Acid Fast Stains,Etiology of Tuberculosis,Alcohol,Decolorizer,Aqueous Phenol,Mycobacteria,Nocardia,Bacteria

Acid Fast Stains

Acid Fast Stains
Acid fast staining is another widely used differential staining procedure in bacteriology. This stain was developed by Paul Ehrlich in 1882, during his work on etiology of tuberculosis (5). Some bacteria resist decolourization by both acid and alcohol and hence they are referred as acid-fast organisms. Acid alcohol is very intensive decolourizer. This staining technique divides bacteria into two groups (i) acid-fast and (ii) non acid-fast. This procedure is extensively used in the diagnosis of tuberculosis and leprosy.

Acid-fastness property in certain Mycobacteria and some species of Nocardia is correlated with their high lipid content. Due to high lipid content of cell wall, in some cases 60% (w/w), acid-fast cells have relatively low permeability to dye and hence it is difficult to stain them. For the staining of these bacteria, penetration of primary dye is facilitated with the use of 5% aqueous phenol which acts as a chemical intensifier. In addition, heat is also applied which acts as a physical intensifier. Once these cells are stained, it is difficult to decolourize

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Acid Fast Stains