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# Listeriosis

Listeriosis is a food-borne bacterial infection that is dangerous in pregnancy, newborns, older adults and people with weak immunity.

Updated 2026-11-01

## Structures involved

Tap one to see what it is and open it in 3D.

- [Dura mater](https://durgical.com/en/anatomy/cranial-dura/)
- [Medulla oblongata](https://durgical.com/en/anatomy/medulla-oblongata/)
- [Pons](https://durgical.com/en/anatomy/pons/)

## Microorganisms that cause it

- [Listeria monocytogenes](https://durgical.com/en/microbiology/listeria-monocytogenes/)

## Why it happens

- [Innate and adaptive immunity: overview](https://durgical.com/en/physiology/innate-and-adaptive-immunity-overview/)
- [Cytoskeleton: microfilaments, intermediate filaments, microtubules](https://durgical.com/en/histology/cytoskeleton-microfilaments-intermediate-filaments-microtubules/)
- [Placenta](https://durgical.com/en/histology/placenta/)

## What it is

Infection by Listeria monocytogenes, a gram-positive intracellular bacillus acquired from contaminated food, that causes febrile gastroenteritis in healthy people and invasive disease (sepsis, meningitis, rhombencephalitis, pregnancy and neonatal infection) in high-risk groups.

## Who gets it

Rare but with one of the highest fatality rates among food-borne infections (about 20–30% for invasive disease). Pregnant women are many times more susceptible than other healthy adults. Outbreaks have been linked to soft and fresh cheeses, deli meats, smoked fish and fresh produce; in Latin America fresh unpasteurised cheese is a recognised vehicle.

## Causes

- Listeria monocytogenes from soil, water and animal intestines
- Contaminated ready-to-eat foods: soft and fresh cheeses, deli and cold meats, smoked fish, prepared salads, unpasteurised milk
- Growth at refrigerator temperatures, so food can become heavily contaminated during storage
- Transplacental spread or contact during delivery for neonatal infection

## Risk factors

- Pregnancy
- Newborns
- Age over about 60 years
- Immunosuppression: corticosteroids, transplant, cancer, chemotherapy, advanced HIV
- Diabetes, cirrhosis, chronic [kidney](https://durgical.com/en/anatomy/kidney/) disease and alcohol use disorder

## Pathophysiology

Listeria crosses the intestinal wall, enters cells and moves directly from cell to cell by polymerising host actin, which shields it from antibodies. Defence depends on cell-mediated immunity, so pregnancy and immunosuppression allow bacteraemia. The organism has a tropism for the central [nervous system](https://durgical.com/en/anatomy/system/nervous-system/) (meninges and brainstem) and for the placenta, where it causes chorioamnionitis and fetal infection.

## Classification

- Febrile gastroenteritis (non-invasive) in healthy people after a large dose
- Invasive disease in adults: bacteraemia, meningitis, meningoencephalitis, rhombencephalitis, focal infections
- Pregnancy-associated listeriosis: maternal febrile illness with fetal infection
- Neonatal listeriosis: early onset (first week, transplacental; granulomatosis infantiseptica) and late onset (meningitis after the first week)

## Symptoms and signs

- Fever, myalgia, diarrhoea and nausea in the gastrointestinal form
- Flu-like illness or no symptoms in pregnant women
- Headache, stiff neck and altered consciousness in meningitis
- Cranial nerve palsies, ataxia and asymmetric weakness in brainstem encephalitis
- Newborn with respiratory distress, poor feeding, rash or seizures

## Red flags

- Fever in a pregnant woman after eating high-risk foods
- Meningitis signs in a person over 50, a newborn or an immunosuppressed patient
- Cranial nerve deficits with fever (rhombencephalitis)
- Reduced fetal movements or preterm labour with maternal fever

## Diagnosis

**Clinical**
Suspected in fever or meningitis in a high-risk patient, and in a pregnant woman with fever after high-risk foods. Empirical treatment is not delayed for results.

**Tests**
Cultures of blood and cerebrospinal fluid (and placenta, amniotic fluid or neonatal samples); routine stool culture does not detect it. CSF often shows a neutrophilic or mixed pleocytosis with a normal or low glucose; the Gram stain is often negative. Gram-positive rods in CSF suggest Listeria.

