Staphylococcus aureus may express various mechanisms of resistance to antibiotics which are combined in methicillin-resistant strains. Antibiotic resistance has been reported in clinical isolates for almost all antibiotics, except for vancomycin. The mechanisms involved in resistance are target modification, enzymic modification of the antibiotics, and active efflux of the drugs. Numerous genes encode this resistance. This partially explains the easy adaptation of S. aureus to antibiotics.