"New technologies for detecting foodborne pathogens that are rapid, sensitive, and portable with a potential for on-site detection are needed to ensure a safe food supply for consumers."

Detection of foodborne pathogens via an integrated spectroscopy and biosensor-based approach

Investigator: Joseph Irudayaraj (Department of Agricultural and Biological Engineering)

Project Report 2008 - 2009

» Download Project Report 2008 - 2009

Project Rationale

Identification of microbial contaminants, such as pathogenic Salmonella, Campylobacter, Listeria monocytogenes, and Escherichia coli O157:H7, is a primary food safety concern in food production, processing, and retail environments. Current detection methods for E. coli O157:H7 require enrichment for 18 to 24 hours followed by isolation, prescreening, and confirmation with classical biochemical methods or commercially available assays based on ELISA, antibody precipitation, or PCR. These procedures require up to four days to completely identify E. coli O157:H7. The infective dose for Salmonella strains varies with the server, food, and person. As few as one to ten cells can cause illness, and ranges from 1 to 107 CFU/ml of Salmonella strains have been reported.

New technologies for detecting foodborne pathogens that are rapid, sensitive, and portable with a potential for on-site detection are needed to ensure a safe food supply for consumers.

Project Objectives

  • Develop and standardize fourier-transform infrared spectroscopy (FTIR) and raman spectroscopy-based molecular fingerprints (spectra) of foodborne outbreak strains in conjunction with sampling and regulatory validation in food matrices.
  • Advance infrared equipment, sampling, testing, and validation capabilities for rapid identification of foodborne pathogens.

Project Highlights

We completed a spectral library of raman and FTIR fingerprints for E. coli, Salmonella, Listeria, Shigella, and Staphylococcus; Raman fingerprints were found to be sharper than the FTIR fingerprints. We classified key pathogens using chemometrics, and we classified outbreak strains.

Next, we developed a magnetic particle-based assay to separate a pathogen of choice, and the separated molecules were fingerprinted and detected by the portable spectrometer. This achievement represents the first portable IR-biosensor. We achieved highly selective detection in fewer than 30 minutes at both species (E. coli O157:H7 vs. S. typhimurium) and strain (E. coli O157:H7 vs. E. coli K12) levels in complex food matrixes (two percent milk, spinach extract) with a detection limit of 104-105 CFU/ml. The combined approach of functionalized magnetic nanoparticles and IR spectroscopy imparts specificity through spectroscopic fingerprinting and selectivity through species-specific antibodies with a built-in sample extraction step. This approach could be applied in the field for on-site foodborne pathogen monitoring.