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Microbiology > Microbiology- Lab Practical #2 (7/18/13 lab) > Flashcards

Microbiology- Lab Practical #2 (7/18/13 lab) Flashcards

Esculin Iron Agar EMB (Eosin Methylene Blue Agar) Hektoen enteric agar antimicrobial susceptibility Test

1
Q

Hydrolysis is?

A

Reactions that use water to split complex molecules

hydrolytic

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2
Q

What type of enzyme are required for hydrolysis?

Identify the two types that exist.

A

Hydrolytic enzymes

Intracellular( catalyzes rxn inside the cell)
Extracellular (catalyzes rxn outside of cell- exoenzymes)

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3
Q

Enzymes for hydrolysis are secreted from where?

A

From the organism in need of the reaction

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4
Q

For the Bile Esculin and Urea Test are type of enzymes are detected?

A

Intracellular

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5
Q

What takes place in the medium of a Bile Esculin and Urea Test ?

A

There ia clear color change in the medium

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6
Q

Nutrients Gelatin is to….. (detects)

A

…Gelatinase (exoenzyme)

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7
Q

What is gelatinase?

A

an exoenzyme that liquifies the solid medium`

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8
Q

Plated media used to identify extracellular enzymes

A

DNase Agar, Milk Agar, Tributyrin Agar, and Starch Agar.

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9
Q

DNase Agar, Milk Agar, Tributyrin Agar, and Starch Agar are identified by….

A

halo that develops around bacterial growth subsequent to hydrolysis

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10
Q

Bile Esculin agar is defined. (T/F)

A

False. It is undefined

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11
Q

Bile Esculin agar is selective media. (T/F)

A

True. :)

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12
Q

Bile Esculin agar is differential or not?(Justify to yourself why/why not)

A

Differntial because it allows for differentiation by pressence of a black precipitate

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13
Q

Bile Esculin is composed of …

A

beef extract, digest of gelatin
esculin,
oxgall (bile),
and ferric citrate

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14
Q

What is the purpose of beef extract, digest of gelatin in Esculin agar?

A

nutrient and energy

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15
Q

Bile in Esculin agar is the …

A

Selective agent:

separates S. bovis & enterococci from streptococci

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16
Q

Ferric citrate in Esculin agar is the ?

A

oxidized iron source to indiate positive test

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17
Q

Gram-positive shows tolerance to bile (T/F)

A

False. Gram-negative enterics do.

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18
Q

Under what circumstances will bacteria hydrolyze esculin?

A

acidic conditions

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19
Q

They tolerate bile and hydrolyzed esculin, they are?

A

enterococci and members of S. bovis group.

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20
Q

In the bile esculin test…

A

esculin molecules split

esculetin reacts with Ferric citrate

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21
Q

A black color in the medium for an Esculin bile test indicates what?

A

The organism is Bile Esculin-positive

a non-darken medium= negative

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22
Q

The Bile Esculin test is to…

A

identify enterococci members of the S. bovis group that are positive.

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23
Q

The Bile Esculin test is perform how?

