Listeriosis Outbreak Linked to Vegan Cheese

An outbreak of listeriosis in several European countries was linked to vegan cheese made from raw nut milk, researchers reported.

The outbreak occurred between April and December 2022 and involved eight people in France, Belgium, Germany, and the Netherlands, detailed Marc Lecuit, MD, PhD, of the Institut Pasteur in Paris, and colleagues in a correspondence to the New England Journal of Medicine.

This is the first time that vegan cheese products have been associated with Listeria monocytogenes, Lecuit told MedPage Today in an email.

L. monocytogenes "can contaminate vegetables such as nuts used to make these vegan cheese substitutes, which are typically not pasteurized or sterilized during processing," Lecuit said, noting that a recent study found that nut-based milk alternatives are actually more conducive to growth of L. monocytogenes than bovine milk.

A spokesperson from the FDA confirmed with MedPage Today that they have "not yet detected an outbreak of L. monocytogenes with a link to vegan/plant-based cheese in the United States," but that there have been a few outbreaks of Salmonella associated with cashews or cashew products. For example, in 2021, a multistate outbreak of Salmonella was linked to raw cashew brie.

In the European listeriosis outbreak, four pregnant women in France presented with preterm deliveries (median gestation of 32 weeks) and a 38-year old person with compromised immune function developed meningoencephalitis. The other cases included a 3-year-old child in Belgium, a person in Germany who developed pregnancy-associated sepsis, and a maternal-neonatal case of neonatal meningitis in the Netherlands.

L. monocytogenes clinical isolates from the affected individuals were found to be genetically related to those from vegan cheeses and their production environment. Moreover, all affected people had exposure to the vegan cheeses, Lecuit and colleagues wrote. This prompted a product recall and a health advisory issued by the French government warning consumers about the risk of listeriosis from vegan cheeses.

In recent years, listeriosis outbreaks in the U.S. have been associated not only with soft dairy cheeses but also with a wide variety of other foods, including deli cheeses and meats, ice cream, fruits, packaged salad greens, enoki mushrooms, and cooked chicken.

Lecuit said that vegan cheese products are often touted as an alternative to dairy products for pregnant people and others at highest risk for listeriosis, who are advised to avoid unpasteurized soft dairy cheeses, such as queso fresco or brie.

"In general, current medical recommendations for pregnant women ... do not cover these vegan cheese products," Lecuit pointed out. The CDC does not specifically mention raw nut-based cheeses or raw nut milks as foods people at high risk for listeriosis should avoid.

"This report will help professionals be aware of this risk and inform their patients. It will also hopefully alert vegan food producers of the risks associated with Listeria monocytogenes," Lecuit said.

In the European Union, "vegan cheese substitutes are already covered by food safety criteria in European regulations," Lecuit said, "but the reported outbreak for a new food product has highlighted to food business operators the reality of this new risk and the need to adequately consider the microbiological hazard of Listeria monocytogenes."

The U.S. Department of Agriculture requires that all almonds to be consumed in the U.S. must be pasteurized and all commercial plant-based non-dairy beverages must be pasteurized or ultrapasteurized. However, products made from raw nuts or raw nut milks still pose a risk of bacterial contamination. Also, pasteurization kills L. monocytogenes and other bacteria but even pasteurized products can be a source of infection if production areas are contaminated.

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