Question

CFUs on TSA

Rep 1 275

Rep 2 250

Rep 3 200

AVE 241.6

SE

If you used the same media for each sample, the same incubation parameters, the same sampling and manipulation protocol, and plated the same volume of solution for each sample, then why aren’t the CFUs counted for each rep the same? Provide two reasons.

Answer 1

Answer:

why aren’t the CFUs counted for each rep the same? Provide two reasons.

CFU counts for each replicate are not same because of the following reasons:

• Sampling variability could result in a difference in CFU counts
• Counting errors can also contribute to difference in CFU counts in replicate samples
• Growth dynamics of microorganisms has intrinsic variability and that can contribute to differences in CFU count.
• Variabilities in incubation temperature of incubators at different regions can also contribute to a variability in growth and hence CFU counts.