Protein deposition and its effect on bacterial adhesion to contact lenses

PURPOSE: Bacterial adhesion to contact lenses is believed to be the initial step for the development of several adverse reactions that occur during lens wear such as microbial keratitis. This study examined the effect of combinations of proteins on the adhesion of bacteria to contact lenses. METHODS: Unworn balafilcon A and senofilcon A lenses were soaked in commercially available pure protein mixtures to achieve the same amount of various proteins as found ex vivo. These lenses were then exposed to Pseudomonas aeruginosa and Staphylococcus aureus. Following incubation, the numbers of P. aeruginosa or S. aureus that adhered to the lenses were measured. The possible effect of proteins on bacterial growth was investigated by incubating bacteria in medium containing protein. RESULTS: Although there was a significant (p < 0.003) increase in the total or viable counts of one strain of S. aureus (031) on balafilcon A lenses soaked in the lysozyme/lactoferrin combination, the protein adhered to lenses did not alter the adhesion of any other strains of P. aeruginosa or S. aureus (p > 0.05). Growth of S. aureus 031 (p < 0.0001) but not of P. aeruginosa 6294 was stimulated by addition of lysozyme/lactoferrin combination (2.8/0.5 mg/mL). Addition of lipocalin did not affect the growth of any strains tested (p > 0.05). CONCLUSIONS: Adsorption of amounts of lysozyme and lactoferrin or lipocalin equivalent to those extracted from worn contact lenses did not affect the adhesion of most strains of S. aureus or P. aeruginosa to lens surfaces.