The epidemiological and molecular characteristics and sulbactam-durlobactam susceptibility of carbapenem-resistant Acinetobacter baumannii in a Chinese teaching hospital.

OBJECTIVES: This study aimed to investigate sulbactam-durlobactam (SUL-DUR) susceptibility and molecular features of carbapenem-resistant Acinetobacter baumannii (CRAB) isolates from a Shenzhen teaching hospital.

METHODS: A retrospective study on CRAB was conducted from January 2018 to June 2025. Isolates were screened for gyrB and β-lactamase genes (blaOXA-23, -24, -51, and -58). Multi-locus sequence typing (MLST) was used for genotyping, and SUL-DUR susceptibility was tested by disk diffusion. The SUL-DUR-resistant isolate underwent whole-genome sequencing to identify resistance mechanisms.

RESULTS: Of 741 non-duplicate A. baumannii isolates, 147 were CRAB, with its annual percentage rising from 11.4% (2018) to 47.2% (2025). Most isolates came from the ICU (53.7%), and affected patients were predominantly aged ≥60 years (62.6%). Sputum was the primary source (49.7%). Resistance rates exceeded 90% for multiple antibiotics, but only one isolate (0.7%) was resistant to SUL-DUR. This strain harbored nine resistance genes (including blaOXA-23 and blaOXA-66) and had substitutions in penicillin-binding protein 2 (PBP2) and a putative D-Ala-D-Ala carboxypeptidase. Five sequence types (STs) were identified, including ST2, ST877, ST133, ST195, and a novel sequence type (ST3267), with ST2 being predominant (96.6%). The blaOXA-23 gene was present in 72.8% of isolates, while blaOXA-24 was rare (2.7%). All isolates carried intrinsic blaOXA-51 and gyrB, but blaOXA-58 was absent.

CONCLUSIONS: The increasing percentage of carbapenem-resistance among A. baumannii, dominated by ST2 and blaOXA-23-positive strains, highlights an urgent need for stricter infection control. Meanwhile, the notable in vitro susceptibility of CRAB to SUL-DUR offers a promising therapeutic alternative for patients infected with CRAB.