Molecular ecology of highest priority critically important antibiotic resistant Escherichia coli from mammals housed at an urban zoo.

This article focuses on the molecular ecology of antibiotic resistant (ABR) Escherichia coli in mammals housed at Bristol Zoological Gardens, the world's oldest provincial zoo located in an urban residential district. Over three months, faecal samples from 28 mammalian species revealed high prevalence of E. coli resistant to third-generation cephalosporins (3GC-R) and fluoroquinolones (FQ-R), with multiple sequence types and resistance mechanisms identified, including plasmid-mediated genes such as blaCTX-M-15, blaCMY-2, and the carbapenemase blaOXA-181. Phylogenetic analysis indicated ongoing circulation and transmission of ABR E. coli within the zoo but no evidence of these resistant strains spreading to humans, cattle, or dogs in the surrounding 50 × 50 km region. The study also linked extensive use of amoxicillin/clavulanate in the zoo to the selection of diverse resistance mechanisms, highlighting the zoo as a contained environment fostering ABR E. coli diversity without apparent external dissemination.