I agree with 3F. You need to do some quantitative measurements. When taken from the sea, L.mono should be negative. The contamination source is sadly the subsequent "environment". Plus opportunities for bacterial multiplication.
FDA and U.S. Department of Agriculture’s L. monocytogenes risk assessment indicates that approximately 8% of raw seafood are contaminated with from 1 to 1000 colony forming unit (CFU)/g and that approximately 91% are contaminated at less than 1 CFU/g. Less than 1% of raw seafood are contaminated at levels greater than 1000 CFU/g and none at levels greater than 10^6 CFU/g.
IMEX the 8% is probably optimistic but will vary with the product / presentation / specific environment / supply chain.
I hope that yr Product Specification does not claim something like "L.mono undetected in 25g" since IMEX that will be simply unrealistic and likely to be disproved.