Neonatal Early-Onset Group B Streptococcal Disease in the Era of Intrapartum Chemoprophylaxis: Residual Problems

Abstract

Guidelines for intrapartum antibiotic prophylaxis appear to have reduced the incidence of early-onset group B streptococcal (GBS) infection, but it still is a major cause of early-onset neonatal sepsis and infectious mortality in newborn infants in the United States. The authors reviewed 92 infants admitted to one of two university-affiliated nurseries in the years 1992 through 2001 at age 7 days or less with culture-proved GBS disease. The mean age at the onset of symptoms was 2.5 hours. Only one infant was diagnosed after death. No intrapartum prophylaxis was given to 68 women, half of whom were known before delivery to have risk factors for early-onset GBS infection. Of 32 infants with clinical risk factors, 22 had a gestational age less than 37 weeks. Less frequent risk factors were ruptured amniotic membranes for 18 hours or longer, intrapartum maternal fever, and previous GBS bacteriuria. In several cases, there was more than one risk factor. Four of 22 women having rectovaginal cultures for GBS were positive, but proper culture medium was not consistently used. Intrapartum prophylaxis was withheld in 18 women who were screen-negative for GBS colonization. Fourteen of 68 infected infants required extracorporeal membrane oxygenation and three infants died. The absence of clinical risk factors or known maternal colonization did not protect these infants. Twenty-four women received what were thought to be adequate doses of antibiotic prophylaxis, most frequently ampicillin. All of these women had risk factors and a majority had multiple risk factors. Five of six studies for maternal rectovaginal colonization were positive. In 15 cases, prophylaxis lasted less than 4 hours. All infants became ill in the first 24 hours of life. Two required extracorporeal membrane oxygenation and one died. These findings suggest that early-onset GBS disease can occur despite appropriate prophylaxis. Possible improvements include a rapid and practical test for GBS colonization, development of effective vaccines, and studies of adjunctive postnatal prophylaxis.