Epidemiology of Neonatal Early-onset Sepsis

Neonatal early-onset sepsis (EOS) continues to be a significant source of morbidity and mortality among newborns, especially among very-low birthweight infants. Epidemiologic risk factors for EOS have been defined, and considerable resources are devoted to the identification and evaluation of infants at risk for EOS. The widespread implementation of intrapartum antibiotic prophylaxis for the prevention of earlyonset neonatal group B Streptococcus (GBS) disease has reduced the overall incidence of neonatal EOS and influenced the microbiology of persistent early-onset infection. Most early-onset neonatal GBS disease now occurs in preterm infants or in term infants born to mothers who have negative GBS screening cultures. Ongoing clinical challenges include reassessment of clinical risk factors for EOS in the era of GBS prophylaxis; more accurate identification of GBS-colonized women; and continued surveillance of the impact of GBS prophylaxis practices on the microbiology of EOS, particularly among very low-birthweight infants. Introduction Bacterial sepsis and meningitis continue to be major causes of morbidity and mortality in newborns, particularly in very-low birthweight (VLBW) infants (birthweight 1,500 g). Neonatal early-onset sepsis (EOS) is defined by the Centers for Disease Control and Prevention (CDC) as blood or cerebrospinal fluid cultureproven infection occurring in the newborn who is younger than 7 days of age. (1) For the continuously hospitalized VLBW infant, EOS is defined as culture-proven infection occurring at fewer than 72 hours of age. (2) The alternative definition in VLBW infants is justified by two findings: 1) the risks for infection in VLBW infants after 72 hours of age primarily derive from the specifics of ongoing neonatal intensive care rather than from perinatal risk factors, and 2) the organisms causing infection after 72 hours of age among VLBW infants reflect the nosocomial flora of the neonatal intensive care unit (NICU) more than perinatally acquired maternal flora. (2) The overall incidence of EOS in the United States in the past 10 years is 1 to 2 cases per 1,000 live births; the incidence is 10-fold higher in VLBW infants. (3)(4) Since *Assistant Professor of Pediatrics, Harvard Medical School; Attending Physician, Channing Laboratory and Department of Newborn Medicine, Brigham and Women’s Hospital and Division of Newborn Medicine, Children’s Hospital, Boston. Abbreviations BWH: Brigham and Women’s Hospital CDC: Centers for Disease Control and Prevention EOS: early-onset sepsis GBS: group B Streptococcus IAP: intrapartum antibiotic prophylaxis MRSA: methicillin-resistant Staphylococcus aureus NICHD: National Institute of Child Health and