Antimicrobial Sensitivity Profile and Biofilm Formation Capacity of Escherichia Coli Strains Isolated from Different Hatcheries in Southern Brazil

ABSTRACT Poultry farming is a key sector of the Brazilian economy, marked by large-scale production. Consumption increased during the SARS-CoV-2 pandemic and due to global pig herd diseases, driven by poultry’s affordability and versatility. However, industry growth has also led to a rise in diseases, including those caused by Escherichia coli. This study evaluated the sensitivity profile of E. coli strains isolated from poultry hatcheries in southern Brazil against selected antimicrobials and two disinfectants (quaternary ammonium and sodium hypochlorite), as well as their biofilm-forming ability. Samples were collected at different stages of fertile egg incubation and identified through conventional bacteriology. E. coli was found in 18% of samples, with 96.74% producing biofilm and all being sensitive to both disinfectants. Antimicrobial resistance was highest for amoxicillin and tetracycline (79.35%), followed by enrofloxacin (69.56%) and kanamycin (26.09%). Multidrug resistance occurred in 53.26% of isolates. These findings underscore the need for standardized tests to monitor biofilm-producing bacteria and their antimicrobial susceptibility in poultry farming.