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Ashley Behrens, Andreina Tarff, Rebecca Yee, Ying Zhang; Potential treatment for fungal keratitis by photochemical therapy using BPerox as a new UVA light-sensitive molecule in vitro. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3662. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
The increased incidence of drug resistant ocular pathogens has led to explore new approaches to treat infectious keratitis. The purpose of our study was to use BPerox photochemical therapy as an alternative to antifungal medications.
Cryptococcus neoformans serotype A strain H99 (ATCC208821) was exposed to BPerox chromophore activated by UVA light. Doses were established: 1) BPerox containing RF 0.1% plus hydrogen peroxide 0.004% photoactivated by 3 mW/cm2 UVA for 30 min and 2) BPerox containing RF 0.5% plus hydrogen peroxide 0.004% photoactivated by 10 mW/cm2 UVA for 10 min, both at a total UVA energy dose of 3.4-4 J, through an 8-mm diameter optical diaphragm in 12-well culture plates. The isolate was assessed against the National Committee for Clinical Laboratory Standards by the broth microdilution method using RPMI 1640 medium after incubation for 72 h at 35°C. Previous treatment exposure, the clinical isolate from sterile vials was subcultured at least twice on potato dextrose agar plates to ensure purity and optimal growth. Then, the inoculum was prepared by suspending 5 colonies from a 48-hour-old culture in 5-ml 8.5 g/l NaCl and adjusted to 0.5 McFarland. A working suspension was made by a 1:100 dilution followed by a 1:20 dilution achieving 5.0 x 102 to 2.5 x 103 yeast cells/ml. Control conditions were included, and triplicates were performed. Student’s t-test was used for statistical analysis. P values of < 0.05 were considered statistically significant.
For both treatment doses the susceptibility of C. neoformans was 100% to BPerox photoactivated by UVA (0 yeast cells) in contrast to the none treated control and single treatments such as riboflavin, hydrogen peroxide, BPerox and UVA that harbored at least 3 ± 1.0 × 103 yeast cells/ml (p ≤ 0.0001); riboflavin + UVA, and hydrogen peroxide + UVA showed at least 1.5 ± 1.0 × 103 yeast cells/ml (p ≤ 0.0025).
BPerox-UVA photoactivation seems to be an effective method against encapsulated fungal pathogens in vitro. It might be a potential new treatment for fungal keratitis.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
BPerox-UVA photochemical therapy (last two rows) did not grow fungal cells after culturing. Controls (first two rows) were not able to reduce the fungal burden.
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