Aims. To investigate the efficacy of ethylenediaminetetraacetic acid-normal saline (EDTA-NS) in dispersing biofilms and reducing bacterial infections. Methods. EDTA-NS solutions were irrigated at different durations (1, 5, 10, and 30 minutes) and concentrations (1, 2, 5, 10, and 50 mM) to disrupt Staphylococcus aureus biofilms on Matrigel-coated glass and two materials widely used in orthopaedic implants (Ti-6Al-4V and highly cross-linked polyethylene (HXLPE)). To assess the efficacy of biofilm dispersion, crystal violet staining biofilm assay and colony counting after sonification and culturing were performed. The results were further confirmed and visualized by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). We then investigated the efficacies of EDTA-NS irrigation in vivo in rat and pig models of biofilm-associated infection. Results. When 10 mM or higher EDTA-NS concentrations were used for ten minutes, over 99% of S. aureus biofilm formed on all three types of materials was eradicated in terms of absorbance measured at 595 nm and colony-forming units (CFUs) after culturing. Consistently, SEM and CSLM scanning demonstrated that less adherence of S. aureus could be observed on all three types of materials after 10 mM EDTA-NS irrigation for ten minutes. In the rat model, compared with NS irrigation combined with rifampin (Ti-6Al-4V wire-implanted rats: 60% bacteria survived; HXLPE particle-implanted rats: 63.3% bacteria survived), EDTA-NS irrigation combined with rifampin produced the highest removal rate (Ti-6Al-4V wire-implanted rats: 3.33% bacteria survived; HXLPE particle-implanted rats: 6.67% bacteria survived). In the pig model, compared with NS irrigation combined with rifampin (Ti-6Al-4V plates: 75% bacteria survived; HXLPE bearings: 87.5% bacteria survived), we observed a similar level of biofilm disruption on Ti-6Al-4V plates (25% bacteria survived) and HXLPE bearings (37.5% bacteria survived) after EDTA-NS irrigation combined with rifampin. The in vivo study revealed that the biomass of S. aureus biofilm was significantly reduced when treated with rifampin following irrigation and debridement, as indicated by both the biofilm bacterial burden and crystal violet staining. EDTA-NS irrigation (10 mM/10 min) combined with rifampin effectively removes S. aureus biofilm-associated infections both in vitro and in vivo. Conclusion. EDTA-NS irrigation with or without antibiotics is effective in eradicating S. aureus biofilm-associated infection both ex and in vivo. Cite this article: Bone Joint Res 2024;13(1):40–51

Objectives. Irrigation is the cornerstone of treating skeletal infection by eliminating pathogens in wounds. A previous study shows that irrigation with normal saline (0.9%) and ethylenediaminetetraacetic acid (EDTA) could improve the removal of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) compared with normal saline (NS) alone. However, it is still unclear whether EDTA solution is effective against infection with drug-resistant bacteria. Methods. We established three wound infection models (skin defect, bone-exposed, implant-exposed) by inoculating the wounds with a variety of representative drug-resistant bacteria including methicillin-resistant S. aureus (MRSA), extended spectrum beta-lactamase-producing E. coli (ESBL-EC), multidrug-resistant Pseudomonas aeruginosa (MRPA), vancomycin-resistant Enterococcus (VRE), multidrug-resistant Acinetobacter baumannii (MRAB), multidrug-resistant Enterobacter (MRE), and multidrug-resistant Proteus mirabilis (MRPM). Irrigation and debridement were repeated until the wound culture became negative. The operating times required to eliminate pathogens in wounds were compared through survival analysis. Results. Compared with other groups (NS, castile soap, benzalkonium chloride, and bacitracin), the EDTA group required fewer debridement and irrigation operations to achieve pathogen eradication in all three models of wound infection. Conclusion. Irrigation with EDTA solution was more effective than the other irrigation fluids used in the treatment of wound infections caused by drug-resistant pathogens. Cite this article: Z. Deng, F. Liu, C. Li. Therapeutic effect of ethylenediaminetetraacetic acid irrigation solution against wound infection with drug-resistant bacteria in a rat model: an animal study. Bone Joint Res 2019;8:189–198. DOI: 10.1302/2046-3758.85.BJR-2018-0280.R3

