OBJECTIVE:

The objective of this study was to assess the effect of maternal antibiotic exposure on neonatal early-onset sepsis (EOS) rates over an 18-year period.

METHODS:

A review was performed of infant and maternal records for all culture- proven cases of EOS in infants delivered at the Brigham and Women's Hospital (Boston, MA) in 1990–2007.

RESULTS:

Data were analyzed from 335 EOS cases over periods that differed with respect to hospital policy for intrapartum antibiotic prophylaxis against group B Streptococcus (GBS): 1990–1992 (no prophylaxis); 1993–1996 (risk-based); and 1997–2007 (screening-based). The overall incidence of EOS decreased over these periods (3.70 vs 2.23 vs 1.59 cases per 1000 live births; P < .0001). No change in the incidence of infection with ampicillin-resistant organisms was observed overall or among very low birth weight infants. However, an increased proportion of infections were caused by ampicillin- resistant organisms. Mothers of infants with ampicillin-resistant infections were more likely to have been treated with ampicillin (P = .0001). Overall peripartum antibiotic use increased during the study period primarily because of increased use of penicillin G and clindamycin, with no significant change in the use of ampicillin.

CONCLUSIONS:

Predominant use of penicillin G for GBS prophylaxis resulted in decreased incidence of EOS. No change in the incidence of ampicillin-resistant EOS was observed, but resistant cases were associated with peripartum ampicillin exposure. These findings suggest that obstetricians should consider preferential use of penicillin G for GBS prophylaxis.

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