Taxonomy Of Dermatophytes – The Classification Systems May Change But The Identification Problems Remain The Same

Fungal infections of the skin, hair, and nails are the most prevalent among all fungal infections, currently affecting over 20–25% of the world’s human and animal populations. Dermatophytes are the etiological factors of the most superficial fungal infections. Among other pathogenic filamentous fungi, what distinguishes them is their unique attribute to degrade keratin. The remarkable ability of this group of fungi to survive in different ecosystems results from their morphological and ecological diversity as well as high adaptability to changing environmental conditions. Dermatophytes, although they are one of the oldest groups of microorganisms recognised as pathogens, have not been classified in a stable taxonomic system for a long time. In terms of diagnostics, dermatophytes still pose a serious problem in the identification procedure, which is often related to therapeutic errors. The increasing number of infections (including zoonoses), the lack of taxonomic stability, and the ambiguous clinical picture of dermatomycosis cases necessitate the search for new methods for the rapid, cheap, and reproducible species identification of these fungi. In turn, the species identification is determined by the clarity of classification criteria combined with the taxonomic division generally accepted by microbiologists and referring to the views expressed by clinicians, epidemiologists, and scientists. In this paper, the authors present the evolution of taxonomic systems for dermatophytes over the history of microbiology development. The discovery of new facts about the biology and ecology of dermatophytes and the development of techniques applied in a mycological diagnosis laboratory facilitated the development of new identification strategies at various points in the history. The modern molecular classification system of these pathogens seems to be stable and widely accepted. However, will it end the long-standing classification confusion and the period of hundreds of nomenclatural changes, which are a diagnostician’s nightmare? It can be argued that the taxonomy of dermatophytes, in particular that of anthropophilic species, is sufficiently established and stable for the benefit of both clinicians and scientists.

1. Introduction. 2. First dermatophyte classification systems. 3. Phenotypic classification systems. 4. “Biological” era in the classification. 5. Ecological division of dermatophytes. 6. Molecular revolution in the taxonomy of dermatophytes. 7. Taxonomic problems in mycology. 8. Clinical aspect of the taxonomy of dermatophytes. 9. Current classification system. 10. Indistinguishable «species complexes». 11. Summary