Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 17 1 2025 02 05 80 91 Nafiseh Hosseinzadeh Shakib Department of Bacteriology and Virology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran; Student Research Committee, Shiraz University of Medical Sciences, Shiraz, Iran Zahra Hashemizadeh Department of Bacteriology and Virology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran Abolfazl Rafati Zomorodi Department of Bacteriology and Virology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran; Student Research Committee, Shiraz University of Medical Sciences, Shiraz, Iran Reza Khashei Department of Bacteriology and Virology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran; Department of Microbiology, School of Medicine, Sabzevar University of Medical Sciences, Sabzevar, Iran Yeganeh Sadeghi Department of Bacteriology and Virology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran Abdollah Bazargani Department of Bacteriology and Virology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran 2024 05 20 2024 11 03 Background and Objectives: Increasing antimicrobial resistance among Acinetobacter baumannii (A. baumannii) strains poses a significant challenge, particularly in intensive care units (ICUs) where these bacteria are common causes of hospital infections. Biofilm production is recognized as a key mechanism contributing to this resistance. This study aims to explore the relationship between biofilm production, the presence of biofilm-associated genes, and antibiotic resistance patterns in A. baumannii isolates obtained from ICU patients. Materials and Methods: We collected 100 A. baumannii isolates from ICU patients at Nemazee Hospital in Shiraz, Iran. Antimicrobial susceptibility testing (AST) was performed using the Kirby-Bauer disk diffusion method, and biofilm production potential was assessed through the tissue culture plate (TCP) method. Additionally, we investigated eleven biofilm-related genes (ompA, bap, csuE, epsA, blaper-1, bfmS, pgaB, csgA, fimH, ptk, and kpsMII) in all isolates using polymerase chain reaction (PCR). The REP-PCR technique was utilized to analyze the genetic relatedness of the isolates (Fig. 4). Results: All isolates displayed multi-drug resistance, with the highest resistance rates observed against ceftazidime, cefotaxime, and trimethoprim/sulfamethoxazole (100%). Gentamicin and amikacin showed the lowest resistance rates at 70% and 84%, respectively. A total of 98% of the isolates were capable of biofilm production, with 32% categorized as strong biofilm producers. The most frequently detected biofilm-associated genes included csuE (99%), bfmS (98%), ompA (97%), and pgaB (89%). Conclusion: Biofilm production significantly contributes to the prevalence of multi-drug resistant A. baumannii strains. It is essential to implement effective antimicrobial stewardship and develop innovative anti-biofilm strategies to address this global health issue. https://ijm.tums.ac.ir/index.php/ijm/article/view/4799 https://ijm.tums.ac.ir/index.php/ijm/article/download/4799/1744