Microorganisms

Question 1

What is the purpose of gram staining tissue sections?

Answer 1

Differentiate/ demonstrate gram positive and negative organisms

Question 2

What is the principle of gram staining?

Answer 2

Physical theory - porosity

Question 3

What is the difference between a mordant and a trapping agent?

Answer 3

Mordant:
- Used with acidic dyes, usually metallic and is applied before the dye.
Trapping agent:
- used with basic dyes, are not usually metallic and is applied after the dye but prior to removing excess dye.

Question 4

What are modifications of the gram stain? what is the purpose of modifying it?

Answer 4

• Gram twort
• Brown and Brenn
• Addition of a 3rd dye to enhance gram negative organsim

Question 5

What will Gram Twort stain?

Answer 5

Cytoplasm = green

Question 6

What will Brown and Brenn stain?

Answer 6

Cytoplasm = yellow

Question 7

What is the purpose of the Ziehl-Neelsen method?

Answer 7

Demonstration of acid fast bacteria in tissue?

Question 8

What is the principle behind acid fast stains?

Answer 8

Chemical vs solubility

Question 9

What is the counterstain in the Ziehl-Neelsen method?

Answer 9

Methylene Blue

Question 10

What is the primary stain in the Ziehl-Neelsen method? And what does it target?

Answer 10

Basic Fuchsin - Mycolic acid

Question 11

What will acid fast bacili stain after using the Ziehl-Neelsen method?

Answer 11

Red

Question 12

How should sections be decolourized in the Ziehl-Neelsen method?

Answer 12

1% HCl + 70% ethanol

Question 13

What are the modifications of the Ziehl-Neelsen method?

Answer 13

• Kinyoun - cold
• Fite - enhancement
• Auramine and Rhodamine fluorescence

Question 14

What is the purpose of using Fite in the demonstration of acid fast bacteria?

Answer 14

enhance weakly acid fast bacteria

Question 15

What substances are used for the fite method for demonstrating acid fast bacteria?

Answer 15

Peanut oil & xylene

Question 16

What is the purpose of the warthin starry method?

Answer 16

Demonstration of spirochetes

Question 17

What is the principle behind the Warthin starry method?

Answer 17

Argyrophilic reactions

Question 18

What is the reducing agent used in the Warthin starry method?

Answer 18

hydroquinone

Question 19

What will spirochetes, H.pylori and klebsiella stain following the Warthin starry method?

Answer 19

Black

Question 20

What will nuclei stain following the Warthin starry method?

Answer 20

Brown

Question 21

What will the background stain following the Warthin starry method?

Answer 21

golden Yellow

Question 22

You overstain a sections containing spirochetes with the Warthin starry method, how would you proceed?

Answer 22

• Remove the stain with iodine and hypo
• Re-stain

Question 23

What is the purpose of the Steiner and Steiner method?

Answer 23

Demonstrate spirochetes, H.pylori, cat scratch, legionella and pneumophilia

Question 24

What is the principle of the Steiner and Steiner method?

Answer 24

Argyrophilic reactions

Question 25

What is the reducing agent in the Steiner and Steiner method?

Answer 25

Gum mastic + hydroquinone + absolute alcohol

Question 26

What will the bacteria look like following staining with the Steiner and Steiner method?

Answer 26

Brown / black

Question 27

What will the background look like following staining with the Steiner and Steiner method?

Answer 27

Light yellow

Question 28

What are the 5 method to H.pylori identification.

Answer 28

- Diff quick - Dye-based histochemical stains - True Giemsa stain - Silver stains - IHC

Question 29

What are 4 demonstration methods of fungus?

Answer 29

- H&E - Gram stains - PAS - Silver impregnation

Question 30

What is the purpose of Grocott’s Methenamine silver?

Answer 30

Demonstrate fungi, actinomyces and norcardia.

Question 31

What is the principle of Grocott’s Methenamine silver?

Answer 31

Argentaffin reactions

Question 32

Which fixative should be avoid when staining with Grocott’s Methenamine silver? WHY?

Answer 32

Glutaraldehyde - because it contains free aldehydes which will reduce silver.

Question 33

what is the counterstain in Grocott’s Methenamine silver method?

Answer 33

Light green

Question 34

What will fungi stain following Grocott’s Methenamine silver method?

Answer 34

Black

Question 35

What should you do prior to staining a liver section with Grocott’s Methenamine silver method?

Answer 35

Diastase to remove glycogen