We have a very extensive EMP for listeria and salmonella in our NRTE plant. We currently test Zone 2-3 but have a requirement from one of our customers to test Zone 1 for indicator organisms. I get testing for EB for E. coli, or Salmonella but wonder if there is something to indicate possible listeria? I have done a lot of web surfing but have not come up with anything yet. We do test Zone 1 with the ATP meter but that does not correlate to bacteria. Thanks for any guidance in the correct direction.