Role of Chrysosporium keratinophillum in the parasitic evolution of dermatophytes

Abstract

Anti-dermatophytic activity of Chrysosporium keratinophillum against species of the genera Trichophyton, Microsporum and Epidermophyton floccosum was tested in vitro. When C. keratinophillum and different species of dermatophytes were inoculated on Sabouraud's dextrose agar plates 2 cm apart, no antagonistic effect of C. keratinophillum on the mycelial growth of dermatophytes was observed. However, conidia production was not observed on the hyphae of Trichophyton rubrum, Trichophyton tonsurans and E. floccosum grown near C. keratinophillum. The secretory substances released by C. keratinophillum inhibited the growth of T. rubrum, T. tonsurans, Trichophyton mentagrophytes var. interdigitale and E. floccosum at a concentration of 2,000 microg ml(-1) when tested by broth dilution technique. No inhibition of the growth was observed for Microsporum gypseum and Microsporum nanum. The anti-fungal activity of secretory substances released by C. keratinophillum was recorded to be heat stable. Results of the present study suggest that the anti-dermatophytic activity of the secretory substances of C. keratinophillum on T. rubrum, T. mentagrophytes var. interdigitale, T. tonsurans and E. floccosum may be responsible in part, for the absence of these dermatophyte species in soil. Considering the global prevalence of C. keratinophillum in soil one may speculate that the anti-dermatophytic activity of C. keratinophillum is one of the early events for the evolutionary divergence of saprophytic archi-dermatophytes to obligate parasitic dermatophyte species.

Does competition for existence pushed the evolution of the ‘once’ saprophytic fungi to parasitic life?

“…Considering the global prevalence of Chrysosporium spp. and in combination with the results in the present study, it is speculated whether the antidermatophytic activity of these fungi might also be one of the early events for the evolutionary divergence of some geophilic archi-dermatophyte (saprophytic) to obligate parasitic dermatophyte species (Gokulshankar et al, 2005). The antibiosis of other soil microbes on dermatophytes also cannot be underestimated for such a parasitic evolution of dermatophytes.…”

“…However, the viability of these organisms at least in sterilized soil for a prolonged period cannot be ruled out. The inability to recover these dermatophytes even by plating technique from the sterilized soil when they were inoculated along with C. keratinophillum (Gokulshankar et al, 2005) strongly suggests the possibility of SS released by C. keratinophillum has a definite role in the complete elimination of the dermatophytes. Interestingly, the growth of M. gypseum was not affected by SS produced by C. keratinophillum.…”

“…M. gypseum is a geophilic fungi prevalent throughout the world (Rippon, 1988). The selective ability of M. gypseum to counter the antagonistic activity of the SS of C. keratinophillum may be one of the reasons for worldwide distribution of this fungus in soil (Gokulshankar et al, 2005). The susceptibility of these anthropophilic dermatophytes to intra cellular substances (ICS) of C. keratinophillum is relatively less when compared to the SS secreted by the organism.…”

“…Earlier studies (Gokulshankar et al, 2001;Gokulshankar et al, 2005) on the co-inoculation of different species of dermatophytes and C. keratinophillum in sterilized soil revealed that none of the isolates of T. rubrum, T. mentagrophytes var. interdigitale and E. floccosum could be recovered from soil after 15 th day either by baiting or plating technique.…”

Antagonism of Microsporum species by soil fungi

“…In their study, C. keratinophilum inhibited T. rubrum, Trichophyton tonsurum and T. mentagrophytes, but not M. gypseum and Microsporum nanum. Gokulshankar et al [19] also studied the influence of Chrysosporium species on prevalence of dermatophytes in soil, whereas Tariq and Campbell [20] demonstrated influence of volatile metabolites of Geotrichum on some soil fungi. Ulfig [21] demonstrated that keratinophilic fungi unable to decompose hair exerted larger inhibitory effect on pathogenic dermatophytes in which T. mentagrophytes and Microsporum persicolor were more sensitive.…”