Listeria monocytogenes infections in neonates

Abstract

Listeria monocytogenes continues to be a major bacterial pathogen for newborn infants in North America. Neonatal listeriosis accounts for approximately 30 percent of the total listeriosis cases reported in the United States. Foodborne outbreaks of listeriosis have been attributed to dairy products and ready-to-eat prepared foods. During outbreaks, a disproportionately high number of cases occur as perinatal infection. In newborns, the high susceptibility to Listeria probably is attributable to delayed activation of macrophages. Production of tumor necrosis factor-α (TNF-α) and interleukin-12 (IL-12), which are essential mediators of host defense against Listeria , are produced in lower concentrations by infected newborn mononuclear cells. The clinical manifestations of listeriosis are well known. Perinatal infection often is associated with a preceding flulike disease in the pregnant woman. Maternal bacteremia may be present at this stage. Premature labor is common; approximately 70 percent of infected mothers deliver before 35 weeks' gestation. Among infants, two clinical syndromes are identified, early-onset and late-onset listeriosis. Early-onset infection is associated with overwhelming sepsis and a high mortality rate. Late-onset infection, occurring between 7 and 90 days of life, is less severe; however, a high proportion of cases have meningitis. Ampicillin in combination with an aminoglycoside is the preferred treatment for neonatal listeriosis. Removal of Listeria -contaminated food through strict adherence to regulatory standards has led to a decreased incidence of listeriosis in the United States since the early 1990s. Although the incidence of epidemic disease is decreasing in the United States, sporadic cases still do occur. All cases must be identified and treated early to achieve optimal outcome. A high index of suspicion and early intervention are essential.