Combination therapy for treatment of Pseudomonas aeruginosa bloodstream infections

OBJECTIVES: Management of bloodstream infections (“BSIs”) caused by Pseudomonas aeruginosa remains controversial as data supporting the use of definite combination treatment for severe P. aeruginosa infections remain conflicting. We aimed to determine differences in mortality between patients treated with definite combination therapy and monotherapy in a large 11-year cohort. METHODS: All consecutive patients with P. aeruginosa BSI hospitalized at the University Hospital Basel, Switzerland, a tertiary academic care center, from January 2003 to December 2013 were included. Pertinent clinical data was assessed. Patients with and without definite combination therapy were compared and hazard ratios for death were calculated. RESULTS: During the study period, 187 patients with P. aeruginosa BSI were identified. Definite combination therapy was administered in 42.8% (80/187) of all patients, of which 76% (61/80) received a combination of a betalactam with an aminoglycoside and 24% (19/80) received a combination of a betalactam with a quinolone. The remaining 57.2% (107/187) were treated with betalactam monotherapy. Median treatment duration was 15 days (interquartile range 12–20 days). Mortality was lower in patients receiving definite combination therapy in univariable and multivariable cox regression analyses (HR 0.26, 95% CI 0.11–0.60, p = 0.002 and HR 0.30, 95% CI 0.13–0.71, p = 0.006, respectively), the latter adjusting for age, neutropenia at diagnosis, PITT bacteremia score, and inadequate empirical treatment. CONCLUSIONS: Combination therapy (i.e. betalactam-aminoglycoside or betalactam-quinolone combinations) may improve survival of P. aeruginosa BSI, independent of potential confounders such as age, neutropenia, PITT bacteremia score, and inadequate empirical treatment.