In vitro activity: Linezolid inhibits initiation complex formation with either the 30S or the 70S ribosomal subunits from Escherichia coli. Linezolid inhibits complex formation with Staphylococcus aureus 70S tight-couple ribosomes. Linezolid is a potent inhibitor of cell-free transcription-translation in E. coli, exhibiting 50% inhibitory concentrations (IC50s) of 1.8 mM. Linezolid is an oxazolidinone, a new class of antibacterial agents with enhanced activity against pathogens. Linezolid MICs vary slightly with the test method, laboratory, and significance attributed to thin hazes of bacterial survival, but all workers find that the susceptibility distributions are narrow and unimodal, with MIC values between 0.5 and 4 mg/L for streptococci, enterococci and staphylococci. Linezolid entails mutation of the 23S rRNA that forms the binding site. Linezolid is an oxazolidinone whose mechanism of action involves inhibition of protein synthesis at a very early stage. Linezolid is added to 7H10 agar medium (Difco) supplemented with OADC (oleic acid, albumin, dextrose, and catalase) at 50°C to 56°C by doubling the dilutions to yield a final concentration of 0.125 μg/mL to 4 μg/mL. Linezolid shows excellent in vitro activity against all the strains tested (MICs ≤ 1 μg/ml), including those resistant to SIRE.

Cell Assay: Linezolid was a potent inhibitor of cell-free transcription-translation in E. coli. IC50 was 1.8 mM. linezolid MICs vary slightly owing to the different test method and laboratory. The MIC values were between 0.5 and 4 mg/L for streptococci, enterococci and staphylococci.

Antimicrob Agents Chemother. 1998 Dec;42(12):3251-5; Antimicrob Agents Chemother. 1997 Oct;41(10):2132-6; Antimicrob Agents Chemother. 1999 Aug;43(8):2059-62.