In vivo growth of Staphylococcus lugdunensis is facilitated by the concerted function of heme and non-heme iron acquisition mechanisms

Abstract

Acquisition of iron underpins the ability of pathogens to cause disease and Staphylococcus lugdunensis has increasingly been recognized as a pathogen that can cause serious infection. In this study, we sought to address the knowledge gap that exists regarding the iron acquisition mechanisms employed by S. lugdunensis, especially during infection of the mammalian host. Here we show that S. lugdunensis utilizes diverse genome encoded iron acquisition mechanisms to satisfy its need for this nutrient. Indeed, S. lugdunensis can usurp hydroxamate siderophores, and staphyloferrin A and B from S. aureus, using the fhuC ATPase-encoding gene. Acquisition of catechol siderophores and catecholamine stress hormones necessitates the presence of the sst-1 transporter-encoding locus, but not the sst-2 locus. Iron-dependent growth in acidic culture conditions necessitates the feoAB locus. Heme iron is acquired via expression of the iron-regulated surface determinant (isd) locus. During systemic infection of mice we demonstrate that while S. lugdunensis does not cause overt illness, it does colonize and proliferate to high numbers in the kidneys. By combining mutations in the various iron acquisition loci, we further demonstrate that only a strain mutated for all of isd, fhuC, sst-1, and feo, versus combination mutants carrying wild type copies of any one of those loci, was attenuated in its ability to proliferate to high numbers in kidneys. Taken together our data reveal that S. lugdunensis requires a repertoire of both heme and non-heme iron acquisition mechanisms to proliferate during systemic infection of mammals. ImportanceAcquisition of iron underpins the ability of pathogens to cause disease and Staphylococcus lugdunensis has increasingly been recognized as a pathogen that can cause serious infection. In this study, we sought to address the knowledge gap that exists regarding the iron acquisition mechanisms employed by S. lugdunensis, especially during infection of the mammalian host. Owing to an inability to synthesize siderophores, growth of S. lugdunensis is dramatically impaired in the presence of transferrin or serum, yet S. lugdunensis nonetheless uses several other genome-encoded iron acquisition mechanisms, in concert, to proliferate within the mammalian host. Therefore, the development of interventions that target bacterial iron acquisition systems should consider the overlapping function of distinct metal acquisition strategies deployed by bacterial pathogens.