According to the USDA FSIS Listeria Guidelines, non food contact surface swabs for Listeria are not required and any positives do not render the product adulterated. In the document it states that cooling units, ceilings, walls, floors, drains are all non food contact surfaces.
If a swab from a ceiling or cooling unit (above product contact surfaces) is positive, this would not need to be reported to USDA FSIS as the swabs are not required and the product does not contact these areas. Correct?
I'm not in USA but I'll start the ball rolling.
I presume this is RTE product.
I presume the relevant reference is this attachment, esp Pg 3-12.
I cannot see any comment in the FSIS document regarding reporting anything to FSIS so i assume that yr OP query comes from some other (mandatory?) arrangement ? Within any Listeria Program, some documented "follow-up" to a positive Listeria finding (anywhere) would presumably be expected by a Regulatory body.
From a purely sanitation POV the risk assessment of yr hypothesised finding particularly relates to the potential for direct/indirect cross-contamination as discussed in the attachment. Insufficient details to say much more, clearly whether in the post-lethality area is of immediate interest.