EXERCISE 11

Question 1

are required to visualize bacteria adequately and demonstrate the fine detail of internal structures

Answer 1

Biological stains

Question 2

Biological stains are usually derivatives of coal tar with a fundamental structure of

Answer 2

benzene ring

Question 3

Biological stains results in color development when certain chemical radicals have the property of absorbing light of different wavelengths, acting as

Answer 3

chemical prisms

Question 4

Biological stains are usually

Answer 4

ionic

Question 5

positively charged ions

Answer 5

Basic dyes

Question 6

examples of Basic dyes

Answer 6

safranin, basic fuchsin, crystal violet, methylene blue, safranin, malachite green

Question 7

Basic dyes binds best to [?] like nucleic acids, many proteins, and the surface cells of prokaryotic cells (carry a negative charge)

Answer 7

negatively charged molecules

Question 8

negatively charged ions

Answer 8

Acidic dyes

Question 9

examples of Acidic dyes

Answer 9

eosin, acid fuchsin, congo red

Question 10

used to stain animal tissues that microorganisms invade

Answer 10

Acidic dyes

Question 11

Acidic dyes intensify staining by increasing a specimen’s [?] for dye

Answer 11

affinity

Question 12

types of Biological stains

Answer 12

a. Basic dyes

b. Acidic dyes

Question 13

Types of Staining Procedures

Answer 13

1. Simple Stains

2. Differential Stains

Question 14

used to make cells visible with one basic dye

Answer 14

Simple Stains

Question 15

Simple Stains stains cells that

Answer 15

absorb the dye

Question 16

[3] are frequently used in simple staining to determine the size, shape, and arrangement of prokaryotic cells

Answer 16

crystal violet, methylene blue, and carbol fuchsin

Question 17

used to distinguish between types of microorganisms

Answer 17

Differential Stains

Question 18

Differential Stains usually involves 2 stains:

Answer 18

primary staining followed by counterstaining

Question 19

Purpose:
Gram’s stain (Hans Christian Gram- 1884)

a. differentiating [?] bacteria
b. determine the [?] of a particular bacterial sample
c. aids in the [?] of bacteria according to their size, shape, and grouping
d. examination of cultures to [?] and for purpose of identification

Answer 19

a. gram-positive and gram-negative
b. identity
c. identification
d. determine purity

Question 20

The difference in composition between gram-positive cell walls, which contain thick peptidoglycan with numerous [?] cross-linkages, and gram-negative cell walls, which consist of a thinner layer of peptidoglycan, accounts for the Gram staining differences between these two major groups of bacteria.

Answer 20

teichoic acid

Question 21

Gram-positive bacteria the [?] the primary stain because of the extensive teichoic acid cross-links that resist [?] and appear [?].

Answer 21

retain ; alcohol decolorization; blue or purple

Question 22

Gram-negative bacteria [?] the primary stain during decolorization, take up the [?] and appear [?].

Answer 22

lose; counterstain; pink or red

Question 23

Crystal violet –

Answer 23

primary stain

Question 24

Gram’s iodine -

Answer 24

mordant

Question 25

Decolorizer -

Answer 25

decolorizer

Question 26

Safranin –

Answer 26

secondary stain

Question 27

Gram-stained clinical material is evaluated for:

• the [?] of bacterial cells (rare, few, moderate, many)
• the presence of bacterial cells as well as the [?] (Grampositive or Gram-negative), [?] (cocci, bacilli, coccobacilli), and [?] (chains, pairs, clusters) of the cells observed
• the presence of [? and ?]

Answer 27

• relative amounts
• Gram reaction; morphologies ; arrangements
• host cells and debris

Question 28

to visualize bacterial cells by light microscopy a minimum concentration of 105 cells per mL of the specimen is required

Answer 28

the relative amounts of bacterial cells

Question 29

correlate smear results with the amount of growth observed subsequently from culture

Answer 29

the relative amounts of bacterial cells

Question 30

fungal cells and elements generally stain Gram-positive, but they may take up the crystal violet poorly and appear Gram-variable or Gram-positive

Answer 30

the presence of bacterial cells as well as the Gram reaction, morphologies, and arrangements of the cells observed

Question 31

Host cells (RBC and WBC) allow the crystal violet to wash out during decolorization and therefore appear pink on smear

Answer 31

the presence of host cells and debris

Question 32

the squamous epithelial cell in the respiratory specimen may indicate contamination with organisms and cells in the mouth

Answer 32

the presence of host cells and debris

Question 33

background tissue debris and proteinaceous material indicates that specimen material was adequately affixed thus the absence of bacteria is “real” and not likely the loss of the specimen during staining

Answer 33

the presence of host cells and debris

Question 34

All cooci are Gram positive bacteria, except [3]

Answer 34

Neisseria, Veilonella, Branhamella

Question 35

All bacilli are Gram negative bacteria, except [7]

Answer 35

Corynebacterium, Clostridium, Bacillus, Listeria, Erysipelotrix, Lactobacillus, Mycobacterium

Question 36

Limitations: Cannot detect microorganisms
• that exist almost exclusively within [?] (e.g., chlamydia)
• that lack [?] (e.g., mycoplasma and ureaplasma)
• of [?] to be resolved by light microscopy (e.g., spirochetes)

Answer 36

• host cells
• cell wall
• insufficient dimension

Question 37

Reasons for Loss of Gram-positive Cell Wall Integrity
• antibiotic treatment
• old age
• action of autolytic enzyme

may allow the [?] to wash out with the decolorizing step and may appear [?] , with some cells staining pink and other staining purple

Answer 37

crystal violet; gram-variable