Microorganisms Flashcards
Acid fast tissues may be negative if the tissues are fixed in
Carnoy- will make acid fast into non-acid-fast
In the Fite method, the organism will stain
red
After Schiff reagent, tissues are rinsed in a sulfate solution to:
a. fix the stain in the tissue
b. differentiate the stain
c. remove the excess leucofuchsin
d. oxidize the tissue
remove the excess leucofuchsin
In the Brown-Hopps modification of the Gram stain for tissues, Gram-positive tissues will stain what color?
blue-black
The property that acid-fast depends on is:
a. affinity for anionic dyes
b. capability for reducing silver
c. failure to stain with a dye other than basic fuchsin
d. ability to resist decolorization with dilute acid
ability to resist decolorization with dilute acids
Which of the following is a method for demonstration of fungi?
a. Ziehl-Neelson
b. Warthin-Starry
c. Giemsa
d. PAS
PAS. Ziehl-Neelson (acid fast), Warthin-Starry (spirochetes), Giemsa
The best stain for the demonstration of Mycobacterium leprae is
Fite
The PAS stain differs from the Gridley technique how?
oxidizer used. PAS uses periodic acid and Gridley uses chromic acid
Artifactual precipitate seen in the Grocott stain may be the result of using:
a. plastic forceps
b. gelatin in the water bath
c. glassware that was not chemically cleaned
d. excess time in the gold chloride solution
glassware that was not chemically cleaned
Spherical or ovoid bacteria are classified as
gram-negative or cocci
A medically important protozoan is:
a. Staphylococcus aureus
b. Giardia lamblia
c. Candida albicans
d. Clostridium tetani
Giardia lamblia- which causes an infection in the small intestine
The basic structure of a filamentous fungi is the:
a. hypha
b. bud
c. endospore
d. spherule
hypha - filamentous fungi are also called molds
The carbol-fuchsin methods are specific for:
a. mycobacteria
b. dimorphic fungi
c. diplococci
d. spore-forming bacilli
mycobacteria
The auromine-rhodanine technique demonstrates
Mycobacterium tuberculosis
Carbol-fuchsin contains:
a. acid fuchsin and HCl
b. acid fuchsin and phenol
c. basic fuchsin and HCl
d. basic fuchsin and phenol
basic fuchsin and phenol
Stains for the demonstration of spirochetes are based on their property of:
a. argentophilia
b. agyrophilia
c. metachromasia
d. acid-fastness
agyrophilia
The term mycosis is used to describe disease caused by
fungi
The differential staining achieved with the gram stain is due to the differences in the bacterial…
cell wall
Which of the following is a fluorescence technique?
a. Ziehl-Neelson
b. Warthin-Starry
c. auramine-rhodamine
d. Brown and Brenn
auramine-rhodamine
The PAS reaction will demonstrate fungi, because the cell walls contain:
carbohydrates
The Gridley stain uses what reagents?
chromic acid and Schiffs
In the Hotchkiss-McManus modification of the PAS technique, aldehydes are formed by which reagent?
periodic acid
The preferred fixative for Warthin-Starry is:
10% NBF
The “developer” in the Warthin-Starry stain is:
hydroquinone
Which of the following techniques demonstrates Pneumocystis jirovecci?
a. Grocott
b. Gridley
c. PAS
d. Kinyoun
Grocott
If fungi are to be demonstrates, a good counterstain for the PAS technique is:
light green
In the Gridley procedure, the aldehyde fuchsin stain will attach to what reagent?
Schiff Reagent
To differentiate Crytococcus neoformans from other yeast like fungi, which of the following stain should be performed?
a. PAS
b. Gridley
c. Grocott
d. Mayer mucicarmine
Mayer mucicarmine
To differentiate Crytococcus neoformans and other yeast like fungi is that only Crytococcus neoformans has a capsule containing…
mucin
T/F: Gram-positive organisms cannot be decolorized once stained with crystal violet.
False. The decolorization step is a relative one, and sections can be overdecolorized, removing the stain from both Gram-negative and positive organisms.
T/F: Gram-positive organisms cannot be decolorized once stained with crystal violet.
False. The decolorization step is a relative one, and sections can be overdecolorized, removing the stain from both Gram-negative and positive organisms.
T/F: A problem may result from allowing stains to dry during the Gram-staining process.
True. If sections are allowed to dry at any stage of the procedure, insoluble compounds may be formed that are difficult or impossible to decolorize.
