Evaluation of biofilm-related phenotypic and genotypic characteristics in clinical Acinetobacter baumannii isolates from Gorgan, northern Iran

Biofilm formation and antibiotic resistance are key virulence characteristics of Acinetobacter baumannii that contribute to its persistence in hospital environments and the development of nosocomial infections. This study investigated antimicrobial susceptibility, biofilm formation potential, and the distribution of biofilm-associated genes in clinical isolates of A. baumannii . Endotracheal aspirate (ETA) specimens were obtained from intensive care unit (ICU) and subjected to microbiological culture for identification of A. baumannii . Isolates underwent testing for antimicrobial susceptibility, biofilm formation capacity, twitching motility, and the presence of the biofilm-associated genes. A total of 108 A. baumannii isolates were identified. All isolates exhibited multidrug resistance (MDR), and 98.1% were extensively drug-resistant (XDR). Eighty-seven (80.6%) isolates produced biofilm, including 27.8% strong-biofilm producers, 28.7% moderate-biofilm producers, and 24% weak-biofilm producers. No significant correlation was found between biofilm formation and resistance profiles or MDR/XDR phenotypes. The frequency of twitching motility phenotype was 34.2%. The most prevalent biofilm-related gene was bap (100%), followed by csuE (96.3%), bfmS (90.7%), bfmR (72.2%), ompA (52.7%), pilA (18.5%), and epsA (16.6%). All isolates carried more than three genes simultaneously. A significant relationship was not found between biofilm formation ability and the persence of biofilm-associated genes among A. baumannii isolates. The study demonstrated the high prevalence of MDR and XDR A. baumannii isolates capable of biofilm formation and highlighted the ongoing challenge of treating infections in intensive care settings. The lack of association between biofilm formation, gene presence, and resistance patterns suggests that additional factors influence the pathogenicity and antibiotic tolerance of A. baumannii .