Early-Onset Group B Streptococcal Disease in the Era of Maternal Screening

Abstract

Although the wide use of intrapartum antibiotic prophylaxis (IAP) has markedly reduced early-onset neonatal sepsis and meningitis caused by Streptococcus agalactiae (group B streptococcus [GBS]), especially in term infants, GBS disease continues to occur and to cause significant morbidity and mortality. Factors responsible for persistent early-onset GBS disease (EOGBS) were sought in a retrospective review of culture-proved EOGBS seen on a single large maternity service in the years 1997 through 2003. A total of 67,260 infants were live-born during this time. Of 25 cases of EOGBS identified during the period under review, 5 occurred in very-low-birth-weight (VLBW) infants weighing 400 to 1499 g at birth. The overall incidence of EOGBS was 0.37 cases per 1000 live births, and the rate in VLBW infants was 3.3 per 1000 births. Risk estimates for EOGBS had lessened in the overall group and VLBW group since adoption of a risk-based protocol for intrapartum antibiotic prophylaxis (IAP), but no further decline was noted after changing to a screening-based protocol. Seventeen of the 25 cases identified after instituting a screening-based protocol—approximately two thirds—occurred in term infants; there was a single death. Three of the 8 preterm infants died. More than 80% of mothers of term infants had been GBS-negative when screened. A majority of these mothers had intrapartum risk factors for neonatal infection but did not receive antibiotics before delivery. Only one of the 25 women in the study received adequate IAP. In 4 instances, either documented GBS colonization went unrecognized or an infant at risk of sepsis was not evaluated. Five of 25 isolates (20%) were resistant to clindamycin and/or erythromycin, and 5 others were partially resistant to erythromycin or clindamycin. None of the invasive isolates were resistant to penicillin, ampicillin, cephalosporin, or vancomycin. Screening for GBS disease has substantially lowered the overall rate of neonatal EOGBS. In the present review, a majority of cases occurred in infants whose mothers had been screen-negative for GBS colonization. Two measures are important: prompt IAP for women with clinical evidence of chorioamnionitis regardless of the screening results and evaluation of normal-appearing infants for possible sepsis.