In vitro activity of fosfomycin against methicillin-susceptible and methicillin-resistant Staphylococcus aureus

The in vitro antibacterial activity of fosfomycin was compared to that of oxacillin, cefazolin, ceftriaxone and vancomycin against isolates of Staphylococcus aureus from patients treated at the University of Vienna General Hospital. Of 211 strains, 104 were methicillin-susceptible and 107 were methicillin-resistant. Fosfomycin inhibited over 90% of the strains at concentrations of less than or equal to 64 mg/l, independent of methicillin susceptibility or resistance. The minimal bactericidal concentrations (MBC) were one dilution above the minimal inhibitory concentrations (MIC). Vancomycin showed activity similar to fosfomycin while other beta-lactam antibiotics such as oxacillin, cefazolin and ceftriaxone were inactive against methicillin-resistant S. aureus. Fosfomycin at a high dosage seems to be a potential drug for the treatment of infections due to methicillin-resistant S. aureus.