Bios 351: Bacteriological Examination Of Water

Front 1

Describe three reasons why E. coli is a good indicator of fecal contamination in water.

Back 1

found in intestines but not normally found in water
easily identified
survives longer in water samples

Front 2

Describe the haracteristics of coliforms. 5

Back 2

gram-negative, facultative anaerobes, non-spore-forming, rods, lactose fermenters

Front 3

What type of medium is used for the presumptive test for coliforms?

Back 3

lactose broth

Front 4

What type of medium can be used for the confirmed test for coliforms? 2

Back 4

EMB agar or
ENDO agar

Front 5

What two types of medium are used for the completed test for coliforms?

Back 5

nutrient agar slant
lactose broth

Front 6

On EMB agar, how can you differentiate coliforms from non-coliforms?

Back 6

coliforms produce nucleated colonies (colonies with dark centers)

Front 7

Do coliforms typically produce gas as a result of lactose-fermentation?

Back 7

yes

Front 8

What is a good coloiform?

Back 8

E.Coli

Front 9

Positive result for Presumptive test?

Back 9

10% gas placement seen in tube

Front 10

What does EMB and ENDO media inhibit the growth of?

Back 10

gram positive bacteria

Front 11

Positive results for ENDO agar?

Back 11

produce reddish colonies

Front 12

Most Probable Number (MPN)?

Back 12

amount of coliforms in 100 ml of water

Front 13

Thomas' simple formula?

Back 13

MPN/100ml = # positive tubes * 100/ sgrt(ml sample in negative tubes * ml sample in all tubes)