Objective: Our aim is to quantify the prevalence of small intestinal bacterial overgrowth (SIBO) and intestinal methanogen overgrowth (IMO) in PD subjects with constipation compared to patients with unexplained GI symptoms undergoing glucose breath testing (GBT).

Background: Prevalence of SIBO varies widely in PD¹. SIBO in PD has been associated with worse motor function and longer off time². Eradication of SIBO can improve motor fluctuations in PD².

Method: After an overnight fast and a day of low-CHO diet, subjects brushed their teeth and rinsed their mouth with antiseptic mouthwash 2h before test. During GBT, 75 g of glucose dissolved in 250 mL water was administered. Breath samples were obtained at baseline and 15 min intervals for 2 h. Samples are collected in a bag (QuinTron Instrument Company, Inc.) and alveolar gas was analyzed for both H₂ and CH₄ levels by chromatography (QuinTron MicroAnalyzer, QuinTron, Inc). SIBO was defined as H₂ rise of ≥20 ppm from baseline and/or CH4 rise of ≥10 ppm. IMO was defined as any CH₄ ≥10 ppm. . Daily bowel movements were assessed by prospective stool diary. Constipation was defined by <3 complete spontaneous bowel movements (CSBMs)/week. PD stage was assessed by Hahn-Yahr (HY) stage.

Results: In this interim analysis, 19 patients with PD (68.2 ± 7.0 years, F/M=6/13) were enrolled and compared to 158 subjects with unexplained GI symptoms (47.4 ± 15.3 years, F/M=119/39). 31.6% (6/19) of PD subjects had SIBO versus 23.4% (37/158) of subjects with unexplained GI symptoms (p=0.95), shown in Table 1. 52.6% (10/19) of PD subjects had IMO compared to 14.6% (23/158) subjects with unexplained GI symptoms (p<0.001). 36.8% (7/19) had <3 CSBMs per week. There was good correlation between constipation and IMO, but not SIBO, Table 2. The maximum methane level during GBT also correlated with severity of constipation. There was no correlation between SIBO or IMO and the HY stage.

Conclusion: Our study reveals over half of PD subjects with constipation have IMO, which correlates with constipation severity. Methanogens may play a critical role in constipation and PD overall, however, further study is needed. Acknowledgement: Parkinson’s Foundation Translational Research Award.

References: 1. Tan, A. H., Mahadeva, S., Thalha, A. M., Gibson, P. R., Kiew, C. K., Yeat, C. M., … & Yong, H. S. (2014). Small intestinal bacterial overgrowth in Parkinson’s disease. Parkinsonism & related disorders, 20(5), 535. 2. Vizcarra, J. A., Wilson-Perez, H. E., Fasano, A., & Espay, A. J. (2018). Small intestinal bacterial overgrowth in Parkinson’s disease: Tribulations of a trial. Parkinsonism & related disorders, 54, 110-112.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/intestinal-methanogen-overgrowth-imo-more-prevalent-than-sibo-in-parkinsons-disease-with-constipation-preliminary-results/