The OP query seems to focus on the disposition of the Lot of finished product which has sampled / tested positive for L.innocua.
I make no comment on the environmental sampling other than to attach one suggested Listeria system SOP below. There are many others already posted on this forum, some regulatory, some not.
I presume you already have an existing procedure in the case of detection of L.mono. in the finished product.
(It should be noted that a negative result for a particular micro.species using a sample from a given lot can never guarantee that the whole lot has zero contamination. (Sampling 101)).
AFAIK, L.innocua is not generally regarded as a significant human pathogen unlike L.monocytogenes.
Typical cooking processes should “eliminate” (inter alia) both L.monocytogenes and L.innocua if present in the raw material at “normal” levels. Testing of the finished cooked product for the above 2 species should therefore result in a finding(s) of “undetected”.
Accordingly, detection is typically assumed to imply that post-cooking contamination has occurred.
With respect to a specific Lot, I have encountered at least 3 interpretations of a positive finding such as referred in the OP –
(1) A conservative interpretation which assumes that the detection of L.innocua indicates the potential for L.monocytogenes to also be present, even if negative analytical results were obtained for the latter. Follow-up is then identical to finding a positive detection for L.monocytogenes.
(2) An interpretation based solely on compliance to the appropriate micro. specification for the product. IMEX, product specifications only reference L.monocytogenes. The typical follow-up in such a case was to further sample / check for L.monocytogenes. If negative, the product was released (with respect to L.mono). If positive, (1) was followed.
(3) As a variation on (2), the finding for L.innocua was ignored and the product released (with respect to L.mono).
The choice between options like (1-3) may well relate to the detailed context, eg product, history, local regulatory factors, buyers, contract, etc.
Listeria Mono. Control Manual,Crab.pdf 349.77KB