In natural settings, infants are often subject to colonization at birth with the aerobic and anaerobic flora of their mothers; they also receive specific immunoglobulin across the placenta before delivery and, later, through ingestion of breast milk. In contrast, babies born and cared for in hospital tend to be colonized by E. coli acquired from the environment [43][44]. The virulence of E. coli strains isolated in cases of UTI is correlated with the ability of the strain to adhere to uroepithelial cells [45]. This ability has been shown to be associated with the presence on the bacteria of proteinaceous, filamentous organelles called fimbria, which appear to recognize and bind to specific receptors on the epithelial cells [45]. Kallenius and associates [46] reported that 94% of the cases of infantile pyelonephritis they reviewed were due specifically to P-fimbriated E. coli.
On the basis of these observations, Winberg and collaborators [47] suggested two alternative preventive strategies: deliberate colonization with nonpathogenic bacterial flora during the newborn period or the promotion of rooming-in to facilitate close contact between newborns and their mothers. The first strategy is analogous to the active colonization of the umbilicus and nasal mucosa undertaken in the past to arrest epidemics of infection with Staphylococcus aureus [48].
These two strategies need to be evaluated further. One would expect both to have a low risk of complications. The second is in keeping with recent trends in maternal and infant care and could also have a low cost. If either strategy is successful, it may prove to be a more cost-effective way to prevent UTI among male infants than circumcision. Such an approach could also be applied to the prevention of UTI in female infants, since adherence of bacteria to epithelial cells also plays a role in the development of UTI in girls [45].