# Resistance of Acinetobacter baumannii Complex Clinical Isolates to Sulbactam–Durlobactam: A Systematic Review of Data from In Vitro Studies

## TL;DR

This study reviews how resistant Acinetobacter baumannii isolates are to a new antibiotic combination, sulbactam–durlobactam, based on in vitro data.

## Contribution

The study provides a systematic review of resistance data for sulbactam–durlobactam in A. baumannii clinical isolates.

## Key findings

- OXA-23/OXA-23-like β-lactamase genes were most commonly found in resistant isolates.
- Resistance to sulbactam–durlobactam was low in non-selected A. baumannii isolates (1.2–4.6%).
- Non-susceptibility was rare in A. calcoaceticus, A. nosocomialis, and A. pittii isolates.

## Abstract

Introduction: Due to the limited therapeutic options for patients with Acinetobacter baumannii complex infections, a new combination antimicrobial agent, sulbactam–durlobactam, has been developed. In this systematic review, we evaluated the available data on the resistance of A. baumannii complex clinical isolates to sulbactam–durlobactam. Methods: We performed a thorough search of four databases for relevant studies. The Clinical and Laboratory Standards Institute (CLSI) sulbactam–durlobactam breakpoint for A. baumannii complex susceptibility was used (MIC value ≤4 mg/L). Data on the presence of genes of various β-lactamases were also analyzed. Results: From 182 identified articles, 84 were thoroughly screened. Data extraction was performed on 20 articles (published 2017–2025) reporting on a total of 10,412 A. baumannii complex clinical isolates. Among the various β-lactamases genes present, the OXA subvariants OXA-23/OXA-23-like were the most common (in 561 isolates). The proportions of non-selected (consecutive) A. baumannii isolates found to be resistant to sulbactam–durlobactam were 1.2%, 1.2%, and 4.6% in the three studies, and with non-susceptibility (resistance and intermediate resistance) were 2%, 2.1%, and 4.6% in three other studies. Non-susceptibility was very rare among A. calcoaceticus, A. nosocomialis, and A. pittii isolates (0%, 0.3%, and 0.6%, respectively). The proportion of carbapenem-resistant A. baumannii isolates with resistance was 0–5.2%. The proportion of A. baumannii isolates selected for their reduced susceptibility profile (including reduced susceptibility to cefiderocol) with resistance was 1.4–27.3%. Discussion: The low proportion of sulbactam–durlobactam resistance among A. baumannii complex isolates supports the consideration of the use of this new antibiotic for its approved indications.