Background and Aim: Acinetobacter (A.) baumannii is an opportunistic pathogen in humans, affecting immunocompromised patients and is becoming increasingly important as a hospital-acquired infection. These strains exhibit resistance to essential current antibiotics, posing a real health threat worldwide. The aim of this study was to investigate the relationship between biofilm formation and antibiotic resistance in clinical Acinetobacter baumannii isolates. Materials and Methods: A total of 40 clinical isolates were collected from Iranian hospitalized patients. Disk diffusion method was performed to assess the antimicrobial resistance. Crystal violet staining was used to assess the biofilm-forming ability and polymerase chain reaction (PCR) was employed to determine the frequency of biofilm-related genes (bfmR, bfmS, pgaA, bap, ompA, csuE, and abaI). The relationship between biofilm-forming ability and resistance to antibiotics was statistically analyzed using Fisher's exact test and P≤0.05 was considered significant. Results: All A. baumannii isolates were multidrug-resistant (MDR). The frequency of extensively drug-resistant (XDR) was 80%, and the rest were pan-drug-resistant (PDR). Most of the MDR isolates (85%) were strong biofilm formers, and the rest of them were moderate biofilm formers. All PDRs and 81.25% of XDRs formed strong biofilms. The bfmR, bfmS, pgaA, bap, and ompA genes were existed in all MDRs. The csuE and abaI genes were detected in 97.5% and 82.5% of MDRs, respectively. All XDRs carried csuE gene, and 90.62% possessed abaI gene. Among PDR isolates, 87.5% presented csuE gene, and 50% exhibited abaI gene. Conclusion: The presence of biofilm-forming genes may be related to antibiotic resistance in clinical A. baumannii isolates, although a clone of PDR is evolving with strong biofilm-forming ability and lacking abaI gene.
