Tag Archives: #listeria

All in the Family: Cornell Adds Five Species To Listeria Genus (Biology)

Gather the listeria clan. It’s time for a bacterial family reunion.

While examining the prevalence of listeriain agricultural soil throughout the U.S., Cornell food scientists have stumbled upon five previously unknown and novel relatives of the bacteria, according to new research published May 17 in the International Journal of Systematic and Evolutionary Microbiology.

The discovery, researchers said, will help food facilities identify potential growth niches that until now, may have been overlooked – thus improving food safety.

“This research increases the set of listeria species monitored in food production environments,” said 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.”

One of the novel species, L. immobilis, lacked motility, or the ability to move.  Listeria move a lot. Among scientists, motility was thought to be common among listeria closely related to L. monocytogenes, a well-known foodborne pathogen – and used as a key test in listeriadetection methods. This discovery effectively calls for a rewrite of the standard identification protocols issued by food safety regulators, Carlin said.

As listeriaspecies 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.

Listeria 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 the U.S. Food and Drug Administration.

The Centers for Disease Control and Prevention estimate that 1,600 people in the U.S. get listeriosis annually and nearly 260 die.

While consumers in the grocery aisles may not notice the difference, professionals checking daily for pathogens now will have more tools.

“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,” said co-author Martin Wiedmann, Ph.D. ’97, the Gellert Family 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 listeria monocytogenes,” Wiedmann said, “and not misidentifying it as something else.”

In the research, the Wiedmann group collected soil samples from all over the United States and agricultural water samples from New York state. From the soil and water, they found 27 listeria isolates that could not be classified to the species level, so the lab conducted whole-genome sequence-based tests and showed these new species formed five novel distinct clusters.

After naming L. immobilisto reflect this organism’s non-motile characteristic, three of the other species were named to honor other listeria researchers:

  • L. cossartiae for Pascale Cossart, a bacteriologist at the Pasteur Institute of Paris;
  • L. farberi for Jeff Farber, a microbiologist at the at the University of Guelph, Canada; and
  • L. portnoyii for Daniel Portnoy, a microbiologist at the University of California, Berkeley.

The species L. rustica was taken from the Latin word “rusticus” and signifies its rural origin. 

Since 2010, 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,” Wiedmann said. “You need to tell the good guys from the bad guys.”  

In addition to Carlin and Wiedmann, the other authors for the new paper are Jingqiu Liao, Ph.D. ’20, Columbia University; Dan Weller, Ph.D. ‘17, SUNY College of Environmental Science and Forestry; Xiaodong Guo, research technician; and Renato Orsi, Ph.D. ’08, senior research associate.

Research funding was provided by the Center for Produce Safety from the Florida Department of Agriculture and Consumer Service Specialty Crop Block Grant Program.

Featured image: Listeria cossartiae, shown above, is named for Pascale Cossart, a bacteriologist at the Pasteur Institute of Paris. © Catharine Carlin/Cornell University

Reference: Catharine R. Carlin, Jingqiu Liao, Dan Weller, Xiaodong Guo1, Renato Orsi, Martin Wiedmann, “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), 2021. Link to paper

Provided by Cornell University

Bioengineered Probiotic Could Prevent Listeria Infections (Medicine)

For pregnant women, the elderly and those with weakened immune systems, listeriosis is a serious foodborne illness often linked to deli meats, fresh produce and dairy products. Even with antibiotic treatment, listeriosis is fatal for about 20 percent of patients, resulting in thousands of deaths annually.

Bioengineered lactobacillus (red) interacts with surface heat shock protein 60 (white, yellow arrows), blocking Listeria monocytogenes (green, white arrows) from crossing into the bloodstream. Credit: Rishi Drolia and Arun Bhunia

Purdue University’s Arun Bhunia, a professor of food science, and postdoctoral researcher Rishi Drolia have developed a probiotic that could prevent infections in at-risk populations. A bioengineered version of Lactobacillus, a bacterium common in the human gut, can block the pathway the Listeria monocytogenes bacteria use to cross intestinal wall cells into the bloodstream, his team reports in the journal Nature Communications.

“The Lactobacillus bacteria we developed seeks out the same proteins as Listeria monocytogenes in the gut. When it attaches, it blocks the roadway for Listeria,” Bhunia said. “This could be included in probiotic yogurts, capsules or gummies and used as a preventive measure to treat people who are at high risk of infection.”

In a previous study, Bhunia’s and Drolia’s work showed how Listeria crosses the epithelial barrier, a wall of cells in the gut that generally protects the bloodstream from harmful pathogens. A protein in Listeria, called Listeria adhesion protein (LAP), interacts with heat shock protein in those epithelial cells and forces the cells apart. That gives Listeria access to the bloodstream.

Bhunia’s team has now isolated the Listeria adhesion protein from nonpathogenic strains of the listeria bacterium and added it to the Lactobacillus to make a probiotic. When introduced to human gut cells and in mice, the Lactobacillus probiotic stably colonized the intestine and attached to epithelial cells on the heat shock protein. When pathogenic Listeria was introduced, it wasn’t able to attach to those gut cells and invade the bloodstream.

“This novel approach of engineering a probiotic strain with an adhesion protein from a nonpathogenic bacterium to exclude a pathogen significantly enhances the prophylactic use of such bioengineered probiotic bacteria without raising serious health or regulatory concerns and, thus, their potential as preventive agents against listeriosis,” the authors wrote. “This study, thus, provides the first and direct evidence that rational engineering of probiotic strains allows them to outcompete and diminish the colonization of the pathogens by competing for the receptor binding adhesion sites.”

The Lactobacillus probiotic could also have potential for other gut illnesses such as celiac disease or inflammatory bowel disease.

“We’ve seen evidence that the same proteins Listeria adheres to are overactive in these other illnesses,” Drolia said. “The probiotic has an anti-inflammatory effect and colonizes the gut for a week or more at a time. We’re interested in seeing how this could improve the lives of patients suffering from a variety of gut-related illnesses.”

Bhunia has applied for a patent for the bioengineered Lactobacillus probiotic and envisions licensing the technology.

“We’re also interested in using this model to look at other pathogenic bacteria such as E. coli or Salmonella,” Bhunia said. “If we can engineer bacteria properly, we may be able to use this technology to prevent a wider range of foodborne illnesses.”

References: Rishi Drolia et al. Receptor-targeted engineered probiotics mitigate lethal Listeria infection, Nature Communications (2020). DOI: 10.1038/s41467-020-20200-5

Provided by Purdue University