A

spot inoculation of a Bile Esculin Agar plate

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24
Q

Give the 3 main characteristics of Eosin Methylene

Blue Agar

A

Complex/ undefined (chemically)
Selective
Differential

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25
List the ingrdients in Eosin Methylene | Blue Agar
peptone, lactose, sucrose, and the dyes eosin Y and methylene blue.
26
What is the role of peptone in Eosin Methylene | Blue Agar?
It provides nutritional components
27
The enteric bacteria are encourage to grow and are indentified in the Eosin Methylene Blue Agar because?
sugars included in the medium
28
Lactose is to ... as sucrose is to.....
Lactose is to E. coli as sucrose is proteus or Salmonella. (they encourage the bacteria growth)
29
Why add the dye in the Eosin Methylene Bue Agar?
Inhibit the growth of Gram-positive organism | React with vigorous lactose fermenters in acidic environment
30
Fermneters like (blank) will grow and turn the Eosin Methylene Blue Agar what color?
The medium turns dark purple or black when E. coli is present.
31
Enterobacter and Klebsiella species turns a Eosin Methylene Blue Agar what color?
Pink to dark purple (less agressive than E. coli as a fermenter)
32
In which test will the organisms (Non fermenters & Sucrose Fermenters) retain or take color of the medium ?
Eosin Methylene Blue Agar test
33
Why do we perform the Eosin Methylene Blue Agar test?
To isolate the fecal coliforms
34
Which test is used for isolation of fecal coliform?
Eosin Methylene Blue Agar
35
What Organisms are used for the fecal coliform Test
E. coli etc.. ( Eosin Methylene Blue Agar)
36
What was the technique of the Eosin Methylene Blue Agar?
Spot inoculation of 1 Eosin Methylene Blue Agar plate (EMB plate ) and 1 Nutrient agar.
37
The Gram-positive bacteria exerienced the most growth in the Eosin Methylene Blue Agar Test. (T/F)
False. Gram-Negative did.
38
Based on observations from the Eosin Methylene Blue Agar Test we can conclude what about the probable coliform organisms? (three things)
They are Gram-Negative Dark color (purple/black) is indicative of their presence in the medium They ferment lactose &/or sucrose with acid production
39
For the Eosin Methylene Blue Agar test Gram-negatives (are/are not) inhibited by eosin and methylene blue
ARE NOT
40
Why is the Hektoen Enteric Agar a useful Test?
It is because it isolates and differentiate Salmonella and Shigella species from other Gram-Negative enteric organisms.
41
We performed the Hektoen Enteric Agar Test by...
Spot inoculation of Hektoen Enteric Agar plate
42
Hektoen Enteric Agar is defined an uncomplex. (T/F)
False. It is undefined and complex chemically
43
Is Hektoen Enteric Agar Selective or other wise. | Explain.
It is moderately selective | because
44
Hektoen Enteric Agar is not a differntial medium. (T/F)
Fasle. IT IS.
45
How can Hektoen Enteric Agar carry out its purpose?
Based on the organisms ability to ferment lactose, sucrose, or salicin and to reduce sulfur to hydrogen sulfide gas.
46
In the Hektoen Enteric Agar Test what is produce as reult of fermentation?
Black Precipitate is produced called ferrous sulfide.
47
What makes Hektoen Enteric Agar a mederately selective medium?
The bile salts prevent growth of Gram-positive bacteria.
48
What dyes are used in the Hektoen Enteric Agar and why?
Bromthymol blue and acid fuschsin to indicate pH changes.
49
What makes the Salmenella and Shigella different from other enterics ( indentifiable characteristic)
They do not break down any of the sugars, they simply break down the animal tissues, this raises the pH and gives off a blue-green color.
50
Salmonella reduces what..
sulfur to hydrogen sulfide
51
What are antibiotics?
natural antimicrobial agents produced by microorganisms. Ex. penicillin
52
What is the name of the mold that produces Penicillin?
Penicilium notatum
53
Kirby-bauer Test A.K.A is
disk diffusion test
54
What is the purpose of the disk diffusion Test
It measures the effectiveness of antimicrobics against pathogens
55
In the Kirby-bauer Test if the organism is NOT | susceptible to the drug a clear zone appear around the disk where growth is inhibited.
FALSE. | if the organism IS susceptible to the drug a clear zone appear around the disk where growth is inhibited.
56
Zone of inhibition depends on what?
Sensitivity of the bacteria to the drug | and once the chemical's MIC (minimum inhibitory concentration) is reached.
57
What is the difference between bactericidal and bacteriostatic.
BACTERICIDAL: chemical kills bacterial and causes the clear zone. BACTERIOSTATIC: Chemical simply stops the growth of the bacteria w/o killing.
58
What is the name of the agar used fo the if the Kirby-bauer test and what's its pH?
Mueller-Hinton Agar | pH of 7.2-7.4
59
In which test will the depth of the Agar plate be important for obtaining accurate results
Kirby-bauer test / disk diffusion test
60
We measure the diameters of clear zones in
millimeters

Microbiology (2 decks)

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