. There is, therefore, need for routine surveillance for AMR in both human and veterinary medicine so as to establish the current status and to formulate strategies on its mitigation. While there are some published data from AMR studies and reviews, data on the prevailing situation, especially in animals, is inadequate. This paper reports on AMR profiles of E. coli isolated from chickens in selected parts of Kenya. Methods: In an effort to establish the antimicrobial resistance profile of bacteria isolated from chicken, A cross-sectional study was carried out in Nairobi County, Kenya. Chickens were purposively selected from three sources: 50 from sick chickens brought to the Poultry clinic at the department of Veterinary Pathology, Microbiology and Parasitology, University of Nairobi, for disease diagnosis (post-mortem examination), 50 from a commercial poultry farm in Nairobi, and 72 from a poultry slaughterhouse in Nairobi. The clinical (sick) cases included broilers, layers, indigenous chickens from various farms, suffering from various disease conditions. Samples from which E. coli was isolated, were considered as representative of strains present in other chickens. The commercial farm kept layers under slatted floor (wire mesh) system. Chicken brought to the slaughterhouse were mainly of indigenous type and spent layers,from various parts of Kenya. Cloacal swabs were taken and the samples placed in Stuart’s transport medium and transported to the microbiology laboratory at the department. Isolation of E. coli was done by streak-inoculating swab samples on MacConkey agar (Oxoid Ltd) followed by incubation at 37 o C overnight. Results: E. coli was recovered from 54/172 samples (31.4%). The study showed that E. coli isolates from the chickens were resistant, at varying levels, to some of the tested antimicrobials; particularly to the ones commonly-used, including: Ampicillin (resistance rate of 85.2%), Tetracycline (66.7%), Cotrimoxazole (57.4%) and Streptomycin (40.7%); low resistances were demonstrated with respect to Nalidixic acid at 24.1%; Chloramphenicol at 14.8% (1 isolate). In contrast, high susceptibilities were observed to Amoxicillin and Gentamycin, each at 96.3%. Six (11.1%) of the isolates were resistant to one antimicrobial (Ampicillin) only, and 5 (9.3%) were susceptible to all the 8 antimicrobials tested, while the rest showed variable resistance to multiple antimicrobials, ranging from 2 to 6. The low E. coli recovery of 31.4% (54/172) was contrary to what was expected since E. coli lives as a commensal in both humans and animals and is the most commonly-found bacteria (coprobacteria) in the faeces. However, this less-than-100%-recovery using cloacal swab method has been observed in other studies. This could be due to intermittent shedding of enterobacteria in feces, so if one does not detect the organism with the cloacal-swab method, it does not mean that the animal is completely free of the organism. Conclusion, this study has demonstrated carriage of antimicrobial resistant E. coli in Kenyan chickens; worst-still is the fact that most of them showed multi-resistances ranging from 2 to 6. Evidence of correaltion between antimicrobial usage and development of antibiotic resistant was domenstrated. This information will contribute towards data on current AMR status in bacteria harbored by chickens in Kenya