Activity of dalbavancin against staphylococci and streptococci, assessed by BSAC and NCCLS agar dilution methods.
BACKGROUND
Dalbavancin is a long-half-life (9-12 days) glycopeptide, now in Phase 3 development. Its pharmacokinetics may facilitate home intravenous therapy, early discharge and long prophylaxis.


METHODS
Dalbavancin and comparators were tested in vitro against staphylococci and streptococci to determine (i) activity and (ii) the comparability of agar dilution MICs by the BSAC and the NCCLS methods. The test panels comprised 92-93 isolates each of Staphylococcus aureus, coagulase-negative staphylococci (CoNS) and 'viridans' streptococci, chosen for epidemiological diversity and to over-represent strains resistant to conventional agents, including teicoplanin.


RESULTS
Dalbavancin MICs by the BSAC and NCCLS methods generally were identical, or else those by the BSAC method were two-fold lower. In both cases the MIC distributions of dalbavancin within species groups were unimodal, with peaks at 0.25, 0.12/0.25 and 0.12 mg/L for S. aureus, CoNS and viridans streptococci, respectively. MIC differences between the BSAC and NCCLS methods were similarly small for other glycopeptides and, generally, non-glycopeptides. Dalbavancin MICs were mostly two- to 16-fold below those of vancomycin and dalbavancin-like vancomycin-remained highly active against teicoplanin-non-susceptible staphylococci.


CONCLUSIONS
Dalbavancin has good activity versus streptococci and staphylococci, including teicoplanin-resistant strains. MICs by BSAC and NCCLS agar dilution methods were comparable to each other; slightly lower MIC values, nevertheless, have been recorded by broth microdilution.
Mushtaq
Shazad
S
Antibiotic Resistance Monitoring & Reference Laboratory, Health Protection Agency Colindale, 61 Colindale Avenue, London NW9 5HT, UK.
Warner
Marina
M
Johnson
Alan P
AP
Livermore
David M
DM
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003470:Culture Media; D024901:Drug Resistance, Multiple, Bacterial; D006020:Glycopeptides / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D013210:Staphylococcus / Q000187:drug effects*; D013291:Streptococcus / Q000187:drug effects*; D017334:Teicoplanin / Q000494:pharmacology / Q000031:analogs & derivatives
D000900:Anti-Bacterial Agents; D003470:Culture Media; D006020:Glycopeptides; D017334:Teicoplanin; C469289:dalbavancin