Aspergillus versicolor as cause of onychomycosis: Report of 12 cases and susceptibility testing to antifungal drugs

Background: Onychomycoses caused by opportunistic moulds are not well understood, and many are due to Scopulariopsis brevicaulis and other species. Aspergillus versicolor is not documented as an etiological agent in most studies. We have found an increasing prevalence of this species which is involved in 5.8% of all fungal infections of toe nails. Objective: To study the clinical and mycological characteristics of the onychomycosis caused by A. versicolor and the in vitro susceptibility of this mould to antifungal agents. Results: Onychomycosis due to A. versicolor is mainly seen in people over 60 and presents with chronic involvement of the big toe nails. Predisposing factors are not always present and the infection does not respond to conventional topical antifungals. In vitro, A. versicolor has been shown to be resistant to griseofulvin and fluconazole as well as to amphotericin B, whereas MICs for itraconazole and ketaconazole are variable but within a range of 0.50-4.0 μg/ml; on the contrary, MICs for terbinafine are very low (< 0.125 μg/ml). Discussion: Aspergillus versicolor could be considered as an emergent pathogen causing toenail onychomycosis. Local treatment seems not be effective. Of the various systemic antifungal agents studied terbinafine appears to be the most effective in treating onychomycosis.