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Ziehl–Neelsen stain (classic and modified bleach types) [5]; Kinyoun stain; For color blind people (or in backgrounds where detecting red bacteria is difficult), Victoria blue can be substituted for carbol fuchsin and picric acid can be used as the counter stain instead of methylene blue, and the rest of the Kinyoun technique can be used.
Mechanism of acid-fast staining in acid-fast cells and non-acid-fast cell [24] [25] [26] The mechanism of action of the Ziehl-Neelsen stain is not completely understood, but it is thought to involve a chemical reaction between the acidic dyes and the cell walls of the bacteria.
The Kinyoun method can be modified as a weak acid fast stain, which uses 0.5–1.0% sulfuric acid instead of hydrochloric acid.The weak acid fast stain, in addition to staining Mycobacteria, will also stain organisms that are not able to maintain the carbol fuchsin after decolorizing with HCl, such as Nocardia species and Cryptosporidium.
Some bacteria have cell walls which are particularly adept at retaining stains. These will appear positive by Gram stain even though they are not closely related to other gram-positive bacteria. These are called acid-fast bacteria, and can only be differentiated from other gram-positive bacteria by special staining procedures. [25]
[2] [3] Carbol fuchsin is used as the primary stain dye to detect acid-fast bacteria because it is more soluble in the cells' wall lipids than in the acid alcohol. If the bacteria is acid-fast the bacteria will retain the initial red color of the dye because they are able to resist the destaining by acid alcohol (0.4–1% HCl in 70% EtOH). [4 ...
Acid fast (Ziehl-Neelsen technique) Film stained with hot Z.N.C.F. decolourised (acid-alcohol) and counter stain with methylene blue Separate non-decolorized acid fast bacteria that are not decolorized from colorized non-acid fast bacteria Acid fast bacteria:Red Non acid fast: Blue 5 Endospore (Dornor's method)
In the Runyon classification, both bacteria are nonchromogens. They can be differentiated from M. tuberculosis and each other by commercially available DNA probes. [4]: 245 They are characterized as Gram-positive, nonmotile, acid-fast, short to long rods. [citation needed] Colony characteristics
In solution with phenol (also called carbolic acid) as an accentuator [16] it is called carbol fuchsin and is used for the Ziehl–Neelsen and other similar acid-fast staining of the mycobacteria which cause tuberculosis, leprosy etc. [17] Basic fuchsine is widely used in biology to stain the nucleus, and is also a component of Lactofuchsin ...