"Our group has developed such a system, using an infrared (IR) sensor, that is able to accurately identify low levels of microbial foodborne contaminants."

Infrared sensors for rapid identification of living vs. dead select microbial foodborne contaminants

Investigators: Lisa Mauer (Department of Food Science), Maribeth Cousin (Department of Food Science), Jay Gore, Brad Reuhs (Department of Food Science)

Project Report 2005 - 2006

» Download Project Report 2005 - 2006

Project Rationale

To keep the food supply safe, food production, processing, and retail establishments must be able to identify microbial foodborne pathogens, such as Salmonella, Campylobacter jejuni, and Escherichia coli O157:H7. The CDC estimates that annual foodborne-related outbreaks result in 76 million cases of illness, 325,000 hospitalizations, and 5,000 deaths.

To facilitate timely intervention measures, the food industry needs rapid detection methods. Our group has developed such a system, using an infrared (IR) sensor, that is able to accurately identify low levels of microbial foodborne contaminants. In this phase of the study we have tested the field instrument, and we have applied the technology to a second problem: distinguishing live bacterial cells from dead cells. To accomplish this goal, we developed FT-IR methods and analytical approaches to differentiate between living and dead cells of Salmonella spp. strains and E. coli O157:H7 in water, culture media, and select foods. This is important in both the determination of contamination potential in fresh products and the efficacy of decontamination efforts. We also validated a miniature IR sensor for detecting the live bacteria. In this part of the project we addressed sample handling procedures, the time needed for detection, detection limits, and wavelength bands and algorithms appropriate for the sensor design.

Project Objectives

  • Use an existing library of FT-IR spectra of bacterial cell-wall components and whole cells of E. coli O157:H7 and E. coli K12, as well as Salmonella, for cell identification and differentiation of live versus dead cells in water, cultural media, and foods. This milestone also involves the application and improvement of capture (filtration, etc), concentration, and enrichment techniques.
  • Apply a limited wavelength technique that has already been developed for cell identification in the validation of a field-size IR using the most promising few-wavelength algorithm developed during FT-IR techniques evaluations in the previous project.

Project Highlights

In the studies using variations on the selective and non-selective capture of live versus dead cells of E. coli O157:H7 and E. coli K12, and the subsequent spectral analyses, we showed that live cells could easily be distinguished from dead cells, especially when the cells were killed by the harsh techniques commonly used in the food industry (e.g., heat, salt, UV, etc). In contrast, the use of antibiotics that disrupt metabolism with out physical damage to the cell resulted in less distinct spectral separation of dead cells, but differentiation was still possible. Importantly, a relatively quick multi-step procedure allowed for a quantitative analysis of the relative abundance of dead versus live cells of E. coli O157:H7.

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