Role of Microscopy

Question 1

A fluorescent dye coupled with specific antibodies is called:

a. Immunofluorescence
b. Flourochroming
c. Acridine orange
d. Electron microscopy

Answer 1

a. Immunofluorescence

Question 2

The stain that binds to the nucleic acid of organisms but does not discriminate between gram-positive or gram-negative organisms is called:

a. Ziehl-Neelsen stain
b. Auramine-rhodamine stain
c. Gram stain
d. Acridine orange stain

Answer 2

d. Acridine orange stain

Question 3

The step in the Gram stain process that distinguishes between gram-positive and gram-negative organisms is:

a. Fixing of the cells to the slide using heat or methanol
b. Decolorization using alcohol or acetone
c. Counterstain of the Gram stain using safranin
d. Application of the mordant, Gram’s iodine

Answer 3

b. Decolorization using alcohol or acetone

Question 4

Dark-field microcopy is used for the microscopic examination of these types of bacteria:

a. Gram-positive cocci such as S. aureus
b. Yeast such as Candida tropicalis
c. Gram-negative bacilli such as E. coli
d. Spirochetes such as Trepnema palllidum

Answer 4

d. Spirochetes such as Trepnema pallidum

Question 5

The ocular lens is the lens closest to the specimen. True or false

Answer 5

False

Question 6

T/F:

Resolution is the extent at which detail in a magnified image is defined.

Answer 6

True

Question 7

T/F:

Fungi stain gram-negative

Answer 7

False

Question 8

T/F:

Acid-fast bacteria are resistant to decolonization

Answer 8

True

Question 9

T/F:

A fluorescent dye coupled with specific antibodies is called fluorochroming.

Answer 9

False

Question 10

principle stain used for microscopic bacteria examination

Answer 10

Gram stain

Question 11

stain used to detect fungi in clinical material

Answer 11

calcofluor white

Question 12

Gram staining of clinical material

Answer 12

direct smear

Question 13

primary stain in the classic acid-fast stain

Answer 13

carbolfuchsin

Question 14

“hot” method of acid-fast stain

Answer 14

Ziehl-Neelsen

Question 15

counterstain in the Gram stain

Answer 15

safranin

Question 16

mordant that forms the intracellular complex

Answer 16

Gram’s iodine

Question 17

primary stain of the Gram stain

Answer 17

crystal violet

Question 18

focuses light path for proper resolution

Answer 18

Kohler illumination

Question 19

How is contrast achieved in light microscopy?

Answer 19

as a result of the interaction between illuminating light wavefronts and the specimen, and how the light leaving the specimen is processed,

Question 20

Calculate the total viewing magnification of an object when using the 40x objective lens

Answer 20

10 x 40 = 400x

Question 21

What two methods of microscopy are most widely used in clinical laboratories?

Answer 21

Bright field and fluorescent microscopy

Question 22

For what reason would the gram stain of a specimen stain gram-variable. and how should that gram stain be reported?

Answer 22

Gram-positive organisms that have lost cell wall integrity as a result of antibiotic treatment, old age, or other reasons will decolorize, report as gram-positive.

Question 23

An indirect smear from a blood agar plate was gram stained and reported as “gram -positive cocci in clusters.” However, the gram stain of the thioglycollate broth demonstrated gram-positive cocci in chains. How would the microbiologist resolve this discrepancy, and what should be reported?

Answer 23

The smears prepared from each media are the same organism. When preparing a smear from solid media, it is important to make the smear is thin enough and to look to the outer edges to find the true morphologic characteristics and arrangement; all organisms tend to clump together when improperly emulsified. The broth culture allows the microbiologist to view organisms in their native states, including correct cellular morphologic characteristics and arrangement, they are not clumped together but are free floating in the liquid medium.