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

Facile one-step antibacterial biomineralized scaffolds through regulation of chitosan by imitating bone ingredient bonding to inspire endogenous repair

In situ mineralization based on chitosan (CS) as an organic template achieves uniform distribution of nano-hydroxyapatite (nHAp), and is expected to enhance interface bonding between materials and tissues, therefore promoting endogenous bone repair. However, chitosan-based materials are difficult to provide certain mechanical and antibacterial properties. In this study, Ca2+ and PO43- were used as the precursor of nHAP, Zn2+ as the precursor of nano-ZnO, and synthesized nHAp/ZnO particles in situ on the surface of chitosan to form CS/HAp/ZnO bone repair scaffold. The results indicated that the incorporated Zn2+ was chemically bonded to the system, with formed particles evenly distributed, which achieved more efficient antibacterial activity and osteogenic induction performance in vivo. The material had interconnected pore structure with a porosity of >70 %, which simulates the microenvironment of natural bone. The formed inorganic particles improved the mechanical properties of the chitosan scaffold to match the rate of new bone formation. ZnO endowed scaffolds with antibacterial activity, with antibacterial rate of >95 %. In addition, the material also showed good cell compatibility and biological activity, and promoted the adhesion, migration, proliferation and differentiation of osteoblast-related cells.

Evaluating the antimicrobial and anti-inflammatory mechanisms of dexmedetomidine in managing bone infection: a laboratory perspective

BACKGROUND

Osteomyelitis involves bone destruction, impaired bone formation, and systemic inflammation. Dexmedetomidine (DXMT) possesses antioxidant, anti-inflammatory, and anti-apoptotic properties alongside sedative and analgesic effects. This study evaluates DXMT's effects on markers of infection and bone healing using osteocyte-like cells infected by Staphylococcus aureus (S. aureus).

METHODS

Human osteosarcoma-derived SAOS-2 cells were differentiated to an osteocyte-like phenotype over 28 days using potassium dihydrogen phosphate. Differentiation was verified via qPCR for osteogenic markers. Cytotoxicity of DXMT (0.1-10 µM) was tested using WST-1 assay and Reactive Oxygen Species (ROS) production analysis. Cells infected with S. aureus were treated with DXMT to assess its antimicrobial, anti-inflammatory (via ELISA for cytokines IL1-ß, TNF-⍺, IL-17, and IL-6), and osteogenesis-promoting effects.

RESULTS

DXMT ≤ 1 µM did not affect cell viability, while 2, 5, and 10 µM DXMT administration reduced cell counts. A 5 µM dose slightly reduced intracellular bacterial load (6.2 log in controls vs. 6.1 log with DXMT), while neither less nor more DXMT was effective on reducing the S. aureus load. Doses ≥ 5 µM effectively reduced ROS production and inflammation post-infection in a time-dependent manner. S. aureus infection decreased osteogenic markers, but DXMT mitigated cellular stress and inflammation with a positive impact on osteogenesis at therapeutic doses.

CONCLUSION

DXMT at 5 µM is an optimal dose to reduce infection-induced cellular stress and promote bone healing in osteomyelitis in vitro, balancing antimicrobial effects and cytotoxicity.

Engineered bacillus subtilis enhances bone regeneration via immunoregulation and anti-Infection

Chronic osteomyelitis caused by implant infections is a common complication following orthopedic surgery. Preventing bacterial infection and simultaneously improving bone regeneration are the key for osteomyelitis. Current treatments include systemic antibiotics and multiple surgical interventions, but the strategies available for treatment are limited. In this study, a multifunctional engineered Bacillus subtilis (B. sub) hydrogel with sulfasalazine (SSZ) is developed to treat methicillin-resistant Staphylococcus aureus (MRSA) infection and anti-inflammatory and promote bone regeneration. B. sub in alginate hydrogels protects B. sub from being cleared by the host immune system while allowing the release of its bioactive substances, including antibacterial peptides and anti-inflammatory agents such as SSZ. The results show that the engineered probiotic hydrogels exhibit excellent antibacterial efficacy against MRSA (97 %) and prevent the development of bacterial resistance. The antibacterial effect is primarily mediated through the secretion of bioactive peptides by B. sub, which not only inhibit MRSA growth but also reduce the likelihood of resistance development. Meanwhile, the probiotic hydrogel has a greater ability to induce M2 polarization of macrophages and promote angiogenesis, resulting in enhanced osteogenic differentiation in bone marrow mesenchymal stem cells (BMSCs) and thus enhancing bone regeneration. This engineered probiotic hydrogel offers a promising strategy by simultaneously combating bacterial infection and enhancing osteogenic differentiation for chronic osteomyelitis.

A remotely controlled nanotherapeutic with immunomodulatory property for MRSA-induced bone infection

Osteomyelitis is a deep bone tissue infection caused by pathogenic microorganisms, with the primary pathogen being methicillin-resistant Staphylococcus aureus (MRSA). Due to the tendency of the infection site to form biofilms that shield drugs and immune cells to kill bacteria, combined with the severe local inflammatory response causing bone tissue destruction, the treatment of osteomyelitis poses a significant challenge. Herein, we developed a remotely controlled nanotherapeutic (TLBA) with immunomodulatory to treat MRSA-induced osteomyelitis. TLBA, combined with baicalin and gold nanorods, is positively charged to actively target and penetrate biofilms. Near-infrared light (808 nm) triggers spatiotemporal, controllable drug release, while bacteria are eliminated through synergistic interaction of non-antibiotic drugs and photothermal therapy, enhancing bactericidal efficiency and minimizing drug resistance. TLBA eliminated nearly 100 % of planktonic bacteria and dispersed 90 % of biofilms under NIR light stimulation. In MRSA-induced osteomyelitis rat models, laser irradiation raised the infection site temperature to 50 °C, effectively eradicating bacteria, promoting M2 macrophage transformation, inhibiting bone inflammation, curbing bone destruction, and fostering bone tissue repair. In summary, TLBA proposes a more comprehensive treatment strategy for the two characteristic pathological changes of bacterial infection and bone tissue damage in osteomyelitis.

