Risk factors and outcome of Pseudomonas aeruginosa bloodstream infections (PABSI) in hematological patients: a single center retrospective cohort study.

Purpose: Bloodstream infections caused by Pseudomonas aeruginosa (PABSI) in hematological patients are associated with high morbidity and mortality. We investigated the epidemiology, risk factors, and outcomes of PABSI at our center.

Methods: All adult hematological patients with PABSI between January 2013 and July 2023 were included. Demographic and clinical characteristics, antimicrobial susceptibilities, antibiotic therapy, fluoroquinolone-prophylaxis, source of infection, and 30-day outcome were recorded. Descriptive statistics, tests for difference, and logistic regression models were performed.

Results: Fifty patients with PABSI were identified with a median age of 58.5 years (range 24-78). 37 patients (74%) had severe neutropenia, 20 (40%) received allogeneic HSCT, and 29 (58%) had acute leukemia. A total of 34 (68%) had received timely appropriate anti-pseudomonal antibiotic therapy. The most common presumed cause of PABSI was mucositis (n = 16, 32%), followed by pneumonia (8, 16%) and skin and soft tissue infections (n = 6, 12%). Empirical combination therapy was used in 16 (32%) patients, while targeted combination therapies were used in 27 (54%) patients. P. aeruginosa detection led to treatment change in 31 (62%) cases. The overall 30-day survival rate was 78% (n = 39). Carbapenem-resistance occurred in 34% (n = 17), and multidrug-resistance (MDR) in 20% (n = 10). Prior antibiotic exposure was associated with resistance. Appropriate antibiotic therapy was associated with survival, whereas antibiotic resistance and organ infection were associated with a fatal outcome.

Conclusion: Prior antibiotic exposure in hematological patients is associated with resistance in PABSI, which is a major risk factor for a fatal outcome. Antibiotic stewardship efforts should be intensified and fluoroquinolone prophylaxis needs to be reconsidered.