FIG 7.
Fitness of UMH9 siderophore mutants in a murine model of bacteremia. CBA/J mice were infected with 5 × 107 CFU/mouse in a 1:1 mixture of the wild type and the indicated mutant strain via the tail vein. Mice were euthanized at 24 h and the kidneys (A), spleen (B), and liver (C) were collected from each mouse. Organs were homogenized. Homogenates were diluted and selectively plated. The relative fitness for each mutant compared to that of the wild type was calculated as a competitive index (CI). The dotted line represents a CI of 1.0, meaning that the two strains competed equally. Solid lines represent median CI. Statistics were calculated using the Wilcoxon signed-rank test with a theoretical median of 0 (*, P < 0.05; **, P < 0.01).