Paracoccidioides brasiliensis

On Sabouraud's dextrose agar at 25C, colonies are slow growing and variable in morphology. Colonies may be flat, wrinkled and folded, glabrous, suede-like or downy in texture, white to brownish with a tan or brown reverse. Microscopically, a variety of conidia may be seen, including pyriform microconidia, chlamydoconidia and arthroconidia. However, none of these are characteristic of the species, and most strains may grow for long periods of time without the production of conidia.

On BHI blood agar at 37C, the mycelium converts to the yeast phase and colonies are white to tan, moist and glabrous and become wrinkled, folded and heaped. Microscopically, numerous large, 20-60 um, round, narrow base budding yeast cells are present. Single and multiple budding occurs, the latter are thick-walled cells that form the classical "steering wheel" or "Mickey mouse" structures that are diagnostic for this fungus, especially in methenamine silver stained tissue sections.

Multiple, narrow base, budding yeast cells "steering wheels"of Paracoccidioides brasiliensis.

WARNING:  RG-3 Organism.  Cultures of P. brasiliensis represent a severe biohazard to laboratory personnel and must be handled with extreme caution in an appropriate pathogen handling cabinet.

MIC data is limited.  Antifungal susceptibility testing of individual strains is recommended.

Clinical significance:

Paracoccidioidomycosis is a chronic granulomatous disease that characteristically produces a primary pulmonary infection, often inapparent, and then disseminates to form ulcerative granulomata of the buccal, nasal and occasionally the gastrointestinal mucosa. The disease in its inception and development is similar to blastomycosis and coccidioidomycosis. The only etiological agent, P. brasiliensis is geographically restricted to areas of South and Central America.

Mycosis: Paracoccidioidomycosis

Further reading:

Rippon, J.W. 1988. Medical Mycology. 3rd Edition. W.B. Saunders Co., Philadelphia, USA