What bacteria causes MRSA?

MRSA, or methicillin-resistant Staphylococcus aureus, is caused by a bacterium called Staphylococcus aureus. This type of bacteria is commonly found on the skin or in the nose of healthy individuals and usually does not cause any harm. However, in certain cases, S. aureus can become resistant to antibiotics such as methicillin, making infections difficult to treat.