Background: Parkinson’s disease (PD) is one of the most common neurodegenerative diseases. There is accumulating evidence that link gut microbiota to symptomatology and pathophysiology of PD. The aim of this study was to
describe the pattern of gut microbiota and its association with PD and identify the effect of environmental factors on
gut microbiota. This case–control study included 46 patients diagnosed as Parkinson’s disease (PD) and 31 healthy
volunteers age and sex matched. Detailed history including age of onset, duration of disease, environmental risk factors, diet data, treatment, Unified Parkinson’s Disease Rating Scale (UPDRS), and gastrointestinal tract (GIT) domain of
Non‐Motor Symptoms Scale (NMSS) were assessed. After extraction of bacterial DNA from the fecal samples, bacterial
abundance was quantified by qPCR using 16S rRNA group-specific primers.
Results: Significant high abundance of Clostridium cluster IV, Akkermansia, Bifidobacterium, and lactic acid bacteria
were found in the PD group compared with the control group (P < 0.001, 0.04, 0.02 and < 0.001, respectively), while
Firmicutes were significantly less abundant in the PD group (P < 0.001) compared with the control group. The naive
PD patients had significant abundance of Bifidobacterium, and lactic acid compared with control group. Interestingly,
Akkermansia was more abundant in treated than untreated patients. There were significant associations between
pesticide exposure and Bifidobacterium (P=0.002), while no significant correlations between different gut microbiota
and demographic, environment data, different rating scores or dominant type of PD. There was a significant negative
correlation between the Bifidobacterium with the duration of illness (P=0.012).
Conclusion: The present study highlighted a significant connection between PD and levels of certain types of gut
microbiota, in support of a possible link between gut microbiota and a neurodegenerative cascade of PD.