organism may become pathogenic in the newborn if it is present in high numbers. There is still little understanding about the mechanisms that account for the beneficial effect of colonization with non-enteropathogenic E.coli strains. Both strains have g000d adhesive properties supported by the presence of tl (Colinfant strain) and FlA and F1C fimbriae (Mutaflor strain). The fact that receptors of the intestinal mucosa are occupied by the orally administered E.coli strains suggest a mechanism of interference preventing adhesion of other microbs including pathogens.Quantitative dominance of the implanted E.coli apparently associated with nutritive competition and colonization soon after birth carries several advantages for the first colonizer.By replacement of the natural, but incidental (sometime pathogenic) colonization of the intestine by a targeted, orally administered E.coli strain of advantageous properties we may have come upon one possibility of how to prevent infections of the alimentary tract but also other nosocomial infections particularly in formula-fed infants and high-risk newborns. CONCLUSIONS I. After oral administration of live vaccines COLINFANT and MUTAFLOR prepared from non-enteropathogenic E.coli strains, both strains colonized effectively the intestine in full-term and preterm infants and remained for many weeks.2. The presence of E.coli in the intestine stimulated significantly the antibody production in the gut, saliva and serum of colonized infants. 3. In full-term and premature infants the early presence of nonenteropathogenic E.coli strains in the intestine decreased significantly colonization of the intestine and also other mucosal surfaces of the body with pathogenic bacterial strains.4. The presence of the COLINFANT strain in the intestine decreased also significantly the number of nosocomial infections, the mortality rate in connection with infection, and the need for antibiotics.Both strains replaced pathogenic strains in carriers after treatment with antibiotics. Lodinová-Ldniková R, Tlaskalová-Hogenová H, Sonnenborn U. REFERENCENSLocal and serum antibody response in fullterm and premature infants after artificial colonization of the intestine with E.coli strain Nissle 1917 (Mutaflor). Pediatr Allergy Immunol 1992; 3: 43-8.8.Lodinová-Ldniková R, and Sonnenborn U. Effect of preventive administration of a nonpathogenic Escherichia coli strain on the colonization of the intestine with microbial pathogens in newborn infants. In mice, strain dependent cytokine production profiles are induced after oral administration of Lactobacillus.Such a cytokine profile seems to determine the direction

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