Associations Between β-Lactamase Types of Acinetobacter Baumannii and Antimicrobial Resistance

Abstract

Background and objective: Acinetobacter baumannii (A. baumannii) is an important nosocomial pathogen that possesses not only intrinsic resistance to many classes of antibiotics, but also is capable to rapidly develop antimicrobial resistance during treatment. The aim of our study was to determine the production of different types of β-lactamases (AmpC, ESBL, KPC) in A. baumannii strains, to evaluate its association with antimicrobial resistance, and to identify the changes in these characteristics after 5 years. Materials and methods: A total of 233 A. baumannii strains were isolated from different clinical specimens of patients treated at the Hospital of Lithuanian University of Health Sciences in 2016–2017 and 2021–2022. All clinical cultures positive for A. baumannii were analyzed. The type of β-lactamase was detected by phenotypic methods using ESBL plus AmpC screen disk tests and the combination meropenem disk test. Results: In 2016–2017 and 2021–2022, all A. baumannii strains were resistant to ciprofloxacin; more than 80% were resistant to carbapenems, piperacillin/tazobactam, gentamicin, and tobramycin. Comparison of two different period showed that the production of two different types of β-lactamases increased more than 5-fold (from 17.7% to 94.2%, p < 0.001), and the production of all three types of β-lactamases, more than 4-fold (from 1.3% to 5.8%, p < 0.001). A. baumannii strains producing two or three types of β-lactamases were more often resistant to tigecycline, tetracycline, and doxycycline than strains producing one type of β-lactamases (p < 0.001). Conclusions: The frequency of isolation of A. baumannii strains producing two or three β-lactamases types and the resistance rates to ampicillin/sulbactam, tigecycline, tetracycline, and doxycycline increased in 2020–2021 as compared with 2016–2017. The production of two or three types of β-lactamases by A. baumannii strains was associated with higher resistance rates to tetracyclines.