Simultaneous Detection and Serotyping of Salmonellae by Immunomagnetic Separation and Label-Free Surface-Enhanced Raman Spectroscopy

Current detection and characterization techniques for Salmonellae are time consuming, and rapid methods could benefit investigation and control of foodborne outbreaks. In this study, the potential of surface-enhanced Raman spectroscopy (SERS) in label-free detection and serotyping of Salmonella was evaluated. After immunomagnetic separation (IMS) and overnight culture, SERS spectra were collected from multiple replicates and experiments and analyzed by chemometrics. The detection/characterization accuracies were evaluated in real unknown mixture samples, which were confirmed by plating on selective agar plates and anti-sera agglutination tests. Prediction accuracies were found between 93 and 100%, 87 and 100%, and 67 and 100% for detecting Salmonella from other species, characterization of Salmonella serotypes, and simultaneous detection and characterization, respectively. When validated in mixture samples consisting of six bacteria, accuracies were 65-100% with increased misclassification. Overall, the approach may provide an inexpensive alternative within similar or slightly longer periods of time, but further improvement in spectral reproducibility and accuracy is needed.