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.
T/F: Acid-fast reactions are satisfactory on tissues fixed in Carnoy solution.
False, Carnoy should never be used as a fixative for acid-fast reactions.
T/F: Iodine serves as a mordant in the Gram stain.
True.
T/F: H. Pylori is a spirochete.
False, it is a Gram-bacillus.
H. Pylori is readily demonstrated by a Romanowsky type stain.
True.
T/F: The Giemsa stain will differently stain different bacteria.
False, they will all be the same color.
Acid-fast organisms are seen on a section of lung with normal alveolar sacs. They appear to be slightly out of the plane of the section. What happened?
There was possible contamination from the water bath.
The methylene blue counterstain is too heavy on the Kinyoun acid-fast stain, so that the organisms present are very difficult to locate. How can this be corrected?
Backing up the section in acid alcohol, then recounterstaining, removing the coverslip and repeating the entire procedure.
GMS stained sections from the lung of a patient known to have Histoplasma capsulatum show marked background staining, especially of reticulin and collagen. What is the most likely cause of this?
Accidental oxidation with periodic acid, chromic acid should have been used.
Scattered patchy blue areas are seen on the Brown & Hopps Gram stain, although the decolorization step was prolonged. This is most likely the result of:
The section was accidentally dried at some point.
The background of a Brown & Hopps Gram stained section is an intense red. This can be corrected in the future by:
Increased time in the picric acid-acetone.
The control section containing both Gram - and Gram + organisms shows only Gram + organisms when stained with the Brown & Hopps technique. This is most likely the result of:
Overdifferentiation with the picric acid-acetone.
A section of liver stained with the GMS stain shows diffuse black staining over the entire section, making it difficult to see organisms. This can be most likely corrected in the future by:
Treating the liver sections with diastase prior to staining to remove the glycogen.
A section of lung from a patient with sputum cultures positive for acid-fast organisms gave a negative result when stained with the Ziehl-Neelsen method. To confirm that there are no microorganisms in the lung tissue, it would be best to stain a new section with:
The auramine-rhodamine method.
The control section containing Coccidioides immitis shows very pale pink stained organisms on the PAS stain. This is most likely the result of:
Old or overused reagents.
The chromic acid keeps turning dark after only 2-3 uses. This can most likely be corrected in the future by:
Ensuring the complete removal of alcohol prior to chromic acid.
GMS stained sections show reticulin and red cells stained black. This is most likely the result of:
Overimpregnation with methamine silver.
GMS stained sections from the lung of a patient with positive cultures of Histoplasma capsulatum do not reveal any organisms. The best course of action would be to:
Ensure that chromic acid has been used as the oxidizer, to avoid a false negative.
What is the sequence of reactions in the Wilder and Snook ammoniacal silver method for demonstrating Retic fibers?
Oxidation, Sensitization, Silver impregnation and Reduction.
What is the largest portion of the brain?
The cerebrum.
Hemosiderin- laden macrophages present in the alveolar space of the lung can be distinguished from other pigmented macrophages by what reaction?
The Prussian blue reaction.
What pigment is commonly known as a “wear and tear pigment” or “brown atrophy”?
Lipofuchsin.
To properly classify bone, it may be described as:
It can be classified as either cancellous or compact.
Where is melanin commonly found?
Skin.
A Gram stain has been done on reactive, inflammatory lymph node and the background structures are stained an intense red which makes identification of Gram negative organisms very difficult. What happened?
The differentiation in picric acid-acetone was poor.
What acid in an alcohol solution is most commonly used to differentiate aluminum-hematoxylin stained sections?
Hydrochloric acid in alcohol (acid alcohol).
What is a metachromatic stain used for identifying mast cells?
Toludine blue.
Connective tissue proper refers to tissue composed of:
Collagen, reticulin and elastin.
What is the purpose of iodine (Lugols) in the Gram procedure?
It forms a dye complex with the crystal violet.
The terms “squamous”, “cuboidal”, and “columnar” describe cells of which tissue type?
Epithelium.
What is the atomic grouping within a dye that gives it its color?
Chromophore.
What stain commonly uses hydroquinone?
The Bodian stain.
Bacteria stain either Gram positive or Gram negative due to differences in:
Differences in cell walls.
Which of the following chemicals is used as both a mordant and a differentiator in the Weil stain for myelin?
Ferric ammonium sulfate.
Fixation of tissues for 2 weeks in which of the following will most likely impair nuclear basophilia?
Zenker solution, fixation should never exceed 24 hours.
A researcher wishes to differentiate the different types of granulocytes in a tissue section. What would be the stain of choice?
A Romanowsky stain.
What is a substance that has the ability to both bind and reduce silver to a visible metallic form?
Argentaffin.
After H&E staining, the cytoplasm in a tissue section appears hazy, obscure and contrasts poorly with the nuclei. What happened?
The slides were not adequately dehydrated.
Microscopic review of auramine-rhodamine stained control slides will reveal:
Mycobacteria.
When the auxochrome of a dye is the COOH group, the dye is:
Anionic.
The Stein and Hall techniques are based on the conversion of bile pigment to:
The bile pigment is converted to biliverdin.
What is the acid used in the Prussian blue reaction?
Hydrochloric acid.
Areolar connective tissue is also known as:
Loose connective tissue.
What is a hematoxylin solution that is ONLY used progressively?
Mayer hematoxylin.
Nuclei stained with hematoxylin are predominately red-brown to red. This is most likely because of the use of:
Overoxidized hematoxylin.
To achieve the desired intensity of purple when using the Gomori Aldehyde fuchsin stain for demonstrating elastic tissue, the paraldehyde used to prepare the reagent should be:
Fresh.
Microscopic evaluation of an H&E stained section shows a pink artefact surrounding the tissue and in tissue spaces. The most probable cause of this artefact is:
Surplus adhesive on the slide.
In the Mallory phosphotungstic acid-hematoxylin (PTAH) method, skeletal muscle striation stain what color?
Blue.
Acidophilic tissue components that should appear stained different shades of pink following H&E staining are:
Muscle, collagen and RBCs.
In order for the Gram stain to work properly, it is important to apply the mordant:
After the crystal violet.
What stain uses a methenamine solution?
Both the Gomori and Grocott stains.
Differential staining of nuclei and cytoplasm with Giemsa solution is an example of:
Polychromasia.
What histologic feature is unique to muscle tissue?
Intercalated discs.
What is a pigment that is present on the surface of tissues but not within them?
Artefactual pigments.
Oligodendroglia are cells that function in the production and maintenance of myelin sheaths that surround:
axons.
What is an example of a metachromatic stain?
Toludine blue.
What procedure will demonstrate most amoebae in tissue?
The PAS procedure.
What is an iron hematoxylin solution that is frequently used for nuclear staining?
Weigert hematoxylin.
What pigment is formed following a reaction of ferrous ions with potassium ferricyanide?
Turnbull blue.
What is the stain procedure that produces a red-orange result for calcium deposits in tissue?
Alizarin red S.
What are connective tissue cells that have many cytoplasmic granules that stain metachromatically?
Mast cells.
