[Fungal nail infections - an update. Part 2 - From the causative agent to diagnosis - conventional and molecular procedures].

Trichophyton (T.) rubrum is the most frequently isolated dermatophyte in onychomycosis, both in Germany and worldwide. T. interdigitale (formerly T. mentagrophytes var. interdigitale) follows in second place. A further however rarely isolated dermatophyte in onychomycosis is Epidermophyton floccosum. Candida parapsilosis, Candida guilliermondii, and Candida albicans, followed by Trichosporon spp. are the most important yeasts which are found in onychomycosis. The molds most often responsible include Scopulariopsis brevicaulis, and several Aspergillus species, e. g. Aspergillus versicolor, and Fusarium spp. These so called non-dermatophyte molds (NDM) are increasingly isolated as emerging pathogens in onychomycosis. The diagnosis of onychomycosis should be verified in the mycology laboratory. Conventional diagnostic methods include the direct examination, ideally using fluorescence staining with Calcofluor® or Blancophor®, and culture. However, new molecular biological methods primarily employing the polymerase chain reaction (PCR) for direct detection of dermatophyte DNA in skin scrapings and nail samples have been introduced into routine mycological diagnostics. The diagnostic sensitivity is higher when both conventional and molecular procedures are combined.