[Implantation of a strain of "Escherichia coli" in the digestive tract of human new-borns: barrier effect against antibioresistant "E. coli" (author's transl)].

Twenty-two healthy human new-borns were inoculated within two hours of birth with a strain of Escherichia coli. This strain was isolated from the faecal flora of an healthy adult and was plasmid-free, nontoxigenic in vitro or in vivo, and sensitive to all usual antibiotics. This strain became established at a high population level within two days in all new-borns and remained at a very high level during the following days in almost all cases (86%). Strains of E. coli resistant to ampicillin or tetracycline were found in 6 of 22 inoculated infants as well as in 7 of the 24 control infants. These resistant strains remained at a very high level in the control infants but disappeared, or decreased to a subdominant level, in the inoculated infants. These results show that a totally innocuous strain of E. coli can exert in holoxenic conditions a barrier effect on antibiotic resistant E. coli strains. They also suggest the interest of inoculating such a strain at birth in order to prevent proliferation of potentially pathogenic bacteria.