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18 Cards in this Set
- Front
- Back
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MacConkey agar selects for which group ofbacteria? Explain.
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Inhibits Gram-positive bacteria andselects Gram-negative bacteria
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MacConkeyagar media differentiates between enteric bacteria based on what biochemicalreaction? Explain.
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One can use carbohydrate lactose, bile salts,and pH indicator neutral red to differentiate between enteric bacteria based ontheir ability to ferment lactose. The bacteria will be separated into two groups,with one consisting of the lactose fermenters and the other consisting of thelactose non-fermenters
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If the organism is E.coli, what would yousee on your plates? Explain.
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The colonies and surrounding media willbe pink in color
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Ifthe organism(s) is/are other enterics, what would you see on your plate? Explain.
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The colonies can be red, tan, or transparent.
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EMBagar selects for which group of bacteria? Explain.
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The dyes eosin Y and methylene blue inhibitthe growth of Gram-positive bacteria, but allow the growth of Gram-negative bacteria
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EMBagar media differentiates between gram negative enterics based on what biochemicalreaction? Explain.
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Lactose fermentation.
When fermented, produces large amount of acid, causing plate to turn metallic green in color When smaller amount of acid are produced from the reaction, the colonies will turn pink to purple in color When there is a lack of lactose fermentation, no acid will be produces and the colonies will be colorless. |
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Ifthe organism is E.coli, what would you see on your plates? Explain.
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Metallic green in color
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Ifthe organism(s) is/are other enterics, what would you see on your plate? Explain.
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Blue fish eye on pink background
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HEAagar selects for which group of enterics specifically which bacteria? Explain.
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HEA agar selects for enterics, especiallySalmonella and Shigella isolated from fecal specimens.
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HEAagar media differentiates bacterial groups based on what biochemical reaction? Explain.
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The bacterial groups can be differentiatedthrough a test for fermentation. The acid that is produced by fermentation willcause the plate to turn yellow-orange in color. This result will be seen if thebacteria are lactose fermenters. The lactose non-fermenters will not change thecolors of the media.
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Ifthe organism is Salmonella, what would you see on your plates? Explain.
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Salmonella is a lactose non-fermenter,and so there will be no change in the color of the plate.
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Ifthe organism(s) is/are other enterics, what would you see on your plate? Explain.
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If the organism or organisms is/are lactosefermenter(s), the plate will turn yellow-orange in color.
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MSAagar selects for which group of bacteria? Explain.
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Mannitol Salt Agar is used to isolate and identify species ofstaphylococci
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MSAagar media differentiates staphylococcal species based on what biochemicalreaction? Explain.
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Contains a high concentration of salt(7.5% NaCl), which inhibits the growth of most bacteria other thanstaphylococci
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Ifthe organism is Staphylococcus aureus, what would you see on yourplates? Explain.
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The plate will turn gold in color because Staphylococcus aureus ferments mannitol.
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Ifthe organism is other Staphylococcusepidermis, what would you see on your plate? Explain.
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The colonies and the plate will be redbecause Staphylococcus epidermis doesnot ferment mannitol.
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Staphylococcusand Streptococcus are bothGram-positive cocci. What test would you perform to differentiate them?
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Thecatalase test will differentiate between them. In the catalase test, superoxidedismutase breaks down superoxide, consequently producing hydrogen peroxide. Staphylococcus bacteria will testpositive for catalase and Streptococcusbacteria, which lack superoxide dismutase and hydrogen peroxide, will test negativefor catalase.
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Catalase process
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2H2O2------------->2H2O & O2 (produces bubbles)
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