CFU vs. MPN Test Results
for Microbial Water Quality Testing

When choosing microbial water quality testing methods, there are multiple factors to consider, such as what type of water sources you are testing, what you are trying to accomplish by water testing, and what resources are available for testing.

Another important topic to decide is what type of testing methodology to use in terms of test results, namely Presence/Absence or Quantified testing methods. For a summary of these testing methodologies, see the Aquagenx technical brief Microbiological Water Quality Testing Methods for E. coli and Total Coliform Bacteria.

This technical brief will explain the differences in terms of test results between the two quantified testing methodologies, Colony Forming Units (CFU) vs. Most Probable Number (MPN).