UGA scientists have found bacteria that kill listeria in processing plant floor drains, where the pathogen is known to settle and multiply.
“There are just a few thousand cases of listeria in humans each year,” said Michael Doyle, a microbiologist and director of the UGA Center for Food Safety in Griffin. “But, of those, about 500 die. That’s a high mortality rate, and that’s why listeria infections are a major concern.”
Pregnant women, cancer patients and transplant patients are among the most frequent known cases.
“Listeria strikes these immunocompromised populations hardest,” Doyle said.

The U.S. Department of Agriculture identifies luncheon meats as high-risk products for listeria infections, Doyle said. Sliced turkey deli meats are high on the list.
To help fight it, representatives of the processed meat industry asked Doyle and his UGA colleagues to help find a solution.
“Listeria can be widely distributed in processing plants,” Doyle said. “It grows where there is water in areas like floor drains, where listeria can set up a home.”
Unfortunately, floor drains are one of the toughest areas to effectively clean and treat for listeria in processing plants.
According to Doyle, a biofilm, or slime layer, develops in floor drains over time. This layer protects the listeria from typical cleaners and sanitizers.
Knowing this, Doyle took a fight-fire-with-fire approach to killing the drain-dwelling listeria. He uses the same technology he developed for controlling E. coli and Salmonella.
With the help of the plant operators, biofilm samples were taken from dairy, poultry and infant food processing plants with little to no history of listeria. The scientists found nine different bacteria from biofilms that were highly effective in competing with and killing listeria.
From the samples collected, the researchers chose two strains that could grow with listeria and ultimately out-compete the pathogen.
The researchers then tested these two strains in a fresh poultry-processing plant. Working with Ecolab Inc., UGA scientists used a foaming agent to apply the bacteria to drains.
The drains were monitored for more than three months. The foam-biofilm mixture eliminated listeria in most drains to undetectable numbers for several weeks. The UGA researchers then tested the bacteria mixture in a ready-to-eat deli meat processing plant.
The listeria numbers are much lower in these plants than in fresh meat plants. Six drains were treated, and two were used as natural control drains. After eight weeks, scientists found five of six treated drains were free of detectable listeria.
Ecolab has licensed this technology from UGA and is developing a formulation that will be further tested. The company intends to make the product available after regulatory review and approval.
(Thanks to Sharon Omahen, UGA CAES News Editor.)
Billy Skaggs is Hall County extension agent. He can be reached at (770) 531-6988.