Yersiniae and iron. A study in host-parasite relationships.

Most enterobacteria obtain the iron they require for growth by producing low-molecular-weight high-affinity iron ligands known as siderophores. These substances chelate and solubilize iron making it available to bacteria. The pathogenic Yersiniae produce no detectable siderophores; thus, they proliferate poorly or not at all under conditions of iron limitation. Most systemic infections with Yersinia enterocolitica occur in patients who are overloaded with iron. This may be due to the presence of excess iron in the tissues of such patients, but the adverse effects of excess iron on immune responsiveness may also be partly responsible. Many patients with iron overload receive treatment with desferrioxamine B, a bacterial siderophore which promotes growth of Y. enterocolitica in vitro and in vivo. Thus, desferrioxamine B may add to the risk of systemic yersiniosis developing in patients with siderosis. Some strains of Yersinia frederiksenii, Yersinia intermedia and Yersinia kristensenii produce the hydroxamate siderophore aerobactin, but, paradoxically, they appear to be unable to proliferate in tissues.