Background. Early-onset group B streptococcal (GBS) prevention efforts are based on targeted use of intrapartum antibiotic prophylaxis (IAP); applicability of these prevention efforts to infections caused by other organisms is not clear.Methods. Multicenter surveillance during 1995 to 1996 for culture-confirmed, early-onset sepsis in an aggregate of 52?406 births; matched case-control study of risk factors for GBS and other sepsis.Results. Early-onset disease occurred in 188 infants (3.5 cases per 1000 live births). GBS (1.4 cases per 1000 births) and Escherichia coli (0.6 cases per 1000 births) caused most infections. GBS sepsis less often occurred in preterm deliveries compared with other sepsis. Compared with gestation-matched controls without documented sepsis, GBS disease was associated with intrapartum fever (matched OR, 4.1; CI, 1.2–13.4) and frequent vaginal exams (matched OR, 2.9; CI, 1.1–8.0). An obstetric risk factor—preterm delivery, intrapartum fever, or membrane rupture ≥18 hours—was found in 49% of GBS cases and 79% of other sepsis. IAP had an adjusted efficacy of 68.2% against any early-onset sepsis. Ampicillin resistance was evident in 69% of E coli infections. No deaths occurred among susceptible E coli infections, whereas 41% of ampicillin-resistant E coli infections were fatal. Ninety-one percent of infants who developed ampicillin-resistant E coli infections were preterm, and 59% of these infants were born to mothers who had received IAP.Conclusions. Either prenatal GBS screening or a risk-based strategy could potentially prevent a substantial portion of GBS cases. Sepsis caused by other organisms is more often a disease of prematurity. IAP seemed efficacious against early-onset sepsis. However, the severity of ampicillin-resistant E coli sepsis and its occurrence after maternal antibiotics suggest caution regarding use of ampicillin instead of penicillin for GBS prophylaxis.
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