Antibiotic and Antimicrobial Susceptibility

Question 1

What medium is used for susceptibility testing?

Answer 1

Mueller-Hinton plates (enriched medium)

Question 2

What is 0.5 McFarland standard used for?

Answer 2

Used as a reference to adjust the turbidity of bacterial suspensions so they’re within a certain range

Question 3

Why do we adjust the turbidity of the bacterial suspension?

Answer 3

To standardize: if a suspension is too heavy or too dilute, a false resistant or susceptibility determination can occur

Question 4

What is observed if an organism is susceptible to an antibiotic/antimicrobial agent?

Answer 4

A zone of inhibition

Question 5

What is observed if an organism is resistant?

Answer 5

Growth all around/next to the disk

Question 6

What is the difference between Bacteriocidal and Bacteriostatic?

Answer 6

Bacteriocidal: kills bacteria
Bacteriostatic: prevents bacterial growth

Question 7

What Antibiotics were used for Gram + organisms?

Answer 7

Penicillin (10 units)

Erythromycin (15ug)

Question 8

What Antibiotics were used for Gram - organisms?

Answer 8

Penecillin (10 units)
Tetracycline (30ug)
Gentamycin (10ug)