Microbiology · India ink wet mount

Cryptococcus neoformans (India Ink Preparation)

Round yeast cells surrounded by a wide clear halo against a dark background — the capsule of Cryptococcus neoformans in an India ink preparation.

Micrograph of many round yeast cells each surrounded by a thick clear halo on a brownish background
Cryptococcus neoformans in a light India ink preparation (CDC PHIL #3771).Image: CDC / Dr. Leanor Haley, via Wikimedia Commons — Public domain.

Written & reviewed by: Kinase Medical Team · Last reviewed: 30 September 2026 · Editorial policy

Key features

  • The polysaccharide capsule excludes ink particles, leaving a clear halo around each yeast cell.
  • A quick wet-mount test on CSF, but it can be negative when the fungal burden is low.
  • Culture is the gold standard; cryptococcal antigen detection in CSF, serum or plasma gives rapid results.
  • Most infections are in immunocompromised people, especially advanced HIV disease; CSF shows chronic meningitis (mononuclear pleocytosis, raised protein).
  • C. neoformans lives in soil and bird droppings; C. gattii is mostly tropical/subtropical.
  • Severe CNS disease: amphotericin B + flucytosine, then prolonged fluconazole.

Differential diagnosis

Differential diagnosis of Cryptococcus neoformans (India Ink Preparation)
ConditionHow to tell it apart
Leukocytes or fat globules in CSFCan be mistaken for yeast by inexperienced readers — confirm with antigen testing or culture.

How it appears in NEET PG

Shown as an India ink or nigrosin image with an HIV patient and chronic headache; questions ask for the organism, the virulence factor (capsule) or induction therapy.

Frequently asked questions

Why does Cryptococcus show a halo on India ink?

Its thick polysaccharide capsule keeps out the ink particles, so a clear zone appears around each yeast against the dark background.

What is the gold standard for diagnosing cryptococcosis?

Culture. Cryptococcal antigen testing in CSF or blood is used for rapid diagnosis; India ink is quick but less sensitive.

How is cryptococcal meningitis treated?

Induction with amphotericin B plus flucytosine, followed by long-term fluconazole.

Sources

  1. CDC — Clinical overview of cryptococcosis
  2. Harrison's Principles of Internal Medicine (textbook)

Keep practising

For exam preparation and medical education only — not a substitute for clinical judgement, diagnosis or treatment of any patient.