In vitro evaluation of sulbactam-durlobactam as a therapeutic alternative for multidrug-resistant <i>Acinetobacter baumannii</i> infections: insights from a tertiary care hospital

Abstract Objectives The Acinetobacter baumannii complex (ABC) is a hospital-acquired pathogen that exhibits high resistance, particularly to β-lactam antibiotics. The rise of β-lactamase enzymes, including carbapenemases, limits treatment options. New β-lactam/β-lactamase inhibitor (BL-BLI) combinations show promise, but information on their use in Indian hospitals is inadequate. The current study was designed to investigate the effectiveness of BL-BLI against ABC isolates, assess the impact of co-harboring various resistance genes on antibiotic effectiveness, and map the distribution pattern of these genes in clinical A. baumannii strains obtained from patients admitted at different wards and units of a tertiary care hospital using cluster analysis. Methods For the study, a total of 155 non-repetitive ABC isolates were isolated from specimens (n=9,753) collected from various critical care units and different inpatient departments of a tertiary care hospital. Antimicrobial susceptibility testing was performed on the isolates using Vitek-2 and Kirby-Bauer disc diffusion methods. Conventional PCR was performed to identify β-lactamase genes, including blaCTX-M, blaTEM, blaKPC, blaNDM, blaOXA-48 , and blaOXA-23 . The genetic relationships between ABC and the respective hospital wards from which they were isolated were studied using a dendrogram. Results Among BL-BLI combinations, sulbactam-durlobactam showed the highest effectiveness against blaOXA-23, blaKPC , and blaOXA-48 producing ABCs. However, it had limited activity against blaNDM -positive strains, whether alone or in combination. The PCR results reveal that the most widespread genes were blaOXA-23 (65.1 %) and blaNDM (60 %), respectively. Conclusions The high prevalence of carbapenemase genes in ABC isolates, which underscores the limited effectiveness of newer BL-BLI against NDM-positive strains.