Rapid detection of Salmonella enterica subsp. enterica serovar Thompson by real-time fluorescence loop-mediated isothermal amplification (LAMP) and colorimetric LAMP combined without DNA extraction in the field

Salmonella enterica subsp. enterica serovar Thompson (S. Thompson) has caused numerous international outbreaks of foodborne disease in recent years. Despite the need for methods to control and prevent these outbreaks, many researchers continue to focus on Salmonella species, and few studies have focused on S. Thompson. In this study, we developed the new loop-mediated isothermal amplification (LAMP) assay with the novel primers that targets highly specific hsdS gene for the detection of S. Thompson. The LAMP assay yielded 100% positive results for S. Thompson strains and observed no cross-reaction with 55 other strains. The sensitivity was determined to be 10 colony-forming units (CFU)/mL in pure and artificially contaminated chicken samples. The LAMP assays were further improved to develop a direct LAMP assay for on-site detection that could complete the entire process within 45 min without the need for DNA isolation. After 60 min of enrichment, artificially contaminated chicken samples (initial concentration of 3 CFU/g) were detectable by direct LAMP assay, and this assay was also effectively used for testing commercial meat samples. The proposed LAMP assay has potential applications for on-site detection of S. Thompson and for rapid tracing of contamination sources in laboratories with limited resources.