Colonization and persistence of Escherichia coli phenotypes in the intestines of children aged 0 to 18 months.

The aim of the present investigation was to study the intestinal colonization of Escherichia coli in newborn children, and to determine which strains become residential within the human intestine. The E. coli flora of 89 newborn children was studied by repeated sampling during their first 11 or 18 months of life. The E. coli isolates from the samples were subdivided into phenotypes by the aid of biochemical fingerprinting, a method which measures the kinetics of 24 selected biochemical tests as a tool for discriminating bacterial strains. It was found that E. coli strains colonizing children soon after birth persisted longer than strains colonizing them later. Especially those phenotypes which were defined as hospital strains persisted longer. Certain phenotypes were commonly found among the children, and these phenotypes were more persistent and more homogeneous than other phenotypes with respect to their pattern of biochemical activities. They might be specially adapted to colonize the human intestine. It was concluded that the generally long persistence of the first E. coli strains colonizing a newborn child indicates that the first case of bacterial colonization in children may be an event too important to be allowed to happen at random.