Ultraviolet C (UV-C) Light Therapy for Equine Ulcerative Keratomycosis-An In Vitro Study.

OBJECTIVES

To assess if an affordable, commercially available 275 nm ultraviolet C (UV-C) device can inhibit fungal pathogens associated with equine keratomycosis and to establish the optimal exposure time/dose required in vitro.

METHODS

Fungal inhibition zone surface areas of isolates from two fungal genera (Aspergillus and Fusarium spp.) were compared in triplicates after UV-C exposure at distances of 10, 15, and 20 mm with single or repeat doses (4 h apart) of 5, 10, 15, or 30 s duration after 24, 48, and 72 h of incubation. Inhibition zones were microscopically assessed, and regrowth checks were performed.

RESULTS

Fungal inhibition was achieved with the lowest exposures/doses of 5 s/7.5 mJ/cm2 and 10 s/7 mJ/cm2 at distances of 10 and 20 mm, respectively. At 10 mm, the fungal inhibition zone was statistically significantly enlarged by increasing exposure/dose from 5 s to 15 s/22.5 mJ/cm2 for all isolates. Only Aspergillus flavus showed a further significant zone enlargement after a 30 s/45 mJ/cm2 exposure/dose. Fungal inhibition zone sizes did not differ significantly between isolates after 15 s exposure regardless of distance, but an increased distance led to a subjective increase in fungal regrowth. While inhibition zones decreased over time, no central growth was noted despite the lack of complete fungal eradication.

CONCLUSIONS

For Aspergillus and Fusarium spp., an exposure/dose of 15 s at a 10 mm distance/22.5 mJ/cm2 may optimally align antifungal efficacy with previously reported corneal safety data. Further preclinical and safety studies are required to ensure that this effect translates into clinical practice.