Have you confirmed with the lab what <100 actually means?
This could mean that the count is actually 1 which is <20. It will depend on how the lab is processing/diluting the samples in order to plate out and incubate the plates.
If they are making an initial 1:100 dilution and plating this then any plate with no growth would be reported as <100 given the initial product dilution.
Speak to the lab and find out the dilution process - you may want to ask them the run a 1:10 plate which will give you results that you can relate to your specification
Edited by SpursGirl, 30 October 2014 - 12:54 PM.