The Investigation of Beta Lactamase in Carbapenem-Resistant Acinetobacter baumannii Isolates

Abstract

Acinetobacter baumannii is an opportunistic pathogen that causes nosocomial infections and exhibits multiple antimicrobial resistance. Carbapenems are preferred in the treatment. In recent years, increasing resistance to carbapenems has been reported all over the world. The aim of the study is to investigate the presence of carbapenemases in carbapenem-resistant A. baumannii strains by molecular methods.A total of 77 carbapenem-resistant A. baumannii isolates, obtained from blood samples collected from catheter hubs of patients hospitalized in the intensive care unit at Ondokuz Mayıs University Faculty of Medicine between from January 2021 and September 2022, were examined. Bacterial identification used traditional methods alongside VITEK® MS (bioMérieux, France). Antibiotic resistance profiles were determined following EUCAST standards using the Vitek2 Compact automated system. Additionally, multiplex polymerase chain reaction (PCR) was utilized to investigate the presence of blaOXA 23-like, blaOXA 24-like, blaOXA 51-like, and blaOXA 58-like oxacillinase genes, as well as blaNDM, blaVIM, and blaIMP metallo-beta-lactamase genes. While all 77 A. baumannii isolates were resistant to meropenem, 75 isolates were also resistant to imipenem. In addition, all of the isolates were found to be resistant to ceftazidime, levofloxacin, and ciprofloxacin. Sensitivity to amikacin, gentamicin, and trimethoprim-sulfomethoxazole was 29.8%, 6.4%, and 6.4%, respectively. The blaOXA 51-like gene was found in all A. baumannii strains. The blaOXA 23-like gene was detected in 74 (96%) of the strains, and the blaOXA 24-like gene was detected in 16 (20.7%) strains. blaOXA 58-like, blaNDM, blaVIM, and blaIMP genes were not detected positively in any of the isolates. Oxacillinase-type enzymes, notably blaOXA 51-like, blaOXA 23-like, and blaOXA 24-like genes, primarily contribute to carbapenem resistance in A. baumannii isolates. The blaOXA 58-like gene and metallo-betalactamase metallo-beta-lactamase resistance genes were not found in the strains. These obtained data revealed reveals the necessity of molecular methods in defining the epidemiological relationship of isolates. © 2024 Ondokuz Mayis Universitesi. All rights reserved.