Lab exam chapter 9 Flashcards
Where do a lot of the pathogenic organisms come from
fecal contamination of the water supply
Most fecal microbes are ________ pathogenic but…
not; but the presence of fecal microbes in a water supply could indicate fecal contamination and thus possible pathogen
What are the 4 properties of an indicator organism
- the only natural environment of the microbe should be in association with feces, such as intestinal tracts–present in its natural environment
- it should not grow readily in nature outside of its natural environment
- the bacterium should survive longer than the most viable pathogens but not so long that historical events are detected
- it should be easy to grow, detect, and identify in the lab
The _______ are the closest to fulfilling the criteria of indicator organisms
coliform
What do coliforms measure
the biological contamination of water
coliforms are an example of
enteric bacteria
Coliforms are non ________ forming
spore
coliforms are what gram and shape
gram negative rods
coliforms are what gram and shape
gram negative rods
coliforms are what type of oxygen relationship
falcultative anaerobic
What is a fecal coliform
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
What parts of fecal coliforms cause disease
only a few strains
What is most probable number analysis doing
gaining quantitative data on the concentration of bacteria based on the presence or absence of grwoth
To measure the number of fecal coliforms, coliforms are detected in 2 sequential stages
- presumptive test is done
- confirmed test is done
What occurs in step 1: presumptive test is done
dilutions of water samples are added to a series of LLTB tubes and positive growth in each is recorded
What occurs in step 2: confirmed test is done
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
What does step 1 in LLTB aim to do
revive the damages coliform cells such that they can increase their number and be detected by gas resulting from lactose fermentation
What does step 2 in BGLB broth and EC broth aim to do
select more effectively against gram positive organisms without putting undue stress on the recovered coliforms population
The EC broth tells us that what is present
fecal coliforms
What is the MPN number
the predicted number of cells in the middle tube
In the colilert test what is ONPG degraded by
beta galactosidase
What has beta galactosidase
coliforms
MUG is degraded by what in the colilert test
beta glucuronidase
What has beta glucuronidase
E. coli
What does the colilert test predict
Most probable coliforms and E.coli in water samples
ONPG is similar to what
lactose
MUG can degration results in production of 4-methyl umbelliferone which is a
fluorescent product
For ONPG what color means it contains that enzyme
yellow
What would you expect to grow on MAC
gram negative bacteria
What would you expect to grow on PCA
anything–all purpose
What do dark red colonies on MAC plates determine
total coliforms present in food
Why is E. Coli a good indicator
they do not survive long in environments outside of the host and can be differentiated from other coliforms by incubating on selective media
