S almonella acquires ferrous iron from haemophagocytic macrophages

Summary Bacteria harbour both ferrous and ferric iron transporters. We now report that infection of macrophages and mice with a S almonella enterica   T yphimurium strain containing an inactivated feoB ‐ encoded ferrous iron transporter results in increased bacterial replication, compared to infection with wild type. Inactivation of other cation transporters, SitABCD or MntH , did not increase bacterial replication. The feoB mutant strain does not have an intrinsically faster growth rate. Instead, increased replication correlated with increased expression in macrophages of the fepB ‐ encoded bacterial ferric iron transporter and also required siderophores, which capture ferric iron. Co‐infection of mice with wild type and a feoB mutant strain yielded a different outcome: FeoB is clearly required for tissue colonization. In co‐infected primary mouse macrophages, FeoB is required for S .   T yphimurium replication if the macrophages were IFN γ treated and contain phagocytosed erythrocytes, a model for haemophagocytosis. Haemophagocytes are macrophages that have engulfed erythrocytes and/or leucocytes and can harbour S almonella in mice. These observations suggest that S almonella acquires ferrous iron from haemophagocytic macrophages.