SPOROTHRIX

SPECIES - DIMORPHIC FUNGUS

MICROSCOPIC APPEARANCE

at 25 degrees C.:
Hyphae septate, hyaline. Conidiophores little differentiated from vegetative hyphae; conidia hyaline to brown, ovoid, thin-walled, grouped in rosettes at the tips of the conidiophores; brown conidia, ovoid or sometimes triangular, thick-walled, attached directly to the sides of hyphae.


at 37 degrees C. on a rich medium:
Yeasts ovoid or elongate, producing one or several buds.

MACROSCOPIC APPEARANCE

at 25 degrees C.:
Surface: Texture glabrous to moist; Whitish to black on surface.
Reverse: Whitish to black.
Growth Rate: Rapid to very rapid growth.


at 37 degrees C. on rich medium or in infected tissues:
Surface: Texture creamy; Color cream to beige on surface.
Reverse: Cream to beige.
Growth Rate: Moderately rapid growth.

DISTINGUISHING FEATURES

S. schenkii is distinguished by its grayish to black colonies in Potato Glucose Agar, its hyaline conidia disposed in rosettes on denticles at the tips of conidiophores, and its brown, thick-walled conidia attached along the hyphae. In addition, it converts to a yeast phase at 37 degrees C. on rich media. Other non-pathogenic Sporothrix species may in some cases convert to a yeast phase at 37 degrees C. but do not produce brown, thick-walled conidia around the hyphae. Ophiostoma stenoceras , a normally non-pathogenic species isolated occasionally in the clinical laboratory, possesses a Sporothrix state and produces its characteristic long-necked perithecia after 2-3 weeks of incubation.

HABITAT

Cosmopolitan, isolated mainly from soil, from decomposing plant material, and living plants. Peat moss and thorny bushes are particularly well known sources.

PATHOGENICITY

Sporothrix schenckii is the agent of sporotrichosis, an infection which is most commonly chronic and subcutaneous, or progressive and lymphocutaneous. The disease may become systemic, disseminating most commonly to the skeletal system. Primary pulmonary sporotrichosis occurs with prevalence among chronic alcoholics, but rarely also may manifest in an opportunistic respiratory or disseminated form. It affects both humans and animals.

RECOMMENDED CULTURE MEDIA

Mycelial phase:

Incubate at 25 degrees C. for 10 days.

Yeast phase:

Incubate aerobically at 35 degrees C. for 10 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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