1. Division of Neurology, Department of Medicine, and the Mah Pooi Soo and Tan Chin Nam Centre for Parkinson's and Related Disorders, Faculty of Medicine University of Malaya Kuala Lumpur Malaysia
2. Division of Gastroenterology, Department of Medicine, Faculty of Medicine University of Malaya Kuala Lumpur Malaysia
3. Department of Medical Microbiology University of Malaya Kuala Lumpur Malaysia
4. Division of Neurology, Edmond J. Safra Program in Parkinson's Disease and the Morton and Gloria Shulman Movement Disorders Clinic, Toronto Western Hospital University of Toronto Toronto Ontario Canada