1. Department of Veterinary Microbiology and Preventive Medicine, Iowa State University, Ames, Iowa.
2. Department of Veterinary and Biomedical Sciences, University of Minnesota, St. Paul, Minnesota.
3. Department of Veterinary and Microbiological Sciences, North Dakota State University, Fargo, North Dakota.
4. Department of Veterinary and Biomedical Sciences, Pennsylvania State University, University Park, Pennsylvania.
5. Information Technology Services, North Dakota State University, Fargo, North Dakota.
6. E. coli Reference Center, Pennsylvania State University, University Park, Pennsylvania.
7. U.S. Food and Drug Administration, Center for Veterinary Medicine, Office of Research, Laurel, Maryland.