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Biofilms with Listeria pose persistent threat in food production

It doesn’t matter how big or influential a company is, bacteria and biofilms don’t discriminate between multinationals like Dole with its tens of thousands of employees and operations like Hudson Valley Farms, where 10 or fewer people work.

Both of those companies have had close encounters with Listeria, which ongoing research is showing can be even tougher to kill than previously thought. When the microorganism has time to set up housekeeping in a biofilm in crevices on equipment or around drains and cracks in floors it is even more difficult to evict.

sponsored content Miceros biofilm listeriajpgThe consequences of so-called resident bacteria in a food production or packing facility are strong enough to rock a big ship like Dole and far-reaching enough to send ripples out from a small operation like Hudson Valley Farms across the nation as multiple companies initiate recalls because of potentially contaminated ingredients.

Dole is being investigated by the U.S. Department of Justice after bagged salads from its Springfield, OH, plant sickened at least 33 people in the U.S. and Canada in 2015 and 2016 developed infections from the same strain of Listeria monocytogenes that was found at the plant.

Hudson Valley Farms, based in New York with a production plant about two hours north of New York City, produces nuts and nut butter products. Listeria in its plant is behind at least three of seven product recalls in recent days. As of the posting of the recalls this past week, no illnesses had been reported in connection to the granola, protein bars and other foods recalled because Listeria was found in the Hudson Valley Farms facility.

The Centers for Disease Control and Prevention estimate that annually 1,600 people in the United States develop listeriosis from eating food contaminated with Listeria monocytogenes. About 260 of them die. It is particularly dangerous for the elderly, children and pregnant women, and it can be difficult to diagnose because it can take 70 days after exposure for symptoms to develop.

The 2011 outbreak of listeriosis linked to Listeria on whole, fresh cantaloupe from Jensen Farms in Colorado sickened at least 147 and killed at least 33, according to the CDC. It also bankrupted the family farm where the cantaloupe were grown because the Listeria was traced to its packing shed.

Helping the Listeria bacteria maintain a hold on surfaces such as packing tables, conveyor belts and food processing equipment, biofilm provides the microscopic bugs get comfortable and reproduce.

Biofilm formation involves a multi-step process that includes electrostatic forces, complex polymers and extracellular polymeric substances. The process results in a microscopic layer of adhesive that allows bacteria to stick to equipment and other surfaces safely.

The result is a metropolis for pathogens. The proteins, nucleic acids and lipids in biofilms give a superstructure to the bugs, with scaffold formation and highly permeable water paths. The paths allow newborn bacteria to travel to other nooks and crannies in equipment and on food-contact surfaces.

Enter the emerging weapon of choice against Listeria — bacteriophages. Often referred to as simply phages, bacteriophages are basically viruses that infect bacteria.

Research is showing that phages are more efficient than traditional sanitizers. Unlike the traditional sanitizers, phages are not affected by food debris, which can interact with oxidizing sanitizes and weaken their effect.

Phage sanitizers are not neutralized by the proteins in biofilms, making it possible for them to pierce the outer layers of biofilms to get to the bacteria below.

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