Establishment and clinical application of a rapid RPA-LFS assay for detecting Moraxella catarrhalis

Moraxella catarrhalis (M. catarrhalis) is an important opportunistic pathogen causing respiratory tract infections, and current detection methods are limited by low sensitivity, heavy instrument dependence or complex operation, which cannot meet the needs of rapid clinical and on-site testing.

The copB gene is a species-specific conserved gene of M. catarrhalis, which was selected as the target for specific detection. Primers and probe were designed using Primer Premier 5.0 software and online tools. The limit of detection was determined using standard strains, and the clinical applicability of the recombinase polymerase amplification-lateral flow strip assay (RPA-LFS) was evaluated by testing 300 clinical samples. Culture combined with real-time quantitative PCR (qPCR) was applied as the composite reference standard to evaluate clinical diagnostic performance.

The optimized RPA-LFS assay was incubated at 37 °C for 15 minutes, which specifically detected all 20 M. catarrhalis strains without cross-reactivity with other pathogens, and its limit of detection reached 13.4 CFU/mL without interference from heterologous bacterial DNA. The clinical sensitivity and specificity of RPA-LFS were 96.26% and 88.08%, respectively.The positive detection rate of the assay in clinical specimens was 42%, significantly higher than that of PCR (15%) and conventional culture (9%).

The established copB-based RPA-LFS assay is rapid, simple, instrument-independent, highly sensitive and specific, with excellent clinical detection performance, which can serve as an effective technical tool for the rapid and on-site detection of M. catarrhalis and support early clinical diagnosis of its infections.