Current concepts in pathogenesis of acute and chronic osteomyelitis

A Bacterial Capturing, Neural Network-Like Carbon Nanotubes/Prussian Blue/Puerarin Nanocomposite for Microwave Treatment of Staphylococcus Aureus-Infected Osteomyelitis

Staphylococcus aureus (S. aureus)-infected osteomyelitis is a deep tissue infection that cannot be effectively treated with antibiotics. Microwave (MW) thermal therapy (MTT) and MW dynamic therapy (MDT) based on MW-responsive materials are promising for the therapy of bacteria-infected osteomyelitis occurring in deep tissues that cannot be effectively treated with antibiotics. In this work, the MW-responsive system of carbon nanotubes (CNTs)/Prussian blue (PB)/puerarin (Pue) with stable network-like structures is constructed. The PB is grown in situ on the CNTs, and its introduction not only reduces the aggregation of the network-like structures of the CNTs, but the large specific surface area and mesoporous structure can also provide many active sites for the adsorption of oxygen and polar molecules. Pue is a natural anti-inflammatory material that reduces inflammation at the infection site. The composite of the CNTs and PB avoids the skin effect and thus can improve dielectric and reflection losses. The MW thermal response of CNTs/PB/Pue is mainly due to the occurrence of reflection loss, dielectric loss, multiple reflections and scattering, interface polarization, and dipole polarization. In addition, under MW irradiation, the CNTs/PB/Pue can produce reactive oxygen species (ROS), such as singlet oxygen (1O2), hydroxyl radical (·OH).

Ilizarov External Fixator Versus Orthofix LRS in Management of Femoral Osteomyelitis: A Propensity Score Matched Analysis

Purpose

Treatment of osteomyelitis (OM) is challenging. Ilizarov bone transport is a commonly used technique for management of OM. The recently introduced limb reconstruction system (LRS) has been effectively used for management of OM. It was suggested to be easier in use and less invasive. The present retrospective study aimed to compare LRS and Ilizarov bone transport in management of femoral OM using a propensity score matched analysis.

Methods

The present retrospective study included 80 consecutive patients with femoral OM. The studied patients were managed either using Ilizarov external fixator (n = 40) or Orthofix LRS (n = 40). The clinical outcome measurements included union time, limb length discrepancy, additional operative procedures, refracture and infection.

Results

Patients in the LRS group were exposed to significantly higher frequency of bone transport (30.0 versus 15.0%) and lower frequency of acute compression and lengthening (10.0 versus 32.5%). Patients in Ilizarov group had significantly higher frequency of tobramycin pellets as compared to their counterparts. The studied groups were comparable regarding the operative complications including pin-tract infection, non-union at docking site and refracture. Patients in the Ilizarov had significantly shorter time to union (8.2 ± 3.2 versus 11.0 ± 5.6 months, p = 0.012). No statistically significant differences were found between the studied groups regarding the quality-of-life domains.

Conclusions

Use of Ilizarov external fixator and Orthofix LRS devices proved to be effective and reliable. Their influences on patients' quality appear to be comparable.

Nicotine promotes Staphylococcus aureus-induced osteomyelitis by activating the Nrf2/Slc7a11 signaling axis

Although smoking is a significant risk factor for osteomyelitis, there is limited experimental evidence that nicotine, a key tobacco constituent, is associated with this condition, leaving its mechanistic implications uncharacterized. This study revealed that nicotine promotes Staphylococcus aureus-induced osteomyelitis by increasing Nrf2 and Slc7a11 expression in vivo and in vitro. Inhibition of Slc7a11 using Erastin augmented bacterial phagocytosis/killing capabilities and fortified antimicrobial responses in an osteomyelitis model. Moreover, untargeted metabolomic analysis demonstrated that Erastin mitigated the effects of nicotine on S. aureus-induced osteomyelitis by altering glutamate/glutathione metabolism. These findings suggest that nicotine aggravates S. aureus-induced osteomyelitis by activating the Nrf2/Slc7a11 signaling pathway and that Slc7a11 inhibition can counteract the detrimental health effects of nicotine.

Examining the causal relationship between circulating immune cells and the susceptibility to osteomyelitis: A Mendelian randomization study

BACKGROUND

Osteomyelitis is considered as a deleterious inflammatory condition affecting the bone, primarily attributed to pathogenic infection. However, the underlying factors predisposing individuals to osteomyelitis remain incompletely elucidated. The immune system plays a multifaceted role in the progression of this condition, yet previous observational studies and randomized controlled trials investigating the association between circulating immune cell counts and osteomyelitis have been constrained. In order to address this knowledge gap, we conducted a Mendelian randomization (MR) analysis to evaluate the impact of diverse immune cell counts on the risk of developing osteomyelitis.

METHODS

In our study, we utilized single nucleotide polymorphisms (SNPs) that have been strongly linked to circulating immune cells or specific lymphocyte subtypes, as identified in large-scale genome-wide association studies (GWAS). These SNPs served as instrumental variables (IVs) for our MR analysis. We employed a more relaxed clumping threshold to conduct MR analysis on several related lymphocyte subtypes. To estimate causal effects, we utilized the Wald ratio, as well as the random-effects inverse variance weighted (IVW) and weighted median (WM) methods. To enhance the credibility of our results, we performed F-statistic calculations and a series of sensitivity analyses.

RESULTS

Our findings revealed a significant correlation between the absolute count of circulating lymphocytes and the risk of osteomyelitis [odds ratio(OR) 1.20；95 % confidence interval (CI), 1.08-1.32；P = 0.0005]. Furthermore, we identified a causal relationship between the absolute count of CD8+ T cells and susceptibility to osteomyelitis (OR 1.16; 95 % CI, 1.04-1.30; P = 0.0098). Importantly, these findings remained robust across a wide range of sensitivity analyses.

CONCLUSION

Through our MR analysis, we have provided evidence supporting a causal relationship between genetic predisposition to higher circulating immune cell counts and an increased risk of osteomyelitis. Specifically, our findings highlight the association between elevated CD8+ T cell counts and a heightened susceptibility to osteomyelitis. These results offer valuable insights for the future exploration of immunotherapy approaches in the management of osteomyelitis.

The "Lumpy Jaw" Disease-Treatment and Diagnostical Challenge of Actinomycotic Osteomyelitis

Background

Osteomyelitis is a serious entity that can occur in many different locations. Especially in the mandible, osteomyelitis can show different clinical courses, which differ clearly from other anatomical regions in terms of severity and treatment. Osteomyelitis in the mandible is often caused by mixed species of the oral cavity. A species causing subacute/chronic osteomyelitis can be actinomyces. Actinomycotic osteomyelitis of the jaw represents a diagnostic and treatment challenging disease.

Conclusion

This article describes our perspective on the therapy pillars treating actinomycotic osteomyelitis. The rapid introduction of the two therapeutic elements (antibiosis/surgical therapy) is crucial regarding the outcome of this entity.

