The goal of this study is to test a new way to diagnose and track treatment of spine infections caused by the bacteria Staphylococcus aureus.

Ongoing Staphylococcus aureus (S. aureus) infections of the spine associated with orthopedic hardware implants elicit prominent immune responses against a repertoire of proteins characteristic of the invading pathogen. Antibodies specific for these antigens can be measured in the serum or in a novel sample created by culturing circulating Antibody Secreting Cells (ASC) in vitro where they create an analytic fluid called here "medium enriched for newly synthesized antibodies" (MENSA). The hypothesis of this study addresses three essential attributes of this analytic approach that can yield both a valuable tool for research on spinal infections and in the future, this can be developed a clinical tool for diagnosis and monitoring of therapeutic success in patients. By measuring the emergence of these signature antibodies in the serum and/or MENSA, the goals of this study are: 1) To differentiate between patients with an ongoing S. aureus infections, not just "general infection, in the spine using only blood samples; 2) To track the success (or failure) of therapeutic interventions; and 3) to distinguish spinal infections from S. aureus infections in other sites by the repertoire of antibodies that are elicited.

Inclusion Criteria:

• patients with known or suspected spinal infections associated with spinal orthopedic implant(s);
• patients over 18 years of age and younger than 85;
• patients undergoing spinal revision surgery.

Exclusion Criteria:

• Diagnosed as immuno-compromised or immuno-suppressed based on medication use;
• On-going or previously diagnosed musculoskeletal infections associated non-spine hardware (e.g., prosthetic hip, prosthetic knee, prosthetic shoulder);
• Current diabetic foot ulcer/infection;
• Patients undergoing cancer treatment (including radiation and chemotherapies);
• Pregnancy;
• Absence of a spleen;
• Over the age of 85 or under the age of 18.
• Weigh less than 110 pounds, or for which it would otherwise be unsafe for them to undergo a blood draw.

Patients undergoing revision spine surgeries at the University of Colorado Hospital. with suspected infection of previous instrumentation will be offered enrollment. The enrolled patients will be identified prior to surgery by the surgeons and research staff through radiographs and images contained in the medical records and the parameters of suspected infection which include:

• Blood biomarkers: elevated C-reactive protein (CRP) and ESR (erythrocyte sedimentation rate), and white blood cell count
• X-ray imaging: to show osteolysis and possibly implant-loosening
• MRI or CT imaging: looking for fluid accumulations, evidence of inflammation, enhancements.