7.1: GRAM STAINING METHOD

Question 1

who invented gram staining method? developed when?

Answer 1

Christian Gram; 1884

Question 2

crystal violet

Answer 2

hexamethyl-p-rosanaline chloride

Question 3

function of crystal violet

Answer 3

color all cells and background material deep blue

Question 4

function of Gram’s iodine

Answer 4

large iodine material REPLACE smaller chloride in stain molecule

Question 5

bacteria thick celled walles contain

Answer 5

teichoic acid

Question 6

gram-positive bacteria retain what dye complex?

Answer 6

crystal violet-iodine dye complex

Question 7

bacteria w thin celled walls contains

Answer 7

lipopolysaccharides

Question 8

this decolorizer damages thin lipid walls and allows the stain complex to wash out

Answer 8

alcohol-acetone decolorizer

Question 9

unstained elements are counterstained RED by

Answer 9

safranin dye

Question 10

differential ability of gram stain makes it useful for

Answer 10

microbial taxonomy

Question 11

gram stain is used routinely forbthe primary micicroscopic examinatioj of specimens submitted for

Answer 11

smear and culture

Question 12

gram staining is used when - infection is strongly suspected

Answer 12

bacterial infections

Question 13

ex. routinely stained directly

Answer 13

CSF SWEEB

• Cerebrospinal Fluid (CSF)
• Sterile fluid
• Wounds
• Exudates
• Expectorated sputum
• Bronchoalveolar lavages

Question 14

ex. routinely stained NOT directly

Answer 14

urine and stool

Question 15

samples sent for — are usually NOT STAINED

Answer 15

focused screening cultures

Question 16

gram stain is used to characterize

Answer 16

bacteria growing on culture media

Question 17

adherence can be improved by (2 ways)

Answer 17

• fixation in 70-95% alcohol
• warming the slide to remove all water from the material

Question 18

examine stained smear using

Answer 18

• low power objective

Question 19

stained smear is examined closely using

Answer 19

40-60 oil objective

Question 20

suspicious areas of stained smear are evaluated using

Answer 20

100 oil objective

Question 21

gram (+) stain

Answer 21

deep blue to blue black

Question 22

gram (-) stain [other elements]

Answer 22

safranin red

Question 23

individual structures absorb diff amounts of safranin- so they can be described as either

Answer 23

• prominent staining (strong avidity)
• weakly stained (low avidity)

Question 24

gram negative: enteric

Answer 24

strong avidity, stain bright red

Question 25

gram negative: pseudomonads

Answer 25

less avid, stain moderately well

Question 26

thin walled gram-negative organisms taht are stained WEAKLY

Answer 26

LABS

• Legionella spp.
• Anaerobic bacilli
• Borrelia spp.
• Spirilum spp.

Question 27

used to wash away the crystal violet (no water rinse)

Answer 27

dilute iodine solution

Question 28

a more rapid decolorizer

Answer 28

acetone

Question 29

used to decolorize the slide

Answer 29

acetone or absolute alcohol (or mixture of both)

Question 30

anaerobes stain better w

Answer 30

dilute carbolfuchsin (1 min)

Question 31

anaerobes is flooded w — for 30 sec to 1 min

Answer 31

safranin
dilute carbolfuchsin
neutral red

Question 32

most commonly used stain in the clin microbiology lab

Answer 32

gram stain

Question 33

2 main groups of bacteria

Answer 33

gram positive (blue to purple)
gram negative (pink)

Question 34

determines the gram-staining characteristics if a specis

Answer 34

cell wall structure

Question 35

4 sequential components

Answer 35

-crystal violet (primary stain,1 min)
-iodine (mordant or fixative, 1 min)
-alcohol or alcohol acetone sol. (decolorizer quick on then rinse)
-safranin (counterstain 30 sec)

Question 36

used for rinsing between each sequential step

Answer 36

water

Question 37

cells in direct smear that appear pink (gram negative)

Answer 37

Epithelial cells
WBC
RBC
Amorphous background material

Question 38

cells in direct smear that appear pink (gram negative)

Answer 38

Epithelial cells
WBC
RBC
Amorphous