Magnetic Bead-Based Immunoassay Coupled with Tyramide Signal Amplification for Detection of S almonella in Foods

Salmonella is the leading cause of bacteria-associated foodborne illnesses in the United States. Early detection of this pathogen by a rapid and sensitive assay is important to prevent salmonellosis. In this study, we describe a magnetic bead-based immunoassay for detection of Salmonella consisting of immunomagnetic separation for simple target concentration with tyramide signal amplification to increase the assay sensitivity. The developed immunoassay was able to detect Salmonella Typhimurium in culture with the detection limit of 280 CFU/mL in less than 3 h without any enrichment and further decreased to 70 CFU/mL with 3 h enrichment. When tested with ground beef and poultry samples artificially contaminated with S. Typhimurium and Enteritidis, the assay showed increased detection limits with 800 and 200 CFU/mL, respectively, due to the effect of complex food matrices. However, when 12 h enrichment was added, the detection limits in both food matrices decreased to 1 CFU. Practical Applications This study demonstrated that using immunomagnetic separation (IMS) and tyramide signal amplification can enhance sensitivity and specificity for the detection of Salmonella in food samples. The developed assay has great potential as a simple monitoring system for foodborne pathogens in food samples, which can improve food safety and public health. The results were also compared with sandwich type enzyme-linked immunosorbent assay, which showed the developed assay is approximately 50 times more sensitive than enzyme-linked immunosorbent assay.