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14 Cards in this Set
- Front
- Back
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It selects for bacteria that tolerate 7.5% NaCl, and differentiates between bacteria according to its ability to ferment mannitol. It is used to isolate staphylococci and distinguish between individual species, for example, Staphylococcus epidermidis (non‐fermenter) versus Staphylococcus aureus (fermenter).
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What makes *mannitol salt agar (MSA) selective and differential? What does MSA select for?
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It selects for the growth of Gram‐positive bacteria. It inhibits or slows down the growth Gramnegative
bacteria by interfering with DNA synthesis. |
What bacteria selectively grow on *phenylethyl alcohol (PEA)? How does it selectively inhibit
other bacteria? |
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It is a differential, enriched media that characterizes bacteria according to its ability to lyse red blood cells. Three results can be observed:
Alpha: a greenish hue appears around a colony, due to the partial lysis of red blood cells. Beta: a clear zone appears around a colony, due to the complete lysis of red blood cells. Gamma: no change results, due to the presence of nonhemolytic bacteria. |
What type of media is *Blood Agar? How does alpha, beta and gamma hemolysis appear on
blood agar plate? |
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A positive test indicates that bacteria contain the enzyme capable of breaking down hydrogen
peroxide to water and oxygen. |
What type of information is gained from a positive *catalase test?
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This antibiotic sensitivity test can be used to differentiate between bacteria. For example,
Staphylococcus is resistant to while Micrococcus is sensitive. |
What is the purpose of the *bacitracin susceptibility test?
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Alpha:
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a greenish hue appears around a colony, due to the partial lysis of red blood cells.
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Beta:
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a clear zone appears around a colony, due to the complete lysis of red blood cells.
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Gamma:
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no change results, due to the presence of nonhemolytic bacteria.
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Mannitol Salt Agar (MSA)
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It selects for bacteria that tolerate 7.5% NaCl, and differentiates between bacteria according to its ability to ferment mannitol. It is used to isolate staphylococci and distinguish between individual species, for example, Staphylococcus epidermidis (non‐fermenter) versus Staphylococcus aureus (fermenter).
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Phenylethyl alcohol (PEA)?
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It selects for the growth of Gram‐positive bacteria. It inhibits or slows down the growth Gramnegative
bacteria by interfering with DNA synthesis. |
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Blood Agar Plate
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Enriched media that characterizes bacteria according to its ability to lyse red blood cells
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Catalase Test
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A positive test indicates that bacteria contain the enzyme capable of breaking down hydrogen
peroxide to water and oxygen. |
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Bacitracin susceptibility test?
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This antibiotic sensitivity test can be used to differentiate between bacteria. For example,
Staphylococcus is resistant to while Micrococcus is sensitive. |
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Gram‐Positive Bacteria and Unknowns
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Micro Lab 8 - is
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