It has been hypothesized, based on epidemiological observations, that Helicobacter pylori (HP) infection may play a role in the pathogenesis of Parkinson's Disease (PD). Previous studies have also shown that HP eradication therapy may result in improvements in levodopa pharmacokinetics and motor fluctuations. This study aims to examine the effects of HP eradication, using a double-blind randomized placebo-controlled trial design in a relatively large cohort of patients. Outcomes of interest include motor function, gastrointestinal symptoms and health-related quality of life. The investigators hypothesize that HP eradication will lead to improvements in motor function. The primary outcome of interest is the "ON"-medication Unified PD Rating Scale (UPDRS) Part III score at 3 months. Secondary outcomes include Purdue Pegboard Score, Timed Test of Gait, Dyskinesia and Bradykinesia scores measured by Parkinson's Kinetigraph (PKG), Leeds Dyspepsia Questionnaire (LDQ), Parkinson's Disease Questionnaire (PDQ-39), UPDRS Part I, Part II and Part IV; and Montreal Cognitive Assessment (MOCA).

Inclusion Criteria:

1. Aged ≥18 years
2. Provision of written informed consent
3. Clinical diagnosis of Parkinson's Disease (PD) assigned by a consultant neurologist

Exclusion Criteria:

1. History of previous gastric or major abdominal/pelvic surgery
2. History of previous eradication therapy for Helicobacter pylori
3. Antibiotic use in the preceding four weeks or use of anti-acid/prokinetics/laxatives in the preceding one week prior to breath test
4. Recent initiation of dopaminergic medications (within the last three months) or recent adjustment of dopaminergic medications (within the last one month)
5. History of functional neurosurgery for PD
6. No concomitant neurologic disease except PD
7. Medical condition that prevents reliable completion of questionnaire