Mass Spectrometry-Based Proteomic Profiling of Sonicate Fluid Differentiates Staphylococcus aureus Periprosthetic Joint Infection from Non-Infectious Failure: A pilot study

Purpose: This study aims to use proteomic profiling of sonicate fluid samples to compare host response during Staphylococcus aureus-associated periprosthetic joint infection (PJI) and non-infected arthroplasty failure (NIAF) and investigate novel biomarkers to increase diagnostic accuracy. Experimental Design: In this pilot study, eight sonicate fluid samples (four from NIAF and four from Staphylococcus aureus PJI) were studied. Samples were reduced, alkylated and trypsinized overnight, followed by analysis using liquid chromatography-tandem mass spectrometry (LC-MS/MS) on a high-resolution Orbitrap Eclipse mass spectrometer. MaxQuant software suite was used for protein identification, filtering, and label-free quantitation. Results: Principal component analysis of the identified proteins clearly separated S. aureus PJI and NIAF samples. Overall, 810 proteins were quantified in any three samples from each group and 35 statistically significant differentially abundant proteins (DAPs) were found (2-sample t-test p-values [≤]0.05 and log2fold-change values [≥]2 or [≤]-2). Gene ontology pathway analysis found that microbial defense responses, specifically those related to neutrophil activation, were increased in S. aureus PJI compared to NIAF samples. Conclusion and Clinical Relevance: Proteomic profiling of sonicate fluid using LC-MS/MS, alone or in combination with complementary protein analyses, differentiated S. aureus PJI and NIAF in this pilot study.