Bactericidal activity of daptomycin against Streptococcus pneumoniae compared with eight other antimicrobials.

A spectrum of pneumococci with varying susceptibilities to beta-lactams, macrolides and quinolones was tested for susceptibility to nine antibiotics, including the novel lipopeptide daptomycin. Daptomycin was active against all strains (MIC range </=0.5 mg/L; MIC(50) 0.125 mg/L; MIC(90) 0.25 mg/L). All pneumococci were susceptible to vancomycin, teicoplanin, linezolid and quinupristin/dalfopristin, with MICs < 4.0 mg/L. Time-kill assays with eight strains demonstrated that daptomycin (2 x MIC) was bactericidal in seven of eight strains tested at 24 h, with >90% killing at 1 h.