Background: The gut microbiome is speculated to play a crucial role in its pathogenesis of Parkinson's disease as a triggering factor. Recent hypotheses suggested that Prevotella species regulate gut permeability, exert a neuroprotective effect, and interestingly, has been suspected to be deficient in PD patients, and so may play a role in this disease. Aim: This study was designed to compare between PD patients and their healthy controls as regards relative Prevotella abundance, prevalence of Prevotella-dominant Enterotype, and constipation severity. Also, to correlate Prevotella changes with the clinical phenotypes and  severity of motor and non-motor symptoms of PD. Methods: Twenty-five PD cases were enrolled in this study and cross-matched to 25 healthy subjects representing the control group. Overall NMS severity was assessed using the Non-Motor Symptoms Scale (NMSS). Quantitative SYBR green Real Time PCR was performed for the identification and quantitation of Prevotella in stool. Results: Prevotella relative abundance was 4-fold decreased in cases when compared to controls with PIGD phenotype showing the lowest abundance, however the difference was not statistically significance. Prevotella-dominant Enterotype was less presented in cases compared to controls, the result was statistically significant. Severe and very severe constipation grades presented 64% of cases group Vs 12% of control group. There was statistically significant positive correlation between total constipation score and UPDRS total score and motor symptoms phenotypes. Conclusion: Relative low Prevotella abundance in PD patients appears to be related to severe phenotypes of the disease; PIGD and mixed phenotypes. Severe constipation was more presented in PD cases which may be considered  as a preclinical biomarker for PD.