Longitudinal Characterisation of the Gastrointestinal Tract Microbiome in Systemic Sclerosis.

Objectives: To evaluate changes in microbial composition and the evolution of gastrointestinal tract (GIT) symptoms in systemic sclerosis (SSc). Methods: Adult SSc patients provided stool specimens every 3 months over the course of 1 year. Participants completed the University of California, Los Angeles (UCLA) GIT 2.0 questionnaire to assess GIT symptom severity at each stool collection. The microbiota from these samples were determined by Illumina HiSeq 2500 16S ribosomal RNA sequencing (Illumina, Inc., San Diego, California, USA). Mixed effect models evaluated changes in GIT symptoms and microbial composition over time. Results: Among 19 patients with SSc (female; 89.5%; median age: 51.3 years), the median disease duration was 7 years and the baseline total GIT 2.0 score was 0.7 (standard deviation: 0.6). The majority of participants (63%) provided at least four stool samples over the course of the 12-month study. Patients with longer disease durations had increased GIT symptoms over the course of the study. There was no difference in the course of GIT symptoms over time between patients with limited versus diffuse cutaneous disease. The relative abundances of specific genera did not change over time within individual subjects. After controlling for age, sex, ethnicity, disease duration, and SSc subtype (i.e., limited versus diffuse), low abundance of Conclusion: This study is the first to have longitudinally characterised the lower GIT microbiome in SSc patients and demonstrated relative stability of genera abundance over the course of 1 year. The findings provide additional evidence that specific genera are associated with SSc-GIT symptoms and warrant further evaluation in larger SSc studies.