Risk factors for invasive, early-onset Escherichia coli infections in the era of widespread intrapartum antibiotic use.

OBJECTIVE: The goal was to evaluate risk factors for invasive Escherichia coli infections in the first week of life (early onset), focusing on the role of intrapartum antibiotic use.

METHODS: We conducted a retrospective case-control study. Between 1997 and 2001, case infants, defined as infants < 7 days of age with E coli isolated from blood or cerebrospinal fluid, were identified in selected counties of California, Georgia, and Connecticut by the Active Bacterial Core Surveillance/Emerging Infections Program Network. Control infants (N = 1212) were identified from a labor and delivery record review of a stratified random sample of live births at the same hospitals in 1998 and 1999.

RESULTS: Surveillance identified 132 E coli cases, including 68 ampicillin-resistant cases. The case fatality rate was 16% (21 of 132 cases). Two thirds of case infants were preterm, and 49% (64 of 132 infants) were born at < or = 33 weeks of gestation. Fifty-three percent of case mothers (70 of 132 mothers) received intrapartum antibiotic therapy; 70% of those received ampicillin or penicillin. Low gestational age (< or = 33 weeks), intrapartum fever, and membrane rupture of > or = 18 hours were associated with increased odds of early-onset E coli infection. Results were similar when case subjects were limited to those infected with ampicillin-resistant strains. Exposure to any intrapartum antibiotic treatment, beta-lactam antibiotic treatment, or > or = 4 hours of intrapartum antibiotic therapy was associated with increased odds of E coli infection and ampicillin-resistant infection in univariate analyses. Among preterm infants, intrapartum antibiotic exposure did not remain associated with either outcome in multivariable models. Among term infants, exposure to > or = 4 hours of intrapartum antibiotic therapy was associated with decreased odds of early-onset E coli infection.

CONCLUSIONS: Exposure to intrapartum antibiotic therapy did not increase the odds of invasive, early-onset E coli infection. Intrapartum antibiotic therapy was effective in preventing E coli infection only among term infants.