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Article Differences of Microbial Growth and Biofilm Formation Among Periprosthetic Joint Infection-Causing Species: an Animal Study(Springer Science and Business Media Deutschland GmbH, 2025) Ertan, M.B.; Ayduğan, M.Y.; Evren, E.; İnanç, İ.; Erdemli, E.; Erdemli, B.Purpose: The most frequently used surgical procedures for periprosthetic joint infections (PJIs) are debridement, antibiotics, and implant retention (DAIR), as well as single- or two-stage revision arthroplasty. The choice of surgery is made depending on the full maturation of the biofilm layer. The purpose of this study was to evaluate the biofilm formation and microbial growth using common PJI-causing agents and compare its development on the implant surface. Methods: The in vivo study was performed using 40 Sprague–Dawley rats divided into five groups (n = 8/group): Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Candida albicans, and control. Six standard titanium alloy discs were placed into the subcutaneous air pouches of the interscapular areas of the rats. After the inoculation of microorganisms, disc and soft tissue cultures were collected at 2-week intervals for 6 weeks, and the microbial load and the microscopic appearance of the biofilm were compared. Results: The disc samples from the S. aureus group had the highest infection load at all time points; however, in soft tissue samples, this was only observed at week 4 and 6. Electron microscopic images showed no distinctive differences in the biofilm structures between the groups. Conclusion: S. aureus microbial burden was significantly higher in implant cultures at week 2 compared to other PJI-causing agents examined. These results may explain the higher failure rate seen if the DAIR procedure was performed at < 3–4 weeks after the PJI symptom onset and support the observation that DAIR may not be effective against PJIs caused by S. aureus. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2025.Article Development and In-Vitro Evaluation of Gallium-68 Labelled Staphylococcus Aureus-Specific Aptamer as a Potential PET Agent for Infection Imaging(IJRR-Iranian Journal Radiation Res, 2025) Bargh, S.; Ozkul, C.; Timur, S. S.; Ozalp, V. C.; Erdogan, S.Background: Staphylococcus aureus (S. aureus) is the most common causative pathogen associated with a wide range of infections, from mild to life-threatening conditions such as osteomyelitis, endocarditis, and pneumonia. Early detection and reliable differentiation between infection and sterile inflammation are essential for accurate diagnosis and effective treatment. However, most radiopharmaceuticals currently available fail to discriminate between these conditions, underscoring the need for infection-specific imaging agents. Materials and Methods: In this study, a Gallium-68 (Ga-68)-labeled S. aureus-specific aptamer was developed as a potential PET infection imaging probe. Aptamers were selected using the cell- systematic evolution of ligands by exponential enrichment (SELEX) method, and their specificity was verified by fluorescence-based binding assays. Radiolabeling was achieved via DOTA chelation, and radiochemical purity was determined. Additionally, in vitro binding assays were performed with S. aureus, while Escherichia coli (E. coli) served as a control. Results: The aptamer exhibited an affinity constant (K-a) of 2260 +/- 634 CFU/ mL and a linear detection range of 250-2x10(4) CFU/mL, with a limit of detection of 171 CFU/mL for S. aureus. The Ga-68-labeled aptamer demonstrated radiochemical purity greater than 99%. In vitro binding increased linearly with rising S. aureus concentrations (10(3)-2x10(4) CFU/mL), while minimal binding to E. coli confirmed its specificity. Conclusion: These results demonstrate that the Ga-68-labeled S. aureusspecific aptamer holds promise as an infection-targeted PET imaging agent. Although currently limited to in vitro evaluation, such aptamer-based radiopharmaceuticals may contribute to improved diagnosis and imaging of infectious diseases.
