Illustration of Staphylococcus aureus (MRSA) coccoid bacteria. Staphylococcus aureus is a Gram-positive bacterium that causes food poisoning, toxic shock syndrome and skin and wound infections such as scalded skin syndrome, scarlet fever, erysipelas and impetigo. Methicillin resistant Staphylococcus aureus (MRSA) infections that are acquired by persons who have not been recently hospitalized or had a medical procedure are known as CA-MRSA (Community associated-MRSA) infections. CA-MRSA infections in the community are usually manifested as skin infections, such as pimples and boils, and occur in otherwise healthy people.