Scopulariopsis brevicaulis: a keratinophilic or a keratinolytic fungus?

The morphologic expression of human hair and nail invasion in vitro by Scopulariopsis brevicaulis isolates was studied by light microscopy on whole material and on semi-thin sections, and also by scanning and transmission electron microscopy. Only three isolates of the nine that were examined were keratinolytic, capable of both attacking keratinic substrates and demolishing their keratin. The process showed all the characteristic of enzymatic digestion and was in agreement with the biochemical and morphogenetic scheme proposed for other keratinolytic fungi during their invasion of human hair in vitro. All the active isolates were capable of developing structures related to surface erosion and radial penetration contemporaneously. However the extent and rate of keratinolysis were rather low when compared with the efficiency of other keratinolytic fungi. This finding suggests that S. brevicaulis is of secondary importance in the mineralization of keratinic substrates in natural environments. From the medical standpoint the mere demonstration of keratinolytic activity means that it may be regarded as a real cause of primary infection.