Abstract
Objective To define the temporal relationship between intrapartum intravenous vancomycin administration
and vaginal group B streptococcus (GBS) colony counts.
Study Design Prospective cohort study conducted from October 2014 to February 2017. Women with
antenatal cultures demonstrating GBS colonization and a plan for vancomycin administration
were eligible. Intrapartum vaginal cultures were collected prior to the first vancomycin
infusion and every 2 hours up to five collections or delivery. Results were analyzed
in two groups: participants with at least one positive intrapartum culture and those
without any positive intrapartum cultures.
Results A total of 63 women were enrolled. Among consented women, a total of 8 were excluded
and 3 participants' cultures were never plated, thus leaving a total of 52 women for
analysis. The degree of vaginal GBS colonization varied between subjects and was not
normally distributed. Colony counts dropped rapidly from hour 0 to hour 2 (median:
6.0 × 108 vs. 1.0 × 108, p < 0.01). Standardizing hour 0 colony counts to 100%, the percent decline in colony
counts from hour 0 to hour 2 was significant (p = 0.03), and at each subsequent time point fell further.
Conclusion GBS vaginal colony counts fall rapidly after intrapartum vancomycin administration.
Keywords
GBS prophylaxis - intrapartum antibiotics - intrapartum antibiotic prophylaxis - intrapartum
vancomycin - vaginal GBS colony counts - vancomycin
