Rapid detection and characterization of biofilms on shoulder implants

The National Institute of Arthritis and Musculoskeletal and Skin Diseases awarded Rush University Medical Center $366,988 on September 1, 2026, under the Arthritis, Musculoskeletal and Skin Diseases Research program (CFDA 93.846) to develop a rapid detection tool for Cutibacterium acnes infection on shoulder implants using Raman spectroscopy.

The project establishes a diagnostic method to identify C. acnes biofilms on removed shoulder arthroplasty implants by analyzing their chemical composition via high-resolution and high-throughput Raman spectroscopy. The work addresses a critical clinical gap: C. acnes infections are difficult to diagnose due to the organism's slow growth and culture false-positive rates, yet positive C. acnes cultures appear in 59–100% of aseptic shoulder revision surgeries, suggesting unrecognized biofilm-driven implant failure. The ultimate goal is a point-of-care diagnostic tool to confirm C. acnes and other infections intra- or peri-operatively and clarify C. acnes's role in implant loosening.

Performance occurs in Chicago, Illinois, with a period of performance from September 1, 2026, through August 31, 2028. The assistance type is Project Grant (R21AR088391).

Abstract

This project aims to establish a novel tool for the rapid detection of cutibacterium acnes (c. Acnes) infection in shoulder arthroplasty (SA). This tool utilizes the chemical signature-as measured via raman spectroscopy- of the c. Acnes biofilm adhering to the implant surface. Our long-term goal is to develop a point-of-care tool for diagnosing c. Acnes and other infections and further elucidate the role of c. Acnes in implant failure. The incidence of primary SA is expected to reach 350K/year in the US in 2025 and is rapidly increasing. Up to 8% of primary SAS need revision surgery because of periprosthetic joint infection (PJI). Within SA revisions classified as aseptic, 59-100% have positive c. Acnes cultures. These unexpected positive cultures suggest that many seemingly aseptic revisions may actually be caused by an underlying c. Acnes infection, leading to biofilm formation and implant loosening. The diagnosis of c. Acnes PJI is difficult, given the slow-growing nature and the lack of a robust inflammatory response. Also, cultures are known to have a high false positive rate. Thus, there is a critical need for reliable peri- or intra-operative tests that determine the presence of c. Acnes infection. We will utilize high-resolution and high-throughput raman spectroscopy to localize and characterize biofilms on implant surfaces associated with c. Acnes and non-c. Acnes infection. Our central hypothesis is that c. Acnes biofilms have a specific chemical composition that can be characterized by their raman signatures and can be rapidly detected on removed implants. We base this hypothesis on our preliminary data showing a characteristic raman signature of various biofilms in laboratory samples and surgical retrievals, as well as prior data showing that biofilms are a common feature of deep c. Acnes and that c. Acnes isolates retrieved from deep sites have higher biofilm-forming capacity. Specific aim 1: to identify characteristic raman signatures associated with biofilms and map their location on retrieved shoulder arthroplasty components with associated positive c. Acnes cultures, other positive cultures, and aseptic failures. Specific aim 2: to build a spectral library of indolent and highly virulent bacteria, their associated biofilms, and other organic species within the periprostatic environment, and a machine learning tool for rapid biofilm identification and speciation. Our research team is ideally suited for this work due to their combined expertise in revision TSA, c. Acnes infection diagnosis, PJI, implant retrieval analysis, high-resolution spectroscopy, machine learning, and the availability of a large implant retrieval collection and clinically relevant isolates. The results of this project will enable same-day diagnosis and, thus, appropriate treatment and better outcomes for the patient.