The Ziehl–Neelsen stain, also known as the acid-fast stain, was first described by two German doctors; Franz Ziehl (1859 to 1926), a bacteriologist and Friedrich Neelsen (1854 to 1898), a pathologist. It is a special bacteriological stain used to identify acid-fast organisms, mainly Mycobacteria. Mycobacterium tuberculosis is the most important of this group, as it is responsible for the disease called tuberculosis (TB). Other important Mycobacterium species involved in human disease are Mycobacterium Kansasii, Mycobacterium Marinum, 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 like a Gram stain[1]. It can also be used to stain a few other bacteria like Nocardia. The reagents used are Ziehl–Neelsen carbolfuchsin, acid alcohol and methylene blue. Acid-fast bacilli will be 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.[2][3]
[edit] Procedure
- Prepare smear.
- Air dry and heat fix it
- Rinse in carbol fuchsin
- Light a cotton swab and hold it underneath until steam appears
- Wash with dilute hydrochloric acid until a faint pink color remains.
- Counterstain with Methylene Blue for a minute
- Wash with gentle water till violet becomes faint
- Blot dry
- View under oil immersion lens
Studies have shown that an AFB stain without a culture has a poor negative predictive value. An AFB Culture should be performed along with an AFB stain; this has a much higher negative predictive value.
[edit] Modifications
- 5% sulfuric acid is used for destaining Mycobacterium leprae instead of the 20% used for Mycobacterium tuberculosis.
- Kinyoun modification (or cold Ziehl–Neelsen technique) is also available.
- A protocol in which a detergent is substituted for the highly toxic phenol in the fuchsin staining solution.[4]
[edit] See also
[edit] References
- "Microbiology with Diseases by Body System", Robert W. Bauman, 2009, Pearson Education, Inc.
- Morello, Josephine A., Paul A. Granato, Marion E. Wilson, and Verna Morton. Laboratory Manual and Workbook in Microbiology: Applications to Patient Car. 10th ed. Boston: McGraw-Hill Higher Education, 2006. Print.
[edit] Online protocol examples
[edit] References
[edit] External links
Media related to Ziehl-Neelsen stain at Wikimedia Commons
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