Talaromyces marneffei (formerly known as Penicillium marneffei) produces elongated, ovoid, small (3-5 µm) yeasts that divide by fission rather than by budding. They are often found within histiocytes. T. marneffei forms rapidly growing tan mold colonies that are initially powdery or velvety on the surface and become colored with maturity (typically blue or green centrally) when it is cultured at 25-30ºC. Additionally, a red pigment diffuses into the agar around and underneath the colonies.
Microscopically, the mold colonies are composed of hyaline septate hyphae with conidiophores and metulae producing brush-like clusters of phialides. There are chains of small oval conidia that form at the terminal ends of the phialides. Thermal dimorphism should be demonstrated for correct identification.
The yeast colonies are off-white to pink and consist of small (3-5 µm) oval yeast-like cells that reproduce by fission rather than by budding.
The organism is endemic in Southeast Asia and is not found elsewhere. Those at risk are HIV/AIDS patients. It is acquired via the respiratory route and, in most cases, leads to the involvement of the bone marrow, skin, lymphatics, liver, and spleen. The associated disease state is known as talaromycosis.
61. CDC/Ajello. Image #11967. This 1971 photograph depicts the reverse view of a Petri dish in which a colony of Penicillium marneffei [now known as Talaromyces marneffei] had been cultivated. Note the darkened interior pigment that lightens to a red-orange, then to a cream coloration, as the colony radiates outward from the center. PHIL public domain. Created 1971. Accessed January 17, 2023. https://phil.cdc.gov/Details.aspx?pid=11967 62. CDC/Ajello. Image #4240. This photomicrograph revealed some of the ultrastructural morphology exhibited by the mold, Talaromyces marneffei, formerly known as Penicillium marneffei, including chains of single-celled, teardrop-shaped conidia, each emanating from its respective, flask-shaped phialide. T marneffei is known to cause a disease known as talaromycosis, formerly referred to as penicilliosis. PHIL public domain. Created 1972. Accessed January 17, 2023. https://phil.cdc.gov/Details.aspx?pid=4240
