Antibiotic-resistant Salmonella species and Escherichia coli in broiler chickens from farms, abattoirs and open markets in selected districts of Zambia

Salmonella species and Escherichia coli are major bacterial enteropathogens of global public health importance that cause foodborne diseases, thereby contributing to increased human morbidity and mortality. Both pathogens have also been found to contribute towards the spread of antimicrobial resistance through the food chain, especially in poultry. The aim of this study was to determine the occurrence of antibiotic-resistant Salmonella sp . and E. coli in broiler chickens at farm level, abattoirs and open markets in selected districts of Zambia. A cross-sectional study was undertaken in seven districts of Zambia to determine the resistance profiles of Salmonella sp . and E. coli obtained from broiler chickens at farms, abattoirs and open markets. A total of 470 samples were collected, including litter, cloacal swabs and carcass swabs. Samples were inoculated into buffered peptone water, sub-cultured onto MacConkey and Xylose Lysine Deoxycholate agar plates. Identification of Salmonella sp. and E. coli was done using the API-20E kit and confirmation by 16S rDNA sequencing. Confirmed isolates were tested against a panel of 10 antibiotics using the Kirby-Bauer disc-diffusion method and interpreted according to the Clinical Laboratory Standards Institute guidelines. Analysis of the antibiotic susceptibility test results was done using WHONET 2018 software. Overall, 4 Salmonella spp . and 280 E. coli were isolated. One of the Salmonella sp . was resistant to ampicillin (25%), amoxicillin/clavulanic acid (25%) and cefotaxime (25%). E. coli antibiotic resistance was highest to tetracycline (81.4%) and lowest to imipenem (0.7%). The antibiotic susceptibility profile revealed 55% (154/280) multidrug resistant E. coli , with the highest multidrug resistance profile (20.7%) in the ampicillin-tetracycline-trimethoprim/sulfamethoxazole drug combination. Furthermore, 4.3% (12/280) of the isolates showed Extensive Drug resistance. The levels of antimicrobial resistance to E. coli and Salmonella observed in market-ready chickens is of public health concern.