Methicillin-resistant Staphylococcus aureus (MRSA) is difcult to treat with methicillin, amoxicillin,
penicillin, oxacillin, and other commonly used antibiotics because of its resistance. Staphylococcus
organisms rapidly develop drug resistance as many as 50% of the domiciliary and 80% of the hospital strains are now penicillin
resistant. Staphylococcus aureus also show multiple drug resistance. Therefore, Staphylococcal isolates should always be
tested for antimicrobial sensitivity and chronic infection should be treated by more than one drug. Before 1960,when methicillin,
is the rst penicillin's-resistant penicillin's, was brought into use, about 1%of the strains of the Staphylococcus aureus were
"methicillin resistant" and by 1970 in Britain their proportion has risen to about 5%.These strains are tolerant of, low therapeutic
concentrations of methicillin, cloxacillin, benzyl penicillin and ampicillin.They do not destroy methicillin and cloxacillin, but
most of them are penicillinase-producing as well as being "methicillin resistant" and therefore inactivate benzyl penicillin and
ampicillin. Its resistance is uncertain since infections may be cured with a high dose of methicillin.