Methicillin-resistantStaphylococcus aureus (MRSA) is a type of bacterium. Staph bacteria, like other kinds of bacteria, frequently live on the skin and in the nose without causing health problems. Staph becomes a problem when it is a source of infection. These bacteria can be spread from one person to another through casual contact or through contaminated objects. Infections with MRSA are more difficult to treat than ordinary Staph infections because these strains of bacteria are resistant to many types of antibiotics—the medicines used to treat bacterial infections. Infections can occur in wounds, burns, and other sites where tubes have been inserted into the body. In 2005, there were an estimated 94 360 cases of MRSA infections in the United States.