Question

[CH-07-06] What substances in the wall of acid-fast bacteria account for their staining reaction?

Answer 1

Ans.

Acid-fast organisms are characterized by wax-like, nearly impermeable cell walls containing mycolic acid and large amounts of fatty acids, waxes, and complex lipids. Acid-fast organisms are highly resistant to disinfectants and dry conditions.

As cell wall is resistant to most compounds , acid-fast organisms require a special staining technique.

The primary stain used in acid-fast staining, carbolfuchsin.

• Carbolfuschin is lipid-soluble and contains phenol, which helps the stain penetrate the cell wall. This is then foll8 by the addition of heat.
• The smear is then rinsed with a very strong decolorizer, which strips the stain from all non-acid-fast cells but does not permeate the cell wall of acid-fast organisms. The decolorized non-acid-fast cells then take up the counterstain.

Mycolic acid in cell wall of acid fast bacteria retain carbol fuschin and responsible for their staining.