AST

Question 1

Products of microorganisms that reacts with and inhibit the growth of another microorganisms

Answer 1

Antibiotics

Question 2

Performed on bacteria causing an individuals infection after they have been recovered in a culture of the specimen

Answer 2

Antibiotic susceptibility testing

Question 3

What is the most common diffusion method?

Answer 3

Kirby-Bauer diffusion method

Question 4

What is the population density?

Answer 4

1.5 x 10^8 CFU/mL

Question 5

What is the recommended McFarland?

Answer 5

0.5 McFarland Standard

Question 6

What is the component of McFarland?

Answer 6

Sulfuric acid and barium chloride

Question 7

Enumerate the diffusion method

Answer 7

• kirby bauer diffusion method
• agarcup diffusion method
• agar cylinder diffusuon method
• epsilometer or gradient diffusion method

Question 8

Enumerate the dilution method

Answer 8

• macrobroth method or tube dilution method
• microtube dilution method

Question 9

What will you obtain if you mix barium chloride to sulfuric acid?

Answer 9

Barium sulfate

Question 10

The zone of inhibition is measured in

Answer 10

Millimeter

Question 11

Too thick medium will cause

Answer 11

Small zones

Question 12

An inoculum as turbid as the 0.5 McFardland contains how many CFU/ml?

Answer 12

1.5x10^8

Question 13

What is the recommended pH for AST?

Answer 13

7.2 pH (7.2-7.4)

Question 14

What instrument is used when placing antibiotic discs on the media?

Answer 14

Forceps

Question 15

What is the depth of the agar?

Answer 15

3 mm - 5 mm

Question 16

What is the culture media of choice for disc diffusion AST?

Answer 16

Mueller Hinton Agar

Question 17

What instrument is used to measure the zone of inhibition?

Answer 17

Microcaliper or ruler

Question 18

The composition of a 10 no 0.5 McFarland standard is

Answer 18

99.5 ml of 1% sulfuric acid + 0.5 mL 1.175% of Barium chloride

Question 19

Other term for kirby bauer method

Answer 19

Agar diffusion method or disk diffusion method

Question 20

How long is the incubation for non-fastidious organisms?

Answer 20

16-20 hours

Question 21

How long is the incubation for fastidious organisms?

Answer 21

20-24 hours

Question 22

Enumerate the media that we can use in preparation of pure inoculum

Answer 22

• mueller hinton broth
• trypticase soy broth
• sterile distilled water
• natural saline solution
• brain heart infusion broth

Question 23

If standard more turbid than inoculum…

Answer 23

Add colonies to inoculum

Question 24

If inoculum more turbid than standard…

Answer 24

Add distulled water to inoculum

Question 25

Heavy inoculum will result in

Answer 25

Small zone sizes

Question 26

Lighter inoculum will result in

Answer 26

Larger zone sizes

Question 27

Indicates that the organisms is inhibited by the recommended dose, at the infection site of an Antimicrobial agent

Answer 27

Susceptible or sensitive

Question 28

Organisms is not inhibited by recommended dose

Answer 28

Resistant

Question 29

Represents an organisms that may require a higher dose of antibiotic for a longer time period to be inhibited

Answer 29

Intermediate

Question 30

Enumerate the step by step procedure for kirby bauer method

Answer 30

• preparation of pure inoculum using Mueller-Hinton broth
• standardize pure inoculum using 0.5 McFarland standard
• streak the pure inoculum into the media
• apply antibiotic discs
• incubate
• measure the diameter of zone of inhibition
• interpret the result