CRISPR-based sensing platform for the Group B streptococcus screening in pregnant women

Group B Streptococcus (GBS) is a major cause of perinatal infections. Prenatal screening is critical to prevent maternal and neonatal GBS infections, reduce adverse outcomes, and guide clinical interventions. While bacterial culture is the gold standard, it is time-consuming and delays decision-making. Rapid molecular tests like PCR are sensitive and specific but require expensive equipment and skilled personnel. Point-of-care tests (e.g., Xpert GBS LB) offer speed and sensitivity but remain costly and underutilized. This study aims to develop a portable CRISPR/Cas13a-based device for rapid, on-site GBS detection.

A palm-sized CRISPR detection platform, PalmCS, was developed. PalmCS includes two key components: an integrated tube for nucleic acid extraction, gene amplification, and CRISPR-based reaction, and a multifunctional device for thermal regulation, fluorescence detection, and automatic result interpretation. The sealed plug needle valve controls fluid flow for sample input and result output. By optimizing crRNA selection, Cas13a/crRNA ribonucleoprotein (RNP) complex concentrations, and isothermal recombinase polymerase amplification primers, we established a one-pot CRISPR/Cas13a-RPA method for GBS detection. Results showed that 3 M guanidinium salt combined with 5 % Tween 20 achieved the highest extraction efficiency. The system extracted nucleic acids from samples in 5 min at room temperature, demonstrating its potential for rapid diagnostics. PalmCS was validated using 40 clinical samples, achieving a limit of detection (LOD) of 20 copies/reaction, 97.5 % sensitivity, and 100 % specificity.

This study used a one-step nucleic acid extraction combined with a closed one-pot RPA-CRISPR reaction for rapid, sensitive, and specific GBS detection. This provides a new platform for prenatal screening in pregnant women. In resource-limited settings with emergency deliveries, PalmCS enables on-site GBS testing, allowing antibiotic administration during delivery for positive cases to significantly reduce neonatal infection risk.