Which organism characteristic is visualized by India ink staining in cryptococcosis?

Which organism characteristic is visualized by India ink staining in cryptococcosis?

• A. Encapsulated, budding yeast
• B. Gram-positive cocci in clusters
• C. Branching hyphae
• D. Acid-fast bacilli

Answer: (A)

India ink staining in cryptococcosis highlights encapsulation. Cryptococcus neoformans has a thick polysaccharide capsule that rejects the ink, so under a negative-stain prep the yeast appears with a clear halo around it against a dark background. This capsule is a defining feature and, together with budding yeast forms, is what you’re visualizing with India ink. Other organisms wouldn’t show this encapsulated appearance with India ink: Gram-positive cocci in clusters would be seen as purple cocci on Gram stain, branching hyphae point to molds like Aspergillus or Candida in its hyphal form, and acid-fast bacilli require different staining (acid-fast) to be seen. The key takeaway is that the clear halo around a budding yeast signal encapsulation, characteristic of Cryptococcus.

India ink staining in cryptococcosis highlights encapsulation. Cryptococcus neoformans has a thick polysaccharide capsule that rejects the ink, so under a negative-stain prep the yeast appears with a clear halo around it against a dark background. This capsule is a defining feature and, together with budding yeast forms, is what you’re visualizing with India ink.

Other organisms wouldn’t show this encapsulated appearance with India ink: Gram-positive cocci in clusters would be seen as purple cocci on Gram stain, branching hyphae point to molds like Aspergillus or Candida in its hyphal form, and acid-fast bacilli require different staining (acid-fast) to be seen. The key takeaway is that the clear halo around a budding yeast signal encapsulation, characteristic of Cryptococcus.