A team of microbiologists from Cornell University has isolated five new non-pathogenic species of Listeria soil samples from an agricultural water sample from New York and different locations in the United States. The discovery will help food facilities identify potential growth niches that until now, may have been overlooked — thus improving food safety.
Listeria cossartiae is named for Pascale Cossart, a bacteriologist at the Pasteur Institute of Paris. Image credit: Catharine Carlin, Cornell University.
Listeria is a genus of Gram-positive, rod-shaped, facultatively anaerobic bacteria that includes over 20 distinct species.
The genus received its current name, after the British pioneer of sterile surgery Joseph Lister, in 1940.
Listeria species are known as saprophytes in soil. Several species are pathogens carried by sheep and goats.
The major human foodborne pathogen is Listeria monocytogenes. It is usually the causative agent of listeriosis, an infection caused by eating food contaminated with the bacteria.
“Our research increases the set of Listeria species monitored in food production environments,” said Catharine Carlin, a doctoral student in the Department of Food Science at Cornell University.
“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.”
The five newfound species are Listeria cossartiae, Listeria immobilis, Listeria portnoyi, Listeria rustica, and Listeria farberi.
Listeria immobilis lacked motility, or the ability to move. Other Listeria species move a lot.
Among scientists, motility was thought to be common among Listeria species closely related to Listeria monocytogenes.
“This discovery effectively calls for a rewrite of the standard identification protocols issued by food safety regulators,” Carlin said.
“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. Likely, some tests will need to be re-evaluated,” said Professor Martin Wiedmann, also from the Department of Food Science at Cornell University.
Understanding different Listeria species is key to comprehending their similarities.
“This will help us to get better about identifying Listeria monocytogenes, and not misidentifying it as something else,” Professor Wiedmann said.
“When you’re inspecting the environments of food processing plants or restaurants, you need to know the pathogenic Listeria from the non-pathogenic species. You need to tell the good guys from the bad guys.”
A paper describing the discovery was published in the International Journal of Systematic and Evolutionary Microbiology.
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Catharine R. Carlin et al. 2021. Listeria cossartiae sp. nov., Listeria immobilis sp. nov., Listeria portnoyi sp. nov. and Listeria rustica sp. nov., isolated from agricultural water and natural environments. International Journal of Systematic and Evolutionary Microbiology 71 (5); doi: 10.1099/ijsem.0.004795
