Question

Write the brief explanation of CFU (Colony Forming Unit) calculation with an example.

Answer 1

CFU:

• It stands for colony-forming units, a measure of viable cells or microorganisms present in a sample.
• It's calculations are commonly used in microbiology to determine the concentration of bacteria in a sample.
• To perform a CFU calculation, a sample is diluted and plated onto an agar medium. After incubation, colonies of bacteria will form on the plate.
• The number of colonies that form is counted, and the number is multiplied by the dilution factor to determine the CFU count.
• For example, let's say we have a bacterial culture and we want to determine the CFU/mL.
• We take 1 mL of the culture and add it to 9 mL of sterile diluent, giving us a 1:10 dilution.
• We then take 0.1 mL of the 1:10 dilution and add it to 0.9 mL of sterile diluent, giving us a 1:100 dilution.
• We then plate 0.1 mL of the 1:100 dilution onto an agar plate and incubate it.
• After incubation, we count 50 colonies on the plate.
• Since we plated 0.1 mL of the 1:100 dilution, we need to multiply the colony count by 10,000 to get the CFU/mL count.
• Therefore, the CFU/mL count is 50 x 10,000 = 500,000 CFU/mL.

Colony forming unit (CFU):

• In microbiology, the colony-forming unit i.e., CFU is a unit which estimates the number of microbial cells (bacteria, fungi, viruses etc.) in a sample that are viable, able to multiply via binary fission under the controlled conditions.