Characteristic faecal flora of NC mice.

The composition of faecal flora of NC mice was compared with that of CF #1 mice. NC- and CF #1-germfree (GF) mice were cage-mated with NC- or CF #1-conventional (CV) mice in an isolator. The faecal flora of these ex-GF mice was dependent on the recipient mouse strain modifying colonization by the donor mouse bacteria. Although NC- and CF #1-pups removed by hysterectomy were fostered to different strains, almost all these mice at 8 weeks old had a strain characteristic pattern of faecal flora regardless of the foster strains. In GF mice mono-associated with a Lactobacillus strain or a Bifidobacterium strain isolated from faeces of CV mice, the numbers of these bacteria in the stomach and small intestine of NC mice were lower than those of CF #1 mice. In GF mice associated with chloroform-treated faeces of CV mice, and a Lactobacillus strain or a Bifidobacterium strain, the numbers of these bacteria in the stomach and all parts of the intestine of NC mice were considerably lower than those of CF #1 mice. These results suggested that the composition of faecal flora of NC mice were characteristic, i.e. the fact that the numbers of lactobacilli were low compared with CF #1 mice with ordinary faecal flora and the colonization of bifidobacteria, peptococcaceae and eubacteria on ES agar in NC mice intestine differed, was due to genetic factors.