Skip to Main Content


Neonatal sepsis is a clinical syndrome of systemic illness accompanied by bacteremia occurring in the first month of life. It can be classified into 2 relatively distinct syndromes based on the age of presentation: early-onset and late-onset sepsis. These 2 entities will be discussed separately.



Early-onset sepsis (EOS) is defined by the Centers for Disease Control and Prevention (CDC) as blood and/or cerebrospinal fluid (CSF) culture–proven infection occurring in the newborn at <7 days of age. For the continuously hospitalized very low birthweight (VLBW; <1500 g) infant, EOS is defined as culture-proven infection occurring at <72 hours of age.


The overall incidence of EOS in the United States is estimated at 0.77 to 0.98 per 1000 live births. Incidence is strongly influenced by gestational age (GA) at birth. Among infants born at ≥37 weeks’ gestation, the incidence is around 0.53 per 1000 live births, whereas in the preterm population, the incidence is 3.7 per 1000 live births (7 times higher), and among VLBW infants, it is approximately 11 per 1000 live births (20 times higher).


  1. Infants usually present with a multisystem, sometimes fulminant, illness with prominent respiratory symptoms. Typically, the infant has acquired the organism during the antepartum or intrapartum period from the maternal genital tract. Several infectious agents, notably treponemes, viruses (eg, herpes simplex virus, enteroviruses, and parechoviruses), Listeria, and probably Candida, can be acquired transplacentally via hematogenous routes. Acquisition of other organisms is associated with the birth process. With rupture of membranes, vaginal flora or other bacterial pathogens may ascend to reach the amniotic fluid and the fetus. Chorioamnionitis develops, leading to fetal colonization and infection. Aspiration of infected amniotic fluid by the fetus or neonate may play a role in the resultant respiratory symptoms. Finally, the infant may be exposed to vaginal flora as it passes through the birth canal. The primary sites of colonization tend to be the skin, nasopharynx, oropharynx, conjunctiva, and umbilical cord. Trauma to these mucosal surfaces may lead to infection. The disease may present suddenly with a fulminant course that can progress rapidly to septic shock and death.

  2. Microbiology. The principal pathogens involved in EOS have tended to change with time. Before 1965, Staphylococcus aureus and Escherichia coli used to be the most commonly isolated organisms. In the late 1960s and early 1970s, group B Streptococcus (GBS) emerged as the most common microorganism. Currently, most centers continue to report GBS as the most common microorganism, even though the incidence has decreased considerably after the widespread adoption of universal antenatal screening for GBS colonization at 35 to 37 weeks’ gestation and intrapartum antibiotic prophylaxis (IAP) with penicillin or ampicillin for colonized women. The incidence of EOS secondary to GBS decreased from 1.7 per ...

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.