Outbreaks of foodborne illness due to pathogenic bacteria have been identified worldwide and have been associated with the consumption of contaminated agricultural products. The main objective of this research is to develop a rapid method for pathogen detection using Raman spectroscopy (RS). Direct detection in culture media and surface-enhanced Raman scattering (SERS) were used to identify Escherichia coli, Escherichia coli O157:H7, Salmonella spp., Listeria monocytogenes, Staphylococcus aureus, Bacillus cereus, and Bacillus thuringiensis. Bacterial isolates were cultured on selective media for 24 h at 37°C or 30°C and then tested with RS. A portable 785 nm point-scan Raman system was developed at ARS USDA for this purpose and multiple laser current and exposure times were tested to establish optimal conditions. Seven nanoparticles and three substrates were evaluated for optimal bacterial detection using label-free SERS. Raman peaks were very weak in direct detection and the bacteria were not identified using direct or SERS approaches. However, two gold nanoparticles consistently showed SERS peaks at 878.9, 1086, and 1455 cm^-1 and relative differences in Raman intensity were observed among each of the tested bacteria. This method can be used to lay a foundation for future research such as SERS combined with chemometric analysis and label-based SERS approaches.

Date Published: 30 April 2019
PDF: 8 pages
Proc. SPIE 11016, Sensing for Agriculture and Food Quality and Safety XI, 110160B (30 April 2019); doi: 10.1117/12.2520624

Published in SPIE Proceedings Vol. 11016:
Sensing for Agriculture and Food Quality and Safety XI
Moon S. Kim; Bryan A. Chin; Byoung-Kwan Cho, Editor(s)