MRSA stands for meticillin-resistant Staphylococcus aureus. It's a type of bacteria, and is sometimes known as a superbug. There are various strains (subtypes) of S. aureus and some strains are classed as MRSA. Strains of MRSA are very similar to any other strain of S. aureus. That is, some healthy people are carriers and some people develop the types of infections described above.
This is a companion discussion topic for the original article at https://patient.info/infections/mrsa-leaflet