INTRODUCTION:
Antimicrobial resistance (AMR) is a major global health challenge, causing an estimated 1.27 million deaths annually.¹ Urban backyard poultry systems create complex ecological interfaces where poultry, rodents, and contaminated environments interact. Rodents may act as bridging hosts for resistant pathogens, linking environmental reservoirs and poultry.² Understanding these transmission dynamics is critical for designing effective One Health interventions.

METHODS:
A cross-sectional study was conducted across 80 households in Harare. Samples (n=320) included cloacal swabs from poultry, faecal samples from rodents and humans, and environmental samples from poultry house effluent water. E. coli isolates identified using morphological and biochemical testing underwent antimicrobial susceptibility testing using agar diffusion method following CLSI guidelines. Similarities in antimicrobial resistance profiles were assessed using Jaccard similarity indices to infer potential transmission pathways within and between households.

RESULTS:
Of 304 bacterial isolates, Extended-Spectrum Beta-Lactamases (ESBLs)/ AmpC Beta-Lactamases - producing E. coli predominated in poultry (79.3%) and rodents (82%), with environmental isolates showing 100% multidrug resistance. Human rectal swab samples exhibited markedly lower resistance (≤16%). The Jaccard similarity revealed strong local connectivity among non-human compartments: environment–rodent (0.75), poultry–rodent (0.76), and environment–poultry (0.78) within households, compared to weaker between-household links. Human-animal/environment similarities were minimal (≤0.15), suggesting limited direct zoonotic transmission. These results indicate that AMR in Harare backyard poultry settings circulates primarily through environmental contamination and rodent-poultry interactions rather than direct human exposure.

CONCLUSIONS:
Rodents may play an important role in sustaining AMR cycles between poultry and contaminated environments in urban backyard systems. Further genomic analysis is needed to confirm whether identical bacterial strains or resistance genes occur across rodents, poultry, and environmental samples, showing if observed similarities indicate real transmission rather than coincidence. Nevertheless, the observed resistance profile similarities highlight the need for integrated One Health interventions that include rodent control alongside poultry biosecurity and urban waste management.