Introduction Implant infections caused by Staphylococcus aureus are responsible for high mortality and morbidity worldwide. Treatment of these infections can be difficult especially when bacterial biofilms are involved. In this study we investigate the potential of infrared photoimmunotherapy to eradicate staphylococcal infection in a mouse model. Methods A monoclonal antibody that targets Wall Teichoic Acid surface components of both S. aureus and its biofilm (4497-IgG1) was conjugated to a photosensitizer (IRDye700DX) and used as photoimmunotherapy in vitro and in vivo in mice with a subcutaneous implant pre-colonized with biofilm of Staphylococcus aureus. A dose of 400 μg and 200 μg of antibody-photosensitizer conjugate 4497-IgG–IRDye700DXwas administered intravenously to two groups of 5 mice. In addition, multiple control groups (vancomycin treated, unconjugated IRDye700DX and IRDye700DX conjugated to a non-specific antibody) were used to verify anti-microbial effects. Results In vitro results of 4497-IgG-IRDye700DX on pre-colonized (biofilm) implants showed significant (p<0.01) colony-forming units (CFU) reduction at a concentration of 5 μg of the antibody-photosensitizer conjugate. In vivo, treatment with 4497-IgG-IRDye700DX showed no significant CFU reduction at the implant infection. However, tissue around the implant did show a significant CFU reduction with 400 μg 4497-IgG-IRDye700DX compared to control groups (p = 0.037). Conclusion This study demonstrated the antimicrobial potential of photoimmunotherapy for selectively eliminating S. aureus in vivo. However, using a solid implant instead of a catheter could result in an increased bactericidal effect of 4497-IgG-IRDye700DX and administration locally around an implant (per operative) could become valuable applications in patients that are difficult to treat with conventional methods. We conclude that photoimmunotherapy could be a potential additional therapy in the treatment of implant related infections, but requires further improvement.

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Background: Despite the extensive use of silver ions or nanoparticles in research related to preventing implant-associated infections (IAI), their use in clinical practice has been debated. This is because the strong antibacterial properties of silver are counterbalanced by adverse effects on host cells. One of the reasons for this may be the lack of comprehensive in vitro models that are capable of analyzing host-bacteria and host-host interactions. Methods and results: In this study, we tested silver efficacy through multicellular in vitro models involving macrophages (immune system), mesenchymal stem cells (MSCs, bone cells), and S. aureus (pathogen). Our model showed to be capable of identifying each element of culture as well as tracking the intracellular survival of bacteria. Furthermore, the model enabled to find a therapeutic window for silver ions (AgNO3) and silver nanoparticles (AgNPs) where the viability of host cells was not compromised, and the antibacterial properties of silver were maintained. While AgNO3 between 0.00017 and 0.017 µg/mL retained antibacterial properties, host cell viability was not affected. The multicellular model, however, demonstrated that those concentrations had no effect on the survival of S. aureus, inside or outside host cells. Similarly, treatment with 20 nm AgNPs did not influence the phagocytic and killing capacity of macrophages or prevent S. aureus from invading MSCs. Moreover, exposure to 100 nm AgNPs elicited an inflammatory response by host cells as detected by the increased production of TNF-α and IL-6. This was visible only when macrophages and MSCs were cultured together. Conclusions: Multicellular in vitro models such as the one used here that simulate complex in vivo scenarios can be used to screen other therapeutic compounds or antibacterial biomaterials without the need to use animals.@en

