Lab exam chapter 9

Question 1

Where do a lot of the pathogenic organisms come from

Answer 1

fecal contamination of the water supply

Question 2

Most fecal microbes are ________ pathogenic but…

Answer 2

not; but the presence of fecal microbes in a water supply could indicate fecal contamination and thus possible pathogen

Question 3

What are the 4 properties of an indicator organism

Answer 3

1. the only natural environment of the microbe should be in association with feces, such as intestinal tracts–present in its natural environment
2. it should not grow readily in nature outside of its natural environment
3. the bacterium should survive longer than the most viable pathogens but not so long that historical events are detected
4. it should be easy to grow, detect, and identify in the lab

Question 4

The _______ are the closest to fulfilling the criteria of indicator organisms

Answer 4

coliform

Question 5

What do coliforms measure

Answer 5

the biological contamination of water

Question 6

coliforms are an example of

Answer 6

enteric bacteria

Question 7

Coliforms are non ________ forming

Answer 7

spore

Question 8

coliforms are what gram and shape

Answer 8

gram negative rods

Question 9

coliforms are what gram and shape

Answer 9

gram negative rods

Question 10

coliforms are what type of oxygen relationship

Answer 10

falcultative anaerobic

Question 11

What is a fecal coliform

Answer 11

type of coliform that is capable of lactose fermentation to acid and gas within 48 hours at a growth temp of 44 or 45 degrees C

Question 12

What parts of fecal coliforms cause disease

Answer 12

only a few strains

Question 13

What is most probable number analysis doing

Answer 13

gaining quantitative data on the concentration of bacteria based on the presence or absence of grwoth

Question 14

To measure the number of fecal coliforms, coliforms are detected in 2 sequential stages

Answer 14

1. presumptive test is done
2. confirmed test is done

Question 15

What occurs in step 1: presumptive test is done

Answer 15

dilutions of water samples are added to a series of LLTB tubes and positive growth in each is recorded

Question 16

What occurs in step 2: confirmed test is done

Answer 16

samples from the positive presumptive test are inoculated into BGLB and EC broth tubes–positive results are then used to calculate the most probable number of cells in the original sample

Question 17

What does step 1 in LLTB aim to do

Answer 17

revive the damages coliform cells such that they can increase their number and be detected by gas resulting from lactose fermentation

Question 18

What does step 2 in BGLB broth and EC broth aim to do

Answer 18

select more effectively against gram positive organisms without putting undue stress on the recovered coliforms population

Question 19

The EC broth tells us that what is present

Answer 19

fecal coliforms

Question 20

What is the MPN number

Answer 20

the predicted number of cells in the middle tube

Question 21

In the colilert test what is ONPG degraded by

Answer 21

beta galactosidase

Question 22

What has beta galactosidase

Answer 22

coliforms

Question 23

MUG is degraded by what in the colilert test

Answer 23

beta glucuronidase

Question 24

What has beta glucuronidase

Answer 24

E. coli

Question 25

What does the colilert test predict

Answer 25

Most probable coliforms and E.coli in water samples

Question 26

ONPG is similar to what

Answer 26

lactose

Question 27

MUG can degration results in production of 4-methyl umbelliferone which is a

Answer 27

fluorescent product

Question 28

For ONPG what color means it contains that enzyme

Answer 28

yellow

Question 29

What would you expect to grow on MAC

Answer 29

gram negative bacteria

Question 30

What would you expect to grow on PCA

Answer 30

anything–all purpose

Question 31

What do dark red colonies on MAC plates determine

Answer 31

total coliforms present in food

Question 32

Why is E. Coli a good indicator

Answer 32

they do not survive long in environments outside of the host and can be differentiated from other coliforms by incubating on selective media