Antibiotic therapy for Pseudomonas aeruginosa bacteremia: outcome correlations in a prospective study of 200 patients.

PURPOSE AND PATIENTS AND METHODS: We performed a prospective clinical study of 200 consecutive patients with Pseudomonas aeruginosa bacteremias to analyze in vitro susceptibility and synergistic testing of antibiotics the patients received and clinical parameters to assess their relationship to survival. RESULTS: No significant correlation between in vitro susceptibility testing (minimal inhibitory concentrations/minimal bactericidal concentrations) and outcome could be demonstrated. Similarly, improved outcome could not be demonstrated for patients receiving antibiotic combinations that were synergistic in vitro (either time-kill or checker-board) versus those combinations that were not. There was also no correlation between results obtained by time-kill curve and checkerboard synergistic testing, i.e., combinations found to be synergistic by one method were not necessarily synergistic by the other method. Clinical parameters associated with improved survival were a urinary portal of entry and absence of neutropenia. Conversely, survival was significantly decreased when the portal was the respiratory tract. The mortality rate between patients receiving combination therapy (27%) and monotherapy (47%) was significant (p less than 0.02); this significant relationship held true for most subgroups including malignancy, nosocomial infection, and infection site. CONCLUSION: Increasing effort should be placed on ensuring timely administration of combination therapy to patients with P. aeruginosa bacteremia since the use of combination therapy was even more important in determining outcome than was underlying disease.