FDA Opens Investigation into Listeria Outbreak with 11 Cases Linked to Unidentified Food

The United States Food and Drug Administration (FDA) published on September 30, in its table of investigations of outbreaks of foodborne illnesses, a new investigation into Listeria monocytogenes with 11 cases of illness. The entry is listed as active and in progress, and the associated product is listed as still unidentified. The agency reported that it has already begun origin tracing, that is, reconstructing the distribution chain to find the food the patients share.

At this early stage, the FDA has not disclosed data such as affected states, hospitalizations or deaths in the table, nor has it published a consumer advisory with specific recommendations. It is common for these data to be completed when the genetic analyses of the isolates, carried out by public health laboratories, confirm that the cases are related to each other and that the suspect food is identified.

Listeriosis is of concern because the bacterium survives under refrigeration, can remain for months on the surfaces of processing plants and causes serious symptoms in pregnant women, newborns, older adults and immunocompromised people. Outbreaks are usually linked to ready-to-eat foods, such as cold cuts, cheeses, deli products, and prepared salads, where there is no subsequent cooking step to eliminate the microorganism. The same FDA table maintains another Listeria investigation open with 44 cases, published on September 23.

For TAAG, the episode reminds us that systematic environmental monitoring is the most effective defense against Listeria monocytogenes in ready-to-eat food plants. Frequently swabbing drains, equipment and contact surfaces, and confirming the presence of the pathogenic species with real-time PCR, makes it possible to detect a persistence niche before the product reaches the market and before a public health investigation reaches the plant's door.