Analysis of vaginal and rectal sampling methods for maternal group B streptococcal isolation

Abstract

Background: Group B streptococci (GBS) is considered as an important cause of neonatal morbidity and mortality. The Centers for Disease Control and Prevention (CDC) recommends recto-vaginal sampling of pregnant women and the use of selective broth medium for GBS isolation. This study was done to evaluate the GBS yield from only vaginal, only rectal, and both rectal and vaginal swabs collected. In addition, the drawbacks of using the selective broth mediums for GBS isolation were also analyzed. Methodology: This was a prospective study that was done to screen 300 pregnant women for vaginal and rectal GBS colonization. Vaginal and rectal swabs were inoculated separately in Todd Hewitt Broth and later subcultured on blood agar for GBS isolation. Results: The GBS detection rates from both vaginal and rectal swabs were 42.9%, indicating heavy colonization in these women. In addition, our study noted certain drawbacks with the use of selective Todd Hewitt Broth medium used for GBS isolation. Conclusion: GBS isolation rate was higher when both rectal and vaginal swabs were collected. Our study also concluded that there was a need to develop alternative culture media for GBS isolation in view of the drawbacks encountered with the selective Todd Hewitt Broth medium.