This summary discusses listeriosis in infants. Listeriosis in adults and children is addressed separately.

Emergent Care / Stabilization:
Infants with suspected neonatal listeriosis should be transferred to a neonatal intensive care unit (NICU) for management. Immediate stabilization addressing the ABCs (airway, breathing, circulation) should be rapidly initiated. Antimicrobial therapy should be initiated as soon as possible without waiting for culture or microbiologic data.

Diagnosis Overview:
Neonatal listeriosis is a (typically) transplacentally contracted infection caused by the presence of the facultative intracellular gram-positive motile rods, known as Listeria monocytogenes, a foodborne pathogen. While rare, neonatal infection is associated with high rates of neurologic morbidity and mortality. Listeria monocytogenes is ubiquitous in nature and is found in the fecal flora of many mammals; listeriosis is a common foodborne illness. Possibly contaminated food sources include unpasteurized dairy products, soft cheeses, raw vegetables, prepared deli meats and salads, refrigerated meat spreads, and smoked seafood.

In the United States, there have been food product recalls due to listerial contamination identified through routine screening and surveillance. Despite such strict surveillance, sporadic outbreaks of listerial food poisoning still occur.

As the typical mode of transmission of Listeria to a neonate is from mother to child, it is essential to be aware of symptoms and signs present in the expecting mother as well as the neonate. Listeriosis is 18 times more common in pregnant individuals than in the nonpregnant population. Listeria infections in pregnant patients account for up to 25% of all Listeria infections.

There are certain pregnant populations especially susceptible to listeriosis due to cultural diet habits. Women of Hispanic ethnicity are more likely to report having contracted listeriosis compared with other groups (52.8% versus 25.6%, respectively; odds ratio of 3.3 [95% CI 2.2-4.8]). This is thought to be associated with the presence and prevalence of Mexican-style cheese (which contains unpasteurized milk) in the diet.

In pregnant individuals, a Listeria infection is most likely to be contracted during the third trimester, with increased chance of fetal death the later into pregnancy the disease is contracted. It is possible for the organism to spread across the placenta, for the fetus to aspirate infected amniotic fluid, or for ascending infection from the vaginal canal. Although the symptoms of listeriosis in pregnant patients are rather nonspecific (or sometimes even absent), they include backache, sore throat, flu-like symptoms, and/or gastroenteritis.

Neonatal listeriosis has 2 different clinical presentations: early- and late-onset disease.

Early-onset neonatal listeriosis is usually acquired by transplacental transmission or aspiration of infected amniotic fluid. It presents within 5 days of birth (mean age of 36 hours). Granulomatosis infantisepticum, presenting as a diffuse, erythematous rash with small granulomatous nodules, is a pathognomonic feature of early-onset listeriosis. There is a 20%-40% mortality rate in early-onset neonatal listeriosis.

In contrast, late-onset neonatal listeriosis is thought to occur during vaginal delivery or secondary to nosocomial contamination. It typically begins after 5 days postpartum (mean age of 2 weeks). Affected neonates are typically born at term, and they present with septicemia and meningitis. However, the mortality rate is lower (0%-20%).