endopeptidases. These proteases allow T. rubrum to digest human keratin, collagen and elastin; they have an optimum pH of 8 and are calcium dependent. Although T. rubrum shares phylogenetic affiliations with other dermatophytes, it has a distinctive protein regulation system. Transmission This species has a propensity to infect glabrous (hairless) skin and is only exceptionally known from other sites. Transmission occurs via infected towels, linens, clothing (contributing factors are high humidity, heat, perspiration, diabetes mellitus, obesity, friction from clothes). Infection can be avoided by lifestyle and hygiene modifications such as avoiding walking barefoot on damp floors particularly in communal areas. Treatment Treatment depends on the locus and severity of infection. For tinea pedis, many antifungal creams such as miconazole nitrate, clotrimazole, tolnaftate (a synthetic thiocarbamate), terbinafine hydrochloride, butenafine hydrochloride and undecylenic acid are effective. For more severe or complicated infections, oral ketoconazole was historically shown to be an effective treatment for T. rubrum infections but is no longer used for this indication due to the risk of liver damage as a side effect. Oral terbinafine, itraconazole or fluconazole have all been shown to be safer, effective treatments. Terbinafine and naftifine (topical creams) have been successfully treated tinea cruris and tinea corporis caused by T. rubrum. Trichophyton rubrum infections have been found to be susceptible to photodynamic treatment, laser irradiation, and photoactivation of rose bengal dye by green laser light. Tinea unguium presents a much greater therapeutic challenge as topical creams do not penetrate the nail bed. Historically, systemic griseofulvin treatment showed improvements in some patients with tinea unguium; however, failure was common even in lengthy treatment courses (e.g., > 1 yr). Current treatment modalities include oral terbinafine, oral itraconazole, and intermittent "pulse therapy" with oral itraconazole Fingernail infections can be treated in 6–8 weeks while toenail infections may take up to 12 weeks to achieve cure. Topical treatment by occlusive dressing combining 20% urea paste with 2% tolnaftate have also shown promise in softening the nail plate to promote penetration of the antifungal agent to the nail bed. References Parasitic fungi Arthrodermataceae Fungi described in 1845