Abstract
BACKGROUND: Colistin is a last-resort antibiotic used against infections caused by multidrug-resistant gram-negative organisms, particularly carbapenem-resistant strains. Rising resistance to colistin is a significant global concern. To address this, an Antimicrobial Stewardship (AMS) Program was introduced in our hospital, including pre-authorization protocols for colistin use. OBJECTIVE: To evaluate the prevalence of colistin-resistant organisms and determine the impact of AMS implementation on their occurrence and associated clinical outcomes. METHODS: We conducted a quasi-experimental study at a tertiary care hospital in Pakistan, comparing data from 18 months before and after AMS implementation. Adult patients (>18 years) with confirmed infections due to colistin-resistant Klebsiella pneumoniae, Pseudomonas aeruginosa, or Acinetobacter spp. were included. Clinical and microbiological data were analyzed to assess differences in organism prevalence, mortality, and hospital stay duration. RESULTS: A total of 121 patients met inclusion criteria, with 45 (37.2%) in the pre-AMS period and 76 (62.8%) in the post-AMS period. Klebsiella pneumoniae was the most frequently isolated organism in both groups. The overall in-hospital mortality rate was 34%, and the average length of stay was approximately 20 days, with no significant differences between periods. Despite AMS implementation, colistin resistance prevalence did not decline. CONCLUSION: While the AMS facilitated better identification and documentation of colistin-resistant infections, it did not significantly reduce their prevalence or associated mortality. Strengthened stewardship measures, continuous compliance monitoring, and alternative therapeutic strategies are needed to curb rising colistin resistance in high-burden settings.