Gram staining: principle and interpretation

Microbiology Notes · 4 min read · Preview summary, not a migrated article

Overview

Gram staining is a differential stain used to distinguish many bacteria by their cell-wall characteristics. The procedure uses a primary stain, a mordant, a decolorizer and a counterstain.

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Key principles

Gram-positive cells typically retain the crystal violet–iodine complex and appear purple. Gram-negative cells are decolorized and take up the counterstain, appearing pink. Culture age, smear thickness and decolorization affect results. A Gram reaction alone is not a species identification.

Gram staining: principle and interpretation

Overview

Key principles

Further reading

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