Methicillin-resistant Staphylococcus aureus: from the hospital to the community.

Infections due to community-associated methicillin---resistant Staphylococcus aureus (CA-MRSA) are becoming more prevalent. CA-MRSA infections have unique epidemiologic features and virulence factors. Compared with health care-associated MRSA (HA-MRSA), most CA-MRSA is clonal type USA300 or 400 and has the Staphylococcal cassette chromosome mec type IV, which carries the mecA gene that encodes for resistance to methicillin and other beta-lactam antibiotics but generally not for other antibiotics. CA-MRSA often contains various virulence factors that may result in tissue necrosis. CA-MRSA clinical presentation includes mostly skin and soft tissue infections and less frequently pneumonia. In many of the small soft tissue abscesses due to CA-MRSA, primary treatment with surgical drainage may result in improvement without antibiotic therapy. Optimal treatment and prevention of CA-MRSA infections are unclear. However, distinction between CA-MRSA and HA-MRSA may be less relevant in the future, as CA-MRSA strains are now diagnosed in the hospital setting.