Principle

PRINCIPLE
  • Acid fast staining is an important differential staining technique.
  • The primary stain referred to as acid fast stain binds strongly to only bacteria having waxy material on the cell wall. This method is used to identify organisms under the genus Mycobacterium.
  • The important pathogenic species under this genus are M.tuberculosis, M.bovis, M.avium,M.partuberculosis and M.leprae. In this method strong carbol fuchsin is used as the primary stain, acid alcohol mixture is used as decoloriser and methylene is used as counter stain.
  • The acid fast organisms retain the colour of the primary stain i.e., red, where as the non acid fast organisms take the color of methylene blue.
  • The acid fastness is due to presence of waxes (mycolic acid) in the cell wall of the organisms.
  • The acid fast organisms can withstand the decolorising action of acid alcohol mixture where as the non acid fast organisms can not.
Last modified: Sunday, 4 December 2011, 7:24 AM