PARACOCCIDIOIDES

SPECIES - DIMORPHIC FUNGUS

Paracoccidioides brasiliensis

MICROSCOPIC APPEARANCE

at 25 degrees C.:
Hyphae septate, hyaline, often sterile. Aleurioconidia, arthroconidia and chlamydospores often present, but not a distinctive feature of the species.


at 37 degrees C. on a rich medium:
Yeasts with multiple "satellites", budding.

MACROSCOPIC APPEARANCE

at 25 degrees C.:
Surface: Texture glabrous to velvety; White, pink, beige or brown on surface.
Reverse: Yellowish to brown.
Growth Rate: Rapid to very rapid growth.


at 37 degrees C. on rich medium or in infected tissues:
Surface: Texture creamy; White on surface.
Reverse: White.
Growth Rate: Very slow growth.

DISTINGUISHING FEATURES

Freshly isolated strains may sometimes sporulate weakly on culture media commonly used in medical mycology, but the majority of cultures are sterile. For this reason certain biological safety manuals have now removed this species from their lists of the most highly biohazardous fungi in the laboratory environment. P. brasiliensis is recognized by its yeasts with multiple buds, induced at 37 degrees C. on rich media.

HABITAT

P. brasiliensis has been isolated only on a dew occasions from non-medical sources, chiefly soil and the digestive tracts of animals, and its exact habitat remains unknown. Its geographic distribution is restricted to South America where the majority of cases are diagnosed in Brazil, Venezuela, and Colombia.

PATHOGENICITY

Paracoccidioides brasiliensis is the etiologic agent of paracoccidioidomycosis (South American blastomycosis) or systemic mycoses. This chronic illness, acquired via inhalation, may remain asymptomatic or progress in the form of a pulmonary or disseminated infection, usually producing secondary lesions of the buccal, nasal or gastrointestinal mucosa.

RECOMMENDED CULTURE MEDIA

Mycelial phase:






Potato Dextrose Agar
Sabouraud Dextrose Agar

Incubate aerobically at 25 degrees C. for 15-21 days.

Yeast phase:




Brain Heart Infusion Agar

Incubate aerobically at 35 degrees C. for 7-14 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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