Investigating the Role of S. aureus Citrate Metabolism in Prosthetic Joint Infection

Prosthetic joint infection (PJI) is a complication following arthroplasty that occurs in approximately 1-3% of patients, with ~50% of cases caused by methicillin-resistant Staphylococcus aureus (S. aureus). Biofilm formation evolves as bacteria multiply, producing a complex extracellular matrix that creates a heterogeneous population with unique metabolic properties. S. aureus is metabolically flexible, allowing it to colonize various niches and establish chronic infections. Bacterial-derived metabolites play an important role in biofilm infection, which is reflected by the fact that several tricarboxylic acid cycle (TCA) intermediates are critical for biofilm development. Our laboratory has characterized an in vivo mouse model of PJI and identified macrophages (Mφs), anti-inflammatory granulocytic myeloid-derived suppressor cells (G-MDSCs), and polymorphonuclear cells (PMNs) as the predominant leukocyte infiltrates, all of which are also present in human PJI. Previous work from our group has characterized several metabolites that are important for promoting S. aureus persistence during PJI; however, it is unclear how S. aureus adapts in response to leukocyte exposure to regulate its metabolism to promote biofilm formation and establishment. Our novel bacterial single-cell RNA sequencing (Bsc-RNA seq) approach has revealed that Mφs, G-MDSCs, and PMNs elicit distinct metabolic changes in S. aureus biofilm, namely, the expression of genes involved in citrate metabolism (gltA, acnA, and icd). While the role of AcnA has been examined in a S. aureus skin and soft tissue infection model, its role, along with the other citrate enzymes (GltA and Icd) in biofilm development under leukocyte pressure and during PJI, remains elusive. The overarching hypothesis of this fellowship is that S. aureus citrate metabolism is upregulated to adapt to leukocyte pressure and promote biofilm development and pathogenesis. The role of citrate metabolism in biofilm development and S. aureus pathogenicity will be examined in the following Specific Aims. 1) Investigate the role of S. aureus biofilm citrate metabolism under leukocyte pressure and 2) Elucidate the role of citrate metabolism on S. aureus pathogenesis in PJI. The results from this fellowship will provide new insights into S. aureus metabolic adaptations under leukocyte pressure and within the PJI niche that could represent future therapeutic targets. Project Number: 1F31AI197749-01 | Fiscal Year: 2026 | NIH Institute/Center: National Institute of Allergy and Infectious Diseases (NIAID) | Principal Investigator: Nichole Brandquist | Institution: UNIVERSITY OF NEBRASKA MEDICAL CENTER, OMAHA, NE | Award Amount: $41,509 | Activity Code: F31 | Study Section: Special Emphasis Panel[ZRG1 F07A-W (20)] View on NIH RePORTER: https://reporter.nih.gov/project-details/1F31AI19774901