1. Microbial Food Safety Research Unit, Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, 600 East Mermaid Lane, Wyndmoor, Pennsylvania 19038
2. National Animal Disease Center, Agricultural Research Service, U.S. Department of Agriculture, 2300 Dayton Road, Ames, Iowa
3. Centers for Epidemiology and Animal Health, Animal and Plant Health Inspection Service, U.S. Department of Agriculture, 555 South Howes Street, Fort Collins, Colorado 80521