Biofilm Formation, Genetic Determinants, and Antibiotic Resistance in Clinical Isolates of Acinetobacter baumannii

Background: Acinetobacter baumannii is a multidrug-resistant nosocomial pathogen that causes biofilm formation and contributes to persistent infections and challenges in treatment. The interplay between biofilm-associated genes and antibiotic resistance is critical for understanding their clinical impact. The aim of this study was to investigate the biofilm-forming capacity, prevalence of biofilm-related genes (ompA, csuE, bap, bla~PER-1~, cpaA), and antibiotic resistance profiles of clinical A. baumannii isolates. Materials and methods: This cross-sectional study were performed on 125 clinical specimens from Babylon and Al-Najaf hospitals (August–November, 2024). A. baumannii isolates (n=50) were identified using Vitek2 and biochemical tests. Antibiotic susceptibility was assessed using disc diffusion (CLSI 2024 guidelines). Biofilm formation was quantified using the tissue culture plate (TCP) method, and biofilm-related genes were detected by PCR. Resuls: Among 50 A. baumannii isolates, 62% exhibited strong biofilm formation, correlated significantly with extensively drug-resistant (XDR) phenotypes (67%, p=0.009). High resistance rates were observed to carbapenems (imipenem, 90%), cephalosporins (ceftazidime, 96%), and aminoglycosides (amikacin, 76%). PCR revealed high prevalence of ompA (86%) and csuE (86%), whereas bap and bla~PER-1~ were detected in 41.8% and 20.9% of isolates, respectively. XDR strains (62%) dominated by multidrug-resistant (MDR) isolates (38%). Conclusion: Biofilm formation in A. baumannii is strongly associated with XDR phenotypes and the presence of the ompA and csuE genes. These findings underscore the role of biofilm-related genes in exacerbating antibiotic resistance, which poses a significant challenge in clinical management. Enhanced surveillance and targeted interventions are urgently needed to mitigate nosocomial outbreaks.