Staining Techniques Flashcards
What is the simplest preparation method for specimens?
The simplest preparation is the wet mount.
What is fixation in specimen preparation?
Fixation is the process of attaching cells to a slide, often achieved by heat or chemical treatment.
What does fixation do to microorganisms?
Fixation kills microorganisms, stopping their movement and preserving cellular integrity for observation.
What are some chemical agents used for fixation?
Chemical agents include acetic acid, ethanol, methanol, formaldehyde (formalin), and glutaraldehyde.
Why are chemical agents preferable to heat for tissue specimens?
Chemical agents are preferable because they denature proteins, stop biochemical reactions, and stabilize cell structures.
What is the purpose of staining specimens?
Staining is applied to color features of a specimen before examination.
What are the components of stains/dyes?
Stains/dyes contain salts made of positive and negative ions.
What is a chromophore?
Chromophore is the colored ion in a dye.
What is a counterion?
Counterion is the uncolored ion in a dye.
What is the difference between basic and acidic dyes?
Basic dyes have a positive chromophore, while acidic dyes have a negative chromophore.
What is a positive stain?
A positive stain adds color and is absorbed by the cell/organism, making them stand out against the background.
What is negative staining?
Negative staining is absorbed by the background but not the cells, producing an outline or silhouette.
What types of dyes are used as positive stains?
Basic dyes such as basic fuchsin, crystal violet, malachite green, methylene blue, and safranin are used.
What types of dyes are used as negative stains?
Acidic dyes such as acid fuchsin, eosin, and rose bengal are used.
What is simple staining?
Simple staining uses a single dye to emphasize structures, making all organisms appear the same color.
What is differential staining?
Differential staining distinguishes organisms using more than one stain, resulting in different colors for different organisms.
What is Gram staining?
Gram staining distinguishes between bacteria with different cell walls (gram negative and gram positive).
What are the steps in Gram staining?
- Add crystal violet stain (cells turn blue/purple). 2. Add iodine (mordant). 3. Add decolorizing agent (ethanol/acetone). 4. Add safranin (counterstain).
What happens to gram positive and gram negative cells during Gram staining?
Gram positive cells remain purple, while gram negative cells become pink after safranin is added.
What is acid-fast staining?
Acid-fast staining determines between two types of gram-positive bacteria based on the presence of waxy mycolic acids.
What are the two methods of acid-fast staining?
The Ziehl-Neelsen technique and the Kinyoun technique.
What is capsule staining?
Capsule staining identifies a microbe’s virulence and often uses negative staining techniques.
What is the common technique for identifying encapsulated yeast?
Adding drops of India ink or nigrosin.
What is endospore staining?
Endospore staining differentiates endospores from the rest of the cell using two stains.
