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Portage Microbiology > 4.2 Agar Plates Part 3 > Flashcards

4.2 Agar Plates Part 3 Flashcards

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Biology 101 flashcards
1
Q

What color is a MacConkey agar?

A

pale red

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2
Q

What type of media is in a MacConkey agar?

A

selective and differential

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3
Q

What is present in the media of MacConkey agar?

A

crystal violet and bile salts; lactose, and pH indicator

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4
Q

What is the purpose of the crystal violet and bile salts in a MacConkey agar?

A

restricts gram positive bacterial growth

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5
Q

What are the only bacteria that can be grown on MacConkey agar plates?

A

gram negative

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6
Q

What color is the pH indicator under acidic conditions on a MacConkey agar?

A

red

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7
Q

What is the purpose of lactose in a MacConkey agar?

A

differentiate between lactose fermenters and nonfermenters

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8
Q

What color do lactose fermenters appear on a MacConkey agar? Non-fermenters?

A

fermenters = red
nonfermenters = white/tan

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9
Q

When does the MacConkey agar turn yellow?

A

pH > 8.0

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10
Q

What type of bacteria would make the MacConkey agar plate turn yellow?

A

non-fermenting microbe

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11
Q

When does the MacConkey agar plate turn dark red?

A

pH < 6.8

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12
Q

What type of bacteria would cause the MacConkey agar plate to turn dark red? Why?

A

lac+ microbe due to acid production during fermentation

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13
Q

What does E coli cause on a MacConkey plate?

A

formatio of vibrant pink colonies

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14
Q

What is the main function of MacConkey plates clinically?

A

isolate intestinal pathogenic microbes such as salmonella and shigella

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15
Q

What is a SMAC agar?

A

sorbitol-MacConkey agar

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16
Q

What is the function of the SMAC plate?

A

special MacConkey palte that is formulated to detect the presence of E Coli O157:H7

17
Q

What is E coli able to ferment under standard enteric conditions?

A

lactose
sorbitol

18
Q

What is E Coli )157;H7 able to ferment under normal enteric conditions?

A

only lactose

19
Q

What is the purpose of SMAC plates containing both lactose and sorbitol?

A

differentiate non-pathogenic strains of E coli from pathogenic strains of E coli

20
Q

What is the pathogenic strain of E coli?

A

O157:H7

Portage Microbiology (53 decks)

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