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Leveduras e fungos

Cryptococcus neoformans

Encapsulated yeasts

Identification & Growth

Identification

  • India ink stain: capsular halo visible in CSF
  • Urease-positive, phenoloxidase-positive (Niger seed/birdseed agar: brown colony)
  • Cryptococcal antigen (latex/LFA) in CSF and serum

Growth Conditions

  • Sabouraud agar without cycloheximide, 30–35 °C, 48–72 h; mucoid, creamy colonies

Clinical Significance

  • Meningitis in people living with HIV and other immunosuppressed patients; pulmonary cryptococcoma

Intrinsic Resistance

  • Echinocandins have no activity — never use caspofungin

Bench Alerts

  • Never report an echinocandin as an option
  • Treatment is amphotericin B plus flucytosine, followed by fluconazole
  • CSF opening pressure measurement is part of management

Clinical Notes

Clinical presentations

  • Causes subacute to chronic meningoencephalitis, particularly in patients with advanced HIV infection and other cellular immunosuppression states.
  • Pulmonary cryptococcal disease ranges from asymptomatic nodules to severe pneumonia, potentially preceding dissemination to the central nervous system.
  • Can cause skin lesions and disseminated infection in immunocompromised patients, including solid organ transplant recipients.

Specimens and collection

  • Cerebrospinal fluid should be collected with opening pressure measurement, essential for managing intracranial hypertension.
  • Cryptococcal antigen (CrAg) testing in serum or CSF is highly sensitive and specific, recommended for rapid screening and diagnosis.
  • Fungal culture of CSF and blood should be performed for diagnostic confirmation and monitoring of therapeutic response.

Epidemiology and at-risk populations

  • Is the leading cause of fungal meningitis in patients with advanced HIV/AIDS, especially with CD4 counts below 100 cells/µL.
  • Environmental exposure occurs via inhalation of spores present in soil contaminated by bird droppings, especially pigeons.
  • Global disease burden is significant in regions with high HIV prevalence and limited access to antiretroviral therapy.

Resistance and therapeutic implications

  • Liposomal amphotericin B combined with flucytosine is the recommended induction therapy for cryptococcal meningitis.
  • Adequate-dose fluconazol is used in the consolidation and maintenance phases following successful induction.
  • Primary antifungal resistance is rare, but susceptibility testing may be considered in treatment failure or relapse.

Bench and reporting notes

  • India ink staining of CSF reveals encapsulated yeasts, though with lower sensitivity than antigen testing.
  • Growth on Sabouraud agar with characteristic mucoid colonies confirms identification after 48-72 hours of incubation.
  • Serial CSF opening pressure measurement is essential to guide relief taps in clinical management.

Sources

Educational decision-support content. It does not replace laboratory validation, current guidelines or review by the responsible professional.

FAQ: Frequently Asked Questions

How to identify Cryptococcus neoformans in the lab?

Cryptococcus neoformans is identified through india ink stain: capsular halo visible in csf, urease-positive, phenoloxidase-positive (niger seed/birdseed agar: brown colony), cryptococcal antigen (latex/lfa) in csf and serum.

What are the intrinsic resistances of Cryptococcus neoformans?

This organism is naturally resistant to echinocandins have no activity — never use caspofungin. These drugs should not be reported as susceptible.

Where is Cryptococcus neoformans commonly found?

It is typically associated with meningitis in people living with hiv and other immunosuppressed patients; pulmonary cryptococcoma.

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