Daptomycin activity and spectrum: a worldwide sample of 6737 clinical Gram-positive organisms

Background: Increasing antimicrobial resistance among bacterial pathogens has prompted attempts to develop new antimicrobial agents active against multidrug-resistant Gram-positive pathogens. Objectives: To evaluate the in vitro activity of daptomycin against a worldwide collection of clinical bacterial isolates. Methods: Daptomycin is a novel cyclic lipopeptide recently approved by the United States Food and Drug Administration. Daptomycin and selected comparators were tested against 6737 clinical Gram-positive strains from more than 70 centres located in Europe, North America and South America. Results: The overall distribution of daptomycin MIC values were in the range less than or equal to0.12-8 mg/L and 99.4% of all strains were inhibited at less than or equal to2 mg/L. Despite resistances to other antimicrobial agents, >99.9% of staphylococcal isolates were inhibited at less than or equal to1 mg/L of daptomycin (MIC90 0.5 mg/L for staphylococci). Streptococcal isolates were very susceptible to daptomycin independent of their susceptibility to penicillin. MIC50/90 values were less than or equal to0.12 and 0.25 mg/L, respectively. Enterococci showed the highest daptomycin MIC values, but all isolates tested were inhibited at less than or equal to4 mg/L (except for one Enterococcus faecium isolate which showed a daptomycin MIC of 8 mg/L). Conclusions: Daptomycin exhibited excellent in vitro activity against a wide spectrum of Gram-positive organisms and may represent a therapeutic option for infections caused by multidrug-resistant pathogens worldwide.