Superbug Staph (MRSA) Spread in Community

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Commonly called the "superbug," MRSA, or methicillin-resistant Staphylococcus aureus, is a bacterium that can cause serious infections. It "super" because it is resistant to numerous antibiotics, including methicillin and penicillin, so it is harder to treat than many bacterial infections.

MRSA belongs to the large group of bacteria known as staphylococci, often referred to as staph. Up to 33% of all people carry the staph bacteria within the lining tissues of the nose, but it normally does not cause an infection. In contrast, only about 2% of the population are carriers of MRSA.

Infections with MRSA can occur in hospitals and other institutional health-care settings, such as nursing homes, where they tend to strike older people, those who are very ill, and people with a weakened immune system. In health-care settings, MRSA is a frequent cause of surgical wound infections, urinary tract infections, bloodstream infections (sepsis), and pneumonia.

MRSA outbreaks, however, can also occur in people who have not been hospitalized or had a medical procedure performed in the past year, and who do not have immune deficiency. These infections are termed community-associated MRSA infections (CA-MRSA). CA-MRSA infections have increased dramatically in the U.S. since the mid-1990s.