1.3.1 RPA primer design
In this study, the highly conserved sequence IS711 (Genebank No. AF242532) gene was selected as the target sequence from the National Center for Biotechnology Information (NCBI), then used Premier 5.0 software to design RPA forward and reverse primers (Gumaa et al., 2019) based on primer design principles (Table 1). Through the BLAST (The Basic Local Alignment Search Tool) to compare the primer sequences with the genomes of the cross strains Yersinia enterocoliticaO:9, Escherichia coli O157, Salmonella enterica serovarUrbana O:30, and Francisella tularensis to determine the primer specificity; Primers was synthesized by Sangon Biotech (Shanghai, China).