Deadly Foodborne Bacteria Found To Hide From Sanitizers

Our efforts to protect ourselves form potentially deadly bacteria may be in vain, scientists have warned.

Listeria is the third leading cause of death from foodborne diseases in the U.S., the Centers for Disease Control and Prevention Reports. Roughly 1,600 people contract serious Listeria infections every year, resulting in 260 deaths. While the illness is usually mild, Listeria bacteria can spread beyond the intestines, potentially infecting other parts of the body.

To avoid Listeria contamination, food suppliers often spray their produce with sanitizers to kill any bacteria. But, according to a new study from Penn State University, Listeria bacteria may be able to evade these sanitation protocols.

The study, published in the journal Biofilm, demonstrates how other harmless species of bacteria in the fruit-packing environment can stick together and form a protective shield, called a biofilm, around the Listeria bacteria.

"We found two groups of microorganisms in the tree fruit packing environments, Pseudomonadaceae and Xanthomonadaceae, that are very good at forming biofilms and protecting Listeria monocytogenes," co-author Jasna Kovac, a Professor of Food Safety at Penn State, said in a statement. "Biofilms represent a physical barrier that reduces the effective diffusion and antimicrobial action of sanitizers and is hypothesized to increase Listeria monocytogenes' tolerance to sanitizers used in food processing facilities."

In other words, the protected bacteria are faced with a much lower dose of sanitizer, which they can more easily tolerate.

The results highlight the need to assess how effective commonly used sanitizers are against the harmless biofilm-forming bacteria that can often be found in food processing environments.

"The findings of this research project will inform and enhance sanitation protocols and extension training efforts targeted at the tree-fruit industry to effectively control Listeria monocytogenes," co-author Luke LaBorde, a professor in food science and an expert in the tracking of Listeria monocytogenes in produce production and processing environments, said in a statement.

If you are immunocompromised, pregnant or over the age of 65, the CDC recommends avoiding foods that are more likely to contain Listeria. These include:

• Unpasteurized soft cheese—instead opt for harder cheese, cream cheese, or pasteurized soft cheese.
• Unheated deli meats—instead opt for deli meats that have been reheated.
• Cut melon that has been left out for more than two hours (or in a refrigerator for over a week) —opt for melon that has been freshly cut.
• Raw or lightly cooked sprouts—instead opt for sprouts that have been cooked until they are steaming hot.

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