Rectal colonization by group B Streptococcus as a predictor of vaginal colonization.

Abstract

The purpose of this article was to describe rectal colonization by group B Streptococcus (GBS) and its role in the prediction of vaginal colonization. In this prospective cohort of 1248 nonpregnant women, vaginal and rectal swabs for GBS culture were obtained at enrollment and at three 4-month intervals. Generalized estimating equations were used to identify factors that are associated with colonization. Eight hundred fourteen (65%) women had GBS colonization sometime during the observation period. Rectal GBS colonization was the strongest predictor of vaginal colonization (adjusted odds ratio, 14.3; 95% CI, 11.9-17.1). Recent sexual intercourse, vaginal colonization with yeast, and a vaginal Nugent score >/= 4 were also independent determinants of vaginal GBS colonization. Antimicrobial use decreased vaginal GBS colonization only among women who had no rectal colonization. GBS in the gastrointestinal tract is a risk factor for vaginal GBS. Sexual activity and abnormal vaginal microflora are independent determinants of vaginal GBS colonization.