Abstract
Most microorganisms are destroyed by the host tissues through processes that usually involve phagocytosis and lysosomal disruption. However, some organisms, called intracellular pathogens, are capable of avoiding destruction by growing inside macrophages or other cells. During infection with intracellular pathogenic microorganisms, the element iron is required by both the host cell and the pathogen that inhabits the host cell. This minireview focuses on how intracellular pathogens use multiple strategies to obtain nutritional iron from the intracellular environment in order to use this element for replication. Additionally, the implications of these mechanisms for iron acquisition in the pathogen-host relationship are discussed.
Highlights
Intracellular pathogens are organisms that are capable of growing and reproducing inside host cells
Some examples of infectious diseases of global importance that are caused by intracellular microorganisms include tuberculosis, leprosy, typhoid, listeriosis, Legionnaire’s disease, malaria, leishmaniasis, Chagas’ disease, and toxoplasmosis
Macrophages require Fe as a cofactor for the execution of important antimicrobial effector mechanisms, including the NADPH- dependent oxidative burst and the production of nitrogen radicals catalyzed by the inducible nitric oxide synthase [13]. Intracellular bacteria such as Legionella pneumophila, Coxiella burnetii, Salmonella typhimurium, and Mycobacterium tuberculosis have an obligate requirement for Fe to support their growth and survival inside host cells [14]
Summary
Intracellular pathogens are organisms that are capable of growing and reproducing inside host cells. Facultative intracellular parasites, for example, bacteria such as Francisella tularensis, Listeria monocytogenes, Salmonella typhi, Mycobacterium spp., and Neisseria meningitidis, are capable of living and reproducing either inside or outside host cells. If the ingested bacteria have no intracellular survival mechanisms, the bacteria-containing phagosomes fuse with the lysosomal compartment, and bacteria are digested within 15– 30 min For this reason, the majority of intracellular bacteria and other parasites must keep host cells alive as long as possible while they are reproducing and growing [7, 9]. Intracellular bacteria such as Legionella pneumophila, Coxiella burnetii, Salmonella typhimurium, and Mycobacterium tuberculosis have an obligate requirement for Fe to support their growth and survival inside host cells [14]. It has been documented that deprivation of Fe in vivo and in vitro severely reduces the pathogenicity of M. tuberculosis, C. burnetii, L. pneumophila, and S. typhimurium [13,14,15]
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