CarbolfuchsinLösung

Carbolfuchsin Lösung, also known as Carbolfuchsin solution, is a staining solution commonly used in microscopy, particularly in the Ziehl-Neelsen staining method and its modifications. It is an aqueous or alcoholic solution of basic fuchsin, a dye that stains acidic structures within cells. The key characteristic of carbolfuchsin is its strong affinity for the waxy cell walls of certain bacteria, most notably Mycobacterium species, which are the causative agents of tuberculosis and leprosy.

The composition of carbolfuchsin solution typically includes basic fuchsin, phenol, and either ethanol or isopropanol. Phenol is a crucial component as it helps to penetrate the lipid-rich cell walls of mycobacteria. The alcohol acts as a solvent for the dye and phenol, and also plays a role in decolorization steps during staining. When applied to a specimen, carbolfuchsin stains these bacteria a distinct red or pink color. This red color is retained even after treatment with a decolorizing agent, such as acid-alcohol, which removes the stain from other, less resistant cells and tissues.

In the Ziehl-Neelsen stain, carbolfuchsin solution is heated to aid penetration into the bacterial cells. After decolorization, a counterstain, usually a blue dye like methylene blue or brilliant green, is applied to stain the background and other cellular elements. This differential staining allows for the identification of acid-fast bacilli under a microscope, making carbolfuchsin a vital reagent in diagnostic microbiology and research. Variants of the staining method, such as Kinyoun staining, use a higher concentration of phenol and omit the heating step, relying solely on the concentrated phenol for penetration.