 Linezolid is effective against all clinically important Gram @-@ positive bacteria — those whose cell wall contains a thick layer of peptidoglycan and no outer membrane — notably Enterococcus faecium and Enterococcus faecalis ( including vancomycin @-@ resistant enterococci ) , Staphylococcus aureus ( including methicillin @-@ resistant Staphylococcus aureus , MRSA ) , Streptococcus agalactiae , Streptococcus pneumoniae , Streptococcus pyogenes , the <unk> group streptococci , Listeria monocytogenes , and Corynebacterium species ( the latter being among the most susceptible to linezolid , with minimum inhibitory concentrations routinely below 0 @.@ 5 mg / L ) . Linezolid is also highly active in vitro against several mycobacteria . It appears to be very effective against Nocardia , but because of high cost and potentially serious adverse effects , authors have recommended that it be combined with other antibiotics or reserved for cases that have failed traditional treatment . 
