Enoki mushroom Listeria outbreak sickens people in 2 states

The US Centers for Disease Control and Prevention (CDC) yesterday announced a Listeria monocytogenes outbreak linked to enoki mushrooms that has hospitalized two people in two states.

Enoki mushrooms have long, thin stems and are a popular ingredient in Chinese, Japanese, and Korean food, usually eaten cooked in soups, stir fries, and hot pots. In 2020, the CDC reported the nation's first Listeria outbreak linked to enoki mushrooms imported from South Korea. Since then, federal and state officials have ramped up testing of enoki mushrooms, which has resulted in many positive samples and a number of product recalls.

In the latest outbreak, the cases were reported from Michigan and Nevada. The patients' samples were collected in the first part of October. Both are men, ages 30 and 42. Both reported eating enoki mushrooms or eating at restaurants that had menu items that contained the ingredient.

Whole-genome sequencing suggests that the patients' samples are closely related and that they probably got sick from the same food. The samples are similar to an imported November 2021 sample that triggered a product recall. However, the company at the center of that recall has not been identified as the source of the outbreak.

The CDC warned people who are pregnant, older than 65, or have weakened immune systems to avoid eating raw enoki mushrooms. It also urged restaurants not to serve raw enoki mushrooms.

In an import alert issued on Jul 1, the Food and Drug Administration (FDA) said that in fiscal year 2021, 42% of enoki mushrooms sampled from South Korea were contaminated with Listeria and that it's unlikely that contamination is an isolated incident. The FDA said enoki mushrooms may be a high-risk reservoir for Listeria owing to the difficulty of maintaining good hygiene practices at the medium-sized plants where the mushrooms are usually grown.

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