Listeriosis is a foodborne illness caused by the bacterium Listeria monocytogenes. During pregnancy, this infection is particularly concerning, as pregnant individuals are 10 to 20 times more susceptible due to immune system changes. Early detection of a Listeria infection is important because it can lead to severe health consequences for both the pregnant individual and the developing baby.
When Testing is Recommended
Testing for Listeria is generally considered when a pregnant individual exhibits specific symptoms, especially after consuming foods associated with higher risk. Symptoms of listeriosis often resemble a mild flu, including fever, chills, muscle aches, headache, and fatigue. Gastrointestinal issues like diarrhea or nausea may also be present. These symptoms can develop anywhere from a few days to up to two months after exposure.
Healthcare providers typically recommend testing if a pregnant person has a fever exceeding 100.6°F (38.1°C) accompanied by flu-like symptoms, particularly if there’s a possibility of having consumed high-risk foods. Such foods include unpasteurized dairy products, soft cheeses, deli meats, hot dogs (unless reheated to steaming hot), and refrigerated smoked seafood. If symptoms are mild or a fever is absent, testing may not be immediately necessary, but monitoring is advised.
Types of Tests Available
Diagnosis of Listeria infection primarily relies on culturing the bacteria from a sterile body site. The most common method for pregnant individuals is a blood culture. This involves taking a blood sample and sending it to a laboratory to confirm the bacteria’s presence in the bloodstream.
If there is concern about the infection spreading, other tests may be performed. If meningitis is suspected, a cerebrospinal fluid (CSF) culture may be conducted via a lumbar puncture to collect fluid from around the brain and spinal cord. An amniotic fluid culture might be considered if the infection is suspected to have reached the fetus, involving fluid collection during an amniocentesis. Placental cultures may also be obtained after birth to help diagnose maternal-neonatal listeriosis.
Understanding Your Test Results
A negative test result for Listeria is generally reassuring, indicating that the bacteria was not detected. However, if symptoms persist or worsen, or if there was a known exposure to contaminated food, it is important to continue discussions with a healthcare provider.
A positive test result confirms a Listeria infection and indicates the need for immediate medical intervention. Treatment typically involves antibiotics, such as ampicillin or penicillin, administered to protect both the pregnant individual and the baby. Prompt antibiotic treatment is important to help prevent severe complications for the pregnancy, including miscarriage, stillbirth, premature birth, and serious infection in the newborn.