Investigation of Metallo-Beta-Lactamase Production in Carbapenem-resistant Clinical Acinetobacter baumannii Isolates

Introduction: Carbapenem resistance generally emerges from carbapenemase production in Acinetobacter baumannii isolates. It is known that prognosis is adversely affected, and mortality rate increases in infections caused by Metallo-beta-lactamase (MBL) type carbapenemase-producing isolates. This study aimed to investigate MBL production in carbapenem-resistant A. baumannii isolated from inpatients in Kastamonu Training and Research Hospital (TRH), Turkiye. Materials and Methods: A total of 110 non-duplicated carbapenems (imipenem and meropenem) resistant A. baumannii isolates between July 2020 and July 2021 were included in the study. Identification of the isolates was performed by conventional methods, VITEK 2 Compact automated system, and amplification of the OXA-51-like gene region. Antibiotic susceptibility tests were conducted and evaluated with EUCAST criteria using VITEK 2. Carbapenemase production of the isolates was tested using the modified Hodge test. MBL production was screened using imipenem-EDTA double-disc synergy test. The presence of blaIMP, blaVIM, blaGIM, and blaNDM genes was investigated using polymerase chain reaction (PCR) to confirm the MBL production. Results: All isolates were confirmed to be A. baumannii. All isolates were resistant to imipenem, meropenem, ciprofloxacin, and levofloxacin. The susceptibilities to trimethoprim-sulfamethoxazole, tobramycin, amikacin, and gentamicin were 0.9% (n= 1), 1.8% (n= 2), 2.7% (n= 3), and 2.7% (n= 3), respectively. All isolates had carbapenemase activity. However, the MBL phenotype was present in none of the strains. Also, MBL genes were not detected in the isolates. Conclusion: MBL production was not detected in carbapenem-resistant A. baumannii isolates obtained from Kastamonu TRH. Carbapenem resistance in these isolates may be due to the production of non-MBL carbapenemases such as OXA-type carbapenemases.