HIF1A and susceptibility to pneumonia measurement: To test the hypothesis that K. pneumoniae siderophores stabilize HIF-1α during pneumonia, we utilized a transgenic mouse model that expresses a fusion protein of luciferase with the oxygen-dependent domain (ODD) (ODD-Luc) of HIF-1α that is subject to prolyl hydroxylation and becomes stabilized under low oxygen or low iron conditions (29, –, 31).