BINDING OF STAPHYLOCOCCUS-AUREUS TO FIBRONECTIN AND GLYCOLIPIDS ON CORNEAL SURFACES

Staphylococcus aureus is one of the most common pathogens of bacterial corneal ulcers. It is generally believed that the first step necessar y in the development of an infection involves adherence of bacteria to host tissue. The mechanisms by which staphylococci adhere to ocular e pithelium have not yet been defined. An in vitro assay was used to mea sure binding of S. aureus and Streptococcus pyogenes to a cornea epith elial cell line. Reduction of the amount of cell-surface fibronectin b y proteinase treatment decreased the adherence of S. pyogenes to a gre ater degree than that of S. aureus. The significantly higher number of staphylococci adhering to the cells as compared with S. pyogenes (P<0 .001) suggests the presence of additional binding sites for S. aureus. Using a thin-layer chromatogram overlay assay, we showed binding of S . aureus to various glycolipids extracted from corneal epithelial cell s and corneal tissue. S. aureus was found to bind to gangliosides and asialo-GM1, whereas S. pyogenes did not bind to any of these complex l ipids. The increased adherence potential of S. aureus due to the abili ty to bind to glycolipids may provide a selective advantage for S. aur eus and explain the prevalence of this organism in bacterial corneal u lcers.