Linezolid is a synthetic antibiotic developed by a team at Pharmacia and Upjohn Company. It is used for the treatment of serious infections caused by Gram-positive bacteria that are resistant to several other antibiotics. The main indication of linezolid is the treatment of severe infections caused by Gram-positive bacteria that are resistant to other antibiotics; it should not be used against bacteria that are sensitive to drugs with a narrower spectrum of activity, such as penicillins and cephalosporins. In both the popular press and the scientific literature, linezolid has been called a "reserve antibiotic"—one that should be used sparingly so that it will remain effective as a drug of last resort against potentially intractable infections. Linezolid is a weak monoamine oxidase inhibitor (MAOI), and should not be used concomitantly with other MAOIs, large amounts of tyramine-rich foods or serotonergic drugs.