WHAT IS THE BEST ANTISEPTIC SOLUTION FOR IRRIGATION IN PERIPROSTHETIC JOINT INFECTION? IN VIVO ANALYSIS IN GALLERIA MELLONELLA BIOFILM MODEL

Introduction & Aim Periprosthetic joint infection (PJI) treatment often includes intraoperative irrigation with antiseptic solutions, and their anti-biofilm activity may critically influence outcomes, particularly in the debridement, antibiotics, and implant retention (DAIR) approach. Several commercially available irrigation solutions are used in clinical practice, however, comparative evidence regarding their efficacy against biofilm-associated PJI pathogens remains limited. We compared eight clinically used irrigation and debridement solutions to identify the most effective antiseptic agents and exposure regimens relevant to DAIR, aiming to provide in vivo experimental evidence to support clinical decision-making. Methods Biofilms of Staphylococcus aureus and Pseudomonas aeruginosa were established on titanium Kirschner wires (K-wires) following 72 hours of incubation. The biofilm-colonised implants were subsequently exposed to eight clinically used antiseptic solutions under static conditions for 1, 3, or 15 minutes. Biofilm clearance was quantified by viable bacterial counts after ultrasonic dislodgement. In parallel, a Galleria mellonella larval model was used to assess the in vivo efficacy of each treatment by monitoring post-implantation survival. Scanning electron microscopy (SEM) was employed to visualize structural disruption of biofilms on implant surfaces following antiseptic exposure. Results Povidone-iodine-based antiseptics (Braunol, Betaisodona) showed the highest anti-biofilm activity, eradicating nearly all bacteria even after short (1-3 minute) exposure. Octenidine-based Octenisept and the multi-component solution Bactisure also demonstrated strong biofilm killing, significantly reducing bacterial counts in both assays. In contrast, LAVANOX and Granudacyn exhibited delayed efficacy against S. aureus biofilms, with appreciable effects only after 15 minutes of exposure. Hydrogen peroxide and low-concentration polyhexanide (PHMB) showed minimal biofilm clearance despite prolonged contact. SEM analysis confirmed pronounced structural disruption of S. aureus biofilms following 1 minute of effective antiseptic treatment, whereas P. aeruginosa biofilms were less affected. Conclusions Among the agents tested, povidone-iodine exhibited outstanding biofilm eradication even at brief contact times, while Octenisept and Bactisure were strongly effective but less potent. Hydrogen peroxide and diluted PHMB performed poorly and are not recommended as sole irrigation solutions for DAIR. Importantly, longer contact times (≥15 minutes) significantly enhanced the antimicrobial efficacy of most antiseptics. These findings support the use of potent antiseptics, particularly povidone-iodine-based formulations, as well as Octenisept and Bactisure, provided sufficient dwell time is ensured to maximise infection eradication during DAIR. Acknowledgements The authors acknowledge support from the Chinese Scholarship Council scholarship (202308080110). This research was conducted as part of the HyFiDress consortium, funded by the European Union's Horizon Europe Widening Participation and Spreading Excellence programme under grant agreement 101159615.