Neonatal Listeriosis

Infections in pregnant patients may be asymptomatic or characterized by a primary bacteremia manifesting first as a nonspecific flu-like illness.

In the fetus and neonate, clinical presentation depends on the timing and route of infection. Spontaneous abortion or stillbirth, preterm delivery with amnionitis (with a characteristic brown, murky amniotic fluid), or neonatal sepsis and pneumonia are common. Infection may be apparent within hours or days of birth (early onset) or may be delayed up to several weeks (delayed onset).

Neonates with early-onset disease are frequently low birth weight, have associated obstetric complications, and show evidence of sepsis soon after birth with circulatory or respiratory insufficiency or both.

Neonates with the delayed-onset form are usually full-term, previously healthy neonates presenting with meningitis or sepsis.

• Culture or polymerase chain reaction (PCR) testing of blood, cervix, and amniotic fluid (if available) of febrile pregnant patient

• Culture or PCR of blood, cerebrospinal fluid (CSF), gastric aspirate, meconium, umbilical cord, placenta, and infected tissues of sick neonate

Blood and cervix specimens should be obtained from any pregnant patient with an unexplained febrile disease and cultured or PCR tested for L. monocytogenes. A sick neonate whose mother has listeriosis should be evaluated for sepsis, including cultures or PCR of umbilical cord, placenta, peripheral blood, CSF, gastric aspirate, meconium, any potentially infected tissue, the mother’s lochia and exudates from cervix and vagina, grossly diseased parts of the placenta, and amniotic fluid (if available).

CSF examination may show a predominance of mononuclear cells, but usually polymorphonuclear cells predominate. Gram-stained smears are frequently negative but may show pleomorphic, gram-variable coccobacillary forms, which should not be disregarded as diphtheroid contaminants.

Laboratory confirmation of the organism involves biochemical testing and observation of motility using a slide test or showing motility in semisolid media. To do the slide test, colonies of the organism that have grown on solid media are mixed with saline and examined under a microscope. L. monocytogenes exhibits a distinctive end-over-end “tumbling” motility due to the presence of flagella at both ends. Serologic tests are not useful.

• Ampicillin plus an aminoglycoside

Treatment of the newborn is with ampicillin plus an aminoglycoside (eg, gentamicin). A 14-day course is usually satisfactory (21 days for meningitis), but the optimal duration is unknown. Other possible medications include Treatment of the newborn is with ampicillin plus an aminoglycoside (eg, gentamicin). A 14-day course is usually satisfactory (21 days for meningitis), but the optimal duration is unknown. Other possible medications includeampicillin in combination with other intracellular medications such as fluoroquinolones, linezolid, or rifampin, but these have not been studied in pediatric patients, and susceptibility should be confirmed. in combination with other intracellular medications such as fluoroquinolones, linezolid, or rifampin, but these have not been studied in pediatric patients, and susceptibility should be confirmed.

Neonates with sepsis require other supportive measures.

Source control may be necessary for certain infections (eg, drainage of an abscess).

Mortality, ranging from 7 to 29%, is higher in neonates with early-onset disease (1, 2).

Pregnant patients should avoid food products that have a higher risk of contamination by L. monocytogenes (eg, unpasteurized dairy products, soft cheeses, raw vegetables, prepared deli meats and salads, refrigerated meat spreads or smoked seafood, uncooked fruit or vegetables, ice cream). Proper food handling, in particular separating uncooked meats from other items during preparation and washing hands, utensils, and cutting boards after handling uncooked foods, is critical.

If infection during pregnancy is recognized, treatment may then be given before delivery or intrapartum to prevent maternal-fetal transmission, but the usefulness of such treatment is unproved.