Aims. Bacteriophages infect, replicate inside bacteria, and are released from the host through lysis. Here, we evaluate the effects of repetitive doses of the Staphylococcus aureus phage 191219 and gentamicin against haematogenous and early-stage biofilm implant-related infections in Galleria mellonella. Methods. For the haematogenous infection, G. mellonella larvae were implanted with a Kirschner wire (K-wire), infected with S. aureus, and subsequently phages and/or gentamicin were administered. For the early-stage biofilm implant infection, the K-wires were pre-incubated with S. aureus suspension before implantation. After 24 hours, the larvae received phages and/or gentamicin. In both models, the larvae also received daily doses of phages and/or gentamicin for up to five days. The effect was determined by survival analysis for five days and quantitative culture of bacteria after two days of repetitive doses. Results. In the haematogenous infection, a single combined dose of phages and gentamicin, and repetitive injections with gentamicin or in combination with phages, resulted in significantly improved survival rates. In the early-stage biofilm infection, only repetitive combined administration of phages and gentamicin led to a significantly increased survival. Additionally, a significant reduction in number of bacteria was observed in the larvae after receiving repetitive doses of phages and/or gentamicin in both infection models. Conclusion. Based on our results, a single dose of the combination of phages and gentamicin is sufficient to prevent a haematogenous S. aureus implant-related infection, whereas gentamicin needs to be administered daily for the same effect. To treat early-stage S. aureus implant-related infection, repetitive doses of the combination of phages and gentamicin are required. Cite this article: Bone Joint Res 2024;13(8):383–391

Aims. Arthroplasty surgery of the knee and hip is performed in two to three million patients annually. Periprosthetic joint infections occur in 4% of these patients. Debridement, antibiotics, and implant retention (DAIR) surgery aimed at cleaning the infected prosthesis often fails, subsequently requiring invasive revision of the complete prosthetic reconstruction. Infection-specific imaging may help to guide DAIR. In this study, we evaluated a bacteria-specific hybrid tracer (. 99m. Tc-UBI. 29-41. -Cy5) and its ability to visualize the bacterial load on femoral implants using clinical-grade image guidance methods. Methods. 99m. Tc-UBI. 29-41. -Cy5 specificity for Stapylococcus aureus was assessed in vitro using fluorescence confocal imaging. Topical administration was used to highlight the location of S. aureus cultured on femoral prostheses using fluorescence imaging and freehand single photon emission CT (fhSPECT) scans. Gamma counting and fhSPECT were used to quantify the bacterial load and monitor cleaning with chlorhexidine. Microbiological culturing helped to relate the imaging findings with the number of (remaining) bacteria. Results. Bacteria could be effectively stained in vitro and on prostheses, irrespective of the presence of biofilm. Infected prostheses revealed bacterial presence on the transition zone between the head and neck, and in the screw hole. Qualitative 2D fluorescence images could be complemented with quantitative 3D fhSPECT scans. Despite thorough chlorhexidine treatments, 28% to 44% of the signal remained present in the locations of the infection that were identified using imaging, which included 500 to 2,000 viable bacteria. Conclusion. The hybrid tracer . 99m. Tc-UBI. 29-41. -Cy5 allowed effective bacterial staining. Qualitative real-time fluorescence guidance could be effectively combined with nuclear imaging that enables quantitative monitoring of the effectiveness of cleaning strategies. Cite this article: Bone Joint Res 2023;12(1):72–79

