Lab exam

Question 1

What makes MacConkey agar selective?

Answer 1

inhibitor - bile salt and crystal violet

Question 2

What makes MacConkey agar differential?

Answer 2

lactose

Question 3

What type of MO’s grow on MacConkey agar?

Answer 3

Gram negative

Question 4

what makes mannitol salt agar selective?

Answer 4

inhibitor - salt

Question 5

what makes mannitol salt agar differential?

Answer 5

mannitol

Question 6

what type of MO’s can grow on mannitol salt agar?

Answer 6

staphylococcus

Question 7

what is the pH indicator in macConkey agar?

Answer 7

natural red dye

Question 8

what is the pH indicator in mannitol salt agar?

Answer 8

phenol red dye

Question 9

what MO’s does mannitol salt agar inhibit

Answer 9

all gram negative and most gram positive

Question 10

In MacConkey agar, what would the results look like if lactose is utilized?

Answer 10

pink colonies, acidic end product

Question 11

In MacConkey agar, what would the results look like if peptones are utilized?

Answer 11

yellow colonies, alkaline

Question 12

In Mannitol salt agar, what would the results look like if mannitol was utilized

Answer 12

acidic, yellow colonies

Question 13

in Mannitol salt agar, what would the results look like if peptones are utilized?

Answer 13

alkaline, pink colonies

Question 14

describe a positive mannitol salt test

Answer 14

yellow colonies, acidic end product

Question 15

describe a positive MacConkey agar test

Answer 15

Pink colonies, acidic end product

Question 16

beta hemolysis is

Answer 16

yellow

Question 17

alpha hemolysis is

Answer 17

green

Question 18

gamma hemolysis is

Answer 18

no hemolysis

Question 19

carbohydrate fermentation test positive result

Answer 19

yellow, carb broken down, acidic

Question 20

carbohydrate fermentation test negative result

Answer 20

pink, peptones utilized, alkaline

Question 21

what is the purpose of a durham tube

Answer 21

to detect the production of CO2 while growing the MO

Question 22

carbohydrate in starch hydrolysis test

Answer 22

starch

Question 23

enzyme required to break down starch in starch hydrolysis test

Answer 23

amylase

Question 24

end product formed in starch hydrolysis test

Answer 24

maltose and glucose

Question 25

indicator in starch hydrolysis test

Answer 25

iodine

Question 26

positive result in starch hydrolysis test

Answer 26

black

Question 27

what is the purpose of a quality control plate?

Answer 27

to ensure that the specimen is not contaminated

Question 28

with all the media available, why can we not grow all of the wide array of bacteria known to us?

Answer 28

because some bacteria require extreme conditions to grow

Question 29

what MO (genus) does mannitol salt agar grow?

Answer 29

staphylococcus

Question 30

define and describe a bacterial colony

Answer 30

cluster of approximately 1000 cells, exhibits specific, unique, identifying features

Question 31

identify two benefits of using agar in the media as a solidifying agent

Answer 31

bacteria can be incubated at various temperatures, there are very few MO's that can break down agar

Question 32

what color does gram negative stain

Answer 32

pink

Question 33

what color does gram positive stain

Answer 33

purple

Question 34

what are four properties used to describe bacterial colonies on solid media

Answer 34

size, shape, margin, elevation

Question 35

what enzyme must be present for hemolysis to occur

Answer 35

hemolysin

Question 36

how do you quantify a routine culture

Answer 36

quadrant growth

Question 37

if a MO grows only into the first quadrant it is

Answer 37

few

Question 38

if a MO grows into the second quadrant it is

Answer 38

moderate

Question 39

if a MO grows into the third or fourth quadrant it is

Answer 39

heavy or many

Question 40

how do you quantify the MO's in a urine culture

Answer 40

colony forming units (Counting colonies)

Question 41

describe the streaking procedure for a urine culture

Answer 41

primary streak down the plate and a continuous streak going through the first at right angles

Question 42

how long is preserved urine specimen good for

Answer 42

72 hours

Question 43

ways to collect urine sample

Answer 43

clean catch urine or catheter

Question 44

size of the loop for urine culture

Answer 44

.001 mL loop

Question 45

describe rejection criteria

Answer 45

observing more than 100 colonies of mixed NF and/or the presence of 3 or more types of pathogens (colonies greater than 10)