Comparison of culture and 2 real-time polymerase chain reaction assays to detect group B Streptococcus during antepartum screening

Group B Streptococcus (GBS) is the most common cause of life-threatening infection in neonates but is preventable if the mother is diagnosed before and treated at delivery. Using 200 vaginal–rectal swabs inoculated to enrichment (LIM) broths, we compared routine culture and 2 real-time polymerase chain reaction (PCR) assays for detection of GBS: the LightCycler (LC) Strep B analyte-specific reagents (ASRs) (Roche Diagnostics, Indianapolis, IN) and the BD GeneOhm StrepB (BD-StrepB) test (BD GeneOhm Sciences, San Diego, CA). Culture detected 26.5% GBS-positive specimens, whereas the LC Strep B ASR and BD-StrepB test identified 29.5% and 30.0% positive specimens, respectively. Because of the increased detection rate of 3.0% to 3.5% observed with PCR, a second GBS-specific amplicon was sequenced to confirm the presence of GBS that was not detected by culture. In our hands, the sensitivity/specificity of the LC Strep B ASR was 100%/95.9%, and the BD-StrepB test was 92.5%/92.5% using culture as the gold standard.