Fighting foodborne illness with bacteria

Harsh Bais (right), an associate professor of plant and soil science at UD's Delaware Biotechnology Institute, and KalI Kniel, a professor of animal and food sciences, stand in the greenhouse where they are studying a bacteria that could prevent harmful pathogens like listeria from being absorbed in leafy greens.(Photo: SUCHAT PEDERSON/THE NEWS JOURNAL)

Foodborne illnesses pose a serious health concern for consumers and a potentially devastating risk to the companies associated with outbreaks.

Texas ice cream maker Blue Bell Creameries reportedly laid off 37 percent of its workforce earlier this year after a deadly listeria outbreak linked to its frozen treats resulted in three deaths.

Meanwhile, Chipotle Mexican Grille has seen its stock and store sales tumble as an outbreak of E. coli expands to nine states, sickening more than 50 people.

Those high-profile cases only scratch the surface.

The U.S. Centers for Disease Control and Prevention estimates foodborne illness sickens as many as 1 in 6 Americans every year. While most of those cases are mild, tainted food is linked to 3,000 deaths and more than $80 billion a year in medical bills and corporate losses.

The U.S. food chain may be one of the safest in the world, but federal regulators say outbreaks appear to be rising, even with the addition of enhanced food safety regulations and handling protocols.

That’s partly because those with compromised immune systems, who are most susceptible to outbreaks, are living longer. But it’s also because new pathogens are emerging as consumers demand year-round produce, often without the processing that kills harmful microorganism.

The rise of massive agriculture operations – from farms to packing houses – also can contribute to those disease-causing organisms reaching more consumers.

“Large distribution chains do allow for more chances of contamination, but we have to balance that with feeding the world,” said Kali Kniel, an animal and food science professor at the University of Delaware. “Unfortunately, it’s a complex problem with no easy answers.”

Yet Kniel and other UD researchers are hopeful they may have found a new weapon to fight some of the most harmful pathogens plaguing the nation’s food supply in the form another bacteria that’s completely benign to humans.

“It’s what you might call a probiotic for plants,” said Harsh Bais, an associate professor of plant and soil science at UD’s Delaware Biotechnology Institute.

Zinnias are some of the plants used in the study of a bacteria that could prevent harmful pathogens like salmonella and listeria from being absorbed in leafy greens. (Photo: SUCHAT PEDERSON/THE NEWS JOURNAL)

The bug that Bais and Kniel are studying is a special strain of the bacteria Bacillus subtilis that UD researchers first isolated from the soil around radish roots in 2003.

Known today as UD1022, the strain is currently being licensed to a large agricultural company interested in its ability to promote growth among a wide range of crops.

By accident, Bais and his team of researchers recently discovered another trait that also could make UD1022 a promising candidate for fighting foodborne pathogens.

“A post-doc in my lab working on a big experiment was treating a plant called Arabidopsis with this particular bacteria,” he said. “It’s a needy lab rat of a plant that requires a lot of water.”

After a long weekend in which the student was unable to water her specimens, she returned to discover those treated with the bacteria were still healthy, while the control plants had become scorched and wilted.

What they found was UD1022 had somehow caused the treated plants to close their stomates, the tiny openings on the leaf surface through which plants breathe and give off water vapor.

It’s through those stomates, researchers theorize, that human pathogens like salmonella and E. coli also may infiltrate plants where they remain in hiding for several days regardless of how well the produce is washed.

Last year, Bais, Kniel and a trio of researchers embarked on a series of experiments to look at whether UD1022 could induce stomata closure in spinach and romaine lettuce, two leafy greens commonly associated with outbreaks of foodborne illness. Their work also examined how the bacteria might impact the presence of salmonella and listeria on the exterior of those vegetables.

Their findings, published earlier this year in the Journal of Foodborne Pathogens and Diseases, found UD1022 not only regulated stomata closure in both plants, but also significantly reduced the persistence of listeria within three days of application.

“We still have a lot of work left to do in terms of learning exactly how this bacteria works to accomplish those things,” Kniel said. “But what we’ve seen so far is very promising for its potential use as a bio-control agent, especially for listeria.”

The hope, according to the researchers, is that UD1022 eventually could be developed into a crop treatment that keeps produce from picking up pathogens in the days leading up to harvest, as well as a natural sanitizer that could be used to reduce listeria contamination in packing houses.

Either use could prove to be immensely valuable in terms of saving both dollars and lives.

Commonly found in soil, listeria is a relatively rare, but particularly deadly source of foodborne illness. A 2011 outbreak of the pathogen linked to cantaloupes from a single Colorado farm resulted in 30 deaths – one of the most deadly outbreaks since the CDC began tracking such statistics in the 1970s.

“We don’t think this is the only answer,” Bais said. “But it could prove to be a very valuable tool in reducing the incidence of foodborne illness when used in combination with other measures.”

Contact business reporter Scott Goss at (302) 324-2281, sgoss@delawareonline.com or on Twitter @ScottGossDel.