Capsule Stains

Capsule Stains are differential stains used to view bacteria that can produce an outer polysaccharide/polypeptide capsule which functions for protection and increased virulence since the capsule protects the bacteria from phagocytosis. Both acidic and basic dyes are used on non-heat fixed smears. The basic dye such as Crystal Violet, will stain the bacteria, while the acidic dye, such as India Ink, provides a colored contrasting background.

The capsule appears as a clear-white halo area around the bacteria.

Black backgound is colored by the acidic dye, the bacteria is purple from CV.