Abstract
Purpose:
In contrast to that used in Europe, the most commonly used corneal storage medium in the United States, Optisol-GS, does not contain an antifungal additive. We previously demonstrated the efficacy of Amphotericin B in reducing Candida albicans contamination of Optisol-GS, as well as its corneal endothelial toxicity at high concentrations. Because Amphotericin B activity is thought to be degraded by exposure to light after 24-96 hours, we sought to determine what role light inactivation of Amphotericin B may play in its efficacy as an antifungal additive in order to determine if this would be a viable method to reduce its endothelial toxicity.
Methods:
Vials of Optisol-GS were supplemented with Amphotericin B at 3 different concentrations (0.06 μg/mL, 0.12 μg/mL and 0.255 μg/mL). Each vial was inoculated with C. albicans. One vial at each of these concentrations was protected from light throughout the study while the other vial was exposed to light after 24 hours. The vials were refrigerated at 4oC. Samples from each vial were collected and plated on days 2, 7, and 14. Plates were incubated for 48 hours after which fungal colony counts were performed.
Results:
There was no growth of C. albicans in any of the Amphotericin B supplemented Optisol-GS vials on days 7 and 14. Minimal growth was observed at the lower concentrations (0.06 μg /mL and 0.12 μg /mL) of Amphotericin B on day 2, but the mean number of colonies was decreased by 78% at both of these concentrations when compared to Optisol-GS without antifungal additive. There was no statistically significant difference in C. Albicans growth between the light-exposed and light-protected vials at any concentration on any day of the study (p=0.58).
Conclusions:
Our study confirms the efficacy of Amphotericin B in Optisol-GS corneal storage media, even at low concentrations. There was no statistically significant difference in efficacy in the light-exposed and light-protected groups, suggesting that if light exposure of Amphotericin B is shown to reduce its corneal toxicity in future studies, it would not have an impact on its efficacy.