showing typical pyriform to clavate shaped conidia with truncated
bases which may be formed
either intercalary, laterally or terminally.
Colonies are moderately fast growing, flat, white to tan to beige
in colour, often with a powdery or granular surface texture.
Reverse pigment absent or pale brownish-yellow with age. Hyaline,
one-celled (ameroconidia) are produced directly on vegetative
hyphae by non-specialized conidiogenous cells. Conidia are
typically pyriform to clavate with truncate bases (6 to 7 by 3.5
to 4 um) and are formed either intercalary (arthroconidia),
laterally (often on pedicels) or terminally. No macroconidia or
hyphal spirals are seen.
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. The species 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 Clinical Significance
species 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
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.
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.