Abstract

Background: Bacterial vaginosis (BV) is a risk factor for premature birth and group B streptococci (GBS) colonizing the vagina are etiological agents of neonatal infections. Significant growth of GBS in the vagina has been assumed to be detectable through urinary culture. The aim was to investigate the correlation between BV and the presence of GBS in qualitative vaginal or quantitative urinary culture, since this could predict a higher risk for perinatal morbidity.

Design and setting: A consecutive prospective study of women in early pregnancy included 3101 women between 2007 and 2010, in a region of south-western Sweden.

Methods: Vaginal and urine samples were obtained from women in early pregnancy at maternity health care clinics. BV was diagnosed according to the Ison/Hay classification. GBS in urine were detected in amounts as low as 100 CFU/ml. Vaginal culturing for GBS was obtained from a selected group of 481 women.

Results: There was no difference in the prevalence of GBS in the urine among women with BV compared with women with lactobacilli flora (OR 0.7; 95% CI 0.4-1.1). Vaginal presence of GBS was found among 17.3% of women with BV and among 23.5% of women with lactobacilli flora (OR 0.7; 95% CI 0.3-1.4). Among the 105 women who had vaginal GBS, the urine culture of GBS was positive in only 21.9% of cases.

Conclusions: Even though women with BV have much higher concentration of bacteria in the vagina, they do not necessarily have more GBS in the vagina or urine. The modest correlation between positive vaginal culture and positive urine culture of GBS question the value of urinary culture for detection of vaginal GBS.

Keywords: Bacterial vaginosis, group B streptococci, pregnancy, vagina