Ziehl neelsen

Question 1

What is the
classification
target tissue
staining principle
mechanism of staining
and control

for Ziehl Neelsen

Answer 1

classification - micro-org stain

target tissue-Mycobacterium TB

staining principle- acid fastness

mechanism of staining - ionic bonding

and control -appendix

Question 2

What is Mycobacterium tuberculosis cell wall composed of

Answer 2

-cell wall has mycolic acid with negatively charged carboxyl groups that the dye binds too

-lipid capsule has a high MW so it is waxy a RT and therefore cant stain with regular stains

-if you expose them to acid the lipids in the cell wall can get removed so avoid acid fixatives like carnoys

Question 3

Step 1 - staining

Answer 3

done at 60C
done with carbol fuchsin with phenol and alcohol

-stains by ionic bonding
positively charged fuchsin binds negatively charged carboxyl groups in mycolic acid

Question 4

STEP 2: Decolorization

Answer 4

acid alcohol to help break bonds between tissue and acid fuchsin

-MTB can retain dye because of the lipids

acid fastness is being able to retain dye with treated with dye

Question 5

STEP 3: Counterstain

Answer 5

-Methylene blue, Light green
-Basic dye (positively charged)
-Primarily stains nuclei, but will also stain the cytoplasm pale blue

-Mechanism of staining - Ionic bonding