Paracoccidioides brasiliensis

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.

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.

Penicillium marneffei

Penicillium marneffei
WARNING: RG-3 organism. Cultures of Penicillium marneffei may represent a biohazard to laboratory personnel and should be handled with caution in an appropriate pathogen handling cabinet. P. marneffei exhibits thermal dimorphism and is endemic in Southeast Asia and the southern region of China.
On Sabouraud's dextrose agar at 25C, colonies are fast growing, suede-like to downy, white with yellowish-green conidial heads. Colonies become greyish-pink to brown with age and produce a diffusible brownish-red to wine red-pigment. Conidiophores are hyaline, smooth-walled and bear terminal verticils of 3 to 5 metulae, each bearing 3 to 7 phialides. Conidia are globose to subglobose, 2 to 3 um in diameter, smooth-walled and are produced in basipetal succession from the phialides.
On brain heart infusion (BHI) blood agar incubated at 37C, colonies are rough, glabrous, tan-colored and yeast-like. Microscopically, yeast-cells are spherical to ellipsoidal, 2 to 6 um in diameter, and divide by fission rather than budding. Numerous short hyphal elements are also present.

Clinical significance:

Penicillium marneffei exhibits thermal dimorphism by growing in living tissue or in culture at 37C as a yeast-like fungus or in culture at temperatures below 30C as a mould. This fungus has been isolated from bamboo rats and is endemic in Southeast Asia and the southern region of China. Over 30 cases of hyalohyphomycosis cause by P. marneffei, especially in AIDS patients have now been reported.