Single-dose penicillin prophylaxis against neonatal group B streptococcal infections. A controlled trial in 18,738 newborn infants.

Neonatal Group B streptococcal infections may not respond to antimicrobial therapy and have been associated with case fatality rates of 50 per cent or greater. We evaluated the effect on colonization and disease rates of a single intramuscular dose of aqueous penicillin G given at birth in a prospectively controlled study of 18,738 neonates during a 25-month period. The colonization rate in the mothers was 26.6 per cent, with 50 per cent concordance in the untreated infants and 12.2 per cent in the penicillin-treated infants (P < 0.001). There was a significant decrease in the incidence of disease caused by all penicillin-susceptible organisms in the penicillin group (0.64 vs. 2.26 cases per thousand live births, P = 0.005). Disease caused by penicillin-resistant pathogens was increased in the penicillin-treated group during the first year of the study but was unaffected during the second year. Routine administration of parenteral penicillin at birth cannot be recommended until the effect on the incidence of disease caused by penicillin-resistant pathogens is fully defined.