Water Quality Test Flashcards
What media is used for Water-Standard Coliform Testing?
Lactose broths (double strength/single strength), Brilliant Green Lactose Bile Broth (BGLBB), and Eosin Methylene Blue plate (EMB)
What are the 3 parts of Water-Standard Coliform Testing?
Presumptive, Confirmed, and Completed tests
Describe the Presumptive Test
Involves adding diff. volumes of water sample to the lactose broths.
Growth & gas production due to lactose fermentation = +
Describe the Confirmed Test
Involves transfers from the highest dilution of the lactose broths that showed growth & gas into BGLBB.
Growth & gas = +
What does the Brilliant Green select for in BGLBB?
Selects for gram negatives
What does the Bile further select for in BGLBB?
Coliforms
Describe the Completed test
Involves a positive result from BGLBB to be used to inoculate an EMB plate
Describe the results of the Completed test
E. coli will produce a metallic green sheen. Any other growth would be a coliform or other enteric.
What is the purpose of Eosin Methylene Blue?
Isolation of coliforms
What does Eosin Methylene Blue contain?
Peptones, lactose, sucrose, & the dyes eosin and methylene blue
What is the significance of the dyes in EMB?
Inhibit growth of gram + organisms; and under acidic conditions, produce a dark purple complex usually accompanied by a green metallic sheen
What does the green metallic sheen indicate on EMB?
Indicates vigorous lactose and sucrose fermentation (both dyes get precipitated)
What results in pink coloration in EMB?
Smaller amounts of acid production
Describe Colilert Assay
Combination of ONPG and MUG to determine the presence or absence of coliforms (yellow color formation only) or the presence specifically of E. coli (both yellow color formation and blue fluorescence)
What does ONPG detect?
What indicates a positive result?
The presence of beta-galactosidase (present in most coliforms)
yellow color = +
