Which dimorphic fungus can produce black, yeast-like colonies after prolonged incubation at 37°C?

Sporothrix schenckii is the dimorphic fungus that can produce black, yeast-like colonies after prolonged incubation at 37°C. This organism is known for its thermostat adaptation where it can exist in a mold form at cooler temperatures (around 25°C) and convert to a yeast form when exposed to higher temperatures, such as those found in the human body (37°C).

This yeast form typically appears as small, round to oval, black colonies, which can be a distinctive feature aiding in its identification in a clinical laboratory setting. The ability to produce these black colonies is associated with the organism's natural properties and its pathogenesis, particularly in cases of cutaneous or lymphocutaneous sporotrichosis.

The other fungi mentioned do not exhibit the same growth characteristics at 37°C. For example, Histoplasma capsulatum, while also dimorphic, primarily produces colonies that differ in appearance and do not typically show blackish coloration. Candida albicans tends to produce creamy to white colonies and does not exhibit the same unique characteristics of Sporothrix schenckii. Aspergillus fumigatus belongs to a different category entirely, primarily presenting as mold rather than yeast at body temperature and does not produce black colonies either.