LAUSR

ABSTRACT Background Proteus mirabilis is a common opportunistic zoonotic pathogen frequently linked to a wide range of human infections acquired in the community and hospital‐acquired infections. The emergence of antimicrobial resistance in P. mirabilis, largely driven by antibiotic overuse in both human and veterinary medicine, poses a growing global concern. This study aimed to investigate the association between biofilm formation, virulence gene expression and antibiotic resistance in P. mirabilis isolates collected from broiler chickens. Methods A total of 50 isolates were confirmed as P. mirabilis from faecal and tissue samples of 100 broiler chickens by polymerase chain reaction (PCR). Antibacterial susceptibility was evaluated by the disc diffusion method, and nine virulence genes were screened by PCR. We also assessed the biofilm formation capability of the isolates using the crystal violet staining technique. Results Among the 50 P. mirabilis isolates, the highest antimicrobial resistance was observed against chloramphenicol and trimethoprim/sulfamethoxazole (60%), whereas all isolates were fully susceptible to meropenem and cefepime. Multidrug resistance (MDR) was detected in 36% of isolates. Biofilm formation was demonstrated in 88% (n = 44) of isolates, with 74% exhibiting strong biofilm‐forming capacity. All isolates harboured ireA, pmfA, atfA, zapA, hpmA and ptA virulence genes, whereas ucaA was detected in 36% (n = 18) of isolates and mrpA was absent. The virulence gene zapA was significantly more prevalent in biofilm‐producing isolates compared to non‐biofilm producers (p ≤ 0.05). Conclusion Poultry farms may represent an important reservoir of antimicrobial‐resistant P. mirabilis. Our findings underscore the need for responsible antimicrobial stewardship in veterinary medicine, particularly regarding agents critically important for human health, such as cephalosporins, fluoroquinolones, carbapenems.