Listeria

Reviewed and revised 4 July 2014

OVERVIEW

• Listeria monocytogenes is non-endospore forming, regular, non-branching gram positive bacilli that grows in aerobic and anaerobic conditions
• Listeriosis may resemble influenza or gastroenteritis but can be fatal and often occurs in outbreaks affecting the immunocompromised especially
• accounts for 20-65% of all deaths in the USA from foodborne illness

TRANSMISSION

• most common routes of transmission:
  – via food source
  – vertical transmission from mother to child
• found widely in the environment in soil, decaying vegetation and water
• outbreaks often related to contamination of cheese, cabbage, milk, deli meats and centralised production of ready-to-eat foods
• can be found in faecal flora of mammals including humans and spread by contact
• can grow at refrigerator temperatures (4°C to 10°C) and is resistant to freezing; killed by pasteurisation

RISK FACTORS

For severe forms of listeriosis

• >60 years-old
• pregnancy
• newborms
• immunocompromised
  • organ transplantation
  • immunosuppressant drugs e.g. corticosteroids, TNFR antagonists
  • cancer
  • diabetes mellitus
  • chronic renal failure
  • alcoholism
  • debilitation

CLINICAL FEATURES

• onset 2-70 days post-exposure to contaminated food
• Initial symptoms of infection include nonspecific flu-like symptoms, nausea, vomiting, cramps, diarrhea and fever
• self-limiting illness in most healthy adults
• may progress to severe illness: septic shock, ARDS, and/or meningoencephalitis
• joint infections and endocarditis are rare
• pregnant women may have mild-moderate severity infection, but have an increased risk of miscarriage and preterm labour
• newborns may present with sepsis in the first 24 hours (early onset Listeriosis) or may present with delayed irritability and poor feeding (late onset)

INVESTIGATIONS

• gram stain: gram positive bacilli (non-branching)
• blood cultures
• stool cultures if diarrhoea

MANAGEMENT

Resuscitation

• attend to ABCs

Antibiotics

• First line: penicillin G or amoxycillin
• Alternatives: cotrimoxazole, meropenem, Linezolid-Rifampicin

Supportive care and monitoring

Consults

• infectious diseases
• obstetrics / neonatology

Prevention

• see here

Notifiable disease

PROGNOSIS

• 10 to 50% mortality (highest in newborns)

References and Links

Journal articles

• Bortolussi R. Listeriosis: a primer. CMAJ. 2008 Oct 7;179(8):795-7. PMC2553879