The ability of rifampin-resistant Escherichia coli to colonize the mouse intestine is enhanced by the presence of a plasmid-encoded aerobactin-iron(III) uptake system.

Rifampin-resistant Escherichia coli are known to be poor colonizers of the animal intestine. In this report, we show that the colonizing ability of rifampin-resistant E. coli cells is increased dramatically in the presence of the aerobactin-mediated iron(III) uptake system. In contrast, the colonization by nalidixic acid-resistant E. coli does neither depend on the aerobactin-iron(III) nor on the dicitrate-iron(III) uptake system. Likewise, it does not depend on the production of the siderophore enterochelin.