Activity of daptomycin and selected antimicrobial agents tested against Staphylococcus aureus from patients with bloodstream infections hospitalized in European medical centers.

Daptomycin is a cyclic lipopeptide with potent bactericidal activity against Gram-positive organisms and has been approved by the United States Food and Drug Administration for the treatment of Staphylococcus aureus bacteremia and infectious endocarditis (right-side). We evaluated the activity of daptomycin against bloodstream infection S. aureus strains from 4,799 patients hospitalized in 32 medical centers (12 European countries, Turkey and Israel) with bloodstream infections (BSI) during a 5-year period (2002-2006). Intravenous catheters were the source of infection in 15% of cases, and those strains were analyzed separately. All strains were susceptibility tested by reference broth microdilution methods utilizing calcium supplementation (50 mg/L) when testing daptomycin. Bactericidal activity of daptomycin and vancomycin were evaluated against a subset of 50 randomly selected strains. Daptomycin (MIC(50/90), 0.25/0.5 mg/L), vancomycin (MIC (50/90), 1/1 mg/L), and linezolid (MIC(50/90), 2/2 mg/L), were highly active (>99.9% susceptibility) against the strains evaluated; and daptomycin was the most potent (lowest MIC(90) ) among these compounds. Resistance rates to oxacillin and levofloxacin were generally elevated, especially when an intravenous catheter was the source of infection.