Duration of Antimicrobial Prophylaxis for Group B Streptococcus in Patients With Preterm Premature Rupture of Membranes Who Are Not in Labor

Abstract

Group B streptococcus (GBS), which colonizes as many as 30% of pregnant women, remains a major cause of serious neonatal infection. GBS may be transmitted by ascending infection after rupture of the fetal membranes or may be acquired during vaginal delivery. Disease may develop within or after the first week of life. The investigators conducted a retrospective cohort study of pregnant women with preterm premature rupture of membranes (PPROM) before 37 weeks' gestation—a condition accounting for nearly 40% of all preterm births. Cultures from the lower third of the vagina and rectum were obtained on admission and each day thereafter, and intravenous antibiotics were given until cultures were negative for 3 consecutive days. The authors hypothesized that GBS can be cleared from the genital tract with fewer than 3 days of antimicrobial therapy. All patients received an antepartum course of betamethasone or dexamethasone. Penicillin G was the primary prophylactic antibiotic; a loading IV dose of 5 million units was followed by 2.5 million units every 4 hours. Patients allergic to penicillin received clindamycin instead. Of 169 patients taking part in the study, 33 (19.5%) were GBS-positive when admitted. Counting multifetal pregnancies, there were 140 neonates in the GBS-negative group and 35 in the GBS-positive group. Neonatal sepsis developed in 19 newborn infants (11.2%), 3 of whose mothers were GBS-positive at admission. In no instance was neonatal sepsis a result of GBS infection. Genital tract cultures for GBS were negative by day 2 in all but one patient, and by day 3 in all instances. All but 2 of the GBS-positive patients received penicillin G. None of the GBS-negative group became GBS-positive after 2 consecutive days of negative cultures. The overall incidence of positive blood cultures in neonates whose mothers had PPROM was 10.9%. In pregnant women presenting with PPROM, 3 days of prophylaxis with IV antibiotic, penicillin G in the present study, reliably eradicates GBS from the genital tract. Further studies are needed to learn whether even shorter courses of antimicrobial therapy are effective.