Subtractive Inhibition Assay Based on PagN-Specific Monoclonal Antibody for the Detection of Salmonella Using Surface Plasmon Resonance

Salmonella is a common foodborne zoonotic pathogen that poses a great threat to human health and breeding industry. The rapid detection of Salmonella is necessary for early prevention and control. In this study, a subtractive inhibition assay (SIA) based on surface plasmon resonance (SPR) for the rapid detection of Salmonella was developed. Mouse-specific monoclonal antibody 3B3 against Salmonella membrane protein PagN was first incubated with Salmonella. The unbound free antibody was separated using a sequential process of centrifugation and then detected using an immobilized goat anti-mouse immunoglobulin G polyclonal antibody on the SPR sensor chip. This SIA-SPR method showed excellent sensitivity for Salmonella with a limit of detection of about 300 CFU mL⁻¹. This method is sensitive to different serotypes of Salmonella strains but not for non-Salmonella strains. It was able to detect Salmonella in the contaminated water and milk powder at less than 10² and 10³ CFU mL⁻¹, respectively, which was consistent with the bacterial plate count results. In addition, this method could be used to evaluate the lysis effect of phages on bacteria. Since the culturing detection method needs more than 48 h, this method has the potential for the rapid and sensitive clinical detection of Salmonella. For our knowledge, this is the first report for Salmonella detection using SIA-SPR method.