Antimicrobial Phenolic Materials: From Assembly to Function

Infectious diseases pose considerable challenges to public health, particularly with the rise of multidrug-resistant pathogens that globally cause high mortality rates. These pathogens can persist on surfaces and spread in public and healthcare settings. Advances have been made in developing antimicrobial materials to reduce the transmission of pathogens, including materials composed of naturally sourced polyphenols and their derivatives, which exhibit antimicrobial potency, broad-spectrum activity, and a lower likelihood of promoting resistance. This review provides an overview of recent advances in the fabrication of antimicrobial phenolic biomaterials, where natural phenolic compounds act as active antimicrobial agents or encapsulate other antimicrobial agents (e.g., metal ions, antimicrobial peptides, natural biopolymers). Various forms of phenolic biomaterials synthesized through these two strategies, including antimicrobial particles, capsules, hydrogels, and coatings, are summarized, with a focus on their application in wound healing, bone repair and regeneration, oral health, and antimicrobial coatings for medical devices. The potential of these advanced phenolic biomaterials provides a promising therapeutic approach for combating antimicrobial-resistant infections and reducing microbial transmission.

Investigation of characteristics and classification for swine vertebral osteomyelitis in South Korea

BACKGROUND

Vertebral osteomyelitis (VO) is a major cause of condemnation in swine slaughterhouses, leading to economic losses for farmers. This study aimed to investigate the characteristics and classification of VO cases in South Korean slaughterhouses, focusing on their relationship with pyemia and their potential to reduce unnecessary total condemnation.

RESULTS

Our findings confirmed that swine VOs are often associated with tail-biting injuries, particularly in the posterior vertebrae, underscoring tail biting as a prominent risk factor. Trueperella pyogenes were the most prevalent among the bacterial pathogens, while additional less common bacteria were also identified, warranting further research on their potential pathogenic roles. According to the VO classification scheme used in this study, 75% of the 20 VO cases examined were classified as acute VO, whereas the remaining cases were chronic. It was revealed that only 10% (2/20) of the VO cases were in a state of pyemia at the time of slaughter (true pyemia) and these true pyemia cases were found only in the acute VOs.

CONCLUSIONS

The VO classification scheme tested in this study demonstrated high sensitivity (100%), indicating its robustness in avoiding false negatives and ensuring food safety. Of the carcasses that could have undergone unnecessary condemnation, 22.2% were excluded. The results indicate that the VO classification scheme is recommended as a measure to reduce unnecessary total condemnation induced by VO.

Antimicrobial photodynamic therapy with 5-aminolevulinic acid plus antibiotics: a promising treatment for tibial osteomyelitis caused by drug-resistant bacteria

Osteomyelitis is a severely destructive bone disease caused by microbial infections, and currently, no available treatment effectively controls the infection. 5-Aminolevulinic acid is a second-generation endogenous photosensitizer. This study investigated the efficacy of 5-aminolevulinic acid-mediated photodynamic therapy (ALA-PDT) in combination with antibiotics in the treatment of tibial osteomyelitis in rabbits. The results illustrated that ALA-PDT alone and in combination of antibiotics displayed significant efficacy in treating osteomyelitis. Animals in the photodynamic antimicrobial chemotherapy (PACT) + antibiotics group exhibited a higher survival rate, an improved overall mental status, a lower localized infection rate, and reduced Tang Hui and Norden scores (P < 0.05), indicating less severe bone destruction. Histologically, more strips of lamellar new bone formation and more pronounced periosteal hyperplasia were noted in the PACT + antibiotics group. Micro-computed tomography illustrated that the structural integrity of cortical bone and cancellous bone structure had better continuity and clearer display in the PACT + antibiotics group than in the other groups, and the periosteal reaction in the modeling area was the most obvious. Bone parameter analysis indicated that trabecular thickness, bone volume, and trabeculae volume were significantly higher in the PACT + antibiotics group than in the model and antibiotics groups (P < 0.05). Additionally, trabecular separation was significantly lower in the PACT + antibiotic group than in the other groups (P < 0.05). These findings suggest that the combination of ALA-PDT and antibiotics has a sensitizing therapeutic effect, offering a promising strategy for the clinical treatment of osteomyelitis.

Synergistic photothermal-sonodynamic therapy for antibacterial and immune reprogramming in chronic osteomyelitis

The development of antibiotic resistance and inadequate immune response in chronic inflammation pose significant challenges in treating chronic osteomyelitis. As accepted non-antibiotic antimicrobial therapies, sonodynamic therapy (SDT) and photothermal therapy (PTT) are recognized for their effectiveness in eliminating bacteria and promoting tissue repair, rendering them promising therapeutic strategies for treating bacterial infections and preventing the emergence of drug-resistant bacteria. However, the antimicrobial action and efficacy in promoting tissue repair depend on the activation status of the host immune system. In this study, by encapsulating horseradish peroxidase (HRP)-loaded gold/polydopamine (PDA) nanoparticles within DOTAP/DOPE cationic liposomes (DLPs), a novel multifunctional nanocatalyst, Au/PDA/HRP@DLP (APH@DLP), was developed to achieve antimicrobial effects and immunological reprogramming of chronic osteomyelitis through synergistic SDT and PTT. The impact on immune activation was investigated by assessing the anti-infective and healing effects in osteomyelitis rat models. The release of bacterial-associated antigens during treatment serves as an in situ vaccine, activating antigen-presenting cells and further stimulating adaptive immunity, while also inducing immune memory that significantly reduces the risk of recurrence. Additionally, macrophage phenotypic transformation during SDT and PTT facilitates tissue repair. This study highlights the role of immune activation in SDT/PTT-based antimicrobial therapy and suggests new strategies for treating chronic osteomyelitis.

