Inactivation of Candida albicans following exposure to 624-nanometer light from a supraluminous diode array

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.

Inactivation of Salmonella on tainted foods: using blue light to disinfect cucumbers and processed meat products

Foodborne illness resulting from infectious organisms occurring in vegetables and processed meat is a serious health concern in the United States. Improved and cost-effective techniques for disinfection are needed. Visible light in the blue range (405 nm) was administered to processed meat that had been inoculated with Escherichia coli. One application of light energy at doses of 10, 30, 60, and 100 J/cm² was applied, in vitro. In the case of vegetables contaminated with Salmonella (cucumbers), 464 nm light was used at 6, 12, and 18 J/cm². In both cases, after 20 hours of incubation, colony-forming units were counted and compared to controls to determine whether the light energy inhibited growth of E. coli or Salmonella. E. coli - 405 nm light at doses of 30, 60, and 100 J/cm² were all effective inhibitors of the organism. Kill rates of 75.61 - 96.34% were achieved. Salmonella - 464 nm light at doses of 6, 12, and 18 J/cm² produced significant inactivation of the organism. Kill rates of 80.23-100% were obtained. Blue light, delivered in the wavelength/dose combinations used in this study is an effective inhibitor of both E. coli and Salmonella on actual foodstuffs. Blue light should be considered as a potentially effective tool in the effort to protect humans from foodborne illnesses.