Antimicrobial Susceptibility Testing

Question 1

Reasons for the Antimicrobial Testing (3)

Answer 1

1) the capacity of the bacterial isolate to cause disease
2) susceptibility patterns of the bacterial isolate to the Antimicrobial agents
3) availability of standard susceptibility methods

Question 2

What is the broth used for broth dilution method?

Answer 2

Mueller-Hinton Broth

Question 3

What is the principle of Broth Dilution method

Answer 3

To determine the lowest concentration of the Antimicrobial drug that will inhibit bacterial growth (MIC)

Question 4

It is where a specific amount of antibiotic is prepared in a decreasing concentration in broth by SERIAL DILUTION technique, and a standard amount of the test organism is inoculated

Answer 4

Broth dilution method

Question 5

Absence of turbidity of broth signifies:
A. Bacterial growths
B. Inhibition of bacterial growth by the antibiotics being tested

Answer 5

B.

Question 6

What is the preferred method for broth dilution method

Answer 6

Serial twofold-dilution concentrations (ug/mL)

Question 7

What is the standard inoculum size for broth dilution method

Answer 7

5 x 10^5 CFU/mL

Question 8

It can be used to determine MIC and MLC concentrations

Answer 8

Broth dilution method

Question 9

Used to improve detection of oxacillin-resistant staphylococcus

Answer 9

MH broth with 2% NaCl

Question 10

Used for streptococci and Neisseria meningitidis

Answer 10

MH broth with 2% to 5% lysed horse blood

Question 11

The lowest concentration of the antimicrobial agents needed to kill the bacterial growth

Answer 11

Minimum bactericidal concentration (MBC)

Question 12

This refers to the concentration of an antimicrobial agent that coincides with a susceptible or intermediate MIC breakpoint for a particular drug

Answer 12

Breakpoint (cutoff)

Question 13

Involves heavy bacterial growth at lower concentrations followed by one or more wells that show greatly reduced growth in the form of a small button or a light haze

Answer 13

Trailing growth

Question 14

1) involve growth at higher concentrations and no growth at one or more of the lower concentration
2) may indicate contamination, improper incubation, improper concentration of the antimicrobials and presence of unusual resistant isolate

Answer 14

Skipped wells

Question 15

1) used to test multiple organisms
2) antimicrobial solution are brought together on a molten and cooled culture
3) to test anaerobes and N. gonorrheae
4) used for research studies

Answer 15

Agar dilution method

Question 16

Has tendency to lyze in broth media, resulting in false-susceptibility

Answer 16

Neisseria gonorrheae

Question 17

Media for anaerobes

Answer 17

Brucella-laked sheep blood (Wadsworth method)

Question 18

Susceptibility medium for agar dilution method (2)

Answer 18

1) MHA (aerobes)

2) MHA + 5% sheep blood (fastidious bacteria)

Question 19

Standard inoculum size for agar dilution method

Answer 19

1 x 10^4 CFU/mL

Question 20

Incubation condition for agar dilution method used for anaerobes

Answer 20

35 degrees Celsius for 48 hours

Question 21

Shelf like of agar dilution plate

Answer 21

1 week (for most antimicrobial agents)

Question 22

Can isolate 32 different organisms

Answer 22

Agar dilution method

Question 23

Best medium for routine susceptibility testing of nonfastidious bacteria

Answer 23

MHA

Question 24

Reasons why MHA is the best medium? (3)

Answer 24

1) show acceptable batch-to-batch reproducibility for susceptibility testing
2) it is low in sulfonamide, trimethoprim, tetracycline inhibitors
3) supports satisfactory growth of mosey nonfastidious pathogens

Question 25

What is the significance of Antimicrobial Susceptibility Testing

Answer 25

Determine whether growth of the bacterial ISOLATE will be inhibited by the desired antibiotics, or it will develop resistance