Inhibitory and Bactericidal Activities of Daptomycin, Vancomycin, and Teicoplanin against Methicillin-Resistant Staphylococcus aureus Isolates Collected from 1985 to 2007

The inhibitory and bactericidal activities of daptomycin, vancomycin, and teicoplanin against a collection of 479 methicillin-resistant Staphylococcus aureus isolates were assessed. The isolates were collected from U. S. and European hospitals from 1985 to 2007 and were primarily from blood and abscess cultures. The MICs and minimum bactericidal concentrations (MBCs) of the three agents were determined, and the MBC/MIC ratios were calculated to determine the presence or absence of tolerance. Tolerance was defined as an MBC/MIC ratio of >= 32 or an MBC/MIC ratio of >= 16 when the MBC was greater than or equal to the breakpoint for resistance. Tolerance to vancomycin and teicoplanin was observed in 6.1% and 18.8% of the strains, respectively. Tolerance to daptomycin was not observed.