MRSA

(Methicillin-Resistant Staphylococcus aureus): A specific strain of staph bacteria that has developed resistance to all core beta-lactam antibiotics, including methicillin, oxacillin, penicillin, and amoxicillin. It represents a widespread, high-priority pathogen that bypasses standard first-line staphylococcal treatments, often requiring specialized non-beta-lactam therapies like vancomycin.