A Rapid Molecular Detection Method for Streptococcus agalactiae Based on Bacteriophage Lysin Lysis and Real-Time PCR.

PURPOSE: Streptococcus agalactiae (Group B Streptococcus, GBS) is a leading cause of neonatal infections. This study aimed to establish a rapid GBS detection method using a bacteriophage lysin-based lysis approach. METHODS: Specific primers and probes were designed for GBS cylA gene and human ACTB gene. A rapid nucleic acid extraction and purification method was established for GBS, achieving complete lysis and extraction within 5 min through the use of a bacteriophage lysin. A point-of-care assay was developed using real-time fluorescence quantitative PCR. In Phase I, 331 vaginal swab samples were tested by POCT and conventional culture; in Phase II, 180 separate samples were tested by POCT, culture, and antigen testing. RESULTS: The assay completed nucleic acid extraction within 5 min and PCR amplification within 30 min, resulting in a total turnaround time of 35 min. Culture required 18-48 h. The assay had a detection limit of 2,000 copies/mL and no cross-reactivity. In the Phase I cohort, the assay achieved 100% sensitivity and 94.24% specificity. Following 16 S rDNA sequencing confirmation of discordant samples, the adjusted specificity increased to 97.76%. In the Phase II cohort, the assay showed higher sensitivity than the antigen test (100% vs. 58.06%). CONCLUSIONS: We developed a rapid GBS molecular assay centered on bacteriophage lysin lysis. The assay showed high diagnostic performance in the study cohorts and has potential for intrapartum or near-patient screening, although real-world workflow feasibility requires further validation. CLINICAL TRIAL NUMBER: Not applicable.