What are the staining characteristics of mycobacteria?

Mycobacteria are aerobic, non–spore-forming, nonmotile bacilli. They do not stain readily, but their most useful staining characteristic is acid fastness. Acid fastness refers to the ability to retain carbol fuchsin dye after washing with acid or alcohol as a result of a high content of cell wall mycolic acids, fatty acids, and other lipids. The acid-fast stain is also called the Ziehl-Neelsen stain. Other staining methods include the Dieterle, Fite, hematoxylin-eosin, auramine-rhodamine, and phenolic acridine orange stains. Acid fastness is also shared by Nocardia, Rhodococcus, Legionella micdadei, Isospora, and Cryptosporidium.