Tuesday, December 06, 2005

CA-MRSA in perspective

In his post today on Staphylococcal infections RangelMD says methicillin resistant staphylococcus aureus (MRSA) infections are not inherently worse than methicillin sensitive (MSSA) infections, community acquired MRSA (CA-MRSA) is not a “super bug”, and the press has sensationalized and distorted the issue. I agree partially---especially with the point about media distortion. I also agree that the “old fashioned” MRSA is not necessarily more virulent than MSSA, although it may be associated with poorer outcomes related to greater difficulty in treatment and greater comorbidities in MRSA infected populations.

Concerning CA-MRSA, however, I feel some need to elaborate since I have posted about its unique attributes before. [1] [2]. Although its predilection for causing minor skin infections often makes it more of a nuisance than a threat to life there is evidence of uniquely heightened virulence and transmissibility in some CA-MRSA clones. These characteristics are associated with the Panton-Vanentine leukocidin, (PVL) found more frequently in CA-MRSA than in other strains. The PVL gene is only rarely found in hospital associated MRSA and MSSA.

Although the somewhat heterogeneous nature of CA-MRSA makes it difficult to generalize, some trends are emerging which raise concerns about increased transmissibility and virulence.

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