Which stain is used for identifying fungi and its constituents?

Grocott's methenamine silver (GMS) stain is specifically designed for identifying fungi and certain fungal components in histopathologic examinations. This stain selectively binds to polysaccharides in the cell wall of fungi, highlighting them with a characteristic black or dark green color against a green or pale yellow background. GMS is particularly useful for visualizing organisms such as Aspergillus and Candida, making it a vital tool in diagnosing fungal infections in tissue samples.

The other stains listed have different purposes. Wright-Giemsa stain is commonly used for the identification of blood cells and pathogens in blood smears. Cresyl fast violet is primarily used to stain nervous tissue and detect neuronal cell bodies. The peroxidase reaction is a histological technique used for identifying enzyme activity, particularly in the context of immunohistochemistry, rather than for staining fungi directly. Therefore, the GMS stain stands out as the most appropriate choice for fungal identification in tissue samples.