Aims. Biofilm infections are among the most challenging complications in orthopaedics, as bacteria within the biofilms are protected from the host immune system and many antibiotics. Halicin exhibits broad-spectrum activity against many planktonic bacteria, and previous studies have demonstrated that halicin is also effective against Staphylococcus aureus biofilms grown on polystyrene or polypropylene substrates. However, the effectiveness of many antibiotics can be substantially altered depending on which orthopaedically relevant substrates the biofilms grow. This study, therefore, evaluated the activity of halicin against less mature and more mature S. aureus biofilms grown on titanium alloy, cobalt-chrome, ultra-high molecular weight polyethylene (UHMWPE), devitalized muscle, or devitalized bone. Methods. S. aureus-Xen36 biofilms were grown on the various substrates for 24 hours or seven days. Biofilms were incubated with various concentrations of halicin or vancomycin and then allowed to recover without antibiotics. Minimal biofilm eradication concentrations (MBECs) were defined by CFU counting and resazurin reduction assays, and were compared with the planktonic minimal inhibitory concentrations (MICs). Results. Halicin continued to exert significantly (p < 0.01) more antibacterial activity against biofilms grown on all tested orthopaedically relevant substrates than vancomycin, an antibiotic known to be affected by biofilm maturity. For example, halicin MBECs against both less mature and more mature biofilms were ten-fold to 40-fold higher than its MIC. In contrast, vancomycin MBECs against the less mature biofilms were 50-fold to 200-fold higher than its MIC, and 100-fold to 400-fold higher against the more mature biofilms. Conclusion. Halicin is a promising antibiotic that should be tested in animal models of orthopaedic infection. Cite this article: Bone Joint Res 2024;13(3):101–109

Aims. Although low-intensity pulsed ultrasound (LIPUS) combined with disinfectants has been shown to effectively eliminate portions of biofilm in vitro, its efficacy in vivo remains uncertain. Our objective was to assess the antibiofilm potential and safety of LIPUS combined with 0.35% povidone-iodine (PI) in a rat debridement, antibiotics, and implant retention (DAIR) model of periprosthetic joint infection (PJI). Methods. A total of 56 male Sprague-Dawley rats were established in acute PJI models by intra-articular injection of bacteria. The rats were divided into four groups: a Control group, a 0.35% PI group, a LIPUS and saline group, and a LIPUS and 0.35% PI group. All rats underwent DAIR, except for Control, which underwent a sham procedure. General status, serum biochemical markers, weightbearing analysis, radiographs, micro-CT analysis, scanning electron microscopy of the prostheses, microbiological analysis, macroscope, and histopathology evaluation were performed 14 days after DAIR. Results. The group with LIPUS and 0.35% PI exhibited decreased levels of serum biochemical markers, improved weightbearing scores, reduced reactive bone changes, absence of viable bacteria, and decreased inflammation compared to the Control group. Despite the greater antibiofilm activity observed in the PI group compared to the LIPUS and saline group, none of the monotherapies were successful in preventing reactive bone changes or eliminating the infection. Conclusion. In the rat model of PJI treated with DAIR, LIPUS combined with 0.35% PI demonstrated stronger antibiofilm potential than monotherapy, without impairing any local soft-tissue. Cite this article: Bone Joint Res 2024;13(7):332–341

Aims. Bone regeneration during treatment of staphylococcal bone infection is challenging due to the ability of Staphylococcus aureus to invade and persist within osteoblasts. Here, we sought to determine whether the metabolic and extracellular organic matrix formation and mineralization ability of S. aureus-infected human osteoblasts can be restored after rifampicin (RMP) therapy. Methods. The human osteoblast-like Saos-2 cells infected with S. aureus EDCC 5055 strain and treated with 8 µg/ml RMP underwent osteogenic stimulation for up to 21 days. Test groups were Saos-2 cells + S. aureus and Saos-2 cells + S. aureus + 8 µg/ml RMP, and control groups were uninfected untreated Saos-2 cells and uninfected Saos-2 cells + 8 µg/ml RMP. Results. The S. aureus-infected osteoblasts showed a significant number of intracellular bacteria colonies and an unusual higher metabolic activity (p < 0.005) compared to uninfected osteoblasts. Treatment with 8 µg/ml RMP significantly eradicated intracellular bacteria and the metabolic activity was comparable to uninfected groups. The RMP-treated infected osteoblasts revealed a significantly reduced amount of mineralized extracellular matrix (ECM) at seven days osteogenesis relative to uninfected untreated osteoblasts (p = 0.007). Prolonged osteogenesis and RMP treatment at 21 days significantly improved the ECM mineralization level. Ultrastructural images of the mineralized RMP-treated infected osteoblasts revealed viable osteoblasts and densely distributed calcium crystal deposits within the extracellular organic matrix. The expression levels of prominent bone formation genes were comparable to the RMP-treated uninfected osteoblasts. Conclusion. Intracellular S. aureus infection impaired osteoblast metabolism and function. However, treatment with low dosage of RMP eradicated the intracellular S. aureus, enabling extracellular organic matrix formation and mineralization of osteoblasts at later stage. Cite this article: Bone Joint Res 2022;11(5):327–341

