DefinitionMethicillin-resistant Staphylococcus aureus (MRSA) is a bacterial infection that is highly resistant to some antibiotics.Alternative NamesMethicillin-resistant Staphylococcus aureus;Community-acquired MRSA (CA-MRSA); Hospital-acquired MRSA (HA-MRSA)Causes, incidence, and risk factorsMRSA is a strain of Staphylococcus aureus (S. aureus) bacteria. S. aureus is a common type of bacteria that normally live on the skin and sometimes in the nasal passages of healthy people. MRSA refers to S. aureusstrains that do not respond to some of the antibiotics used to treat staph infections.The bacteria can cause infection when they enter the body through a cut, sore, catheter, or breathing tube. The infection can be minor and local (for example, a pimple), or more serious (involving the heart,