Ziehl-Neelsen carbol fuchsin, also known as hot staining, is a staining method specifically designed to identify acid-fast bacteria such as Mycobacterium tuberculosis. The method is based on the use of carbolfuchsin as the primary dye and the application of heat to enhance the penetration of the dye into the cells.

In Ziehl-Neelsen hot staining, the tissue sample is first treated with the carbolfuchsin solution. Carbolfuchsin is a red dye used in combination with phenol and alcohol to allow good penetration into the cells. After application of the carbol fuchsin, the sample is briefly heated to increase the depth of penetration of the dye and improve binding to the acid-fast bacteria.

After heating, the sample is cooled and then treated with an acid decolorizing solution to decolorize non-acid-fast cells and structures. Acid-fast bacteria retain the carbolfuchsin dye and appear bright red in color, while other cell structures lose color.

Ziehl-Neelsen hot staining is an important technique in the diagnosis of tuberculosis and other infections with acid-fast bacteria. It allows the specific visualization of these bacteria in tissue samples and facilitates the identification and differentiation of mycobacteria and other cell structures.