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Flashcards in Lab 6 Deck (10):

1. What are the 8 steps and reagents used in the acid-fast stain?

1. place small paper towel over slide
2. saturate paper towel with carbolfuchsin, let sit 1 minute
3. apply gentle heat, keep moist for 5 minutes
4. remove paper and let for 1 minute
5. rinse slide with water until clear
6. decolorize with acid/alcohol until colorless
7. rinse with water and counterstain with Methylene Blue for 1 minute
8. rinse with water and blot dry


What is the function Carbolfuchsin?

turns cell reddish purple color, this is lipid soluble and penetrates the waxy cell


What is the function of steam heat?

enhances the entry of carbofuchsin into cells. Heat melts the wax and allows cells to penetrate.


What is the function of the acetone/alcohol?

removes the stain from acid fast negative cells. Acid fast cells resist decolorization.


What is the function of the Methylene Blue?

counterstains acid fast negative cells and turns them blue.


What color is acid fast positive?



What color is acid fast negative?



2. What two genera did we discuss that are acid-fast bacteria?

Mycobacteria and Nocardia


3. What component of their cell wall is responsible for their acid-fast property?

The waxy substance (mycolic acid) is compatible with the primary stain and resistant to decoloization by the acid/alcohol solution.


4. What important diseases are associated with acid-fast bacteria?

TB, Leprosy, HIV/AIDS