Rapid and visual detection of group B Streptococcus based on an ERA-CasMNPs colorimetric biosensor

Group B Streptococcus (GBS) is a major pathogen responsible for adverse perinatal outcomes; rapid and accurate detection is crucial for preventing maternal-neonatal transmission and for guiding clinical interventions. Current GBS detection methods are limited by long assay times, insufficient sensitivity, and high equipment and operational requirements, restricting their application in resource-limited settings and rapid detection scenarios. Targeting the cfb gene of GBS, this study developed ERA-CasMNPs by integrating enzymatic recombinase amplification (ERA), CRISPR/Cas12a-mediated specific recognition and trans-cleavage activity of ssDNA, and horseradish peroxidase (HRP)-modified magnetic nanoparticle complexes (MNPs)-based colorimetric signal output. The ERA-CasMNPs biosensor enables rapid and sensitive visual detection of GBS within 85 min, with an LOD₉₅ of 23.3 copies/μL (95% confidence interval: 15.6-34.8 copies/μL). Moreover, evaluation using 135 cultured clinical bacterial isolates demonstrated that ERA-CasMNPs achieved a sensitivity of 97.33%, a specificity of 98.33%, and a detection accuracy of 97.78%, comparable to qPCR. These results indicate that the ERA-CasMNPs biosensor provides a sensitive and visual method for rapid detection of GBS and supports its potential for further evaluation in resource-limited and rapid-testing settings.