High Levels of Antimicrobial Resistance in Escherichia coli Isolated from Bovans Breeder Hens in Tecamachalco, Puebla, Mexico

Abstract

Antimicrobial resistance in Escherichia coli constitutes a critical problem for public health and animal health worldwide. In poultry production, avian pathogenic strains (APEC) cause colibacillosis, generating significant economic losses. The objective of the present study was to determine the antimicrobial resistance profile of E. coli isolated from Bovans breeder hens on a farm in Tecamachalco, Puebla, during 2025. A total of 52 isolates from birds showing clinical signs and lesions consistent with colibacillosis were analyzed. Bacterial identification was performed using biochemical tests, and antimicrobial susceptibility was assessed using the disk diffusion method (Kirby–Bauer), according to the guidelines of the Clinical and Laboratory Standards Institute (CLSI). High levels of resistance were observed to fluoroquinolones such as ciprofloxacin (92%), enrofloxacin (96%), and norfloxacin (84%), as well as to sulfonamides (sulfamethoxazole + trimethoprim, 86%) and gentamicin (86%). Fosfomycin showed greater sensitivity (68%). The results demonstrate the presence of multidrug-resistant strains, representing a significant risk to poultry production and public health.