Current treatments for biofilm-associated periprosthetic joint infection and new potential strategies

Synergistic antibacterial drug elution from UHMWPE for load-bearing implants

Total joint replacement is a successful procedure for restoring the patient's musculoskeletal mobility and quality of life, but it carries the risk of severe peri-prosthetic joint infections (PJI) and is accompanied by post-operative pain. Cocktails of multiple drugs are often used for prevention/treatment of PJI and for addressing pain. Local drug delivery systems are promising for improving the outcome of the treatment and decreasing the side effects of systemic drugs. To this end, the ultra-high molecular weight polyethylene (UHMWPE) bearing surface of the joint implant is here proposed as a platform for simultaneous release of multiple therapeutics. The combined use of non-antibiotic drugs and antibiotics, and their incorporation into UHMWPE allows to obtain novel antibacterial implant materials. The combined elution of analgesics and antibiotics from UHMWPE is found to be synergistically effective in eradicating Staphylococcus aureus, as the non-antibiotic compound significantly enhances the antibacterial activity of the antibiotic. The drug properties and the employed method for their incorporation into UHMWPE are found to dictate the morphology, thus the mechanical properties of the resulting material. By adopting various fabrication methods, novel formulations showing an enhanced antibacterial activity and outstanding mechanical properties are here proposed to amplify the functionality of polymeric implant materials.

Effect of Antiseptic Irrigation Solutions on Primary Human Knee Fibroblasts Cultured in Human Platelet Lysate

BACKGROUND

Native and periprosthetic joint infections are devastating conditions fraught with patient morbidity and mortality. Aseptic and septic joints are often debrided and irrigated to decrease bacterial loads when preventing or treating infection. However, the effect of clinically used irrigation solutions on the native cellular components of the synovial joint is unknown.

METHODS

Patients consented, and their suprapatellar knee tissue was surgically excised for fibroblast isolation. Cultured knee fibroblasts were treated with normal saline for three minutes or one of the following experimental solutions: acetic acid, chlorhexidine-gluconate, Dakin's solution, hydrogen peroxide, or povidone-iodine. The exposure time for the antiseptic solutions was one and three minutes. At 24 hours after irrigation treatment, metabolic activity was measured via MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium] activity assay, and deoxyribonucleic acid (DNA) content was assessed by Hoechst staining as a surrogate for cell number. Phase-contrast imaging elucidated proliferation potential, progressive cell loss, and cell morphology over a 5-day period. All experiments were repeated in triplicate.

RESULTS

All experimental antiseptic irrigation solutions, regardless of application time, caused a significant reduction in metabolic activity and DNA content, indicating extensive cell death. Phase-contrast imaging showed halted cellular proliferation, progressive cell loss, and distinct changes in cellular morphology, indicating decreased cellular viability and progressive cell death.

CONCLUSIONS

All antiseptic irrigation solutions investigated in this study were severely cytotoxic to human knee fibroblasts regardless of their chemical composition. The concentrations of these solutions are commonly used in orthopaedic surgery. Although these solutions have high bactericidal properties, it may be beneficial to use them in combination at lower doses to retain their effect on bacteria while remaining benign to native synovial cells.

Periprosthetic joint infections: state-of-the-art

In general, periprosthetic joint infection (PJI) is regarded as one of the most common complications of total joint arthroplasty (TJA) and may lead to surgical failure, revision surgery, amputation or death. Nowadays, PJI has become a global health concern, which brings a great burden to public healthcare. In addition, there are still obstacles to achieve high success rates in the prevention, diagnosis and treatment of PJI. However, promising studies are also available with the advancements in biotechnology. This article will present an overview of the current methods used in the prevention, diagnosis and management of PJI while underlining the new technologies utilized.

Investigating the Translational Value of Periprosthetic Joint Infection Models to Determine the Risk and Severity of Staphylococcal Biofilms

With the advent of antibiotic-eluting polymeric materials for targeting recalcitrant infections, using preclinical models to study biofilms are crucial for improving the treatment efficacy in periprosthetic joint infections. The stratification of risk and severity of infections is needed to develop an effective clinical dosing framework with better treatment outcomes. We use in vivo and in vitro implant-associated infection models to demonstrate that methicillin-sensitive and resistant Staphylococcus aureus (MSSA and MRSA) have model-dependent distinct implant and peri-implant tissue colonization patterns. The maturity of biofilms and the location (implant vs tissue) were found to influence the antibiotic susceptibility evolution profiles of MSSA and MRSA, and the models could capture the differing host-microbe interactions in vivo. Gene expression studies revealed the molecular heterogeneity of colonizing bacterial populations. The comparison and stratification of the risk and severity of infection across different preclinical models provided in this study can guide clinical dosing to prevent or treat PJI effectively.

Genomic Insights into Host Susceptibility to Periprosthetic Joint Infections: A Comprehensive Literature Review

Periprosthetic joint infection (PJI) is a multifactorial disease, and the risk of contracting infection is determined by the complex interplays between environmental and host-related factors. While research has shown that certain individuals may have a genetic predisposition for PJI, the existing literature is scarce, and the heterogeneity in the assessed genes limits its clinical applicability. Our review on genetic susceptibility for PJI has the following two objectives: (1) Explore the potential risk of developing PJI based on specific genetic polymorphisms or allelic variations; and (2) Characterize the regulatory cascades involved in the risk of developing PJI. This review focused on clinical studies investigating the association between genetic mutations or variations with the development of PJI. The genes investigated in these studies included toll-like receptors and humoral pattern recognition molecules, cytokines, chemokines, mannose-binding lectin (MBL), bone metabolism molecules, and human leukocyte antigen. Among these genes, polymorphisms in IL-1, MBL, vitamin D receptors, HLA-C, and HLA-DQ might have a relevant impact on the development of PJI. The literature surrounding this topic is limited, but emerging transcriptomic and genome-wide association studies hold promise for identifying at-risk genes. This advancement could pave the way for incorporating genetic testing into preoperative risk stratification, enhancing personalized patient care.

