Microbio Lab #61 Word Scramble

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Question	Answer
Does a positive-presumptive test mean that the water is absolutely unsafe to drink? Explain. No, a positive presumptive test indicates that the water might be unsafe to drink but further testing is warranted.	No, a positive presumptive test indicates that the water might be unsafe to drink but further testing is warranted.
What might cause a false positive presumptive test?	A false positive presumptive test may be due to two or more non-coliform bacteria working synergistically to produce sufficient gas in the tube.
List three characteristics required of a good sewage indicator.	Easy to identify. Present only in sewage, not in soil. Lives slightly longer than pathogens in water.
What enteric bacterial diseases are transmitted in polluted water?	Typhoid fever, bacillary dysentery, and cholera
Name one or more protozoan diseases transmitted by polluted water.	Amoebiasis caused by E. histolytica, cryptosporidiosis caused by C. parvum, and giardiasis caused by G. lamblia.
Why don’t health departments routinely test for pathogens instead of using a sewage indicator?
List five characteristics of coliform bacteria.	Coliform bacteria are gram-negative, facultative anaerobic, non-endospore forming bacilli that ferment lactose to produce acid and gas.
How is Lactose broth with Durham tube used for the detection of coliforms?	Detect gas production from lactose fermentation.
How is Levine EMB agar used for the detection of coliforms?	a. of gram-positive growth and lactose fermentors will produce “nucleated” colonies (black centers) and may have a metallic sheen.
How is Nutrient agar slant used for the detection of coliforms?	To make a slide for Gram staining to confirm morphology (gram-negative bacilli).
Once the completed test establishes the presence of coliforms in the water sample, why might you perform the IMViC tests on these isolates?	The IMViC tests (indole, methyl red, Voges-Proskauer, citrate) are used to confirm the identity of the isolates as coliforms. These tests will differentiate E. coli, which is associated w/ sewage, from E. aerogenes, which isn't always assoc. w/ sewage.

Created by: michellevu