June 17, 2024

Paris Researchers Find Placental Breach Mechanism for Listeria

As the deadly Listeria monocytogenes outbreaks linked to recalled caramel apples made from Bidart brothers apples, and to Queseria Bendita cheese point out, pregnant women are very susceptible to these bacterial infections. In the caramel apple outbreak, ten pregnant women were sickened; one woman suffered a fetal loss. In the Queseria Bendita cheese outbreak, one infection was associated with a pregnancy.

Listeria monocytogenes bacteriaScientists believe that the bacteria get into the placenta and hide from the mother’s immune system, letting them multiple to dangerous levels. But the placental barrier usually acts as a barrier to bacteria. What makes Listeria different?

Researchers at the Pasteur Institute in Paris have found that Listeria survives and grows within the intestinal lumen (channels in the intestines). Protein pathways are responsible for letting the Listeria monocytogenes bacteria break through barriers. The results were published in the Journal of Experimental Medicine.

Listeria bacteria use two surface proteins, called InIA and InIB, or internalins, to take them across mucosal tissue barriers. These proteins bind to receptors on cells. The host cells release enzymes called phosphoinositide 3-kinase (PI3K) that are critical to the invasion process.

In the intestines, the bacteria only need InIA to get into the lumen. But in the placenta, Listeria needs InIB to “flip a switch” and turn on the PI3K pathway. The study shows how bacterial pathogens evolved to invade human tissue. If the placental PI3K activity was somehow blocked, the placental barrier against Listeria might be strengthened.

Because pregnant women are so susceptible to infection from this bacteria, they are advised to avoid many foods that carry a higher risk of Listeria monocytogenes contamination. Those foods include deli meats, bean sprouts, hot dogs, smoked meats, raw milk and raw milk products, soft cheeses, unpasteurized cider, and undercooked and raw meat, poultry, shellfish, and eggs.

When a pregnant woman contracts a Listeria infection, she usually only has mild symptoms that are similar to the flu. Many women dismiss those symptoms because they are so mild. But listeriosis can cause miscarriage, stillbirth, and fatal infection of the newborn baby.

If you ate recalled commercially prepared caramel apples or recalled Queseria Bendita soft cheeses and sour cream and have experienced flu-like symptoms, please see your doctor immediately. Antibiotic treatment can prevent serious complications, especially if the illness is caught early.

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