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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

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Biology 101 flashcards
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
Q

List the ingrdients in Eosin Methylene

Blue Agar

A

peptone, lactose, sucrose, and the dyes eosin Y and methylene
blue.

26
Q

What is the role of peptone in Eosin Methylene

Blue Agar?

A

It provides nutritional components

27
Q

The enteric bacteria are encourage to grow and are indentified in the Eosin Methylene
Blue Agar because?

A

sugars included in the medium

28
Q

Lactose is to … as sucrose is to…..

A

Lactose is to E. coli as sucrose is proteus or Salmonella. (they encourage the bacteria growth)

29
Q

Why add the dye in the Eosin Methylene Bue Agar?

A

Inhibit the growth of Gram-positive organism

React with vigorous lactose fermenters in acidic environment

30
Q

Fermneters like (blank) will grow and turn the Eosin Methylene Blue Agar what color?

A

The medium turns dark purple or black when E. coli is present.

31
Q

Enterobacter and Klebsiella species turns a Eosin Methylene Blue Agar what color?

A

Pink to dark purple (less agressive than E. coli as a fermenter)

32
Q

In which test will the organisms (Non fermenters & Sucrose Fermenters) retain or take color of the medium ?

A

Eosin Methylene Blue Agar test

33
Q

Why do we perform the Eosin Methylene Blue Agar test?

A

To isolate the fecal coliforms

34
Q

Which test is used for isolation of fecal coliform?

A

Eosin Methylene Blue Agar

35
Q

What Organisms are used for the fecal coliform Test

A

E. coli etc.. ( Eosin Methylene Blue Agar)

36
Q

What was the technique of the Eosin Methylene Blue Agar?

A

Spot inoculation of 1 Eosin Methylene Blue Agar plate (EMB plate ) and 1 Nutrient agar.

37
Q

The Gram-positive bacteria exerienced the most growth in the Eosin Methylene Blue Agar Test. (T/F)

A

False. Gram-Negative did.

38
Q

Based on observations from the Eosin Methylene Blue Agar Test we can conclude what about the probable coliform organisms? (three things)

A

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
Q

For the Eosin Methylene Blue Agar test Gram-negatives (are/are not) inhibited by eosin and methylene blue

A

ARE NOT

40
Q

Why is the Hektoen Enteric Agar a useful Test?

A

It is because it isolates and differentiate Salmonella and Shigella species from other Gram-Negative enteric organisms.

41
Q

We performed the Hektoen Enteric Agar Test by…

A

Spot inoculation of Hektoen Enteric Agar plate

42
Q

Hektoen Enteric Agar is defined an uncomplex. (T/F)

A

False. It is undefined and complex chemically

43
Q

Is Hektoen Enteric Agar Selective or other wise.

Explain.

A

It is moderately selective

because

44
Q

Hektoen Enteric Agar is not a differntial medium. (T/F)

A

Fasle. IT IS.

45
Q

How can Hektoen Enteric Agar carry out its purpose?

A

Based on the organisms ability to ferment lactose, sucrose, or salicin and to reduce sulfur to hydrogen sulfide gas.

46
Q

In the Hektoen Enteric Agar Test what is produce as reult of fermentation?

A

Black Precipitate is produced called ferrous sulfide.

47
Q

What makes Hektoen Enteric Agar a mederately selective medium?

A

The bile salts prevent growth of Gram-positive bacteria.

48
Q

What dyes are used in the Hektoen Enteric Agar and why?

A

Bromthymol blue and acid fuschsin to indicate pH changes.

49
Q

What makes the Salmenella and Shigella different from other enterics ( indentifiable characteristic)

A

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
Q

Salmonella reduces what..

A

sulfur to hydrogen sulfide

51
Q

What are antibiotics?

A

natural antimicrobial agents produced by microorganisms. Ex. penicillin

52
Q

What is the name of the mold that produces Penicillin?

A

Penicilium notatum

53
Q

Kirby-bauer Test A.K.A is

A

disk diffusion test

54
Q

What is the purpose of the disk diffusion Test

A

It measures the effectiveness of antimicrobics against pathogens

55
Q

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.

A

FALSE.

if the organism IS susceptible to the drug a clear zone appear around the disk where growth is inhibited.

56
Q

Zone of inhibition depends on what?

A

Sensitivity of the bacteria to the drug

and once the chemical’s MIC (minimum inhibitory concentration) is reached.

57
Q

What is the difference between bactericidal and bacteriostatic.

A

BACTERICIDAL: chemical kills bacterial and causes the clear zone.
BACTERIOSTATIC: Chemical simply stops the growth of the bacteria w/o killing.

58
Q

What is the name of the agar used fo the if the Kirby-bauer test and what’s its pH?

A

Mueller-Hinton Agar

pH of 7.2-7.4

59
Q

In which test will the depth of the Agar plate be important for obtaining accurate results

A

Kirby-bauer test / disk diffusion test

60
Q

We measure the diameters of clear zones in

A

millimeters

Microbiology (2 decks)

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