Staphylococcus aureus (S. aureus) or "staph", is a bacterium found in the nose or on the skin of approximately 20-30% of the U.S. population. It causes diseases ranging from mild to severe skin and soft tissue infections to more serious invasive diseases such as blood stream infections, pneumonia and toxic shock syndrome. Although most infections are treated successfully with antibiotics, some cases result in significant injury or death.
MRSA (methicillin-resistant staphylococcus aureus) refers to S. aureus strains that are resistant to certain antibiotics. MRSA emerged in U.S. hospitals in the 1960s and is now the most common drug-resistant organism found in hospital settings. According to national hospital surveys, MRSA represented two percent of all S. aureus infections in hospitals in 1975, 35% in 1991, and 64% in 2003.
There are two main types of MRSA
- Healthcare-associated (HA) MRSA is found primarily in hospital patients and long-term care residents.
- Community-associated (CA) MRSA occurs in persons who report no contact with healthcare facilities.