OBJECTIVE. The goal was to determine current trends in Escherichia coli-related early- and late-onset sepsis and patterns of ampicillin resistance in relation to institutional changes in the use of intrapartum antibiotic prophylaxis.

METHODS. A retrospective review of data for all infants with E coli sepsis at Yale-New Haven Hospital from 1979 to 2006 was performed. Study periods were based on predominant intrapartum antibiotic prophylaxis practices at Yale-New Haven Hospital, that is, (1) 1979 to 1992 (no formal intrapartum antibiotic prophylaxis), (2) 1993 to 1996 (risk factor-based), and (3) 1997 to 2006 (screening-based). Sepsis rates and patterns of ampicillin resistance were compared.

RESULTS. Fifty-three cases of E coli early-onset sepsis and 129 cases of E coli late-onset sepsis were identified over 3 eras. In very low birth weight (<1500 g) infants, increases in E coli early-onset sepsis (period 1: 2.83 cases per 1000 very low birth weight admissions; period 2: 7.12 cases per 1000 very low birth weight admissions; period 3: 10.22 cases per 1000 very low birth weight admissions), intrapartum ampicillin exposure, and ampicillin-resistant E coli were observed. Intrapartum ampicillin exposure was determined to be an independent risk factor for ampicillin-resistant E coli early-onset sepsis. For the first time, a significant increase in E coli late-onset sepsis was observed in preterm infants (period 1: 10.39 cases per 1000 very low birth weight admissions; period 2: 16.01 cases per 1000 very low birth weight admissions; period 3: 21.66 cases per 1000 very low birth weight admissions) and term infants (period 1: 4.07 cases per 1000 admissions; period 2: 4.22 cases per 1000 admissions; period 3: 8.23 cases per 1000 admissions).

CONCLUSIONS. Studies to provide a better understanding of potential consequences of intrapartum antibiotic exposure and its contribution to evolving trends in neonatal sepsis are urgently needed.

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