Acid Fast
Acid fast organisms have a thick cell wall that is waxy due to the presence of mycolic acids. As a result, these organisms resist decolourization by acid alcohol.
| Ziehl-Neelsen (ZN) Stain | Kinyoun Stain | |
|---|---|---|
| Primary Stain | Carbol fuchsin
|
Carbol fuchsin
|
| Decolourizer | 3% acid alcohol* | 3% acid alcohol* |
| Counterstain | Methylene blue | Methylene blue |
| ZN (Zinc) hot | Kinyoun, cold, concentrated |
*Modified acid fast stains use a lower concentration of acid alcohol (0.5-1.0%) for organisms with less mycolic acid present in their cell walls.
Acid Fast Organisms
- Mycobacteria (e.g., M. tuberculosis, M. leprae, etc.)
Partially Acid Fast Organisms
- Nocardia
- Legionella