TUESDAY, Dec. 18 (HealthDay News) -- Vaginal group B streptococcus (GBS) colony counts fall quickly and dramatically with intrapartum doses of penicillin-G, researchers report in the December issue of the American Journal of Obstetrics & Gynecology.
Anna R. McNanley, M.D., of the University of Rochester Medical Center in Rochester, N.Y., and colleagues obtained and analyzed vaginal cultures from 50 women in labor who had tested positive for GBS. Beginning just before the initial intravenous antibiotic administration, vaginal cultures were collected every two hours up to four times or until delivery, whichever came first.
Thirty-five of the 50 women (70 percent) had positive intrapartum vaginal cultures, of which 27 received intrapartum penicillin-G. The researchers found that the mean vaginal GBS counts of women receiving the antibiotic declined fivefold in the first two hours of antibiotic treatment and 50-fold by four hours. By six hours, mean GBS counts had declined nearly 1,000-fold. They remained at that level at the eight-hour conclusion of the study period.
"We postulate an important role for penicillin-G's direct effect as a component of efficacy in GBS prophylaxis," the authors conclude.
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