Term
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Definition
| common inhabitants of the human intestinal tract and their presence in the environment is strong evidence of fecal contamination |
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Term
| What does mannitol salt agar contain? |
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Definition
| carbohydrate mannitol, 7.5% NaCl, and pH indicator phenol red |
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Term
| Phenol red is yellow at what pH? red at what pH? pink at what pH? |
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Definition
-yellow below 6.8
-red between 7.4-8.4
-pink at 8.4 and above |
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Term
| What does poor growth or no growth on mannitol salt agar mean? |
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Definition
-organism is inhibited by NaCl
-not Staphylococcus |
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Term
| What does good growth on mannitol salt agar mean? |
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Definition
-organism is not inhibited by NaCl
-Staphylococcus |
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Term
| What does yellow growth or halo on mannitol salt agar mean? |
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Definition
-organism produces acid from mannitol fermentation
-possible pathogenic Staphylococcus aureus |
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Term
| What does red growth (no halo) on mannitol salt agar mean? |
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Definition
-organism does not ferment mannitol, no reaction
-nonpathogenic Staphylococcus aureus |
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Term
| What is the purpose of mannitol salt agar? |
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Definition
| to isolate and differentiate pathogenic Staphylococcus species |
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Term
| What does the NaCl in mannitol salt agar do? |
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Definition
| makes the medium selective for Staph because most other bacteria cannot survive in this level of salinity |
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Term
| What is phenylethyl alcohol agar? |
|
Definition
| undefined, selective medium that allows growth of Gram-positive organisms and inhibits growth of most Gram-negative organisms |
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Term
| How does the phenylethyl alcohol in phenylethyl alcohol agar function? |
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Definition
| by interfering with DNA synthesis in gram-negative organisms |
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Term
|
Definition
to isolate Staph & Strep from specimens containing mixtures of bacterial flora
-typically used to screen out E. coli & Proteus spp |
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Term
| When PEA is prepared with 5% sheep blood agar, what is it used to cultivate? |
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Definition
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Term
| What does poor growth or no growth on a PEA plate indicate? |
|
Definition
-the organism is inhibited by phenylethyl alcohol
-probable Gram-negative organism |
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Term
| What does good growth on a PEA plate indicate? |
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Definition
-the organism is not inhibited by phenylethyl alcohol
-probable Staphylococcus, Streptococcus, Enterococcus, or Lactococcus |
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Term
| What color indicators does Endo Agar contain? |
|
Definition
-sodium sulfite
-basic fuchsin
(both also double as Gram-positive inhibitors) |
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Term
| What is the application of Endo Agar? |
|
Definition
| to detect fecal contamination in water or dairy products |
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Term
| What does poor growth or no growth in endo agar mean? |
|
Definition
-organism is inhibited by sodium sulfite & basic fuchsin
-gram-positive organism |
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Term
| What does good growth in endo agar mean? |
|
Definition
-organism is not inhibited by sodium sulfite or basic fuchsin
-organism is gram-negative |
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Term
| What does red or pink growth in endo agar mean? |
|
Definition
-organism ferments lactose to acid end products
-possible coliform |
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Term
| What does red or pink growth with darkened medium and/or metallic sheen in Endo agar mean? |
|
Definition
-organism ferments lactose rapidly and produces large amounts of acid
-probable coliform |
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Term
| What does colorless growth on endo agar mean? |
|
Definition
-organism does not ferment lactose, no reaction
-noncoliform |
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Term
|
Definition
| peptone, lactose, sucrose, and dyes eosin Y and methylene blue |
|
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Term
| What do the sugars in EMB do? |
|
Definition
| provide fermentable substrates to encourage growth of fecal coliforms |
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Term
| What do the dyes in EMB do? |
|
Definition
| inhibit growth of Gram-positive organisms & produce dark medium and sheen that indicates large acid production |
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Term
| What is the application of eosin methylene blue agar? |
|
Definition
| -isolation of fecal coliforms |
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Term
| What does poor growth or no growth on EMB agar indicate? |
|
Definition
-organism is inhibited by eosin and methylene blue
-gram-positive |
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Term
| What does good growth on EMB agar indicate? |
|
Definition
-organism is not inhibited by eosin and methylene blue
-gram-negative |
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Term
| What does pink and mucoid growth on EMB agar indicate? |
|
Definition
-organism ferments lactose with little acid production
-possible coliform |
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Term
| What does dark (purple to black, with or without green metallic sheen) growth on EMB agar indicate? |
|
Definition
-organism ferments lactose and/or sucrose with much acid production
-probably coliform |
|
|
Term
| What does colorless growth on EMB agar mean? |
|
Definition
-organism does not ferment lactose or sucrose, no reaction
-noncoliform |
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