Metal ions and infectious diseases. An overview from the clinic

Trace elements (TEs) are required by both humans and bacterial pathogens. Although metal ion homeostasis is tightly controlled in humans, growing evidence suggests that pathogens utilize a variety of means designed to circumvent the sequestration of TEs. Colonizing pathogenic microorganisms employ a variety of strategies to sense, acquire, store, and export metal ions in the vertebrate host which include the biosynthesis and utilization of siderophores, and the expression of high-affinity metal-ion transporters. For iron, selenium, and zinc, significant correlations have been shown between TE levels in plasma, serum, or tissues, and the prevention or treatment of a variety of infectious diseases; fewer such data exist for copper, chromium, or manganese. TEs are often employed as antioxidants, and as supplements in patients with TE-deficient states. The role of TE supplementation in humans as antioxidants remains controversial, but has demonstrated significant benefit in the role of selenium for patients with sepsis, and of zinc for the prevention of several infectious diseases.