Question

For each set of dilutions (bleach and mouthwash), the first tube contained a 1:11 dilution (0.5 mL of agent was added to 5.0 mL of nutrient broth). What was the dilution of the MIC for the mouthwash and the bleach? Hint: You will have to calculate the dilution of each tube 2 – 4.

Answer 1

Answer:

Tube 2: 8.26 * 10^-3; Tube 4: 6.83 * 10^-5

Explanation:

In the serial dilutions for MIC test, the volume of nutrient broth in each tube should be equal: 5.0 mL. And the volume of agent in each dilution should also be similar: 0.5 mL.

The serial dilutions was as following:

• Tube 1: 0.5/5.5
• Tube 2: 0.5 mL of tube 1 was diluted with 5.0 mL broth. Then, the dilution of tube 2 is (1:11) * (1:11) = (0.5/5.5) * (0.5/5.5) = 1:121 = 8.26 * 10^-3
• Tube 3: We perform the similar calculation. Thus, the result is 1:1331 = 7.51 * 10^-4
• Tube 4: It is 1:14641 = 6.83 * 10^-5.