FRZB affects Staphylococcus aureus‑induced osteomyelitis in human bone marrow derived stem cells by regulating the Wnt/β‑catenin signaling pathway

Osteomyelitis is an infectious disease of bone tissue caused by bacterial infection, which can infect through hematogenous, traumatic or secondary ways and then lead to acute or chronic bone injury and relative clinical symptoms, bringing physical injury and economic burden to patients. Frizzled related protein (FRZB) participates in the regulation of various diseases (osteoarthritis, cardiovascular diseases and types of cancer) by regulating cell proliferation, motility, differentiation and inflammation, while its function in osteomyelitis remains to be elucidated. The present study aimed to uncover the role and underlying mechanism of FRZB mediation in Staphylococcus aureus (S. aureus)-induced osteomyelitis. Human bone marrow derived stem cells (hBMSCs) were treated with S. aureus to imitate an inflammatory osteomyelitis micro-environment in vitro, then mRNA and protein expression were severally assessed by RT-PCR and western blotting. The activity, apoptosis and differentiation of the cells were characterized via CCK-8, caspase-3 activity and Alizarin red sulfate/alkaline phosphatase staining, respectively. Expression levels of FRZB were upregulated in S. aureus-infected hBMSCs. Over-expression of FRZB significantly reduced hBMSC cell viability and differentiation while promoting cell apoptosis with or without S. aureus infection. However, FRZB knockdown reversed these effects. Once Wnt was impeded, the effect of FRZB downregulation was impeded to a great extent. Taken together, FRZB participated to regulate the osteomyelitis by activating the Wnt/β-catenin signaling pathway.

Nitric oxide synthase 2 genetic variation rs2297514 associates with a decreased susceptibility to extremity post-traumatic osteomyelitis in a Chinese Han population

Background

Previous studies have indicated that nitric oxide synthase 2 (NOS2) genetic variations are involved in delayed fracture healing and fracture non-union. Whether these genetic variants associate with the development of osteomyelitis (OM) remains unclear. Here, we analyzed the potential relationships between NOS2 genetic variations and the risk of developing post-traumatic OM (PTOM) in a Chinese Han population.

Methods

Altogether 704 participants, including 336 PTOM patients and 368 healthy controls, were genotyped of rs2297514 and rs2248814 of the NOS2 gene using the SNaPshot genotyping method.

Results

Outcomes showed that the frequency of allele C of rs2297514 in the patient group was significantly lower than that in the control group (48.7% vs. 54.5%, P = 0.029, OR = 0.792, 95% CI 0.642 - 0.976). In addition, significant associations were found between rs2297514 and susceptibility to PTOM by the recessive model (P = 0.007, OR = 0.633, 95% CI 0.453 - 0.884), and the homozygous model (P = 0.039, OR = 0.648, 95% CI 0.429 - 0.979). Moreover, patients with the CC genotype of rs2297514 had lower inflammatory biomarkers levels than the TT genotype, especially for the C-reactive protein (CRP) level (median: 4.1 mg/L vs. 8.9 mg/L, P = 0.027). However, no significant relationship was noted between rs2248814 and the risk of developing PTOM.

Conclusion

In this Chinese cohort, rs2297514 is correlated with a decreased risk of PTOM development, with genotype CC as a protective factor.

Systemic Antimicrobial Treatment of Chronic Osteomyelitis in Adults: A Narrative Review

Chronic osteomyelitis in adults is a complex condition that requires prolonged and intensive antimicrobial therapy, but evidence on optimal selection and duration of antibiotics is limited. A review of PubMed and Ovid Embase databases was conducted to identify systematic reviews, meta-analyses, retrospective and randomised controlled trials (RCTs) on antibiotic treatment outcomes in adults with chronic osteomyelitis. Three main areas of interest were investigated: short-term versus long-term antibiotic therapy, oral versus parenteral antibiotic therapy, and combination antibiotic therapy with rifampicin versus without rifampicin. A total of 36 articles were identified and findings were synthesised using a narrative review approach. The available literature suffers from limitations, including a lack of high-quality studies, inconsistent definitions, and varying inclusion/exclusion criteria among studies. Most studies are open-labelled and lack blinding. Limited high-quality evidence exists that oral therapy is non-inferior to parenteral therapy and that shorter antibiotic duration might be appropriate in low-risk patients. Studies on the impact of rifampicin are inconclusive. Further well-designed studies are needed to provide more robust evidence in these areas.

Design of Antibacterial Apatitic Composite Cement Loaded with Ciprofloxacin: Investigations on the Physicochemical Properties, Release Kinetics, and Antibacterial Activity

This work aims to develop an injectable and antibacterial composite cement for bone substitution and prevention/treatment of bone infections. This cement is composed of calcium phosphate, calcium carbonate, bioactive glass, sodium alginate, and ciprofloxacin. The effect of ciprofloxacin on the microstructure, chemical composition, setting properties, cohesion, injectability, and compressive strength was investigated. The in vitro drug release kinetics and the antibacterial activity of ciprofloxacin-loaded composites against staphylococcus aureus and Escherichia coli pathogens were investigated. XRD and FTIR analysis demonstrated that the formulated cements are composed of a nanocrystalline carbonated apatite analogous to the mineral part of the bone. The evaluation of the composite cement's properties revealed that the incorporation of 3 and 9 wt% of ciprofloxacin affects the microstructural and physicochemical properties of the cement, resulting in a prolonged setting time, and a slight decrease in injectability and compressive strength. The in vitro drug release study revealed sustained release profiles over 18 days. The amounts of ciprofloxacin released per day (0.2 -15.2 mg/L) depend on the cement composition and the amount of ciprofloxacin incorporated. The antibacterial activity of ciprofloxacin-loaded cement composites attested to their effectiveness to inhibit the growth of Staphylococcus aureus and Escherichia coli.

A Review of 3D Polymeric Scaffolds for Bone Tissue Engineering: Principles, Fabrication Techniques, Immunomodulatory Roles, and Challenges

Over the last few years, biopolymers have attracted great interest in tissue engineering and regenerative medicine due to the great diversity of their chemical, mechanical, and physical properties for the fabrication of 3D scaffolds. This review is devoted to recent advances in synthetic and natural polymeric 3D scaffolds for bone tissue engineering (BTE) and regenerative therapies. The review comprehensively discusses the implications of biological macromolecules, structure, and composition of polymeric scaffolds used in BTE. Various approaches to fabricating 3D BTE scaffolds are discussed, including solvent casting and particle leaching, freeze-drying, thermally induced phase separation, gas foaming, electrospinning, and sol-gel techniques. Rapid prototyping technologies such as stereolithography, fused deposition modeling, selective laser sintering, and 3D bioprinting are also covered. The immunomodulatory roles of polymeric scaffolds utilized for BTE applications are discussed. In addition, the features and challenges of 3D polymer scaffolds fabricated using advanced additive manufacturing technologies (rapid prototyping) are addressed and compared to conventional subtractive manufacturing techniques. Finally, the challenges of applying scaffold-based BTE treatments in practice are discussed in-depth.

Hexapeptide decorated β-cyclodextrin delivery system for targeted therapy of bone infection

Successfully treating bone infections is a major orthopedic challenge. Clinically, oral, intravenous, or intramuscular injections of drugs are usually used for direct or complementary treatment. However, once the drug enters the system, it circulates throughout the body, leading to an insufficient local dose and limiting the therapeutic effect because of the lack of targeting in the drug system. In this study, β-cyclodextrin, modified with poly (ethylene glycol) [PEG] and aspartic acid hexapeptide (Asp6-β-CD), was used to specifically target the hydroxyapatite (HA) component of the bone. It was then loaded with norfloxacin (NFX) to treat bone infections. The antibacterial ability of NFX was enhanced by loading it into Asp6-β-CD, because the solubility of Asp6-β-CD@NFX increased significantly. Moreover, Asp6-β-CD could target bone tissue in nude mice and showed significantly enhanced accumulation (10 times) than the unmodified β-CD. In addition, in a rat model of osteomyelitis, Asp6-β-CD@NFX targeted HA well and exerted its antibacterial activity, which reduced inflammation and promoted bone tissue repair. This study indicates that the Asp6-β-CD based drug delivery system can efficiently target bone tissue to enable potential applications for treating bone-related diseases.

