Antimicrobial activity of daptomycin and selected comparators tested against bloodstream Staphylococcus aureus isolates from hemodialysis patients

Background: Patients on long-term hemodialysis are at a significantly higher risk for catheter-related bloodstream infections (BSI) than the general population. These infections are generally caused by Gram-positive organisms, especially Staphylococcus aureus. In the present study, we evaluated the antimicrobial susceptibility patterns of S. aureus causing BSI in dialysis patients compared to those causing BSI in other patient populations. Methods: The potencies of daptomycin and various comparator agents were evaluated by reference broth microdilution methods for S. aureus bloodstream isolates from dialysis patients (606 strains) in 43 hospitals in North America and Europe. Susceptibility patterns for the dialysis isolate set were compared to those S. aureus causing BSI in other patient populations in the same hospitals and time period. Results: Daptomycin was highly potent against S. aureus causing bacteremia in dialysis patients (MIC50/MIC90, 0.25/0.5 mu g/ml). Vancomycin (MIC50/MIC90, 1/1 mu g/ml) and linezolid (MIC50/MIC90, 2/2 mu g/ml) showed similar potency, and overall susceptibility rates for the three antibiotics were 99.8-100.0% susceptible. Linezolid and vancomycin were four- to eight-fold less potent than daptomycin. Conclusions: The overall susceptibility patterns of S. aureus strains from dialysis patients were very similar to those of non-dialysis patients. (c) 2008 International Society for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.