1. Environmental Microbial & Food Safety Laboratory, United States Department of Agriculture–Agricultural Research Service (USDA-ARS), Beltsville Agricultural Research Center (BARC), Beltsville, Maryland.
2. Electron & Confocal Microscopy Unit, United States Department of Agriculture–Agricultural Research Service (USDA-ARS), Beltsville Agricultural Research Center (BARC), Beltsville, Maryland.
3. Department of Molecular Genetics and Microbiology, Emerging Pathogens Institute, University of Florida, Gainesville, Florida.
4. Food Safety and Enteric Pathogens Research Unit, USDA-ARS-NADC, Ames, Iowa.