In vitro activity of linezolid against vancomycin-resistant enterococci, methicillin-resistant staphylococcus aureus and penicillin-resistant streptococcus pneumoniae

We report the activity of the new oxazolidinone antimicrobial agent linezolid against 37 clinical isolates of vancomycin-resistant enterococci (including organisms carrying the vanA, vanB, vanC-1, and vanC-2/3 genes), 26 clinical isolates of methicillin-resistant S. aureus and 20 clinical isolates of high-level penicillin-resistant S. pneumoniae. All isolates of vancomycin-resistant enterococci were inhibited by ≤ 4 ug/ml of linezolid. All isolates of methicillin-resistant S. aureus were inhibited by ≤ 8 ug/ml of linezolid. All isolates of penicillin-resistant S. pneumoniae were inhibited by ≤ 2 ug/ml of linezolid. Linezolid inhibits strains of multidrug resistant Gram-positive cocci in vitro at concentrations ≤ 8 ug/ml.