Comparison between Colistin and Polymyxin B in the Treatment of Bloodstream Infections Caused by Carbapenem-Resistant and .

Polymyxins are still widely used for the treatment of carbapenem-resistant and bloodstream infections (BSIs). This study seeks to evaluate the impact of polymyxin B versus colistin on mortality and nephrotoxicity in BSI caused by these bacteria. We conducted a retrospective cohort study from 2014 to 2021 in Porto Alegre, Brazil. We included patients aged ≥18 years and excluded patients with polymicrobial infection or treatment for ≤48 h. The 30-day mortality was the primary outcome evaluated through Cox regression. We included 259 patients with BSI episodes: 78.8% caused by and 21.2% caused by . Polymyxin B did not impact mortality compared to colistin (adjusted hazard ratio (aHR), 0.82; 95% confidence interval (CI), 0.52-1.30; = 0.40 (when adjusted for COVID-19 comorbidity, = 0.05), Pitt bacteremia score, < 0.01; Charlson comorbidity index, < 0.001; time to start active antimicrobial therapy, = 0.02). Results were maintained in the subgroups of BSI caused by (aHR, 0.92; 95% CI, 0.55-1.54; = 0.74), (aHR, 0.47; 95% CI, 0.17-1.32; = 0.15) and critical care patients (aHR, 0.77; 95% CI, 0.47-1.26; = 0.30). Treatment with polymyxin B or colistin did not impact 30-day mortality in patients with carbapenem-resistant or BSI.