Multidrug-resistant Escherichia coli isolated from cleaned and disinfected poultry houses prior to day-old chick placement.

The control and elimination of multidrug-resistant (MDR) Escherichia coli is an important challenge in the poultry industry. The aim of this study was to investigate the presence of MDR E. coli in cleaned and disinfected poultry houses before day-old chick placement to identify potential flock colonization sources. In this study, a total of 104 swab samples, collected from 104 cleaned and disinfected poultry houses, were analyzed for the presence of E. coli. Antimicrobial susceptibility profiles of E. coli isolates were determined using the disk diffusion method. Screening for extended-spectrum β-lactamases-encoding genes was performed by polymerase chain reaction and Sanger sequencing. Out of the 104 samples analyzed, 92 (88.46%) were found to be colonized with E. coli. At least one poultry house per farm was found positive for the presence of E. coli, and one isolate per positive shed was subjected to antibiotic susceptibility testing. All isolates displayed high resistance rates to most of the antimicrobial agents tested, including commonly used frontline antibiotics in Algeria. All E. coli isolates (100%) exhibited MDR profiles. A single house on four different broiler farms was found to be contaminated with CTX-M-1-producing E. coli. This study suggests the need for the adoption of strict biosecurity measures and the implementation of improved or novel disinfection procedures in all the poultry houses, in order to avoid cross-contamination of day-old chicks by MDR E. coli.