Comparative In Vitro Antimicrobial Activities of Torezolid (TR-700), the Active Moiety of a New Oxazolidinone, Torezolid Phosphate (TR-701), Determination of Tentative Disk Diffusion Interpretive Criteria, and Quality Control Ranges

This study assessed the spectrum of activity of torezolid (TR-700), the active moiety of torezolid phosphate (TR-701), and proposes tentative MIC and disk diffusion breakpoints as well as quality control ranges. The in vitro susceptibilities of 1,096 bacterial isolates, representing 23 different species or phenotypic groups, were determined for torezolid, linezolid, cefotaxime, and levofloxacin using Clinical and Laboratory Standards Institute (CLSI) broth microdilution MICs, minimum bactericidal concentrations (MBCs), agar dilution, and disk diffusion testing methods. Torezolid was very active against the majority of Gram-positive strains, including methicillin-susceptible and -resistant Staphylococcus aureus (MIC(50) = 0.25 microg/ml, MIC(90) <or= 0.5 microg/ml), coagulase-negative staphylococci (CNS; MIC(50) = 0.25 microg/ml, MIC(90) <or= 0.5 microg/ml), enterococci (MIC(50) and MIC(90) <or= 0.5 microg/ml), and streptococci (MIC(50) and MIC(90)