Substance P Augments Chemokine Production by Staphylococcus aureus Infected Murine Osteoclasts

Staphylococcal osteomyelitis is a serious infection of the bone and joints characterized by progressive inflammatory tissue damage and leukocyte recruitment leading to net bone loss. Resident bone cells are capable of recognizing Staphylococcus aureus and initiating an inflammatory immune response that recruits leukocytes and alters bone homeostasis. Importantly, bone tissue is richly innervated with substance P containing nerve fibers and we have previously shown that this neuropeptide can augment the inflammatory responses of both osteoblasts and osteoclasts to S. aureus infection via neurokinin-1 receptors (NK-1R). Here, we have extended these studies by demonstrating that pharmacological inhibition of NK-1R ameliorates disease severity in a mouse model of staphylococcal osteomyelitis. This effect was associated with a significant reduction in leukocyte-attracting chemokine production following infection and reduced local levels of osteoclast and neutrophil activity. We then assessed the effect of S. aureus infection on bone-marrow derived osteoclast gene expression in the absence or presence of substance P. We determined that infection upregulates osteoclast expression of mRNAs encoding inflammatory mediators that include the neutrophil-attracting chemokines identified in vivo. Importantly, we found that, while substance P has no effect on chemokine mRNA expression in infected cells, this neuropeptide significantly increases the release of these chemokines by S. aureus challenged osteoclasts but not osteoblasts. Together, these data further support the ability of substance P to exacerbate inflammatory damage in staphylococcal osteomyelitis and indicate that this effect may be due, in part, to an augmentation of osteoclast immune responses that promote leukocyte recruitment.

Accelerating repair of infected bone defects through post-reinforced injectable hydrogel mediated antibacterial/immunoregulatory microenvironment at bone-hydrogel interface

Functional injectable hydrogel (IH) is promising for infected bone defects (IBDs) repair, but how to endow it with desired antibacterial/immunoregulatory functions as well as avoid mechanical failures during its manipulation has posed as main challenges. Herein, rosmarinic acid (RosA), a natural product with antibacterial/immunoregulatory activities, was utilized to develop a FCR IH through forming phenylboronic acid ester bonds with 4-formylphenyl phenylboronic acid (4-FPBA) grafted chitosan (CS) (FC). After being applied to the IBD site, the FCR IH was then injected with tobramycin (Tob) solution, another alkaline antibacterial drug, to induce in situ crystallization of the FC, endowing the resultant FCRT hydrogel with adaptively enhanced mechanical strength and structural stability. Owing to the specific structural composition, the FCRT hydrogel could sustainedly release Tob and RosA molecules at the IBD interface, effectively eliminating in situ bacterial infection. In addition, the released RosA molecules also induced the M2 polarization of in situ macrophages (Mφ), which was identified to be related to the NF-κB and PI3K-AKT pathways, therefore promoting the osteogenic differentiation of in situ bone marrow stromal cells (BMSCs). Due to the simultaneous antibacterial/osteo-immunoregulatory microenvironment at the IBD interface, the repair of IBDs was proved to be greatly accelerated by the FCRT hydrogel.

Programmed Transformation of Osteogenesis Microenvironment by a Multifunctional Hydrogel to Enhance Repair of Infectious Bone Defects

Repair of infectious bone defects remains a serious problem in clinical practice owing to the high risk of infection and excessive reactive oxygen species (ROS) during the early stage, and the residual bacteria and delayed Osseo integrated interface in the later stage, which jointly creates a complex and dynamic microenvironment and leads to bone non-union. The melatonin carbon dots (MCDs) possess antibacterial and osteogenesis abilities, greatly simplifying the composition of a multifunctional material. Therefore, a multifunctional hydrogel containing MCDs (GH-MCD) is developed to meet the multi-stage and complex repair needs of infectious bone injury in this study. The GH-MCD can intelligently release MCDs responding to the acidic microenvironment to scavenge intracellular ROS and exhibit good antibacterial activity by inducing the production of ROS in bacteria and inhibiting the expression of secA2. Moreover, it has high osteogenesis and long-lasting antimicrobial activity during bone repair. RNA-seq results reveal that the hydrogels promote the repair of infected bone healing by enhancing cellular resistance to bacteria, balancing osteogenesis and osteoclastogenesis, and regulating the immune microenvironment. In conclusion, the GH-MCD can promote the repair of infectious bone defects through the programmed transformation of the microenvironment, providing a novel strategy for infectious bone defects.

Functionalized Bone Implant Inspired by Lattice Defense Strategy: Grid Management, Precise and Effective Multiple-Prevention of Osteomyelitis Recurrence and Promote Bone Regeneration

Osteomyelitis with a high recurrence rate. Timely-prevention can avoid severe consequence and death. However, conventional drug response-release has the disadvantages of unnecessary release and waste, causing ineffective prevention. Inspired by "Lattice-defense technology", gridding lesion areas and constructing a "Triggered-precise response-release system" may be an effective multiple-prevention method. Here, a new strict pH-triggered response drug controlled-release mechanism was proposed innovatively to construct a "Triggered-precise response-release system" and achieve multiple-effective prevention. PO4 3--Ce3+ strict pH responsive release system is prepared through simultaneous hydration reaction of solution-polymerization and compounded in bone-implant. The dispersed system only targets micro-interface contact areas, achieving gridded management of the lesion site. In a normal environment, Ce3+ is captured by PO4 3- and kept electrostatic-attraction balance, ensuring the zero-concentration Ce3+ release continuously. Once osteomyelitis recurs and pH decrease, H+ at the interface will combine with PO4 3- under electrostatic drive and disrupt potential balance, achieving the release of Ce3+ only when the infection recurs. In vivo experiments was confirmed effective prevention and excellent promote bone regeneration. The adoption of "Lattice defense technology" has achieved accuracy spatiotemporal of drug delivery. Even if other lesion sites unfortunately recur again, effective-prevention can be guaranteed. Bone-implant show great potential in preventing osteomyelitis.

