1. Department of Microbiology, University of Washington School of Medicine, Seattle, Washington, USA
2. Division of Gastroenterology, Department of Pediatrics, Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada
3. Department of Biostatistics, University of Washington School of Public Health, Seattle, Washington, USA
4. Paul G. Allen School for Global Animal Health, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA