Antibiotic and MRSA
photo credit: kaibara87 First – What is MRSA? Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterium responsible for several difficult-to-treat infections in humans. MRSA is by definition any strain of Staphylococcus aureus bacteria that is resistant to a large group of antibiotics called the beta-lactams, which include the penicillins and the cephalosporins.