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30 Cards in this Set
- Front
- Back
What is the name of this media?
What type of media is this? |
Name: Blood Agar
TYPES: (1) Enriched (enhances growth of FASTIDIOUS bacteria (2) Differential Media (permits the detection of groups of bacteria that produce HEMOLYSINS) |
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Why is blood agar considered a differential media?
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Because it allows the distinction between bacteria that grow on it.
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What is the name of this media? What type of media is this? And Why?
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MacConkey's (Light Pink)
TYPES: (1) Selective Media-used to grow pathogenic enterobacteria (Gram Neg.) so they INHIBIT the growth of Gram Positive bacteria (2) Differential Media-distinguishes between those bacteria that ferment lactose |
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What is the name of this media? What type of media is it and why?
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Media: Mannitol Salt (Orange/Pink)
TYPES: (1) Selective media-Allows Gram Positive bacteria to grow (HIGH SALT concentration INHIBITS growth of many bacteria) (2) Differential media- Distinguishes between mannitol fermenters that produce acid |
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MacConkey's Agar undergoes what color changes? The bacteria produces?
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MacConkey's:
Differential Media-distinguishes between (1) bacteria that ferment lactose (RED) (2) Bacteria that do not (CLEAR ) |
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Mannitol Salt Agar undergoes what color changes? The bacteria produce?
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Mannitol Salt:
Differential Media: Distinguishes between mannitol fermenters (1) that produce acids (turns phenyl red into YELLOW) (2) those that do not (phenyl red stays RED) |
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What is the active ingredients in Blood Agar? What do they do?
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Ingredients:
(1) 5% Sheeps blood-enhances growth of fastidious bacteria |
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What are the active ingredients in MacConkey's Agar? What do they do?
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Ingredients:
(1) bile salts (2) crystal violet dye both which inhibit the growth of Gram Positive bacteria |
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What is the active ingredient in Mannitol Salt agar? What does it do?
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Ingredient:
(1) Salt (7.5% NaCl) High salt concentration inhibits the growth of many bacteria |
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What are fastidious bacteria?
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Bacteria that grow poorly or not at all on simple media such as nutrient agar.
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What is Selective medium?
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Selective medium-
contains chemicals that prevent the growth of certain bacteria, while allowing others to grow |
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What is Differential medium?
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Differential Medium
A media may be differential if their nutrient makeup allows for distinguishing between bacteria on the basis of their metabolic properties. |
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What is Enriched medium?
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Enriched medium
Are generally formulated to enhance the growth of difficult to grow or fastidious bacteria. |
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An example of enriched media
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Blood Agar
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What are the 3 types of hemolysis?
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(1) Alpha
(2) Beta (3) Gamma |
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What are hemolysins?
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Hemolysis-
substances that damage the membrane of red blood cells (erythrocytes) causing the cells to burst (hemolysis) |
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What is alpha hemoylsis? Describe its appearance
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Alpha hemolysis – incomplete lysis of RBC with a green, cloudy zone around the bacterial colony.
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What is beta hemolysis? Describe its appearance
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Beta hemolysis –complete destruction of the RBC and a clear edge around the colony
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What is gamma hemoylsis? Describe its appearance
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Gamma hemolysis - a lack of any hemolytic activity.
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Which bacteria shows alpha hemolysis?
Enterococcus faecalis (left) or Staphylococcus aureus (right) |
Enterococcus faecalis (left)
see green, cloudy outline |
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Which bacteria shows beta hemolysis?
Enterococcus faecalis (left) or Staphylococcus aureus (right) |
Staphylococcus aureus (right)
Clear outline---because bacteria ate through the blood agar (complete hemolysis) |
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Mannitol Salt Agar contains which sugar?
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Mannitol
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Why are some bacteria not able to grow on Mannitol Salt agar?
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Because it contains 7.5% salt and it's too salty for some bacteria to grow on
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What is the pH indicator in Mannitol Salt?
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pH indicator:
Phenyl Red |
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Why is the medium around Staphylococcus aureaus yellow?
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Staphylococcus aureus ferments and produces an acid causing the pH indicator (phenyl red) to turn:
YELLOW |
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Enterobactero aerogenes does not turn yellow in Mannitol Salt. Why?
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Enterobactero aerogenes DOES NOT ferment and DOES NOT produce an acid.
So the pH indicator (phenyl red) stays red. |
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Why is Staphylococcus aureus not able to grow on MacConkey's Agar?
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Bile salts and Crystal Violet kill it
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MacConkey's agar contains which sugar?
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MacConkey's contains LACTOSE
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If the colonies on Mac Conkey's Agar assume a RED color what does it mean?
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The bacteria are LACTOSE fermenters and they break down lactose into acid which causes
(1) precipitation of bile salts (2) absorption of neutral red dye That is why the colonies turn red in color |
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Why is Proteus Vulgaris a translucent color on MacConkey's Agar?
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Proteus Vulgaris is a LACTOSE NON-FERMENTER and it can not break down lactose into acid
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