Clinical Outcomes of High-Dose Ampicillin–Sulbactam Combined with Colistin in the Treatment of Ventilator-Associated Pneumonia Caused by Carbapenem-Resistant Acinetobacter baumannii

Abstract

Ventilator-associated pneumonia (VAP) caused by carbapenem-resistant Acinetobacter baumannii (CRAB) poses a significant therapeutic challenge with high mortality rates. This study evaluated the clinical efficacy of high-dose ampicillin–sulbactam combined with colistin compared to standard colistin-based regimens. This retrospective study was conducted on 83 patients with CRAB-VAP at Hanoi Medical University Hospital, Vietnam, from May 2024 to May 2025. Patients were divided into an intervention group (n = 33) treated with high-dose ampicillin–sulbactam combined with colistin and a control group (n = 50) receiving other antibiotic regimens combined with colistin. Primary outcomes included 28-day mortality and total ventilation duration. The intervention group achieved significantly lower 28-day mortality (6.1% vs. 38.0%; p < 0.001) and higher microbiological clearance rates by day 14 (93.9% vs. 30.0%; p < 0.001). While early acute kidney injury was more frequent in the intervention group (66.7% vs. 24.0%), renal function outcomes were comparable by day 14. Multivariable analysis identified day-14 microbiological clearance as the strongest independent predictor of survival (hazard ratio [HR] = 13.03; p < 0.001). High-dose ampicillin–sulbactam combined with colistin significantly improves microbiological clearance and survival in patients with CRAB-VAP. Despite a higher incidence of transient nephrotoxicity, the regimen provides a substantial survival benefit.