In vitro activity of quinupristin/dalfopristin, linezolid, telithromycin and comparator antimicrobial agents against 13 species of coagulase-negative staphylococci.

OBJECTIVES To determine in vitro susceptibilities of a large series of speciated coagulase-negative staphylococci (CNS) against three new antibiotics, linezolid, quinupristin/dalfopristin and telithromycin. METHODS Susceptibilities to three new antibiotics and oxacillin, vancomycin, clindamycin and erythromycin were determined by the agar dilution method, as described by the NCCLS. RESULTS Resistance to linezolid was not observed in any isolates, although MIC90 values varied between species. Fifteen of 658 (2.3%) isolates were resistant to quinupristin/dalfopristin, but < 1% of the clinically most important isolates of Staphylococcus epidermidis, Staphylococcus haemolyticus and Staphylococcus hominis demonstrated resistance to this agent. Susceptibility to clindamycin correlated with susceptibility to quinupristin/dalfopristin; however, resistance to clindamycin did not predict quinupristin/dalfopristin resistance. Telithromycin was the least active of the new agents tested, showing activity similar to that of clindamycin. Susceptibility and resistance to clindamycin were predictive of susceptibility and resistance to telithromycin. CONCLUSION Clindamycin susceptibility can be used as a surrogate marker for susceptibility to quinupristin/dalfopristin and telithromycin. Quinupristin/dalfopristin and linezolid show good activity against both mecA-positive and -negative CNS.