Methicillin-resistant "Staphylococcus aureus" is "Staphylococcus aureus" that is not cured by the antibiotic Methicillin or any other penicillin or cephalosporin antibiotics. This is called antibiotic resistance. Because penicillin and cephalosporin are the most important drugs that doctors use to treat "Staphylococcus aureus" infections, doctors may not be able to cure people with MRSA.