Development of a recombinase polymerase amplification nucleic acid lateral flow assay for detecting Streptococcus suis serotype 2 in pork.

Streptococcus suis is a major pathogen in pigs, causing diseases like meningitis, septicemia, and pneumonia, and has become a serious zoonosis in humans, particularly in countries with intensive swine production. Human infections have risen significantly, especially in Thailand, where serotype 2 is most commonly associated with disease in both pigs and humans. Traditional methods of identifying S. suis and its serotypes, such as bacterial culture, biochemical testing, and agglutination tests, face challenges due to variability and limited antisera availability, leading to the need for alternative approaches. In this study, we developed a novel RPA-NALFIA assay targeting the recN and cps2J genes of S. suis serotype 2. This method demonstrated accurate identification without cross-reactivity among 28 other bacterial species, with a detection limit of 103 CFU/mL, comparable to PCR methods. Food safety concerns are heightened by the discovery of S. suis contamination in pork, a major infection route when consumed undercooked. Our surveillance in central Thailand revealed that 49.3% of pork samples were contaminated with S. suis, with serotype 2 detected in 2.6% of samples. The RPA-NALFIA method proved effective, showing 100% sensitivity and 97.5% specificity. This assay offers rapid, reliable detection suitable for point-of-care testing in resource-limited settings.