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HTL > Microorganisms > Flashcards

Microorganisms Flashcards

1
Q

Acid fast tissues may be negative if the tissues are fixed in

A

Carnoy- will make acid fast into non-acid-fast

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2
Q

In the Fite method, the organism will stain

A

red

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3
Q

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

A

remove the excess leucofuchsin

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4
Q

In the Brown-Hopps modification of the Gram stain for tissues, Gram-positive tissues will stain what color?

A

blue-black

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5
Q

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

A

ability to resist decolorization with dilute acids

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6
Q

Which of the following is a method for demonstration of fungi?

a. Ziehl-Neelson
b. Warthin-Starry
c. Giemsa
d. PAS

A

PAS. Ziehl-Neelson (acid fast), Warthin-Starry (spirochetes), Giemsa

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7
Q

The best stain for the demonstration of Mycobacterium leprae is

A

Fite

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8
Q

The PAS stain differs from the Gridley technique how?

A

oxidizer used. PAS uses periodic acid and Gridley uses chromic acid

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9
Q

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

A

glassware that was not chemically cleaned

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10
Q

Spherical or ovoid bacteria are classified as

A

gram-negative or cocci

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11
Q

A medically important protozoan is:

a. Staphylococcus aureus
b. Giardia lamblia
c. Candida albicans
d. Clostridium tetani

A

Giardia lamblia- which causes an infection in the small intestine

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12
Q

The basic structure of a filamentous fungi is the:

a. hypha
b. bud
c. endospore
d. spherule

A

hypha - filamentous fungi are also called molds

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13
Q

The carbol-fuchsin methods are specific for:

a. mycobacteria
b. dimorphic fungi
c. diplococci
d. spore-forming bacilli

A

mycobacteria

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14
Q

The auromine-rhodanine technique demonstrates

A

Mycobacterium tuberculosis

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15
Q

Carbol-fuchsin contains:

a. acid fuchsin and HCl
b. acid fuchsin and phenol
c. basic fuchsin and HCl
d. basic fuchsin and phenol

A

basic fuchsin and phenol

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16
Q

Stains for the demonstration of spirochetes are based on their property of:

a. argentophilia
b. agyrophilia
c. metachromasia
d. acid-fastness

A

agyrophilia

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17
Q

The term mycosis is used to describe disease caused by

A

fungi

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18
Q

The differential staining achieved with the gram stain is due to the differences in the bacterial…

A

cell wall

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19
Q

Which of the following is a fluorescence technique?

a. Ziehl-Neelson
b. Warthin-Starry
c. auramine-rhodamine
d. Brown and Brenn

A

auramine-rhodamine

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20
Q

The PAS reaction will demonstrate fungi, because the cell walls contain:

A

carbohydrates

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21
Q

The Gridley stain uses what reagents?

A

chromic acid and Schiffs

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22
Q

In the Hotchkiss-McManus modification of the PAS technique, aldehydes are formed by which reagent?

A

periodic acid

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23
Q

The preferred fixative for Warthin-Starry is:

A

10% NBF

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24
Q

The “developer” in the Warthin-Starry stain is:

A

hydroquinone

25
Q

Which of the following techniques demonstrates Pneumocystis jirovecci?

a. Grocott
b. Gridley
c. PAS
d. Kinyoun

A

Grocott

26
Q

If fungi are to be demonstrates, a good counterstain for the PAS technique is:

A

light green

27
Q

In the Gridley procedure, the aldehyde fuchsin stain will attach to what reagent?

A

Schiff Reagent

28
Q

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

A

Mayer mucicarmine

29
Q

To differentiate Crytococcus neoformans and other yeast like fungi is that only Crytococcus neoformans has a capsule containing…

A

mucin

30
Q

T/F: Gram-positive organisms cannot be decolorized once stained with crystal violet.

A

False. The decolorization step is a relative one, and sections can be overdecolorized, removing the stain from both Gram-negative and positive organisms.

31
Q

T/F: Gram-positive organisms cannot be decolorized once stained with crystal violet.

A

False. The decolorization step is a relative one, and sections can be overdecolorized, removing the stain from both Gram-negative and positive organisms.

32
Q

T/F: A problem may result from allowing stains to dry during the Gram-staining process.

A

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.

33
Q

T/F: The stains for spirochetes are agyrophil techniques.

A

True.

34
Q

T/F: Rod-shaped bacteria are called bacilli.

A

True

35
Q

T/F: Viral organisms are easily demonstrated with special histochemical stains.

A

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.

36
Q

T/F: A good Grocott methenamine silver stain shows organisms with a crisp black cell wall and a visible internal structure.

A

true

37
Q

T/F: Mercurial fixatives are satisfactory when stains for spirochetes are to be done.

A

False. Avoid mercurial and chromate fixatives. Use 10% NBF.

38
Q

T/F: Tissue containing Helicobacter pylori is a satisfactory control for the Diff-Quick Giemsa modification.

A

True.

39
Q

T/F: The Gridley stain is more intense than the PAS.

A

False.

40
Q

T/F: The mordant is applied after the primary dye in the Gram stain.

A

True

41
Q

T/F: Peanut oil is used in the Ziehl-Neelson method.

A

False. Its used in the Fite methods.

42
Q

T/F: Acid fast stains are satisfactory on tissue used in Carnoy solution.

A

False.

43
Q

T/F: Iodine serves as a mordant in the Gram stain.

A

true

44
Q

T/F: Helicobacter pylori is a spirochete.

A

False. It is a gram-negative bacteria making it cocci.

45
Q

T/F: Helicobacter pylori is readily demonstrated by a Romanowsky-type stain.

A

True (Diff-Quik)

46
Q

T/F: The Giemsa stain will differently stain the different types of bacteria.

A

False. All will stain the same color.

47
Q

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…

A

contamination of the water bath

48
Q

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…

A

backing the section up into acid-alcohol, then recounterstaining removing the coverslip and repeating the entire procedure.

49
Q

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…

A

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.

50
Q

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…

A

Drying of the section during the procedure

51
Q

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

A

Picric acid-acetone. This is the decolorizing step, so it should remove more basic fuchsin.

52
Q

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…

A

Overdifferentiation with picric acid-acetone

53
Q

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…

A

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.

54
Q

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…

A

auramine-rhodamine

55
Q

The control section containing Coccidoidies immitis shows very pale pink-stained organisms on the PAS staine. This is most likely a result of…

A

old or overused reagents

56
Q

The chromic acid keeps turning dark after using it only 2-3 times. This could most likely be corrected in the future by..

A

ensuring the complete removal of alcohol prior to chromic acid. If alcohol isnt completely removed, it will reduce the chromic acid and turn brown.

57
Q

Grocott-stained sections show reticulum and red cells stained black. This most likely is the result of…

A

overimpregnation

58
Q

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

A

ensure that chromic acid is used as the oxidizer. False negatives can be obtained when periodic acid oxidation occurs.

HTL (18 decks)

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