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16 Cards in this Set

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Coliform group loosely refers to ______ bacteria

Enteric (intestinal)

What are the definition of coliform

Facultatively anaerobic


Rod-shaped


Gram negative


Non spore forming


Ferment lactose with gas production

Coliforms are _____ organisms

Indicator

What does coliforms being indicator organisms show

Presence in a sample indicates possible fecal contamination

What is most-probable-number (MPN) technique employed for

The detection of coliforms in freshwater supplies

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

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

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

What are the three differential media used in MPN method

Lauryl tryptose broth (LTB)


Brilliant green alctose bile (BGLB)


E Coli Broth (EC)

What is lauryl tryptose broth

Selective for coliforms, though doesn't screen out all non coliforms




Is used for presumptive coliform determination





What is brilliant green lactose bile

Inhibits non-coliforms and is used to confirm the presence of coliforms

What is e coli broth

Selective for e coli when incubated at 45.5 C




Detect presence of fecal coliforms

All tubes contain what

10 ml of broth




Durham tubes

What are durham tubes

Small inverted glass tubes

What do durham tubes do

Trap gas

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