A member of the oxazolidinone class of drugs, linezolid is active against most Gram-positive bacteria that cause disease, including tuberculosis, streptococci, vancomycin-resistant enterococci (VRE), and methicillin-resistant Staphylococcus aureus (MRSA). Discovered in the 1990s and first approved for use in 2000, linezolid was the first commercially available 1,3-oxazolidinone antibiotic. As a protein synthesis inhibitor, it stops the growth of bacteria by disrupting their production of proteins, that is, it is a bacteriostatic agent, not bacteriocidal. Although many antibiotics work this way, the exact mechanism of action of linezolid appears to be unique in that it blocks the initiation of protein production, and not one of the later steps  Bacterial resistance to linezolid has remained very low.