While examining the prevalence of Listeria in agricultural soil throughout the U.S., scientists at Cornell University in New York City have stumbled upon five previously unknown and novel relatives of the bacteria. The discovery, researchers say, will help food facilities identify potential growth niches that, until now, may have been overlooked, which could improve food safety.
The research was published May 17, 2021 in the International Journal of Systematic and Evolutionary Microbiology.
“This research increases the set of Listeria species monitored in food production environments,” says lead author Catharine R. Carlin, a doctoral student in food science. “Expanding the knowledge base to understand the diversity of Listeria will save the commercial food world confusion and errors, as well as prevent contamination, explain false positives, and thwart foodborne outbreaks.”
Detection Methods for Listeria May Need to Be Overhauled
One of the novel species, L. immobilis, lacked motility. Motility has previously been thought to be common among Listeria closely related to L. monocytogenes and used as a key test in detection methods. This discovery effectively calls for a rewrite of the standard identification protocols issued by food safety regulators, Carlin says.
As Listeria species are often found co-existing in environments that support the growth of L. monocytogenes, food facilities will monitor for all Listeria species to verify their sanitation practices.
L. monocytogenes can have profound pathogenic influence on food processing plants and those plants must be kept clean. Listeriosis has a mortality rate of 20% to 30%, even with a patient taking antibiotics, according to FDA. The Centers for Disease Control and Prevention estimate that 1,600 people in the U.S. get listeriosis annually and nearly 260 die.
“This paper describes some unique characteristics of Listeria species that are closely related to L. monocytogenes, which will be important from an evolutionary perspective and from a practical standpoint for the food industry,” says co-author Martin Wiedmann, PhD, a professor in food safety and food science. “Likely, some tests will need to be re-evaluated.”
Understanding the different Listeria species is key to comprehending their similarities. “This will help us to get better about identifying L. monocytogenes,” Dr. Wiedmann says, “and not misidentifying it as something else.”
Since 2010, Dr. Wiedmann’s research group has discovered 13 of the 26 species classified in the genus Listeria. “When you’re inspecting the environments of food processing plants or restaurants, you need to know the pathogenic Listeria from the non-pathogenic species,” he says. “You need to tell the good guys from the bad guys.”
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