Differential Stain Flashcards
1
Q
Differential Stain
A
- Uses two stains to divide bacteria into 2 groups
- Gram Stain
- Acid-Fast Stain
- Endospore Stain
- Components: Primary Stain, Secondary Stain/Counterstain, Mordant, Decolorizer
2
Q
Gram Stain
A
- Differential stain
- Divides cells based on structure of cell wall
- Primary stain: Crystal violet
- Mordant: Iodine
- Decolorizer: 95% Ethanol
- Counterstain: Safranin
- Culture must be 16-18 hours old
- Must have thin smears
3
Q
Gram Positive Bacteria
A
- Purple (Blue)
- Thick layer of peptidoglycan
- Teichoic acid and lipoteichoic acid
- Crystal violet is retained by peptidoglycan
4
Q
Gram Negative Bacteria
A
- Pink
- Thin layer of peptidoglycan
- Outer membrane contains lipoproteins and lipopolysaccharides
- Fats are soluble in 95% Ethanol
- Decolorizer makes outer membrane porous so the crystal violet washes out.
5
Q
Acid-Fast Stain
A
-Used as a diagnostic tool
-2 methods
>Ziehl Neelson Method (hot method):
+Primary Stain: Carbol fuchsin (contains phenol)
+Mordant: Steam from hot water bath
+Decolorizer: Acid Alochol (95% ethanol w/HCl)
+Counterstain: Methylene blue
>Kinyoun Method (cold method):
+Different is in mordant
+Increased [phenol] in Carbol fuchsin (no steam)
+Primary Stain, Secondary Stain, and Decolorizer are the same
Bacteria Used
(+) Mycobacterium smegmatis
(-) Staphylococcus epidermis
6
Q
Acid-Fast Positive
A
- Only 2 genera:
- Mycobacterium (large bacilli)
- Nocardia (only some)
- Have mycolic acid in cell wall, which is a waxy material making it difficult to stain
