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A. Behrens, J. Castro-Combs, G. Noguera, S. Martins; UV-A and Riboflavin: Potential Application as a New Broad-Spectrum Treatment for Infectious Keratitis. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2676.
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UV-A and riboflavin have been proposed in the past for sterilization of blood components. Byproducts of activated riboflavin have been shown to have the ability to act as bactericidal agents. Following the popularity of collagen cross-linking application for corneal ectasias, we propose to use the UV-A/riboflavin technique for corneal infections. The purpose of this study is to demonstrate the antibacterial/antifungal properties of this combination for the potential treatment of infectious keratitis.
Standard Kirby-Bauer disc diffusion method and minimal inhibitory concentration (MIC) tests were performed in four different strains of infectious agents: gram-positive Staphylococcus epidermidis, gram-negative Pseudomonas aeruginosa, filamentary fungus Fusarium oxysporum and the yeast fungus Candida albicans. Initially in each of the dishes, four areas were used in the following fashion: One area with a disc (B-D, Sparks, MD) with no riboflavin, one quadrant with disc and riboflavin alone, one quadrant with a disc and pre-activated riboflavin (previously exposed for one hour to UV-A, 3 mW/cm2) one disc with riboflavin and exposure to UV-A 3 mW/cm2 for 30 min. Different concentrations of riboflavin (0.1%, 1%, and 2.5% were used in the experiments, per triplicate)
All infectious agents were sensitive to 2.5% concentration of riboflavin, either in pre-activated and exposed to UV-A fashion. S. epidermidis and P. aeruginosa were sensitive to concentrations of 1% and above of the pre-activated or exposed to UV-A. The non-exposed riboflavin and the "empty" disc did not show any effect on the dishes.
Pre-activated riboflavin and the combination UV-A/riboflavin may be effective methods of inhibition of bacterial and fungal growth in culture plates. UV-A alone and riboflavin alone do not seem to have any effect as anti-bacterial agents. Further in vivo experiments are underway to test the efficacy of this approach for infectious keratitis.
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