Improved Detection Techniques for Foodborne Pathogens: Separation Techniques

Investigator: Michael Ladisch (Department of Agricultural and Biological Engineering)

Project Report 2008 - 2009

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Project Rationale

The long-term objectives of this project are to develop, validate, and implement new technologies and systematic approaches for detecting microbial and chemical contamination of foods. The approach focuses on four main components including separation, detection, identification, and quantification of target microorganisms from food matrices. The rapid and accurate detection of foodborne pathogens in meats, dairy products, and vegetables is a critical component for achieving food safety, preventing deaths and severe illnesses caused by foods, and minimizing economic losses to the food industry. Recalls of food products may be minimized by catching any problems before the products leave the plant. Rapid detection is a powerful tool in achieving such a goal.

Our research addresses cell separation and concentration technologies to facilitate pathogen detection and the development, validation, and implementation of robust new identification and quantification technologies. Multiple detection technologies coupled with target separation from food matrices provide the necessary breadth of orthogonal methods that ensure detection of a diverse set of pathogens, and provide platforms that facilitate both detection and identification of pathogens. Our overall goal is to develop robust operational technologies for the food safety industry, regulatory inspection, and food safety research.

Project Objectives

  • Characterize the pore structure of hollow fiber membranes with respect to the potential to entrap microorganisms and particles in the one to two micron range against a background of small particulates derived from food materials.
  • Identify the particle size of microbial adsorbents. Demonstrate the adsorption of microorganisms from food matrices, and the separation of particles from homogenized food matrices.
  • Inoculate GFP-expressing microorganisms into food, recover the microorganisms, and image them using fluorescent microscopy and SEM.
  • Achieve a multiplexed DEP/Ab mediated capture of Escherichia coli and Listeria monocytogenes in the same microfluidic biochip.

Project Highlights

We found that the distribution of cells between solid food particles and a surrounding liquid (aqueous buffer) concentrates cells on the surface of food particles. We hypothesize that this effect is a function of pH and ionic strength, since this would impact the surface charge (zeta potential) of cells, as well as the charge of the proteins on the surface of the particles. Like charges would release cells, while unlike charges would attract them (causing adsorption). We are systematically examining the effects of buffer properties (ionic strength, pH, and ionic species) to obtain devices that are capable of releasing cells from food particles and then utilizing them for subsequent interrogation using PCR, fluorescent labeling, fourier-transform infrared spectroscopy, and other methods.

"Multiple detection technologies coupled with target separation from food matrices provide the necessary breadth of orthogonal methods that ensure detection of a diverse set of pathogens..."

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