Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

medical science > Unit 5 :staining techniques > Flashcards

Unit 5 :staining techniques Flashcards

You may prefer our related Brainscape-certified flashcards:
USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

what are the 2 main differential groups in principle of Gram stain

A

Gram-positive and Gram-negative

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is the difference between Gram-positive and Gram-negative organisms in terms of cell wall

A

Gram-positive =thicker cell wall with more peptidoglycan and

Gram-negative = additional outter membrane instead of thick cell wall,

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what separates the cell wall and the outer membrane of the Gram-negative organisms

A

periplasmic space

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

which species of microorganisms do Gram stain stain for

A

bacteria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

list the 4 steps involved in Gram staining

A

1.primary stain (crystal violet)
2.trapping agent (Gram’s Iodine)
3.rapid decolourisation (alcohol/acetone)
4.counterstaining (safranin)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

explain what crystal violet does to both Gram-positive and Gram-negative cells and the colour change

A

-crystal violet penetrates through cell walls & cell membranes of both Gram-positive and Gram-negative cells

-stains cells purple

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what does Iodine do

A

reacts with crystal violet to form large crystal-iodine complexes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what does alcohol/acetone do

A

alcohol reacts with the lipids of the cell membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what are the different reactions from Gram-positive and Gram-negative cells to decolorization by alcohol

A

Gram-negative cells lose their outer membrane along with the crystal-iodine large complexes
(they are washed away)

Gram-positive cells become dehydrated and the large iodine-crystal violet large complexes become trapped within the multi-layered peptidoglycan cell wall

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is the colour status of Gram-negative and Gram-positive cells after decolorization by alcohol

A

Gram-positive - retain purple colour

Gram-negative -lose their purple colour

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

after counterstaining by safranin, what is the colour status

A

Gram-negative - pink-red colour

Gram-positive -purple colour

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what are the results expected for Gram stain as per principle

A

Gram-positive = purple

Gram-negative = reddish pink

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Now give the Gram’s stain principle, process, reaction and expected results off by heart

A

Principle : it differentiates bacteria into Gram-positive (thicker cell wall) and Gram-negative (thin cell wall with an additional outer membrane) based on their cell wall.

Process :
-Primary stain by Crystal violet stains both Gram-positive and Gram-negative cells purple.
-Trapping agent, Gram’s Iodine reacts with Crystal Iodine to form large crystal-Iodine complexes in both Gram-positive and Gram-negative cells
-Decolorization by alcohol/acetone washes away the additional outer membrane + large complexes in Gram-negative cells and dehydrates the Gram-positive cells and results in large complexes being trapped in the multi-layered peptidoglycan cell wall. Gram- negative cells lose their purple colour and Gram-positive cells retain their purple colour.
-Counterstaining by Safranin gives the Gram-negative a reddish pink colour while Gram-positive cells remain puple.

Expected results :
Gram-positive =purple
Gram-negative =reddish pink

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

give 4 examples of gram-positive organisms.

A

Streptococcus
Staphylococcus
Bacillus
Clostridium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

2 examples of gram-negative organisms

A

Proteus
Neiserria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is the principle for the ziehl-Neelson staining technique

A

it differentiates acid-fast organisms and non-acid-fast bacilllus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what is meant by Acid-fastness

A

physical property of bacteria to resist decolorisation by acids during staining procedures.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what does a decolorizer do

A

it dehydrates and rinses out

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what are the 3 reagents used in Ziehl-neelson staining technique

A

Ziehl-Neelson carbolfuchsin
acid alcohol
methylene blue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what 2 pre-steps are required before attempting to penetrate high lipid cell walled mycobacteria such as bacillus

A

phenol (which is lipid soluble)
heat application (melts the wax)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what step follows addition of phenol and heat application to bacillus

A

primary staining by Ziehl-Neelson Carbolfuchsin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what step, and what is acid alcohol used for

A

step3 for decolorization

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

how does bacillus react to decolorisation by acid alcohol

A

Acid-fast bacillus withstands and it retains the Ziehl-Neelson carbolfuchsin stain and non-acid-fast bacillus doesnt.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what is the last step and what is the expected colour change

A

counterstaining with malachite green or methylene blue.

expected colour change:
acid-fast bacilli - red
non-acid- fast organisms & cells - green or blue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

give 1 example of acid-fast bacillus

A

mycobacterium tuberculosis

26
Q

state the principle, 3steps and expected colour change involved in Ziehl-Neelson staining technique

A

principle: it differentiates bacilli into acid-fast and non-acid fast organisms.

  1. heat application (to melt wax) and phenol application (for lipid-dense cell wall)
  2. primary staining with Ziehl-Neelson carbolfuchsin and both acid-fast and non-acid fast stain red.
  3. decolorization with acid alcohol results in acid-fast bacilli retaining their red colour and non-acid fast organisms and cells being decolorized.
  4. counterstaining with malachite green or methylene blue

Expected colour change
acid-fast bacilli: red
background, non-acid fast organisms or cells: green or blue

27
Q

what 2 methods are used to stain endospores

A

ziehl-neelson stain and malachite green stain for spores

28
Q

why do we say endospores tend to resemble acid-fast behaviour

A

when bacilli is stained with ordinary dye or with Gram stain it stains deeply but its endospores resist ( due to their thick resistant spore coat) the dye and appear as a clear area in the organism.

and when stained endospores tend to retain the dye even after decolorization thus acting like an Acid-fast organism