Human Osteoblast-Conditioned Media Can Influence Staphylococcus aureus Biofilm Formation

Osteoblasts are bone-forming and highly active cells participating in bone homeostasis. In the case of osteomyelitis and more specifically prosthetic joint infections (PJI) for which Staphylococcus aureus (S. aureus) is mainly involved, the interaction between osteoblasts and S. aureus results in impaired bone homeostasis. If, so far, most of the studies of osteoblasts and S. aureus interactions were focused on osteoblast response following direct interactions with co-culture and/or internalization models, less is known about the effect of osteoblast factors on S. aureus biofilm formation. In the present study, we investigated the effect of human osteoblast culture supernatant on methicillin sensitive S. aureus (MSSA) SH1000 and methicillin resistant S. aureus (MRSA) USA300. Firstly, Saos-2 cell line was incubated with either medium containing TNF-α to mimic the inflammatory periprosthetic environment or with regular medium. Biofilm biomass was slightly increased for both strains in the presence of culture supernatant collected from Saos-2 cells, stimulated or not with TNF-α. In such conditions, SH1000 was able to develop microcolonies, suggesting a rearrangement in biofilm organization. However, the biofilm matrix and regulation of genes dedicated to biofilm formation were not substantially changed. Secondly, culture supernatant obtained from primary osteoblast culture induced varied response from SH1000 strain depending on the different donors tested, whereas USA300 was only slightly affected. This suggested that the sensitivity to bone cell secretions is strain dependent. Our results have shown the impact of osteoblast secretions on bacteria and further identification of involved factors will help to manage PJI.

A self-assembled bilayer polypeptide-engineered hydrogel for spatiotemporal modulation of bactericidal and anti-inflammation process in osteomyelitis treatment

Background

Drug resistance of pathogens and immunosuppression are the main causes of clinical stagnation of osteomyelitis. The ideal treatment strategy for osteomyelitis is to achieve both efficient antibacterial and bone healing through spatiotemporal modulation of immune microenvironment.

Methods

In this study, a bilayer hydrogel based on genetically engineered polypeptide AC10A and AC10ARGD was prepared by self-assembly. Ag2S QDs@DSPE-mPEG2000-Ce6/Aptamer (AD-Ce6/Apt) was loaded in the top layer AC10A hydrogel (AA) for antibacterial, and bone marrow-derived mesenchymal stem cells (BMSCs) were loaded in the lower layer AC10ARGD hydrogel (MAR) for bone healing. The AD-Ce6/Apt can be released from the AA hydrogel to target S. aureus before bacterial biofilm formation and achieved significant bactericidal effect under irradiation with a 660 nm laser. Moreover, AD-Ce6/Apt can induce M1 type polarization of macrophages to activate the immune system and eliminate residual bacteria. Subsequently, BMSCs released from the MAR hydrogel can differentiate into osteoblasts and promote the formation of an anti-inflammatory microenvironment by regulating the M2 type polarization of macrophages. The bilayer AA-MAR hydrogel possessed good biocompatibility.

Results

The in vitro and in vivo results showed that the AA-MAR hydrogel not only realized efficient photodynamic therapy of S. aureus infection, but also promoted the transformation of immune microenvironment to fulfill the different needs of each stage, which ultimately improved bone regeneration and mechanical properties post-surgery.

Conclusion

This work presents an approach for spatiotemporal modulation of immune microenvironment in the treatment of osteomyelitis.

Graphical Abstract

Nano Sized Hydroxyapatite-Polylactic Acid-Vancomycin in Alleviation of Chronic Osteomyelitis

Background

Objective

Methods

Results

Conclusion

Osteomyelitis, Oxidative Stress and Related Biomarkers

Bone is a very dynamic tissue, subject to continuous renewal to maintain homeostasis through bone remodeling, a process promoted by two cell types: osteoblasts, of mesenchymal derivation, are responsible for the deposition of new material, and osteoclasts, which are hematopoietic cells, responsible for bone resorption. Osteomyelitis (OM) is an invasive infectious process, with several etiological agents, the most common being Staphylococcus aureus, affecting bone or bone marrow, and severely impairing bone homeostasis, resulting in osteolysis. One of the characteristic features of OM is a strong state of oxidative stress (OS) with severe consequences on the delicate balance between osteoblastogenesis and osteoclastogenesis. Here we describe this, analyzing the effects of OS in bone remodeling and discussing the need for new, easy-to-measure and widely available OS biomarkers that will provide valid support in the management of the disease.

Fabrication and Characterization of Cinnamaldehyde-Loaded Mesoporous Bioactive Glass Nanoparticles/PHBV-Based Microspheres for Preventing Bacterial Infection and Promoting Bone Tissue Regeneration

Polyhydroxybutyrate-co-hydroxyvalerate (PHBV) is considered a suitable polymer for drug delivery systems and bone tissue engineering due to its biocompatibility and biodegradability. However, the lack of bioactivity and antibacterial activity hinders its biomedical applications. In this study, mesoporous bioactive glass nanoparticles (MBGN) were incorporated into PHBV to enhance its bioactivity, while cinnamaldehyde (CIN) was loaded in MBGN to introduce antimicrobial activity. The blank (PHBV/MBGN) and the CIN-loaded microspheres (PHBV/MBGN/CIN5, PHBV/MBGN/CIN10, and PHBV/MBGN/CIN20) were fabricated by emulsion solvent extraction/evaporation method. The average particle size and zeta potential of all samples were investigated, as well as the morphology of all samples evaluated by scanning electron microscopy. PHBV/MBGN/CIN5, PHBV/MBGN/CIN10, and PHBV/MBGN/CIN20 significantly exhibited antibacterial activity against Staphylococcus aureus and Escherichia coli in the first 3 h, while CIN releasing behavior was observed up to 7 d. Human osteosarcoma cell (MG-63) proliferation and attachment were noticed after 24 h cell culture, demonstrating no adverse effects due to the presence of microspheres. Additionally, the rapid formation of hydroxyapatite on the composite microspheres after immersion in simulated body fluid (SBF) during 7 d revealed the bioactivity of the composite microspheres. Our findings indicate that this system represents an alternative model for an antibacterial biomaterial for potential applications in bone tissue engineering.

Development of a large animal rabbit model for chronic periprosthetic joint infection

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 × 10⁹ 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.

Osteomyelitis of the jaws in patients with pycnodysostosis: a systematic review

Introduction

Pycnodysostosis is a rare autosomal recessive syndrome that provides the abnormal bone metabolism that increases the susceptibility of patients to develop osteomyelitis.

Objective

This systematic review was conducted to analyze the risk factors associated with the development of complications in the jaws (fractures and osteomyelitis), as well as their clinical-pathological characteristics and therapeutic approaches in patients with pycnodysostosis.

