 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 . 
