1. Department of Medicine and Pathology and Laboratory Medicine, Queen Elizabeth II Health Sciences Centre, Dalhousie University, Halifax, Nova Scotia, Canada B3H 1V7
2. Foodborne and Diarrheal Diseases Branch, Division of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, Centers for Diseases Control and Prevention, Atlanta, Georgia 30333
3. Battelle Memorial Institute, Battelle Science and Technology International, Chemical and Environmental Technologies, Atlanta Analytical Chemistry Group, 2971 Flowers Road South, Atlanta, Georgia 30341
4. Morehouse School of Medicine, Atlanta, Georgia 30310