Listeria Testing and Response

Lettuce identified by the manufacturer as potentially contaminated with Listeria was served in local schools over the past few weeks.  A message to parents with children in these schools was sent out earlier this week.  This lettuce has been removed from the school stocks, but most of that lettuce had already been served before the warning was issued.

A few highlights to point out:

1) No cases of Listeriosis have yet to be reported secondary to this event.

2) Culture of stool for Listeria has a low yield and has not been evaluated as a screening or diagnostic test (Listeria can be found in the feces of healthy persons, and a negative stool culture for Listeria does not exclude the possibility of Listeria infection or carriage).  The UIHC clinical microbiology laboratory and the State Hygienic Laboratory do not perform stool cultures for ListeriaIf stool is sent for Listeria culture, it will not be performed. There is no reliable screening test for asymptomatic patients.

3) No testing or treatment is indicated for an exposed, asymptomatic person.  Such a person should be instructed to return if he or she develops symptoms of listeriosis within two months of eating the recalled product. Symptoms may include fever and myalgias, often preceded by diarrhea or other gastrointestinal symptoms. In older adults and immunocompromised persons, symptoms of listeriosis can include headache, stiff neck, confusion, loss of balance, and seizures.  Cultures of blood and/or CSF should be performed in symptomatic patients with suspected listeriosis.

For additional information about management of persons at risk for, or with symptoms of, listeriosis, please refer to the CDC document.  The Infectious Diseases consult service is also available to assist in the diagnosis and treatment of patients with suspected listeriosis.

Questions should be directed to Daniel J. Diekema, MD, Director, Division of Infectious Diseases (356-2591) or J. Stacey Klutts, MD, PhD, Medical Director, Clinical Microbiology Laboratory (356-2990).