1. Department of Nutrition and Food Science, Joint Institute for Food Safety and Applied Nutrition, University of Maryland, College Park, Maryland.
2. Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, College Park, Maryland.
3. Department of Microbiology and Immunology, Stanford School of Medicine, Stanford University, Palo Alto, California.
4. Division of Animal and Food Microbiology, Office of Research, Center for Veterinary Medicine, U.S. Food and Drug Administration, Laurel, Maryland.