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Carbolfuchsin is the ________ in the acid-fast stain.

1) counterstain
2) primary stain
3) mordant
4) decolorizer
5) fixing reagent

1 Answer

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Final answer:

Carbolfuchsin is utilized as the primary stain in the acid-fast staining technique to differentiate bacteria with waxy cell walls.

Step-by-step explanation:

Carbolfuchsin is the primary stain in the acid-fast staining procedure. The acid-fast stain is a differential method that allows microbiologists to distinguish between bacteria with and without waxy mycolic acids in their cell walls. In the Ziehl-Neelsen and Kinyoun methods of acid-fast staining, carbolfuchsin serves as the primary stain because it is the first dye applied to the specimen. This stain penetrates the waxy cell walls of the acid-fast bacteria, which retain the carbolfuchsin even after the application of a decolorizing agent. Consequently, acid-fast bacteria will appear red or pink, contrasting sharply with non-acid-fast cells that are counterstained with methylene blue and appear blue.

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