Listeria monocytogenes infection in neonates

Please note that all guidance is currently under review and some may be out of date. We recommend that you also refer to more contemporaneous evidence in the interim.

Listeria monocytogenes infection is transmitted to humans via food, especially unpasteurised dairy products contaminated by infected farm animals, soft cheeses, prepared deli meats and refrigerated meat spreads.

Listeria infection is life threatening for neonates, and rapid diagnosis and treatment is important.

Prevalence and mortality rates

• uncommon in Australia, with 0.3 cases per 100,000 population.
• more common in pregnancy than the non-pregnant population.
• transmission highest in the 3rd trimester; maternal listeriosis in 2nd and 3rd trimester results in 40 to 50 per cent fetal mortality.
• in Australia in 2003 there were 4.6 cases per 100,000 births
• the mortality of neonatal listeriosis is about 5-15 per cent.

Clinical manifestations of listeria

Transplacental infection

Features include:

• Causes a non-specific influenza or gastroenteritic illness in pregnant women during which the organism may infect the fetus by spreading across the placenta or through amniotic fluid.
• First and second trimester infection may cause miscarriage or fetal death.
• Late pregnancy infection may precipitate preterm labour with fetal distress and meconium staining of the liquor.
• Since meconium staining of the liquor is rare below 34 weeks its presence should raise suspicion of listeriosis.
• Characteristically, small (2-3 mm) pinkish-grey cutaneous granulomas are present and, at autopsy, similar small granulomatous lesions are widespread in the liver, lungs, central nervous system (CNS) and many other tissues and organs.

Early-onset infection

Features include:

• 60 per cent of infants infected intrapartum are preterm and become ill within 24 hours of birth.
• most have disseminated infection with:
  • pneumonia
  • meningitis
  • thrombocytopenia
  • anaemia
  • conjunctivitis.
• placenta, blood, urine, CSF and stool should be cultured
• most cases are sporadic, but epidemics are described
• mortality high (20 to 60 per cent).

Late-onset infection

Features include:

• usually presents as meningitis, probably due to nosocomial infection
• median age of onset is about 14 days
• mortality 10 to 20 per cent.

Investigations

Febrile pregnant women:

• Culture of blood, cervical and amniotic fluid and placenta.
   

Sick neonates:

• Culture of blood, urine, CSF, gastric aspirate, meconium and infected tissues
• CXR
• FBE and/differential
   

Gram stain can be variable and the organism slow growing.

Treatment

• Penicillin or ampicillin and gentamicin.
• Recommended duration of treatment 2-3 weeks
• Listeria is resistant to all third-generation cephalosporins.

Note:

• Educate pregnant women to avoid food associated with listeria.
• Investigate pregnant women with flu like symptoms and consider early treatment.
• Investigate babies at risk of infection.
• Listeriosis (group B) is a notifiable disease and must be notified in writing within five days of diagnosis or online. See Notifying infectious diseases in Victoria.