Phenotypical and Molecular Characterization of Acinetobacter baumannii Isolated from Hospitalized Patients During the COVID-19 Pandemic in Brazil

The goal of the present study was to analyze <i>Acinetobacter baumannii</i> strains isolated from hospitalized patients in the period of the COVID-19 pandemic by phenotypic and molecular methods and evaluate their antimicrobial resistance patterns and biofilm production. Forty-seven strains were isolated in 2021-2022 from a hospital in Brazil, and were identified by VITEK^®2, MALDI-TOF/MS (VITEK MS^® and MALDI Biotyper^®), and 16S rRNA sequencing. Fourier-transform infrared (FTIR) spectroscopy was applied for typing and antimicrobial susceptibility testing (AST). In addition, biofilm formation and disinfectant tolerance tests were used. All methods accurately identified all the <i>A. baumannii</i> strains. FTIR typing identified 23 different profiles and 11 clusters, as well as differentiated between the strains from patients with and without COVID-19. Most strains exhibited resistance to the drugs tested, 91.5% of the strains were classified as XDR, 6.4% of the strains were MDR and only 1 strain was classified as non-MDR. Over half of the strains (n = 27, 57.4%) produced biofilms on polystyrene. Sodium hypochlorite (1.0%/15 min) was the best option for effective disinfection. Overall, this study will lay the foundation for further research on effective cleaning protocols for the eradication of <i>A. baumannii</i> biofilms, as well as the use of FTIR for pathogen surveillance in healthcare settings.