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United States Department of Agriculture

Agricultural Research Service

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Research Project: IMPROVED DETECTION TECHNIQUES FOR FOODBORNE PATHOGENS

Location: Molecular Characterization of Foodborne Pathogens

2010 Annual Report


1a.Objectives (from AD-416)
The long-term objectives of this project are to develop, validate, and implement new technologies and systematic approaches for detection of microbial and chemical contamination of foods. Goals will be accomplished by utilizing multi-disciplinary research teams that involve food scientists, microbiologists, molecular scientists, and agricultural, biological, and electrical engineers.


1b.Approach (from AD-416)
Develop rapid and affordable technologies for detection of harmful levels of biological and chemical food contaminants; to establish better methods of food sample preparation and contaiminant separation procedures that can be used with different detection based technology platforms; to use detection systems, sample preparation and contaminant separations techniques to evaluate the efficacy of novel means of food protection; and to provide education, training, and technology transfer necessary for national implementation of these research programs.


3.Progress Report

The detection and quantification of foodborne pathogens involves the development of a system that can separate microorganisms from the food matrix first, followed by an effective detection/quantification system. Microbial cells are being separated from the food matrix and being concentrated with a series of membrane filters and a hollow fiber system. The filtration device has been used successfully to separate organisms from complex foods (i.e. ready-to-eat meats) and they can be cleaned easily between uses. The filtration system has been improved and can now be used multiple times, thereby reducing both cost and manual operations associated with recovery of concentrated microbial samples. The system is currently being used to concentrate E. coli and Salmonella bacteria, and a 1000-fold concentration of microbial cells is now possible. After the separation and concentration step, a wide variety of detection platforms have been studied. One method uses a microfluidic biochip, that incorporates the polymerase chain reaction (PCR) and dielectrophoresis to concentrate and grow bacteria in the biochips. Label-free detection of PCR reactions is being examined with electrically-based detection to aid in both detection and quantification. A second system called “BARDOT” (Bacterial Rapid Detection using Optical Scattering Technology) uses a light scattering technique to differentiate and classify bacterial colonies grown on Petri-dishes. Much of the work this year has focused on detection and classification of Salmonella and E. coli O157:H7 based on their different light scatter images. Finally, a rapid, simple, and economical method for detection, differentiation, and quantification of Escherichia coli O157:H7 strains in ground beef has been developed using infrared spectroscopy method (FT-IR). A main focus of this work was to establish a method that can effectively distinguish between live and dead cells. Three outbreak strains of E. coli O157:H7and a non-pathogenic control strain of E. coli were evaluated in ground beef samples. The detection limit was 10,000 cells. Detection of live cells in the presence of dead cells extracted from ground beef was possible with as few as 0.5% live cells in the presence of 99.5% dead cells of E. coli O157:H7. Similar results were obtained for the detection of Salmonella enterica serovars from chicken. Communication with collaborators was through emails and conference calls.


Last Modified: 4/23/2014
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