Establishment and validation of a loop-mediated isothermal amplification (LAMP) assay targeting the ttrRSBCA locus for rapid detection of Salmonella spp. in food

Salmonella infection represents a common foodborne zoonosis of public concern worldwide. Rapid and user-friendly nucleic acid-based detection methods like loop-mediated isothermal amplification (LAMP) can contribute to the improvement of food safety and prevention of foodborne illness. In the present study, a LAMP assay was established and validated as a specific and rapid tool for detecting Salmonella spp. in various food matrices. Primers targeted a region within the ttrRSBCA locus and enabled 100% inclusivity of the 88 tested Salmonella strains, while no false positive signal occurred in any of the 92 tested non-Salmonella strains. After 20-h enrichment of artificially contaminated minced meat and ready-to-eat salad, initial contamination levels of 1 CFU/25 g were detectable via LAMP. The establishment of a simplified DNA-isolation method, which was adapted for field applications, enabled similar detection probability after 20-h enrichment of artificially contaminated food samples. During validation, 82 variously processed food samples underwent comparative analysis by LAMP and the standard culture method. The LAMP assay was further validated by the investigation of reference material of unknown Salmonella contamination status. Results showed that the ttrRSBCA-based LAMP detection of Salmonella spp. is a suitable tool for rapid sample screening within 24 h including first enrichment. Additionally, all Salmonella isolates obtained during cultural examination of naturally contaminated samples were correctly identified by LAMP, thus making it a suitable confirmation method for official applications.