ALTERNARIA

SPECIES

Alternaria spp.

MICROSCOPIC APPEARANCE

Hyphae septate appear brown. Conidiophores are brown, septate, simple or branched. Conidiophores are scarcely if ever geniculate. Conidia and poroconidia appear brown, muriform, ovoid or obclavate, with an elongated, beak-like apical cell, often in chains and sometimes solitary. Conidia are large (7-10 by 23-24 micrometers).

MACROSCOPIC APPEARANCE

Surface: Texture downy to wooly, color pale gray to olive brown on surface. May eventually become covered by short, grayish, aerial hyphae.
Reverse: Brown to black.
Growth Rate: Rapid growth.

DISTINGUISHING FEATURES

Alternaria can usually be distinguished from Ulocladium by its obclavate conidia with a beak at the apex. Its conidiophores are comparatively less geniculate than those of Ulocladium , and its conidia are typically in chains, while those of Ulocladium are mostly formed singly or only in very short chains. Pithomyces , unlike Alternaria does not produce conidia in chains.

HABITAT

Alternaria are cosmopolitan, predominately isolated from plants, either as pathogens or as saprobes, and from soil.

PATHOGENICITY

Occasional agents of onychomycosis, of ulcerated cutaneous infection, and of the chronic sinusitis. Rare cases of deep infection have also been reported in the immunocompromised patient. Alternaria is considered to be a common laboratory contaminant and allergen.

RECOMMENDED MEDIA

Incubate at 25 degrees C. for 2 - 7 days.

REFERENCES

1. Hensyl, William R., et al. 1990. Stedman's Medical Dictionary , 25th ed. Williams & Wilkins, Baltimore, MD.

2. St. Germain, Guy and Summerbell, Richard, Ph.D. 1996. Identifying Filamentous Fungi , 1st ed. Star Publishing Company, Belmont, CA.

3. Larone, Davise H. 1995. Medically Important Fungi, A Guide to Identification . 3rd ed. American Society for Microbiology Press, Washington, D.C.

4. The Oxoid Vade-Mecum of Microbiology . 1993. Unipath Ltd., Basingstoke, UK.


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