The ability of ocular bacteria to bind to fibronectin

Abstract

Background: Fibronectin enters the tear film during sleep and on reflex tear stimulation. Also, contact lens wearers with increased levels of fibronectin in their tears are more likely to carry greater numbers of bacteria on their contact lenses. This points to a role of fibronectin in mediating adhesion of bacteria to contact lenses.

Methods: Bacterial strains isolated from the eyes of contact lens wearers were examined for their ability to bind to fibronectin. Fibronectin binding was examined in solution or adsorbed onto a surface.

Results: A strain of Pseudomonas aeruginosa isolated at the time of an acute keratitis and a strain of Stenotrophomonas maltophilia isolated from an asymptomatic eye adhered to soluble or adsorbed fibronectin by greater amounts than other species tested (p < 0.01). Using fibronectin derived from plasma (pFn) and fibronectin derived from cells (cFn) it was shown that the addition of cFn in the presence of pFn increased the binding of pFn to cells indicating aggregation or co‐operativity in binding between the two fibronectin types to the cell surface. P. aeruginosa probably bound to both the protein and carbohydrate moieties of fibronectin. Protein(s) on the cell surface of P. aeruginosa probably mediated the adhesion as digestion of cells with protease significantly (p < 0.01) reduced binding.

Conclusions: Bacteria isolated from contact lenses, and in particular gram‐negative bacteria implicated in the production of keratitis, are able to bind to fibronectin. Also, different types of gram‐negative bacteria had distinct abilities to adhere to fibronectin. This may have implications in the binding of these strains to contact lenses in vivo.

Key words:

• adhesion
• contact lenses
• fibronectin
• Pseudomonas aeruginosa