[Effect of orally administered bovine lactoferrin and bovine IgG on the establishment of Escherichia coli in the digestive tract of gnotobiotic mice and human newborn infants].

The bacteriostatic effect of the association bovine lactoferrin (LF) and bovine IgG (IgG) was studied in vitro and in vivo against two Escherichia coli strains, S17 and EMO1, isolated from the faecal flora of mouse and man, respectively. These two strains were sensitive in vitro to the bacteriostatic effect of LF + IgG. A kinetic study of the in vivo establishment of E. coli S17 was followed in axenic mice associated with that strain. Seven hours after inoculation, no difference was observed in the faecal level of E. coli between control mice and mice fed the same diet supplemented with LF + IgG. An in vivo study was also carried out in human newborns receiving either maternized milk (Nursie) or the same milk supplemented with LF + IgG during the first 48 h of life. One group of babies was inoculated at birth with E. coli EMO1, while another was not. Between the ages of 1 and 5 days, the kinetics of establishment of the E. coli strains spontaneously found in the digestive tract of non-inoculated babies was not significantly different between the group which received milk supplemented with LF + IgG and that which did not. This result was confirmed in infants inoculated with E. coli EMO1. Likewise, the faecal levels of E. coli EMO1 were similar in the supplemented and non-supplemented babies, and, already from day 1, the population level was high and only slight individual variations between babies of the same group were observed. These findings show that the in vitro bacteriostatic effect of LF + IgG on the growth of E. coli strains is not found in vivo.