Comparison of Composition of Faecal Microbiota and Metabolism of Faecal Bacteria among 'Human-Flora-Associated' Mice Inoculated with Faeces from Six Different Human Donors

Abstract

The composition of faecal microbiota, enzyme activities of faecal bacteria and concentrations of faecal putrefactive products and short chain fatty acids (SCFAs) were studied in 'human-flora-associated' (HFA) mice inoculated with six different human faeces. The composition of major faecal bacteria of HFA mice was similar to that of inoculated human faeces, although bifidobacteria were eliminated from some HFA mouse groups. β-Glucuronidase activity of intestinal bacteria in HFA mice was similar to that in humans. However nitroreductase activity was closer to that in conventional mice than in humans. Although the concentrations of faecal putrefactive products and SCFAs in HFA mice were much lower than those in humans, the composition of faecal SCFAs of HFA mice was similar to that of humans. Individual variations of putrefactive products and SCFAs observed among inoculated human faeces were not reflected in HFA mice, and variations among six HFA mice groups were not obvious. Bacterial composition and metabolism in HFA mice were maintained in their offspring by breeding. These findings indicate that HFA mice provide a stable and valuable tool for studying the ecosystem and metabolism of the human faecal microbiota, but they have some limitations as a model. Keywords: human-flora-associated mice, faecal microbiota, enzyme activities, putrefactive products, short chain. fatty acids