An investigation into the inhibitory effect of ultraviolet radiation on Trichophyton rubrum

Abstract

Fungal infection of nails, onychomycosis, is predominantly caused by Trichophyton rubrum. This infection is an important public health concern due to its persistent nature and high recurrence rates. Alternative treatments are urgently required. One such alternative is phototherapy involving the action of photothermal or photochemical processes. The aim of this novel study was to assess which wavelengths within the ultraviolet (UV) spectrum were inhibitory and equally important nail transmissible. Initial irradiations of T. rubrum spore suspensions were carried out using a tunable wavelength lamp system (fluence ≤3.1 J/cm(2)) at wavelengths between 280 and 400 nm (UVC to UVA) to evaluate which wavelengths prevented fungal growth. Light-emitting diodes (LEDs) of defined wavelengths were subsequently chosen with a view to evaluate and potentially implement this technology as a low-cost "in-home" treatment. Our experiments demonstrated that exposure at 280 nm using an LED with a fluence as low as 0.5 J/cm(2) was inhibitory, i.e., no growth following a 2-week incubation (p < 0.05; one-way ANOVA), while exposure to longer wavelengths was not. A key requirement for the use of phototherapy in the treatment of onychomycosis is that it must be nail transmissible. Our results indicate that the treatment with UVC is not feasible given that there is no overlap between the antifungal activity observed at 280 nm and transmission through the nail plate. However, a potential indirect application of this technology could be the decontamination of reservoirs of infection such as the shoes of infected individuals, thus preventing reinfection.

The Role of Shoe and Sock Sanitization in the Management of Superficial Fungal Infections of the Feet

“…A total of 33 studies were found, encompassing a broad array of techniques ranging from formalde-hyde fumigation and foot powder application, to more modern approaches such as the use of silverlight irradiation technology and UV light applications (Tables 1-3). 5,[8][9][10][11] The need for sanitization, and sanitization techniques that could be used in the management of superficial fungal infections, were critically reviewed and compared across eligible studies.…”

“…Tanaka et al, 2006 16 Boiling water, cold water, and wiping methods Ghannoum et al, 2012 4 SteriShoe accompanied by a cycle of UVC irradiation Gupta and Brintnell, 2013 14 Ozone application with a drying/ heating component Cronin et al, 2014 11 UV irradiation Messina et al, 2015 5 Cyberclean, a sanitizing putty Abbreviation: PCP, pentachlorophenate. 26,27,47 Bactericides and fungicides English et al, 1967 32 Laundering Broughton, 1955 6 Laundering Tanaka et al, 2006 16 Laundering with or without soap and sock position Borkow and Mellibovsky, 2012 48 Copper oxide Amichai et al, 2013 33 Laundering at 408C or 608C Amichai et al, 2014 22 Sun exposure 36 Laundering and sanitization measures a Jung et al, 2007 37 Silver ion laundry machine He et al, 2008 38 Silver and light irradiation laundry machine Borkow and Gabbay, 2008 29 Copper oxide…”

“…Ultraviolet wavelengths have been examined for their use in sanitization in two eligible studies. 4,11 A fungal reduction in T mentagrophytes was reported when a sanitizer (SteriShoe; Shoe Care Innovations, Inc., Menlo Park, California) was accompanied by one, two, and three cycles of UVC irradiation (one cycle of irradiation, P ¼ .003; two cycles of irradiation, P ¼ .008). 4 An overall 76% fungal reduction in T rubrum-infected shoes also occurred after the SteriShoe sanitizer was accompanied by irradiation; however, no significant difference from control was found.…”

Novel light therapies in treatment of onychomycosis

“…Także Cronin i wsp. [39] wykazali zahamowanie wzrostu T. rubrum po zadziałaniu UVC o długo-ści 280 nm. Ze względu na możliwe działanie mutagenne UVC proponuje się, aby promieniowanie o tej długości wykorzystać w celu odkażania rezerwuarów grzybów, np.…”

The Dermatologist’s Approach to Onychomycosis

“…In 2013, Chronin et al found conflicting results [43]. The study demonstrated that treatment with UVC was not feasible, as UV light would not penetrate the nail until 320nm and wavelengths of 320 nm or greater would not eradicate T. rubrum [46]. …”