Cryptococcus can be readily demonstrated by
**Core Concept**
Cryptococcus is a type of encapsulated yeast that can cause opportunistic infections, particularly in immunocompromised patients. The organism's capsule is a key virulence factor, allowing it to evade phagocytosis and cause disease.
**Why the Correct Answer is Right**
The capsule of Cryptococcus is composed of polysaccharides, primarily glucuronoxylomannan (GXM). This capsule can be readily demonstrated using India ink staining, which takes advantage of the hydrophobic nature of the capsule. The ink fails to penetrate the capsule, creating a clear halo around the organism, making it visible against a dark background. This technique is a classic diagnostic tool for identifying Cryptococcus neoformans in clinical specimens.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify a method for demonstrating Cryptococcus. While other staining techniques may be used, India ink staining is the most characteristic method for visualizing the capsule.
**Option B:** This option is incorrect because it is a general statement about fungal identification, rather than a specific method for demonstrating Cryptococcus.
**Option C:** This option is incorrect because it is a type of staining used for bacteria, not fungi.
**Clinical Pearl / High-Yield Fact**
India ink staining is a classic diagnostic tool for Cryptococcus, but it should not be used to diagnose other types of fungal infections. Always consider the clinical context and specific features of the organism when selecting a diagnostic technique.
**Correct Answer: D. India ink staining.**