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

Abstract

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 (PIs). CMRSA-1B cells that express PIs. exhibited poor adhesion to keratinocyte extracellular matrix. However, CMRSA-1B and purified PIs. adhered to cellular lipids and glycolipids, and PIs. 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 PIs. confers a novel adhesion mechanism.