Listeriosis in Pregnancy

Background

• Listeriosis is a foodborne illness caused by ingestion of foods such as raw meats and unpasteurized dairy products which have been contaminated with Listeria monocytogenes.
• Incidence of listeriosis is rare, with a reported rate of 3 cases per 100,000 pregnant women in the United States.
• The incidence is about 10 times higher in pregnant women, with greatest susceptibility during the third trimester of pregnancy when T-cell immunity is most impaired.
• Typically presents as a mild nonspecific flu-like or gastrointestinal illness in the pregnant woman but effects on the pregnancy and fetus can be severe and include:
  • preterm labor in about 40%-65%
  • fetal loss or neonatal mortality in 20%-30%
  • sepsis, meningitis, or pneumonia in the neonate
• L. monocytogenes grows at 4 degrees C (39.2 degrees F), the refrigerator temperature typically used to control pathogen growth.

Evaluation

• No evidence-based guidelines exist to help determine when and what type of testing is appropriate for pregnant women potentially exposed to Listeria.
• Diagnosis of listeriosis is made by isolation of the organism from a normally sterile site, such as blood or cerebrospinal fluid.
• American College of Obstetricians and Gynecologists (ACOG) statement on management of pregnant women reporting consumption of a product recalled or implicated in a Listeria outbreak is based on expert opinion and suggests:
  • for asymptomatic pregnant women:
    • no testing, treatment, or fetal surveillance
    • monitor for symptoms suggestive of listeriosis over 2-month period
  • for afebrile pregnant women with mild nonspecific gastrointestinal or flu-like symptoms, either:
    • monitor expectantly for additional symptoms suggestive of Listeria such as fever
    • consider blood cultures
  • for febrile pregnant women, with or without additional symptoms suggestive of listeriosis:
    • simultaneously test for infection (obtain blood cultures) and treat empirically
    • obtain placental cultures, if fetus delivered
  • assessment of fetal well-being on a case-by-case basis for any symptomatic pregnant woman

Management

• No evidence-based guidelines or comparative trials establish a recommended strategy for treatment of pregnant women with listeriosis.
• High-dose ampicillin (≥ 6 g/day IV) is recommended as empiric therapy or for those with positive blood cultures, with some experts adding gentamicin.
• Treatment is typically given for ≥ 14 days; continuous treatment until time of delivery has been reported.
• Consider infectious disease and maternal-fetal medicine consultation to assist in management.
• In addition to food safety recommendations for the general public, pregnant women are advised to avoid foods associated with Listeria outbreaks such as:
  • hot dogs, cold cuts, and deli meats (unless cooked until steaming hot)
  • refrigerated pates, meat spreads, smoked or raw seafood
  • soft cheeses (such as feta or brie) Mexican cheeses (such as queso fresco) and blue-veined cheeses, unless pasteurized.