Yeasts/Mold

Question 1

Contrast Molds and yeasts on the basis of their colony appearance and microscopic appearance

Answer 1

• Molds: Colonies appear fuzzy

- Yeasts: Colonies round and smooth, flat colonies

Question 2

Define dimorphic fungi

Answer 2

• Fungus that can grow either as a yeast or a mold. Yeast in host (body temperature), or mold in the lab (room temperature)

Question 3

Fungal cell wall, and membranes, how different than human cells?

Answer 3

• Fungal cell wall is thick! Made of chitin, glucans, and mannoproteins.
• Fungal Membrane: Phospholipid bilayer with Ergosterol (human cholesterol equivalent)in it. Eergosterol is target of some antifungal treatments!

Question 4

Antifungal Therapy Targets

Answer 4

• Cell wall (targets glucan): Echinocandins ex.Caspofungin
• Cell Membrane (Targets Ergosterol): 3 Types: 1. Polyene antibiotics - ex. Amphotericin B. 2. Azoles - ex. Imidazoles or Triazoles. 3. Allyamines - Tirbinafin.
• Nuclear (Targets DNA and RNA): Flucytosine

Question 5

List 4 classes of fungal disease

Answer 5

• Superficial … Dermatophytosis
• Subcutaneous… Candida
• Opportunistic and invasive… In immunosuppressed, ex. Aspergillosis
• Endemic… ex. Malaria

Question 6

List 3 risk factors for invasive fungal infections

Answer 6

• Immunosuppression
• Promotion of fungal colonization with antibiotic use
• Providing access to blood and organs with catheters.

Question 7

Recall methods for diagnosing fungal infections in the lab

Answer 7

• Direct Microscopy of Tissue Sample….Special Stains… Grocott-Gomori Stain (GMS), Hematoxylin and eosin, Mayer’s mucicarmine, Masson-Fontana, Periodic Acid Schiff,
• Culture… much slower process, can take 4-7 weeks!
• Serology… only good for coccidioidomycoses
• Antigen Detection
• Nucleic Acid Testing.. PCR

Question 8

Discuss Aspergillus. Epidemiology, clinical syndromes, diagnosis, and treatment

Answer 8

• Caused by mold
• Spores get breathed in… goes to lung… germinate then spread all throughout body! Really bad infections!
• High rates in Stem cell and organ Transplant patients. Or in immunosuppressed
• Clinical syndromes…3 types: 1. Allergic = longterm , eosinophilic pneumonia. 2. Colonization of hyphae in Xray. 3. Invasive… neutropenia= VERY DANGEROUS!
• Diagnosis: Biopsy, Xray
• Treatment: Voriconazole