Adherence of arthroconidia and germlings of anthropophilic and zoophilic varieties of Trichophyton mentagrophytes to human corneocytes as an early event in the pathogenesis of dermatophytosis

Abstract

The association (adherence) between human corneocytes and arthroconidia of Trichophyton mentagrophytes strains 121 and 126, and T. interdigitale strain 4 was studied in vitro. Adherence of arthroconidia to corneocytes from either the palm and sole occurred and increased with time up to 6 h, by which time germination of arthroconidia had started. Significant differences were seen between the T. mentagrophytes strains and T. interdigitale in their adherence to corneocytes from the palm. When adherence values for plantar corneocytes were compared, significant differences were found between T. mentagrophytes and T. interdigitale. Not all corneocytes from either site had adherent arthroconidia, although there was a time-dependent increase in the numbers of corneocytes with adherent fungal cells. By scanning and transmission electron microscopy it was seen that there was a loose association between arthroconidia and corneocytes with no apparent damage to the corneocyte membrane. Adherence of germlings of T. interdigitale to corneocytes from the palm appeared to be mediated by germling outer cell wall fibrils. Hyphal branches and secondary germlings were observed to enhance the attachment of the parent hypha to adjacent corneocytes.

Pathogenesis of dermatophytoses

“…[4] The germination of arthroconidia and hyphal growth adherence proceeds radially in multiple directions. [56] Little is known about the factors that mediate adherence of dermatophytes; however, it has been hypothesised that dermatophytic-secreted proteases could facilitate or even be necessary for efficient adherence. The ability of Trichophyton rubrum to adhere to epithelial cells has been attributed to carbohydrate-specific adhesins , expressed on the surface of microconidia.…”

The pathogenesis of dermatophyte infections in human skin sections

“…1 -3 As an alternative to these models, other researchers used non-invasive methods obtaining sheets of stratum corneum stripped by an adhesive tapes, 4 -6 or obtaining separate corneocyte cells and used them as skin surface for dermatophyte infections. 7,8 Still, the nature of the interaction between dermatophytes and skin cells, needs more elucidation and require further investigation. In order to characterize initial adherence and invasion steps, we infected and examined ex vivo skin sections by scanning and transmission electron microscopy.…”

New Insights in Medical Mycology

“…Growing hyphae radiate from the initial cell contact but can be seen to grow towards and into holes in any underlying surface, mimicked in vitro by growth across and through a porous structure such as a Millipore membrane (Aljabre et al, 1992(Aljabre et al, , 1993. This is likely to be mirrored in vivo by the ability of growing hyphae to take advantage of small breaks in the stratum corneum and penetrate between cells.…”