Current Topics in Dermatophyte Classification and Clinical Diagnosis

Abstract

Dermatophytes are highly infectious fungi that cause superficial infections in keratinized tissues in humans and animals. This group of fungi is defined by their ability to digest keratin and encompasses a wide range of species. Classification of many of these species has recently changed due to genetic analysis, potentially affecting clinical diagnosis and disease management. In this review, we discuss dermatophyte classification including name changes for medically important species, current and potential diagnostic techniques for detecting dermatophytes, and an in-depth review of Microsporum canis, a prevalent zoonotic dermatophyte. Fungal culture is still considered the “gold standard” for diagnosing dermatophytosis; however, modern molecular assays have overcome the main disadvantages of culture, allowing for tandem use with cultures. Further investigation into novel molecular assays for dermatophytosis is critical, especially for high-density populations where rapid diagnosis is essential for outbreak prevention. A frequently encountered dermatophyte in clinical settings is M. canis, which causes dermatophytosis in humans and cats. M. canis is adapting to its primary host (cats) as one of its mating types (MAT1-2) appears to be going extinct, leading to a loss of sexual reproduction. Investigating M. canis strains around the world can help elucidate the evolutionary trajectory of this fungi.

Clinical Manifestations of Human Exposure to Fungi

“…Dermatophytes, the etiological agents of dermatophytosis, are keratinophilic fungi living on keratin-rich materials commonly found in the soil and skin (including hair and nails) [ 150 , 151 ]. This group includes the genera Trichophyton , Microsporum , Epidermophyton , Lophophyton , Paraphyton , Nannizzia , and Arthroderma .…”

“…in the scalp, is tinea capitis ( Figure 2 B); a rare variant is tinea capitis favosa , caused by Trichophyton schoenleinii , which occurs in children and adolescents; on the beard and moustache areas of men is tinea barbae ( Figure 2 C); in the hand region is tinea manuum ; in the face is tinea faciei ; on the nails and surrounding tissue is tinea unguium ; in the upper body (trunk, shoulder, armpit, chest, and back) is tinea corporis ( Figure 2 D). Independently of the body location or etiological agent, when the infection is misdiagnosed and masked by topical corticosteroids, it is designated tinea incognito [ 151 , 157 ].…”

Comparison of Adhesive Tape Impression Cytology, Hair Plucks, and Fungal Culture for the Diagnosis of Dermatophytosis in Dogs and Cats

“…Dermatophytes are fungi that degrade keratin, resulting in hair, skin, and claw disease [ 2 , 3 ]. The most common dermatophytes diagnosed in dogs and cats are Microsporum canis ( M. canis ), Microsporum gypseum ( M. gypseum ) [new name, Nannizzia gypsea ( N. gypsea )], and Trichophyton mentagrophytes ( T. mentagrophytes ) [ 3 , 4 , 5 ]. M. canis is the most frequently isolated species, with a prevalence of >90% in cats and 70–80% in dogs [ 1 ].…”

Dermatophytes and Dermatophytoses Acquisition Among School-Age Children in Cameroun, Ivory Coast, Mali and Nigeria: A Systematic Review

“…Farm workers that are exposed to various reservoirs of dermatophytes like mud, cow dung, manure, dust and soil are prone to both superficial and other forms of mycoses [10][11][12] .…”