OBJECTIVE  To evaluate the efficacy and safety of colistin sulfate in treating severe patients infected with carbapenem-resistant organism （CRO）, assess the correlation between colistin sulfate plasma concentration and clinical efficacy as well as adverse reactions and analyze potential influencing factors.

METHODS  A retrospective analysis was conducted on the medical records of severe patients infected with CRO, who were treated with colistin in the intensive care unit of the Third Affiliated Hospital of Soochow University from Feb. 2023 to Dec. 2024. The clinical efficacy, microbial clearance rate, incidence of acute kidney injury （AKI） and the correlation between colistin sulfate plasma concentration and clinical efficacy as well as adverse reactions were evaluated. Multivariate logistic regression analysis was performed to identify risk factors for treatment failure in severe patients infected with CRO.

RESULTS  Among 96 severe patients treated with colistin sulfate, 55 cases responded effectively to treatment and 41 cases did not, with a clinical treatment efficacy rate of 57.29% and a microbial treatment efficacy rate of 60.42% （58/96）. The 28-day fatality rate was 5.21% （5/96）, and AKI occurred in 9.38% （9/96） of the patients. There was no statistically significant difference in plasma concentration between the clinically effective group and the ineffective group, but the plasma concentration in the AKI group and the hepatotoxicity group was higher than that in the groups without AKI and no-hepatotoxicity （P＜0.05）. Multivariate logistic regression analysis showed that a duration of medication use of ≤7 days （OR=2.819） and the use of vasoactive drugs （OR=13.612） were risk factors for clinical treatment failure of severe patients infected with CRO （P＜0.05）.

CONCLUSION  Colistin sulfate can achieve high efficacy in treatment of patients with severe CRO infections and microbial clearance rates in clinical practice, with a low risk of kidney injury.