Adhesion and virulence properties of epidemic Canadian methicillin-resistant Staphylococcus aureus strain 1: identification of novel adhesion functions associated with plasmin-sensitive surface protein.

Epidemic Canadian methicillin-resistant Staphylococcus aureus strain 1 (CMRSA-1) comprises related subtypes that differ in phenotype and prevalence, with subtypes 1A, 1B, and 1D representing 1%, 71%, and 18%, respectively, of total CMRSA-1 isolates. The predominant CMRSA-1B subtype possesses a variant of the staphylococcal cassette chromosome mec, harboring pls, which encodes plasmin-sensitive surface protein (Pls). CMRSA-1B cells that express Pls exhibited poor adhesion to keratinocyte extracellular matrix. However, CMRSA-1B and purified Pls adhered to cellular lipids and glycolipids, and Pls promoted bacterial cell-cell interactions. Although exoprotein expression was restricted to a precursor form of lipase in CMRSA-1B, it was not attenuated in virulence relative to CMRSA-1A, which exhibits normal exoprotein expression. In contrast, CMRSA-1D exhibited a pleiotropic defect in exoprotein expression and attenuated virulence relative to CMRSA-1A. These data indicate that the high transmissibility of CMRSA-1B was not achieved at the expense of attenuated virulence and that Pls confers a novel adhesion mechanism.