Implantation and in vivo antagonistic effects of antibiotic-susceptible Escherichia coli strains administered to premature newborns.

Two antibiotic-susceptible and non-pathogenic Escherichia coli strains were administered to hospitalized premature infants in order to protect them from intestinal colonization by hospital-acquired antibiotic-resistant enteric organisms (EOs). Three groups of 16 premature newborns received respectively strain ECA, strain EMO and both strains simultaneously. A fourth group was used as a control. Resistant EOs became spontaneously established in the digestive tract of a majority of the unadministered children. Both ECA and EMO were able to colonize the digestive tract of a majority of the subjects, and reached high population numbers (greater than 10(7)/g) in the faeces. Both strains appeared as able to reduce significantly the establishment of antibiotic-resistant EOs. This effect was more prominent with EMO, which also impaired the implantation of ECA when both strains had been administered simultaneously. The use of such innocuous microorganisms could thus constitute an additional means of preventing nosocomial infections of intestinal origin.