Which of the following stains is used to demonstrate yeast forms of cryptococci in tissue sections
**Core Concept**
The diagnosis of fungal infections, particularly cryptococcosis, relies on the demonstration of fungal elements in tissue sections. This requires the use of specific histological stains that can highlight the morphological features of the fungi, such as yeast forms.
**Why the Correct Answer is Right**
Mucicarmine stain is a polychrome stain that is commonly used to demonstrate the capsule of Cryptococcus neoformans in tissue sections. The capsule is a thick, polysaccharide-rich structure that surrounds the yeast cell wall and is a hallmark of this pathogen. The mucicarmine stain reacts with the capsular polysaccharides, resulting in a pink or red coloration that is easily visible under the microscope. This allows for the identification of yeast forms of cryptococci in tissue sections.
**Why Each Wrong Option is Incorrect**
**Option A:** Gomori methenamine silver (GMS) stain is used to demonstrate fungal elements, but it is not specific for Cryptococcus neoformans or its yeast forms. It stains a wide variety of fungi, including Aspergillus and Candida species.
**Option B:** Periodic acid-Schiff (PAS) stain is a general-purpose stain that can be used to detect fungal elements, but it is not as specific as mucicarmine stain for Cryptococcus neoformans.
**Option C:** Grocott's methenamine silver (GMS) stain is another type of silver stain that is used to demonstrate fungal elements, but it is not specific for Cryptococcus neoformans.
**Clinical Pearl / High-Yield Fact**
Mucicarmine stain is a key diagnostic tool for cryptococcosis, particularly in the context of immunocompromised patients. It is essential to consider this stain in the differential diagnosis of fungal infections, especially when Cryptococcus neoformans is suspected.
**Correct Answer: B. Periodic acid-Schiff (PAS) stain is used to demonstrate yeast forms of cryptococci in tissue sections.**