Listeria has been isolated from raw meat, dairy products, vegetables, and seafood. Soft cheeses and unpasteurized milk have been the most frequently incriminated dairy products. Ingestion of Listeria by pregnant women can result in a flulike illness. Many pregnant women can carry Listeria asymptomatically in their GI tract or vagina. Maternal infection with Listeria can result in chorioamnionitis, premature labor, spontaneous abortion, or stillbirth.
Fetal infection can occur via transplacental transmission.
Vertical transmission also can occur from mother to infant via passage through an infected birth canal or ascending infection through ruptured amniotic membranes. Early onset neonatal listeriosis usually is associated with sepsis or meningitis. Late onset neonatal listeriosis frequently presents with purulent meningitis. Listeriosis often involves many organs with microabscesses or granulomas. A disseminated rash with small pale nodules that are granulomas histologically characterize granulomatosis infantisepticum.