Infections in sickle cell disease

Sickle cell disease (SCD) is one of the commonest severe inherited disorders in the world. Infection accounts for a significant amount of the morbidity and mortality, particularly in sub-Saharan Africa, but is relatively poorly studied and characterized. Patients with SCD have significant immunodeficiency and are more likely to suffer severe and life-threatening complications of infection, and additionally infections can trigger complications of SCD itself. Those with more severe forms of SCD have functional asplenia from a very early age, which accounts for much of the morbidity in young children, particularly invasive infections from encapsulated bacteria including Streptococcus pneumoniae, Haemophilus influenzae, Salmonella typhi and meningococcal disease. Additionally, there are other defects in immune function in SCD, associated with anemia, tissue infarction and impaired adaptive immunity. Complications of infections in SCD include acute chest syndrome, acute painful episodes, osteomyelitis, meningitis, urinary tract infections, overwhelming sepsis and death. Viral infections cause significant morbidity, particularly severe anemia associated with parvovirus, and to a lesser extent other infections such as influenza and coronavirus disease 2019. The relationship between malaria and SCD is complicated and discussed in this review. Unlike many of the genetic risk factors for poor outcomes in SCD, it is theoretically possible to modify the risks associated with infections with established public health measures. These include the provision of vaccination, prophylactic antibiotics and access to clean water and mosquito avoidance, although current financial restraints and political priorities have made this difficult.

Calcium phosphate-based anti-infective bone cements: recent trends and future perspectives

Bone infection remains a challenging condition to fully eradicate due to its intricate nature. Traditional treatment strategies, involving long-term and high-dose systemic antibiotic administration, often encounter difficulties in achieving therapeutic drug concentrations locally and may lead to antibiotic resistance. Bone cement, serving as a local drug delivery matrix, has emerged as an effective anti-infective approach validated in clinical settings. Calcium phosphate cements (CPCs) have garnered widespread attention and application in the local management of bone infections due to their injectable properties, biocompatibility, and degradability. The interconnected porous structure of calcium phosphate particles, not only promotes osteoconductivity and osteoinductivity, but also serves as an ideal carrier for antibacterial agents. Various antimicrobial agents, including polymeric compounds, antibiotics, antimicrobial peptides, therapeutic inorganic ions (TIIs) (and their nanoparticles), graphene, and iodine, have been integrated into CPC matrices in numerous studies aimed at treating bone infections in diverse applications such as defect filling, preparation of metal implant surface coatings, and coating of implant surfaces. Additionally, for bone defects and nonunions resulting from chronic bone infections, the utilization of calcium phosphate-calcium sulfate composite multifunctional cement loaded with antibacterial agents serves to efficiently deal with infection, stimulate new bone formation, and attain an optimal degradation rate of the bone cement matrix. This review briefly delves into various antibacterial strategies based on calcium phosphate cement for the prevention and treatment of bone infections, while also discussing the application of calcium phosphate-calcium sulfate composites in the development of multifunctional bone cement against bone infections.

When E. coli strikes: a necropsy analysis of a juvenile giraffe's fatal infection

BACKGROUND

As bacterial infections pose a major health risk to captive populations, disease prevention and management play a crucial role in the ex situ conservation of giraffes (Giraffa camelopardalis). This study describes the case of a giraffe that developed septicemia after an umbilical cord infection caused by Escherichia coli. To our knowledge, pathological changes in diseased giraffes caused by E. coli, which is an opportunistic pathogenic organism, have not been reported. This is the first report presenting an analysis of necropsies and subsequent microbiological investigations.

CASE PRESENTATION

The baby giraffe's mother died shortly after birth, so it had to be fed milk powder. The giraffe was healthy at first but developed symptoms like depression, loss of appetite, and lameness at 8 days old. At 14 days of age, the juvenile giraffe showed astasia and gradually died, with a disease course of 7 days. Postmortem examination revealed opisthotonus and navel swelling. Serofibrinous arthritis, serofibrinous necrotizing inflammation of periarticular soft tissue, serous omphalitis, and severe adventitia hemorrhage of the umbilical artery were observed. Severe serofibrinous pericarditis, pleuritis, and peritonitis were also observed. The interstitium of the pulmonary lobule widened because it was filled with a pale yellow translucent gelatinous exudate. Histopathologically, the calf had diffuse serous interstitial pneumonia, serous necrotizing umbilical arteritis, degenerative hepatitis with mild fibrosis, degenerative nephritis, hemorrhagic lymphadenitis, necrotizing enteritis, and necrotizing thyroiditis. Blue-stained clumps of bacteria of varying sizes and neutrophil infiltration were scattered or diffused in the interstitial connective tissue and edematous serosa of all tissues and organs, as well as in small vessels and lymphatic vessels, which were filled with many neutrophils (lymphatic spread). Single gram-negative Escherichia coli were cultured from all tissues of the animal. Polymerase chain reaction results of 16S rRNA of the isolated Escherichia coli had 99.79% homology to KJB03889.1.

CONCLUSIONS

The gross, histopathologic, microscopic, and polymerase chain reaction sequencing features reported in a juvenile giraffe were consistent with colibacillosis, which is a rare disease of giraffes. The gross, histopathologic, microscopic, and polymerase chain reaction sequencing features reported in a juvenile giraffe. This case serves as a paradigmatic illustration of a giraffe suffering from neglect and inadequate treatment, leading to severe consequences. In instances of giraffe Escherichia coli septicemia, it is imperative to thoroughly assess for underlying diseases, particularly in the absence of obvious predisposing factors. The rise of multidrug resistant organisms has constrained the efficacy of empirical antibiotic treatment, highlighting the importance of promptly conducting culture and sensitivity testing and employing antibiotic therapy guided by susceptibility results.

