Predictors of clinical outcomes in Chinese patients with carbapenem-resistant Gram-negative bacterial infections receiving colistimethate sodium: a retrospective cohort study

Objective To evaluate the clinical outcomes of colistimethate sodium (CMS) in Chinese patients with carbapenem-resistant Gram-negative bacterial (CR-GNB) infections and to identify predictors associated with clinical outcomes. Methods A retrospective cohort study was performed in patients with CR-GNB infections who received CMS treatment between April 2022 and December 2025. The primary outcome was clinical efficacy; secondary outcomes included bacterial eradication and all-cause mortality. Predictors were identified using multivariable logistic and Cox regression. Results A total of 169 patients were included. The clinical efficacy was 40.8%, microbiological eradication was 50.3%, and all-cause mortality was 36.7%. Multivariate analysis showed that colistin MIC ≤ 0.5 mg/L (adjusted odds ratio [aOR] 3.495; 95% confidence interval [CI] 1.279–9.554; p = 0.015) and duration of CMS therapy (aOR 1.143; 95% CI 1.062–1.229; p < 0.001) were independently associated with favorable clinical efficacy, whereas vasoactive agent use (aOR 0.183; 95% CI 0.062–0.538; p = 0.002) and CMS monotherapy (aOR 0.076; 95% CI 0.008–0.706; p = 0.024) were inversely correlated with clinical success. Patients treated for 14–21 days with a cumulative CMS dose of 40–50 mg CBA/kg tended to have more favorable clinical outcomes. Combination with nebulization (adjusted hazard ratio [aHR] 0.416; 95% CI 0.246–0.703; p = 0.001) and concomitant β−lactam/β−lactamase inhibitor combinations (aHR 0.556; 95% CI 0.316–0.978; p = 0.042) were associated with lower all-cause mortality. Conclusion CMS demonstrated potential therapeutic value in the treatment of CR-GNB infections. Longer treatment durations (particularly 14–21 days) and combination therapy were independent predictors of higher clinical efficacy. Adjunctive nebulized CMS therapy correlated with reduced all-cause mortality, particularly in patients with respiratory tract infections.