Acid Fast Stain- Principle, Reagents, Procedure and Result Interpretation


Ziehl-Neelsen stain, also known as acid-fast stain, is a special staining technique that was developed in the late 19th century by two German microbiologists, Franz Ziehl and Friedrich Neelsen. It is used to identify bacteria that belong to the genus Mycobacterium, which includes the causative agents of tuberculosis, leprosy and other diseases. These bacteria are called acid-fast because they retain the primary stain even after being treated with acid alcohol, unlike most other bacteria that are easily decolorized. This property is due to the presence of a thick and waxy layer of mycolic acid in their cell wall, which makes them resistant to many conventional staining methods and antimicrobial agents.