[Is rapid intrapartum vaginal screening test of group B streptococci (GBS) during partum useful in identifying infants developing early-onset GBS sepsis in postpartum period?]

Introduction: Group B streptococcus (GBS) is the most common infectious agent responsible for early-onset bacterial sepsis (EOS) in term newborns. French prevention of perinatal GBS disease guidelines recommend screening for maternal vaginal GBS colonization at the 9th month of pregnancy, and use of intrapartum antibiotic prophylaxis (IAP) in case of detected GBS vaginal colonization. Peripheral bacterial sampling (gastric aspiration, ear, or meconium) and measurement of C-reactive protein (CRP) are performed in asymptomatic newborns in case of infectious risk factors and/or incomplete IAP.

Objective: The aim of this study was to investigate the relation between a rapid intrapartum screening test for GBS during labor in term parturients and infants developing GBS EOS and in comparison to current recommendations.

Methods: We conducted an observational analytic single-center study, with use of a rapid intrapartum GBS screening test, at Toulouse University Hospital.

Results: A total of 1416 mother-newborn dyads were prospectively included between 31/01/2012 and 17/08/2012. Vaginal GBS colonization was found at the 9th month of pregnancy in 148 mothers (10.6 %), and 176 mothers (12.5 %) were screened positively at delivery using intrapartum GBS rapid polymerase chain reaction assay (GBS PCR) (P=0.025). No confirmed neonatal GBS EOS was found. Nine infants had suspected GBS EOS because of a positive peripheral bacterial finding and elevated CRP. In these infants, seven pregnant mothers were GBS-positive with GBS PCR assay during labor, and four women were positive on prenatal culture at the 9th month of pregnancy. The diagnostic values of the two tests highlighted a nonsignificant superiority of intrapartum GBS PCR assay (AUC=0.83 [0.68-0.97] vs. 0.67 [0.50-0.84]), (P=0.057). The negative predictive value was improved with intrapartum PCR assay (negative likelihood ratio [LR]: 0.3 [0.1-0.9] vs. 0.6 [0.4-1.1]). Intrapartum GBS PCR assay provided its best positive predictive value in the absence of complete AIP and without other infectious factors (positive LR: 21.3 [15.4-29.5]).

Conclusion: These results suggest that the intrapartum GBS PCR assay offers a better predictive value of GBS EOS than the usual vaginal culture swab at the 9th month but requires confirmation by large studies.