1. Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, USA
2. Department of Population Health and Pathobiology, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, USA
3. Wake County Animal Center, Raleigh, North Carolina, USA
4. E. coli Reference Center, Pennsylvania State University, University Park, Pennsylvania, USA