ANTIMICROBIAL SUSCEPTIBILITY TESTING

Question 1

Standard inoculum size: Test tube dilution/broth method

Answer 1

5 x 105 CFU/ml

Question 2

Broth volume: 0.05-0.1 ml

Answer 2

Microdilution

Question 3

Broth volume: 10 ml or greater

Answer 3

Macrodilution

Question 4

The lowest conc. of the antibiotic without bacterial growth after 16 to 24 hours of incubation.

Answer 4

MIC

Question 5

The lowest conc. Of the antibiotic without bacterial growth when subcultured to a fresh medium.

Answer 5

MLC

Question 6

to improve detection of oxacillin-resistant staphylococci

Answer 6

MH broth with 2%NA CL

Question 7

It is brought together to test on an agar-based medium rather than in a broth.

Answer 7

Antimicrobial conc. and Organisms

Question 8

Standard inoculum size: Agar Dilution Method

Answer 8

1x10 4 CFU/ml

Question 9

How many weeks of shelf life of agar dilution plate is for most antimicrobial agents?

Answer 9

1 week only

Question 10

After incubation the plates are examined for what?

Answer 10

growth

Question 11

Standard inoculum size: Disk Diffusion Method

Answer 11

: 1.5 x108 CFU/ml Medium: MHA

Question 12

Limited to aerobic and facultatively anaerobic bacteria.

Answer 12

Disk Diffusion Method

Question 13

Filter paper disk impregnated with various antimicrobial agents of specific concentration are carefully placed on an agar plate previously inoculated with the bacterium being tested.

Answer 13

Disk Diffusion Method

Question 14

The use of a standard inoculum size is important as culture purity and is accomplished by comparison of the turbidity of an organism suspension with a turbidity standard.

Answer 14

Turbidity Standard

Question 15

0.5% Mc. Farland

Answer 15

Turbidity Standard

Question 16

Pure cultures are grown or are directly prepared from agar plates to match the turbidity of how much McFarland standard?

Answer 16

0.5 McFarland Standard

Question 17

Pure Inocula (culture) are obtained by selecting of how many colonies of the same morphology.

Answer 17

4-5 colonies

Question 18

MHA containing 5 % sheep’s blood is used for testing what?

Answer 18

Streptococci and other fastidious organisms

Question 19

If the agar is too thick, zone sizes would be?

Answer 19

smaller

Question 20

If agar is too thin, zone sizes would be?

Answer 20

larger

Question 21

Late examination of test plates after zone can become what?

Answer 21

over grown

Question 22

Use of wrong organism is one of the causes of what?

Answer 22

False Resistance