Prevention and Modern Strategies for Managing Methicillin-Resistant Staphylococcal Infections in Prosthetic Joint Infections (PJIs)

Periprosthetic joint infections (PJIs) are a dangerous complication of joint replacement surgeries which have become much more common in recent years (mostly hip and knee replacement surgeries). Such a condition can lead to many health issues and often requires reoperation. Staphylococci is a bacterial group most common in terms of the pathogens causing PJIs. S. aureus and coagulase-negative staphylococci are found in around two-thirds of PJI cases. Recently, the numbers of staphylococci that cause such infections and that are methicillin-resistant are increasing. This trend leads to difficulties in the treatment and prevention of such infections. That is why MRSA and MRSE groups require extraordinary attention when dealing with PJIs in order to successfully treat them. Controlling carriage, using optimal prosthetic materials, and implementing perioperative antimicrobial prophylaxis are crucial strategies in infection prevention and are as essential as quick diagnosis and effective targeted treatment. The comprehensive professional procedures presented in this review show how to deal with such cases.

High-concentration continuous local antibacterial perfusion therapy: safety and potential efficacy for acute and chronic periprosthetic knee joint infection

BACKGROUND

Periprosthetic joint infections (PJIs) following total knee arthroplasty (TKA) are among the most challenging pathologies to manage. Recently, continuous local antibiotic perfusion (CLAP) therapy has been introduced for treating musculoskeletal infections in orthopedics. This study aimed to determine the outcomes and risks of CLAP therapy combined with conventional treatment for PJIs after TKA.

METHODS

We retrospectively evaluated 14 patients with PJIs. For acute PJIs, CLAP therapy was performed alongside debridement, intravenous antibiotics, and implant retention. For chronic PJIs, a two-stage revision with CLAP therapy and intravenous antibiotics was performed. Implants were replaced with a cement mold incorporating CLAP therapy, followed by revision surgery after 3 months. For all patients, 120 mg/day of gentamicin (GM) was locally administered into the knee joint for 2 weeks as part of CLAP therapy, in combination with perioperative intravenous antibiotics.

RESULTS

Five patients developed acute PJIs, and nine developed chronic PJIs after TKA. The mean follow-up period was 18.4 (15.2-21.1) months. All five patients with PJIs treated with one-stage surgery (debridement and insert exchange only) successfully preserved their implants. Among the nine patients with chronic PJIs, seven underwent CLAP therapy combined with two-stage revision surgery, resulting in successful treatment without relapse, whereas the remaining two patients were initially treated with one-stage surgery and CLAP therapy but failed to retain their implants, and subsequently required additional two-stage revision surgery, which ultimately succeeded. No adverse effects from GM were reported.

CONCLUSIONS

Our results suggest that CLAP therapy is safe and may be effective for treating acute and most chronic PJIs after TKA.

Assessment of Bacteriophage Pharmacokinetic Parameters After Intra-Articular Delivery in a Rat Prosthetic Joint Infection Model

Prosthetic joint infections (PJIs) are a serious complication of orthopedic surgery. Bacteriophage (phage) therapy shows promise as an adjunctive treatment but requires further study, particularly in its pharmacokinetics. Consequently, we performed a pharmacokinetic assessment of phage therapy for PJIs using a Staphylococcus epidermidis Kirschner wire-based prosthesis rat model. We used 52 male Sprague-Dawley rats in four groups: negative controls (no phage, sterile implant), PJI controls (bacteria, no phage), sterile phage (phages given, sterile implant), and PJI (bacteria, phages given). The PJI groups were inoculated with ~106 CFU of S. epidermidis. The groups receiving phage were intra-articularly injected with ~108 PFU of vB_SepM_Alex five days post-implantation. The rats were euthanized between 30 min and 48 h post-injection. The measured phage concentrations between the PJI rats and the sterile controls in periarticular tissues were not significantly different. In a noncompartmental pharmacokinetic analysis, the estimated phage half-lives were under 6 h (combined: 3.73 [IQR, 1.45, 10.07]). The maximum phage concentrations were reached within 2 h after administration (combined: 0.75 [0.50, 1.75]). The estimated phage mean residence time was approximately three hours (combined: 3.04 [1.44, 4.19]). Our study provides a preliminary set of pharmacokinetic parameters that can inform future phage dosing studies and animal models of phage therapy for PJIs.

Nanoparticle ultrasonication: a promising approach for reducing bacterial biofilm in total joint infection-an in vivo rat model investigation

BACKGROUND

While the benefits of sonication for improving periprosthetic joint infection (PJI) are well-documented, its potential therapeutic effect against bacterial biofilm remains unstudied. This study aimed to investigate the safety and efficacy of a novel nanoparticle ultrasonication process on methicillin-resistant Staphylococcus aureus (MRSA) bacterial biofilm formation in a PJI rat model.

METHODS

This novel ultrasonication process was designed to remove attached bacterial biofilm from implant and peri-articular tissues, without damaging native tissues or compromising implant integrity. Twenty-five adult Sprague-Dawley rats underwent a surgical procedure and were colonized with intra-articular MRSA, followed by the insertion of a titanium screw. Three weeks after the index surgery, the animals received a second procedure during which the screws were explanted, and soft tissue was sampled. The intraoperative use of the nanoparticle sonication treatment was employed to assess the device's safety, while ex vivo treatment on the retrieved tissue and implants was used to evaluate its efficacy.

