Journal of Mazandaran University of Medical Sciences (Oct 2024)
Current Classification of Dermatophytes and Their Pathogenic Factors
Abstract
The nomenclature of fungi has undergone significant changes in the last decade. Renaming of fungi has always occurred and will continue, largely due to the influence of molecular methods in taxonomy, diagnosis, and epidemiology. Recently, advancements in molecular techniques and genetic analysis have have led to changes in the classification of dermatophytes that could potentially affect the clinical diagnosis and management of the disease. Fungal culture is still considered the "gold standard" for the diagnosing dermatophytosis; however, modern molecular assays have overcome the major drawbacks of culture and can be used in conjunction with it. Dermatophytes are one of the oldest groups of microorganisms known to cause disease in humans and animals. The ability of dermatophytes to secrete keratinolytic enzymes in vitro has led to the study of secretory proteases. Studies on the quantity and function of keratinolytic proteases produced by dermatophytes are increasing, and the enzymatic properties of these compounds have been investigated. Because of the importance of this group of fungi in public health, this review focuses on the new classification of dermatophytes, including the renaming of important medical species, as well as the pathogenic factors associated with them. The search strategy used was a narrative review, using national and international sources such as PubMed, Web of Science, Google Scholar, Scopus, and the country's periodicals database to collect information. In the proposed new classification, Arthroderma includes 21 species, Trichophyton 16, Nanzia 9, Microsporum 3, Paraphyton 3, Epidermophyton and Lophophyton one each. However, more detailed studies are needed to determine the boundaries of these species. Based on previous studies, it can be concluded that the current classification of common anthropophilic dermatophytes is fairly stable and is unlikely to change drastically in the future. While the study of geophilic dermatophytes has been inadequate compared to many zoophilic species, further taxonomic innovation in these groups is expected. In addition, research into the pathogenic mechanisms of dermatophytes has shown that endopeptidases and exopeptidases play an important role in the pathogenesis of dermatophytes by degrading keratin and converting it into free peptides and smaller amino acids. The most important endopeptidases are from the fungilysin family (M36) and two genes encoding MEP1 and MEP5, while the most important extracellular aminopeptidases are the leucine aminopeptidases Lap1 and Lap2 (M28A family) and the dipeptidyl peptidases DppIV and DppV, which are considered to be dermatophyte exopeptidases. The results of previous studies suggest that by identifying these major proteases, it is possible to isolate and identify dermatophyte species. Based on the results of this study, many factors related to the classification and pathogenesis of dermatophytes remain inadequately expressed in existing research. However, the factors discussed in this study serve as a guide for the identification of relevant factors.