29
Q

what makes the Ziehl-neelson staining be able to stain endospores while ordinary stains cant, what is it that it has that enables this, what makes it special

A

the ziehl-neelson primary stain (ziehl-neelson carbolfuchsin) contains phenol which softens the protein coat and the application of heat helps drive the stain into the endospore

30
Q

what is used as a decolorizer in the Ziehl-neelson staining of endospores

A

2% nitric acid in absolute ethanol

31
Q

what are the expected results from the malachite green and the ziehl-neelson staining of endospores

A

ziehl-neelson stain:
spores-bright red
cytoplam or rest of the cell-blue

32
Q
A
33
Q

what are the 3 steps involved in malachite green staining of endospores

A

1.primary stain is malachite green which stains the entires cell and spores green
2.heat is used to force the stain into the spores
3. primary stain washed away from cell wall with water but retained in the endospore wall
4.counterstain staining with safranin to stain the vegetative cell/cytoplasm

34
Q

does the dye bind the same way on the vegetative cell as it binds to the endospore wall

A

no. it binds relatively weakly to the vegetative cell wall and is removed when washed with water while it is locked in in the spore.

35
Q

what are the malachite expected results

A

spore: green
vegetative cells/cytoplasm : red
and lipid granules are unstained

36
Q

describe the shape of the following types of bacteria

  1. cocci
    2.bacilli
    3.vibrio
    4.spirillum
    5.spirochete
A
  1. cocci- spherical/oval
    2.bacilli-straight rod shaped
    3.vibrio - curved rod shaped
    4/5. spirilla- spirally twisted
37
Q

how would you identify the following types of cocci

1.diplococci
2.strepococci
3.staphylococci
4.micrococci
5. sarcina

A

1.diplococci- paired cocci (spherical)
2.strepococci -chains
3.staphylococci-irregular clusters
4.micrococci- groups of 4 cocci
5. sarcina- cubical packets of 8 cocci

38
Q

how would you describe the following types of Bacilli
1.coccobacilli
2.bacilli
3.palisades
4.diplobacilli
5.streptobacilli

A

1.coccobacilli- short rods approaching coccus shape
2.bacilli- 1 bacillus cell
3.palisades-group of vertical bacilli
4.diplobacilli-2 bacilli connected together
5.streptobacilli- chain of bacilli

39
Q

difference between spirochaetes and spirilla bacilli

A

spirochaetes are flexious and are motile without a flagella

40
Q

are yeasts unicellular or multicellular and how would you describe their shape

A

unicellular fungi
oval or spherical single cells

41
Q

how do yeats reproduce

A

by asexual reproduction called budding producing blastospores

42
Q

are yeasts Gram+ or Gram-

A

gram+

43
Q

draw a unicellular yeast, budding yeast, unicellar yeast next to a blastospore

A

answer on workbook

44
Q

how would you define/describe yeast-like fungi

A

they grow partly as yeasts partly as long filamentous cells joined end to end, forming pseudo-mycelium

45
Q

what are thick-walled resting spores of yeast-like fungi called

A

chlamydospores

46
Q

give an example of yeast-like fungi

A

candida albicans

47
Q

what is hypha

A

the connection between 2 yeast-like fungi as they are joined together end to end

48
Q

how would you describe true-fungi

A

1.they grow as long filaments or hyphae which branch and interface to form mycelium.

2.they reproduce by spores

3.vegetative mycelium- penetrates into substrate, absorbing nutrients for growth

4.aerial mycelium protrude from the vegetative mycelium into the air, form and release spores

49
Q

how does dimorphic fungi grow
at 37degrees and at 22degrees and which of the 2 temperatures is favourable and which one is unfavourable

A

37degrees in the body (favourable) -yeasts (oval or spherical)

22degrees in artificial media (unfavourable)- moulds (long filaments)

50
Q

go to notes (unit 5, last page) and label the different types of spores

A

answer on notes

51
Q

when preparing a dry smear, you need to leave the sample on the glass slide to dry for a few minutes before continuing with the experiment, explain why you cant speed up this process by blowing or heating

A

by blowing we will be forcing the bacteria into the air and this will contaminate and cause a possible infection

52
Q

explain heat-fixing

A

heat fixing is passing a tilted and dried slide 2-3 times over a heat to make the bacteria to stick to the slide.

53
Q

what do we use to stain mycobacterium tuberculosis

A

ziehl-neelson stain

54
Q

define an acid-fast organism

A

an organism that has a waxy layer covering their cell wall and thus resists decolourization by acids

55
Q

which staining technique is used for acid-fast bacteria (the ones that resist decolourization by alcohol or acids)

A

ziehl-neelson technique

56
Q

whats that thing thats used to provide a flame in heat fixing process and what is used to pick a smear from the broth or agar

A

bunsen burner

wire loop

57
Q

what colour is the acid fast bacteria

A

background : blue and mycobacterium tuberculosis : red/purple bacilli

58
Q

(ngwaneso just cram) what colour does phenol red change to when bacteria has fermented an acidic glucose

A

yellow

59
Q

if bacteria didnt ferment carbohydrate what is the colour change and how do we know if gas is produced

A

it remains red

the tube will have a bubble

60
Q

which bacterial organism is a good example of bacteria that has endospores and which stain is used to stain the endospores

A

bacterium cereus

ziehl-neelson stain and malachite green

61
Q

what is the staining reaction and the organism shape

A

Ziehl-neelson stain: blue vegetative organism and red endospores
Malachite green stain: red vegetative organism and green endospores …

…which are bacilli in shape

medical science (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions