Deck 6: Role of Microscopy

Question 1

Which of the following statements is true concerning dark-field microscopy?

A)This type of microscopy uses specific stains to enhance the contrast of certain bacteria.
B)The condenser does not allow light to pass directly through the specimen but directs the light to hit the specimen at an oblique angle.
C)Dark-field microscopy allows the visualization of larger viruses.
D)Dark-field microscopy can differentiate various difficult-to-grow organisms by using immunofluorescence.

Answer 1

B
Dark-field microscopy does not allow light to pass directly through the specimen but directs light to hit at an oblique angle thus making the background a dark field.

Question 2

The fluorochrome stain used to study a fungus is:

A)calcofluor white.
B)acridine orange.
C)auramine.
D)immunofluorescence.

Answer 2

A
The cell walls of a fungus will bind calcofluor white.

Question 3

After which step in the Gram-stain procedure are gram-positive bacteria first distinguished from gram-negative bacteria?

A)Crystal violet
B)Iodine mordant
C)Gram's decolorizer
D)Safranin

Answer 3

C
Up until the decolorizer step,all bacteria and cells appear the same during the Gram-stain procedure.

Question 4

A mordant that is applied after the primary stain to bond chemically the alkaline dye to the bacterial cell wall is:

A)safranin.
B)crystal violet.
C)Gram's iodine.
D)Gram's decolorizer.

Question 5

The acid-fast stain is specifically designed for bacteria whose cell walls contain:

A)teichoic acids.
B)mycolic acids.
C)peptidoglycan.
D)disaccharide-pentapeptide subunits.

Question 6

Of the different types of staining and microscopic techniques,which one of the following is basically the most sensitive?

A)Chromogenic
B)Fluorescence
C)Phase contrast
D)Light field

Question 7

The fluorochrome stain that can be used to detect mycobacteria is:

A)calcofluor white.
B)acridine orange.
C)auramine.
D)immunofluorescence.

Question 8

When processing a culture swab in the diagnostic laboratory the microbiologist should:

A)inoculate the media prior to making the direct smear.
B)roll the swab back and forth on the slide making sure to transfer organisms.
C)prepare the smear by rubbing the slide with one side of the swab and utilize the opposite slide to inoculate media.
D)cancel the direct Gram stain and only set up the media.Request a second swab for the direct smear.

Question 9

In microscopy,resolution can be defined as the:

A)magnification power.
B)extent to which detail in the magnified object is maintained.
C)ability of objects to stand out from the background.
D)ability to see objects against a black background.

Question 10

The limitation associated with utilizing the Gram stain procedure includes all of the following except:

A)over decolorizing resulting in all organisms appearing gram negative.
B)formation of crystals in the stain appearing as gram-positive rods.
C)providing potential life-saving preliminary organism characteristics.
D)variable Gram staining characteristics based on organism viability in preparation.

Question 11

When assessing the quality of a direct Gram stain,neutrophils should appear as:

A)cells with pink cytoplasm and darker more purplish nuclear lobes.
B)cells with pink cytoplasm and pink nuclear lobes.
C)cells with purple cytoplasm and pink nuclear lobes.
D)cells with purple cytoplasm and purple nuclear lobes.

Question 12

When preparing a smear from a viscous and granular sample the microbiologist should:

A)add saline to the sample to thin out the specimen for smear preparation.
B)place some of the material in an enrichment broth and then use the broth for smear preparation.
C)use a sterile swab and roll it around in the material because it will be easier to roll the sample than to use a loop on the slide.
D)if the material is not able to be distributed using a sterile loop or swab,use a squash or crush prep to spread out sample.

Question 13

In the Kinyoun acid-fast staining method,______ replaces _____ in the primary stain solution.

A)increased phenol;heat
B)heat;increased phenol
C)mycolic acid;heat
D)carbolfuchsin;phenol

Question 14

Contrast in microscopy is most commonly achieved by:

A)changing objectives for various specimens.
B)increasing the resolution or resolving power.
C)staining techniques.
D)adding a blue filter to the light path.

Question 15

An organism such as Mycobacterium tuberculosis would absorb which stain in its cell wall?

A)Crystal violet
B)Methylene blue
C)Carbolfuchsin
D)Malachite green

Question 16

The first step in the Gram-stain sequence is the application of _______,which is the primary stain.

A)safranin
B)crystal violet
C)Gram's iodine
D)Gram's decolorizer

Question 17

The most critical step in the Gram stain is the application of the:

A)safranin.
B)crystal violet.
C)Gram's iodine.
D)Gram's decolorizer.

Question 18

Magnifications in excess of 100,000 times are achieved by ________ microscopy?

A)bright-field
B)electron
C)dark-field
D)phase-contrast

Question 19

The value of indirect Gram staining from a broth culture in comparison to a agar plate culture is:

A)there is no significant difference in the results of the indirect smear technique.
B)organisms tend to demonstrate natural cell shape and arrangement in liquid medium.
C)organisms tend to demonstrate more growth and easier visualization from agar plates.
D)none of the answers are correct.

Question 20

Bacterial cells with thick peptidoglycan and numerous teichoic acid cross-linkages are Gram stained.The organisms stain pink.Which one of the following statements explains this discrepancy?

A)The bacterial cells were most likely not heat-fixed to the slide.
B)The bacterial cells were subjected to the decolorizer too long and were overdecolorized.
C)The lot of Gram-stain reagent is most likely expired.
D)No discrepancy exists;cells with this composition stain pink on Gram stain.

Question 21

When reporting a direct smear from a primary specimen,it is important to note the presence and quantity of white blood cells even in the absence of bacteria for all of the following reasons except:

A)the pathogen may not be present in sufficient quantities.
B)the presence of white blood cells indicates a purulent process.
C)the pathogen may not be present in the sample collected.
D)it is not important to report white blood cells unless bacteria are present.

Question 22

It is important to differentiate white blood cells in a preliminary direct smear because

A)the type of white blood cell present definitively indicates whether or not an infection is bacterial.
B)neutrophils are the only white blood cell present during bacterial infections.
C)it is not appropriate,because various types of white blood cells are indicative of different bacterial infections.
D)white blood cells are not noted on preliminary direct smear results.

Question 23

Gram-positive cocci in clusters were reported on preliminary direct Gram staining from a sputum specimen.The patient was treated with antibiotics.Following 48 hours of treatment,a secondary specimen was reported as gram-positive rods.The discrepancy in this result is:

A)the patient likely obtained a secondary infection following treatment of the first pathogen.
B)the antibiotics are effective and the gram-positive cocci are distorted due to inhibition of growth by the antibiotic.
C)the first preliminary Gram stain was erroneous,and should have been reported as normal microbiota.
D)there is no discrepancy.

Question 24

When reporting a direct smear from a primary specimen,it is important to note all of the following except:

A)white blood cells.
B)squamous epithelial cells.
C)artifacts.
D)prominent cell shapes and arrangements.