Real-world outcomes and safety of colistin therapy in children with multidrug-resistant gram-negative infections: a nine-year experience.

Antimicrobial resistance (AMR) among Gram-negative (GN) pathogens has emerged as a critical global threat, particularly in low- and middle-income countries where access to novel antimicrobials is limited. In Türkiye, colistin (CST) remains a last-resort therapy against multidrug-resistant (MDR) and carbapenem-resistant Gram-negative bacteria (CR-GNB) despite its nephrotoxic potential. This study aimed to evaluate the clinical characteristics, microbiological outcomes, and adverse events associated with CST therapy in pediatric patients over a nine-year period. We conducted a single-center retrospective cohort study including pediatric patients treated with CST for nosocomial MDR-GN infections at a tertiary university hospital between January 2016 and March 2025. Demographic, clinical, microbiological, and treatment-related data were collected. Univariable comparisons and multivariable logistic regression analyses were performed to identify factors associated with nephrotoxicity, treatment failure, and mortality. A total of 117 treatment episodes were identified among 112 patients (mean age: 75.9 ± 69.5 months; 65% male). The predominant pathogens were Klebsiella pneumoniae (39.7%), Pseudomonas aeruginosa (26.4%), and Acinetobacter baumannii (22.0%). CST was used in combination regimens in all episodes, most commonly with carbapenems (73.5%). Microbiological eradication was achieved in 70% of culture-confirmed episodes. The overall sepsis-related mortality rate was 18.8%. Nephrotoxicity occurred in 12.8% of patients and was associated with mortality and severity indicators in univariable analyses. In multivariable analysis, endotracheal intubation remained the only independent predictor of mortality (adjusted OR 23.98, 95% CI 4.47-128.52). Conclusions: CST remains a last-resort agent for MDR and CR-GNB infections in pediatric settings with limited access to novel antimicrobials. Although microbiological eradication was achieved in most cases, treatment outcomes were primarily driven by disease severity and host-related factors rather than antimicrobial combinations. Endotracheal intubation emerged as the strongest independent predictor of mortality. What is Known - What is New •CST is widely used as a last-resort option for pediatric MDR-GN infections. •Nephrotoxicity and variable clinical outcomes remain major concerns. •This study provides long-term real-world pediatric data on CST use. • Disease severity and host-related factors were the main determinants of treatment failure and mortality.