RESULTS

Clinical and histological assessments did not indicate any macro- or micro-damage to the host tissue. Sonication of the retrieved tissues demonstrated an average bacterial removal of 2 × 103 CFU/mL and 1 × 104 CFU/gram of tissue. Compared to the standard-of-care group (n = 10), implants treated with sonication (n = 15) had significantly lower remaining bacteria, as indicated by crystal violet absorbance measurements (P = 0.012).

CONCLUSIONS

This study suggests that nanoparticle sonication technology can successfully remove attached bacterial biofilms from explanted orthopedic hardware and the joint capsule, without negatively affecting native tissue. The study provides initial results supporting the potential of nanoparticle sonication as an adjuvant treatment option during a DAIR (debridement, antibiotics, and implant retention) procedure for PJI, paving the way for future clinical trials.

Bacteriophage therapy as an innovative strategy for the treatment of Periprosthetic Joint Infection: a systematic review

BACKGROUND

Periprosthetic Joint Infection (PJI) following hip and knee arthroplasty is a catastrophic complication in orthopaedic surgery. It has long been a key focus for orthopaedic surgeons in terms of prevention and management. With the increasing incidence of antibiotic resistance in recent years, finding more targeted treatment methods has become an increasingly urgent issue. Bacteriophage Therapy (BT) has emerged as a promising adjunctive treatment for bone and joint infections in recent years. It not only effectively kills bacteria but also demonstrates significant anti-biofilm activity, garnering substantial clinical interest due to its demonstrated efficacy and relatively low incidence of adverse effects.

PURPOSE

This review aims to systematically evaluate the efficacy and safety of bacteriophage therapy in treating PJI following hip and knee arthroplasty, providing additional reference for its future clinical application.

METHODS

Following predefined inclusion and exclusion criteria, our team conducted a systematic literature search across seven databases (PubMed, Embase, Web of Science, Cochrane Library, ClinicalTrials.gov, CNKI, and WanFang Database). The search was conducted up to May 2024 and included multiple clinical studies on the use of bacteriophage therapy for treating PJI after hip and knee arthroplasty to assess its efficacy and safety.

RESULTS

This systematic review included 16 clinical studies after screening, consisting of 15 case reports and one prospective controlled clinical trial, involving a total of 42 patients with PJI treated with bacteriophage therapy. The average patient age was 62.86 years, and 43 joints were treated, with patients undergoing an average of 5.25 surgeries. The most common pathogen in these infections was Staphylococcus aureus, accounting for 18 cases. 33 patients received cocktail therapy, while nine were treated with a single bacteriophage preparation. Additionally, all patients underwent suppressive antibiotic therapy (SAT) postoperatively. All patients were followed up for an average of 13.55 months. There were two cases of recurrence, one of which resulted in amputation one year postoperatively. The remaining patients showed good recovery outcomes. Overall, the results from the included studies indicate that bacteriophage therapy effectively eradicates infectious strains in various cases of PJI, with minimal side effects, demonstrating promising clinical efficacy.

CONCLUSION

In the treatment of PJI following hip and knee arthroplasty, bacteriophages, whether used alone or in combination as cocktail therapy, have shown therapeutic potential. However, thorough preoperative evaluation is essential, and appropriate bacteriophage types and treatment regimens must be selected based on bacteriological evidence. Future large-scale, randomized controlled, and prospective trials are necessary to validate the efficacy and safety of this therapy.

Berberine-styrene-co-maleic acid nanomicelles: unlocking opportunities for the treatment and prevention of bacterial infections

The global spread of multi-drug-resistant (MDR) bacteria is rapidly increasing due to antibiotic overuse, posing a major public health threat and causing millions of deaths annually. The present study explored the potential of nanocarriers for delivering novel and alternative antibacterial agents using nanotechnology-based approaches to address the challenge of MDR bacteria. The purpose was to enhance the solubility, stability, and targeted delivery of berberine (BER) and its synthetic derivative NR16 using Styrene-co-Maleic Acid (SMA) nanoparticles. Characterization of the nanoparticles, including dynamic light scattering (DLS) analysis, TEM, and UV/Vis absorption spectroscopy, confirmed their suitability and high stability for passive drug delivery. Antibacterial and antifungal activities were evaluated against a panel of pathogens, revealing significant inhibitory effects on Gram-positive strains; particularly BER, SMA-BER, and NR16 were active against MRSA, MSSA, VR, and VS E. faecalis, and S. epidermidis. Additionally, SMA-BER and SMA-NR16 showed promising activity against biofilm formation of S. epidermidis; while the two free drugs contributed to S. epidermidis biofilm disruption activity. Hemolysis tests and in vitro studies on human embryonic kidney cells (HEK-293) confirmed the safety profiles of the nanoparticles and free drugs. Overall, this research highlighted the potential of nanotechnology in developing effective antibacterial agents with reduced toxicity, addressing the growing threat of MDR bacterial infections.

Napthalimide-based nuclease inhibitor: A multifunctional therapeutic material to bolster MRSA uptake by macrophage-like cells and mitigate pathogen adhesion on orthopaedic implant

The healthcare burden rendered by methicillin-resistant Staphylococcus aureus (MRSA) warrants the development of therapeutics that offer a distinct benefit in the clinics as compared to conventional antibiotics. The present study describes the potential of napthalimide-based synthetic ligands (C1-C3) as inhibitors of the staphylococcal nuclease known as micrococcal nuclease (MNase), a key virulence factor of the pathogen. Amongst the ligands, the most potent MNase inhibitor C1 rendered non-competitive inhibition, reduced MNase turnover number (Kcat) and catalytic efficiency (Kcat/Km) with an IC50 value of ~950 nM. CD spectroscopy suggested distortion of MNase conformation in presence of C1. Flow cytometry and confocal microscopy indicated that C1 restored the ability of activated THP-1 cells to engulf DNA-entrapped MRSA cells. Interestingly, C1 could inhibit MRSA adhesion onto collagen. For potential application, C1-loaded pluronic F-127 micellar nanocarrier (C1-PMC) was generated, wherein the anti-adhesion activity of the pluronic carrier (PMC) and C1 was harnessed in tandem to deter MRSA cell adhesion onto collagen. MRSA biofilm formation was hindered on C1-PMC-coated titanium (Ti) wire, while eluates from C1-PMC-coated Ti wires were non-toxic to HEK 293, MG-63 and THP-1 cells. The multifunctional C1 provides a blueprint for designing therapeutic materials that hold translational potential for mitigation of MRSA infections.

