Linezolid (PNU-100766), the first of the oxazolidinone class, is a synthetic antibiotic used for the therapy of infections resulted from multi-resistant bacteria including methicillin-resistant Staphylococcus aureus (MRSA) and streptococcus. The drug takes effect as the inhibitor of the initiation of bacterial protein synthesis.

Linezolid effectively inhibits Escherichia coli lacking cellular transcription-translation mechanisms, with an IC50 value of 1.8 mM. Its mode of action primarily involves suppressing the synthesis of early-stage proteins, representing a novel antimicrobial agent that enhances anti-pathogenic activity. Linezolid inhibits the formation of the initiation complex by the E. coli 70S or 30S ribosomal subunit. Due to variations in testing methods and laboratory conditions, discrepancies in Linezolid's MIC (Minimum Inhibitory Concentration) have been noted, yet it consistently displays a narrow sensitivity range, with MIC values for streptococci, staphylococci, and enterococci between 0.5 mg/L and 4 mg/L. Linezolid induces mutations at the 23S rRNA gene binding site. When added to 7H10 agar medium [oleic acid, albumin, dextrose, and catalase], and diluted to final concentrations ranging from 0.125 μg/mL to 4 μg/mL at 50°C-56°C, Linezolid exhibits excellent in vitro activity (MIC values ≤1 μg/mL) against tested strains, including those resistant to SIRE.