Carbapenem Resistance Mediated by Oxacillinases and Metallo-β-Lactamases in Acinetobacter baumannii Isolated From Patients in Critical Care Units.

Introduction Acinetobacter baumannii (A. baumannii) is a multidrug-resistant (MDR) pathogen that causes nosocomial infections, especially in ICU settings. Carbapenem resistance among A. baumannii occurs due to the production of metallo-β-lactamases (MBLs) and OXA-carbapenemases. This study was undertaken to detect the presence of OXA-carbapenemase and MBL by phenotypic and genotypic methods. Materials and methods This in vitro, laboratory-based prospective study was conducted on 190 isolates collected from the clinical microbiology division of a 1,600-bed university teaching hospital from August 2023 to August 2024. Results A total of 190 isolates were obtained from the ICUs. The majority of these were isolated from respiratory secretions (77). Carbapenem resistance was detected in 161 isolates. All the carbapenem-resistant isolates exhibited positive Modified Hodge test (MHT) results, while 147 isolates were MBL screen test positive. Among the blaOXA genes, the bla OXA-23-like gene was predominantly detected (43); in combination with bla OXA-51-like, it was detected in 77 isolates. The bla OXA-24-like gene was not detected in this study. Among the MBL genes, bla NDM was detected in the majority of isolates (12). Fourteen isolates did not harbor any of the genes looked for in the study. Conclusion The increase in carbapenem resistance in A. baumannii infections limits the clinical efficacy of antibiotics used in treatment. Therefore, these infections are a significant threat in hospital settings.