Large-Scale Epidemiological Study of the Causal Agents of Onychomycosis: Mycological Findings From the Multicenter Onychomycosis Study of Terbinafine

Abstract

The spectrum of pathogens in onychomycosis is a subject of debate. Some reports^1,2 suggest an increased importance of yeasts and nondermatophytic molds. The time-honored consensus is that the vast majority of these infections are caused by dermatophytes, particularly Trichophyton rubrum.^3-5 These discrepancies might be due to the pattern of onychomycosis (distal subungual, proximal subungual, or superficial white), fingernail vs toenail site, geographic region, method of specimen collection, and differences in laboratory methodologic procedures and interpretation. The current study was conducted to determine whether the causal agents of onychomycosis have recently shifted in the United States. The largest survey to date, performed in Canada by Summerbell and colleagues,⁶ surveyed more than 4000 patients with fungal nail, hand, and foot infections. Nondermatophytic molds constituted only 3.3% of the fungal isolates; 5.5% of all isolates were Candida. A United Kingdom survey of 699 nail specimens by Clayton⁷ found dermatophytes in 81% of