Aims

Here we used a mature seven-day biofilm model of Staphylococcus aureus, exposed to antibiotics up to an additional seven days, to establish the effectiveness of either mechanical cleaning or antibiotics or non-contact induction heating, and which combinations could eradicate S. aureus in mature biofilms.

Aims. Periprosthetic joint infections (PJIs) and osteomyelitis are clinical challenges that are difficult to eradicate. Well-characterized large animal models necessary for testing and validating new treatment strategies for these conditions are lacking. The purpose of this study was to develop a rabbit model of chronic PJI in the distal femur. Methods. Fresh suspensions of Staphylococcus aureus (ATCC 25923) were prepared in phosphate-buffered saline (PBS) (1 × 10. 9. colony-forming units (CFUs)/ml). Periprosthetic osteomyelitis in female New Zealand white rabbits was induced by intraosseous injection of planktonic bacterial suspension into a predrilled bone tunnel prior to implant screw placement, examined at five and 28 days (n = 5/group) after surgery, and compared to a control aseptic screw group. Radiographs were obtained weekly, and blood was collected to measure ESR, CRP, and white blood cell (WBC) counts. Bone samples and implanted screws were harvested on day 28, and processed for histological analysis and viability assay of bacteria, respectively. Results. Intraosseous periprosthetic introduction of planktonic bacteria induced an acute rise in ESR and CRP that subsided by day 14, and resulted in radiologically evident periprosthetic osteolysis by day 28 accompanied by elevated WBC counts and histological evidence of bacteria in the bone tunnels after screw removal. The aseptic screw group induced no increase in ESR, and no lysis developed around the implants. Bacterial viability was confirmed by implant sonication fluid culture. Conclusion. Intraosseous periprosthetic introduction of planktonic bacteria reliably induces survivable chronic PJI in rabbits. Cite this article: Bone Joint Res 2021;10(3):156–165

Aims. Biofilm formation is one of the primary reasons for the difficulty in treating implant-related infections (IRIs). Focused high-energy extracorporeal shockwave therapy (fhESWT), which is a treatment modality for fracture nonunions, has been shown to have a direct antibacterial effect on planktonic bacteria. The goal of the present study was to investigate the effect of fhESWT on Staphylococcus aureus biofilms in vitro in the presence and absence of antibiotic agents. Methods. S. aureus biofilms were grown on titanium discs (13 mm × 4 mm) in a bioreactor for 48 hours. Shockwaves were applied with either 250, 500, or 1,000 impulses onto the discs surrounded by either phosphate-buffered saline or antibiotic (rifampin alone or in combination with nafcillin). The number of viable bacteria was determined by quantitative culture after sonication. Representative samples were taken for scanning electron microscopy. Results. The application of fhESWT led to a ten-fold reduction in bacterial counts on the metal discs for all impulse numbers compared to the control (p < 0.001). Increasing the number of impulses did not further reduce bacterial counts in the absence of antibiotics (all p > 0.289). Antibiotics alone reduced the number of bacteria on the discs; however, the combined application of the fhESWT and antibiotic administration further reduced the bacterial count compared to the antibiotic treatment only (p = 0.032). Conclusion. The use of fhESWT significantly reduced the colony-forming unit (CFU) count of a S. aureus biofilm in our model independently, and in combination with antibiotics. Therefore, the supplementary application of fhESWT could be a helpful tool in the treatment of IFIs in certain cases, including infected nonunions. Cite this article: Bone Joint Res 2021;10(1):77–84

