Comparative Sensitivity of Trichophyton and Aspergillus Conidia to Inactivation by Violet-Blue Light Exposure

Objective: To investigate the use of 405 nm light for inhibiting the growth of selected species of dermatophytic and saprophytic fungi. Background data: The increasing incidence and resilience of dermatophytic fungal infections is a major issue, and alternative treatment methods are being sought. Methods: The sensitivity of the dermatophytic fungi Trichophyton rubrum and Trichophyton mentagrophytes to 405 nm violet-blue light exposure was investigated, and the results compared with those obtained with the saprophytic fungus Aspergillus niger . Microconidia of T. rubrum and T. mentagrophytes and conidia of A. niger were seeded onto Sabauroud dextrose agar plates and irradiated with 405 nm light from an indium-gallium-nitride 99-DIE light-emitting diode (LED) array and the extent of inhibition was measured. Results: Germination of the microconidia of the Trichophyton species was completely inhibited using an irradiance of 35 mW/cm 2 for 4 h (dose of 504 J/cm 2 ). A. niger conidia showed greater resistance, and colonial growth developed after light exposure. In liquid suspension tests, 405 nm light dose levels of 360, 720, and 1440 J/cm 2 resulted in complete inactivation of T. rubrum microconidia, whereas A. niger showed greater resistance, and at the highest dose level applied (1440 J/cm 2 ) although A niger hyphae were completely inactivated, only a 3-log 10 reduction of a 5-log 10 conidial suspension was achieved. Conclusions: The study results demonstrate the relatively high sensitivity of Trichophyton microconidia to 405 nm violet-blue light, and this is may be of potential interest regarding the control and treatment of dermatophyte infections.