Label-free screening of foodborne Salmonella using surface plasmon resonance imaging

Area of Science:

• Food Safety
• Biosensing Technology
• Microbiology

Background:

• Foodborne infections pose a significant public health risk, often caused by a limited number of major pathogens.
• Rapid, cost-effective, and multiplex screening methods are crucial for enhancing food safety and public health surveillance.
• Surface Plasmon Resonance Imaging (SPRi) offers a label-free, multiplex platform with potential for sensitive pathogen detection.

Purpose of the Study:

• To develop and evaluate a singleplex immunoassay using SPRi for the detection of Salmonella.
• To optimize SPRi assay parameters for improved sensitivity, specificity, and speed in pathogen screening.
• To assess the feasibility of using SPRi for direct Salmonella detection in food matrices.

Main Methods:

• Development of a Salmonella-specific immunoassay on an SPRi sensor chip in a microarray format.
• Optimization of ligand immobilization (pH, concentration) and implementation of a pause flow protocol.
• Evaluation of assay specificity against non-Salmonella species and detection of Salmonella serotypes in various matrices.

Main Results:

• The SPRi immunoassay demonstrated high specificity against six non-Salmonella species.
• The assay successfully detected five of six Salmonella serotypes, including common outbreak-associated strains.
• Detection limits were as low as 2.1 × 10⁶ CFU/mL in PBS and 7.6 × 10⁶ CFU/mL in a chicken rinse matrix.
• Direct detection of Salmonella (6.8 CFU/mL after enrichment) in spiked chicken carcass rinse samples was achieved.

Conclusions:

• SPRi is a viable label-free technology for sensitive and specific Salmonella detection.
• The developed immunoassay shows potential for streamlined foodborne pathogen screening with minimal sample preparation.
• This SPRi-based approach could significantly benefit public health by enabling faster and more cost-effective food safety monitoring.