(Lecture) Antimicrobial Susceptibility Testing

Question 1

A laboratory procedure in which it determines the susceptibility pattern of an isolate

Answer 1

Antimicrobial Susceptibility Testing

Question 2

Substance that inhibit the growth of microorganisms

Answer 2

Antibiotics

Question 3

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

Answer 3

Antibiotics

Question 4

This is performed on bacteria causing an individual’s infection after they have been recovered in a culture of the specimen.

Answer 4

Antibiotic Susceptibility Testing

Question 5

What are the 2 Methods of AST?

Answer 5

Diffusion Method
Dilution Method

Question 6

It is used to determine the potential effectiveness of specific antibiotics on the bacteria and/or to determine if the bacteria have developed resistance to certain antibiotics.

Answer 6

Antibiotic Susceptibility Testing

Question 7

List down the methods under Diffusion Methods:

Answer 7

1. Kirby-Bauer Diffusion Method
2. Agar Cup Diffusion Method
3. Agar Cylinder Diffusion Method
4. Epsilometer or Gradient Diffusion Method

Question 8

List down the methods under Dilution Methods:

Answer 8

1. Macrobroth Method or Tube Dilution Method
2. Microtube Dilution Method

Question 9

It is a suspension of bacteria that has been isolated from a patient.

Answer 9

Pure Inoculum

Question 10

Required number of bacteria that must be present in a pure inoculum:

Answer 10

1.5 x 10^8 CFU/mL

Question 11

Required number of bacteria that must be present in a pure inoculum:

Answer 11

1.5 x 10^8 CFU/mL

Question 12

This is used to standardize the approximate number of bacteria in a liquid suspension by visually comparing the turbidity of a test suspension with the turbidity of a McFarland standard

Answer 12

Pure Inoculum

Question 13

Pure Inoculum is used to standardize the approximate number of bacteria in a liquid suspension by visually comparing the turbidity of a test suspension with the turbidity of a _____

Answer 13

McFarland Standard

Question 14

McFarland Standard is prepared by adding _____ to sulfuric acid to obtain a barium sulfate precipitate

Answer 14

Barium chloride

Question 15

Pure Inoculum is prepared by adding barium chloride to _____ to obtain a barium sulfate precipitate

Answer 15

Sulfuric acid

Question 16

Pure Inoculum is prepared by adding barium chloride to sulfuric acid to obtain a _____

Answer 16

Barium sulfate precipitate

Question 17

Recommended population density:

Answer 17

1.5 x 10^8 CFU/mL

Question 18

_____ of 1% Sulfuric acid + 0.5 mL of 1.175% Barium chloride

Answer 18

99.5 mL

Question 19

99.5 mL of _____ Sulfuric acid + 0.5 mL of 1.175% Barium chloride

Answer 19

1%

Question 20

99.5 mL of 1% Sulfuric acid + _____ of 1.175% Barium chloride

Answer 20

0.5 mL

Question 21

99.5 mL of 1% Sulfuric acid + 0.5 mL of _____ Barium chloride

Answer 21

1.175%

Question 22

A tube that has barium chloride and sulfuric acid and it doesn’t have any bacteria.

Answer 22

McFarland Standard

Question 23

Also known as Agar Diffusion Method or Disk Diffusion Method

Answer 23

Kirby-Bauer Method

Question 24

Kirby-Bauer Method is also known as _____ or _____

Answer 24

Agar Diffusion Method
Disk Diffusion Method

Question 25

Principle of Kirby-Bauer Method

Answer 25

- A standardized suspension of organism is inoculated into MHA (Mueller-Hinton Agar) - Paper disk impregnated with specific antibiotics concentration are placed into the agar - After 16-20 hours incubation, the diameters of the zone of inhibitions are measured - Results are compared to determine susceptibility or resistance

Question 26

A Method wherein you will inoculate the bacteria to the whole surface of culture media without space.

Answer 26

Lawn Culture Method

Question 27

Kirby-Bauer Method is isolated using _____ - meaning you will inoculate the bacteria to the whole surface of culture media without space. Then put on an antibiotic disc. Each antibiotic disc has different antibiotics.

Answer 27

Lawn Culture Method

Question 28

The area surrounding the antibiotics wherein it doesn't have a growth.

Answer 28

Zone of Inhibition

Question 29

An area with no zone of inhibition is equivalent to _____

Answer 29

6

Question 30

Lowest Zone of Inhibition Measurement

Answer 30

6

Question 31

Step-by-Step Procedure for Kirby-Bauer Method

Answer 31

1. Preparation of pure inoculum 2. Standardize pure inoculum, using 0.5 McFarland Standard 3. Streak the pure inoculum into the medium 4. Apply antibiotic discs 5. Incubate 6. Measure the zone of inhibition

Question 32

In Kirby-Bauer Diffusion Method, we prepare the pure inoculum using the following:

Answer 32

1. Mueller-Hinton Broth 2. Trypticase Soy Broth 3. Sterile Distilled Water 4. Natural Saline Solution 5. Brain Heart Infusion Broth

Question 33

If the standard is more turbid than inoculum, what do we do?

Answer 33

Add Colonies or Incubate Inoculum

Question 34

If the inoculum is more turbid than standard, what do we do?

Answer 34

We add distilled water into the inoculum

Question 35

A heavy inoculum will result in _____, whereas a lighter inoculum will give _____

Answer 35

Small Zone Sizes Larger Zone Sizes

Question 36

A _____ will result in small zone sizes, whereas a _____ will give larger zone sizes

Answer 36

Heavy Inoculum Lighter Inoculum

Question 37

In streaking the pure inoculum into the medium, we use _____ and we streak with _____

Answer 37

Sterile Cotton Swab No Spaces in Between

Question 38

In applying antibiotic discs, we use _____.

Answer 38

Forceps or Tweezers

Question 39

Preferred spaces in applying antibiotic discs

Answer 39

At least 25mm each antibiotic

Question 40

Incubation period for Kirby-Bauer Method

Answer 40

35 degree Celsius for 16/18-20 hours

Question 41

In measuring the zone of inhibition, what instrument/s is/are used?

Answer 41

Ruler or Microcaliper

Question 42

Unit used in measuring the zone of inhibition

Answer 42

mm or millimeter

Question 43

Bacterias are being killed fast. What is the interpretation of the result?

Answer 43

Susceptible or Sensitive

Question 44

Indicates that the organism is inhibited by the recommended dose, at the infection site of an antimicrobial agent

Answer 44

Susceptible or Sensitive

Question 45

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

Answer 45

Intermediate

Question 46

Antibiotics are not effective for that particular bacteria. This indicates that the microorganisms are _____ to the antibiotics.

Answer 46

Resistant

Question 47

Organism is not inhibited by recommended dose

Answer 47

Resistant

Question 48

Considerations in Antimicrobial Susceptibility Testing;

Answer 48

1. Growth Medium 2. Inoculum 3. Temperature and Atmospheric Conditions 4. Choice of Antibiotic Panel 5. Reading and Interpreting Results

Question 49

pH required for the Growth of Medium

Answer 49

7.2-7.4

Question 50

Agar depth required for the Growth of Medium

Answer 50

3-5mm

Question 51

If the medium is _____ the zones will be falsely small

Answer 51

Too thick

Question 52

If the medium is too thick the zones will be falsely _____

Answer 52

Small

Question 53

If the medium is _____ the zones will be falsely large

Answer 53

Too thin

Question 54

If the medium is too thin the zones will be falsely _____

Answer 54

Large