3/10/2024
Evaluation and Management of Listeria Monocytogenes Exposure and Diagnosis in Pregnancy
Registered users can also download a PDF or listen to a podcast of this Pearl.
Log in now, or create a free account to access bonus Pearls features.
Listeriosis is primarily caused by eating food contaminated with the bacterium Listeria monocytogenes. Most affected persons present with a self-limiting flulike illness or gastroenteritis. In the most severe cases, individuals can develop fever, vomiting, and endocarditis or brain abscesses if immunocompromised.
The foods responsible for L monocytogenes outbreaks range from the most common culprit—unpasteurized cheese—to deli meat, unwashed produce, melon, and ice cream. While most store-bought cheeses in the United States are pasteurized, queso fresco is in many melted cheese dishes and remains an exposure risk. Mitigation of infection risk can be accomplished by avoiding high-risk foods, thoroughly washing fruits and vegetables, and practicing hand hygiene. The overall incidence of listeriosis is low; the Centers for Disease Control estimates about 1600 cases in the United States annually. However, infection is more common and more serious in vulnerable populations such as newborns and elderly, immunocompromised, or pregnant persons. Pregnant individuals are 10 to 20 times more likely to develop listeriosis, with an incidence of about 12 per 100,000.
Listeriosis is usually mild in pregnant persons. However, vertical transmission carries a risk of abortion or stillbirth as high as 20%, with a greater than 60% risk of neonatal listeriosis in the surviving infant. These risks are trimester dependent; although infection is more common in the third trimester, risk of miscarriage or stillbirth is significantly higher earlier in gestation. One cohort study noted a fetal loss following L monocytogenes infection of 100% in the first trimester, 70% in the second, and less than 5% in the third.
Diagnosis of listeriosis can be challenging, and recommendations for treatment are primarily based on symptoms and presumptive exposure. L monocytogenes is most easily isolated in blood cultures, and confirmation of infection is difficult in the absence of bacteremia. Stool culture for common enteric pathogens has a low sensitivity for L monocytogenes isolation and should not be used for diagnosis, although it can help rule out other causes of gastroenteritis. In a patient presenting with an exposure, testing and treatment are not recommended unless the patient is symptomatic. An “exposure” should be considered when a patient ingests either food implicated in a listeriosis outbreak or food with high risk of contamination. If the patient presents with symptoms but is afebrile, the benefit of treatment is uncertain. However, it is reasonable to proceed with blood cultures, stool studies, and oral antibiotic therapy (amoxicillin), with close monitoring for worsening symptoms. If a fever develops, the patient should be hospitalized and started on intravenous antibiotic therapy (ampicillin).
L monocytogenes infection is rare, but reasonable caution should be exercised in avoiding high-risk foods and ensuring good hygiene in food preparation and storage. Treatment or prophylaxis in an asymptomatic patient with an exposure is not recommended, but prompt treatment of a patient with a febrile gastroenteritis and high likelihood of exposure could improve both maternal and neonatal outcomes.
Further Reading:
Committee Opinion No. 614: Management of pregnant women with presumptive exposure to Listeria monocytogenes. Obstet Gynecol. 2014 Dec;124(6):1241-1244. doi: 10.1097/01.AOG.0000457501.73326.6c. PMID: 25411758.
Centers for Disease Control and Prevention (CDC). Prevent Listeria https://www.cdc.gov/listeria/prevention.html
Craig AM, Dotters-Katz S, Kuller JA, Thompson JL. Listeriosis in Pregnancy: A Review. Obstet Gynecol Surv. 2019 Jun;74(6):362-368. doi: 10.1097/OGX.0000000000000683. PMID: 31216045.
Initial Publication: March 10, 2024
********** Notice Regarding Use ************
The Society for Academic Specialists in General Obstetrics and Gynecology, Inc. (“SASGOG”) is committed to accuracy and will review and validate all Pearls on an ongoing basis to reflect current practice.
This document is designed to aid practitioners in providing appropriate obstetric and gynecologic care. Recommendations are derived from major society guidelines and high-quality evidence when available, supplemented by the opinion of the author and editorial board when necessary. It should not be construed as dictating an exclusive course of treatment or procedure to be followed.
Variations in practice may be warranted when, in the reasonable judgment of the treating clinician, such course of action is indicated by the condition of the patient, limitations of available resources, or advances in knowledge or technology. SASGOG reviews the articles regularly; however, its publications may not reflect the most recent evidence. While we make every effort to present accurate and reliable information, this publication is provided “as is” without any warranty of accuracy, reliability, or otherwise, either express or implied. SASGOG does not guarantee, warrant, or endorse the products or services of any firm, organization, or person. Neither SASGOG nor its respective officers, directors, members, employees, or agents will be liable for any loss, damage, or claim with respect to any liabilities, including direct, special, indirect, or consequential damages, incurred in connection with this publication or reliance on the information presented.
Copyright 2024 The Society for Academic Specialists in General Obstetrics and Gynecology, Inc. All rights reserved. No re-print, duplication or posting allowed without prior written consent.
Back to Search Results