ziehl neelson

Question 1

purpose/target of ziehl neelson

Answer 1

acid-fast mycobacteria (tuberculosis)

Question 2

principle/mechanism of staining in ziehl neelson

Answer 2

regressive staining

Lipid capsules of mycobacteria have mycolic acids which are free fatty acids (have carboxyl groups as binding sites)
Carbol fuchsin (dye) binds carboxyl groups and stays in cell wall while other components are decolorized

Question 3

counter stain for ziehl neelson

Answer 3

methylene blue

Question 4

methylene blue is the (primary/counter) _______ stain for ziehl neelson?

Answer 4

counterstain

Question 5

carbol fuchsin purpose in ziehl neelson?

Answer 5

primary stain for mycobacteria

Question 6

what is the primary stain in ziehl neelson

Answer 6

carbol fuchsin

Question 7

what colour does the target stain in ziehl neelson

Answer 7

pink/bright red (carbol fuchsin)

Question 8

acid alcohol purpose in ziehl neelson?

Answer 8

removes carbol fuchsin except from mycobacteria

Question 9

what colour does the background and other tissue components stain in ziehl neelson?

Answer 9

blue (methylene blue counterstain)

(except red blood cells will stain red)

Question 10

purpose/target of Fite stain?

Answer 10

mycobacterium leprae (leprosy bacteria)

Question 11

which fixative to avoid for ziehl neelson/fite?

Answer 11

carnoy’s fixative. (removes acid-fastness)

Question 12

what happens if tissue is fixed in carnoy’s fixative before staining with ziehl neelson/fite?

Answer 12

acid fastness removed. stain ruined

Question 13

why don’t mycobacteria (ziehl neelson/fite) get stained by gram twort?

Answer 13

(thick waxy capsule, impermeable to stain at RT)