Abstract: In this study, four serotype-specific genes of Salmonella Paratyphi A were identified by comparative genomics and PCR. A PCR assay based on the gene_3105 and invA gene was developed and evaluated for the detection of S. Paratyphi A. The electrophoresis pattern showed only two bright specific bands at 284 bp and 384 bp in S. Paratyphi A. The PCR protocol was optimized and the specificity, sensitivity, anti-jamming capability and limit of detection (LOD) for artificially contaminated food were evaluated．The specificity results showed two bright specific bands for S. Paratyphi A, only one specific band at 284 bp for other Salmonella serotypes, no specific bands for non-Salmonella strains. The sensitivity of the PCR assay was 32.4 pg/μL and 4.3 × 103 CFU/mL for genomic DNA and pure colonies, respectively. In the presence of natural background flora enriched from chicken and pork breast samples, the detection limit was 6.43 × 104 CFU/mL. In artificially contaminated chicken and pork, the detection limit was N CFU/25 g after 10 h enrichment (0 < N < 10). In conclusion, the PCR assay for the detection of S. Paratyphi A is specific and sensitive, and has a good application value and can be widely used in the field of food safety.

Key words: Salmonella Paratyphi A, comparative genomics, serotype-specific genes, PCR