Closing the Brief Case: Pneumonia Caused by Talaromyces marneffei

ANSWERS TO SELF-ASSESSMENT QUESTIONS

1. T. marneffei infection occurs primarily in individuals who:

   • a.
     Are HIV infected and reside in or have traveled to an area of endemicity
   • b.
     Are elderly
   • c.
     Are women of childbearing age
   • d.
     Have chronic lung disease

Answer: a. T. marneffei infection is most common in HIV/AIDS patients who reside in or who have traveled to regions where the fungus is endemic, such as southern China, Taiwan, Hong Kong, and other parts of southeast Asia. While rare, T. marneffei infection has also been reported in individuals with other immunosuppressive conditions, including subjects who have received solid organ transplants.

1. Which morphological form would be observed for suspected T. marneffei isolates when cultured at 37°C?

   • a.
     Budding spherical to ellipsoidal yeast-like cells
   • b.
     A filamentous fungus with a diffusible red pigment
   • c.
     Spherical to ellipsoidal yeast-like cells with a central septum
   • d.
     Spherical to ellipsoidal yeast-like cells with a diffusible red pigment

Answer: c. T. marneffei forms ellipsoidal yeast-like cells with a central septum at 37°C. T. marneffei reproduces by binary fission rather than budding, and therefore budding yeast cells are not observed in T. marneffei infections. At temperatures between 25 and 30°C, T. marneffei grows as a filamentous fungus and a diffusible red-brown pigment can be observed in maturing colonies.

1. Which antifungal drug would be the least effective for the treatment of talaromycosis?

   • a.
     Amphotericin B
   • b.
     Fluconazole
   • c.
     Voriconazole
   • d.
     5-Flucytosine

Answer: b. Amphotericin B and intraconazole have been shown to be effective clinically as treatment. T. marneffei has been shown to have elevated fluconazole MIC values in vitro, and the clinical response to fluconazole treatment is poor. T. marneffei generally has low MIC values for other azoles and 5-flucytosine.

TAKE-HOME POINTS

• Talaromyces marneffei, previously named Penicillium marneffei, causes talaromycosis, a lethal, systemic infection characterized by fungal invasion of multiple organ systems, including the lungs, blood, skin, and bone marrow.

• Talaromyces marneffei infection is a significant cause of morbidity and mortality among those with HIV/AIDs and other immunosuppressive conditions who reside in, or travel to, regions of endemicity, namely, Southeast Asia and southern China. Clinicians should always gather a complete travel history to ensure no delays in diagnosis or treatment occur.

• To reduce mortality, early treatment for talaromycosis is essential. Amphotericin B and itraconazole are recommended for the treatment of T. marneffei infection. No antifungal susceptibility testing interpretative criteria exist for T. marneffei.

• Talaromyces marneffei shows temperature-dependent dimorphic growth. When cultured at 37°C, T. marneffei grows as spherical to ellipsoidal yeast-like cells with a central septum and at temperatures between 25 and 30°C, T. marneffei grows as a filamentous fungus with a diffusible red-brown pigment.

See https://doi.org/10.1128/JCM.01690-18 in this issue for case presentation and discussion.