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August 23, 2023
During an ongoing listeriosis outbreak investigation, Listeria monocytogenes was found in milkshakes (all flavors) sold at Frugals, a drive-in restaurant located at 10727 Pacific Ave S, Tacoma, WA 98444. No other Frugals locations (in Washington or Montana) are thought to be affected. Whole genome sequencing shows that L. monocytogenes found in the milkshakes is closely related to the L. monocytogenes that caused the six outbreak-associated infections.
Potentially contaminated milkshakes were sold prior to August 8, 2023 when test samples were collected and the restaurant discontinued use of the milkshake machines.
People aged 65 years and older and those with immunocompromising conditions are at risk for developing invasive infection, including sepsis, meningitis, and meningoencephalitis after consuming foods contaminated with L. monocytogenes. Infection in pregnancy can result in miscarriage, stillbirth, preterm labor and sepsis or meningitis in the neonate but pregnant people typically experience a relatively mild “flu-like” illness and can be asymptomatic. Older children or adults with normal immune function may have no or mild symptoms and only rarely develop invasive disease.
From CDC: Information for Health Professionals and Laboratories
This section presents a framework for assessment and medical treatment of high-risk people (pregnant women, older adults, and people with weakened immune systems) who may have been exposed to L. monocytogenes by eating contaminated foods.
The risk of invasive listeriosis after exposure to L. monocytogenes is very low; exposure is common, but disease is rare. A study related to a 2011 outbreak linked to cantaloupe estimated the attack rate at roughly 1 case per 10,000 pregnant women who ate the implicated cantaloupe.
Management of pregnant women: The American College of Obstetrics and Gynecology has issued a committee opinion on the Management of Pregnant Women with Presumptive Exposure to Listeria monocytogenes.
Management of people other than pregnant women with elevated risk of invasive listeriosis: Clinicians may consider using the framework below. This framework is not intended either as a practice guideline or as a modification of existing guidelines or practices in managing patients with confirmed or suspected listeriosis. Little scientific evidence is available to inform decisions regarding management of people at elevated risk of invasive listeriosis who have been exposed to L. monocytogenes and who are either asymptomatic or have mild symptoms that could be consistent with early Listeria infection. Therefore, this suggested framework is based on informal solicitation of experts in infectious disease, obstetrics and gynecology, and public health in 2011. Patient management decisions for asymptomatic or mildly symptomatic people are appropriately made on a case-by-case basis, informed by clinical judgment and the likelihood of exposure of the patient. Consultation with a specialist in infectious disease may be considered.
Note: The suggested framework above does not include stool culture for L. monocytogenes. Stool culture has not been evaluated as a screening tool and is not recommended for the diagnosis of listeriosis. Ingestion of food contaminated with Listeria occurs frequently because the bacterium is commonly present in the environment. Therefore, intermittent fecal carriage and shedding of Listeria is also frequent (about 5% in unselected populations, but substantial variation exists) and rarely indicative of infection. Stool culture for Listeria may also have low sensitivity and is rarely available in clinical laboratories. Serologic testing for Listeria has poor sensitivity and specificity and is not recommended for diagnosis of listeriosis in individual patients