Clinical Definition MRSA, or methicillin-resistant Staphylococcus Aureus, is a staph bacterium and the cause of certain skin infections in the community and serious hospital-acquired infections as well. S. aureus is common on the skin and in the nose and may be resistant to beta-lactam antibiotics (e.g., methicillin). Serious MRSA infections occur most frequently among patients in hospital settings. In…