Background.Recent worldwide reports of community‐onset skin abscesses, outbreaks of furunculosis, and severe pneumonia associated with methicillin‐resistant Staphylococcus aureus (MRSA) carrying Panton‐Valentine leukocidin (PVL) genes and the staphylococcal cassette chromosome mec (SCCmec) type IV indicate that MRSA infections are evolving into a community‐related problem. The majority of cases reported to date involve skin and soft‐tissue infections, with severe pneumonia representing a relatively rare phenomenon. During a 2‐month period in the winter of 2003–2004, four healthy adults presented to 1 of 2 Baltimore hospitals with severe necrotizing MRSA pneumonia in the absence of typical risk factors for MRSA infection.

Methods.Patients’ MRSA isolates were characterized by strain typing with use of pulsed‐field gel electrophoresis and SCCmec typing with use of a multiplex polymerase chain reaction (PCR) assay and detection of PVL genes by PCR.

Results.All 4 patients’ MRSA isolates carried the PVL genes and the SCCmec type IV element and belonged to the USA300 pulsed‐field type. These 3 findings are among the typical characteristics of community‐onset MRSA strains. In addition, 2 of our patients had concomitant influenza A diagnosed, which likely contributed to the severity of their presentation.

Conclusions.To our knowledge, these patients represent the first reported North American adults with severe community‐onset MRSA pneumonia caused by strains carrying the PVL genes.