Aims. There is a considerable challenge in treating bone infections and orthopaedic device-associated infection (ODAI), partly due to impaired penetration of systemically administrated antibiotics at the site of infection. This may be circumvented by local drug administration. Knowledge of the release kinetics from any carrier material is essential for proper application. Ceftriaxone shows a particular constant release from calcium sulphate (CaSO. 4. ) in vitro, and is particularly effective against streptococci and a large portion of Gram-negative bacteria. We present the clinical release kinetics of ceftriaxone-loaded CaSO. 4. applied locally to treat ODAI. Methods. A total of 30 operations with ceftriaxone-loaded CaSO. 4. had been performed in 28 patients. Ceftriaxone was applied as a single local antibiotic in 21 operations and combined with vancomycin in eight operations, and in an additional operation with vancomycin and amphotericin B. Sampling of wound fluid was performed from drains or aspirations. Ceftriaxone concentrations were measured by liquid chromatography with tandem mass spectrometry (LC-MS/MS). Results. A total of 37 wound fluid concentrations from 16 operations performed in 14 patients were collected. The ceftriaxone concentrations remained approximately within a range of 100 to 200 mg/l up to three weeks. The median concentration was 108.9 mg/l (interquartile range 98.8 to 142.5) within the first ten days. No systemic adverse reactions were observed. Conclusion. Our study highlights new clinical data of locally administered ceftriaxone with CaSO. 4. as carrier material. The near-constant release of ceftriaxone from CaSO. 4. observed in vitro could be confirmed in vivo. The concentrations remained below known local toxicity thresholds. Cite this article: Bone Joint Res 2022;11(11):835–842

Objectives. The purpose of this study was to examine the bactericidal efficacy of hydrogen peroxide (H. 2. O. 2. ) on Cutibacterium acnes (C. acnes). We hypothesize that H. 2. O. 2. reduces the bacterial burden of C. acnes. Methods. The effect of H. 2. O. 2. was assessed by testing bactericidal effect, time course analysis, growth inhibition, and minimum bactericidal concentration. To assess the bactericidal effect, bacteria were treated for 30 minutes with 0%, 1%, 3%, 4%, 6%, 8%, or 10% H. 2. O. 2. in saline or water and compared with 3% topical H. 2. O. 2. solution. For time course analysis, bacteria were treated with water or saline (controls), 3% H. 2. O. 2. in water, 3% H. 2. O. 2. in saline, or 3% topical solution for 5, 10, 15, 20, and 30 minutes. Results were analyzed with a two-way analysis of variance (ANOVA) (p < 0.05). Results. Minimum inhibitory concentration of H. 2. O. 2. after 30 minutes is 1% for H. 2. O. 2. prepared in saline and water. The 3% topical solution was as effective when compared with the 1% H. 2. O. 2. prepared in saline or water. The controls of both saline and water showed no reduction of bacteria. After five minutes of exposure, all mixtures of H. 2. O. 2. reduced the percentage of live bacteria, with the topical solution being most effective (p < 0.0001). Maximum growth inhibition was achieved with topical 3% H. 2. O. 2. . Conclusion. The inexpensive and commercially available topical solution of 3% H. 2. O. 2. demonstrated superior bactericidal effect as observed in the minimum bactericidal inhibitory concentration, time course, and colony-forming unit (CFU) inhibition assays. These results support the use of topical 3% H. 2. O. 2. for five minutes before surgical skin preparation prior to shoulder surgery to achieve eradication of C. acnes for the skin. Cite this article: P. Hernandez, B. Sager, A. Fa, T. Liang, C. Lozano, M. Khazzam. Bactericidal efficacy of hydrogen peroxide on Cutibacterium acnes. Bone Joint Res 2019;8:3–10. DOI: 10.1302/2046-3758.81.BJR-2018-0145.R1

