Composition of faecal microbiota of elderly people

Abstract

Elderly people are susceptible to intestinal dysbiosis such as constipation. In the present study, the gut microbiota of 15 elderly people was investigated by fluorescent in situ hybridization (FISH), denaturing gradient gel electrophoresis (DGGE), cloning and sequence analysis. Eighteen 16S rRNA-based oligonucleotide probes were applied to faecal samples from 15 healthy elderly volunteers (aged > 75 years) to enumerate the predominant bacterial groups. The results show that the composition of the faecal microbiota of these elderly people is different from that of adults. The Ruminococcus group (type species R. flavefaciens) becomes the most predominant group in the elderly, contributing 9.6% of the total cells. The percentages of Enterobacteriaceae, the Eubacterium cylindroides group and the Lactobacillus/ Enterococcus group are also higher in faecal samples from the elderly than in those from a group of healthy volunteers (aged 20-55 years). In contrast to this, the contributions of the three most predominant groups in adults, Bacteroides/Prevotella, the E. rectale/C. coccoides group and Faecalibacterium, are lower in elderly people. In some samples, <35% of the total hybridizable cells were identified. DGGE, cloning and sequence analysis of one of these samples showed that among the 12 possible predominant bacterial groups in this sample, 10 of them should react with our group-specific probes. The reasons why just small proportions of total bacteria are detected in some faecal samples with our probe set need further investigation.