In Situ Application of Berberine-Loaded Liposomes on the Treatment of Osteomyelitis

Osteomyelitis is a major challenge in global healthcare, as it requires the simultaneous management of bone defects and bacterial infections, which poses considerable difficulties for orthopedic clinicians. In this study, we developed berberine liposome-modified bone cement specifically aimed at treating osteomyelitis induced by Staphylococcus aureus. We characterized the physical properties of this modified bone cement, conducted in vitro antibacterial assays to evaluate its efficacy in eradicating Staphylococcus aureus biofilm, established an in vivo rat model of osteomyelitis, and performed histopathological assessments alongside micro-CT analysis of bone parameters. The results indicated that the berberine liposome-modified bone cement exhibited favorable biodegradability and sustained-release characteristics, with a drug release rate of more than 90% within 14 days, while effectively eliminating bacterial biofilm with a biofilm eradication rate of up to 80% and facilitating bone repair with a bone volume fraction of 80%. This innovative treatment demonstrated both safety and efficacy in addressing tibial osteomyelitis in rats, thereby offering novel insights and methodologies for clinical interventions against osteomyelitis.

Do not treat ghosts: anti-methicillin-resistant Staphylococcus aureus (MRSA) therapy in osteomyelitis without identified MRSA

Objective

To compare the clinical outcomes of patients with lower limb osteomyelitis (LLOM) and negative methicillin-resistant Staphylococcus aureus (MRSA) cultures treated with anti-MRSA therapy (AMT) versus those treated with no-anti-MRSA therapy (NAMT).

Design

Retrospective cohort study.

Patients

Hospitalized adult (≥18 yr of age) patients admitted to multiple tertiary referral centers in a single healthcare system between April 1, 2017 and April 1, 2023, with LLOM and planned intravenous antibiotics for at least four weeks.

Methods

Electronic medical records were queried for demographic information, admission dates, treatment strategies, imaging and culture results, and discharge diagnoses. Descriptive statistics measured baseline characteristics, imaging, and culture results.

Results

Out of 473 patients, 64 met the inclusion criteria and 409 were excluded. Of the 64 patients, 26 (40%) had AMT and 38 (59%) had NAMT. A larger but statistically insignificant portion of patients in the NAMT cohort failed therapy (23% AMT vs 32% NAMT, P = 0.325). However, hospital readmission for LLOM within 180 days of antibiotic completion (46.2% vs 47%, P = 0.92), hospital length of stay (median (IQR): 6 (5-9) d vs 7 (5-12.5) d, P = 0.285), incidence of new renal replacement therapy initiation (0% vs 2.6%, P = 0.594), creatinine kinase levels (0 vs 2.6%, P = 0.594), and drug-induced immune thrombocytopenia (0% vs 5.3% P = 0.349) were comparable between the two cohorts.

Conclusions

Treatment failure rates and adverse events did not differ significantly among patients with LLOM treated with AMT or NAMT. Further investigation of determinants of clinical failures in LLOM may help optimize overall treatment.

Staphylococcus aureus in Inflammation and Pain: Update on Pathologic Mechanisms

Staphylococcus aureus (S. aureus) is a Gram-positive bacterium of significant clinical importance, known for its versatility and ability to cause a wide array of infections, such as osteoarticular, pulmonary, cardiovascular, device-related, and hospital-acquired infections. This review describes the most recent evidence of the pathogenic potential of S. aureus, which is commonly part of the human microbiota but can lead to severe infections. The prevalence of pathogenic S. aureus in hospital and community settings contributes to substantial morbidity and mortality, particularly in individuals with compromised immune systems. The immunopathogenesis of S. aureus infections involves intricate interactions with the host immune and non-immune cells, characterized by various virulence factors that facilitate adherence, invasion, and evasion of the host's defenses. This review highlights the complexity of S. aureus infections, ranging from mild to life-threatening conditions, and underscores the growing public health concern posed by multidrug-resistant strains, including methicillin-resistant S. aureus (MRSA). This article aims to provide an updated perspective on S. aureus-related infections, highlighting the main diseases linked to this pathogen, how the different cell types, virulence factors, and signaling molecules are involved in the immunopathogenesis, and the future perspectives to overcome the current challenges to treat the affected individuals.

Clinical and epidemiological differences in staphylococcal osteoarticular infections: insights for developing hospital-based infection control interventions

PURPOSE

Osteoarticular infections (OAI) are serious clinical conditions with Staphylococcus aureus and Coagulase-negative Staphylococcus (CoNS) responsible for up to two-thirds of cases. This work aimed to compare the epidemiological, clinical, and microbiological characteristics of OAI caused by S. aureus versus CoNS to aid in clinical management and infection control strategies.

METHODS

A single-centre retrospective study was performed at the Centro Hospitalar e Universitário de Coimbra for the period of January 2011 to December 2021. A total of 458 cases of OAI were gathered. Data was retrieved from medical records and statistical analysis was performed with SPSS.

RESULTS

S. aureus accounted for 60.7% of infections, followed by S. epidermidis (29.9%). Independent risk factors for S. aureus infections included being male (p < 0.001; OR = 0.47) and a history of osteomyelitis (p < 0.001; OR = 0.18). In contrast, CoNS infections were associated with older age (p = 0.018), carrying a prosthetic device (p < 0.001; OR = 2.92), and a prior periprosthetic infection (p = 0.023; OR = 1.86). Both groups exhibited significant antimicrobial resistance, with CoNS showing greater resistance to gentamicin, linezolid, teicoplanin and trimethoprim-sulfamethoxazole, while S. aureus was more commonly resistant to clindamycin.

CONCLUSION

Our findings show the distinct characteristics of OAI caused by S. aureus and CoNS, highlighting the need for targeted risk factor management and tailored empiric antibiotic therapy to reduce incidence and improve outcomes.