Objectives. Prosthetic joint infection (PJI) is the most common cause of arthroplasty failure. However, infection is often difficult to detect by conventional bacterial cultures, for which false-negative rates are 23% to 35%. In contrast, 16S rRNA metagenomics has been shown to quantitatively detect unculturable, unsuspected, and unviable pathogens. In this study, we investigated the use of 16S rRNA metagenomics for detection of bacterial pathogens in synovial fluid (SF) from patients with hip or knee PJI. Methods. We analyzed the bacterial composition of 22 SF samples collected from 11 patients with PJIs (first- and second-stage surgery). The V3 and V4 region of bacteria was assessed by comparing the taxonomic distribution of the 16S rDNA amplicons with microbiome sequencing analysis. We also compared the results of bacterial detection from different methods including 16S metagenomics, traditional cultures, and targeted Sanger sequencing. Results. Polymicrobial infections were not only detected, but also characterized at different timepoints corresponding to first- and second-stage exchange arthroplasty. Similar taxonomic distributions were obtained by matching sequence data against SILVA, Greengenes, and The National Center for Biotechnology Information (NCBI). All bacteria isolated from the traditional culture could be further identified by 16S metagenomics and targeted Sanger sequencing. Conclusion. The data highlight 16S rRNA metagenomics as a suitable and promising method to detect and identify infecting bacteria, most of which may be uncultivable. Importantly, the method dramatically reduces turnaround time to two days rather than approximately one week for conventional cultures. Cite this article: M-F. Chen, C-H. Chang, C. Chiang-Ni, P-H. Hsieh, H-N. Shih, S. W. N. Ueng, Y. Chang. Rapid analysis of bacterial composition in prosthetic joint infection by 16S rRNA metagenomic sequencing. Bone Joint Res 2019;8:367–377. DOI: 10.1302/2046-3758.88.BJR-2019-0003.R2

Aims. Prompt and sufficient broad-spectrum empirical antibiotic treatment is key to preventing infection following open tibial fractures. Succeeding co-administration, we dynamically assessed the time for which vancomycin and meropenem concentrations were above relevant epidemiological cut-off (ECOFF) minimal inhibitory concentrations (T > MIC) in tibial compartments for the bacteria most frequently encountered in open fractures. Low and high MIC targets were applied: 1 and 4 µg/ml for vancomycin, and 0.125 and 2 µg/ml for meropenem. Methods. Eight pigs received a single dose of 1,000 mg vancomycin and 1,000 mg meropenem simultaneously over 100 minutes and 10 minutes, respectively. Microdialysis catheters were placed for sampling over eight hours in tibial cancellous bone, cortical bone, and adjacent subcutaneous adipose tissue. Venous blood samples were collected as references. Results. Across the targeted ECOFF values, vancomycin displayed longer T > MIC in all the investigated compartments in comparison to meropenem. For both drugs, cortical bone exhibited the shortest T > MIC. For the low MIC targets and across compartments, mean T > MIC ranged between 208 and 449 minutes (46% to 100%) for vancomycin and between 189 and 406 minutes (42% to 90%) for meropenem. For the high MIC targets, mean T > MIC ranged between 30 and 446 minutes (7% to 99%) for vancomycin and between 45 and 181 minutes (10% to 40%) for meropenem. Conclusion. The differences in the T > MIC between the low and high targets illustrate how the interpretation of these results is highly susceptible to the defined MIC target. To encompass any trauma, contamination, or individual tissue differences, a more aggressive dosing approach may be considered to achieve longer T > MIC in all the exposed tissues, and thereby lower the risk of acquiring an infection after open tibial fractures. Cite this article: Bone Joint Res 2022;11(2):112–120

