Study finds that cultures can protect from foodborne pathogens in cheese

A recent study published in LWT, found that bacterial cultures, known as protective cultures, can fight pathogens and prevent them from causing illness by hampering their ability to infect someone at several key points.

Protective bacterial cultures are commercially available and are designed to control undesirable microbes in foods, including foodborne pathogens such as Listeria monocytogenes. 

This study titled “Effect of pre-exposure to protective bacterial cultures in food on Listeria monocytogenes virulence” led by Dennis D’Amico, associate professor of dairy foods in the College of Agriculture, Health and Natural Resources at the University of Connecticut, investigated the ability of three commercial protective cultures to survive human gastrointestinal conditions and exert anti-infective properties against Listeria monocytogenes.

“It’s a huge risk because if there are pathogenic bacteria in raw milk and you make cheese from that milk, they can propagate and that can cause illness,” D’Amico told UConn Today.

Cheese is free of most preservatives found in other foods which leaves it vulnerable to hosting pathogens. Federal regulations dictate that cheese producers cannot use the kinds of additives found in foods like deli meats to counteract this danger. One thing they can use, however, is bacterial cultures.

D’Amico tested three commercially available strains so it would be easy for cheesemakers to adapt to the studies’ findings.

“Producers are trying their best to make safe products,” D’Amico says. “But their hands are kind of tied without solutions like this.”

According to Anna Zarra Aldrich of UConn Today, bacteria cultures compete with each other when grown in the same environment. When a pathogenic bacterium detects the presence of another bacteria, it focuses on expressing genes important to surviving the competitor and turns off many functions that cause human illness.

In order to get sick from eating something contaminated with Listeria, the pathogen needs to survive the inhospitable environment of the gastrointestinal tract and then attach to colon cells. Finally, it needs to enter those cells and cross the epithelial cell lining. Disrupting any of these steps will help prevent illness even if the pathogen doesn’t die.

D’Amico found protective cultures were effective at stopping Listeria at key points in the infection process. Two of the three cultures disrupted Listeria’s ability to survive the gastrointestinal tract.

There was not a significant impact on the pathogen’s ability to adhere to cells. However, two significantly reduced the pathogen’s ability to invade colon cells and all three cultures disrupted transepithelial translocation, where the pathogen crosses the epithelial barrier by moving between the cells.

The full study can be viewed here.

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