[Effect of age on permissive barrier effect against a strain of enterobacteria exerted by a complex bacterial flora in the digestive tract of mice reared in isolator (author's transl)].

A permissive barrier effect against Escherichia coli was observed in the faeces of a first group of mice associated with a complex microbial flora. This effect was transmitted to 6 other groups of mice by inoculation of a fecal suspension originated from a mouse of group I. Although mice were kept in isolator in constant biotic and abiotic environmental conditions, the expression of the barrier effect was very variable during several days after inoculation, then became stabilized in every group, but more slowly in group I than in the others. The expression of this barrier effect was compared in male and female mice aged five weeks or 6 months. The barrier effect was significantly more efficient in older than in young mice whatever the sex.