Lab 3.7: Acid fast stains

Question 1

The presence of ?? acids in the cell walls of acid fat organisms is the cytological basis for the acid-fast differential stain

Answer 1

-mycolic

Question 2

Acid fast stain are used to identify members of:

Answer 2

-genus mycobacterium
-genus nocardia

Question 3

Because so few organisms are acid fast, the acid fast stain is only ran when??

Answer 3

-infection of acid fast organisms is suspected.

Question 4

2 types of acid fast staining procedures:

Answer 4

-Ziehl-Neelsen (ZN) method: uses heat as part of process
-kinyoun (K) method: slightly less sensitive

Question 5

What is used as the primary stain and why?

Answer 5

-carbolfuchsin
-because it is lipid soluble and penetrates the waxy cell wall

Question 6

Acid fast cells are what color?
Nonacid-fast cells are what color?

Answer 6

-reddish-purple
-blue

Question 7

Procedure steps for acid fast staining: (11)

Answer 7

-prepare heat fix smear
-add strip of bibulous paper
-add carbolfuchsin and heat by steam for 5 min
-rinse with water
-add decolorizer (acid alcohol) for 30 seconds
-rinse with water
add methylene blue for 1 min
-rinse with water
-blot dry
-observe under microscope (10X, 40X)
-add oil for 100X

Question 8

Upon completion of the acid-fast stain, cells without mycolic acid in the cell wall will appear:

Answer 8

-blue

Question 9

In the acid-fast staining procedure, why is the carbolfuchsin stain is left in contact with the cells for five minutes using steam?

Answer 9

-to allow the stain to penetrate the waxy wall of the cell

Question 10

What is not used at all in the acid-fast stain is:

Answer 10

-iodine

Question 11

In the acid-fast stain, the primary stain is:

Answer 11

-carbolfuchsin

Question 12

True or false:
The waxy substance that gives acid-fast cells a higher affinity for the primary stain also makes them susceptible to decolorization by an acid alcohol solution.

Answer 12

-false

Question 13

True or false:
The presence of mycolic acids in the cell walls of acid-fast organisms is the cytological basis for the acid-fast stain

Answer 13

-true

Question 14

In the acid-fast stain, the decolorizing agent is:

Answer 14

-acid alcohol

Question 15

The acid-fast stain is a:

Answer 15

-differential stain

Question 16

In the acid-fast stain, the counterstain is:

Answer 16

-methylene blue

Question 17

In the acid-fast procedure, why is the sample counterstained with methylene blue or brilliant green rather than safranin which is used as the counterstain in the Gram stain procedure?

Answer 17

-Safranin is pink like carbolfuchsin and would not allow one to differentiate between the cell types.