A large-scale North American study of fungal isolates from nails: The frequency of onychomycosis, fungal distribution, and antifungal susceptibility patterns

Background: Onychomycosis, a fungal infection of the nail bed, is responsib le for up to 50% of nail disorders. Although several surveys have been cond ucted in different parts of the world, there have been no multicenter epide miologic surveys of onychomycosis in North America. Objective: A 12-center study was undertaken to (1) determine the frequency of onychomycosis, (2) identify organisms recovered from the nails, and (3) determine the antifungal susceptibility of isolates. Methods: ii total of 1832 subjects participated in this study and completed a comprehensive questionnaire, and nail clippings were collected for potas sium hydroxide examination and culturing. Results: The frequency of onychomycosis, as defined by the presence of sept ate hyphae on direct microscopy and/or the recovery of a dermatophyte, was found to be 13.8%. In general, the dermatophyte isolates were susceptible t o the antifungals tested. Conclusion: Because of the limited number of large-scale studies, the basel ine incidence is not firmly established. However, the higher frequency of o nychomycosis in this study may confirm the suspected increase in incidence of disease in North America.