Antimicrobial Susceptibility Testing

Question 0

Destroys microorganisms by inhibiting their development or action

Answer 0

Antimicrobial agents

Question 1

Produced by microorganisms that inhibit the growth of other microorganisms

Answer 1

Antibiotics

Question 2

Agents that inhbit the growth of microorganisms but relies on the host immune system to follow through to destroy organisms

Answer 2

Bacteriostatic agents

Question 3

Agents that kill the microbe and causes cell lysis

Answer 3

Bacteriocidal agents

Question 4

Agents with limited spectrum of action. Example: penicillin

Answer 4

Narrow spectrum

Question 5

Spectrum of activity of penicillin

Answer 5

Gram positive bacteria

Question 6

Agents that action against gram positive and gram negative bacteria. Example: tetracycline

Answer 6

Broad spectrum

Question 7

Disadvantage of using broad spectrum agents

Answer 7

They also destroy/inhibit normal flora

Question 8

Infections that results afater the treatment of the primary infection

Answer 8

Superinfection

Question 9

3 organisms capable of superinfection

Answer 9

• Pseudomonas aeruginosa
• Candida albicans (fungus)
• Staphylococcus aureus

Question 10

2 types of bacterial resistance

Answer 10

• intrinsic resistance

- acquired resistance

Question 11

Type of bacterial resistance. Characteristic of organism before antibiotic use

Answer 11

Intrinsic resistance

Question 12

Bacteria that has intrinsic resistance to novobiocin

Answer 12

Staphylococcus saprophyticus

Question 13

4 bacteria that have intrinsic resistance to polymyxins

Answer 13

• Proteus
• Providencia
• Edwardsiella
• Morganella

Question 14

Type of bacterial resistance that is necessitated by prior exposure to the antimicrobial agent. May result from chromosomal mutations or from plasmids.

Answer 14

Acquired resistance

Question 15

3 ways for the transfer of resistance

Answer 15

• conjugation
• transduction
• transformation

Question 16

3 specific mechanisms of resistance

Answer 16

• modification of the target site
• inactivation of the antimicrobial agent
• decreased permeability of the cell wall

Question 17

Medium used with Kirby-Bauer Disk Diffusion Test

Answer 17

Mueller-Hinton Agar

Question 18

Specific disk diffusion susceptibility testing method which uses MHA and paper disks impregnated with specific antibiotics are place on the agar and then the zone of inhibition is measured

Answer 18

Kirby-Bauer Disk Diffusion Test

Question 19

An indicator of the relative susceptibility of of the organism to the antibiotic in the Kirby-Bauer disk diffusion test

Answer 19

Diameter of the zone of inhibition

Question 20

4 types of results from Kirby-Bauer disk diffusion test

Answer 20

• susceptible
• resistant
• intermediate
• moderately susceptible

Question 21

Result in the KB disk diffusion test. The antibiotic appears to be effective against the bacteria because growth is inhibited.

Answer 21

Susceptible

Question 22

Result in KB disk diffusion test. The antibiotic appears to be ineffective against the bacteria tested because growth is not inhibited.

Answer 22

Resistant

Question 23

The lowest concentration of antibiotic that inhibits in vitro bacterial growth

Answer 23

Minimum Inhibitory Concentration (MIC)

Question 24

Relationship of the diameter of the zone of inhibition to the logarithm of the MIC of the antibiotic

Answer 24

Inverse linear relationship

Question 25

Peptone source of Mueller-Hinton Agar

Answer 25

Casein hydrolysate

Question 26

Component of MHA that neutralizes fatty acids

Answer 26

Cornstarch

Question 27

Effect of increased concentration of calcium and magnesium ions on aminoglycosides

Answer 27

Decreased activity of aminoglycosides against P. aeruginosa

Question 28

Effect of increased concentration of calcium and magnesium ion on tetracycline

Answer 28

Decreased activity of tetracycline against all bacteria

Question 29

Effect of increased pH on tetracycline activity

Answer 29

Decreased tetracycline activity (false resistance)

Question 30

Effect of decreased ph on tetracycline activity

Answer 30

Increased tetracycline activity (false susceptibility)

Question 31

Ideal pH of the MHA

Answer 31

pH 7.2-7.4

Question 32

Effect of thicker agar depth on zone of inhibition

Answer 32

Smaller zones (false resistance)

Question 33

Effect of thinner agar depth on zone of inhibition

Answer 33

Larger zones (false susceptible)

Question 34

Ideal agar depth of MHA

Answer 34

4 mm

Question 35

Standard where the density of the inoculum is adjusted to

Answer 35

0.5 McFarland Standard

Question 36

3 components of the McFarland Standard

Answer 36

- barium - chloride - sulfuric acid

Question 37

Effect of inoculum that is too light

Answer 37

False susceptible

Question 38

Effect of inoculum that is too heavy

Answer 38

False resistant

Question 39

How many antibiotic disks are placed on the agar plate?

Answer 39

12 different disks (8 disks forming an outer ring and 4 disks in the center)

Question 40

Temperature at which antibiotic disks are stored for long periods of time

Answer 40

-14 degress Celcius

Question 41

Temperature for working supply of antibiotic disks

Answer 41

2-8 degress Celcius

Question 42

Incubation period for the KB disk diffusion test

Answer 42

35 degree Celsius for 16-18 hours in ambient air