Improved Detection Techniques for Foodborne Pathogens: FT-IR Applications

Investigator: Lisa Mauer (Department of Food Science)

Project Report 2008 - 2009

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Project Rationale

Viability assessment of bacteria is important in a wide variety of applications in the food industry, including evaluation of the effectiveness of inactivation treatments and microbial quality assessment of foods. The suitability of pathogen detection methods for food analysis depends on sensitivity, total time to detection, and cost of consumables. Even though the detection limit for conventional plating methods is low, the detection procedures are labor-intensive, often requiring extensive sample preparation and long incubation times. Conventional detection methods take at least 24 to 48 hours to differentiate and identify microorganisms; therefore, measures taken to counteract food contamination must wait at least that long. Additionally, conventional methods do not provide information about dead bacteria and may underestimate sub-lethally damaged cells present in a food sample.

Project Objectives

  • Improve Fourier-transform infrared spectroscopy (FTIR) detection techniques for pathogen detection.
  • Identify detection limits for methods developed and opportunities for improving sensitivity and specificity of FTIR detection techniques.
  • Determine how spectroscopic differentiation relates to known cell surface characteristics from laboratory and foodborne outbreak pathogens.

Project Highlights

FTIR pathogen detection techniques were improved this year by determining how spectroscopic differentiation relates to cell surface characteristics, how these structures vary with conditions and treatments, and how the techniques could be applied to detect pathogens in food systems (fruit juice, ground beef, and chicken breast). In studies using Escherichia coli O157:H7, the influence of different types of inactivation treatments (sterilization at 121 °C, UV light, alcohol, sodium chloride, chloramphenicol, and trimethoprim-sulfamethoxazole) on spectra was determined. The FTIR technique can be used to discriminate bacteria subjected to different inactivation treatments and possibly to assess the degree of cell injury caused by each treatment. FTIR methods were able to differentiate live and dead cells of E. coli O157:H7 as well as quantify live cells of E. coli O157:H7 in the presence of dead cells (R2 > 0.996).

Coupling separation techniques (filtration and Dynabeads®) with FTIR analyses enabled the detection and quantification of E. coli O157:H7 from ground beef. The filtration-FTIR and Dynabeads®-FTIR approaches are relatively faster and less expensive than many other techniques used for this purpose. The filtration-FTIR techniques have the additional potential advantages of discriminating between live and heat-treated (dead) E. coli O157:H7 cells, differentiating between pathogenic and non-pathogenic E. coli strains, and quantifying live cells in the presence of dead cells.

"The filtration-FTIR techniques have the additional potential advantages of discriminating between live and heat-treated E. coli O157:H7 cells..."

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