History and exam

Key diagnostic factors

common

presence of risk factors

Strong risk factors include exposure to contaminated food, pregnancy, age >45-50 years or neonatal, or immunocompromise.

headache

Retrospective studies suggest that headache occurs in approximately half of patients with central nervous system infection with L monocytogenes.[1][43]

uncommon

altered mental status

May be seen due to sepsis or CNS infection.[1][43]

Other diagnostic factors

common

fever

May be an indication of bacteraemia or CNS infection, particularly in susceptible groups.[1][43]

May be seen in febrile gastroenteritis, which is the main manifestation of infection in immunocompetent people.

diarrhoea and abdominal pain

Seen in febrile gastroenteritis.

Invasive listeriosis is rare in immunocompetent people. Stool cultures may be positive in 5% of the healthy asymptomatic population and in up to 87% in outbreaks of febrile gastroenteritis due to Listeria.[1]

When healthy adults are symptomatically infected, their clinical presentation mimics febrile gastroenteritis that occurs sporadically or as an epidemic.[5][31][32][37]

generalised malaise

Generalised and atypical or subtle symptoms are seen in older adults and neonates.

flu-like symptoms in pregnancy

Fever, arthralgias, myalgias, headache, fatigue, diarrhoea, vomiting, and abdominal ache are a common presentation of listeriosis in pregnancy.[2]

poor feeding (neonates)

May be the only indication of infection in this age group.

uncommon

meningismus

Nuchal rigidity suggesting meningismus may be seen. Incidence is lower than for meningitis due to other pathogens.[1][6]

cranial nerve deficits

Motor and sensory deficits may occur in complicated meningitis and rhombencephalitis.[6]

cerebellar signs

May be seen in brain stem encephalitis.

focal neurological signs

May be seen in brain abscess.

seizures

Usually occur later in course of CNS infection.

hypotension

May be seen in septic shock.

intra-partum fever

Indications of chorioamnionitis from Listeria (such as intra-partum fever) are a frequent finding in cases of neonatal infection.[2][4]

bleeding diathesis with haemorrhage

Seen in severe infections with disseminated intravascular coagulation. Mortality is high.

cardiac murmur

Listeria may affect both native and prosthetic valves. Endocarditis is more common among patients with immunosuppression.

Risk factors

strong

exposure to contaminated food

Food can be contaminated by Listeria, which is widespread in nature. Raw, undercooked, or processed meat and vegetables; soft cheeses; and leftover food may carry the bacteria.[7][36][31][37][38] Ingestion of bacteria is the main and most frequent route of transmission.[36]

The presence of more than 100 colony-forming units per g of Listeria species is considered unsatisfactory and immediate investigation is required.[39]

age >45-50 years

In older adults, Listeria has an affinity for the central nervous system, causing meningitis, meningoencephalitis, abscesses, brain stem encephalitis, and seizures.[1]

pregnancy

Pregnant women are more susceptible to Listeriainfection due to relatively impaired cellular immunity and inadequate stomach acidification. Infection has been associated with increased incidence of miscarriage.[4]

Septic abortion due to granulomatosis infantiseptica (trans-placental transmission leading to disseminated micro-abscesses) is a serious complication.[4]

neonates

Trans-placental transmission, transmission through an infected birth canal, and cross-contamination in neonatal clinics are the routes of neonatal bacteraemia and sepsis from Listeria.[2][40]

immunocompromised states

Cancer, haematological malignancies, chemotherapy, corticosteroids, transplantation, AIDS with a CD4 count <100/mm³, and splenectomy are strongly correlated to impaired cellular immunity and are epidemiological factors for Listeria infection.[1][18][19] Iron is necessary for the bacterium's metabolism and growth; hence, infection can be seen in iron overload states (which are also a form of immunocompromise).[5][29][34]

weak

impaired stomach acidification

Impaired stomach acidification potential (such as achlorhydria) has been implicated as a potential determinant of ingested inoculum leading to infection in food-borne illness.[1][3]

Use of this content is subject to our disclaimer