Fungal Infections

Species/common name:

 Talaromyces marneffei ( formerly Penicillium marneffei)

Natural habitat

Not known with confidence. Cultures have usually been positive from bamboo rats (4 different species) and humans, and rarely from environmental sources. However, epidemiological studies suggest environmental acquisition.

Geography

Southeast Asia, notably Thailand, Vietnam, Hong Kong, southern China, Taiwan, India, Indonesia, Cambodia and Laos. May be acquired in these localities and present with disease anywhere in the world.

Frequency

Uncommon, except in these locations, in which areas it is a common AIDS-defining illness. Increased incidence during the rainy season in Thailand.

Diseases

Disseminated infection in context of AIDS with prominent skin lesions

Pneumonia in other immunocompromised individuals.

Culture peculiarities

Talaromyces marneffei is the only dimorphic fungus in the genus. It grows rapidly on Sabouraud dextrose agar but is inhibited by cycloheximide. At 25°C, the colonies of Talaromyces marneffei are granular with shade of greenish-yellow colour and a characteristic red diffusible pigment. Little or no red diffusible pigment is produced by the yeast form at 35 to 37°C. Microscopically, the mold form is typical of other Taoaromyces species with hyaline septated hyphae and fruiting structures composing of branching metulae and phialides which produce spherical conidia in chains. As several species of Talaromyces penicillium produce red diffusible pigment, definitive identification by sequencing is desirable in countries in which this organism is not common.

Antifungal resistance (intrinsic and acquired)

All isolates are susceptible to 5-flucytosine miconazole, ketoconazole, itraconazole, voriconazole and amphotericin B.  Fluconazole is relatively inactive.  

Biosafety level

This organism must be handled in a biosafety level 3 laboratory.

Industrial use

While many Talaromyces species have major industrial utility (cheese-making in particular), Talaromyces marneffei has none.

 

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