The role of flagella in the colonization of the intestine by Campyloba
cter jejuni was investigated by challenging infant mice with two flage
llated strains and their nonflagellated variants. The intestinal tract
s of infant mice were regularly colonized with motile strains, but not
by nonmotile variants. Colonization of mice with motile C. jejuni occ
urred with as few as 1000 bacteria per mouse.