The Battle for Iron between Humans and Microbes

Background: Iron is an essential micronutrient for bacteria, fungi, and humans; as such, each has evolved specialized iron uptake systems to acquire iron from the extracellular environment. Objective: To describe complex ‘tug of war’ for iron that has evolved between human hosts and pathogenic microorganisms in the battle for this vital nutrient. Methods: A review of current literature was performed, to assess current approaches and controversies in iron therapy and chelation in humans. Results: In humans, sequestration (hiding) of iron from invading pathogens is often successful; however, many pathogens have evolved mechanisms to circumvent this approach. Conclusion: Clinically, controversy continues whether iron overload or administration of iron results in an increased risk of infection. The administration of iron chelating agents and siderophore- conjugate drugs to infected hosts seems a biologically plausible approach as adjunctive therapy in the treatment of infections caused by pathogens dependent on host iron supply (e.g. tuberculosis, malaria, and many bacterial and fungal pathogens); however, thus far, studies in humans have proved unsuccessful.