Antimicrobial activity of daptomycin in comparison to glycopeptides and other antimicrobials when tested against numerous species of coagulase-negative Staphylococcus

Coagulase-negative Staphylococcus spp. (CoNS) represent a major cause of bloodstream infections, especially in patients with prosthetic devices and intravenous catheters. We evaluated the activity of daptomycin in comparison to vancomycin and teicoplanin against a large collection of 22,024 CoNS isolates causing clinically significant infections from 283 medical centers over 9 years (2002-2010) and tested for susceptibility by broth microdilution methods against daptomycin and numerous comparators. Overall, daptomycin (MIC(50/90), 0.25/0.5 μg/mL) inhibited 99.8% of CoNS at the susceptible breakpoint of ≤1 μg/mL and was 4- to 16-fold more active than vancomycin (MIC(50/90), 1/2 μg/mL; >99.9% susceptible). All species showed ≥99.6% susceptibility to daptomycin, except Staphylococcus auricularis (95.1%), S. capitis (99.0%), S. warneri (98.8%), and S. sciuri. S.sciuri represented only 0.2% of the collection (46 strains) and exhibited decreased susceptibility to daptomycin (MIC(50/90), 1/2 μg/mL; 71.7% susceptible). In contrast, S. sciuri exhibited high susceptibility to vancomycin and teicoplanin (highest MIC at 2 μg/mL for both drugs). In summary, daptomycin exhibited species-specific activity among CoNS, especially versus S. sciuri. No correlation between decreased susceptibility to daptomycin and the glycopeptides tested was observed.