Chapter 10: Microorganisms Flashcards
Acid-fast stains may be negative if the tissue was fixed in:
Carnoy, it will make the tissue non-acid fast.
With the Fite stain, what color does the microorganisms stain?
Red, by Carbol Fucshin.
After Schiff reagent, tissues are rinsed in a sulfite solution in order to:
Remove the excess leucofuchsin.
In the Brown-Hopps modification of the Gram stain for tissues, Gram + organisms appear:
Blue-black.
The property on which the acid-fast stain depends is its:
Ability to resist decolorization with dilute acids.
What is a good stain for demonstrating fungii?
The PAS method.
What is the best stain for the demonstration of Mycobacterium leprae?
The Fite method.
How does the PAS differ from the Gridley technique?
The type of oxidizer used. The PAS uses periodic acid and the Gridley method uses chromic acid.
Artifactual precipitate seen in the Grocott (GMS) stain may be the result of using:
Unclean (non-chemically cleaned) glassware.
Sperical or ovoid bacteria are classified as:
Cocci.
A medically important protozoan is:
Giardia lambia.
The basic structure of filamentous fungi is the:
Hypha.
What are carbol-fuchsin methods specific for?
Mycobacteria.
The auramine-rhodamine technique will demonstrate:
Mycobacterium tuberculosis.
What does carbol-fuchsin contain?
Basic fuchsin and phenol (carbolic acid).
The term “mycosis” is used to describe a disease caused by:
Fungi.
Stains for the demonstration of spirochetes are based on their property of:
Argyophilia, they bind to silver and don’t reduce it.
The differential staining achieved with the Gram stain is due to what?
Differences in the bacterial cell walls.
What is a common fluorescence technique?
The auramine-rhodamine.
The PAS reaction will demonstrate fungi, because the cell wall contains:
Carbohydrates.
What does the Gridley stain use?
Chromic acid and schiff reagent.
In the Hotchkiss-McManus modification of the PAS technique, how are aldehydes formed?
The periodic acid.
What is the preferred fixative for the Warthin-Starry technique?
10% NBF.
What is the “developer” in the Warthin-Starry stain?
Hydroquinone.
What technique will demonstrate Pneumocystis jiroveci?
The Grocott (GMS stain)
If fungi are to be demonstrated, a good counterstain for PAS would be:
Light green.
In the Gridley procedure, the aldehyde fuchsin stain will adhere to:
Schiff reagent.
To differentiate Cryptococcus neoformans from other yeast-like fungi, what stains should be performed?
Mayer mucicarmine, alcian blue and colloidal iron.
The difference between Cryptococcus neoformans and other yeast-like fungi is that:
Cryptococus neoformans has a mucoid capsule that can be demonstrated used for acid mucosubstances.
T/F: Gram + organisms CANNOT be decolorized once stained with crystal violet.
False, the decolorization step is relative.
T/F: A problem may result from allowing the slides to dry during the gram staining process.
True, insoluble compounds will be formed.
T/F: The stains for spirochetes are argyrophil techniques.
True.
T/F: Rod-shaped bacteria are called bacilli.
True.
T/F: Viral organisms are easily demonstrated with special histochemical stains.
False, there are a few IHC and ISH stains that can somewhat show them, but it’s not very good.
T/F: A “good” GMS stain shows organisms with a crisp black cell wall and a visible internal structure.
True.
T/F: Mercurial fixatives are satisfactory when stains for spirochetes are to be done.
False, 10% NBF is preferred.
T/F: Tissue containing H. Pylori is a satisfactory control for the Diff Quik giemsa modification.
True.
T/F: The Gridley stain is more intense than the PAS.
False, the PAS stain is more intense.
T/F: The mordant is applied after the primary dye in the Gram stain.
True.
T/F: Peanut oil is used in the Ziehl-Neelsen method.
False, peanut oil is mixed with xylene in the Fite reaction.