Post-pandemic molecular epidemiology of β-lactam resistance and biofilm formation in multidrug-resistant Acinetobacter baumannii from a Brazilian tertiary hospital

BackgroundMultidrug-resistant (MDR) Acinetobacter baumannii has emerged as a critical post-pandemic pathogen, combining antimicrobial resistance with biofilm formation, severely complicating infection control. We aimed to characterize the genetic mechanisms of β-lactams resistance and biofilm-forming capacity of MDR A. baumannii isolates from a Brazilian tertiary hospital, in the post-COVID-19 pandemic period.MethodsA. baumannii isolates were collected from various clinical specimens between 2023/2024. Species identification was performed using the Phoenix BD® system. Antimicrobial susceptibility testing was performed by broth microdilution. β-lactamase genes were investigated by PCR, and biofilm formation was quantified using crystal violet assay. Growth kinetics were analyzed spectrophotometrically.ResultsAmong 78 isolates, 98.7 % exhibited MDR profiles while remaining susceptible to colistin. Strong biofilm production occurred in 71.8 % of isolates, particularly from rectal swabs. Dominant resistance genes included blaOXA-23 (66.7 %), blaOXA-24 (19.2 %), and blaOXA-143 (12.9 %), with blaNDM-1 in 3.9 %. Isaba1 was associated with blaOXA-23 (44.2 %) and blaADC (92.3 %). The bap gene was detected in 28.2 % of the isolates, while blaKPC/GES/IMP/SPM/PER-1 were absent. Biofilm-forming groups displayed distinct growth patterns.ConclusionOur study demonstrates that most A. baumannii isolates exhibit MDR profiles and robust biofilm formation. The widespread presence of β-lactamase genes and biofilm-producing strains underscores the necessity for enhanced molecular surveillance and biofilm-focused infection control measures in critical care units. These findings provide valuable insights into the genetic mechanisms driving resistance and biofilm formation in post-pandemic clinical settings. To mitigate the persistence and spread of high-risk MDR clones, hospitals should integrate genetic resistance profiling and biofilm-targeted strategies into infection control protocols.