1. AST

Question 1

3 purposes of AST standardization?

Answer 1

1. Optimizes growth conditions
2. Optimizes antimicrobial integrity + activity
3. Provides reproducibility + consistency

Question 2

Approx. cell density of 0.5 McFarland standard?

Answer 2

1.5 x 10^8 CFU/mL

Question 3

2 chemicals used to prepare McFarland standards

Answer 3

1% sulfuric acid

1% barium chloride

Question 4

Growth method/log-phase is never used for this organism

Answer 4

Staph - due to MRSA

Question 5

Volume of each of the McFarland standard components?

Answer 5

BaCl2 - 0.05 mL

H2SO4 - 9.95 mL

Question 6

Storage conditions for McFarland standards?

Answer 6

• Tightly sealed
• In the dark
• 20-25 degC
  <= 6 months shelf life