Biostructure of fecal microbiota in healthy subjects and patients with chronic idiopathic diarrhea.

BACKGROUND & AIMS: Dysbiosis is a key component of intestinal disorders. Our aim was to quantitatively access the biostructure of fecal microbiota in healthy subjects and patients with chronic idiopathic diarrhea and evaluate the responses to Saccharomyces boulardii treatment.
METHODS: We investigated punched fecal cylinders from 20 patients with chronic idiopathic diarrhea and 20 healthy controls using fluorescence in situ hybridization. Fluctuations in assembly of 11 bacterial groups were monitored weekly for 3 weeks before, during, and after oral S boulardii supplementation.
RESULTS: The structural organization of fecal microbiota in healthy subjects was stable and unaffected by S boulardii. The assembly of fecal microbiota in idiopathic diarrhea was markedly different, characterized by mucus depositions within feces; mucus septa and striae; marked reduction in concentrations of habitual Eubacterium rectale, Bacteroides, and Faecalibacterium prausnitzii groups; suppression of bacterial fluorescence in the center of the feces; increased concentrations and spatial shift of mucotrop bacteria to the fecal core; and increased concentrations of occasional bacteria. Except for elevated concentrations of some occasional bacterial groups, all parameters typical for diarrhea improved significantly with S boulardii treatment and most changes persisted after cessation of therapy. The improvement of the fecal microbiota was accompanied by partial (40%) and complete normalization (30%) of the diarrheal symptoms.
CONCLUSIONS: The fecal microbiota is highly structured. Fluorescence in situ hybridization analysis allowed us to quantitatively study the dysbiotic changes. S boulardii significantly improved the fecal biostructure in patients with diarrhea but had no influence on the feces in healthy subjects.