Comparative in vitro analysis of sulbactam-durlobactam against extensively drug resistant (XDR) and non-XDR carbapenem-resistant Acinetobacter baumannii (CRAB) clinical isolates collected from a tertiary care facility in North India.

This study aimed to evaluate the in vitro activity of sulbactam-durlobactam (SUL-DUR), a novel β-lactam/β-lactamase inhibitor combination, against carbapenem-resistant Acinetobacter baumannii (CRAB) clinical isolates from a tertiary care facility in north India. Special focus was placed on extensively drug-resistant (XDR) strains, a subgroup which is likely to be underrepresented in global surveillance.A total of 100 non-duplicate CRAB clinical isolates were included in the study. Isolates were obtained from various clinical specimens, primarily respiratory samples, and characterized using MALDI-TOF MS. Susceptibility testing for SUL-DUR was performed using both broth microdilution (BMD) and disk diffusion (DD) in accordance with CLSI M100, 35th edition guidelines. Quality control was ensured using A. baumannii NCTC 13304 strain. Descriptive analysis and categorical interpretations were employed to evaluate susceptibility patterns. Of the 100 CRAB isolates, 80% were classified as XDR. Overall, 52% of isolates were susceptible to SUL-DUR, 46% resistant, and 2% intermediate. Among XDR strains, susceptibility dropped to 40%. Respiratory isolates, particularly from endotracheal aspirates and bronchoalveolar lavage, exhibited higher resistance rates. All non-XDR isolates (n=20) were susceptible to SUL-DUR. BMD and DD methods showed 100% categorical agreement. The MIC distribution ranged from≤0.25 to ≥128 µg/mL.SUL-DUR showed promising in vitro activity against CRAB, but with reduced efficacy in XDR strains, particularly respiratory isolates. High concordance between BMD and DD supports the utility of disk diffusion in resource-limited settings.