Development of a rapid, one-step-visual method to detect Salmonella based on IC-LAMP method

Background: Salmonella can cause serious human gastroenteritis and is frequently isolated from various food samples. The cell culturing, immunoassay, and polymerase chain reactions (PCR) are the current methods to detect such pathogenic agents. However, these methods are timeconsuming and laborintensive, and thus unavailable for rapidmonitoring of Salmonella. Aims: This study aimed to develop an immunocaptureloopmediated isothermal amplification (IC-LAMP) for rapid and sensitive detection of Salmonella. Methods: Salmonella was used as antigen to produce monoclonal antibody (mAb) and mAbs were prepared via subcloning three times. The mAb 1B12 with high affinity was coated on the surface of the immunomagnetic beads (IMBs) to capture Salmonella. The enriched products (IMBs-Salmonella) were used for LAMP using the special primers targeted the conserved invA gene of Salmonella. Results: The IC-LAMP was developed based on mAb 1B12 and LAMP. Targeting the conserved invA gene of Salmonella, the detection time was shortened to 50 min from three days. If the reaction contains Salmonella, the green fluorescence and the trapezoidal strip can be clearly observed. Importantly, the method combines the specificity of antibody and LAMP with a detection limit of 5 CFU/ml in artificially contaminated water and milk. The specificity of this method was demonstrated by testing other similar bacteria. The results indicate that the IC-LAMP reacts only with Salmonella and does not crossreact with other similar bacteria. Conclusion: The IC-LAMP assay developed here is a rapid, sensitive, onestepvisual method to screen for the presence of Salmonella in food samples. This method is faster than traditional PCR, LAMP, and other methods, and can be used as a primary screening method for the detection.