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Influence of iron on infection

1986; Elsevier BV; Volume: 151; Issue: 2 Linguagem: Inglês

10.1016/0002-9610(86)90090-5

1879-1883

CW Ward,

Hemoglobinopathies and Related Disorders

Sepsis, the result of uncontrolled bacterial growth in a host, is a major clinical problem. Although antibiotics have significantly altered the course of medical care, they have not prevented bacteria from bringing patients to their physiologic knees. Organisms have persisted for millions of years by being genetically “smart” and flexible, and the ease with which bacteria adapt is repeatedly forgotten with the introduction of each new and “better” antibiotic. Adaptation is important for bacteria to survive, but they are helped in the process by specific conditions. When combined with iron, it takes fewer bacteria to establish an infection or to kill a host than when iron is absent. For example, lo4 cells of Escherichia coli injected into a small, healthy mouse is no threat to the animal; however, if the same inoculum is given with an iron salt or an iron-containing protein such as hemoglobin, the inoculum becomes lethal. This applies equally to aerobes, anaerobes, and mixed infections [l-4]. For reasons not fully known, prokaryotic and eukaryotic cells evolved a dependence on iron for multiple metabolic processes, working in concert with proteins of transport, storage, oxygen binding, and functioning enzyme systems. It is believed this was due in large part to iron’s unique combination of properties: (1) Iron is universally abundant; there is a tendency for more of it to be created than other elements [5,6] because it has the most stable nucleus of all the elements. (2) Iron exists in two oxidative states in aqueous solutions, ferrous (Fe+2) and ferric (Fe+3). (3) Iron has a range of oxidation reduction potentials (+350 mV to -500 mV), allowing it to participate in a broad scope of chemical reactions [7,8]. Some examples are the catalysis of oxidation by oxygen and hydrogen peroxide, the decomposition of peroxide and superoxide, oxidative phos-