What is the countable range for a viable plate count?

The viable plate count method is a widely used technique in microbiology to estimate the number of viable bacteria in a given sample. The countable range for a viable plate count is typically between 30 and 300 colony-forming units (CFUs) per plate. This range is considered ideal because it provides enough colonies to ensure statistical reliability while still being manageable to count.

Counts below 30 may lead to inaccuracies due to sampling error and a lack of statistical robustness, and counts exceeding 300 can lead to overcrowding on the agar surface, which may inhibit colony growth and prevent the identification of individual colonies. This balance ensures that results are reproducible and reflect true population density. Thus, the range of 30-300 is the standard for determining the viability of bacterial populations in a sample accurately.