Functional biostructure of colonic microbiota (central fermenting area, germinal stock area and separating mucus layer) in healthy subjects and patients with diarrhea treated with Saccharomyces boulardii

The colonic content can be compared to a spatially structured high output bioreactor composed of three functionally different regions: a separating mucus layer, a germinal stock area, and a central fermenting area. The stool mirrors this structure and can be used for diagnosis in health and disease. In a first part, we introduce a novel method based on fluorescence in situ hybridization ( FISH) of sections of punched-out stool cylinders, which allows quantitatively monitor microbiota in the mucus, the germinal stock and the central fermenting areas. In a second part, we demonstrate the practical implementation of this method, describing the biostructure of stool microbiota in healthy subjects and patients with chronic idiopathic diarrhea treated with Saccharomyces boulardii. Punched stool cylinders from 20 patients with chronic idiopathic diarrhea and 20 healthy controls were investigated using fluorescence in situ hybridization. Seventy-three bacterial groups were evaluated. Fluctuations in assembly of 11 constitutive bacterial groups were monitored weekly for 3 weeks prior to, 3 weeks during, and 3 weeks after oral Saccharomyces boulardii supplementation. Typical findings in healthy subjects were a 5-60 mu m mucus separating layer; homogeneous distribution and fluorescence, high concentrations (> 10 x 10(10) bacterial/mL) of the three habitual bacterial groups: Bacteroides, Roseburia and Faecalibacterium prausnitzii; and low concentrations of the occasional bacterial groups. The diarrhea could be described in terms of increased separating effort, purging, decontamination, bacterial substitution. Typical findings in diarrhea were: increased thickness of the protective mucus layer, its incorporation in the stool, absolute reduction in concentrations of the habitual bacterial groups, suppression of bacterial metabolism in the central fermenting area ( hybridization silence), stratification of the stool structure by watery ingredients, and substitutive increase in the concentrations of occasional bacterial groups. The microbial and clinical symptoms of diarrhea were reversible with Saccharomyces boulardii therapy. The structure-functional analysis of stool microbiota allows to quantitatively monitor colonic malfunction and its response to therapy. Saccharomyces boulardii significantly improves the stool biostructure in patients with chronic idiopathic diarrhea and has no influence on the stool microbiota in healthy subjects.