When performing a sanitation validation exercise using either ATP or Microbe enumeration what microbe would be recommended as the marker for the validation of the sanitation process? e.g. if we use the definition of sanitized that would require a reduction of 99.9% (log 3) of microbes, therefore it is assumed that a control substrate surface is used (e.g. 10 cm x 10 cm) and is spiked with a known microbe and there is a known starting enumeration. After spiking a second substrate surface and performing the sanitation process and enumeration could then establish if we have a reduction of 99.9% (log 3) and could verify the sanitation process is effective. However, if no spiking occurred prior to the sanitation process and ATP or microbe enumeration was done afterwards there is no guarantee that the substrate had anything on it and thus the sanitation can't be proven to be effective. Can we get advice on what method to validate the sanitation process can be used given we need to prove a 99.9% reduction? TIA