Methods

Searches were performed in the PubMed, Web of Science, Scopus, Lilacs, and Cochrane databases. Case reports or case series that met the eligibility criteria according to the PRISMA statement were included. The full texts of 31 articles were retrieved. Twenty of these articles published between 1969 and 2018 were selected, which described 26 cases of osteomyelitis in patients with pycnodysostosis.

Results

The mean age of the patients was 37.84 years; the male-to-female was 1.36:1. The mandible was the most affected site (76.9%). Tooth extraction was the main risk factor for osteomyelitis (61.5%), followed by infection (26.8%) and mandibular fracture (23.0%). Antibiotic therapy alone or combined with some surgical procedure was the treatment used in most cases (80.7%).

Conclusion

The findings of this review showed that patients with pycnodysostosis are more likely to develop osteomyelitis of the jaws after surgical procedures, especially tooth extraction which remains the main risk factor for its establishment. In addition, prophylactic antibiotic-therapy in the pre- and postoperative periods may prevent the development of osteomyelitis in pycnodysostosis.

An injectable and antibacterial calcium phosphate scaffold inhibiting Staphylococcus aureus and supporting stem cells for bone regeneration

Staphylococcus aureus (S. aureus) is the major pathogen for osteomyelitis, which can lead to bone necrosis and destruction. There has been no report on antibacterial calcium phosphate cement (CPC) against S. aureus. The aims of this study were to: (1) develop novel antibacterial CPC-chitosan-alginate microbead scaffold; (2) investigate mechanical and antibacterial properties of CPC-chitosan-penicillin-alginate scaffold; (3) evaluate the encapsulation and delivery of human umbilical cord mesenchymal stem cells (hUCMSCs). Flexural strength, elastic modulus and work-of-fracture of the CPC-chitosan-penicillin-alginate microbeads scaffold and CPC-chitosan scaffold were evaluated. Penicillin release profile and antibacterial effects on S. aureus were determined. The hUCMSC delivery and release from penicillin-alginate microbeads were investigated. Injectable CPC-chitosan-penicillin-alginate microbeads scaffold was developed for the first time. CPC-chitosan-penicillin-alginate microbeads scaffold had a flexural strength of 3.16 ± 0.55 MPa, matching that of cancellous bone. With sustained penicillin release, the new scaffold had strong antibacterial effects on S. aureus, with an inhibition zone diameter of 32.2 ± 2.5 mm, greater than that of penicillin disk control (15.1 ± 2.0 mm) (p < 0.05). Furthermore, this injectable and antibacterial scaffold had no toxic effects, yielding excellent hUCMSC viability, which was similar to that of CPC control without antibacterial activity (p > 0.05). CPC-chitosan-penicillin-microbeads scaffold had injectability, good strength, strong antibacterial effects, and good biocompatibility to support stem cell viability for osteogenesis. CPC-chitosan-penicillin-microbeads scaffold is promising for dental, craniofacial and orthopedic applications to combat infections and promote bone regeneration.

Co-administration of Erythromycin and Leech Salivary Extract Alleviates Osteomyelitis in Rats Induced by Methicillin-Resistant Staphylococcus aureus

OBJECTIVE

 Erythromycin (Ery) and leech saliva (LS) can inhibit Staphylococcus aureus growth in in vitro conditions. This study aimed to evaluate the activities and synergy between Ery and LS on chronic osteomyelitis in male Wistar rat's tibia induced by methicillin-resistant S. aureus (MRSA).

MATERIALS AND METHODS

 Four weeks after osteomyelitis induction, rats were divided into four groups including no treatment (control), Ery monotherapy (orally), LS monotherapy, or Ery + LS twice daily for 2 weeks. Staphylococcus aureus growth, pathological signs and inflammatory cytokine tumour necrosis factor-alpha (TNF-α) levels were assessed.

RESULTS

 Rats tolerated all therapeutic strategies well during the experiment. The Ery treatment alone significantly decreased bacterial growth, pathological signs and TNF-α levels. Leech saliva alone reduced TNF-α level significantly, but did not produce a significant reduction in bacterial growth and pathological signs. Ery + LS treatment significantly decreased bacterial growth, considerably alleviated bone pathological signs and decreased TNF-α levels compared with other groups. Statistical analysis suggested that there was a stronger efficiency and synergistic action of Ery and LS when combined against MRSA-induced osteomyelitis in rats.

CLINICAL SIGNIFICANCE

 The present study suggests that LS may have clinical utility to treat MRSA-induced osteomyelitis when combined with Ery or other therapeutics.

Evaluation of the bactericidal effect of cold atmospheric pressure plasma on contaminated human bone: an in vitro study

The use of cold atmospheric pressure plasma (CAPP) as a bacterial decontaminant for chronic wounds has shown good results. The purpose of this in vitro study was to evaluate the bactericidal effects of CAPP on the cancellous area of the bone. Sterile glass slides and processed sterile human bone allografts 1, 2, 3, and 4mm thick were used for initial contamination and further CAPP treatment. Each block was contaminated with Staphylococcus aureus suspension on one side. Each slide was turned 180° and treated on the reverse side. The bacterial count in colony-forming units (CFU) was then measured and compared with that of a control group, and the bactericidal effects of CAPP in relation to bone density evaluated. A significant reduction in count was measured between treated and untreated groups (groups A-D: p<0.01 and group E: p=0.04). A strong positive linear relation was found between bone density and the S aureus count (r=0.844, p=0.156). Treatment with CAPP had a bactericidal effect on bone structures with a penetration depth of up to 4mm. It might be used for all diseases involving infected bone, and so extends the existing range of treatments.

Role of 18F-flurodeoxyglucose in orthopaedic implant-related infection: review of literature and experience

Infection and inflammation are a common occurrence with orthopaedic procedures. Anatomical modalities can show the transformation in the disease process; however, these may occur later when compared with functional imaging modalities that are more likely to identify early disease patterns. Various molecular imaging modalities such as three-phase bone scintigraphy, labelled leucocyte scintigraphy, as well as radiolabelled antibiotics and immunoglobulins have been considered and have played key roles in assisting clinical decision-making. While 18F-flurodeoxyglucose (FDG) PET/computed tomography (CT) has been relatively well established in cancer pathways, it has the potential to contribute to surgical decision making for possible osteomyelitis post-metal implant surgery. In this article, we present a review of recently used tracers, and share our experience with using 18F-FDG PET/CT studies in a few diverse clinical settings related to post-metal implant osteomyelitis.

Dual Functional Monocytes Modulate Bactericidal and Anti-Inflammation Process for Severe Osteomyelitis Treatment

Osteomyelitis is an inflammatory bone disease caused by infection microorganisms which leads to progressive bone destruction and loss. Drug resistance and inflammatory damage make it urgent to develop new dual-functional therapies. Based on the powerful bactericidal effect of monocyte/macrophage cells by nature, a functional monocyte with programed anti-inflammatory ability is promising for osteomyelitis treatment. Herein, gold nanocage (GNC)-modified monocytes are developed which contain aspirin to realize the controlled antibacterial and anti-inflammatory process for bone infection treatment effectively. Aspirin@GNC-laden monocytes inherit the biological functions of origin monocytes such as chemotaxis to bacteria, differentiation potential, and phagocytic ability. The controlled release of aspirin from GNC has a beneficial effect on improving the rate and amount of bone regeneration after the anti-infection stage due to its ability to suppress the activity of natural immunity and induce osteoblast differentiation during the treatment of osteomyelitis. The present work described here is the first to utilize living monocytes to achieve a dual effect to antibacteria and anti-inflammation in a time-oriented and programed way, and provides an inspiration for future therapy based on this concept.

