Binding of a surface protein of Staphylococcus aureus to cultured ovine mammary gland epithelial cells.

Staphylococcus aureus is the most persistent pathogen causing ovine mastitis. This study investigated S. aureus binding to cultured epithelial cells obtained from the mammary gland. A staphylococcal 145kDa cell wall adhesin, originally isolated from a bovine mastitis strain, was detected in lysostaphin-solubilized ovine mastitis strains and in the encapsulated strain A. This adhesin was able to bind to cultured ovine mammary gland epithelial cells (MGEC) and to a rat intestinal epithelial cell line (RIE-1), exhibiting different electrophoretic mobilities that could be attributable to protein polymorphism. Inhibition assays using antibodies against 145kDa adhesin and against whole bacteria showed the specificity of the binding to cells. The role of this protein in adherence was assessed by adherence inhibition tests carried out in vitro with radiolabeled bacteria and cultured epithelial cells. Preincubation of bacteria with antibodies against adhesin 145kDa or against strain c195 resulted in a statistically significant decrease of adherence. These experiments suggest that adherence of S. aureus to MGEC may be critical for colonization.