Light resistance in geophilic dermatophytes.
The effect of repeated illumination by ultraviolet or visible light on slide cultures of Trichophyton ajelloi and Microporum cookei was studied. Under UV light, germination was inhibited, spores were damaged and destroyed, growth was suppressed and the hyphae were killed. Inhibition was dependent on exposure time and wavelength. Lethal doses for the far UV range were as high as 1 300-1 700 mW sec/cm2 for T. ajelloi and 2 300 mW sec/cm2 for M. cookei. The same effect was caused by the complete UV region but the far UV range was most effective. One exposure, however long, was not sufficient to kill the inoculum but this was effected by smaller doses when repeated 4 times at daily intervals. Under visible light, germination of the spores and growth of the young hyphae were inhibited. Depending on the exposure time and wavelength used, inhibition of 8 to 76% of controls grown in darkness were noted. The inhibition degree was increased up to lethality when the mycelium was sensitized by means of eosin. The coefficient of variation increased regularly up to very high values following exposures to sublethal doses of light...
D003883:Arthrodermataceae / Q000254:growth & development*; D008027:Light; D008864:Microsporum / Q000254:growth & development / Q000528:radiation effects; D011830:Radiation Effects; D014249:Trichophyton / Q000254:growth & development / Q000528:radiation effects; D014466:Ultraviolet Rays