Biofilm Formation in Chronic Infections: A Comprehensive Review of Pathogenesis, Clinical Implications, and Novel Therapeutic Approaches

Biofilms are intricate microbial communities on various surfaces, including medical devices and biological tissues, encased within a protective matrix of extracellular polymeric substances. Their formation and persistence are significant factors in the pathogenesis of chronic infections, contributing to the complexity of treatment and increased resistance to antimicrobial agents. This review explores the multifaceted nature of biofilms, focusing on their formation, structure, and the genetic and environmental factors that contribute to their resilience. Biofilms are particularly problematic in chronic infections, such as those associated with medical implants and persistent wounds, due to their ability to evade both the host immune response and conventional therapeutic strategies. The review also discusses the current challenges in diagnosing biofilm-associated infections and the limitations of existing treatment options. Emerging therapeutic approaches, including novel antibiofilm agents, physical disruption techniques, and biological therapies such as phage therapy, are examined for their potential to improve treatment outcomes. Innovations in drug delivery systems and preventive measures, such as biofilm-resistant materials, are also highlighted as promising developments. This comprehensive overview aims to provide insights into the mechanisms of biofilm-related infections and to guide future research and clinical practice. This review contributes to the ongoing efforts to enhance patient care and combat the growing challenge of antimicrobial resistance by addressing the critical need for effective strategies to manage and prevent biofilm-associated chronic infections.

Eradication of Staphylococcus aureus in Implant-Associated Osteomyelitis by an Injectable In Situ-Forming Depot Antibiotics Delivery System

BACKGROUND

Bone infections with Staphylococcus aureus are notoriously difficult to treat and have high recurrence rates. Local antibiotic delivery systems hold the potential to achieve high in situ antibiotic concentrations, which are otherwise challenging to achieve via systemic administration. Existing solutions have been shown to confer suboptimal drug release and distribution. Here we present and evaluate an injectable in situ-forming depot system termed CarboCell. The CarboCell technology provides sustained and tuneable release of local high-dose antibiotics.

METHODS

CarboCell formulations of levofloxacin or clindamycin with or without antimicrobial adjuvants cis-2-decenoic acid or cis-11-methyl-2-dodecenoic acid were tested in experimental rodent and porcine implant-associated osteomyelitis models. In the porcine models, debridement and treatment with CarboCell-formulated antibiotics was carried out without systemic antibiotic administration. The bacterial burden was determined by quantitative bacteriology.

RESULTS

CarboCell formulations eliminated S. aureus in infected implant rat models. In the translational implant-associated pig model, surgical debridement and injection of clindamycin-releasing CarboCell formulations resulted in pathogen-free bone tissues and implants in 9 of 12 and full eradication in 5 of 12 pigs.

CONCLUSIONS

Sustained release of antimicrobial agents mediated by the CarboCell technology demonstrated promising therapeutic efficacy in challenging translational models and may be beneficial in combination with the current standard of care.

Diagnosis and Treatment of Acute Periprosthetic Infections with the BioFire® System within a Time-Dependent and Bacterium-Dependent Protocol: Review and Prosthesis-Saving Protocol

Despite ongoing efforts to enhance diagnostic and treatment processes, the success rate for eradicating infections, particularly prosthetic joint infections (PJIs), currently stands at around 50%. For acute infections occurring shortly after arthroplasty, guidelines recommend a treatment known as DAIR (debridement, antibiotics, and implant retention). This approach is suggested for infections within 30 days post-arthroplasty or with less than 3 weeks of symptoms, provided that there is a stable implant and adequate soft-tissue mass. Several authors have suggested extending the use of DAIR beyond the initial 3-week period in specific cases. This extension practice seems increasingly feasible due to the rapid diagnostic capabilities offered by BioFire®. This technology allows for quick pathogen identification, aiding in the exclusion of cases that do not fit the criteria for the DAIR/DAPRI (debridement, antibiotic pearls and retention of the implant) protocol based on pathogen identification. The aim of this review is to re-examine the current literature on acute infections and present our proposed "prosthesis-saving" protocol, which integrates the BioFire® molecular diagnostic system. Continued research and assessment of the efficacy and safety of these protocols, especially regarding extended treatment timelines, are crucial for advancing the management of acute infections and enhancing outcomes for PJI patients.

Evaluation of the use of sonication combined with enzymatic treatment for biofilm removal in the microbiological diagnosis of prosthetic joint infection

