Role of iron in the pathogenesis of Vibrio vulnificus infections

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Abstract
Infections with V. vulnificus resulting in septicemia and high mortality are often correlated with pre-existing liver disease and hemochromatosis. As these conditions are associated with impaired Fe metabolism and as Fe availability in the host is implicated in the pathogenicity of a number of bacterial infections, the role of Fe as a possible factor in the pathogenesis of V. vulnificus was examined. Injection of mice with Fe resulted in a lowering of the LD50 from 106 to 1.1 cells and in a reduction in the time of death postinfection. Elevated serum Fe levels were also produced by damaging livers with injections of CCl4. The inoculum size required to kill these mice was directly correlated with serum Fe levels. Since the portal of infection of this organism may be by ingestion of contaminated seafood, the effects of Fe upon orally induced infection were also studied. The effects of adding Fe, transferrin or Desferal (an iron chelate) upon the growth of V. vulnificus in human and rabbit sera were also examined. Fe appeared to be the limiting factor in the ability of this organism to survive or grow in mammalian sera. These results, both in vitro and in vivo, provided strong evidence that Fe may play a major role in the pathogenesis of V. vulnificus.