Increasing frequency of onychomycoses--is there a change in the spectrum of infectious agents?

Abstract

The recently developed antifungal drugs are not equally effective against the fungi causing onychomycoses: dermatophytes, yeasts and non-dermatophyte filamentous fungi (NDFF). Therapeutic failures may be due to the use of antifungal agents not primarily effective against the particular fungus. Considering the high costs of systemic antifungal therapy, it is necessary to know the frequency distribution of the different fungi causing onychomycosis. In a retrospective study, we have analysed results of fungal cultures performed between 1974 and 1994. In particular, we have compared the time periods 1982-1984 and 1992-1994. Culture results from toe nails showed in 1982-1984 the following fungal pattern (n = 833): dermatophytes 61%, yeasts 15%, NDFF 17%, mixed infections 7%. Results from 1992-1994 (n = 930) revealed an increase of dermatophytes 86% at the expense of yeasts (7%), NDFF (3%) and mixed infections (3%). In finger nails, we found a more pronounced change of infectious agents from 1982-1984 (n = 509; dermatophytes 62%, yeasts 29%, NDFF 1%, mixed infections 7%) to 1992-1994 (n = 348; dermatophytes 45%, yeasts 52%, NDFF 0.3%, mixed infections 3%). The high rate of yeast isolations (52%) from finger nails in 1992-1994 is striking. The role of yeast isolates for pathogenesis of onychomycosis remains to be elucidated. Differentiation between colonisation and infection would be necessary. The effectiveness of oral antifungal drugs against dermatophytic nail infections is well documented. The effectiveness against yeasts and NDFF, however, has not been studied thoroughly, but is not supposed to be equal with the different antifungal agents. Determination of the infectious agents in onychomycoses is recommended in order to avoid therapeutic failures.