week 5: lab 12 (acid fast staining)

Question 1

what are the common genera of Acid-fast bacteria?

Answer 1

Mycobacterium M.
leprae M.
tuberculosis, M.

Question 2

what are the clinically significant diseases acid-fast bacteria cause?

Answer 2

tuberculosis and certain other infections

Question 3

how do you perform acid-fast staining, the Ziehl-Neelsen method?

Answer 3

-uses steam to melt: (uses HEAT FIXING)
-Steaming the smear over boiling water permits the entry of primary stain (carbol fuchsin)
-After cooling, stain is trapped as the cell wall solidifies.
-Decolorizer (acid-alcohol) removes any stain that wasn’t trapped.
-Counter stain (methylene blue) binds to non-acid fast cells

Question 4

what are the characteristics of acid-fast cells?

Answer 4

-Waxy cell wall rich in mycolic acid
○ Prevents drying and resistant disinfectants
-Water soluble stains like those in Gram-staining are not efficient
○Stains are repelled

Question 5

what are the two methods for staining acid-fast cells?

Answer 5

Ziehl-Neelsen
-Utilizes heat
Kinyoun
-Higher concentrations of detergent

Question 6

how do you perform acid-fast staining, the Kinyoun method?

Answer 6

-high levels of detergent: (uses HEAT FIXING)
-Requires higher levels of phenol to breakdown membranes in the primary stain (carbol fuchsin)
-Decolorizer (acid-alcohol) removes any stain that wasn’t trapped.
-Counter stain (methylene blue) binds to non-acid
fast cells

Question 7

what is the difference between acid-fast positive and acid-fast negative?

Answer 7

positive- you have active TB
negative -you probably don’t have active TB

Question 8

acid-fast stain appears:

Answer 8

red/pink

Question 9

acid-fast cells appears:

Answer 9

blue