1. *Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO
2. †Department of Molecular Microbiology and Immunology, School of Medicine, University of Missouri, Columbia, MO
3. ‡Food Safety and Enteric Pathogens Research Unit, National Animal Disease Center, Agricultural Research Service, United States Department of Agriculture, Ames, IA
4. §Division of Animal Sciences, University of Missouri, Columbia, MO