Exercise 27

Question 1

Acid fast stain is aka

Answer 1

Ziehl Neelsen acid fast staining technique

Question 2

Acid fast stain purpose

Answer 2

ID bacteria with mycolic acid in cell wall
Genera’s Mycobacterium and Nocardia

Question 3

Mycolic acid

Answer 3

Hydrophobic, waxy lipid layer in the cell wall that prevents the uptake of dyes
Forms external layer around thin pg cell wall in acid-fast bacteria

Question 4

Heat fix?

Answer 4

Yes

Question 5

Primary stain

Answer 5

Carbolfuchsin, penetrates the waxy mycolic acid layer

Question 6

Mordant

Answer 6

Steam

Question 7

Decolorizer

Answer 7

Acid alcohol, mixture of alcohol and hydrochloric acid that allows for the removal of carbolfuchsin from cell walls without mycolic acid but not cell walls with mycolic acid

Question 8

Why is it called acid-fast

Answer 8

Cells with mycolic acid are resistant to decolonization by acid-alcohol

Question 9

Counterstain

Answer 9

Methylene blue, stains cells that are not acid-fast

Question 10

Positive control

Answer 10

Mycobacterium smegmatis

Question 11

Negative control

Answer 11

Micrococcus luteus

Question 12

Stain results

Answer 12

Acid fast cells red/pink, non acid-fast blue