Sonicating explanted prosthetic implants to physically remove biofilms is a recognized method for improving the microbiological diagnosis of prosthetic joint infection (PJI); however, chemical and enzymatic treatments have been investigated as alternative biofilm removal methods. We compared the biofilm dislodging efficacy of sonication followed by the addition of enzyme cocktails with different activity spectra in the diagnosis of PJI with that of the sonication of fluid cultures alone. Consecutive patients who underwent prosthesis explantation due to infection at our institution were prospectively enrolled for 1 year. The diagnostic procedure included the collection of five intraoperative tissue cultures, sonication of the removed devices, and conventional culture of the sonication fluid. The resulting sonication fluid was also treated with an enzyme cocktail consisting of homemade dispersin B (0.04 µg/mL) and proteinase K (Sigma; 100 µg/mL) for 45 minutes at 37°C. The resulting sonication (S) and sonication with subsequent enzymatic treatment (SE) fluids were plated for aerobic and anaerobic culture broth for 7 days (aerobic) or 14 days (anaerobic). Identification was performed by matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (Bruker). We included 107 patients from whom a prosthetic implant had been removed, among which PJI was diagnosed in 36 (34%). The sensitivity of S alone was significantly greater than that of SE alone (82% vs 71%; P < 0.05). Four patients with PJI were positive after sonication alone but negative after sonication plus enzymatic treatment. The four microorganisms missed after the addition of the enzyme cocktail were Staphylococcus aureus, two coagulase-negative Staphylococci, and Cutibacterium acnes. In conclusion, sonication alone was more sensitive than sonication followed by enzymatic treatment. The combination of these two methods had no synergistic effect; in contrast, the results suggest that the combination of both dislodgment methods affects the viability of gram-positive microorganisms.

IMPORTANCE

While the potential of sonication and enzymes as biofilm dispersal agents has been previously described, the originality of our work resides in the combination of both methods, which is hypothesized to enhance the ability to remove biofilm and, therefore, improve the microbiological diagnosis of PJI.

Advancements in treatment strategies for periprosthetic joint infections: A comprehensive review

Periprosthetic joint infection (PJI) presents a critical challenge in orthopedic care, contributing to significant patient morbidity and healthcare costs. This burden is expected to increase secondary to growing demand for total joint arthroplasty (TJA). Despite the profound significance of PJI, there is currently no universally accepted "gold standard" diagnostic criteria using serum biomarker thresholds; latest criteria fail to differentiate acute infections from chronic or consider time since initial surgery. Furthermore, contemporary PJI treatment, which conventionally requires 2-stage revision surgery in conjunction with rigorous antibiotic treatment, can be particularly taxing on patients. Fortunately, recent years have seen marked evolution in both PJI diagnosis and treatment methods. Contemporary research supports time-dependent serum biomarker thresholds with greater sensitivity and specificity than previously reported, as well as alternative surgical options which may be more suitable for certain patients. The following narrative review aims to describe the significance and pathogenesis of PJI before characterizing current challenges, novel innovations, and the future landscape of PJI diagnosis and management. Here, we spotlight the emerging utility of novel biomarkers and metagenomic next-generation sequencing for diagnosis, advancements in patient-centered surgical outcome prediction tools for PJI risk assessment and prevention, and evolving surgical techniques including 1-stage and a "hybrid" 1.5-stage revision surgeries. Additionally, we explore cutting-edge therapeutic modalities including peptide and bacteriophage-based treatments, intraoperative anti-biofilm gel, the VT-X7 antibiotic pump, and promising immune-based interventions. Ultimately, these advancements hold the potential to revolutionize PJI management, offering hope for improved outcomes and reduced burdens on healthcare systems.

The Mark Coventry Award: PhotothermAA Gel Combined With Debridement, Antibiotics, and Implant Retention Significantly Decreases Implant Biofilm Burden and Soft-Tissue Infection in a Rabbit Model of Knee Periprosthetic Joint Infection

BACKGROUND

Chronic periprosthetic joint infection (PJI) is a major complication of total joint arthroplasty. The underlying pathogenesis often involves the formation of bacterial biofilm that protects the pathogen from both host immune responses and antibiotics. The gold standard treatment requires implant removal, a procedure that carries associated morbidity and mortality risks. Strategies to preserve the implant while treating PJI are desperately needed. Our group has developed an anti-biofilm treatment, PhotothermAA gel, which has shown complete eradication of 2-week-old mature biofilm in vitro. In this study, we tested the anti-biofilm efficacy and safety of PhotothermAA in vivo when combined with debridement, antibiotics and implant retention (DAIR) in a rabbit model of knee PJI.

METHODS

New Zealand white rabbits (n = 21) underwent knee joint arthrotomy, titanium tibial implant insertion, and inoculation with Xen36 (bioluminescent Staphylococcus aureus) after capsule closure. At 2 weeks, rabbits underwent sham surgery (n = 6), DAIR (n = 6), or PhotothermAA with DAIR (n = 9) and were sacrificed 2 weeks later to measure implant biofilm burden, soft-tissue infection, and tissue necrosis.

RESULTS

The combination of anti-biofilm PhotothermAA with DAIR significantly decreased implant biofilm coverage via scanning electron microscopy compared to DAIR alone (1.8 versus 81.0%; P < .0001). Periprosthetic soft-tissue cultures were significantly decreased in the PhotothermAA with DAIR treatment group (log reduction: Sham 1.6, DAIR 2.0, combination 5.6; P < .0001). Treatment-associated necrosis was absent via gross histology of tissue adjacent to the treatment area (P = .715).

CONCLUSIONS

The addition of an anti-biofilm solution like PhotothermAA as a supplement to current treatments that allow implant retention may prove useful in PJI treatment.

