What is the term used for plate counts below 30 colonies?

The term used for plate counts below 30 colonies is "Too few to count" (TFTC). This designation indicates that the number of colonies is insufficient to provide a statistically reliable estimate for the population within the sample being tested. Plate counts typically rely on having a sufficient number of colonies to ensure accuracy when calculating concentrations, and when counts fall below 30, variability becomes too high to yield meaningful data.

Establishing a range for counts is essential in microbiology for assessing the health and quality of samples. Counts that are categorized as too few to count signify that the sample may need further dilution or a different method of quantification to achieve a more accurate bacterial population estimation. This understanding is critical for interpreting results in both research and clinical microbiology contexts.