Optical coherence tomography-based detection of orthopaedic implant biofilms formed by methicillin-resistant S.aureus (MRSA).

Orthopaedic implant-associated infections cause serious complications primarily attributed to bacterial biofilm formation and often characterized by increased antibiotic resistance and diminished treatment response. There is currently a lack of imaging modalities that can directly visualize biofilms to determine the location and extent of contamination. Optical coherence tomography (OCT) is a portable, non-invasive, high-resolution imaging modality with the potential to fulfill this unmet need. In this study, we aim to evaluate the efficacy of OCT in detecting biofilms formed by life- and limb-threatening bacteria on orthopaedic implants. Bioluminescent strain SAP231 of methicillin-resistant S.aureus (MRSA) was used to grow biofilms on the surfaces of titanium and stainless-steel orthopaedic hardware situated inside custom-designed macrofluidic devices, allowing continuous nutrient broth supply and waste removal. Three-dimensional OCT images of each piece of hardware were obtained every 24 hours with subsequent bioluminescence imaging using the PerkinElmer IVIS Spectrum. OCT texture analysis based on multi-parametric fitting approach was developed and validated against IVIS quantification for accurate identification of live MRSA signatures. The monitoring of biofilm formation and measurement of film thicknesses starting at 12 micrometers and reaching 180 micrometers in 72 hours on metal hardware is demonstrated. This proof-of-concept study highlights the ability of OCT to detect and quantify the formation of MRSA bacterial biofilms in a high fidelity orthopaedic implant biofilm model