Insight into antibacterial effect of titanium nanotubular surfaces with focus on Staphylococcus aureus and Pseudomonas aeruginosa

Materials used for orthopedic implants should not only have physical properties close to those of bones, durability and biocompatibility, but should also exhibit a sufficient degree of antibacterial functionality. Due to its excellent properties, titanium is still a widely used material for production of orthopedic implants, but the unmodified material exhibits poor antibacterial activity. In this work, the physicochemical characteristics, such as chemical composition, crystallinity, wettability, roughness, and release of Ti ions of the titanium surface modified with nanotubular layers were analyzed and its antibacterial activity against two biofilm-forming bacterial strains responsible for prosthetic joint infection (Staphylococcus aureus and Pseudomonas aeruginosa) was investigated. Electrochemical anodization (anodic oxidation) was used to prepare two types of nanotubular arrays with nanotubes differing in dimensions (with diameters of 73 and 118 nm and lengths of 572 and 343 nm, respectively). These two surface types showed similar chemistry, crystallinity, and surface energy. The surface with smaller nanotube diameter (TNT-73) but larger values of roughness parameters was more effective against S. aureus. For P. aeruginosa the sample with a larger nanotube diameter (TNT-118) had better antibacterial effect with proven cell lysis. Antibacterial properties of titanium nanotubular surfaces with potential in implantology, which in our previous work demonstrated a positive effect on the behavior of human gingival fibroblasts, were investigated in terms of surface parameters. The interplay between nanotube diameter and roughness appeared critical for the bacterial fate on nanotubular surfaces. The relationship of nanotube diameter, values of roughness parameters, and other surface properties to bacterial behavior is discussed in detail. The study is believed to shed more light on how nanotubular surface parameters and their interplay affect antibacterial activity.

Pathogens in FRI - Do bugs matter? - An analysis of FRI studies to assess your enemy

Fracture-related infection (FRI) is a devasting complication for both patients and their treating Orthopaedic surgeon that can lead to loss of limb function or even amputation. The unique and unpredictable features of FRI make its diagnosis and treatment a significant challenge. It has substantial morbidity and financial implications for patients, their families and healthcare providers. In this article, we perform an in-depth and comprehensive review of FRI through recent and seminal literature to highlight evolving definitions, diagnostic and treatment approaches, focusing on common pathogens such as Staphylococcus aureus, polymicrobial infections and multi-drug-resistant organisms (MDRO). Furthermore, multiple resistance mechanisms and adaptations for microbial survival are discussed, as well as modern evidence-based medical and surgical advancements in treatment strategies in combating FRI.

Investigating the translational value of Periprosthetic Joint Infection (PJI) models to determine the risk and severity of Staphylococcal biofilms

With the advent of antibiotic-eluting polymeric materials for targeting recalcitrant infections, using preclinical models to study biofilm is crucial for improving the treatment efficacy in periprosthetic joint infections. The stratification of risk and severity of infections is needed to develop an effective clinical dosing framework with better outcomes. Here, using in-vivo and in-vitro implant-associated infection models, we demonstrate that methicillin-sensitive and resistant Staphylococcus aureus (MSSA and MRSA) have model-dependent distinct implant and peri-implant tissue colonization patterns. The maturity of biofilms and the location (implant vs tissue) were found to influence the antibiotic susceptibility evolution profiles of MSSA and MRSA and the models could capture the differing host-microbe interactions in vivo. Gene expression studies revealed the molecular heterogeneity of colonizing bacterial populations. The comparison and stratification of the risk and severity of infection across different preclinical models provided in this study can guide clinical dosing to effectively prevent or treat PJI.

Innovations in the Isolation and Treatment of Biofilms in Periprosthetic Joint Infection: A Comprehensive Review of Current and Emerging Therapies in Bone and Joint Infection Management

Periprosthetic joint infections (PJIs) are a devastating complication of joint arthroplasty surgeries that are often complicated by biofilm formation. The development of biofilms makes PJI treatment challenging as they create a barrier against antibiotics and host immune responses. This review article provides an overview of the current understanding of biofilm formation, factors that contribute to their production, and the most common organisms involved in this process. This article focuses on the identification of biofilms, as well as current methodologies and emerging therapies in the management of biofilms in PJI.

Biofilm and How It Relates to Prosthetic Joint Infection

Prosthetic joint infection following total joint arthroplasty is a devastating complication, resulting in increased morbidity and mortality for the patient. The formation of a biofilm on implanted hardware contributes to the difficulty in successful identification and eradication of the infection. Antibiotic therapy and surgical intervention are necessary for addressing this condition; we present a discussion on different treatment options, including those that are not yet routinely utilized in the clinical setting or are under investigation, to highlight the present and future of PJI management.

Synergistic use of anti-inflammatory ketorolac and gentamicin to target staphylococcal biofilms

BACKGROUND

While antibiotics remain our primary tools against microbial infection, increasing antibiotic resistance (inherent and acquired) is a major detriment to their efficacy. A practical approach to maintaining or reversing the efficacy of antibiotics is the use of other commonly used therapeutics, which show synergistic antibacterial action with antibiotics. Here, we investigated the extent of antibacterial synergy between the antibiotic gentamicin and the anti-inflammatory ketorolac regarding the dynamics of biofilm growth, the rate of acquired resistance, and the possible mechanism of synergy.

METHODS

Control (ATCC 12600, ATCC 35984) and clinical strains (L1101, L1116) of Staphylococcus aureus and Staphylococcus epidermidis with varying antibiotic susceptibility profiles were used in this study to simulate implant-material associated low-risk and high-risk biofilms in vitro. The synergistic action of gentamicin sulfate (GS) and ketorolac tromethamine (KT), against planktonic staphylococcal strains were determined using the fractional inhibitory concentration measurement assay. Nascent (6 h) and established (24 h) biofilms were grown on 316L stainless steel plates and the synergistic biofilm eradication activity was determined and characterized using adherent bacteria count, minimum biofilm eradication concentration (MBEC) measurement for GS, visualization by live/dead imaging, scanning electron microscopy, gene expression of biofilm-associated genes, and bacterial membrane fluidity assessment.

RESULTS

Gentamicin-ketorolac (GS-KT) combination demonstrated synergistic antibacterial action against planktonic Staphylococci. Control and clinical strains showed distinct biofilm growth dynamics and an increase in biofilm maturity was shown to confer further resistance to gentamicin for both 'low-risk' and 'high-risk' biofilms. The addition of ketorolac enhanced the antibiofilm activity of gentamicin against acquired resistance in staphylococcal biofilms. Mechanistic studies revealed that the synergistic action of gentamicin-ketorolac interferes with biofilm morphology and subverts bacterial stress response altering bacterial physiology, membrane dynamics, and biofilm properties.

