Development of a reliable method to diagnose Streptococcus agalactiae infection by droplet digital PCR

Background: Streptococcus agalactiae (GBS) is the causative pathogen of puerperal sepsis in pregnant women and meningitis in infants. Infection of GBS is responsible for the increased morbidity in pregnant women and the elderly, and bring challenges to clinical diagnosis and treatment. However, culture-based approaches to detect S.agalactiae is time-consuming with limited sensitivity. Besides, real-time quantitative PCR demand for expensive instruments with tedious steps. Thus, we aim to establish a new detection method for more accurate and rapid detection of S.agalactiae. Results: : The ddPCR primer targeted the CspE gene showed a better amplified efficiency in the reaction. The limitation of ddPCR for identifying GBS DNA was able to reach 5 pg/µL. Moreover, no positive amplified signals could be detected in the reactions which served 11 non-GBS strains DNA as templates. Furthermore, the coefficient of variation of this method is 4.5%, indicating an excellent repeatability of ddPCR assay. Conclusions: In our study, ddPCR was performed as a rapid detection of S.agalactiae with high sensitivity and specificity. This technique can promote the accuracy of the diagnosis of GBS infection and provide a scientific basis for clinical treatment.