Electron microscopic studies of the invasion of human hairin vitroby three keratinophilic fungi

Ultrastructural aspects of hair digestion in black piedra infection

“…In P. hortae the disruption produced on the hair cuticle has been attributed to the mechanical pressure produced by the fungal growth [7,14]. Similar effects have been described in other studies [28,29,33,37]. This was also observed in our case as some mechanical pressure may be suspected when the expansion of the fungus, at the cuticle and at the cortex level, continued at a faster rate than the lysis of the surrounding structures.…”

“…The initial invasion of human hair by P. hortae was achieved by producing eroding hyphae which force their way beneath or between the cuticular scales, as described in other fungi [25,33]. However, the presence of perforating organs or fronds as occurs in some keratinophilic fungi [24,25,33,35,36] has not been observed. In P. hortae the disruption produced on the hair cuticle has been attributed to the mechanical pressure produced by the fungal growth [7,14].…”

“…However, further research is needed to ascertain this supposition. The natural selfdegeneration of the fungal cells involved in the hair breakdown at the later stages of hair destruction [26,30,33,34] was not observed in P. hortae. This can be due to the stromatic compacted organization of the fungal nodule that may behave as a resistant structure with a slow development, and therefore small amounts of keratin seem to be sufficient to guarantee the long survival of the fungus.…”

“…In P. hortae, regions with a complete disruption of cuticular scales show a total alteration even of this hard structure. As previously commented, the course of destruction of human hair has been extensively investigated for dermatophytes, Trichophyton mentagrophytes being probably the most well known [26,[32][33][34]38]. This fungus has strong keratinolytic activity being able to destroy both the cuticle and the cortex of the hair, producing big empty zones of lysis [26].…”

The Localization and Secretion of a Proteolytic Enzyme Complex by the Dermatophytic Fungus Microsporum canis

“…In view of the ecological association of dermatophytes with keratinized tissues both as saprophytes and as parasites there is reason to suppose that a study of the proteolytic systems of these fungi will shed light on the mechanism of pathogenesis. That dermatophytes are actively keratinolytic in their saprophytic stage is well established (Mercer & Verma, 1963 ;English, 1963English, ,1968Mathison, 1964;Weary, Canby & Crawley, 1965;Baxter & Mann, 1969). Keratinolysis, as distinct from the proteolysis of less recalcitrant epidermal proteins, is probably less important in vivo once the mycelium is established in the epidermis.…”