Contact lenses coated with protamine reduce bacterial adhesion and the production of Contact Lens Induced Acute Red Eye (CLARE)

Abstract

Abstract: : Purpose: Microbial adhesion to contact lenses is associated with the production of many adverse responses such as microbial keratitis, contact lens induced acute red eye (CLARE) and contact lens induced peripheral ulcers. Our aim was to develop a contact lens coating that could inhibit bacterial adhesion and prevent adverse responses in an animal model. Methods: A range of cationic peptides/proteins were examined in solution and once bound to a contact lens for their ability to inhibit microbial growth, reduce microbial adhesion and prevent the formation of CLARE in an animal model. Pseudomonas aeruginosa and Staphylococcus aureus were the predominant bacteria studied as these are commonly associated with contact lens adverse responses. Activity in solution was measured by inhibition of growth and the MIC of certain cationics was measured. The cationics showing the best growth inhibition were adsorbed onto HEMA–based contact lenses and adhesion of bacteria measured. Finally, protamine, covalently bound to a contact lens was examined for its ability to prevent bacterial adhesion and reduce CLARE in an animal model. Results: The cationics that performed the most successfully in solution were Protamine (against P. aeruginosa, S. epidermidis, S. marcescens), Melittin (P. aeruginosa, S. aureus, S. epidermidis), Cecropin A (P. aeruginosa), Magainin 2 (P. aeruginosa), Beta–defensin (P. aeruginosa), Colicin (P. aeruginosa, S. aureus) and Nisin (P. aeruginosa). The maximum reduction in viability was observed after 24h incubation. The MIC for Protamine was >1000ug/ml for P. aeruginosa and for Melittin was 15ug/ml for S. aureus. Protamine and Melittin were individually adsorbed to lenses. Protamine reduced adhesion of P. aeruginosa by 80% but S. aureus by –50%. Melittin reduced adhesion of S. aureus by 90% but P. aeruginosa by 20%. Melittin, but not protamine, caused an increase in corneal staining when bound to a contact lens placed in an animals eye in the absence of bacteria. Protamine–coated lenses were able to prevent CLARE occurring in a rabbits eye in the presence of high numbers of P. aeruginosa. Conclusions: Protamine–coated lenses appear to be able to prevent adhesion of P. aeruginosa and the production of adverse responses due to P. aeruginosa in an animal model.

Keywords: Pseudomonas • contact lens • antibiotics/antifungals/antiparasitics