Evolution of the barrier effects against an exogenous drug-sensitive Escherichia coli strain after single or repeated oral administration to newborns and infants aged up to three months admitted to an intensive-care unit.

60 neonates--42 newborns 0-30 days old and 18 infants 31-90 days old--without previous antibiotic treatment were chosen and randomized into three groups (A, B, C). The strain of Escherichia coli administered was antibiotic-sensitive and azide-resistant (E. coli AZ). The digestive implantation was quantified by an index. We studied the variations of this index between the single administration group (A) and the 5 administrations group (B) and with age in both groups. Drug-resistant enterobacteria were also numbered in each stool, and their variations were studied by comparing groups A and B to a control group (C) receiving no administration. Multiple administrations did not lead to different results from the single ones. Age played a negative role in the colonizations after single administration, but a positive one after multiple administrations. Drug-resistant enterobacteria were not affected by any procedure. The drug susceptibility of E. coli AZ was lost in only 1 infant.