Cryptococcus

Paul G. Auwaerter, M.D., John G. Bartlett, M.D.
Cryptococcus is a topic covered in the Johns Hopkins ABX Guide.

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MICROBIOLOGY

  • Yeast-like, round fungus; usual size is 5-10µm with polysaccharide capsule [Fig].
    • Reproduces by narrow-based budding.
  • Epidemiology: worldwide in soil, high levels in pigeon droppings (but this relevance is questionable for human disease).
  • Two species:
    • C. neoformans historically divided into 4 serotypes (A to D) described based upon the capsule components with 2 species and 2 varieties causing human disease. Now based on genotypic evaluation, proposed:
      • Serotype A: now known as C. neoformans v. grubii
      • Serotypes B and C: C. gattii
      • Serotype D: C. neoformans v. neoformans (most common) and worldwide in distribution
    • C. gattii: more recently detected and seen primarily in Australia, Western Canada and northwestern U.S. (Washington and Oregon).
      • Clinical presentation and diagnosis and treatment are the same as with C. neoformans.
      • Differences from C. neoformans include higher attack rates in healthy hosts, and worse prognosis.
      • Appears more resistant to fluconazole.
      • True extent of infection/epidemiology not known.

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MICROBIOLOGY

  • Yeast-like, round fungus; usual size is 5-10µm with polysaccharide capsule [Fig].
    • Reproduces by narrow-based budding.
  • Epidemiology: worldwide in soil, high levels in pigeon droppings (but this relevance is questionable for human disease).
  • Two species:
    • C. neoformans historically divided into 4 serotypes (A to D) described based upon the capsule components with 2 species and 2 varieties causing human disease. Now based on genotypic evaluation, proposed:
      • Serotype A: now known as C. neoformans v. grubii
      • Serotypes B and C: C. gattii
      • Serotype D: C. neoformans v. neoformans (most common) and worldwide in distribution
    • C. gattii: more recently detected and seen primarily in Australia, Western Canada and northwestern U.S. (Washington and Oregon).
      • Clinical presentation and diagnosis and treatment are the same as with C. neoformans.
      • Differences from C. neoformans include higher attack rates in healthy hosts, and worse prognosis.
      • Appears more resistant to fluconazole.
      • True extent of infection/epidemiology not known.

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