another differential stain
-->differentiates into distinctive groups by binding strongly only to bacteria that have a waxy materia
l in their cell walls.
Myobacterium tuberculosis & M.leprae(leprosy) and both pathogenic, and Nocardia.
- 1.Carbolfuchsin (red dye) applied to fixed smear slide THEN heated (enchances penetration and retention of dye).
- 2. Let slide cool, water rinsed.
- 3.THEN slide is given acid-alcohol (decolorizer: removed red stain from bacter that are NOT acid-fast).
- **Note: carbolfuchsin is more soluble in cell wall lipids than acid-alcohol, bacteria that lack lipids in their cell wall will have the red color rapidly removed--> leaves it colorless.
THEN smear is stained with methylene blue
(as a counter stain)
so that non acid-fast cells become blue.