To the Editor: In their study of methicillin-resistant Staphylococcus aureus (MRSA), Dr Klevens and colleagues1 concluded that the majority of invasive infections have onset in the community. They also implied that the majority of community-onset invasive MRSA disease occurred in association with exposure to the health care environment.
An important question is how to define health care environment exposure. For example, 1 component of the definition for health care–associated MRSA used in the study by Klevens et al was documentation of a previous infection or colonization with MRSA. Prior to the onset of epidemic community-based MRSA disease, this criterion worked well to define health care risk because MRSA isolates were largely confined to the health care environment.2 Now, however,
novel MRSA isolates (such as the widely disseminated USA300 clone,
with its molecular characteristics that markedly distinguish it from the well-known health care–based MRSA strains) circulate in the community and infect individuals truly lacking health care environment exposure.3 These community-based MRSA infections often recur.4 Such a recurrence should not be inferred as being due to an exposure to the health care system.
David MZ, Siegel JD, Chambers HF, Daum RS. Determining Whether Methicillin-Resistant Staphylococcus aureus Is Associated With Health Care. JAMA. 2008;299(5):519-520. doi:10.1001/jama.299.5.519-a