Molecular Characterization and Microscopic Analysis of Biofilms in Clinical Isolates of Acinetobacter baumannii

Nosocomial infections are a major health problem worldwide. The increasing time patients spend in hospitals has led to an increase in mortality. Acinetobacter baumannii is an opportunistic pathogen that is a significant factor in nosocomial infections. The main aim of the current study was to investigate biofilm and pathogenicity-related genes among multidrug-resistant A. baumannii strains (n = 54) obtained from patients with respiratory infections. ERIC-PCR was also used to determine their molecular typing correlation. Disk diffusion and MIC methods were used to test antibiotic susceptibility. Biofilm formation was evaluated using crystal violet staining and SEM imaging. In this study, 96.30% of isolates formed biofilms, and 59.25% were strong biofilm producers. The most prevalent biofilm-related genes were pgaC (98.15%), pgaB (92.6%), and pgaA (79.6%), followed by epsA and ompA (74.1%). The isolates demonstrated high resistance to imipenem (100%), cefotaxime (98.15%), followed by cefepime, ceftazidime, levofloxacin, and piperacillin/tazobactam (96.3%). The presence of antibiotic-resistant genes was as follows: bla_OXA-58 (20.4%), bla_OXA-23 (5.55%), aacC1 (50.0%), aphA6 (45.45%), sulⅡ (63.25%), and sulⅠ (32.65%). The sulⅢ gene was not detected. A dendrogram based on UPGMA revealed significant genetic diversity among the 54 A. baumannii strains. Twenty-two ERIC types were identified, with 14 unique types and 8 common types. This study illuminates a concerning rise in antibiotic resistance and the widespread presence of resistance genes in A. baumannii strains. Furthermore, the high ability of these isolates to form biofilms likely contributes to their enhanced resistance, further complicating eradication efforts. Molecular typing demonstrated considerable genetic diversity.