Collagen silver-doped hydroxyapatite scaffolds reinforced with 3D printed frameworks for infection prevention and enhanced repair of load-bearing bone defects

Osteomyelitis, a severe bone infection, is an extremely challenging complication in the repair of traumatic bone defects. Furthermore, the use of long-term high-dose antibiotics in standard treatment increases the risks of antibiotic resistance. Herein, an antibiotic-free, collagen silver-doped hydroxyapatite (coll-AgHA) scaffold reinforced with a 3D printed polycaprolactone (PCL) framework was developed with enhanced mechanical properties to be used in the repair of load-bearing defects with antimicrobial properties as a preventative measure against osteomyelitis. The AgHA particles were fabricated in varying Ag doses and loaded within freeze-dried collagen scaffolds at two concentrations. The optimised Ag dose (1.5 mol% Ag) and AgHA concentration (200 wt%) within the collagen scaffold demonstratedin vitroosteogenic and antibacterial properties againstS. aureus (S. aureus),the main causative pathogen of osteomyelitis. The addition of the PCL framework to the coll-AgHA scaffolds significantly enhanced the compressive modulus from 4 to 12 MPa while maintaining high porosity as well as both pro-osteogenic and antibacterial properties. The reinforced coll-AgHA scaffolds were implantedin vivoand demonstrated enhanced bone repair, significantly greater vessel formation, and calcified tissue in a load-bearing critical sized defect in rats. Taken together, these results confirm the capacity of this novel biomaterial scaffold as a preventative measure against infection in bone repair for use in load-bearing defects, without the use of antibiotics.

Exosomes derived from bone marrow mesenchymal stem cells induce the proliferation and osteogenic differentiation and regulate the inflammatory state in osteomyelitis in vitro model

Chronic osteomyelitis is a chronic bone infection characterized by progressive osteonecrosis and dead bone formation, which is closely related to persistent infection and chronic inflammation. Exosomes derived from bone marrow-derived mesenchymal stem cells (BMSC) play an important role in bone tissue regeneration and the modulation of inflammatory processes. However, their role and mechanism of action in osteomyelitis have not been reported so far. This paper explores the potential effect of BMSC-derived exosomes on osteomyelitis in vitro model with the aim of providing a theoretical basis for the treatment of osteomyelitis in the future. In this study, exosomes were isolated and extracted from BMSCs and identified. MC3T3-E1 cells were treated with Staphylococcal protein A (SPA) to establish an in vitro model of osteomyelitis. Next, the effects of BMSC-derived exosomes on cell proliferation, apoptosis, angiogenesis, and autophagy in MC3T3-E1 cells treated with SPA were evaluated. Results showed that the proliferation ability of MC3T3-E1 cells increased after co-culture with BMSC-derived exosomes. Moreover, exosomes induced autophagy and osteogenic differentiation in MC3T3-E1 cells. The mRNA and protein levels of factors related to proliferation, differentiation, apoptosis, autophagy, and angiogenesis including β-Catenin, Runx2, Bcl-2, VEGFA, and Beclin-1 upregulated in SPA-treated MC3T3-E1 cells, whereas the levels of inflammatory cytokines including TNF-α, IL-1β, and IL-6 decreased in the supernatant. The results showed that exosomes derived from BMSCs may participate in the attenuation of osteomyelitis by inducing proliferation and osteogenic differentiation and regulating the inflammatory state in bone cells.

Programmed surface platform orchestrates anti-bacterial ability and time-sequential bone healing for implant-associated infection

Implant-associated infection (IAI) has become an intractable challenge in clinic. The healing of IAI is a complex physiological process involving a series of spatiotemporal connected events. However, existing titanium-based implants in clinic suffer from poor antibacterial effect and single function. Herein, a versatile surface platform based on the presentation of sequential function is developed. Fabrication of titania nanotubes and poly-γ-glutamic acid (γ-PGA) achieves the efficient incorporation of silver ions (Ag+) and the pH-sensitive release in response to acidic bone infection microenvironment. The optimized PGA/Ag platform exhibits satisfactory biocompatibility and converts macrophages from pro-inflammatory M1 to pro-healing M2 phenotype during the subsequent healing stage, which creates a beneficial osteoimmune microenvironment and promotes angio/osteogenesis. Furthermore, the PGA/Ag platform mediates osteoblast/osteoclast coupling through inhibiting CCL3/CCR1 signaling. These biological effects synergistically improve osseointegration under bacterial infection in vivo, matching the healing process of IAI. Overall, the novel integrated PGA/Ag surface platform proposed in this study fulfills function cascades under pathological state and shows great potential in IAI therapy.

MRSA septic arthritis of the pubic symphysis post vaginal delivery: A case report and literature review

INTRODUCTION AND IMPORTANCE

Septic arthritis of the pubic symphysis is a rare postpartum infection characterized by severe pelvic pain, fever, and elevated inflammatory markers. It is often underdiagnosed due to its rarity and nonspecific symptoms. It is commonly caused by Staphylococcus aureus, with methicillin-resistant Staphylococcus aureus (MRSA) septic being a rare but concerning pathogen.

CASE PRESENTATION

We report the case of a 36-year-old woman who developed septic arthritis of the pubic symphysis caused by MRSA after spontaneous vaginal delivery.

CLINICAL DISCUSSION

Differentiating between diastasis and septic arthritis of the pubic symphysis is crucial for treatment. Noninfective pubic osteitis can mimic septic arthritis, presenting a diagnostic challenge. Imaging, laboratory data, and cultures are essential for accurate diagnosis. MRSA colonisation during pregnancy and postpartum trauma may facilitate infection. MRI is the most sensitive imaging modality for early detection and monitoring.

CONCLUSION

Septic arthritis of the pubic symphysis secondary to MRSA is a rare cause of postpartum pelvic pain. Prompt diagnosis and treatment are essential for favourable outcomes.

