Comparative Analysis of Antimicrobial Susceptibility Profiles of Extended-Spectrum β-Lactamase-Producing <em>Escherichia coli</em> Isolated from Intensively Reared and Free-Range Chickens in Selected Districts of Zambia

This study underscored the public health implications of antibiotic use in poultry pro-duction by evaluating antimicrobial susceptibility of ESBL-producing Escherichia coli isolated from intensively reared and free-range chickens in selected Zambian districts. A cross-sectional study analysed 112 faecal samples (56 from free-range and 56 from in-tensively reared chickens) collected from seven veterinary camps, of which five (5) were from Kabwe and two (2) from Kapiri Mposhi Districts. E. coli from the samples were cultured on MacConkey agar containing Cefotaxime, and analyzed by PCR for the presence of blaCTX-M, blaSHV, and blaTEM resistance genes. ESBL-producing E. coli were found in 11.61% of samples (5.35% free-range; 6.25% intensively reared). Overall, of the thirteen samples that yielded isolates resistant to the panel of antibiotics used, 58.9% of isolates showed resistance to β-lactams and other antibiotics. Chi-Square analysis at α=0.05, revealed no statistically significant difference in the carriage of Extended Beta Lactama-se-producing E. coli between intensively reared and free-range chickens. Both intensively reared and free-range chickens in Zambia harbour ESBL-producing E. coli, indicating widespread antimicrobial resistance. The absence of a statistically significant difference in ESBL producing E. coli between intensive and free-range production systems indicates that free-range birds are comparably exposed to antimicrobial-resistant pathogens. This demonstrates an urgent to reinforce antimicrobial stewardship, implement surveillance strategies, and promote responsible antibiotic use across poultry production systems.