A duplex real-time NASBA assay targeting a serotype-specific gene for rapid detection of viable Salmonella Paratyphi C in retail foods of animal origin

Salmonella enterica serovar Paratyphi C is highly adapted to humans and can cause a typhoid-like disease with high mortality rates. In this study, three serovar-specific genes were identified by comparative genomics for Salmonella Paratyphi C, SPC_0871, SPC_0872, and SPC_0908. Based on the SPC_0908 and xcd genes for testing Salmonella spp., we developed a duplex real-time nucleic acid sequence-based amplification (real-time NASBA) with a molecular beacon approach for the simultaneous detection of viable cells of Salmonella spp. and serotype Paratyphi C. The test selectively and consistently detected 53 Salmonella spp. (representing 31 serotypes) and 18 non-Salmonella strains. Additionally, the method showed high resistance to interference from natural background flora in pork and chicken samples. The sensitivity of the established approach was determined to be 4.89 cfu/25 g in artificially contaminated pork and chicken samples after pre-enrichment. We propose this NASBA-based protocol as a potential detection method for Salmonella spp. and serotype Paratyphi C in foods of animal origin.