Background and Objectives: Avian pathogenic Escherichia coli (APEC) is a major cause of colibacillosis in poultry, contributing to systemic disease and economic loss. This study investigated virulence gene profiles, biofilm formation, and antimicrobial and disinfectant resistance in E. coli isolates from broiler chickens in Qazvin, Iran.
Methods: Liver samples were collected from 50 broiler chickens diagnosed with colibacillosis. E. coli isolates were confirmed biochemically. Antibiotic susceptibility was evaluated using the disk diffusion method, and virulence genes were detected via PCR. Biofilm formation was assessed using crystal violet staining. MIC and MBC values for formaldehyde, glutaraldehyde, and hydrogen peroxide were determined using broth microdilution.
Results: Among 50 isolates, 82% exhibited multidrug resistance (MDR) and 30% were ESBL producers. The most frequent gene was iss (66%), and papC was the least common (4%). All isolates formed biofilms, with 72% classified as strong producers. Formaldehyde and hydrogen peroxide exhibited the lowest MIC and MBC values (≤ 0.009%), while glutaraldehyde required higher concentrations for inhibitory and bactericidal activity (0.078%).
Conclusion: High rates of MDR and biofilm formation among APEC isolates highlight the need for effective antimicrobial stewardship and disinfection strategies in poultry production systems.