Culturing dermatophytes rapidly from each toe web by fingertip

The diagnosis of tinea pedis is usually confirmed by microscopy and culture of skin scrapings. Isolating dermatophytes by fungal culture gives more reliable proof of infection and has the advantage of identifying the causative organisms. Nevertheless, culture examination is complementary to microscopy and is not routinely performed because it is time- and cost-consuming. Herein, we propose a new culturing method, the 'finger-sampling method', for collecting dermatophytes from patients' toe webs using the examiner's fingertip as a sample collection tool. Using this method, four toe webs of a foot can be examined at one time on one culture dish. Every toe web of 50 patients with untreated tinea pedis were examined, and dermatophytes were grown from 83 out of 107 (78%) KOH positive toe webs. The isolation ratio by the finger-sampling method was comparable to that by traditional slant culture of skin scrapings performed by skilled practitioners. Culture results were also positive in 19 out of 53 (36%) diseased but KOH negative toe webs and in 38 (16%) normal toe webs, suggesting the existence of unidentified infection. Additionally, we confirmed the efficacy of this method for detecting dermatophyte attachment on the healthy toe web skin of volunteers who had just been exposed to contaminated areas, i.e. Japanese public baths or a bath mat stepped on by a patient disseminating dermatophyte propagules.