Aims. In wound irrigation, 1 mM ethylenediaminetetraacetic acid (EDTA) is more efficacious than normal saline (NS) in removing bacteria from a contaminated wound. However, the optimal EDTA concentration remains unknown for different animal wound models. Methods. The cell toxicity of different concentrations of EDTA dissolved in NS (EDTA-NS) was assessed by Cell Counting Kit-8 (CCK-8). Various concentrations of EDTA-NS irrigation solution were compared in three female Sprague-Dawley rat models: 1) a skin defect; 2) a bone exposed; and 3) a wound with an intra-articular implant. All three models were contaminated with Staphylococcus aureus or Escherichia coli. EDTA was dissolved at a concentration of 0 (as control), 0.1, 0.5, 1, 2, 5, 10, 50, and 100 mM in sterile NS. Samples were collected from the wounds and cultured. The bacterial culture-positive rate (colony formation) and infection rate (pus formation) of each treatment group were compared after irrigation and debridement. Results. Cell viability intervened below 10 mM concentrations of EDTA-NS showed no cytotoxicity. Concentrations of 1, 2, and 5 mM EDTA-NS had lower rates of infection and positive cultures for S. aureus and E. coli compared with other concentrations in the skin defect model. For the bone exposed model, 0.5, 1, and 2 mM EDTA-NS had lower rates of infection and positive cultures. For intra-articular implant models 10 and 50 mM, EDTA-NS had the lowest rates of infection and positive cultures. Conclusion. The concentrations of EDTA-NS below 10 mM are safe for irrigation. The optimal concentration of EDTA-NS varies by type of wound after experimental inoculation of three types of wound. Cite this article: Bone Joint Res 2021;10(1):68–76

Aims. High-energy injuries can result in multiple complications, the most prevalent being infection. Vancomycin powder has been used with increasing frequency in orthopaedic trauma given its success in reducing infection following spine surgery. Additionally, large, traumatic injuries require wound coverage and management by dressings such as negative pressure wound therapy (NPWT). NPWT has been shown to decrease the ability of antibiotic cement beads to reduce infection, but its effect on antibiotic powder is not known. The goal of this study was to determine if NPWT reduces the efficacy of topically applied antibiotic powder. Methods. Complex musculoskeletal wounds were created in goats and inoculated with a strain of Staphylococcus aureus modified to emit light. Six hours after contaminating the wounds, imaging, irrigation, and debridement and treatment application were performed. Animals received either vancomycin powder with a wound pouch dressing or vancomycin powder with NPWT. Results. There were no differences in eradication of bacteria when vancomycin powder was used in combination with NPWT (4.5% of baseline) compared to vancomycin powder with a wound pouch dressing (1.7% of baseline) (p = 0.986), even though approximately 50% of the vancomycin was recovered in the NPWT exudate canister. Conclusion. The antimicrobial efficacy of the vancomycin powder was not diminished by the application of NPWT. These topical and locally applied therapies are potentially effective tools that can provide quick, simple treatments to prevent infection while providing coverage. By reducing the occurrence of infection, the recovery is shortened, leading to an overall improvement in quality of life. Cite this article: Bone Joint Res 2021;10(2):149–155

Aims. CERAMENT|G is an absorbable gentamicin-loaded biocomposite used as an on-site vehicle of antimicrobials for the treatment of chronic osteomyelitis. The purpose of the present study was to investigate the sole effect of CERAMENT|G, i.e. without additional systemic antimicrobial therapy, in relation to a limited or extensive debridement of osteomyelitis lesions in a porcine model. Methods. Osteomyelitis was induced in nine pigs by inoculation of 10. 4. colony-forming units (CFUs) of Staphylococcus aureus into a drill hole in the right tibia. After one week, the pigs were allocated into three groups. Group A (n = 3) received no treatment during the study period (19 days). Groups B (n = 3) and C (n = 3) received limited or extensive debridement seven days postinoculation, respectively, followed by injection of CERAMENT|G into the bone voids. The pigs were euthanized ten (Group C) and 12 (Group B) days after the intervention. Results. All animals presented confirmatory signs of bone infection post-mortem. The estimated amount of inflammation was substantially greater in Groups A and B compared to Group C. In both Groups B and C, peptide nucleic acid fluorescence in situ hybridization (PNA FISH) of CERAMENT|G and surrounding bone tissue revealed bacteria embedded in an opaque matrix, i.e. within biofilm. In addition, in Group C, the maximal measured post-mortem gentamicin concentrations in CERAMENT|G and surrounding bone tissue samples were 16.6 μg/ml and 6.2 μg/ml, respectively. Conclusion. The present study demonstrates that CERAMENT|G cannot be used as a standalone alternative to extensive debridement or be used without the addition of systemic antimicrobials. Cite this article: Bone Joint Res 2020;9(7):394–401

