Characterization of Antimicrobial Resistant Salmonella and Escherichia Coli in retail Broiler Chickens in Lusaka province of Zambia

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Muligisa-Muonga, Elizabeth
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University of Zambia
The steady increase in the demand for poultry in Zambia and the world over has put a strain on poultry producers leading to the introduction of new practices such as the use of antibiotics in order to boost production. However, in many resource poor countries, the use of these antibiotics is often not monitored. When antibiotics are misused it can result in the emergence of antibiotic resistance in organisms that could find their way into poultry meat such as Salmonella and Escherichia coli (E. coli). These organisms, as well as others, that could be found in poultry meat, form a reservoir of Antimicrobial Resistant Genes that can be spread from one bacterium to another through horizontal gene transfer, whether pathogenic, commensal or environmental in nature. This spread is facilitated by cross-contamination of the poultry meat when in contact with other surfaces or products. A cross-sectional study was undertaken at the retail level in four districts of Lusaka province (Lusaka, Chilanga, Chongwe and Kafue) in order to determine the proportion of antimicrobial resistant Salmonella and E. coli from retail broiler chickens and to determine the genes that confer the resistance. Sampling was done between January and May 2018. A total of 250 whole broiler carcasses were purchased from 26 open markets (n=134) and 37 supermarkets (n=116). An open market was defined as an unrestricted competitive market in which any buyer and seller is free to participate, while a supermarket was defined as a self-service shop offering a wide variety of food and household products organized into aisles. Upon purchase, all samples were transported in a cooler box containing ice packs to the UNZA Veterinary Public Health Laboratory. Laboratory isolation included a whole carcass rinse in buffered peptone water (Oxoid), pre-enrichment and subsequent incubation at 37OC overnight. Ten microliter (10µL) of the incubated broth was then transferred to MacConkey agar (Oxoid UK) for E. coli isolation while 1ml was also transferred to Rappaport Vassiliadis (Oxoid UK) and later subcultured on Xylose-Lysine Deoxycholate agar (Oxoid UK) for isolation of Salmonella. Biochemical tests were performed on all suspected isolates using Analytical Profile Index (API 20E) (Biomerieux®). Further identification of the isolates was done using 16S rRNA sequencing for bacteria and Antimicrobial susceptibility tests were performed using the Kirby Bauer disk diffusion technique using a panel of 10 different antibiotics. The panel of antibiotics comprised of Ampicillin (10µg), Amoxicillin/Clavulanic acid (30µg), Imipenem (10µg), Nalidixic acid (30µg), Ciprofloxacin (5µg), Trimethoprim/Sulfamethoxazole (25µg), Colistin (10µg), Chloramphenicol (30µg), Tetracycline (30µg) and Cefotaxime (30µg). Analysis of the disk diffusion results was done using WHONET 2018 software. A total of 148 E. coli isolates were identified and subjected to antimicrobial susceptibility testing. Fifty three percent (53%) (n=79) of the isolates were from Open markets while 47% (n=69) were from Supermarkets. Tetracycline recorded the highest resistance of 76.4%, followed by Ampicillin 51.4%, Trimethoprim Sulphamethoxazole 44.6%, Nalidixic Acid 23.6%, Chloramphenicol 14.2%, Cefotaxime 12.8%, Ciprofloxacin 8.1%, Amoxicillin/Clavulanic acid 5.4%, Colistin 5.4% and Imipenem 0.7%. FiveSalmonella isolates was recovered and two were resistant to Tetracycline and Ampicillin, but were susceptible to the other eight antimicrobials. The three target genes of resistance were Tet1, Sul1 and CtxM. The resistant isolates had atleast one of these genes encoded in their DNA, with the beta-lactam gene being the highest. This study has demonstrated the presence of resistant E. coli isolates on broiler chicken from both open and supermarkets. Such resistance patterns pose a threat to public health, hence the need to find the predisposing causes. Keywords: Antimicrobial resistance, E. coli, Salmonella, Poultry, Zambia
Antimicrobial resistance , Poultry, Zambia