T/F: The stains for spirochetes are agyrophil techniques.
True.
T/F: Rod-shaped bacteria are called bacilli.
True
T/F: Viral organisms are easily demonstrated with special histochemical stains.
False. Some viral organisms form inclusions that can only be seen with the electron microscope, but some form inclusions that can be seen with a light microscope. However, there is no histochemical stain for the viruses themselves. There are IHC and ISH stains that will stain for the virus.
T/F: A good Grocott methenamine silver 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. Avoid mercurial and chromate fixatives. Use 10% NBF.
T/F: Tissue containing Helicobacter pylori is a satisfactory control for the Diff-Quick Giemsa modification.
True.
T/F: The Gridley stain is more intense than the PAS.
False.
T/F: The mordant is applied after the primary dye in the Gram stain.
True
T/F: Peanut oil is used in the Ziehl-Neelson method.
False. Its used in the Fite methods.
T/F: Acid fast stains are satisfactory on tissue used in Carnoy solution.
False.
T/F: Iodine serves as a mordant in the Gram stain.
true
T/F: Helicobacter pylori is a spirochete.
False. It is a gram-negative bacteria making it cocci.
T/F: Helicobacter pylori is readily demonstrated by a Romanowsky-type stain.
True (Diff-Quik)
T/F: The Giemsa stain will differently stain the different types of bacteria.
False. All will stain the same color.
Acid fast organisms are seen on a section of lung within alveolar sacs. They appear to lie slightly out of plane of the section. This is most likely a result of…
contamination of the water bath
The methylene blue counterstain is too heavy on the Kinyoun acid fast stain, so that the organism present are very difficult to locate. This problem can most likely be corrected by…
backing the section up into acid-alcohol, then recounterstaining removing the coverslip and repeating the entire procedure.
Grocott stained sections from the lung of a patient known to have Histoplasma capsulatum show marked background staining, especially of reticulin and collagen. The most likely cause of this is…
Oxidation with periodic acid. Periodic acid is not as strong of an oxidizing agent as chromic acid (which Grocott uses) and periodic acid oxidation leads to increased background staining. Chromic acid has the advantage of decreased staining of connective tissue; only substances that contain large quantities of carbohydrates, such as fungal cell walls, mucin, and glycogen will remain active after chromic acid oxidation.
Scattered patchy blue ares are seen on the Brown and Hopps Gram stain although the decolorization step was prolonged. This is most likely the result of…
Drying of the section during the procedure
The background of Brown and Hopps Gram-stained section is an intense red. This could most likely be corrected in the future by changing the time in the:
a. iodine solution
b. Gallego solution
c. picric acid-acetone
d. crystal violet
Picric acid-acetone. This is the decolorizing step, so it should remove more basic fuchsin.
The control section containing both Gram positive and negative organisms only show gram positive organisms when stained with Brown and Hopps technique. This is most likely a result of…
Overdifferentiation with picric acid-acetone
A section of liver stained with the Grocott stain shows diffuse black staining over the entire section, making it difficult to see organisms. This could likely be corrected in the future by treating the liver sections with…
diastase prior to the beginning of the stain. Glycogen will stain prominently in liver sections stained with Grocott methenamine silver technique. So digestion of the glycogen prior to staining should be used to reduce background staining.
A section of lung from a patient with sputum cultures postivie for acid fast organisms give a negative result when stained with Ziehl-Neelson stain. To confirm that no organisms are present in the lung tissue, it would be best to stain new sections with…
auramine-rhodamine
The control section containing Coccidoidies immitis shows very pale pink-stained organisms on the PAS staine. This is most likely a result of…
old or overused reagents
The chromic acid keeps turning dark after using it only 2-3 times. This could most likely be corrected in the future by..
ensuring the complete removal of alcohol prior to chromic acid. If alcohol isnt completely removed, it will reduce the chromic acid and turn brown.
Grocott-stained sections show reticulum and red cells stained black. This most likely is the result of…
overimpregnation
Grocott stained sections from the lung of a patient with positive cultures of Histoplasma capsulatum do not reveal any organisms. The best course of action is to:
a. stain new sections with PAS
b. ensure that chromic acid is used as the oxidizer
c. repeat using fresh periodic acid
d. omit the sodium thiosulfate step
ensure that chromic acid is used as the oxidizer. False negatives can be obtained when periodic acid oxidation occurs.
