Grocott staining is particularly useful for visualizing Pneumocystis jiroveci.

• A. Pneumocystis jiroveci
• B. Candida albicans
• C. Mycobacterium tuberculosis
• D. Plasmodium falciparum

Answer: (A)

Grocott staining uses silver to highlight fungal cell walls, creating a dark, contrasting image against a lighter background. This makes fungi much easier to see in tissue sections. Pneumocystis jiroveci has small cysts in lung tissue that can be very difficult to spot with routine stains, but the Grocott methenamine silver stain binds strongly to their cell walls, turning these cysts black and clearly revealing them. Because of this high contrast and specificity for fungal walls, this stain is especially valuable for detecting Pneumocystis pneumonia.

Candida albicans can also be seen with this stain, but it isn’t the hallmark use; in many cases other stains or routine methods suffice to visualize Candida. Mycobacterium tuberculosis is best seen with acid-fast stains, not Grocott. Plasmodium falciparum is identified primarily in blood smears using Giemsa or Wright stains, not this silver method.