Comparison of a quantitative Real-Time PCR Assay and droplet digital PCR Assay for detection of Streptococcus agalactiae

Background :Streptococcus agalactiae(GBS) is pathogenic bacterium that causes puerperal sepsis in pregnant women and meningitis in newborns. Reliable detection methods for GBS included culture-based approaches, antigen-antibody method and real-time quantitative PCR. However, these methods have low sensitivity and are time consuming. In this study, we established a new detection approach, i.e. droplet digital PCR (ddPCR), for more accurate detection of GBS. Materials and Methods : Clinical specimens infected with GBS were analyzed using culture method. QPCR and ddPCR were used to quantify GBS related genes (CpsE and Sip gene). All experiments were run in triplicate using the same positive strain to verify the repeatability of the methodology. Results: The ddPCR showed outstanding accuracy, with 100% sensitivity, 100% specificity and coefficient of variation =4.5%. Among the detected strains, only positive results were obtained for the CpsE gene by ddPCR, and the detection sensitivity was 5pg/μL. Compared to the level of individual nanogramme-sized(0.5ng/μL) of qPCR assay, ddPCR resulted as a more significantly accurate method for detection of GBS in precision medical area. Conclusions : Droplet digital PCR offers high sensitivity, accuracy and repeatability, and is a suitable approach for detection of positive GBS samples.