IFN-γ +874T/A polymorphism increases susceptibility to post-traumatic osteomyelitis

Immunological inflammatory reaction is one of the key links in the occurrence and development of post-traumatic osteomyelitis after microbial invasion. Growing evidence suggests complex interactions between IFN-γ and bone remodelling cells. However, potential association of IFN-γ gene polymorphism with susceptibility to post-traumatic osteomyelitis remains unclear. This study aimed to investigate the potential link between IFN-γ +874T/A polymorphism and risk of developing post-traumatic osteomyelitis. A total of 189 patients with post-traumatic osteomyelitis and 200 healthy controls were enrolled for genotyping using the SNaPshot genotyping method. Statistically significant associations were found between the gene polymorphism and the risk of post-traumatic osteomyelitis by dominant model (AA + AT vs. TT, OR = 1.820, p = .017) and heterozygous model (AT vs. TT, OR = 1.781, p = .029). Moreover, the frequency of mutant allele A was significantly higher in the patients than that in the healthy controls (15.07% vs. 9.25%, OR = 1.742, p = .013). IFN-γ +874T/A polymorphism may contribute to the increased susceptibility to post-traumatic osteomyelitis.

Formulation and characterization of a novel PHBV nanocomposite for bone defect filling and infection treatment

Biodegradable materials that combine bioactivity with sustained drug release have been proved promising for the treatment and prophylaxis of bone infection. In this work, injection-molded nanocomposites were formulated from poly(3-hydroxybutyrate-co-3-6%hydroxyvalerate) (PHBV), nanodiamond (nD) and nanohydroxyapatite (nHA) loaded with vancomycin (VC). The components were compounded using a rotary evaporator (PHBV/nHA/VC/nD-R) or a spray-dryer (PHBV/nHA/VC/nD-SD). The nanoparticles acted as a nucleating agent, increasing PHBV crystallinity from 57.1% to up to 73.3% (PHBV/nHA/VC/nD-SD). The nHA particles were found to be well distributed on the formulations fracture surface observed by SEM-EDS micrographs. PHBV/nHA/VC/nD-SD presented higher glass transition temperature (18.1 vs 14.8 °C) and stronger interface than PHBV/nHA/VC/nD-R, as determined by dynamic mechanical analysis (DMA). Furthermore, the incorporation of nanoparticles increased PHBV flexural elastic modulus by 34% and match the reported for human bone. Both systems were able to present a sustained release of VC for 22 days, reaching 7.1 ± 1.3%(PHBV/nHA/VC/nD-R) and 4.8 ± 0.6% (PHBV/nHA/VC/nD-SD). VC presented antibacterial activity even after being processed at 178 °C in an injection molding machine. Moreover, in vitro assays showed a good adhesion and growth of cells on the specimens and suggested a non-cytotoxic and non-cytostatic behavior. These findings indicate that these systems can be further explored as bone defect filling material.

A new transformation method with nanographene oxides of antisense carrying yycG RNA improved antibacterial properties on methicillin-resistant Staphylococcus aureus biofilm

Staphylococcus aureus has the potential to opportunistically cause infectious diseases. The aim of this study was to determine the antimicrobial effects of novel graphene oxide (GO)-polyethylenimine (PEI)-based antisense yycG (ASyycG) on the inhibition of methicillin-resistant S. aureus (MRSA) biofilm formation. In current study, a novel GO-PEI-based recombinant ASyycG vector transformation strategy was developed to produce ASyycG. The mechanical features including zeta-potential and particle size distributions were evaluated by: GO; GO-PEI and GO-PEI-ASyycG. The recombinant ASyycG vector was transformed into MRSA cells, and the expression levels of the yycF/G and icaADB genes were determined and compared by quantitative real-time PCR (qPCR) assays. The recombinant ASyycG plasmids were subsequently modified with a gene encoding enhanced green fluorescent protein (ASyycG-eGFP) as a reporter gene, and the transformation efficiency was assessed by the fluorescence intensity. The biofilm biomass and bacterial viability of the MRSA strains were evaluated by crystal violet assay, colony-forming unit assays and confocal laser scanning microscopy. The results showed that the Z-average sizes of GO-PEI-ASyycG were much larger than those of GO or GO-PEI. The GO-PEI-based strategy significantly increased the efficiency of ASyycG transformation. The GO-PEI-ASyycG-transformed MRSA strain had the lowest expression levels of the biofilm formation-associated genes. Furthermore, GO-PEI-ASyycG suppressed biofilm aggregation and improved bactericidal effects on the MRSA after 24 hr of biofilm establishment. Our findings demonstrated that GO-PEI based antisense yycG RNA will be an effective method for management of MRSA infections.

Double-Stranded RNA Is a Novel Molecular Target in Osteomyelitis Pathogenesis: A Translational Avian Model for Human Bacterial Chondronecrosis with Osteomyelitis

Osteomyelitis remains a serious inflammatory bone disease that affects millions of individuals worldwide and for which there is no effective treatment. Despite scientific evidence that Staphylococcus bacteria are the most common causative species for human bacterial chondronecrosis with osteomyelitis (BCO), much remains to be understood about the underlying virulence mechanisms. Herein, we show increased levels of double-stranded RNA (dsRNA) in infected bone in a Staphylococcus-induced chicken BCO model and in human osteomyelitis samples. Administration of synthetic [poly(I:C)] or genetic (Alu) dsRNA induces human osteoblast cell death. Similarly, infection with Staphylococcus isolated from chicken BCO induces dsRNA accumulation and cell death in human osteoblast cell cultures. Both dsRNA administration and Staphylococcus infection activate NACHT, LRR and PYD domains-containing protein (NLRP)3 inflammasome and increase IL18 and IL1B gene expression in human osteoblasts. Pharmacologic inhibition with Ac-YVAD-cmk of caspase 1, a critical component of the NLRP3 inflammasome, prevents DICER1 dysregulation- and dsRNA-induced osteoblast cell death. NLRP3 inflammasome and its components are also activated in bone from BCO chickens and humans with osteomyelitis, compared with their healthy counterparts. These findings provide a rationale for the use of chicken BCO as a human-relevant spontaneous animal model for osteomyelitis and identify dsRNA as a new treatment target for this debilitating bone pathogenesis.

G-CSF partially mediates bone loss induced by Staphylococcus aureus infection in mice

Bone loss in Staphylococcus aureus (S. aureus) osteomyelitis poses a serious challenge to orthopedic treatment. The present study aimed to elucidate how S. aureus infection in bone might induce bone loss. The C57BL/6 mice were injected with S. aureus (10⁶ CFU/ml, 100 μl) or with the same amount of vehicle (control) via the tail vein. Microcomputed tomography (microCT) analysis showed bone loss progressing from week 1 to week 5 after infection, accompanied by a decreased number of osteocalcin-positive stained osteoblasts and the suppressed mRNA expression of Runx2 and osteocalcin. Transcriptome profiles of GSE30119 were downloaded and analyzed to determine the differences in expression of inflammatory factors between patients with S. aureus infected osteomyelitis and healthy controls, the data showed significantly higher mRNA expression of granulocyte colony-stimulating factor (G-CSF) in the whole blood from patients with S. aureus infection. Enzyme-linked immunosorbent assay (ELISA) analysis confirmed an increased level of G-CSF in the bone marrow and serum from S. aureus infected mice, which might have been due to the increased amount of F4/80⁺ macrophages. Interestingly, G-CSF neutralizing antibody treatment significantly rescued the bone loss after S. aureus infection, as evidenced by its roles in improving BV/TV and preserving osteocalcin- and osterix-positive stained cells. Importantly, we found that G-CSF level was significantly up-regulated in the serum from osteomyelitis patients infected by S. aureus Together, S. aureus infection might suppress the function of osteoblastic cells and induce progressive bone loss by up-regulating the level G-CSF, suggesting a therapeutic potential for G-CSF neutralization in combating bone loss in S. aureus osteomyelitis.

