What is the definition or description of: methicillin resistant staphylococcus aureus?

Resistance: Mrsa is just a staph aureus that has a new gene that renders it resistant to beta-lactam antibiotics; for the most part, it will present the exact same as a "regular" staph infection, and will respond to other antibiotics the same as non-mrsa. It is difficult to call one regular because in most of the us, about 50% of all staph aureus is now mrsa. Only way to tell for sure is lab culture.

Resistant to therapy: Mrsa is a form of staph aureus that can come in 2 forms, community aquired and hospital acquired. The bacteria will be resistant to penicillins that are used to treat MRSA including methicillin and oxacillin. There can still be oral choices for treatment as long as the infection is not severe.