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MCB-L > Simple Stains > Flashcards

Simple Stains Flashcards

1
Q

Chromophore

A

the portion of the stain that gives it a color

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2
Q

Heat fixing

A

process performed on a DRY bacterial smear

bunsen burner or hot plate is used as a heat source & makes the bacterial smear adhere to the slide

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3
Q

Bacterial surface

A

negatively charged

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4
Q

Primary Stain

A

Positively charged

First stain applied in many differential staining techniques & is usually subjected to a decolorizing step that forms the basis for the differential stain

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5
Q

Secondary Stain (counterstain)

A

Negatively charged

stain applied after decolorizing to provide contrast between cells that were decolorized and those that weren’t

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6
Q

Bacteria with capsules

A

Bacillus anthracis, Klebsiella pneumoniae, and Streptococcus pneumoniae

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7
Q

Basic (cationic) stain examples

A

Bacillus anthracis, Klebsiella pneumoniae, and Streptococcus pneumoniae

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8
Q

Endospore outer coating

A

Keratin

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9
Q

Stain used to pick up keratin

A

Malachite green

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10
Q

Mordant

A

a stabilizer that causes the dye to form large crystals that get trapped by the peptidoglycan meshwork of cell wall

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10
Q

Decolorizer

A

removes stain from vegetative cell

used in the gram stain, acid-fast stain, and endospore stain

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10
Q

Mycolic acid

A

waxy substance in cell wall of acid-fast organisms

gives acid-fast cells (1) a higher affinity for the primary stain and (2) resistance to declaration by an acid alcohol solution

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10
Q

Endospore

A

a dormant, highly resistant form of the bacterium that allows it to survive poor environmental conditions

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10
Q

Glycocalyx

A

a polysaccharide coating surrounding some bacteria

capsule - tightly attached

slime layer - loosely attached (advantage of resistance to phagocytosis, increased adherence to surfaces, & decreased dessication)

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10
Q

Basic (cationic) stains

A

use a dye solution in which the chromogen is basic and carries a positive charge (cationic)

attracted to negative charges on the surface of most bacterial cells, as well as nucleic acids, and proteins

applied to bacterial smears that have been heat-fixed

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10
Q

Basic (cationic) dyes

A

crystal violet, methylene blue, carbolfuchsin, safranin, and malachite green

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10
Q

Acidic (anionic) stains

A

use a dye solution in which the chromogen is acidic and carries a negative charge

repelled by negative charge on the surface of most bacterial cells and thus stains the background, not the bacterial cell itself

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10
Q

Acidic (anionic) dyes

A

nigrosin & india ink

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10
Q

Bacterial morphologies

A

Spheres, rods, spirals, and slightly-curved rods

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10
Q

Sphere morphology

A

cocci, singular coccus

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10
Q

Rods morphology

A

bacilli, singular bacillus

11
Q

Spirals morphology

A

spirilla, singular spirillum

12
Q

Slightly-curved rods

A

vibrios

13
Q

Bacterial arrangements

A

diplo, strepto, tetrad, sarcinae, staphylo

14
Q

Diplo arrangement

A

pairs of cells

15
Q

Strepto arrangement

A

chains of cells

16
Q

Tetrad arrangement

A

group of four cells

17
Q

Sarcinae arrangement

A

group of eight cells

18
Q

Staphylo arrangement

A

irregular cluster of cells (grape like clusters)

19
Q

Acid fast stain

A

used to identify bacteria with a waxy cell wall content (mycolic acid)

differential stain - differentiates between Mycobacteria and other types of bacteria

20
Q

Steps of acid fast stain

A

Primary stain - carbolfuchsin (red)
Decolorizer - acid alcohol
Counterstain - methylene blue

21
Q

Acid fast organisms

A

pink/red

e.g. Mycobacterium spp. (M. leprae & M. tuberculosis)

22
Q

Non-acid fast organisms

A

blue

Enterococcus faecium

23
Q

Capsule stain

A

differential stain - identifies bacteria with a polysaccharide coating known as a glycocalyx, or capsule

negative stains background while basic stains colorize the cell, leaving the capsule unstained

24
Q

Capsule stain steps

A

Primary stain - nigrosin or India ink
Counterstain - basic stain (stains cell)

25
Q

Organisms with a capsule…

A

appears the color of basic stain, surrounded by a clear halo against a background color of the acidic stain

26
Q

Endospore stain

A

differential stain - identifies presence and location of spores in bacterial cells

27
Q

Endospores are…

A

highly resistant to heat, chemicals, and staining b/c of tough outer covering made of the protein keratin

metabolically inert or dormant structures produced by the cell when it is stressed (poor environmental conditions or depleted nutrients)

can survive dehydration and then begin to grow when conditions are more favorable

28
Q

Endospore stain steps

A

Primary stain - malachite green (stains spore bc keratin)
Decolorizer - water; removes stain from vegetative & spore mother cell
Counterstain - Safranin (red) ; stains the vegetative & spore mother cell

29
Q

Organisms with endospores….

A

the vegetative and spore mother cell take on the color of the basic stain (pink/red), the endospore is green

30
Q

Bacteria with endospores

A

Bacillus anthracis, Clostridium tetani, C. botulinum, C. perfringens (gas gangrene), C. difficile (pseudo-membranous colitis)

31
Q

Identify endospores

A

Top: central spore
Middle: terminal spore
Bottom: subterminal spores

32
Q

Identify blue and red stains

A

Blue - Enterococcus faecium; non acid fast (-)
Red - Mycobacterium smegmatis; acid fast (+)

33
Q

Identify stain

A

Klebsiella pneumoniae capsule stain

34
Q

Identify stain

A

Bacillus anthracis endospore stain w/ 27 hours incubation period

35
Q

Identify stain

A

Bacillus anthracis endospore stain w/ 48 hour incubation period (more spores)

36
Q

Identify stain

A

Clostridium botulinum endospore stain

sub-terminal, unstained spores

37
Q

Identify species

A

White: Staphylococcus epidermidis
Green: Pseudomonas aeruginosa
Violet: Chromobacterium violaceum
Red/orange: Serratia marcescens
Rose: Kocuria rosea
Yellow: Micrococcus luteus

38
Q

Identify species
1. flat/dry
2. spreading edge
3. crusty/friable
4. transparent

A

Flat/dry: Bacillus spp.
Spreading edge: Alcaligenes faecalis
Crusty/friable: Mycobacterium phlei
Transparent: Lactobacillus plantarum

39
Q

Identify species

A

Enterobacter aerogenes & Citrobacter diversus (motile)

Enterococcus faecalis & Staphylococcus (non-motile, gram positive cocci)

Mycobacterium phlei & Mycobacterium smegmatis (non-motile w/ a waxy cell wall)

40
Q

Identify species

A

Streptococcus species from a throat culture demonstrating flocculence in todd-hewitt broth

41
Q
A

MCB-L (12 decks)

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