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1. Any of various strains of the bacterium Staphylococcus aureus that are resistant to methicillin and other beta-lactam antibiotics and can cause life-threatening infections. Many strains are also resistant to other classes of antibiotics.
2. An infection caused by one of these strains of bacteria.
[m(ethicillin)-r(esistant) S(taphylococcus) a(ureus).]
(Microbiology) methicillin-resistant Staphylococcus aureus: a bacterium that enters the skin through open wounds to cause septicaemia and is extremely resistant to most antibiotics. It has been responsible for outbreaks of untreatable infections among patients in hospitals