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Comparative Sensitivity of Trichophyton and Aspergillus Conidia to Inactivation by Violet-Blue Light Exposure
Sian Moorhead1, Michelle Maclean1, Scott J MacGregor1
1The Robertson Trust Laboratory for Electronic Sterilisation Technologies, University of Strathclyde , Glasgow, Scotland, United Kingdom .
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-log10 reduction of a 5-log10 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.
Insights
Violet-blue light (405 nm) effectively inhibits dermatophytic fungi like Trichophyton species. This novel approach shows potential for treating fungal infections resistant to conventional methods.
Area of Science:
- Photomedicine
- Antimicrobial therapies
- Mycology
Background:
- Dermatophytic fungal infections are increasing in incidence and resilience.
- There is a critical need for alternative treatment strategies.
- Violet-blue light therapy presents a potential novel approach.
Purpose of the Study:
- To investigate the efficacy of 405 nm light in inhibiting the growth of dermatophytic and saprophytic fungi.
- To compare the sensitivity of Trichophyton species and Aspergillus niger to 405 nm light exposure.
Main Methods:
- Microconidia of Trichophyton rubrum and Trichophyton mentagrophytes, and conidia of Aspergillus niger were cultured on agar plates.
- Fungal cultures were exposed to 405 nm light emitted by an indium-gallium-nitride light-emitting diode (LED) array.
- Inhibition of fungal germination and growth was measured at various light doses and irradiances.
Main Results:
- Complete inhibition of Trichophyton microconidia germination was achieved at 35 mW/cm² for 4 hours (504 J/cm²).
- Aspergillus niger exhibited greater resistance, with colonial growth observed post-irradiation.
- In liquid suspension, 405 nm light at doses up to 1440 J/cm² completely inactivated Trichophyton microconidia, while achieving only a 3-log10 reduction in Aspergillus niger conidia.
Conclusions:
- Trichophyton microconidia demonstrate significant sensitivity to 405 nm violet-blue light.
- This finding suggests a potential therapeutic application for 405 nm light in managing dermatophyte infections.
- Further research may explore optimizing light parameters for clinical use.
