How to enumerate the microorganisms present in a sample?

  1. If the sample is solid, a first homogenisation step is required to prepare a 1/10 dilution.
  2. Once the sample is suspended or if the sample is liquid, serial dilute it with Dilucup®
  3. Plate 1 mL of the selected suspension(s) and incubate them.
  4. Count the colony-forming unit (CFUs). Remember that the plates should have between 30 and 300 CFUs to get a statistically valid result.
  5. Divide the average number of CFUs per the dilution level to get the number of microorganisms per mL or g in the original sample.