26dkou551 10.3205/26dkou551 urn:nbn:de:0183-26dkou5515 Meeting Abstract Mannala Mannala Gopala Krishna GK

Department of Trauma Surgery, University Hospital Regensburg, Regensburg, Deutschland

author Riool Riool Martijn M

Department of Trauma Surgery, University Hospital Regensburg, Regensburg, Deutschland

author Alt Alt Volker V

Department of Trauma Surgery, University Hospital Regensburg, Regensburg, Deutschland

author German Medical Science GMS Publishing House

Düsseldorf

610 20261020 engl This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 License. Dieser Artikel ist ein Open-Access-Artikel und steht unter den Lizenzbedingungen der Creative Commons Attribution 4.0 License (Namensnennung). M0659 551 Deutsche Gesellschaft für Orthopädie und Unfallchirurgie Deutsche Gesellschaft für Orthopädie und Orthopädische Chirurgie Deutsche Gesellschaft für Unfallchirurgie Berufsverband für Orthopädie und Unfallchirurgie Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2026) Poster experimentell | Arthrose und Infektion Berlin 20261020 20261023 DKOU26_Abs_2166 TextObjectives and questions: Orthopaedic devices are extensively used for fracture fixation and total joint arthroplasty. Despite their widespread application, the surfaces of these devices are frequently colonized by various bacteria, leading to biofilm formation, and limited efficacy of antibiotic treatments. Staphylococcus aureus is a predominant cause of implant-associated bone infections, characterized by biofilm formation on implant surfaces and internalization into osteoblasts. Bacteriophages (‘phages’) are viruses that infect and replicate within bacteria and ultimately cause bacterial lysis. Calcium (Ca2+) and magnesium (Mg2+) ions play crucial roles in various physiological processes, including bone health, muscle function, and nerve transmission. It is known that Ca2+ and Mg2+ ions can influence phage adsorption and replication by affecting phage infectivity, bacterial-phage interactions, and viral-mediated mineral precipitation. This study aims to assess the role of Ca2+ and Mg2+ in phage therapy against S. aureus clinical isolates in both planktonic and biofilm states, using in vitro and in vivo models.Material and methods: In this study, STAPH bacteriophages obtained from the ELIAVA Institute (Georgia) were used. Phage activity was evaluated using the standard double-layer agar method in the presence of Ca2+, Mg2+, or both divalent ions. The effects of STAPH phages on S. aureus growth curves were analysed in the presence of Ca2+ or Mg2+ ions. In addition, the role of these ions in phage adsorption and biofilm eradication was evaluated. Finally, the therapeutic efficacy of STAPH phages against S. aureus infection was assessed using a Galleria mellonella infection model in the presence of divalent cations.Results: The results showed that STAPH phages exhibited higher bactericidal efficiency against S. aureus, with more than a 1-log increase in plaque-forming units (PFUs) in the presence of Ca2+ or Mg2+ ions. Both ions enhanced phage adsorption to bacterial cell wall, which might be due strong binding to receptors, resulting in increased PFU counts. STAPH phages combined with Ca2+ or Mg2+ ions also demonstrated biofilm reduction. In vivo experiments showed improved larval survival in the presence of STAPH phages supplemented with Mg2+ ions against S. aureus infection in G. mellonella.Discussion and conclusions: Our results demonstrate that supplementation with Ca2+ or Mg2+ ions enhances STAPH phage efficacy by increasing phage adsorption and PFU formation. Mg2+ supplementation significantly improved larval survival in vivo compared with control groups. These findings suggest that addition of divalent metal ions could enhance bacteriophage efficacy and support their potential application in clinical settings for implant-associated infections. 0 0 0 0