Activity of daptomycin against Gram-positive pathogens: a comparison with other agents and the determination of a tentative breakpoint.
The in vitro activity of daptomycin was studied in comparison with other agents active against 328 recent clinical isolates of Gram-positive pathogens. MIC data showed that the addition of calcium ions to a final concentration of 50 mg/L enhanced the activity of daptomycin generally by eight- to 16-fold. In the presence of calcium ions daptomycin was uniformly active against the strains of Staphylococcus spp. and Streptococcus spp. studied with a MIC90 of < or = 1 mg/L. Enterococcus faecalis and Enterococcus faecium were slightly less susceptible (MIC90 2 mg/L). Vancomycin-, fluoroquinolone- and quinupristin/dalfopristin-resistant strains were all susceptible to daptomycin. The presence of serum reduced the apparent activity of daptomycin to only a moderate extent. Employing the BSAC methodologies, a tentative breakpoint of 2 mg/L for daptomycin is proposed.
Wise
R
R
Department of Microbiology, City Hospital NHS Trust, Birmingham B18 7QH, UK. r.wise@bham.ac.uk
Andrews
J M
JM
Ashby
J P
JP
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D017576:Daptomycin / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D006094:Gram-Positive Bacteria / Q000187:drug effects*; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods / Q000592:standards*
D000900:Anti-Bacterial Agents; D017576:Daptomycin