What is a CFU?
CFU (colony-forming units) is a unit of measurement used to estimate the number of viable bacterial colonies that form on a petri dish.
Viability is an organism's ability to reproduce. CFU is calculated by counting the number of viable colonies that form on a petri dish.
Colonies are only visible if they have reproduced significantly which implies that the sample is both viable and healthy. Once a plate has visible colonization, the CFU can be calculated for that sample.
How to Measure CFU