Variations of Bacterial Populations in Human Faeces Measured by FISH with Group-Specific 16S rRNA-Targeted Oligonucleotide Probes

Abstract

The human intestinal tract contains a complex ecosystem consisting mainly of obligatory anaerobic bacteria, usually referred to as the normal flora. The composition of this flora plays an important role in human health and disease. To measure the effect of treatments aimed at modulating the normal flora, we have developed fluorescent 16S rRNA targeted oligonucleotide probes for numerically important groups of bacteria in the human intestine. These probes have been used for whole cell fluorescent in situ hybridization (FISH) to study the composition of the human intestinal flora over time. To facilitate detection and enumeration, we have combined FISH with automated microscopic image analysis. Measurement of 48 samples can be done overnight. In this study we have focused on the number of bifidobacteria present in faecal samples of different age groups. The percentage bifidobacteria in faeces ranges from 0 to 78.9 % depending on the age group. In each age group large variations were found. In faecal samples from formula-fed newborn infants we found individual differences ranging from 0 to 54.1 % bifidobacteria and in faecal samples from elderly (77-91 yr) individual differences ranged from 0.2 to 41.3%.