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Listeria Monocytogenes Subtyping Database for Control of Foodborne Listeriosis


The overall goal of the Food Safety Research Consortiun (FSRC) is to conduct and coordinate food safety research and to facilitate the development and use of research knowledge and new approaches and tools to help the food industry in their efforts to improve food safety. Initial research in the FSRC will focus on the dissemination and further development of molecular subtyping and characterization methods for the foodborne pathogens. In a first stage our research and development efforts will focus on the development and use of this database to provide broad access to DNA subtyping and strain information for the foodborne pathogen Listeria monocytogenes. <P>

The specific objectives of this project include: <OL> <LI> To develop a WWW database infrastructure to collect, store, and distribute information on strains of foodborne pathogens and their DNA subtypes. <LI> To develop a WWW database of L. monocytogenes isolates from humans, animals, foods and food processing plant environments and their DNA fingerprints to facilitate a better definition of L. monocytogenes subtypes that can cause human disease when present in foods (and of subtypes that do not cause human disease when present in foods) <LI> To use DNA subtyping and the Listeria WWW database to determine patterns of L monocytogenes contamination and spread in food processing environments to provide the food industry with effective tools for controlling L. monocytogenes contamination.

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NON-TECHNICAL SUMMARY: Molecular subtyping methods for foodborne pathogens provide a unique opportunity to track and define specific bacterial human health hazards. Publicly accessible databases are required to allow the food industry to take advantage of these new techniques. The purpose of this project is to characterize a collection of bacterial isolates and to develop an Internet database structure to allow broad access to DNA subtyping data for foodborne pathogens.

APPROACH: The FSRC program will be administered by faculty and staff in the Department of Food Science at Cornell. They will administer the funds and conduct research as specified and involve faculty at other universities and organizations as formal or informal collaborators. The program will interface with and draw on the existing "Cornell Food and water Safety Program" (, which includes more than 30 faculty members at different colleges with research, teaching, and extension efforts and interests in food and water safety. The FSRC will serve as a central source for information on foodborne pathogen DNA subtypes and associated characteristics. Once the initial database infrastucture has been developed and tested using L. monocytogenes as a model, funding for the FSRC will be used to subcontract with researcehers at Cornell and other universities and laboratories to expand the database to cover other bacterial foodborne pathogens (e.g., E. coli O157:H7, Salmonella). We will use the following specific approaches to accomplish the objectives described above: 1. Design a database structure in Microsoft SQL, which will store all bacterial strain data already collected in our labratory. Develop an Internet interface to allow for searches against our database using DNA subtype patterns (e.g., ribotyping patterns), DNA sequence data, phenotypic data and strain information (source, year of isolation, etc.) as input. 2. Charcterize L. monocytogenes isolates from foods and food processing environments using various DNA subtyping methods. These subtyping data will allow food processing plants to track environmental contamination sources. In conjunction with our database of human l. monocytogenes these data will also aid in defining L. monocytogenes subtypes found in food processing environments and foods, but not associated with human disease. 3. Characterize L. monocytogenes isolates from foods and food processing plants for their pathogenic potential using tissue culture assays to define L. monocytogenes subtypes that differ in their abilities to cause human disease.


PROGRESS: 2001/03 TO 2004/03<br>
Recent estimates project that 76 million cases of gastrointestinal foodborne illnesses occur in the US on an annual basis, resulting in at least 325,000 hospitalizations and 5,000 deaths. To track and control sources of foodborne pathogens, agricultural and food industries have a critical need for access to advanced molecular subtyping tools and data. The Centers for Disease Control and Prevention (CDC) have developed a National Molecular Subtyping Network for Foodborne Disease Surveillance. This database is only available to public health laboratories around the country. To allow the food industry to further take advantage of molecular subtyping methods for controlling and tracking foodborne pathogens, we have developed a WWW-based bacterial subtype database (PathogenTracker 2.0), which is publicly accessible at The PathogenTracker database and strain collection currently contains more than 5,000 L. monocytogenes isolates, including isolates from human and animal listeriosis cases, foods, food processing environments, and other environmental sources. General information on each isolate stored in PathogenTracker includes (if available), year and month of isolation, source (food, food processing environment, human, animal, etc.), state and country, where an isolate was collected, GPS coordinates of sampling site, etc. as well as molecular subtype information. PathogenTracker currently has more than 200 registered users from academia, industry, and government agencies in the US as well as in other countries. The PathogenTracker strain collection also provides an important source for Listeria isolates for research and development purposes. In response to requests we have already supplied at least 250 well characterized L. monocytogenes isolates to more than 10 research groups in academia, government agencies, and industry. Over the current reporting period, we have focused our efforts on depositing large numbers of L. monocytogenes strain data into PathogenTracker and linking them to publications reporting the primary data. These efforts have provided the scientific community with a large set of L. monocytogenes subtype data and associated characteristics. DNA subtype data for more than 3,000 L. monocytogenes isolates from humans, animals, foods and other sources have already been posted in PathogenTracker 2.0. In addition, we have deposited tissue culture virulence assay data for more then 200 L. monocytogenes isolates in this database. Data mining efforts have allowed us to use these data to identify a specific subset of L. monocytogenes that is common among food isolates (representing more than 25% of food isolates), but significantly less common among human clinical isolates (less than 2 percent prevalence). This subset of L. monocytogenes was subsequently shown to be characterized a unique mutation in a key L. monocytogenes virulence gene (inlA) that leads to a reduced ability of these strains to infect human intestinal epithelial cells. We have thus successfully identified a L. monocytogenes subset that clearly show reduced human virulence.
IMPACT: 2001/03 TO 2004/03<br>
The development of an internet-based database will allow rapid exchange and use of sophisticated genetic fingerprinting approaches to better control bacteria causing foodborne diseases. Our initial efforts have focused on the application of this database and fingerprinting methods to better control the bacterium Listeria monocytogenes, which causes approximately 500 human foodborne deaths annually in the US alone. Application of this database will allow for improved source tracking of listeriosis cases and contamination events and for a better understanding of virulence differences among L. monocytogenes subtypes

Wiedmann, Martin
Cornell University
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