Emergence of Community-acquired Meticillin-resistant Staphylococcus Aureus Strain USA300 as a Cause of Necrotising Community-onset Pneumonia.

Methicillin-resistant Staphylococcus aureus (MRSA), usually known as a nosocomial pathogen, has emerged as the predominant cause of skin and soft-tissue infections in many communities. Concurrent with the emergence of community-acquired MRSA (CA-MRSA), there have been increasing numbers of reports of community-acquired necrotising pneumonia in young patients and others without the classic healthcare-associated risk factors. Community-onset necrotising pneumonia due to CA-MRSA is now recognised as an emerging clinical entity with distinctive clinical features and substantial morbidity and mortality. The best treatment of this partly toxin-mediated disease has not been clearly defined. Whereas cases of CA-MRSA pneumonia have now been reported from almost every continent, the overall burden of disease of this emerging syndrome remains incompletely described. This paper reports two related cases of community-onset pneumonia due to the MRSA USA300 genotype and reviews the literature regarding the emergence of CA-MRSA pneumonia. Lancet Infect Dis. 2009;9:384-92.