Background and purpose — The long-term results of the 1-or 2-stage revision procedure and infection-free prosthesis survival in a tertiary referral center are unknown. In this retrospective observational study, the long-term results of infection control and infection-free prosthesis survival of the peri-prosthetic joint infection-related 1-and 2-stage revision procedure are evaluated. Furthermore, the merits of performing an antibiotic-free window in the 2-stage revision is evaluated. Patients and methods — All patients who received a 1-or 2-stage revision procedure of the hip or knee between 2010 and 2017 were included. Data was collected on patient and infection characteristics. The primary treatment aim was successful infection control without the use of antibiotic therapy afterwards. Infection-free survival analysis was performed using the Kaplan–Meier method with type of periprosthetic joint infection-related revision as covariate. Within the group of 2-stage revisions, use of an antibiotic-free window was selected as covariate. Results — 128 patients were treated for a periprosthetic joint infection-related revision procedure (81 hips and 47 knees). Successful infection control was achieved in 18 of 21 cases for the 1-stage and 89 out of 107 cases for the 2-stage revision procedure (83%) respectively after follow-up of more than 4 years. In addition, 2-stage revision procedure infection control was achieved in 52 of 60 cases with an anti-biotic-free interval and 37 of 45 cases without such interval (p = 0.6). The mean infection-free survival of the 1-stage revision was 90 months (95% CI 75–105) and 98 months (CI 90–106) for the 2-stage revision procedure. Interpretation — There seems to be no difference in infection control and infection-free survival between the 1-and 2-stage revision procedure. Second, an antibiotic-free window in the case of a 2-stage revision did not seem to influence treatment outcome. However, one must be cautious when interpreting these results due to confounding by indication and the small study population. Therefore, no definite conclusion can be drawn.

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Cationic host defense peptides (HDPs) are a promising alternative to antibiotics in the fight against Staphylococcus aureus infections. In this study, we investigated the antibacterial and immunomodulatory properties of three HDPs namely IDR-1018, CATH-2, and LL-37. Although all three HDPs significantly inhibited LPS-induced activation of human macrophages, only CATH-2 prevented S. aureus growth. When applied to different infection models focused on intracellularly surviving bacteria, only IDR-1018 showed a consistent reduction in macrophage bacterial uptake. However, this observation did not correlate with an increase in killing the efficiency of intracellular S. aureus. Here, we conclude that despite the promising antibacterial and anti-inflammatory properties of the selected HDPs, macrophages’ intrinsic antibacterial functions were not improved. Future studies should either focus on combining different HDPs or using them synergistically with other antibacterial agents to improve immune cells’ efficacy against S. aureus pathogenesis.

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Introduction: Debridement, antibiotics and implant retention (DAIR) procedures are effective treatments for acute postoperative or acute hematogenous periprosthetic joint infections. However, literature reporting on the effectiveness of DAIR procedures performed after a one- or two-stage revision because of a prosthetic joint infection (PJI) (PJI-related revision arthroplasty) is scarce. The aim of this study is to retrospectively evaluate the infection control after 1 year of a DAIR procedure in the case of an early postoperative infection either after primary arthroplasty or after PJI-related revision arthroplasty. Materials and methods: All patients treated with a DAIR procedure within 3 months after onset of PJI between 2009 and 2017 were retrospectively included. Data were collected on patient and infection characteristics. All infections were confirmed by applying the Musculoskeletal Infection Society (MSIS) 2014 criteria. The primary outcome was successful control of infection at 1 year after a DAIR procedure, which was defined as the absence of clinical signs, such as pain, swelling, and erythema; radiological signs, such as protheses loosening; or laboratory signs, such as C-reactive protein (CRP) (<10) with no use of antibiotic therapy. Results: Sixty-seven patients were treated with a DAIR procedure (41 hips and 26 knees). Successful infection control rates of a DAIR procedure after primary arthroplasty (n=51) and after prior PJI-related revision arthroplasty (n=16) were 69 % and 56 %, respectively (p=0.38). The successful infection control rates of a DAIR procedure after an early acute infection (n=35) and after a hematogenous infection (n=16) following primary arthroplasty were both 69 % (p=1.00). Conclusion: In this limited study population, no statistically significant difference is found in infection control after 1 year between DAIR procedures after primary arthroplasty and PJI-related revision arthroplasty.

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