"We developed a FTIR and raman library of spectroscopic fingerprints for a total of 28 foodborne pathogenic strains."

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

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

Project Report 2007 - 2008

» Download Project Report 2007 - 2008

Project Rationale

Zoonotic pathogens such as Salmonella spp., Listeria monocytogenes, Shiga-toxin producing Escherichia coli (including E. coli O157:H7), and Campylobacter jejuni are recognized as causes of significant and sometimes lethal foodborne illnesses. Identification of these microbial contaminants 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 1 to 10 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 help ensure a safe food supply for consumers.

The ultimate goal of this research was to develop a portable miniaturized infrared sensor for specific and sensitive detection of foodborne pathogens. We proposed to integrate sampling and biosensor modules with Fourier transform infrared/Raman spectroscopy (FTIR/raman) as well as uv-Visible near infrared spectroscopy to improve detection sensitivity and specificity. The first steps were to constitute the standardization of FTIR and raman methodologies with the most appropriate sampling steps for sensitivity enhancement and biofunctionalization steps for specificity improvement. The second phase focused on extensive validation using food, as well as mock industry samples, and translating the benchtop methodologies to a portable mid-infrared device.

Project Objectives

  • Develop and standardize 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 developed a FTIR and raman library of spectroscopic fingerprints for a total of 28 foodborne pathogenic strains. Of these, 14 were E. coli O157:H7, and two were outbreak strains. We developed a biosensor protocol using gold nanorods to detect < 10 CFU/ml using a simple ultraviolet-visible spectrometer. We finalized a procedure to perform component analysis to understand further the basis and the origin of the FTIR signatures. We constructed and tested the PathoIR chip in the benchtop FTIR. The presence of three signature peaks in the 850cm-1 to 1100 cm-1 region confirmed binding of the target bacteria to the chip surface. We identified a portable system which is twice as sensitive as the current system. This system is already remarkably promising. However, we believe that this can be further improved.

In summary, our key accomplishment this year was the development of sensitive nanobiosensors that can provide a detection limit of ~10 CFU/ml using a simple visible-near-infrared spectrometer. The potential exists to further refine this technology by integrating a pathogen separation element. Hence, detection in complex mixtures could be performed in one step. This would also facilitate the detection of multiple pathogens at a very high sensitivity level using a simple spectrometer that is affordable and portable.