Fecal colonization with pyelonephritogenic Escherichia coli in neonates as a risk factor for pyelonephritis.

The aim of the study was to investigate the properties of fecal P-fimbriated Escherichia coli strains in neonates and to relate these characteristics to the later development of acute pyelonephritis. In a 2 1/2 year prospective study of the children admitted to a particular neonatal ward, 113 children were found to be fecally colonized with a P-fimbriated Escherichia coli strain. However, only one of these children developed pyelonephritis from this strain during the first year of life. The combined results of serotyping, biochemical phenotyping and determination of outer membrane protein pattern as clonal characterization suggested that only 26 of the P-fimbriated strains belonged to a pyelonephritogenic Escherichia coli clone. It is concluded that the risk of a child colonized with an Escherichia coli strain belonging to such a clone of developing pyelonephritis, as calculated in this study, is about 4%.