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

OBJECTIVE: To determine the potential for visible light (405 or 624 nm) to produce an inhibitory effect on Candida albicans. In addition, the study sought to evaluate a series of doses in terms of their respective inhibiting capabilities. BACKGROUND DATA: The authors have studied the effect of blue light on Staphylococcus aureus and found that a bactericidal outcome can be obtained with low doses of blue light. METHODS: Candida albicans was tested because of its common appearance in human skin and mucous membrane infections. The organism was treated in vitro with 405-nm (blue) and with 624-nm (red) light emitted from a supraluminous diode array. Doses of 3, 9, 15, 30, and 60 J/cm(2) were used. Colony counts were performed and compared with untreated controls using Student t tests and 1-way analysis of variance with Tukey post hoc analysis. RESULTS: The results revealed no inhibition produced by 405 nm on C albicans (F4,20 = 0.901; P = .482). However, 624 nm did inhibit growth of C albicans at 3, 9, and 30 J/cm(2) (F4,20 = 6.064; P = .002). CONCLUSIONS: Appropriate doses of 624-nm light from a supraluminous diode array can inhibit the growth of C albicans in vitro. Three, 9, and 30 J/cm(2) are all effective dose levels.

Ultraviolet C inactivation of dermatophytes: implications for treatment of onychomycosis.

BACKGROUND: Onychomycosis responds to systemic antifungals and sometimes to topical lacquers, but alternative treatments are desirable. Topical application of germicidal ultraviolet (UV) C radiation may be an acceptable and effective therapy for infected nails. OBJECTIVES: To test the ability of UVC to inactivate dermatophyte suspensions in vitro and to sterilize a novel ex vivo model of nail infection. METHODS: Trichophyton rubrum, T. mentagrophytes, Epidermophyton floccosum and Microsporum canis suspensions were irradiated with UVC (254 nm) at a radiant exposure of 120 mJ cm(-2) and surviving colony-forming units quantified. T. rubrum infecting porcine hoof slices and human toenail clippings was irradiated with UVC at radiant exposures of 36-864 J cm(-2). RESULTS: In vitro studies showed that 3-5 logs of cell inactivation in dermatophyte suspensions were produced with 120 mJ cm(-2) UVC irradiation. Depending on factors such as the thickness and infectious burden of the ex vivo cultures, the radiant exposure of UVC needed for complete sterilization was usually in the order of tens to hundreds of J cm(-2). Resistance of T. rubrum to UVC irradiation did not increase after five cycles of subtotal inactivation in vitro. CONCLUSIONS: UVC irradiation may be a less invasive treatment option for onychomycosis, when the appropriate consideration is given to safety.