Impact of multidrug-resistant Pseudomonas aeruginosa bloodstream infections on mortality in oncology patients

INTRODUCTION: Pseudomonas aeruginosa (PAE) is among the most frequent causes of bloodstream infections (BSIs) in cancer patients. Resistant strains are associated with increased morbidity and mortality. METHODOLOGY: A retrospective study was conducted at a tertiary oncology hospital in Mexico City, including all episodes of PAE-BSI. The isolates were classified as susceptible, carbapenem-resistant (CR), multidrug-resistant (MDR), or difficult-to-treat resistant (DTR). RESULTS: A total of 259 PAE-BSI episodes were analyzed: 202 (78.4%) susceptible, 19 (7.3%) CR, 13 (5.0%) MDR, and 25 (9.7%) DTR. Resistant strains were significantly associated with prior antibiotic use (84.2% vs. 52.5%), more extended hospital stays (18 vs. 9 days), septic shock (36.8% vs. 19.8%), and inappropriate empiric therapy (54.4% vs. 19.3%). Overall, 30-day mortality was 38.2%, rising to 47.4% in CR, 84.6% in MDR, and 76% in DTR cases; compared with 29.7% in susceptible isolates (p < 0.001). No mortality benefit was observed with combination therapy compared to monotherapy. Multivariate analysis indicated that age ≥ 60 years, advanced oncological status, secondary bacteremia, septic shock, invasive mechanical ventilation, inadequate source control, and carbapenem strains were independent predictors of 30-day mortality. Appropriate antimicrobial therapy was a protective factor. CONCLUSIONS: Resistant PAE-BSI in cancer patients was associated with longer hospitalizations and a significantly increased mortality rate. Appropriate antimicrobial therapy can lead to a reduction in mortality.