Comparison of scpB gene and cfb gene polymerase chain reaction assays with culture on Islam medium to detect Group B Streptococcus in pregnancy

Purpose: The purpose of the current study was to evaluate two low-costing PCR assays for rapid detection of Group B Streptococcus (GBS) in comparison to a pigment-based culture method.
Materials and Methods: One-hundred and fifty vaginal swabs were collected from pregnant women at 35-40 weeks of gestation. Vaginal swabs were inoculated in selective enrichment broth medium, and examined using Islam medium, cfb PCR and scpB PCR assays. The demographic data were analysed to identify independent predictors of GBS colonization (age and gravidity), with GBS status as the dependent variable.
Results: There was a significant association of age and gravidity with GBS colonization. GBS was detected in 25.3% of isolates by Islam medium, in 30.6% by using the cfb PCR assay and in 30% by using the scpB PCR assay.
Conclusion: Older pregnant women (≥30 years) and multigravida (>3 pregnancies) are at higher risk of GBS colonization. Both scpB-gene and cfb-gene-based PCR methods are highly sensitive techniques (100% sensitivity) compared to culture method. However, the specificities of the scpB and cfb PCR assays were 93.75 and 92.85%, respectively.

Keywords
Group B Streptococcus, Vaginal swab, Islam medium, scpB-gene-based PCR, cfb-gene-based PCR