Probiotic biofilm modified scaffolds for facilitating osteomyelitis treatment through sustained release of bacteriophage and regulated macrophage polarization

Osteomyelitis has gradually become a catastrophic complication in orthopedic surgery due to the formation of bacterial biofilms on the implant surface and surrounding tissue. The therapeutic challenges of antibiotic resistance and poor postoperative osseointegration provide inspiration for the development of bioactive implants. We have strategically designed bioceramic scaffolds modified with Lactobacillus reuteri (LR) and bacteriophages (phages) to achieve both antibacterial and osteogenic effects. Leveraging the tendency of bacteria to adhere to the surface of implants, bioceramics have been modified with LR biofilm to promote bone repair. The LR biofilm, sterilized by pasteurization, prevents sepsis caused by live bacteria and is biocompatible with phages. Phages, being natural enemies of bacteria, not only effectively kill bacteria and inhibit biofilm formation but also readily adsorb onto the surface of bioceramics. Hence, this scaffold, loaded with a phage cocktail, lysates specific bacterial populations, namely Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). More importantly, the inactivated LR biofilm stimulates macrophages RAW264.7 to polarize towards an anti-inflammatory M2 phenotype, creating an immune microenvironment favorable for inducing osteogenic differentiation of rat mesenchymal stem cells in vitro. In a rat model of infectious cranial defects, the scaffold not only effectively eliminated S. aureus and alleviated associated inflammation but also mediated macrophage-mediated immunoregulation, thus resulting in effective osteogenesis. Collectively, these multifunctional modified scaffolds offer an integrated approach to both bacterium elimination and bone repair, presenting a new strategy for bioactive implants in the clinical management of osteomyelitis.

Antibiotic-eluting scaffolds with responsive dual-release kinetics facilitate bone healing and eliminate S. aureus infection

Osteomyelitis (OM) is a progressive, inflammatory infection of bone caused predominately by Staphylococcus aureus. Herein, we engineered an antibiotic-eluting collagen-hydroxyapatite scaffold capable of eliminating infection and facilitating bone healing. An iterative freeze-drying and chemical crosslinking approach was leveraged to modify antibiotic release kinetics, resulting in a layered dual-release system whereby an initial rapid release of antibiotic to clear infection was followed by a sustained controlled release to prevent reoccurrence of infection. We observed that the presence of microbial collagenase accelerated antibiotic release from the crosslinked layer of the scaffold, indicating that the material is responsive to microbial activity. As exemplar drugs, vancomycin and gentamicin-eluting scaffolds were demonstrated to be bactericidal, and supported osteogenesis in vitro. In a pilot murine model of OM, vancomycin-eluting scaffolds were observed to reduce S. aureus infection within the tibia. Finally, in a rabbit model of chronic OM, gentamicin-eluting scaffolds both facilitated radial bone defect healing and eliminated S. aureus infection. These results show that antibiotic-eluting collagen-hydroxyapatite scaffolds are a one-stage therapy for OM, which when implanted into infected bone defects simultaneously eradicate infection and facilitate bone tissue healing.

Emodin Enhanced Microwave-Responsive Heterojunction with Powerful Bactericidal Capacity and Immunoregulation for Curing Bacteria-Infected Osteomyelitis

Eradication of osteomyelitis caused by bacterial infections is still a major challenge. Microwave therapy has the inherent advantage of deep penetration in curing deep tissue infections. However, the antibacterial efficiency of sensitizers is limited by the weak energy of microwaves. Here, a hybrid heterojunction system (Fe3O4/CuS/Emo) is designed for curing bacterially infected osteomyelitis. As an enhanced microwave sensitizer, it shows supernormal microwave response ability. Specifically, Fe3O4 acts as a matrix to mediate magnetic loss. After CuS loading, the heterogeneous interface forms induce significant interfacial polarization, which increasing dielectric loss. On the basis of the heterojunction formed by the two semiconductors, emodin is innovatively introduced to modify it. This integration not only accelerates the movement of charge carriers but also enhances polarization loss due to the numerous functional groups present on the surface. This further optimizes the microwave thermal and catalytic response. In addition, the unique anti-inflammatory properties of emodin confer the ability of hybrid heterojunction to regulate the immune microenvironment. In vivo studies reveal that heterojunction modified by emodin programmed elimination of bacteria and regulation of the immune microenvironment. It offers a revolutionary approach to the treatment of bacterial osteomyelitis.

Efficacy of pH-Responsive Surface Functionalized Titanium Screws in Treating Implant-associated S. aureus Osteomyelitis with Biofilms Formation

Implant-associated Staphylococcus aureus (S. aureus) osteomyelitis (IASO) leads to high orthopedic implant failure rates due to the formation of Staphylococcal abscess community within the bone marrow and bacterial colonization in the osteocyte lacuno-canalicular network (OLCN). To address this, antimicrobial peptides (HHC36)-loaded titania nanotubes (NTs) are developed on titanium screws (Ti-NTs-P-A), which integrate pH-responsive polymethacrylic acid to control HHC36 release for eradicating bacteria in IASO. Colony-forming unit assay confirmed that Ti-NTs-P-A screws maintained sustainable antibacterial effectiveness, killing over 65% of S. aureus even after multiple bacterial solution replacements. Notably, Ti-NTs-P-A screws exhibit significant pH-responsive HHC36 release behavior and bactericidal activity, consistent with the phenotype of peptides-killed bacteria from scanning electron microscopy. Transcriptome sequencing results reveal that Ti-NTs-P-A screws interfered with ribosome formation and disrupted the arginine biosynthesis, which is crucial for bacterial survival in acidic environments. In the non-infected implant model, the bone-implant contact ratio of the Ti-NTs-P-A screw is 2.3 times that of the clinically used titanium screw. In an IASO model, Ti-NTs-P-A screws effectively eradicated bacteria within the OLCN, achieving an 80% infection control rate and desirable osteointegration. Collectively, Ti-NTs-P-A screws with pH-responsive antibacterial properties exhibit great potential for eradicating bacteria and achieving osseointegration in IASO.

