Abbreviation for methicillin-resistant Staphylococcus aureus, an infection that causes serious problems in hospitals. S. aureus is a very common bacterium, present in the nose in 30% of people. Normally it gives no trouble, but, largely due to over-prescribing of antibiotics, strains have arisen that are resistant to the drugs used to treat them, principally methicillin. MRSA strains represent a serious hazard to the critically ill or immunosuppressed.
MRSA normally responds to two antibiotics which are considered too toxic for use in any but life-threatening infections (vancomycin and teicoplanin) but it still causes fatalities. An outbreak of MRSA may force closure of an acute ward or intensive care unit for some days.