To this end, several groups have described the anti-humoral immune response in physiologic and pathological situations [12, 13, 33, 39, 41, 42, 44]. antigens provide a better predictor of ongoing contamination? Methods A case-control study was performed. Sera were collected from 35 consecutive patients with culture-confirmed (methicillin-sensitive or methicillin-resistant infections and murine tibial implant infections were used to evaluate a multiplex immunoassay for immunoglobulin titers against 14 recombinant antigens. All patients were treated with organism-targeted antibiotic therapy and appropriate, timely medical procedures. Treatment response was monitored with clinical examination, erythrocyte sedimentation rate, C-reactive protein, and resampling of the contamination site for the pathogen as needed. Elevated inflammatory markers or persistent positive culture results were considered evidence of ongoing contamination. Treatment provided was considered standard-of-care therapy in our medical center and all patients were treated jointly with a board-certified infectious disease specialist. Results Four antigens elicited more than 65% of the measurable IgG, the most dominant being against iron-regulated surface determinant protein B (IsdB). Patients with infections had different patterns of elevated IgG titers, so that no single titer was elevated in more than 50% of patients with infections (area under CCT251545 the curve [AUC] 0.80). Multivariate analysis of IgG titers yielded greater predictive power of contamination (AUC = 0.896). Patients with infections who had high titers against IsdB (median of survivors, 7.28 [25%C75% range, 2.22C21.26] vs median of patients with infection-related death, 40.41 [25%C75% range, 23.57C51.37], difference of medians, 33.13; p = 0.043) and iron-regulated surface determinant protein A (IsdA) median of survivors, 2.21 [25%C75% range, 0.79C9.11] vs median of patients with infection-related death, 12.24 [25%C75% range, 8.85C15.95], difference of medians, 10.03; p = 0.043) were more likely to die from infections than those who did not have SELL high titers of IsdB. Conclusions Measurement of the host antibody response is usually a predictor of ongoing contamination that may prove to have prognostic value. Future studies will seek to enlarge the patient population with infections to allow us to reduce the number of antigens required to achieve a stronger predictive power. Clinical Relevance Measurement of the immune response against with this diagnostic tool may help guideline future studies on prophylaxis and therapy in an era of personalized medicine and pathogen-specific therapies. Electronic supplementary material The online version of this article (doi:10.1007/s11999-015-4354-2) contains supplementary material, which is available to authorized users. Introduction Deep musculoskeletal infections, including osteomyelitis associated with prosthetic joint infections, are a major clinical problem and are gradually increasing. Approximately 1 million total joint replacements are performed in the United States annually, and the demand is usually expected to increase to more than 4 million by 2030 [22]. Even though the introduction of improved surgical and patient-care procedures has reduced the number of prosthetic joint infections, the rate of primary prosthetic joint infections remains in the range of 0.5% to 3% [9, 34]. As a result, there are 20,000 new prosthetic joint infections per year, and this number is usually expected to increase along with the demand for total joint replacements [23]. The most consequential pathogen is usually (strains infect 100,000 patients and contribute to 18,650 deaths annually [21]. This pathogen further complicates a chronic prosthetic joint contamination, which has only a 50% success rate in a two-stage revision [29]. As a result, there is renewed interest in vaccines and immunomodulatory approaches to prevent and treat osteomyelitis. There is also an increasing need for effective diagnostics of contamination and the host response. Although diagnostic criteria for prosthetic joint infections exist [30], rapid and accurate diagnosis remains challenging for many patients with infections [10, 11, 25]. Additionally, while serum diagnostics are available for several CCT251545 microbial pathogens, no host immunity test is usually available for infections. To this CCT251545 end, several groups have described the anti-humoral immune response in physiologic and pathological situations [12, 13, 33, 39, 41, 42, 44]. Gedbjerg et al. [15] described an antiglucosaminidase antibody test to assess contamination and prognosis in patients undergoing orthopaedic surgery who have a confirmed contamination. The results showed an interesting pattern from this single antigen analysis that warranted development of a multiplex assay to test the hypothesis that measurement of the magnitude and quality of a patients antibody response will provide a diagnostic tool for identifying patients who have ongoing infections and a prognostic tool for directing additional intervention for patients at the greatest risk for poor outcomes. To address this, we described the development and validation of a multiplex immunoassay for characterizing a patients immune response against 14 known antigens, which we then used to answer four CCT251545 questions: (1) Do certain antigens predominate in the immune response against for mice and humans? (2) Is there a predominant pattern of antigens recognized by patients and mice with infections?.