acidfastvärjäyksellä

Acid-fast staining is a differential staining technique used in microbiology to identify bacteria that have a waxy cell wall, specifically those containing mycolic acids. These acids make the cell wall resistant to decolorization by acids and alcohol after being stained with a primary dye. The most common application of acid-fast staining is for the identification of *Mycobacterium* species, including *Mycobacterium tuberculosis*, the causative agent of tuberculosis.

The procedure typically involves applying a primary stain, usually carbolfuchsin, which is a bright red dye. This stain is then heated to allow it to penetrate the waxy cell wall. After cooling, a decolorizing agent, typically an acid-alcohol solution, is applied. Acid-fast bacteria retain the red carbolfuchsin stain because their mycolic acid content prevents the decolorizer from removing the dye. Non-acid-fast bacteria, which lack this waxy layer, will be decolorized by the acid-alcohol. A counterstain, such as methylene blue or malachite green, is then applied to stain the decolorized non-acid-fast bacteria, making them visible under a microscope. Acid-fast bacteria appear as red or pink rods, while non-acid-fast bacteria appear as blue or green rods. This staining method is crucial for diagnosing mycobacterial infections and for differentiating these bacteria from other types.