Isolation of nonchemotactic mutants of Campylobacter jejuni and their colonization of the mouse intestinal tract

Three nonchemotactic mutants (D54, Y14, and N74) of Campylobacter jejuni were isolated from wild-type strain FUM158432 by either the negative swarming or liquid gradient method with brucella broth as the attractive substance. Strains D54 and Y14 were isolated after mutagenesis with methyl methanesulfonate, and N74 was isolated from a nonmutagenized culture. These mutants all failed to swarm on a semisolid medium and did not show any chemotactic behavior in the hard-agar plug assay method for any of the chemicals which act as attractants for the wild-type strain. They had intact flagella and were actively motile. Swimming behavior examined by a video tracking technique showed that the mutants swim only straight, without any tumbling. When suckling mice were challenged orally with approximately 10⁵ CFU of these mutant strains, all of the mutants were cleared from the intestinal tract by 48 h. In contrast, the wild-type strain colonized the intestinal tracts of all mice challenged with 10² CFU. We concluded that chemotactic movement is important for colonization of the intestinal tract of suckling mice by C. jejuni.