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Up Coag. -ve staph. Listeria Staphylococcus aureus Streptococci


  • Gram positive non sporing bacillus

  • Only L. monocytogenes and L. ivanovii are associated with significant infection in humans  

Listeria monocytogenes


  • Almost all cases of infection acquired through the ingestion of contaminated food

  • Pregnant women and immunocompromised patients are more prone to infection with 2/3 of adult cases occurring in the immunocompromised. However community acquired cases may occur spontaneously in patients who have no underlying predisposing conditions


Can invade and survive within macrophages of the liver and spleen as well as non-phagocytic cells (epithelial, hepatocellular, fibroblast cell lines). As such the organisms are temporarily sheltered from host defence mechanisms and they are able to grow and spread

Clinical features

Listerosis during pregnancy

  • Early cases associated with septic abortion

  • Most cases occur after 5 months gestation: premature delivery of septic or stillborn infant

  • Maternal flu like illness often precedes delivery by 2-14 days

    • Fever and chills

    • Fatigue, headache

    • Myalgia

  • Maternal listerosis can be transmitted to the fetus by an ascending or transplacental route

Listerosis in non-pregnant adults

  • Usually presents as meningitis or meningoencephalitis. Occasionally as an isolated cerebritis

  • Immunocompromised adults, particularly renal transplant recipients

  • Illness often subacute, similar to the pattern seen in cryptococcal or tuberculous meningitis

  • CSF: raised protein, moderate pleocytosis, (polymorphonuclear cells>lymphocytes)

  • High incidence of prolonged ataxia, hydrocephalus and cerebellar atrophy.

  • Brainstem encephalitis and brain abscesses also seen. Good prognosis

  • Focal infections include:

    • Lymphadenitis

    • Endocarditis

    • Arthritis

    • Osteomyelitis

    • Peritonitis

    • Acute cholecystitis

    • Acute hepatitis


  • Tends to be susceptible to ampicillin, penicillin, erythromycin and tetracycline.

  • Uniformly highly resistant to cephalosporins

  • In animal models combination of ampicillin with an aminoglycoside resulted in significantly better eradication of organisms in the spleen when compared with ampicillin alone

Listeriosis in pregnancy

  • If amnionitis is present: ampicillin 4-6 g/day 6hrly IV with an aminoglycoside.

  • If amnionitis is not present or has subsided oral amoxicillin 2-3 g/day is probably adequate.

  • 14 day course in both cases

  • Erythromycin if patient allergic to penicillins. But avoid estolate because increased liver toxicity in pregnancy

  • Avoid trimethoprim-sulfamethoxazole because of potential toxic effects if premature labour occurs and child is jaundiced

Listerosis in non-pregnant adults

  • Meningitis: Ampicillin 200-400 mg/kg/day in 4-6 daily doses for 3 weeks in combination with an aminoglycoside

  • If response is delayed (>2 days) further investigations including CT indicated to assess for presence of cerebritis, abscess, brainstem encephalitis, or intracranial haemorrhage

  • Treatment should be prolonged to 6 weeks if cerebral pathology identified. If organism persists in CSF addition of rifampicin or use of trimethoprim-sulfamethoxazole may be considered if organism is sensitive in vitro.

  • Vancomycin has been used successfully in patients who are allergic to penicillin


©Charles Gomersall, April, 2014 unless otherwise stated. The author, editor and The Chinese University of Hong Kong take no responsibility for any adverse event resulting from the use of this webpage.
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