CONCLUSION

The results of this study have a significant impact on the local administration of antibiotics and other therapeutic agents commonly used in the prevention and treatment of orthopaedic infections. Further, these results warrant the study of synergy for the concurrent or sequential administration of non-antibiotic drugs for antimicrobial effect.

Periprosthetic joint infection and immunity: Current understanding of host-microbe interplay

Periprosthetic joint infection (PJI) is a major complication of total joint arthroplasty. Even with current treatments, failure rates are unacceptably high with a 5-year mortality rate of 26%. Majority of the literature in the field has focused on development of better biomarkers for diagnostics and treatment strategies including innovate antibiotic delivery systems, antibiofilm agents, and bacteriophages. Nevertheless, the role of the immune system, our first line of defense during PJI, is not well understood. Evidence of infection in PJI patients is found within circulation, synovial fluid, and tissue and include numerous cytokines, metabolites, antimicrobial peptides, and soluble receptors that are part of the PJI diagnosis workup. Macrophages, neutrophils, and myeloid-derived suppressor cells (MDSCs) are initially recruited into the joint by chemokines and cytokines produced by immune cells and bacteria and are activated by pathogen-associated molecular patterns. While these cells are efficient killers of planktonic bacteria by phagocytosis, opsonization, degranulation, and recruitment of adaptive immune cells, biofilm-associated bacteria are troublesome. Biofilm is not only a physical barrier for the immune system but also elicits effector functions. Additionally, bacteria have developed mechanisms to evade the immune system by inactivating effector molecules, promoting killing or anti-inflammatory effector cell phenotypes, and intracellular persistence and dissemination. Understanding these shortcomings and the mechanisms by which bacteria can subvert the immune system may open new approaches to better prepare our own immune system to combat PJI. Furthermore, preoperative immune system assessment and screening for dysregulation may aid in developing preventative interventions to decrease PJI incidence.

Synergistic use of anti-inflammatory ketorolac and gentamicin to target staphylococcal biofilms

Background

While antibiotics remain our primary tools against microbial infection, increasing antibiotic resistance (inherent and acquired) is a major detriment to their efficacy. A practical approach to maintaining or reversing the efficacy of antibiotics is the use of other commonly used therapeutics, which show synergistic antibacterial action with antibiotics. Here, we investigated the extent of antibacterial synergy between the antibiotic gentamicin and the anti-inflammatory ketorolac regarding the dynamics of biofilm growth, the rate of acquired resistance, and the possible mechanism of synergy.

Methods

Control (ATCC 12600, ATCC 35984) and clinical strains (L1101, L1116) of S. aureus and S. epidermidis with varying antibiotic susceptibility profiles were used in this study to simulate implant-material associated low-risk and high-risk biofilms in vitro. The synergistic action of gentamicin sulfate (GS) and ketorolac tromethamine (KT), against planktonic staphylococcal strains were determined using the fractional inhibitory concentration measurement assay. Nascent (6hr) and established (24hr) biofilms were grown on 316 stainless steel plates and the synergistic biofilm eradication activity was determined and characterized using adherent bacteria count, MBEC measurement for GS, gene expression of biofilm-associated genes, visualization by live/dead imaging, scanning electron microscopy, and bacterial membrane fluidity assessment.

Results

Gentamicin-ketorolac combination demonstrated synergistic antibacterial action against planktonic Staphylococci. Control and clinical strains showed distinct biofilm growth dynamics and an increase in biofilm maturity was shown to confer further resistance to gentamicin for both 'low-risk' and 'high-risk' biofilms. The addition of ketorolac enhanced the antibiofilm activity of gentamicin against acquired resistance in staphylococcal biofilms. Mechanistic studies revealed that the synergistic action of gentamicin-ketorolac interferes with biofilm morphology and subverts bacterial stress response altering bacterial physiology, membrane dynamics, and biofilm properties.

Conclusion

The results of this study have a significant impact on the local administration of antibiotics and other therapeutic agents commonly used in the prevention and treatment of orthopaedic infections. Further, these results warrant the study of synergy for the concurrent or sequential administration of non-antibiotic drugs for antimicrobial effect.

Mitigating Concerns Over Transport Delays: An Analysis of Synovial Fluid Culture Results in Arthroplasty

INTRODUCTION

 There is a concern in the field of arthroplasty that synovial fluid transport delays may reduce the accuracy of synovial fluid culture. However, synovial fluid samples collected in the office, and sometimes in a hospital setting, often require transport to a third-party central or specialty laboratory, causing delays in the initiation of culture incubation. This study investigated the impact of transportation delays on synovial fluid culture results.

METHODS

 A retrospective review of prospectively collected data at one clinical laboratory, from 2016 to 2022, was conducted. A total of 125,270 synovial fluid samples from knee arthroplasties, from 2,858 different US institutions, were transported to a single clinical laboratory for diagnostic testing including synovial fluid culture (blood culture bottles). Synovial fluid to be cultured was transported in red top tubes without additives. Samples were grouped into six-time cohorts based on the number of days between aspiration and culture initiation (1-day-delay to 6-day-delay). Metrics such as culture positivity, false-positive culture rate, culture sensitivity, and proportional growth of top genera of organisms were assessed across the cohorts.

