Ziehl–Neelsen stain

Acid-fast stain, first introduced by Dr. Paul Ehrlich, also known as the Ziehl–Neelsen staining, is a bacteriological stain used to identify acid-fast organisms, mainly Mycobacteria. It is named for two German doctors who modified it: the bacteriologist Franz Ziehl (1859–1926) and the pathologist Friedrich Neelsen (1854–1898). Acid-fast stain, first introduced by Dr. Paul Ehrlich, also known as the Ziehl–Neelsen staining, is a bacteriological stain used to identify acid-fast organisms, mainly Mycobacteria. It is named for two German doctors who modified it: the bacteriologist Franz Ziehl (1859–1926) and the pathologist Friedrich Neelsen (1854–1898). Mycobacterium tuberculosis is the most important of this group because it is responsible for tuberculosis (TB). Other important Mycobacterium species involved in human disease are Mycobacterium leprae, Mycobacterium kansasii, Mycobacterium marinum, Mycobacterium bovis, Mycobacterium africanum and members of the Mycobacterium avium complex. Acid-fast organisms like Mycobacterium contain large amounts of lipid substances within their cell walls called mycolic acids. These acids resist staining by ordinary methods such as a Gram stain. It can also be used to stain a few other bacteria, such as Nocardia. The reagents used for Ziehl–Neelsen staining are – carbol fuchsin, acid alcohol, and methylene blue. Acid-fast bacilli are bright red after staining. A variation on this staining method is used in mycology to differentially stain acid-fast incrustations in the cuticular hyphae of certain species of fungi in the genus Russula. It is also useful in the identification of some protozoa, namely Cryptosporidium and Isospora. The Ziehl–Neelsen stain can also hinder diagnosis in the case of paragonimiasis because the eggs in sputum sample for ovum and parasite (O&P) can be dissolved by the stain, and is often used in this clinical setting because signs and symptoms of paragonimiasis closely resemble those of TB.