Intrapartum Antibiotic Prophylaxis Effective in Decreasing Early-Onset Group B Streptococcus Infection

Abstract

Source: Puopolo KM, Madoff LC, Eichenwald EC. Early-onset group B streptococcal disease in the era of maternal screening. Pediatrics. 2005;115:1240–1246.Researchers from Brigham and Women’s Hospital in Boston investigated the reasons for persistence of early-onset group B streptococcal disease (EOGBS) at their institution since the implementation of the Centers for Disease Control and Prevention’s (CDC) screening-based protocol for intrapartum antibiotic prophylaxis (IAP) in 1997. They searched the computerized database of their microbiology laboratory for positive blood and CSF cultures obtained between January 1, 1997 and December 31, 2003 in infants less than 72 hours of age. There were 67,260 live births; 1502 were very low birthweight (VLBW) infants. Twenty-five cases of EOGBS were identified (5 in VLBW infants) and the medical records of these infants and their mothers were reviewed.The overall incidence of EOGBS infection during the study period (0.37 cases per 1000 live births) represented a significant decrease from before the use of IAP (1990–1992: 2.2 cases per 1000 live births) and from the period when a risk-based approach to IAP was used (1993–1996: 1.1 cases per 1000 live births). Incidence of EOGBS infection among VLBW infants (3.3 per 1000) decreased significantly during the study period compared to before the implementation of the CDC’s risk-based screening protocol (1990–1992: 10.1 per 1000) but not compared to the time when the CDC’s risk-based protocol was being followed (1993–1996: 3.1 per 1000). Of the 25 mothers (17 were term pregnancies) of infants born with EOGBS, 21 were screened for GBS colonization, and 16 of those screened negative (14 were term pregnancies). Nineteen (76%) of 25 mothers had deliveries complicated by ≥ 1 risk factor for EOGBS in their infants (delivery at <37 weeks’ gestation, intrapartum fever of >100.4°F, clinical chorioamnionitis, or GBS colonization) but only 4 mothers received IAP.Overall, 19 of 25 infants became ill within the first 24 hours of life. Of 17 term infants, 12 had only mild illness while 7 of 8 pre-term infants were ill from birth and 6 required ventilator support. Five infants who were well at birth but whose mothers had risk factors for EOGBS that led to evaluation and treatment with antibiotics remained clinically well. No dominant serovariant was identified among the GBS isolates and none of the isolates were resistant to the currently recommended antibiotics for IAP. Three cases of EOGBS might have resulted because of failure to give IAP to a GBS-positive mother. The authors conclude that even in the setting of a maternal GBS-screening program, efforts to evaluate and treat infants with intrapartum clinical risk factors for early-onset sepsis remain important.Dr. Rathmore has disclosed no financial relationships relevant to this commentary.The use of the CDC-recommended screening-based protocol for the prevention of neonatal EOGBS has significantly decreased the incidence of EOGBS. However, cases are still occurring. This study showed that even in the era of a screening-based protocol those mothers who have negative GBS screening but have risk factors for EOGBS should receive IAP. Even in the absence of risk factors, good clinical judgment is essential since screening techniques are not infallible. Infants with intrapartum clinical risk factors should be carefully evaluated whether or not their mothers have received IAP. Empiric antibiotic therapy should be strongly considered for those with maternal or neonatal risk factors. Until an efficacious vaccine is available for the prevention of GBS infection, all newborns should be considered at risk for EOGBS. This study showed that it was not procedural, administrative, or systemic failure or antibiotic resistance but rather the failure to consider risk factors that played a role in the development of several cases of EOGBS.