Mechanisms of skin adherence and invasion by dermatophytes

Abstract

SummaryDermatophytes are keratinophilic fungi that can be pathogenic for humans and animals by infecting the stratum corneum, nails, claws or hair. The first infection step consists of adherence of arthroconidia to the stratum corneum. The mechanisms and the kinetics of adherence have been investigated using different in vitro and ex vivo experimental models, most notably showing the role of a secreted serine protease from Microsporum canis in fungal adherence to feline corneocytes. After germination of the arthroconidia, dermatophytes invade keratinised structures that have to be digested into short peptides and amino acids to be assimilated. Although many proteases, including keratinolytic ones, have been characterised, the understanding of dermatophyte invasion mechanisms remains speculative. To date, research on mechanisms of dermatophyte infection focused mainly on both secreted endoproteases and exoproteases, but their precise role in both fungal adherence and skin invasion should be further explored.

Destructin-1 is a collagen-degrading endopeptidase secreted by Pseudogymnoascus destructans , the causative agent of white-nose syndrome

“…Aspartyl and serine peptidases are also associated with dermatophyte fungi, which infect the stratum corneum, nails, and hair of animals; here, they are implicated in promoting adherence to host cells and degradation of keratin during tissue invasion (17,18). Both Candida species and dermatophytes display expanded protein families of peptidases, supporting the idea that these molecules are key virulence factors (15,18).…”

Dermatophyte Growth in Glabrous Skin Dermatophytoses of Immuno Compromised Hosts

“…Dissemination of dermatophytes depends on direct or indirect contacts between infected and uninfected hosts. The first step in the infection process corresponds to colonisation of the cornified layers of the SC [3,4]. Fungal cells representing the contagious and infectious propagules correspond to arthroconidia and hyphal fragments adhering to, or contained within some corneocytes.…”

“…This is the crux of the problem of infections in immunocompromised patients. The adhesion of microorganisms to the stratum corneum (SC) [3,4], and its barrier system represent additive components of the skin protection. …”

Can we Prevent Onychomycosis?

“…With the exception of direct inoculation of the nail plate, tinea pedis precedes DLSO onychomycosis. Studies have shown concurrent active tinea pedis in the majority of onychomycosis cases; undoubtedly, the remaining cases either had treated tinea pedis or non-DLSO subtypes 4-7 Dermatophytes invade the stratum corneum via keratinolytic proteases with hyphae growing in multiple directions [10,11]. Left untreated (or only partially treated), the infection extends from the plantar surface to the distal nail bed causing DLSO [12].…”