Hepcidin deficiency and resulting iron overload promote mortality from siderophilic but not nonsiderophilic Y enterocolitica. (A) Survival after oral infection with increasing doses of siderophilic Y enterocolitica O9 (10⁴-10⁸ CFUs per mouse) of WT mice with normal iron status or naturally iron-loaded HKO mice. *Comparison of HKO to WT mice infected with the same dose. (B) Survival curve for WT or naturally iron-loaded HKO mice infected through oral gavage with 10⁸ CFUs per mouse Y enterocolitica serotype O9 (siderophilic) or O8 (nonsiderophilic). (C) Survival of naturally iron-loaded or dietary iron-depleted HKO mice after oral infection with 10⁸ CFUs per mouse Y enterocolitica O9. Infection with siderophilic O9 bacteria resulted in significantly greater mortality than infection with nonsiderophilic O8 bacteria in iron-loaded HKO mice. Survival is defined in “Methods.” Statistical comparison of survival was performed using multifactorial Kaplan-Meier log-rank analysis.