Fungi

Fungal infections

Ecology

• Contaminant
• Commensal
• Colonization
• Infection without damage
• Disease with damage

Clinical Categories

• Yeasts (single-cell)
  • Candida
  • Cryptococcus
• Molds (multi-cellular)
  • Hyalohyphomycosis (hyaline molds)
  • Phaeohyphomycosis (dematiaceous or pigmented)
  • Mucormycosis
  • Dermatophyte (also hyaline)
• Thermally dimorphic fungi (yeast at 37°C, molds below 37°C)
  • Histoplasmosis
    • Great Lakes region and Ohio River Valley
    • Very small cells
  • Blastomycosis
    • Especially prevalent in Ontario
  • Coccidiomycosis
    • South-western US (Arizona and Nevada)
    • Larger cells
• Pneumocystis
• Unusual fungi or fungal-like organisms

Identification of Molds

• Macroscopic
  • Colony appearance
  • Growth rate
• Microscopic
  • Hyphae
  • Sexual reproduction (rarely)
  • Asexual reproduction
    • Blastic conidia: conidia created by budding
      • Blastoconidia: created by budding from the apex or side of a conidiophore. May be solitary, in chains, sympodial (like alternating leaves), or multiseptate.
      • Annelloconidia: with rings on an annellide.
      • Phialoconidia: with a collarette on a bottle-shaped phialide, conidia releated from collaratte.
    • Thallic conidia: conidia created from existing hyphal segments
      • Arthroconidia: may be simple or alternate (with disjunctor cells).
      • Aleurioconidia: may have macroconidia or microconidia.
      • Chlamydospores

Identification of Yeasts

• Macroscopic
  • Colony appearance
• Microscopic
  • Budding cells: may be unipolar or (rarely) bipolar, or (rarely) division by fission
  • Filamentation, including pseudohyphae and true hyphae (which includes germination tubes)
  • Conidium or chlamydospore production
• Physiological tests, including chromagar Candida medium
• Molecular tests

Further Reading

• Anaissie Clinical Mycology 2e