MRSA Infection: Symptoms, Causes, Treatment, Contagious, … Apr 22, 2022 · Staphylococcus aureus (SA) is a common skin bacterium. It is sometimes called staph, and it most often causes skin and soft tissue infections. Although S. aureus has been causing staph infections as long as humans have existed, MRSA has only been around since 1961. Methicillin was one of the first antibiotics used to treat S. aureus and other infections.