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Updated: May 30, 2026
A Murine Model of Group B Streptococcus Vaginal Colonization
Published on: November 16, 2016
The effect of intrapartum clindamycin on vaginal group B streptococcus colony counts
Kristin M Knight1, Loralei L Thornburg, Anna R McNanley
1Department of Obstetrics and Gynecology, Division of Maternal Fetal Medicine, University of Rochester Strong Memorial Hospital, USA. kristin_knight@urmc.rochester.edu
Objective:
To determine the temporal relationship between intrapartum clindamycin and vaginal Group B Streptococcus (GBS) colony counts.
Methods:
In this prospective observational study, women with GBS-positive, clindamycin-sensitive, antenatal rectovaginal cultures, intrapartum vaginal cultures were collected just before the first clindamycin dose (T(0)) and then every 2 h for 8 h or until delivery. Colony counts were quantified using serial dilution. Results were standardized as percent of initial colony count and analyzed using sequential Friedman tests.
Results:
Twenty-one women had positive intrapartum vaginal GBS cultures at T(0). With T(0) colony counts standardized to 100%, subsequent percents-of-baseline fell rapidly and significantly by T(2) and fell further at each subsequent point, reaching 0% by T(6). For 12 women cultured for the full 8 hours, the decline in GBS was significant at p < 0.001.
Conclusions:
Vaginal GBS colony counts fall rapidly after intrapartum clindamycin administration, similar to declines after penicillin. This represents a possible mechanism for efficacy of chemoprophylaxis.