Efficacy of novel nano-hydroxyapatite/polyurethane composite scaffolds with silver phosphate particles in chronic osteomyelitis

Recently, chronic osteomyelitis is still a challenging surgical problem. Unfortunately, the traditional clinical method using bone cement loaded antibiotics is restricted due to its non-biodegradability and limited release of antibiotics. Hydroxyapatite is a good adsorbent with good biocompatibility, an ideal bone repair material, and can avert the requirement for the secondary surgical procedure of removal. In this study, nano-hydroxyapatite combined with a polyurethane containing 3% silver (Ag/n-HA/PU) was synthesized, and investigated for its efficacy of treating chronic bone infection with bone defects. To clarify its silver ions release characteristics, the concentration of the Ag⁺ in the elution was analyzed every day after in vitro deionized water immersion. A chronic osteomyelitis of tibia in rabbit model was established, and 70 New Zealand rabbits were divided into 4 groups, including the blank control group, nano-hydroxyapatite combined with polyurethane (n-HA/PU) implant group, 3% Ag/n-HA/PU group and 10% Ag/n-HA/PU group after debridement. Routine blood tests, radiography, Micro-CT, and histological staining were conducted at 4 days, 3, 6 and 12 weeks post-treatment. The results showed that the released silver from the 3% Ag/n-HA/PU and 10% Ag/n-HA/PU exhibited an initial burst release and followed by a slow controlled release up to 39 days and 42 days respectively. A good repair of bone defects, an appropriate rate of degradation of scaffolds and no significant toxicity were observed in the 3% Ag/n-HA/PU group, indicating the advantages of this novel synthetic scaffold to be a potential option for the treatment of chronic osteomyelitis. A novel nano-composite, nano-hydroxyapatite combined with a polyurethane containing 3% silver (Ag/n-HA/PU) provide controlled release of Ag⁺, illustrated by its abilities of biodegradation, antimicrobial activity, and favorable repair of bone defects in the treatment of chronic osteomyelitis.

Foot and ankle infections: Debridement, early fixation and rifampicin provide earlier recovery of function and quality of life

BACKGROUND

Infection after foot and ankle fractures is a major concern for orthopedic surgeons. It is widely believed that final osteosynthesis should be delayed until the infection is cured. However, there is no literature that supports this practice. In addition, the delay impairs patient function and quality of life (QoL).

METHODS

In the present study, four cases of ankle infection treated with aggressive debridement, early fixation and antibiofilm antibiotics are described. It is thought that, like other implant related infections, ankle infections can be rapidly treated with the definitive fixation and by curing the infection to make for a fast recovery of QoL and function.

RESULTS

The infections were caused by MSSA and Pseudomonas aeruginosa in case 1, MSSA in case 2 and MRSA as well as K. pneumonia in case 3. Case 4 was a culture negative infection. They were susceptible to antibiofilm antibiotics (the gram-negative bacilli susceptible to ciprofloxacin and the gram-positive cocci susceptible to rifampicin). Cases 1, 3 and 4 were treated with a tibio-talo-calcaneal arthrodesis and case 2 was treated with a de-rotational fibular osteotomy and a medial closing wedge supramalleolar osteotomy. All cases improved at a median time of 4 weeks in terms of quality of life (SF-36) and function (AOFAS). At 2-years follow-up, no recurrence of infection was observed in any of the cases. All the cases achieved fusion or osteotomy healing at final follow-up.

CONCLUSIONS

Early fixation after debridement combined with antibiofilm antibiotics can be performed in foot and ankle inflections to provide early recovery of QoL and function in patients.

Staphylococcus aureus biofilm organization modulated by YycFG two-component regulatory pathway

BACKGROUND

Staphylococcus aureus (S. aureus) infection accounts for more than 50% of the osteomyelitis cases. Currently, methicillin-resistant S. aureus (MRSA) strains present an urgent medical problem. The YycFG two-component regulatory system (TCS) can allow bacteria to rapidly adapt to physical, chemical, and biological stresses. To define the role of YycFG in modulation virulence of S. aureus in osteomyelitis, we isolated clinical MRSA strains and compared these with ATCC29213 methicillin-sensitive S. aureus (MSSA).

METHODS

In the present study, 13 MRSA strains from chronic osteomyelitis tissues were isolated. The in-depth sequencing of 16S rRNA amplicons of the samples was conducted. Bacterial growth was monitored, and biofilm biomass was determined by crystal violet microtiter assay. Furthermore, quantitative RT-PCR analysis was adopted to identify the expression of yycF/G/H and icaA/D in MRSA and MSSA strains. Analysis of variance with one-way ANOVA was used for statistical analysis.

RESULTS

The in-depth sequencing of 16S rRNA amplicons of the clinical samples indicated a polymicrobial infection, with the phylum Firmicutes made up 13% of the microbial population. The MRSA strains showed an accelerated growth rate compared to the MSSA strains. Of note, MRSA biofilms showed an accumulation of an intercellular polysaccharides matrix and enhanced biomass upon microscopic examination. Furthermore, MRSA strains had a higher expression of the yycF/G/H and icaA/D genes and adhesion force.

CONCLUSIONS

These data suggested the roles of intercellular polysaccharide in S. aureus pathogenesis, indicating a possible association between YycFG pathways and MRSA strain virulence.

Quantitative B-lymphocyte deficiency and increased TCRγδ T-lymphocytes in acute infectious spondylodiscitis

Acute infectious spondylodiscitis (AIS) is a serious infection of the spine with rising incidence and a mortality of 3–6%. The role of the immune system in AIS is largely unknown. We performed extensive B and T-lymphocyte phenotyping in patients with AIS at diagnosis and after treatment cessation. In this prospective multicentre study, flow cytometric analysis of T and B-lymphocyte subsets was performed in 35 patients at diagnosis and 3 months after treatment cessation. We additionally analysed levels of immunoglobulins and IgG subclasses, serum level and genetic variants of mannose-binding lectin, and somatic hypermutation. A total of 22 (61%) patients had B-lymphocytes below reference limit at baseline, persisting in 7 (30%) patients at follow-up. We found a lower proportion of CD19 + CD27 + IgD+ marginal zone B-lymphocytes and a higher proportion of γδ+ T-lymphocyte receptors compared with controls at both time points. Immunoglobulin levels were elevated at baseline compared to follow-up, and not associated with absolute B-lymphocyte count. In conclusion, a large proportion of AIS patients presented with profound B-lymphocyte deficiency, only partly reversible at follow-up. Identification of immune dysfunction related to AIS may allow for future targeted therapeutic interventions to restore host immunity.

