MRSA, or methicillin-resistant Staphylococcus aureus, is a bacteria that is responsible for many hard-to-treat infections. The bacteria is often referred to as a "super bug," because it cannot be killed with certain antibiotics, including common ones like penicillin and amoxicillin. MRSA most often causes painful skin infections, but it can also lead to infections of the urinary tract, blood, and lungs. Some of these infections can be life-threatening. People who are in the hospital are more likely to get severe MRSA infections. Follow the links below to find WebMD's comprehensive coverage about how MRSA is contracted, what the symptoms are, how to treat it, and much more.