Five New Listeria Species Discovered, Could Help Improve Food Safety

A team of food scientists from the Cornell University adds five new listeria species to the list while studying the prevalence of these bacteria in American agricultural soils.

The five new listeria species are previously unreported and described as "novel relatives" of the bacteria genus. According to the researchers, the recent discovery could help food facilities determine potential growth niches of listeria that might have remained overlooked until now. In turn, this will improve food safety.

Cornell University researchers report the five new listeria species in the article "Listeria cossartiae sp. nov., Listeria immobilis sp. nov., Listeria portnoyi sp. nov. and Listeria rustica sp. nov., isolated from agricultural water and natural environments." The new report appears in the International Journal of Systematic and Evolutionary Microbiology, May 17.

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More Species to Watch Out For Means Greater Food Safety

Catharine R. Carlin, the lead author in the new study and a doctoral student in food science at Cornell, explains that their new study effectively increases the listeria species that has to be monitored. She adds that expanding the knowledge base regarding these bacteria, further understanding the diversity of listeria as a genus, will save the world from confusion and errors brought about by these previously unknown species. This could help prevent contamination and explain false positives, preventing chances of foodborne disease outbreaks.

One of the five new listeria species, L. immobilis, was named "immobilis" for its lack of ability to move, or motility - a notable characteristic since listeria is known for moving around a lot. Before this discovery, motility was thought of as a universal trait among listeria closely related to L. monocytogenes, a known foodborne pathogen.

Additionally, this trait has been used in existing tests for detecting listeria and the L. immobilis was most likely undetectable under these tests. With the discovery, standard identification protocols used by food safety regulators and food facilities will have to be rewritten to accommodate the possibility of immobile species.

Since existing listeria species are usually found in the same environments that also allow L. monocytogenes to thrive, food facilities monitor for all known listeria species in the verification of their sanitation and food safety practices.

For food processing plants, which must be kept strictly clean, the presence of L. monocytogenes has a profound influence on the presence of pathogens.

"This paper describes some unique characteristics of listeria species that are closely related to listeria monocytogenes, which will be important from an evolutionary perspective and from a practical standpoint for the food industry," explains Martin Wiedmann, co-author of the study and a professor of food safety and food science, in a press release from Cornell University.

Wiedmann is also a part of previous studies that have led to the discovery of 13 out of 26 species currently classified within the genus listeria.

The Risks of L. Monocytogenes, a Foodborne Pathogen

The main problem with the presence of L. monocytogenes is a condition called Listeriosis. According to the Centers for Disease Control and Prevention (CDC), it is a "serious infection" usually affecting humans who eat contaminated food. It primarily affects newborns, older adults, pregnant women, and immunocompromised people, with the CDC noting that cases of listeriosis aside from these people are rare.

As for its symptoms, the CDC notes that it varies depending on the person and the affected body part. The most common are fever and diarrhea, which are common among foodborne diseases.