Staphylococccus pseudintermedius surface proteins SpsD and SpsO mediate adherence to ex vivo canine corneocytes

The Gram-positive bacterium Staphylococcus pseudintermedius is regarded as the major cause of canine bacterial pyoderma. Despite its clinical importance, there is only very limited knowledge about the pathogenesis of S. pseudintermedius infection and the specific bacterial virulence factors involved in causing disease. Using a whole-genome approach, we have previously identified 18 predicted cell-wall-anchored surface proteins representing possible virulence factors in a clinical isolate of S. pseudintermedius (strain ED99). They were designated S. pseudintermedius surface proteins A-R (SpsA-SpsR). The present study tested three of the putative Sps proteins (SpsD, SpsL and SpsO) for their ability to mediate adherence of bacteria to canine corneocytes. The three proteins were expressed on the surface of the nonpathogenic surrogate host Lactococcus lactis, a Gram-positive bacterium that does not adhere to canine corneocytes. Adherence assays were performed using corneocytes from different healthy canine donors (n = 5), and bacterial cells were quantified using computerized image analysis. Two of the proteins, SpsD and SpsO, mediated adherence of L. lactis to canine corneocytes, suggesting that they contribute to S. pseudintermedius pathogenesis and may represent novel therapeutic targets to combat infection.