Causative agents of onychomycosis — a retrospective study

BACKGROUND: Dermatophytes, yeasts and moulds all are potential causative agents of onychomycosis. The aim of this study was to determine the percentage of cases of onychomycoses caused by each group. In addition, the responsible genus and species was identified for each nail infection. PATIENTS AND METHODS: In a retrospective study performed at the Department of Dermatology of the Leipzig University, 5,077 nail samples from 4,177 patients--2,240 women and 1,937 men--with a variety of nail changes--not just onychomycosis--were investigated. 75% were toenails, 23% fingernails, and 2% from both sites. RESULTS: Both microscopic and/or cultural detection of fungi (dermatophytes, yeasts and moulds) were successful in 54% of samples. Causative fungal agents were: 68% dermatophytes, 29% yeast, and 3% moulds. The most frequently detected dermatophyte species were T. rubrum (91%), and T. mentagrophytes (7.7%). Among yeasts, C. parapsilosis (42%) was most common,followed by C. guilliermondii (20.1%), C. albicans (14.2%), and Trichosporon spp. (10%). Scopulariopsis brevicaularis (43%) was the most frequent mould. The percentage of mixed fungal infections was 22%. CONCLUSIONS: Dermatophytes, in particular T.rubrum, but also T. mentagrophytes, are the most frequently isolated causative agents in onychomycosis. In addition, yeasts may be isolated relatively frequently, while moulds are uncommon.