What is the Difference Between CFU and MPN?

The main difference between CFU (Colony Forming Units) and MPN (Most Probable Number) lies in the methods used to enumerate microorganisms in samples. Both methods are used to measure the number of viable bacterial cells or fungal cells in a given sample, but they differ in their approach and application.

CFU is determined by directly counting visible colonies of bacterial growth on a plate or film. This method is also known as the standard plate count or viable plate count. The standard unit for CFU is CFU/ml or CFU/g.

On the other hand, MPN measures growth statistically. In this method, a sample is added to a series of test tubes with special media at different concentrations. The MPN value is then measured based on the reaction levels in the tubes and the value is calculated using multiple tube fermentation method and MPN table.

Some studies have found that MPN-derived estimates are somewhat higher on average than CFU estimates, especially for certain types of bacteria like Escherichia coli. However, a strong positive relationship is generally observed between MPN and CFU estimates. Both methods are used to detect water quality and fecal indicator bacteria in water samples.

Comparative Table: CFU vs MPN

The main difference between CFU (Colony Forming Units) and MPN (Most Probable Number) lies in the methods used to calculate them. Both CFU and MPN are measures of the estimated number of bacteria in a given sample, but they are determined using different techniques.

Here is a summary of their differences:

In summary, both CFU and MPN are equivalent units that measure the estimated number of bacteria in a sample. However, CFU is calculated from bacterial and fungal colonies growing on a solid agar plate, while MPN is calculated using multiple tube fermentation and a statistical method.