The U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA-FSIS) has reissued its guidance, titled, Testing for Non-Listeria Monocytogenes Listeria Species.

The reissued guidance reflects expansions made to the agency’s testing method and enforcement actions regarding Listeria in ready-to-eat (RTE) foods production facilities. These changes were made in January 2025 as a result of a review of USDA’s Listeria Rule and inspection procedures following a fatal, multistate listeriosis outbreak linked to Boar’s Head-brand deli meats, which revealed gaps in the agency’s oversight of RTE facilities.

The reissued guidance continues to instruct inspection program personnel (IPP) that USDA-FSIS changed its laboratory method to include testing for Listeria species other than L. monocytogenes in all sampling projects that currently test product, food contact surface, or environmental samples for Listeria monocytogenes in facilities producing RTE meat, poultry, or egg products. Specifically, USDA-FSIS reports L. monocytogenes as well as the names other Listeria species identified by the method when any of the following more common species are detected: L. aquatica, L. booriae, L. cornellensis, L. costaricensis, L. fleischmannii, L. floridensis, L. grandensis, L. grayi, L. innocua, Listeria ivanovii, L. newyorkensis, L. riparia, L. rocourtiae, L. seeligeri, L. weihenstephanesis, and L. welshimeri. When the agency identifies Listeria but the method cannot confirm the name of the species, it will report the result as indeterminant.

USDA-FSIS is testing for additional Listeria species because these results provide more information about the effectiveness of the establishment's sanitation program. According to the agency, if sanitation is effective, no type of Listeria should be found in product, on food contact surfaces, or on environmental/non-food contact surfaces in the post-lethality exposed RTE environment.

The notice also instructs IPP on the actions to take in response to a Listeria-positive sample (species other than L. monocytogenes) in a RTE meat, poultry, or egg product sample, and instructs Enforcement, Investigations, and Analysis Officers (EIAOs) on the actions to take in response to a positive sample.