Aims. To characterize the intracellular penetration of osteoblasts and osteoclasts by methicillin-resistant Staphylococcus aureus (MRSA) and the antibiotic and detergent susceptibility of MRSA in bone. Methods. Time-lapse confocal microscopy was used to analyze the interaction of MRSA strain USA300 with primary murine osteoblasts and osteoclasts. The effects of early and delayed antibiotic treatments on intracellular and extracellular bacterial colony formation and cell death were quantified. We tested the effects of cefazolin, gentamicin, vancomycin, tetracycline, rifampicin, and ampicillin, as well as agents used in surgical preparation and irrigation. Results. MRSA infiltrated bone-resident cells within 15 to 30 minutes. Penetration was most effectively prevented with early (i.e. 30 minutes) antibiotic administration. The combined administration of rifampicin with other antibiotics potentiated their protective effects against MRSA-induced cytotoxicity and most significantly reduced extracellular bacterial bioburden. Gentamicin-containing compounds were most effective in reducing intracellular MRSA bioburden. Of the surgical preparation agents evaluated, betadine reduced in vitro MRSA growth to the greatest extent. Conclusion. The standard of care for open fractures involves debridement and antibiotics within the first six hours of injury but does not account for the window in which bacteria penetrate cells. Antibiotics must be administered as early as possible after injury or prior to incision to prevent intracellular infestation. Rifampicin can potentiate the capacity of antibiotic regimens to reduce MRSA-induced cytotoxicity. Cite this article:Bone Joint Res. 2020;9(2):49–59

Objectives. Preclinical data showed poly(methyl methacrylate) (PMMA) loaded with microsilver to be effective against a variety of bacteria. The purpose of this study was to assess patient safety of PMMA spacers with microsilver in prosthetic hip infections in a prospective cohort study. Methods. A total of 12 patients with prosthetic hip infections were included for a three-stage revision procedure. All patients received either a gentamicin-PMMA spacer (80 g to 160 g PMMA depending on hip joint dimension) with additional loading of 1% (w/w) of microsilver (0.8 g to 1.6 g per spacer) at surgery 1 followed by a gentamicin-PMMA spacer without microsilver at surgery 2 or vice versa. Implantation of the revision prosthesis was carried out at surgery 3. Results. In total, 11 of the 12 patients completed the study. No argyria or considerable differences in laboratory parameters were detected. Silver blood concentrations were below or around the detection limit of 1 ppb in ten of the 11 patients. A maximum of 5.6 ppb at 48 hours after implantation of the silver spacer, which is below the recommended maximum level of 10 ppb, was found in one patient. No silver was detected in the urine. Drainage fluids showed concentrations between 16.1 ppb and 23.3 ppb at 12 hours after implantation of the silver spacers, and between 16.8 ppb to 25.1 ppb at 48 hours after implantation. Pathohistological assessment of the periprosthetic membrane did not reveal any differences between the two groups. Conclusion. Microsilver-loaded gentamicin-PMMA spacers showed good biocompatibility and the broad antimicrobial activity warrants further clinical research to assess its effectivity in reducing infection rates in prosthetic joint infection. Cite this article: V. Alt, M. Rupp, K. Lemberger, T. Bechert, T. Konradt, P. Steinrücke, R. Schnettler, S. Söder, R. Ascherl. Safety assessment of microsilver-loaded poly(methyl methacrylate) (PMMA) cement spacers in patients with prosthetic hip infections: Results of a prospective cohort study. Bone Joint Res 2019;8:387–396. DOI: 10.1302/2046-3758.88.BJR-2018-0270.R1

Aims

Fracture-related infection (FRI) is commonly classified based on the time of onset of symptoms. Early infections (< two weeks) are treated with debridement, antibiotics, and implant retention (DAIR). For late infections (> ten weeks), guidelines recommend implant removal due to tolerant biofilms. For delayed infections (two to ten weeks), recommendations are unclear. In this study we compared infection clearance and bone healing in early and delayed FRI treated with DAIR in a rabbit model.