MRSA is a kind of bacteria — a tiny living thing that can make you ill — that ordinary antibiotic drugs often cannot kill. The letters stand for methicillin-resistant Staphylococcus aureus: staphylococcus aureus is a common skin germ (people shorten it to staph), and resistant means the old drug methicillin no longer works on it. That is why news stories call it a superbug. It lives on skin and in noses without always causing trouble, but in a hospital it can get into a wound, a drip line, or the blood, and then it is hard to treat. You will meet the word in hospital leaflets and health news, not in everyday chat unless someone has been in hospital. Though actually, not every hospital germ is MRSA, and not every staph infection is this one — doctors test for it because the treatment changes if it is. It is serious, but it is not a death sentence in every case; hospitals watch for it so they can use different drugs and keep it from spreading.