Microorganisms Flashcards
What is the purpose of gram staining tissue sections?
Differentiate/ demonstrate gram positive and negative organisms
What is the principle of gram staining?
Physical theory - porosity
What is the difference between a mordant and a trapping agent?
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.
What are modifications of the gram stain? what is the purpose of modifying it?
- Gram twort
- Brown and Brenn
- Addition of a 3rd dye to enhance gram negative organsim
What will Gram Twort stain?
Cytoplasm = green
What will Brown and Brenn stain?
Cytoplasm = yellow
What is the purpose of the Ziehl-Neelsen method?
Demonstration of acid fast bacteria in tissue?
What is the principle behind acid fast stains?
Chemical vs solubility
What is the counterstain in the Ziehl-Neelsen method?
Methylene Blue
What is the primary stain in the Ziehl-Neelsen method? And what does it target?
Basic Fuchsin - Mycolic acid
What will acid fast bacili stain after using the Ziehl-Neelsen method?
Red
How should sections be decolourized in the Ziehl-Neelsen method?
1% HCl + 70% ethanol
What are the modifications of the Ziehl-Neelsen method?
- Kinyoun - cold
- Fite - enhancement
- Auramine and Rhodamine fluorescence
What is the purpose of using Fite in the demonstration of acid fast bacteria?
enhance weakly acid fast bacteria
What substances are used for the fite method for demonstrating acid fast bacteria?
Peanut oil & xylene
What is the purpose of the warthin starry method?
Demonstration of spirochetes
What is the principle behind the Warthin starry method?
Argyrophilic reactions
What is the reducing agent used in the Warthin starry method?
hydroquinone
What will spirochetes, H.pylori and klebsiella stain following the Warthin starry method?
Black
What will nuclei stain following the Warthin starry method?
Brown
What will the background stain following the Warthin starry method?
golden Yellow
You overstain a sections containing spirochetes with the Warthin starry method, how would you proceed?
- Remove the stain with iodine and hypo
- Re-stain
What is the purpose of the Steiner and Steiner method?
Demonstrate spirochetes, H.pylori, cat scratch, legionella and pneumophilia
What is the principle of the Steiner and Steiner method?
Argyrophilic reactions
What is the reducing agent in the Steiner and Steiner method?
Gum mastic + hydroquinone + absolute alcohol
What will the bacteria look like following staining with the Steiner and Steiner method?
Brown / black
What will the background look like following staining with the Steiner and Steiner method?
Light yellow
What are the 5 method to H.pylori identification.
- Diff quick
- Dye-based histochemical stains
- True Giemsa stain
- Silver stains
- IHC
What are 4 demonstration methods of fungus?
- H&E
- Gram stains
- PAS
- Silver impregnation
What is the purpose of Grocott’s Methenamine silver?
Demonstrate fungi, actinomyces and norcardia.
What is the principle of Grocott’s Methenamine silver?
Argentaffin reactions
Which fixative should be avoid when staining with Grocott’s Methenamine silver? WHY?
Glutaraldehyde - because it contains free aldehydes which will reduce silver.
what is the counterstain in Grocott’s Methenamine silver method?
Light green
What will fungi stain following Grocott’s Methenamine silver method?
Black
What should you do prior to staining a liver section with Grocott’s Methenamine silver method?
Diastase to remove glycogen
