Importance of manganese uptake in uropathogenic Escherichia coli CFT073 during urinary tract infection

Urinary tract infections (UTIs) are the second most common bacterial infection, with the majority of cases caused by uropathogenic Escherichia coli (UPEC). To establish infection, UPEC requires iron and other transition metals to support essential metabolic processes. In response, the host limits access to these metals during infection, generating a nutrient-restricted environment that pathogens must overcome. We investigated the role of three iron transport systems, Sit, Feo, and Efe, in the prototypical UPEC strain CFT073 during UTI. In the murine model of infection, loss of Sit, but not Feo or Efe, resulted in a significant fitness defect in the urine. Because Sit can transport both iron and manganese, we hypothesized that its contribution to virulence extends beyond iron import. Consistent with this idea, deletion of sitABCD (Δ sit ) or both sitABCD and an additional manganese transporter mntH (Δ sit/ Δ mntH ) impaired growth in metal-restricted minimal medium. Interestingly, mntH deletion increased sitA transcription, but the inverse was not observed, suggesting compensatory regulation under cationic-limiting conditions. All three mutants (Δ sit , Δ mntH , and Δ sit/ Δ mntH ) displayed significant sensitivity to hydrogen peroxide-induced killing, with the double mutant exhibiting the strongest defect. In the murine model of ascending UTI, the Δ sit/ Δ mntH strain was severely attenuated compared to wild type in the urine, bladder, and kidneys. Collectively, these findings demonstrate that manganese uptake, mediated primarily by Sit and MntH, is critical for oxidative stress resistance and bacterial fitness during infection. This highlights the importance of manganese acquisition as a determinant of UPEC pathogenesis in the iron-limited urinary tract.