Question

How much supernatant should be left in the tube to resuspend the sediment prior to microscopic evaluation?

a. 0.25 to 0.75 mL
b. 0.5 to 1 mL
c. 2.5 to 3 mL
d. 1.5 to 2 mL

Answer 1

When resuspending sediment prior to microscopic evaluation, you should leave a supernatant volume of 0.25 to 0.75 mL after centrifugation. The correct option is a.

Step-by-step explanation:

To resuspend the sediment before microscopic evaluation, it is recommended to leave a supernatant volume between 0.25 to 0.75 mL.

The supernatant volume plays a critical role as it provides enough fluid to effectively mix and suspend the sediments, allowing for an accurate assessment of the sample under the microscope.

This process is crucial to maintain consistent sample concentrations, particularly when performing microbiological assays such as those for determining the number of colony-forming units (CFU) per mL.

A microcentrifuge may be used to perform the centrifugation at the required speeds, thus separating the supernatant from sediment. Option a. is the correct one.