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Cryptococcus neoformans

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Summary

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Key Points

  • Cryptococcus neoformans
    • Characteristics
      • Narrow oval budding yeast
        • Not dimorphic; no mold form
        • Does not form hyphae or pseudohyphae
      • Thick polysaccharide capsule
        • Highlighted with
          • India ink stain (clear halo)
          • mucicarmine (red inner capsule)
      • Makes melanin
    • Transmission
      • Opportunistic
        • Infects immunocompromised individuals (esp. HIV/AIDS)
      • Found in soil via bird (pigeon) droppings
      • Yeast is inhaled into lungs
        • Hematogenous dissemination to meninges
    • Presentation: Cryptococcosis
      • Meningoencephalitis
        • “Soap bubble” lesion in brain
        • Present with fevers, relentless headaches, and generalized malaise
    • Diagnosis
      • CSF with wide halos on India ink stain
      • Latex agglutination test
        • Detects polysaccharide capsular antigen in CSF
        • Sensitive and specific; but has been largely replaced with lateral flow assays which are faster with same diagnostic accuracy
    • Treatment
      • Amphotericin B and  flucytosine, followed by fluconazole