The Effect of the Prebiotic Inulin and the Probiotic<i>Bifidobacterium longum</i>on the Fecal Microflora of Healthy Volunteers Measured by FISH and DGGE

Abstract

The effect of pre- and probiotics on the human intestinal microflora was investigated by fluorescent in situ hybridization (FISH) with specific 16S rRNA-targeted oligonucleotide probes, and by denaturing gradient gel electrophoresis (DGGE) of specifically PCR-amplified 16S rRNA genes. The prebiotic inulin was orally administered in the form of Raftiline ® HP (Orafti, Belgium). Daily doses of 9 g were taken for 14 days by 10 healthy adult volunteers. The probiotic Bifidobacterium longum , encapsulated in gelatin/pectin capsules, was orally administered in the form of Bifina ® (Morishita Jintan, Japan). Nine capsules were taken each day for 14 days by 14 healthy adult volunteers. For the prebiotic study, FISH probes were used to enumerate all bacteria, bifidobacteria, the Eubacterium rectale–Clostridium coccoides group (Erec group), Bacteroides , and eubacteria of the low G+C group. No significant changes were found in the total population of bacteria, the Bacteroides nor in the low G+C group during the study. The population of bifidobacteria increased significantly, while there was a significant decrease in numbers of the Erec group. The FISH analysis of the probiotic study focused on the enumeration of bifidobacteria only, which did not increase significantly during the study. Samples collected in both studies were analyzed by Bifidobacterium -specific PCR and DGGE. The results showed that a stable bifidobacterial population was present throughout each study. Using both FISH and DGGE, we have shown that for modulation of the bifidobacterial populations in the gut, prebiotics are better candidates than probiotics, since inulin increased bifidobacterial numbers without changing the species composition, whilst the probiotic had almost no effect. Keywords: inulin, non-digestible oligosaccharides, prebiotics, probiotics, intestinal microflora, bifidobacteria, fluorescent in situ hybridization, probes, DGGE.