How to Identify Penicillium Marneffei

Penicillium marneffei is a fungus carried by the bamboo rat located in Southeast Asia. Mild infections are common in this region and persons who have traveled into Southeast Asia may be at risk of contracting this infection -- though the method of transmission is still unknown. In recent years, doctors in the United States, Europe and the rest of the world have found it necessary to become familiar with methods of identifying a Penicillium marneffei infection, because persons with HIV and AIDS are particularly susceptible to this opportunistic infection.

Things You'll Need

• Microscope
• Skin biopsy
• Bone marrow aspirate
• Giemsa stain
• Sabouraud's dextrose agar
• Brain heart infusion (BHI) blood

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Instructions

• 1

  Take a patient history. According to the Centers for Disease Control, patients who present with possible Penicillium marneffei recently traveled to Thailand, Myanmar (Burma), Vietnam, Cambodia, Malaysia, northeastern India, Hong Kong, Taiwan and southern China -- or came into contact with persons who recently traveled in these areas. In addition, these patients typically have an advanced HIV infection, AIDS or another condition that severely compromises their immune system.

• 2

  Examine the skin of the infected person. Penicillium marneffei infections present as nodules on the face, trunk and extremities. In advanced infections, the nodules will show necrotic umbililication, a centralized depression representing an area of dying tissue.

• 3

  Identify possible Penicillium marneffei infection by microscopy. Either a skin biopsy or bone marrow aspiration touch smear stained with Giemsa will clearly show the presences of Penicillium marneffei. Under a microscope, the fungus will appear in elliptical yeast form 2 to 6 micrometers in length. Replicating yeast will show a clear septum or divide, distinguishing them from other yeast that replicate by budding.

• 4

  Perform two cultures of the skin or bone marrow samples. Pencillium marneffei is thermally dimorphic, growing as a filamentous fungus at low temperatures and as a yeast at body temperature. A culture grown on Sabouraud's dextrose agar at 27 degrees Celsius will produce a yellow-pink filamentous fungus that eventually produces a orange or red stain in the surrounding agar. A culture grown on brain heart infusion (BHI) blood agar at 35 degrees Celsius, encourages the growth of the yeast producing a smooth, creamy to slightly pink colony.