Raman Spectroscopy detects changes in Bone Mineral Quality and Collagen Cross-linkage in Staphylococcus Infected Human Bone

Diagnosis of osteomyelitis presents a formidable challenge. Lack of pathognomonic clinical sign(s) and diagnostic tests that can diagnose osteomyelitis at an early stage contribute to this difficulty. If the diagnosis is not made early, the disease becomes very difficult to eradicate and can lead to limb threatening and potentially life-threatening complications. Staphylococcus aureus is the most common organism causing osteomyelitis. Raman Spectroscopy provides information about molecular vibration that could potentially be harnessed as a spectral signature for cellular changes in specific pathologic conditions. In this study we describe a technique using Raman spectroscopy that could potentially be used to diagnose staphylococcal osteomyelitis. Human bone samples were co-cultured with Staphylococcus aureus (S. aureus) and the effects of bacterial growth on bone quality were then monitored using Raman spectroscopy. A major drop in the bone mineral quality and crystallinity was observed in the infected bones compared to the controls. S. aureus infection was also found to alter the collagen cross-linking. Our study shows that specific spectral signatures are present for the cause as well as the effect of staphylococcal osteomyelitis, opening the possibility of developing a useful diagnostic modality for early and rapid diagnosis of this condition.

From macrophage to osteoclast - How metabolism determines function and activity

Osteoclasts are specialised cells that resorb bone and develop from the monocyte/macrophage lineage. While there is a wealth of information on the regulation of macrophage function through metabolic activity, the connection between osteoclast differentiation and metabolism is less well understood. Recent data show that mitochondria participate in switching macrophages from an inflammatory phenotype towards differentiation into osteoclasts. Additionally, it was found that reactive oxygen species (ROS) actively take place in osteoclast differentiation by acting as secondary signalling molecules. Bone resorption is an energy demanding process and differentiating osteoclasts triggers the biogenesis of mitochondria. In addition, the activity of specific OXPHOS components of macrophages and osteoclasts is differentially regulated. This review summarises our knowledge on macrophage-mediated inflammation, its impact on a cell's metabolic activity and its effect on osteoclast differentiation.

Acute and Chronic Suppurative Osteomyelitis of the Jaws: A 10-Year Review and Assessment of Treatment Outcome

PURPOSE

To review cases of suppurative osteomyelitis of the jaws treated at the Massachusetts General Hospital (Boston, MA) over a 10-year period, evaluate specifics of disease presentation, and answer the clinical question: are there identifiable variables associated with treatment outcome?

MATERIALS AND METHODS

A retrospective cohort study was completed using patients treated for suppurative osteomyelitis of the jaws at the Massachusetts General Hospital from April 2006 to October 2016. Inclusion criteria were a diagnosis of suppurative osteomyelitis of the jaw, age older than 18 years, and complete medical records. Patients with nonsuppurative disease, radiation history, or antiresorptive exposure were excluded. Candidate variables included demographic information, medical and dental history, presenting signs and symptoms, and radiologic and laboratory findings. The outcome variable was successful treatment, defined as resolution of symptoms and radiographic evidence of healing after initial treatment. Appropriate statistical analyses were performed with significance set a P value less than .05.

RESULTS

Forty-two patients met the inclusion criteria. Mean age was 53 years (range, 20 to 80 yr) and 26 were women (62%). Common comorbidities included cardiovascular disease (52%), tobacco use (45%), and psychiatric disorders (45%). Pain (90%), swelling (86%), and neurosensory change (50%) were the most common findings. Common microbacterial isolates included Streptococcus milleri (74%) and coagulase-negative Staphylococcus species (43%), which showed marked antibiotic resistance. Surgical debridement was the most common intervention (93%). Successful treatment was found in 86%. Of 6 persistent cases, 4 resolved with a second debridement and continued antibiotics and 2 required resection. Increased white blood cell (WBC) count at presentation (P = .005) and associated psychiatric diagnoses (P = .037) were statistically associated with unsuccessful initial treatment.

CONCLUSION

The results of this study indicate that antibiotic resistance is commonly encountered in this patient population, although it was not associated with unsuccessful outcome. Patients presenting with increased WBC count and concurrent psychiatric comorbidities required protracted treatment.

The black soldier fly, Hermetia illucens - a promising source for sustainable production of proteins, lipids and bioactive substances

The growing demand worldwide for proteins and lipids cannot be met by the intensive use of agricultural land currently available. Insect mass cultures as a source for proteins and lipids have been in focus for various reasons. An insect with many positive properties is the black soldier fly, Hermetia illucens, whose larvae could be used for the sustainable production of proteins and lipids. Furthermore, the larvae produce bioactive substances which could potentially be used for human and animal welfare.

Complete resolution and remodeling of chronic recurrent multifocal osteomyelitis on MRI and radiographs

Chronic recurrent multifocal osteomyelitis (CRMO) is a rare condition thought to be under-diagnosed, with a true prevalence of more than the 1 in 10,000 estimated. It is a condition that is classically described as polyostotic with a relapsing and remitting course, preferentially affecting the metaphyses of tubular bones in the pediatric population. Lesions have characteristic appearances of cortical hyperostosis and mixed lytic/sclerotic medullary appearances radiographically, with active osteitis and periostitis best seen with fluid-sensitive sequences on magnetic resonance imaging (MRI). There are reports of lesions resolving on follow-up radiographs and MRI scans, but no supporting images. In particular, although the marrow appearances and degree of osteitis have been shown to improve on MRI, complete resolution and remodeling back to normal has never been demonstrated. We present a case of a lesion that has completely healed and remodeled back to normal appearances on both radiographs and MRI, and consider this the standard for the often loosely used terms "normalization" and "resolution". We discuss the implications of this for our understanding of the natural history of CRMO, and how this adds weight to the condition being significantly under-diagnosed. It provides a "gold standard" to be aimed for when assessing treatments for CRMO, and the optimal outcomes that are possible. It also provides further insight into the potential of pediatric bone to recover and remodel when affected by inflammatory conditions.

Staphylococcal Osteomyelitis: Disease Progression, Treatment Challenges, and Future Directions

Osteomyelitis is an inflammatory bone disease that is caused by an infecting microorganism and leads to progressive bone destruction and loss. The most common causative species are the usually commensal staphylococci, with Staphylococcus aureus and Staphylococcus epidermidis responsible for the majority of cases. Staphylococcal infections are becoming an increasing global concern, partially due to the resistance mechanisms developed by staphylococci to evade the host immune system and antibiotic treatment. In addition to the ability of staphylococci to withstand treatment, surgical intervention in an effort to remove necrotic and infected bone further exacerbates patient impairment. Despite the advances in current health care, osteomyelitis is now a major clinical challenge, with recurrent and persistent infections occurring in approximately 40% of patients. This review aims to provide information about staphylococcus-induced bone infection, covering the clinical presentation and diagnosis of osteomyelitis, pathophysiology and complications of osteomyelitis, and future avenues that are being explored to treat osteomyelitis.

