Most probable number (MPN) method

Definition

The Most Probable Number (MPN) method is a statistical technique used to estimate the number of viable microorganisms in a sample. It is particularly useful for samples with low concentrations of bacteria.

5 Must Know Facts For Your Next Test

1. MPN is based on the principle of dilution and relies on probability theory.
2. It involves inoculating multiple tubes with serial dilutions of a sample and incubating them to observe microbial growth.
3. Results are interpreted by comparing the number of positive tubes at each dilution level against standard MPN tables.
4. The MPN method is commonly used for water quality testing, especially to detect coliform bacteria.
5. One advantage of MPN over direct counting methods is its ability to detect very low levels of microorganisms.

Review Questions

Related terms

Serial Dilution: A stepwise dilution of a substance in solution to reduce concentration.

Coliform Bacteria: A group of bacteria commonly found in water that are used as indicators of sanitary quality.

Viable Count: A measurement of the number of living microorganisms in a sample.