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Micro Lab Study Cards > Lab #3 > Flashcards

Lab #3 Flashcards

(45 cards)

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1
Q

G (-) Enteric Bacilli

A 
Escherichia coli
Enterobacter cloacae
Klebsiella pneumoniae
Pseudomonas aeruginosa
Proteus vulgaris
Proteus mirabilis
Shigella flexneri
Salmonella enterica
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2
Q

MacConkey test

A

Both differential & selective
Selective for: G (-)
Selective against: G(+)
Differential based on lactose fermentation

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3
Q

MacConkey

What compounds in the medium inhibit certain bacteria (make it selective)?

A

crystal violet dye

bile salt tolerance

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4
Q

MacConkey
How is medium differential?

Medium differentiates between what 2 groups of G (-) bacilli?

A

lactose fermentation

lactose fermenters & lactose non-fermenters

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5
Q

MacConkey

What is the name of the pH indicator in the medium?

A

neutral red
CLEAR when pH is neutral
HOT PINK when pH is acidic

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6
Q

MacConkey

  1. How do lactose-fermenting colonies appear on this medium?
  2. How do lactose-nonfermenting colonies appear on this medium?
A
  1. pink

2. colorless/translucent

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7
Q

What does EMB stand for?

A

Eosin Methylene Blue (Agar)

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8
Q

EMB (agar)

Is this media selective, differential, or both?

A

Both
Selective for: G (-) bacteria
Selective against: G (+)

Differential based on lactose fermentation (inhibitory to G(+)

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9
Q

EMB

What compounds in the medium inhibit certain bacteria (what makes it selective)?

A

bile salt tolerance
methylene blue
eosin dyes

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10
Q

EMB

This media differentiates between what 2 groups of bacteria?

A

G (-) and G (+)

MacConkey is preferred over EMB, though, as it inhibits the swarming of Proteus.

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11
Q

EMB

How do E. coli colonies appear on this media?

A

greenish metallic sheen (so is used to confirm if IMVic results are inconclusive)

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12
Q

Phenol Red Broth

selective, differential or both?

A

Differential

Based on sugar fermentation

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13
Q

Is sugar fermentation anaerobic or aerobic?

A

aerobic

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14
Q

Phenol Red Broth

What 2 end products of fermentation are we testing for with this medium?

A

acid & gas

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15
Q

Phenol Red Broth

What 3 sugars are used in this medium?

A

sucrose
glucose
lactose

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16
Q

Phenol Red Broth

What is the purpose of the Durham tube?

A

serve as gas traps for collecting bubbles generated by gas-producing microbes

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17
Q

Phenol Red Broth

What is the name of the pH indicator used in this medium?

A

phenol red

RED when pH is neutral
YELLOW when pH is acidic

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18
Q

Phenol Red Broth

How is sugar fermentation observed?

A

air is trapped in the Durham tube

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19
Q

What does TSI stand for?

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A

Triple Sugar Iron

20
Q

TSI

selective, differential or both?

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A

differential
Differential in 2 ways:
1. sugar fermentation (sucrose, lactose, glucose)
2. sulfur reduction

21
Q

TSI

This medium is used to differentiate what group of bacteria?

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A

lactose nonfermenters

22
Q

Lactose fermenters

Study These Flashcards
A

EEK
Esherichia coli
Enterobacter cloacae
Klebsiella pneumoniae

23
Q

Lactose nonfermenters

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A 
P3S2 (P cubed, S squared)
Proteus vulgaris
Proteus mirabilis
Pseudomonas aeruginosa
Shigella flexneri
Salmonella enterica
24
Q

TSI

What is the name of the pH indicator in the medium?

25
TSI | How is sugar fermentation observed?
turns yellow
26
TSI | black precipitate
Some bacteria reduces sulfates in the process of anaerobic respiration (sulfates can serve as the final electron acceptor in electron transport chain). These bacteria are "sulfur reducers." Sulfate is reduced to H2S (hydrogen sulfate) Combines with an iron indicator in the medium to produce a black precipitate in the butt of the tube (the anaerobic part of the tube).
27
TSI | red slant/yellow butt; black precipitate
``` glucose fermented (only one sugar) = red/yellow sulfur reduced = black precipitate ``` Salmonella enterica Proteus mirabilis
28
TSI | yellow/yellow; black precipitate
2 sugars fermented = glucose & sucrose = yellow/yellow sulfur reduced = black precipitate Proteus vulgaris
29
TSI | red/red; no black ppt
no sugar fermented = red/red no sulfur reduced = no black Pseudomonas aeruginosa
30
TSI | red slant/yellow butt; no black ppt.
one sugar fermented (glucose) = yellow butt no sulfur reduced = no black Shigella flexneri
31
TSI | yellow/yellow; no black ppt
2 sugars fermented (glucose & sucrose) = yellow/yellow no sulfur reduced = no black Escherichia coli
32
What does IMViC stand for?
Indole (tryptone broth) Methyl Red Voges-Proskauer Citrate
33
IMViC test | selective or differential or both?
differential differentiates bacteria in EEK group (lactose fermenters) Escherichia coli Enterbacter cloacae Klebsiella pneumoniae
34
IMViC results for: | Escherichia coli
+ + - -
35
IMViC results for: Kebsiella pneumoniae Enterobacter cloacae
- - + +
36
IMViC | Indole test
- uses tryptone broth, which contains tryptonphan - Tryptophan is an amino acid - Bacteria metabolizes tryptophan into pyruvic acid - add chemical agent (Kovac's) after incubation + = pink ring - = yellow ring
37
IMViC | Methyl Red test (MR) - use MRVP broth
- differential based on fermentation of glucose into multiple acids - pH indicator added after incubation = methyl red ``` + = red when pH is acidic - = yellow when pH is alkaline (basic) ```
38
IMViC | Voges Proskauer test (VP)
- differential based on a type of alcoholic fermentation - after incubation, 2 reagents are added: Barritt's A Barritt's B + = pink/rose/red - = clear VP results should always be opposite of MR results.
39
IMViC | Citrate test
- differential based on utilization of citrate as the sole source of carbon - medium is GREEN prior to inoculation - pH indicator = BROMTHYMOL BLUE - indicator changes from green to blue if alkaline/basic ``` + = blue (presence of a base) - = stays green ```
40
If IMViC is - - + +, what is next test?
Ornithine Decarboxylase test
41
If IMViC is + + - -, what is the next test?
None. You know it's Escherichia coli | Confirm with EMB (Eosin Methylene Blue) - get shiny, greenish metallic sheen
42
Urea Hydrolysis test
- differential for hydrolysis of urea - differentiates between Salmonella enterica & Proteus mirabilis - common characteristics: - G(-) - bacilli - lactose NONfermenters - ferment glucose - ferment sucrose - do no reduce sulfur - found in the colon
43
Ornithine Decarboxylation test | Differentiates between which two bacteria?
- differentiates Enterobactoer cloacae & Klebsiella pneumonia AND Proteus mirabilis & Proteus vulgaris - Characteristics shared: - G(-) - bacilli - Lactose fermenters - IMViC results = - - + + - found in colon
44
Urea Hydrolysis test
- chemical reaction = urea -> ammonia + CO2 - looking for ammonia (end product), which is alkaline (basic) - enzyme produced by the bacteria to hydrolyze urea = UREASE - pH indicator = PHENOL RED ``` + = hot pink / basic (alkaline) [Proteus mirabilis] - = salmon / acidic [Salmonella enterica] ```
45
Ornithine Decarboxylation test | selective, differential or both?`
Differential based on ornithine decarboxylation

Micro Lab Study Cards (2 decks)

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