Which staining technique is used to identify acid-fast bacteria such as Mycobacterium tuberculosis?

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Multiple Choice

Which staining technique is used to identify acid-fast bacteria such as Mycobacterium tuberculosis?

Ziehl-Neelsen staining is the method used to identify acid-fast bacteria. It relies on the waxy, lipid-rich cell wall of organisms like Mycobacterium tuberculosis, which resists decolorization by acid alcohol. The procedure uses a strong red primary stain (carbol fuchsin) with heating to drive the stain into the cell wall, followed by an acid-alcohol decolorizer; acid-fast bacteria retain the red color, while non-acid-fast cells are decolorized and then counterstained to provide contrast. This makes TB bacteria stand out clearly in sputum or other samples. Gram staining is not reliable for these organisms because their lipid-rich walls can confuse Gram results. Giemsa and Wright stains are used for other purposes (blood smears and parasites) and do not specifically identify acid-fast bacteria.

Ziehl-Neelsen staining is the method used to identify acid-fast bacteria. It relies on the waxy, lipid-rich cell wall of organisms like Mycobacterium tuberculosis, which resists decolorization by acid alcohol. The procedure uses a strong red primary stain (carbol fuchsin) with heating to drive the stain into the cell wall, followed by an acid-alcohol decolorizer; acid-fast bacteria retain the red color, while non-acid-fast cells are decolorized and then counterstained to provide contrast. This makes TB bacteria stand out clearly in sputum or other samples.

Gram staining is not reliable for these organisms because their lipid-rich walls can confuse Gram results. Giemsa and Wright stains are used for other purposes (blood smears and parasites) and do not specifically identify acid-fast bacteria.

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