Overview
Listeria monocytogenes is a Gram-positive rod that is found in soil, sewage, and faeces and can cause infection in pregnant people, neonates, immunocompromised people (e.g. HIV) and the elderly.
Although rare in the general population, infection in susceptible people can lead to life-threatening sepsis, meningitis, and pregnancy complications including stillbirth.
It is mainly spread through food contamination, and outbreaks have been reported, with sources often being reported as being frozen vegetables and pork.
Listeriosis describes an infection with Listeria species.
Pathophysiology
Susceptible individuals are people with impaired cellular immunity as immunity depends on the presence of specific T-cell responses rather than antibodies, and reduced stomach acidification, which can disrupt normal gastrointestinal flora. Listeria monocytogenes is capable of escaping an immune response by moving from cell to cell and it most commonly affects the nervous system and placenta.
Risk Factors
- >45 years old
- Exposure to contaminated food
- Pregnancy
- Neonates
- Immunocompromise (e.g. HIV, chemotherapy)
- Exposure to contaminated food
Presentation
Maternal listeriosis tends to occur after 20 weeks’ gestation and may present causes:
- Non-specific features – fever, sore throat, headaches
- Pregnancy complications – reduced foetal movements, premature labour, stillbirth, abortion, neonatal infection
In neonates:
- Early neonatal disease (<5 days) can present with sepsis and can cause long-term complications such as neurological (e.g. hemiplegia) or lung disease. It has a high mortality rate.
- Late neonatal disease (>5 days) can present with meningitis, but mortality is lower.
Investigations
Overview
Some investigations include:
- Full blood count (FBC) – may show leukocytosis due to bacterial infection
- Blood cultures – if the patient is febrile and infection is suspected:
- Samples should ideally be taken before starting antibiotics, but this should not delay treatment
- Urine pregnancy test – all people of childbearing potential should be screened
- CT/MRI brain – if neurological involvement is suspected
- Used to exclude mass lesions to allow lumbar punctures
- Lumbar puncture and cerebrospinal fluid analysis – may identify infection:
- May show raised white cells, protein, and culturing may identify Listeria
Management
Overview
Meningitis caused by Listeria is treated using IV ampicillin (or amoxicillin) + gentamicin.
Complications
- Pregnancy complications – such as stillbirth and neonatal infection. This may occur due transmission of Listeria through the placenta
- Permanent neurological deficits – up to 1/3 of people have residual neurological deficits after recovery (e.g. hemiplegia)
