Acinetobacter baumannii resistance trends in an ICU from Saudi Arabia over 12 years.

Background and objectives Acinetobacter baumannii is a major intensive care unit (ICU)-associated pathogen due to associated extensive drug resistance. Regional data from southern Saudi Arabia remain limited. This study aimed to describe overall and temporal resistance patterns of ICU-associated A. baumannii. Methods We conducted a 12-y retrospective study (August 2012- August 2024) at Aseer Central Hospital, Saudi Arabia, analysing Acinetobacter spp. clinical isolates from ICU and non-ICU settings. Species identification and antimicrobial susceptibility testing (AST) were performed using the VITEK® 2 system, with susceptibility interpreted per CLSI M100 guidelines. Carbapenem-resistant A. baumannii (CRAB) and difficult-to-treat resistance phenotypes were defined. Temporal trends were assessed via logistic regression. Results Of 3,935 isolates, 96.6% were A. baumannii. ICU-derived isolates (48.5%) showed significantly higher resistance rates across nearly all antibiotic classes compared to non-ICU isolates (P<0.001). Carbapenem resistance rates remained above 90% throughout the study period, while difficult to treat resistance ranged between 65.2 to 96.1%. Logistic regression revealed significant temporal declines in resistance to cefepime, ceftazidime, aminoglycosides, and fluoroquinolones (P<0.001). Interpretation and conclusions Acinetobacter baumannii isolates from ICU settings in southern Saudi Arabia exhibit persistently high resistance, including carbapenem resistance and difficult-to-treat resistance. We observed significant temporal declines in resistance to selected agents, particularly cefepime, aminoglycosides, and fluoroquinolones. These findings highlight the critical role of ICU-focused antimicrobial stewardship, enhanced infection control strategies, and regional molecular surveillance to limit further spread.