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16 Cards in this Set
- Front
- Back
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Coliform group loosely refers to ______ bacteria |
Enteric (intestinal) |
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What are the definition of coliform |
Facultatively anaerobic Rod-shaped Gram negative Non spore forming Ferment lactose with gas production |
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Coliforms are _____ organisms |
Indicator |
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What does coliforms being indicator organisms show |
Presence in a sample indicates possible fecal contamination |
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What is most-probable-number (MPN) technique employed for |
The detection of coliforms in freshwater supplies |
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What does sample diluted to extinction mean |
Successively higher dilutions of a source are made until no viable organisms are detected in the final dilution |
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What is the "probable" number of viable organisms in the sample based upon? |
A probability dilution that takes into consideration the higest dilution in which a positive result is found, the magnitude of dilutions and number of replicates performed |
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Why is a liquid nutrient medium often employed to detect viable organisms |
Allows use of larger source volumes that can be used for direct plating Larger volumes is also adds to improvement of accuracy |
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What are the three differential media used in MPN method |
Lauryl tryptose broth (LTB) Brilliant green alctose bile (BGLB) E Coli Broth (EC) |
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What is lauryl tryptose broth |
Selective for coliforms, though doesn't screen out all non coliforms Is used for presumptive coliform determination |
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What is brilliant green lactose bile |
Inhibits non-coliforms and is used to confirm the presence of coliforms |
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What is e coli broth |
Selective for e coli when incubated at 45.5 C Detect presence of fecal coliforms |
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All tubes contain what |
10 ml of broth Durham tubes |
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What are durham tubes
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Small inverted glass tubes
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What do durham tubes do
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Trap gas |
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