Background: Group B streptococcus (GBS) is a common cause of early-onset neonatal sepsis in both developed and developing countries. Neonatal Early-Onset Disease (0-6 days of life) is acquired from mothers with vaginal/rectal colonization with GBS. Laboratory detection of GBS colonization status in pregnant women is therefore important for the selective prescription of antibiotic for the prevention of complications arising from Group B Streptococcus infection.Culture based screening has its limitations including poor turn -around time, and patients lost to follow up. The GeneXpert GBS ® (Cepheid) is a rapid screening test that can be performed intrapartum. Such a test should compare favourably to culture based screening methods.Methods & Materials: A total of 85 pregnant women who were between 27 and 37 weeks gestation were enrolled from a single large maternity clinic in our region. Three swabs were collected from each participant: 1 vaginal, 1 rectal and 1 vagino-rectal (Copan TM ). Each of the swabs was plated on Granada medium. The presence of typical orange colonies on the Granada medium were confirmed by Streptex ® agglutination. The vagino-rectal swab was also used for the GeneXpert GBS assay which was performed according to the manufacturer's instructions.Results: Twenty-five (29%) women were colonized by GBS by the Granada medium. Xpert GBS detected 23/85 (27%) positives. The Xpert GBS missed two specimens that were positive by culture and identified one additional positive, with a sensitivity of 87.5% and specificity of 98.4%. The PPV was 95.5% and NPV 95.2%.Conclusion: Xpert GBS had excellent performance compared to culture. Our study is the first in South Africa to evaluate the performance of Xpert GBS compared to the Granada medium for the rapid screening of pregnant women for GBS colonization. This realtime PCR assay is a potentially accurate test to identify GBS carriers at point of care. The Xpert GBS could enhance the identification of candidates for intrapartum antibiotic treatment, including women with preterm rupture of membranes or preterm labour.

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