Why are my bacteria results reported as "Too numerous to count (TNTC)"?

Created by: Andrew White

Modified on: Wed, 30 Jan, 2019 at 12:55 PM


When determining a concentration of microorganisms within a test sample using a technique which involves counting individual bacterial  colonies or colony forming units (CFU) on a test plate, there is a possibility that the concentration observed on the test plate may exceed the upper countable limit of the test. 


In such situations where a value cannot be  provided the result may be reported as Too Numerous to Count, or TNTC. 


In some regions a greater than result might be reported for this scenario.  For example >200 CFU/100 mL is used to indicate an over populated plate count where the upper countable limit can not be determined.


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Andrew is the author of this solution article.

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