C. immitis is a dimorphic fungus which can be isolated from sputum specimens of infected individuals. When grown on Sabouraud's agar at 25o it grows as a mold with white aerial mycelium in about 3 to 5 days. C. immitis is known to produce arthroconidia which are "barrel-shaped" after 1 to 2 weeks of growth.

Within three days at 28 ºC a sputum specimen placed on Sabouraud's dextrose agar with chloramphenicol and cycloheximide produced moist, grayish growth, with a white aerial mycelium, the organism is MOST likely: