Susceptibility of Trichopyton mentagrophytes to Visible Light Wavelengths.

OBJECTIVE: To determine whether a blue light (405 nm) could inhibit the growth of Trichopyton mentagrophytes without using a photosensitizing material as part of the treatment protocol.

DESIGN: Basic physiologic randomized trial using laboratory specimens (T mentagrophytes).

INTERVENTIONS/METHODS: Plated on a growth medium, T mentagrophytes were exposed to 3 to 5 administrations of blue light at 20 J/cm over 28 hours. Following 7 days of incubation, colony-forming units were counted and compared with nonirradiated controls.

RESULTS: The study found 3, 4, and 5 administrations of blue light produced significant inhibition of T mentagrophytes (P < .05); 4 and 5 applications produced the greatest inhibition of growth (84.7% and 93.6% kill rates, respectively).

CONCLUSIONS: The application of 405-nm light at a dose of 20 J/cm is an effective in vitro inhibitor of T mentagrophytes. To give results similar to those seen when a photosensitizing material is included, 3 to 5 applications of this wavelength and dose condition delivered over 28 hours is likely needed.