Intestinal colonization and antibody response

Rapid bacterial colonization of the gastrointestinal tract takes place immediately after birth. Only a few of theEscherichia coli strains colonizing the gut of healthy full-term neonates expressed MS pili. On the other hand, mostE. coli strains isolated carried MR pili resembling the P-fimbriae which are a known virulence factor for pyelonephritogenicE. coli. The presence of serum antibodies against pili and K antigens ofE. coli after vaccination did not influence the capacity ofE. coli to colonize and persist in the intestine of experimental animals.