A novel visual loop-mediated isothermal amplification assay targeting gene62181533 for the detection of Salmonella spp. in foods

In this study, we developed a rapid and sensitive loop-mediated isothermal amplification (LAMP) assay for Salmonella detection targeting the gene62181533. The addition of manganous ions and calcein to the reaction system allowed the visualization of an apparent color change during the amplification reaction. The detection limit of LAMP using a six-primer combination was 1.057 copies/μl (standard plasmid), 4.1 CFU/ml (cell), and 7.68 fg/μl (genome). The LAMP assay was 100% specific based on 32 Salmonella strains and 25 non-Salmonella bacteria. In inoculated milk, the LAMP assay detected Salmonella at an initial inoculation concentration of 0.81 CFU/ml following 12 h of pre-enrichment in buffered peptone water. One hundred food samples (beef, chicken, and pork) were tested by the LAMP assay. The positive-sample ratios were 11/100 by LAMP, 11/100 by conventional PCR, and 11/100 by a culture-based method. The results revealed that the gene62181533-based LAMP assay is a rapid, specific, and sensitive method for the detection of Salmonella in foods.