Directly interface microreaction tube and test strip for the detection of Salmonella in food with combined isothermal amplification and lateral flow assay

Abstract

Salmonella is a common foodborne bacterial pathogen that leads to severe illness or even death. The recommended method for Salmonella detection relies on the culture and has a long turnaround time of up to ∼1 week. In this study, we have developed a molecular assay that detects Salmonella in food by targeting the invA gene using loop-mediated isothermal amplification (LAMP) and lateral flow assay (LFA). The assay shortens the turnaround time considerably to ∼1 day, including pre-enrichment and DNA extraction. More importantly, we have developed a simple device that directly couples the LAMP microreaction tube to the LFA test strip, eliminating the need for manual liquid handling. The unique design greatly simplifies the device operation, rendering the device suitable for point-of-sampling applications. The method could be used as an initial screening tool, but would require confirmation testing to act on the result. Using the proposed device, we have successfully detected samples containing as little as 10 fg (3-4 copies) Salmonella genomic DNA. The detection limit of the device in terms of bacteria load is 4 colony forming units (CFUs). We have also correctly identified Salmonella at as little as 4-6 CFU bacteria per 25 g of food homogenate.