Description and Natural Habitats
is a keratinophilic filamentous fungus commonly isolated from soil, plant
material, dung, and birds. It lives on remains of hairs and feathers in
soil. The telemorphs of Chrysosporium spp. are included in the genera
Aphanoascus, Nannizziopsis, and Uncinocarpus. As well
as being a common contaminant, Chrysosporium is occasionally isolated
from human infections.
The genus Chrysosporium contains
several species. The most common ones are Chrysosporium keratinophilum, Chrysosporium tropicum, Chrysosporium merdarium,
Chrysosporium inops, Chrysosporium pannicola, Chrysosporium
queenslandicum, and Chrysosporium zonatum. Another species of
special interest, classified as Emmonsia parva on the ecological
basis, is occasionally named as Chrysosporium parvum as well.
of Chrysosporium are differentiated from each other by the texture of
the colony and morphology, location, and size of the conidia. Also, some
species, particularly Chrysosporium pannicola, do not grow at 37°C.
Species of Chrysosporium are
occasionally isolated from skin and nail scrapings, especially from feet,
but because they are common soil saprophytes they are usually considered as
contaminants. There are about 22 species of
Chrysosporium, several are keratinophilic with some also
being thermotolerant, and cultures may closely resemble some dermatophytes,
especially Trichophyton mentagrophytes, and some strains may also
resemble cultures of Histoplasma and Blastomyces.
Pathogenicity and Clinical Significance
may cause skin infections and onychomycosis in humans. In addition to these
superficial infections, Chrysosporium spp. have occasionally been
isolated from systemic infections in bone marrow transplant recipients and
in patients with chronic granulomatous disease. The high mortality rate of
systemic Chrysosporium infections is noteworthy.
colonies grow moderately rapidly at 25°C. The morphology of the colonies is
very variable. They may be granular, woolly, or cottony and flat, or raised
and folded in appearance. From the front, the color is white cream, yellow
or tan to pale brown. The reverse is white to brown.
produces hyphae, conidia (aleuriconidia), and arthroconidia. Hyphae are
septate while the conidia are hyaline, broad-based, one-celled, and smooth-
or rough-walled. These conidia are broader than the vegetative hyphae and
occur terminally on pedicels, along the sides of the hyphae, or in
intercalary positions. The conidia usually have an annular frill which is
the reminant of the hyphal wall that remains after detachment from the hypha.
Arthroconidia, on the other hand, are abundant and larger than their parent
hyphae in diameter. In addition, Chrysosporium parvum forms enlarged,
thick-walled cells (adiaspores) at 37-40°C.
No special precautions other than general
laboratory precautions are required.
Very limited data are available.
Amphotericin B, itraconazole, ketoconazole, and voriconazole tend
to yield low MICs for Chrysosporium keratinophilum isolates.
Fluconazole MICs are relatively higher than those of the just noted
antifungal agents. Flucytosine, on the other hand, appears to have no
in vitro activity against these isolates.