The role of the O-antigen lipopolysaccharide on the colonization in vivo of the germfree chicken gut by Aeromonas hydrophila serogroup O:34.

We compared the ability of different Aeromonas hydrophila strains from serogroup O:34 grown at different temperatures to colonize in vivo the germfree chicken gut. We found a good colonization when the strains were grown at 20 degrees C but not when they were grown at 37 degrees C. We previously described that these strains were able to form the O-antigen lipopolysaccharide (LPS) when they grow at low temperature but not at high temperature. We also obtained by transposon mutagenesis mutants only devoid of the O-antigen LPS (rfb mutants), and showed that they were unable to colonize the germfree chicken gut. All these results prompted us to conclude that the O-antigen LPS, in these strains, is a main factor for colonization in this animal model system.