Methicillin-resistant Staphylococcus aureus infections.

Community-acquired methicillin-resistant Staphylococcus aureus (MRSA) infection is epidemic in the community, differs from nosocomial MRSA in virulence, mechanisms, and antibiotic susceptibility, and exhibits diverse and often unique pathologic characteristics. The community-acquired MRSA USA 300 strains are transmitted largely by person-to-person contact and cause characteristic soft-tissue abscesses and, less commonly, other sometimes unusual and serious infections including a necrotizing pneumonia, and other necrotic infections such as necrotizing fasciitis, pelvic thrombophlebitis, and septic phlebitis. This MRSA 300 family remains susceptible to drugs active against nosocomial MRSA (ie, vancomycin, linezolid, daptomycin) and is often susceptible to trimethoprim-sulfamethoxazole, doxycycline, and clindamycin. Recent epidemiologic data indicate that nosocomial MRSA (eg, mainly USA 100) strains are also present in the community and that MRSA USA 300 strains are present in hospital settings, with both families found in intermediate frequency in health care-associated settings (eg, nursing homes, dialysis centers). More work is needed to identify effective barrier precautions to limit their spread.