[LAB] Exercise 8A: Kirby-Bauer Disk Diffusion

Question 1

Meaning of MIC

Answer 1

Minimum Inhibitory Concentration

Question 2

Zones of inhibition can be interpreted using established break points recommended by what organization?

Answer 2

Clinical Laboratory Standards Institute (CLSI)

Question 3

This method involves spreading bacteria on an agar plate and placing paper discs impregnated with antibiotics on the plate

Answer 3

Kirby-Bauer

Question 4

Areas around the antibiotic disk where no bacterial growth can be seen

Answer 4

Zone of inhibition

Question 5

This zone shows that an antibiotic has been successful in stopping bacterial growth

Answer 5

Zone of inhibition

Question 6

What is measured in the zone of inhibition?

Answer 6

Diameter

Question 7

Type of test tubes used

Answer 7

Sterile Loeffler test tube or Sterile screw cap tube

Question 8

T or F: A vortex mixer is needed to perform Kirby-Bauer

Answer 8

T

Question 9

Size of sterile Petri dish needed

Answer 9

100mm or 150mm

Question 10

T or F: The test culture on BAP or TSA or NAP should be strictly 18-hour-old

Answer 10

F

should be less than 24-hour-old

Question 11

Using an inoculating loop or needle, how many similar looking colonies should you fish out?

Answer 11

3-5

Question 12

How many mL of NSS should be used in suspending fished out colonies?

Answer 12

5

Question 13

The suspension is mixed for ___ seconds using a vortex.

Answer 13

15

Question 14

T or F: If a vortex is not available, rub the sides of the tubes with an inoculating loop or needle to mix the colonies

Answer 14

T

Question 15

The turbidity of the suspension is virtually compared to

Answer 15

0.5 McFarland Standard

Question 16

T or F: Distilled water can be used to dilute the suspension to achieve the desired turbidity

Answer 16

T

Question 17

T or F: More colonies can be added to the suspension to increase turbidity

Answer 17

T

Question 18

T or F: In standardizing the inoculum, make sure that the test tubes are of the same size

Answer 18

T

Question 19

What is the culture media used in performing Kirby-Bauer Method?

Answer 19

Mueller Hinton Agar (MHA)

Question 20

The surface of the MHA medium is inoculated by what method of streaking?

Answer 20

Overlap method

Question 21

How many times should you perform the overlap method of streaking?

Answer 21

2 to 3 times

Question 22

In streaking, rotate the plate at ___ degrees each time to ensure an even distribution

Answer 22

60

Question 23

T or F: The rim/edge of the medium is swabbed before streaking

Answer 23

F

after

Question 24

The inoculation of the medium is done no more than ___ minutes from the time standardized inoculum was prepared

Answer 24

15

Question 25

Place the inoculated plates on a flat level surface with the lid partially open for ____ minutes before applying antibiotic disks

Answer 25

3 to 5

Question 26

This is used to place antibiotic disks on the agar surface

Answer 26

Flame-sterilized forceps

Question 27

T or F: Press the disk using the tip of your gloved finger to make sure it has complete contact with the agar surface

Answer 27

F

using the tip of the forceps

Question 28

Distance of each disk from one another

Answer 28

24 mm

Question 29

Distance of each disk from the edge of the plate

Answer 29

10 mm

Question 30

T or F: Plates are inverted when placed in the incubator

Answer 30

T

Question 31

Set the incubator at ____ degrees Celsius for _____ hours

Answer 31

35 to 37; 16 to 18

Question 32

Examine the plate after _____ hours of incubation

Answer 32

16 to 18

Question 33

Used to measure the diameter of the zones of inhibition

Answer 33

Ruler or Vernier Caliper

Question 34

T or F: MHA should have bacterial growth

Answer 34

T

Question 35

Arrange the steps in order:

1. Inoculation of MHA plate
2. Application of antibiotic disks
3. Reading and interpretation
4. Preparation and standardization of test inoculum

Answer 35

4 > 1 > 2 > 3