Rapid Visual Detection of Pathogenic Streptococcus suis Type 2 through a Recombinase Polymerase Amplification Assay Coupled with Lateral Flow Test

Streptococcus suis serotype 2 (SS2) is an important zoonotic pathogen causing serious disease and even death in pigs and humans. Public health events and economic losses caused by SS2 have prompted widespread concern. Because of the unavailability of vaccines, the development of rapid detection methods for timely diagnosis of SS2 infection or contaminated products, and monitoring of its prevalence in susceptible animals and populations, is required to aid in the prevention and control of SS2 infections. Several sets of primers and one probe for a recombinase polymerase amplification (RPA) assay targeting the cpsJ2 gene were designed and synthesized. Lateral flow (LF) tests in combination with RPA were used to provide visual results. Primers with high amplification efficiency were screened, and the reaction system was optimized. Indicators of detection effectiveness were evaluated. The established method had a detection limit of 100 copies/reaction for recognizing SS2 rather than other organisms. The sensitivity was 100%, as evaluated in infected animal samples. The detection could be completed within 20 min and required only constant temperature equipment. The established rapid, visual, sensitive and specific RPA-LF assay showed superior detection performance and is expected to be widely applied to fight SS2 infection in resource-limited areas.