Antimicrobial resistance patterns and risk factors for cloacal Escherichia coli in chickens in central Tanzania

Antimicrobial resistance is a serious and escalating threat to global health. This study established a baseline antimicrobial resistance profile and prevalence for cloacal Escherichia coli in chickens in central Tanzania. Animal husbandry practices, flock size, and chicken breed were recorded for risk factor evaluation to elucidate potential drivers of resistance across populations. Cloacal samples were collected from poultry in Iringa, Tanzania, and E. coli isolates cultured were then tested for susceptibility to seven medically important antimicrobial drugs: ampicillin, amoxicillin-clavulanate, cefoxitin, enrofloxacin, gentamicin, sulfamethoxazole-trimethoprim, and tetracycline using the Kirby-Bauer disk diffusion method. Over 94% of the 59 E. coli isolates tested were resistant to at least one antimicrobial drug, and over 61% of isolates were resistant to three or more classes of antimicrobial drugs. The highest prevalence of resistance found was to tetracycline and sulfamethoxazole-trimethoprim (88% and 86%, respectively), which were used regularly on many sampled chickens. Previous antimicrobial usage emerged as the only significant risk factor associated with increased detection of multi-drug resistant E. coli. Further surveillance and educational outreach about antimicrobial resistance and stewardship is recommended to reduce antimicrobial drug use and to limit the potential spread of resistance to antimicrobial drugs in Tanzania.