"the BARDOT system... provided a platform for using a simple laser beam toscatter the bacterial colonies growing on an agar plate and simultaneouslycapturing and storing the images..."

Improved Detection Techniques for Foodborne Pathogens: Bacterial Rapid Detection using Optical Scattering Technology (BARDOT)

Investigator: Arun K. Bhunia (Department of Food Science)

Project Report 2005 - 2006

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Project Rationale

Listeria monocytogenes and Escherichia coli are the major foodborne pathogens of concern in the United States. For the detection and evaluation of foods contaminated with Listeria monocytogenes or E. coli, USDA/FSIS recommends initial enrichment and subsequent plating on a selective agar media, which is often followed by further identification procedures. These procedures are often time consuming and lengthy, taking more than 2-3 days. The present industrial demand is to increase the rapidity of the detection assays leading to strategies for decreasing bacterial contamination and thus reducing the economical loss. Our main objective was to reduce the time of identification of these pathogens after plating, by developing a simple light scattering sensory method. The method has now been improved to differentiate among the different strains of Listeria, based on the varying patterns.

There have been increasing foodborne illnesses, multiple outbreaks, product recalls, and loss of lives, resulting from pathogens in processed, ready-to-eat food products. Bacterial contamination in products not only puts the public at risk, it is costly to companies due to loss of production time, product recalls and liability.

Project Objectives

  • To improve the BARDOT (Bacteria Rapid Detection using Optical Scattering Technology) design, including supporting physics-based models, for more repeatability and maximum discrimination of forward scattering signatures of colonies.
  • To acquire scatter images of colonies of select foodborne bacterial colonies including pathogens.
  • To analyze the bacterial colonies of different foodborne bacteria on non-selective and selective agar media.
  • To validate the technology by using naturally or deliberately contaminated food samples.
  • To analyze cellular composition, cell arrangement, refractive index and colony contents using electron microscopy, FT-IR or GC-MS.
  • To analyze the scatter signal images using 'Standard feature extraction' and 'Moments of shape analysis' methods.

Project Highlights

The design and development of the BARDOT system was the major accomplishment during the year 2005-2006. This was a significant accomplishment since it provided a platform for using a simple laser beam to scatter the bacterial colonies growing on an agar plate and simultaneously capturing and storing the images using a CCD camera attached to the instrument. The computer-stored images were used for image analysis. This system was able to differentiate genus Listeria, Salmonella and Vibrio with 89-98% accuracy. Furthermore, species within genus Listeria can be differentiated with 92-94% accuracy, Salmonella with 95-98% accuracy, and Vibrio with 84-90% accuracy.