**Imaging**
Brain MRI for suspected rhombencephalitis or abscess; obstetric ultrasound for fetal wellbeing.

## Differential diagnosis

- Bacterial meningitis by pneumococcus or meningococcus
- Viral encephalitis
- Chorioamnionitis by other organisms
- Neonatal group B streptococcal sepsis
- Viral gastroenteritis

## Goal of treatment

Give antibiotics active against Listeria early in invasive disease and pregnancy to prevent death, neurological damage and fetal infection.

## Treatment

**Medical**
Intravenous ampicillin (or penicillin), often with gentamicin in severe disease; Listeria is intrinsically resistant to cephalosporins, so ampicillin is added to empirical meningitis therapy in newborns, people over 50 and the immunosuppressed.

**Medical**
Trimethoprim-sulfamethoxazole as an alternative in penicillin allergy; prolonged courses for meningitis, rhombencephalitis and abscess.

**Acute**
Sepsis and meningitis care: airway, fluids, seizure control and intensive care when needed; neonatal resuscitation for an infected newborn.

**Follow-up**
Fetal monitoring in pregnancy; neurological checks for cranial nerve and consciousness changes; report clusters to public health for food tracing.

## Complications

- Miscarriage, stillbirth and preterm birth
- Neonatal sepsis and meningitis
- Rhombencephalitis and brain abscess
- Hydrocephalus and lasting neurological deficits
- Septic shock and death

## Prognosis

Invasive listeriosis has a high case-fatality rate (about one in four to one in five), higher in older and immunosuppressed adults and in early-onset neonatal disease. Prompt treatment of the mother can prevent fetal infection.

## Prevention

- Pregnant women and high-risk people avoid fresh unpasteurised cheese, raw milk, cold deli meats and refrigerated smoked fish unless heated until steaming
- Reheat leftovers and ready-to-eat foods thoroughly; keep the refrigerator cold and clean
- Wash raw produce; separate raw and cooked foods
- Food-industry hygiene and outbreak surveillance

## Test yourself

Think of the answer, then tap the question to see it.

## Which antibiotic is added to empirical meningitis treatment in neonates and adults over 50 to cover Listeria, and why?

Ampicillin, because Listeria is intrinsically resistant to cephalosporins.

## Which foods are classically linked to listeriosis?

Soft and fresh unpasteurised cheeses, deli meats, smoked fish, unpasteurised milk and prepared ready-to-eat foods.

## Why can Listeria contaminate food that has been refrigerated?

It can grow at refrigerator temperatures.

## What brainstem syndrome is characteristic of Listeria?

Rhombencephalitis: fever with cranial nerve palsies, ataxia and altered consciousness.

## What are the pregnancy outcomes of listeriosis?

Miscarriage, stillbirth, preterm birth and neonatal sepsis or meningitis, often after a mild maternal illness.

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## Related conditions

- [Bacterial meningitis](https://durgical.com/en/conditions/bacterial-meningitis/)
- [Neonatal sepsis](https://durgical.com/en/conditions/neonatal-sepsis/)
- [Chorioamnionitis (intra-amniotic infection)](https://durgical.com/en/conditions/chorioamnionitis/)
- [Miscarriage (early pregnancy loss)](https://durgical.com/en/conditions/miscarriage/)
- [Stillbirth (intrauterine fetal death)](https://durgical.com/en/conditions/stillbirth/)
- [Preterm labour and birth](https://durgical.com/en/conditions/preterm-labour-and-birth/)
- [Sepsis and septic shock](https://durgical.com/en/conditions/sepsis-and-septic-shock/)
- [Acute (viral) gastroenteritis](https://durgical.com/en/conditions/acute-gastroenteritis/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Listeriosis](https://www.who.int/news-room/fact-sheets/detail/listeriosis) (World Health Organization, 2018); [Clinical Overview of Listeriosis | Listeria Infection | CDC](https://www.cdc.gov/listeria/hcp/clinical-overview/index.html) (Centers for Disease Control and Prevention, 2024).

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/listeriosis/