Diminished bone regeneration after debridement of posttraumatic osteomyelitis is accompanied by altered cytokine levels, elevated B cell activity, and increased osteoclast activity

Osteomyelitis is a frequent consequence of open fractures thus representing a common bone infection with subsequent alteration of bone regeneration. Impaired bone homeostasis provokes serious variations in the bone remodeling process, thereby involving multiple inflammatory cytokines to activate bone healing. Our previously established mouse model of posttraumatic osteomyelitis provides the chance to study regulation of selected cytokines after surgical debridement of osteomyelitis thus illustrating the course of initial infectious recovery. An inflammatory cytokine array revealed specifically upregulated cytokines in debrided animals after bone infection, that were verified by Western blot analysis, identifying increased levels of CCL2, CCL3, and CXCL2. Increased osteoclastogenesis after debridement of osteomyelitis was demonstrated by Calcitonin-receptor and RANKL detection via immunohistochemical and -fluorescence stainings. The substantial protein analysis was complemented by uncovering diminished osteogenesis and proliferation in debrided group, tracking Osteocalcin, RUNX2, and PCNA expression. Interestingly TNF-α expression seemed to have no effect on altered bone regeneration after bone infection. Additional flow cytometry analysis proved elevated B cell activity, subsequently increased osteoclast activity and accelerated bone resorption. Based on the variety of severely altered cytokines, we propose a RANKL-dependent osteoclastogenesis after debridement of osteomyelitis coinciding with elevated B cells and simultaneously decreased osteogenesis. A comprehensive understanding of these mechanisms provides new therapeutic options of osteomyelitis cure and is of great importance in prospective medical treatment. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2425-2434, 2017.

Staphylococcus Aureus Induces Osteoclastogenesis via the NF-κB Signaling Pathway

Background

Osteomyelitis is one of the refractory diseases encountered in orthopedics, while Staphylococcus aureus (S. aureus) is the most common causative organism in osteomyelitis. However, the precise mechanisms underlying the bone loss caused by S. aureus infection have not been well defined. Here, we investigated the effect of S. aureus on osteoclast differentiation and the probable molecular mechanism.

Material/Methods

RAW 264.7 cells were treated for 5 days with live S. aureus, inactivated S. aureus, and S. aureus filtrate. Then, the formation of osteoclast-like cells and resorption pits was observed, and the expression of osteoclast-specific genes (TRAP, MMP-9, cathepsin K, CTR and Atp6v0d2) was detected by real-time PCR. Moreover, key proteins in the signaling pathway associated with osteoclast differentiation were detected with Western blot.

Results

The data showed that live S. aureus, inactivated S. aureus, and S. aureus filtrate induced osteoclast formation, promoted bone resorption, and increased the expression of osteoclast-specific genes in a dose-dependent manner in the absence RANKL. In addition, we found that the S. aureus-induced osteoclastogenesis was related to the degradation of IκB-α, phosphorylation of NF-κB p65, and increased expression of NFATc1. Thus, we used JSH-23 to inhibit NF-κB transcriptional activity. The effect of the S. aureus-induced osteoclastogenesis and the expression of osteoclast-specific genes and NFATc1 were inhibited, which indicated that the NF-κB signaling pathway plays a role in S. aureus-induced osteoclastogenesis.

Conclusions

This study demonstrated that S. aureus induces osteoclastogenesis through its cell wall compound and secretion of small soluble molecules, and the NF-κB signaling pathway plays a role in this process.

Chronic Osteomyelitis of the Distal Femur Treated with Resection and Delayed Endoprosthetic Reconstruction: A Report of Three Cases

Chronic osteomyelitis involving the distal femur often results in amputation or arthrodesis. This article presents three cases of chronic osteomyelitis treated with a staged approach culminating in endoprosthetic reconstruction. Stage one involved resection of infected bone and placement of an intramedullary nail spanning the bony defect between proximal femur and tibia, with antibiotic cement packed around the nail. Patients were then placed on long-term IV +/- oral antibiotics to clear the infection. A "cooldown" period was then used between stages where patients were off antibiotics and inflammatory markers were monitored for signs of remaining infection. Stage two then involved reconstruction of the distal femur and knee with an endoprosthesis. In the appropriate patient, this treatment strategy offers another option in this challenging population.

Bad to the Bone: On In Vitro and Ex Vivo Microbial Biofilm Ability to Directly Destroy Colonized Bone Surfaces without Participation of Host Immunity or Osteoclastogenesis

Bone infections are a significant public health burden associated with morbidity and mortality in patients. Microbial biofilm pathogens are the causative agents in chronic osteomyelitis. Research on the pathogenesis of osteomyelitis has focused on indirect bone destruction by host immune cells and cytokines secondary to microbial insult. Direct bone resorption by biofilm pathogens has not yet been seriously considered. In this study, common osteomyelitis pathogens (Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans, and Streptococcus mutans) were grown as biofilms in multiple in vitro and ex vivo experiments to analyze quantitative and qualitative aspects of bone destruction during infection. Pathogens were grown as single or mixed species biofilms on the following substrates: hydroxyapatite, rat jawbone, or polystyrene wells, and in various media. Biofilm growth was evaluated by scanning electron microscopy and pH levels were monitored over time. Histomorphologic and quantitative effects of biofilms on tested substrates were analyzed by microcomputed tomography and quantitative cultures. All tested biofilms demonstrated significant damage to bone. Scanning electron microscopy indicated that all strains formed mature biofilms within 7 days on all substrate surfaces regardless of media. Experimental conditions impacted pH levels, although this had no impact on biofilm growth or bone destruction. Presence of biofilm led to bone dissolution with a decrease of total volume by 20.17±2.93% upon microcomputed tomography analysis, which was statistically significant as compared to controls (p <0.05, ANOVA). Quantitative cultures indicated that media and substrate did not impact biofilm formation (Kruskall-Wallis test, post-hoc Dunne's test; p <0.05). Overall, these results indicate that biofilms associated with osteomyelitis have the ability to directly resorb bone. These findings should lead to a more complete understanding of the etiopathogenesis of osteomyelitis, where direct bone resorption by biofilm is considered in addition to the well-known osteoclastic and host cell destruction of bone.

An effective treatment of experimental osteomyelitis using the antimicrobial titanium/silver-containing nHP66 (nano-hydroxyapatite/polyamide-66) nanoscaffold biomaterials

Effective treatment of osteomyelitis remains a formidable clinical challenge. The rapid emergence of multidrug-resistant bacteria has renewed interest in developing antimicrobial biomaterials using antiseptic silver ions to treat osteomyelitis. However, inadequate local retention and severe cytotoxic effects have limited the clinical use of ionic silver for bone grafts. We recently developed novel porous nano-hydroxyapatite/polyamide 66 (nHP66)-based nanoscaffold materials containing varied concentrations of silver ions (Ag⁺) (TA-nHAPA66) and oxidized titanium (TiO₂), which was added as a second binary element to enhance antibacterial activity and biocompatibility. In this study, we establish a large cohort of rabbit model of experimental osteomyelitis and investigate the in vivo antimicrobial and therapeutic effects of TA-nHP66 biomaterials and their in vivo silver release kinetics. We find the TA-nHP66 scaffolds exhibit potent antibacterial activities against E. coli and S. aureus, support cell adhesion and cell proliferation of pre-osteoblasts, and stimulate osteogenic regulator/marker expression. Moreover, the TA2-nHP66 scaffold exerts potent antibacterial/anti-inflammation effects in vivo and promotes bone formation at the lesion site of osteomyelitis. We further demonstrate that TA2-nHP66 exhibits excellent biosafety profile without apparent systemic toxicities. Therefore, the TA-nHP66 scaffold biomaterials may be further explored as an effective adjuvant therapy for infected bone defects and/or osteomyelitis debridement.