RESULTS

 Of the 125,270 samples in this study, 71.2% were received the day after aspiration (1-day-delay), with an exponential decrease in samples received on each subsequent day. Culture-positive rates for synovial fluid samples received after 1, 2, 3, 4, 5, and 6 days of transport time were 12.2%, 13.3%, 13.5%, 13.1%, 11.6%, and 11.0%, respectively. The maximum absolute difference in culture-positive rate compared to the 1-day-delay cohort was an increase of 1.3% in the 3-day-delay cohort, which was not considered a clinically meaningful difference. The estimated false-positive culture rate remained relatively consistent across time cohorts, with values of 0.3%, 0.4%, 0.3%, 0.2%, 0.5%, and 0.5% for 1, 2, 3, 4, 5, and 6 days of transport time, respectively. None of the cohorts showed a statistically significant difference after adjustment for multiplicity compared to the 1-day-delay cohort. Culture sensitivity was estimated at 68.2%, 67.2%, 70.5%, 70.7%, 65.9%, and 70.7% for 1, 2, 3, 4, 5, and 6 days of transport time, respectively. None of the cohorts showed a statistically significant difference after adjustment for multiplicity compared to the 1-day-delay cohort. Organism proportions were consistent across time cohorts, with Staphylococcus being the most commonly identified organism. No statistically significant differences were found in the proportional contribution of major genera across the cohorts.

CONCLUSIONS

 Synovial fluid culture exhibited surprisingly consistent results despite variable transport time to the destination laboratory, with differences that have minimal clinical importance. While the authors of this study advocate for short transport times as a best practice to expedite diagnosis, it appears that concerns regarding the rapid degradation of culture results due to synovial fluid transportation is unwarranted.

Interactions between Macrophages and Biofilm during Staphylococcus aureus-Associated Implant Infection: Difficulties and Solutions

Staphylococcus aureus (S. aureus) biofilm is the major cause of failure of implant infection treatment that results in heavy social and economic burden on individuals, families, and communities. Planktonic S. aureus attaches to medical implant surfaces where it proliferates and is wrapped by extracellular polymeric substances, forming a solid and complex biofilm. This provides a stable environment for bacterial growth, infection maintenance, and diffusion and protects the bacteria from antimicrobial agents and the immune system of the host. Macrophages are an important component of the innate immune system and resist pathogen invasion and infection through phagocytosis, antigen presentation, and cytokine secretion. The persistence, spread, or clearance of infection is determined by interplay between macrophages and S. aureus in the implant infection microenvironment. In this review, we discuss the interactions between S. aureus biofilm and macrophages, including the effects of biofilm-related bacteria on the macrophage immune response, roles of myeloid-derived suppressor cells during biofilm infection, regulation of immune cell metabolic patterns by the biofilm environment, and immune evasion strategies adopted by the biofilm against macrophages. Finally, we summarize the current methods that support macrophage-mediated removal of biofilms and emphasize the importance of considering multi-dimensions and factors related to implant-associated infection such as immunity, metabolism, the host, and the pathogen when developing new treatments.

Analysis of the clinical efficacy of two-stage revision surgery in the treatment of periprosthetic joint infection in the knee: A retrospective study

BACKGROUND

Periprosthetic joint infection (PJI) is a catastrophic complication that can occur following total knee arthroplasty (TKA). Currently, the treatment for PJI mainly includes the use of antibiotics alone, prosthetic debridement lavage, primary revision, secondary revision, joint fusion, amputation, etc.

AIM

To explore the clinical effect of two-stage revision surgery for the treatment of PJI after TKA.

METHODS

The clinical data of 27 patients (3 males and 24 females; age range, 47–80 years; mean age, 66.7 ± 8.0 years; 27 knees) with PJI treated with two-stage revision surgery in our hospital between January 1, 2010 and December 31, 2020 were analyzed retrospectively. The following outcomes were compared for changes between preoperative and last follow-up results: Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), visual analogue scale (VAS) scores, Hospital for Special Surgery (HSS) scores, knee range of motion (ROM), and infection cure rates.

RESULTS

All 27 patients were followed up (range, 13–112 mo). The ESR (14.5 ± 6.3 mm/h) and CRP (0.6 ± 0.4 mg/dL) of the patients at the last follow-up were significantly lower than those at admission; the difference was statistically significant (P < 0.001). The postoperative VAS score (1.1 ± 0.7), HSS score (82.3 ± 7.1), and knee ROM (108.0° ± 19.7°) were significantly improved compared with those before the surgery; the difference was statistically significant (P < 0.001). Of the 27 patients, 26 were cured of the infection, whereas 1 case had an infection recurrence; the infection control rate was 96.3%.

CONCLUSION

Two-stage revision surgery can effectively relieve pain, control infection, and retain good joint function in the treatment of PJI after TKA.

A review of current practices in periprosthetic joint infection debridement and revision arthroplasty

BACKGROUND

Periprosthetic joint infection remains a significant challenge for arthroplasty surgeons globally. Over the last few decades, there has been much advancement in terms of treatment and diagnosis, however, the fight rages on. As management of periprosthetic joint infections continues to evolve, it is critical to reflect back on current debridement practices to establish common ground as well as identify areas for future research and improvement. BODY: In order to understand the debridement techniques of periprosthetic joint infections, one must also understand how to diagnose a periprosthetic joint infection. Multiple definitions have been elucidated over the years with no single consensus established but rather sets of criteria. Once a diagnosis has been established the decision of debridement method becomes whether to proceed with single vs two-stage revision based on the probability of infection as well as individual patient factors. After much study, two-stage revision has emerged as the gold standard in the management of periprosthetic infections but single-stage remains prominent with further and further research.

CONCLUSION

Despite decades of data, there is no single treatment algorithm for periprosthetic joint infections and subsequent debridement technique. Our review touches on the goals of debridement while providing a perspective as to diagnosis and the particulars of how intraoperative factors such as intraarticular irrigation can play pivotal roles in infection eradication. By providing a perspective on current debridement practices, we hope to encourage future study and debate on how to address periprosthetic joint infections best.