STAINING TECHNIQUES Flashcards
-> organic or aqueous preparations of dyes that impart a variety of color to tissue or microorganisms
• Differentiate or identify structures and characteristics of bacteria
Dyes or stains
- ion that imparts the color
Chromophore
The chromophore is a positive ion -›____
• methylene blue, crystal violet, carbol fuchsin, malachite green, safranin
BASIC STAIN
- The chromophore is a negative ion -› _______
eosin, nigrosin, picric acid
ACIDIC STAIN
• -> ion not giving off the color
Counterion
• directly stains bacteria and bacterial structure
bacteria absorbs the stain
DIRECT STAINING
• No special structures are seen
Stain evenly dyes the bacteria
The stain is flooded across the smear
Simple Staining
• Only one type of dye is used
• No special structure of a cell is distinguished
• eg. methylene blue
Simple Staining
• Can visualize bacterial structures
• Can isolate specific parts of bacterial structure
Selective/Special Staining
-> Not easily colorized, not easily decolorized
-> Impenetrable
Endospore Stain or Schaeffer-Fulton stain
Differential Staining
• Two Types:
Gram Stain
Acid Fast Stain
-> The first stain used in the procedure
-> A stain that will impart the color
Initial/Primary Stain
•
-> allow stains to stick to the bacteria
- for a bridge between cell and stain
Mordant
-› no chemical eg. heat or cold
-› ferrous sulfate, iodine, tannic acid
Physical Mordant
Chemical Mordant
-> Removes color
-> Bacteria in question retain the color
-> Bacteria without the specific structure or composition in them will not retain the color
Decolorizer
- Bacteria that were decolorized will absorb the color
Counterstain/Secondary Stain
• Negative/Relief Staining
• The background is stained instead for contrast
- Demonstrate the HALO EFFECT
• DRY INDIA INK/NIGROSINE STAIN
INDIRECT STAINING
TYPES OF IONIZABLE DYES USED IN STAINING BACTERIA
Basic dyes
Acidic dyes
▪ Commonly used in bacteriology
▪ These are cationic dyes with positively charged groups that adhere to negatively charged molecules.
BASIC DYES
positive
Basic dyes
Includes:
METHYLENE BLUE
MALACHITE GREEN
BASIC FUCHSIN
CRYSTAL VIOLET
SAFRANIN
▪ These are anionic dyes with negatively charged group that bind to positively charged cell structures
ACIDIC DYES
ACIDIC DYES
EOSIN
ACID FUCHSIN
ROSE BENGAL