Inclusion Criteria:

   - Case Surveillance: Live born infants with gestational age of at least 22 weeks and
   birth weight >400 g and <72 hours of age who are delivered at NRN hospitals and have
   early-onset sepsis and meningitis defined as isolation of a pathogen from blood or CSF
   obtained within 72 hours of birth and provision of appropriate antibiotic treatment
   for 5 or more days (or <5 days if death occurs while receiving antibiotic therapy).

   - Controls: Live born infants with gestational age of at least 22 weeks and birth weight
   >400 g who are delivered at NRN hospitals and have not been evaluated for early-onset
   sepsis (<72 hours of age) or if evaluated, they have sterile blood and/or CSF cultures
   and were not treated with prolonged antibiotics for clinical "culture negative"
   sepsis. Controls for infants with Gram-negative infection will be infants without
   early-onset infection. Controls for infants born to mothers with clinical
   chorioamnionitis will be infants without early-onset infection born to mothers with
   clinical chorioamnionitis. Control infants will be born at the same hospital as cases,
   with the same gestational age grouping as cases (22 0/7 - 28 6/7 weeks; 29 0/7 - 33
   6/7 weeks; 34 0/7 - 36 6/7 weeks; and ≥ 37 weeks).

Exclusion Criteria:

   - Stillbirths and infants who die in the delivery room will be excluded.

   - Infants who die within 12 hours of age will be excluded if they have not been
   evaluated for possible infection-ie, do not have a blood culture obtained to identify
   EOS.