Introduction

• Listeria monocytogenes is a gram-positive rod found in soil, vegetation, and animals.

• Human infection by L. monocytogenes is most commonly seen in immunocompromised patients or in pregancy.

• Most infections are due to eating contaminated foods, but invasive clinical syndromes including meningitis, sepsis, chorioamnionitis, and still birth result.

• The increased risk of L. moncytogenes infection in pregnancy is thought to be due to changes in both systemic and local immune system.

  • Immune suppression at the maternal-fetal placental interface may favor intrauterine infection after transient maternal bacteremia.

Clinical presentations

• Pregnancy-associated listeriosis:

  • May occur at any stage of pregnancy, but usually detected during last trimester.

  • Manifestations include chorioamnionitis, premature labor and intrauterine fetal death.

  • Clinical outcome is favorable following delivery or treatment with antibiotics.

• Neonatal listeriosis:

  • Early onset disease is by second day

  • Early-onset disease includes:

    •  Likelihood of obstetrical complications (chorioamnionitis;premature delivery)

    •  Sepsis

    •  Respiratory distress

    •  Skin lesions

    •  Granulomatosis infantisepticum (abscesses involving liver, spleen, adrenal glands, lungs, etc)

  • Late-onset disease is more likely associated with normal delivery and later development of meningitis.

• Non-pregnancy associated listeriosis:

  • Immunocompromised patients, especially the elderly

  • Underlying conditions include: chronic glucocorticoid therapy, hematologic or solid malignancies, diabetes mellitus, renal disease, liver disease, AIDS.

  • Listeriosis is a relatively uncommon opportunistic infection in AIDS

•  Sepsis: symptoms similar to bacteremia caused by other agents.

•  CNS infection: meningitis

•  Endocarditis: patients with prosthetic or previously damaged valves are at higher risk.

Treatment

• i.v. ampicillin (Principen, Omnipen) or penicillin, often in combination with synergistic-acting aminoglycoside.

• In patients with penicillin allergy: the combination of trimethoprim-sulfamethoxazole (Bactrim) is bactericidal and may be effective.

• Chloramphenicol (Chloromycetin) and rifampin (Rimactane) may antagonize bactericidal effects of penicillins.

• Cephalosporins: not recommended.

Schuchat, A., and Broome, C.V. Infections Caused by Listeria Monocytogenes. In Harrison's Principles of Internal Medicine 14th edition, (Isselbacher, K.J., Braunwald, E., Wilson, J.D., Martin, J.B., Fauci, A.S. and Kasper, D.L., eds) McGraw-Hill, Inc (Health Professions Division), 1998, p. 899-901.