815. Combination therapy is superior for treatment of Pseudomonas aeruginosa bloodstream infections (BSI): Analysis of 187 cases
Session: Poster Abstract Session: Bacteremia and Endocarditis
Friday, October 9, 2015
Room: Poster Hall
Background: Management of BSI caused by P. aeruginosa remains controversial: The rational for the use of combination therapy even when susceptibility pattern is known, includes possible synergistic activity and prevention of emerging resistance. However definite supporting clinical data is lacking. We aimed to determine differences in mortality between patients treated with combination therapy versus monotherapy in a large 11-year cohort.

Methods: All consecutive patients with detection of P. aeruginosa in blood cultures and hospitalized at the University Hospital Basel, a tertiary academic care center, from 1/2003-12/2013 were included.  Baseline characteristics, as well as comorbid conditions, Charlson comorbidity index, systemic inflammatory response syndrome (SIRS) criteria, Pitt bacteremia score, and antibiotic treatment were assessed.  Patients with and without definite combination therapy were compared and hazard ratios for death were calculated.

Results: 187 patients with P. aeruginosa BSI were identified. Definite combination therapy was administered in 42.8% (80/187) of all patients, of which 20% (16/80) received a combination of a betalactam and a quinolone and 80% received a combination of a betalactam with an aminoglycoside. The remaining 57.2% (107/187) were treated with betalactam monotherapy. Median treatment duration was 15 days (IQR 12-20 days). The age of patients significantly differed, but comorbid conditions, immunosuppression, receipt of solid organ or stem cell transplant, ICU admission, Pitt bacteremia score were similar between groups. Importantly, receipt of effective empiric treatment was equally distributed between groups. Mortality was significantly lower in patients receiving definite combination therapy in crude and adjusted cox regression analyses (HR 0.26, 95%CI 0.11-0.60, p=0.002 and HR 0.29 95%CI 0.12-0.68, p=0.004, respectively).

Conclusion: This study provides evidence that combination antimicrobial treatment regimens including quinolones or aminoglycosides in addition to betalactams improves survival in P.aeruginosa BSI compared to betalactam monotherapy. However, new antibiotic regimens may be as effective as combination therapy.

Sarah Tschudin-Sutter, MD, MSc1, Nicole Fosse, MS1, Maja Weisser, MD1, Reno Frei, MD2 and Andreas F. Widmer, MD, MS1, (1)Division of Infectious Diseases and Hospital Epidemiology, University Hospital Basel, Basel, Switzerland, (2)Division of Clinical Microbiology, University Hospital Basel, Basel, Switzerland


S. Tschudin-Sutter, None

N. Fosse, None

M. Weisser, None

R. Frei, None

A. F. Widmer, None

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