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10 Cards in this Set
- Front
- Back
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What are the Enterics?
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They are Gram neg bacteria that are part of the normal intestinal flora.
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What are the main groups of enterics/
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Vibrionacae
Enterobacteriacae Pseudomonadacae Bacterodaceae |
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List 2 important biochemical properties of the enterics?
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1. Ability to ferment lactose and convert it into gas and acid. E. coli and and most of the enterobacteriacae ferment lactose while Salmonella, Shigella and pseudomonas aeruginosa do not.
2. The production of H2S, ability to hydrolyze urea, liquefy gelatin and decarboxylate specific amino acids. |
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Some growth media can do 2 things:
1. They have chemicals that inhibit the growth of Gram + bacteria that may be contaminating the sample. They have indicators that change color in the presence of lactose fermentation. Name 2 such media? |
EMB agar-(eosine Methylene Blue)
MacConkey agar(bile salts) |
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What do both of these media have in common/
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They both can inhibit G+ bacteria.
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Describe a presumptive test that can test for E. coli in river water.
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Add the river water samples to test tubes containing nutrient broth(like agar) that contains lactose. These tubes have an inverted vial that can trap gas and a dye indicator that changes color if acid is produced. After 24hrs, if lactose is fermented gas is produced and the dye is visualized. You now know that E. coli or some other nonenteric that ferments lactose is in the sample.
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How can the above test be confirmed?
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Streak EMB agar plates with the water samples, and the E. coli should form colonies with a metallic green sheen. Also, E. coli can grow at 45.5C but most nonenterics cannot.
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Regarding the above test, how can the test be completed/
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Colonies that were metallic green are placed in the broth again . if they produce acid or gas, then we know that the river water has E. coli.
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What are the three surface antigens of the enterics?
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1. O antigen-This is the most external component of the LPS of Gram neg bacteria.
2. K antigen-This is a capsule that covers the O antigen. 3. H antigen-This antigen makes up subunits of the bacterial flagella, so only motile bacteria will possess the antigen. Shigella does not have an H antigen. Salmonella has H antigens that periodically change, protecting it from antibodies. |
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The Enterics generally cause 2 disease patterns. what are they?
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1. Diarhhea-with or without systemic invasion.
2.Urinary tract infections, pneumonia, bacteremia and sepsis. |