Novel antibiotics against Staphylococcus aureus without detectable resistance by targeting proton motive force and FtsH

The increased prevalence of methicillin-resistant Staphylococcus aureus (MRSA) and its biofilms poses a great threat to human health. Especially, S. aureus-related osteomyelitis was hardly cured even by conventional antibiotics combined with surgical treatment. The development of novel structural antibiotics is urgently needed. By high-throughput screening and rational design, we identified a small molecule C218-0546 and its optimized analog STK848198 with great antimicrobial potential against MRSA avoiding resistance occurrence. And significant synergistical antimicrobial effects were found between the molecules and conventional antibiotics. Mechanisms studies by transcriptomics, fluorescent probes, molecule dynamics, and plasma surface resonance indicated that the proton motive force as well as FtsH are the main potential targets of these molecules. The compounds exhibited excellent in vivo pharmacokinetics, toxicity profiles, and antimicrobial activities in the abscess model as well as the peritonitis-sepsis model. In addition, STK848198 was found to be effective against MRSA biofilms by interacting with the quorum sensing system. STK848198 also showed in vivo efficacy in the periprosthetic joint infection model. In all, our study identified a class of antimicrobials with novel scaffolds that could be potential alternatives for the treatment of MRSA and its biofilm-related infections.

A Multifunctional Cobalt-Containing Implant for Treating Biofilm Infections and Promoting Osteointegration in Infected Bone Defects Through Macrophage-Mediated Immunomodulation

Treating bone infections and ensuring bone recovery is one of the major global problems facing modern orthopedics. Prolonged antibiotic use may increase the risk of antimicrobial resistance, and inflammation caused by biofilms can obstruct tissue healing, making bone infection treatment even more challenging. The optimal treatment strategy combines immune response modification to promote osteogenesis with effective bacterial infection removal that does not require long-term antibiotic use. A one-step plasma immersion ion implantation approach is used to create titanium alloy implants incorporating cobalt. According to experimental findings, cobalt-containing titanium implants exhibit improved antibacterial activity by efficiently disrupting biofilm formations and reducing Methicillin-resistant Staphylococcus aureus adherence by over 80%. Additionally, the implants exhibit superior anti-inflammatory and osseointegration properties. RNA sequencing analysis reveals the potential mechanism of Co2+ in regulating the polarization of macrophages toward the anti-inflammatory M2 phenotype, which is crucial for creating an immune environment conducive to bone healing. Concurrently, these implants promote osteogenic differentiation while suppressing osteoclast activity, further supporting bone repair. Overall, without exogenous recombinant proteins or antibiotics, the implants effectively eradicate infections and expedite bone repair, offering a novel therapeutic strategy for complex skeletal diseases with clinical promise.

Engineering mesoporous polydopamine-based potentiate STING pathway activation for advanced anti-biofilm therapy

The biofilm-induced "relatively immune-compromised zone" creates an immunosuppressive microenvironment that is a significant contributor to refractory infections in orthopedic endophytes. Consequently, the manipulation of immune cells to co-inhibit or co-activate signaling represents a crucial strategy for the management of biofilm. This study reports the incorporation of Mn2+ into mesoporous dopamine nanoparticles (Mnp) containing the stimulator of interferon genes (STING) pathway activator cGAMP (Mncp), and outer wrapping by M1-like macrophage cell membrane (m-Mncp). The cell membrane enhances the material's targeting ability for biofilm, allowing it to accumulate locally at the infectious focus. Furthermore, m-Mncp mechanically disrupts the biofilm through photothermal therapy and induces antigen exposure through photodynamic therapy-generated reactive oxygen species (ROS). Importantly, the modulation of immunosuppression and immune activation results in the augmentation of antigen-presenting cells (APCs) and the commencement of antigen presentation, thereby inducing biofilm-specific humoral immunity and memory responses. Additionally, this approach effectively suppresses the activation of myeloid-derived suppressor cells (MDSCs) while simultaneously boosting the activity of T cells. Our study showcases the efficacy of utilizing m-Mncp immunotherapy in conjunction with photothermal and photodynamic therapy to effectively mitigate residual and recurrent infections following the extraction of infected implants. As such, this research presents a viable alternative to traditional antibiotic treatments for biofilm that are challenging to manage.

The art of biodegradable polymer design for the treatments against osteomyelitis

Osteomyelitis arises from the incomplete treatment of the external wounds in the healing process, while bacterial infections persist within the bone marrow, leading to abscess formation. Osteomyelitis treatments generally involve three main aspects: rapid bactericidal action, sustained bacteriostasis, and induction of bone regeneration. However, current treatment methods, which often combine surgical debridement with long-term high-dose intravenous antibiotic administration or poly(methyl methacrylate) (PMMA) beads antibiotic therapy, suffer from significant drawbacks and limitations. In an era focused on environmental protection and sustainability, there is potential for biodegradable polymers to replace non-degradable plastic materials to reduce environmental pollution and achieve sustainable development in resources, society, and the economy. With this in mind, this review aims to explore the concept and design of applying various natural biodegradable polymers like gelatin, chitosan, cellulose, etc., and synthetic biodegradable polymers like polylactic acid, poly(lactic-co-glycolic) acid, polycaprolactone, etc. for osteomyelitis treatment, including (1) replacing PMMA with biodegradable polymer beads, (2) biodegradable polymer coatings on medical implants, (3) injectable biodegradable polymer hydrogels, and (4) biodegradable polymers as scaffolds for osteogenic cell growth. This article contributes to understanding and advancing biodegradable polymer applications in biomedicine through a comprehensive review and discussion of these four aspects.

Concentration, pathogenic composition, and exposure risks of bioaerosol in large indoor public environments: A comparative study of urban and suburban areas

Biological contamination in larger indoor environments can lead to the outbreak of various infectious diseases. This study aimed to compare the pollution profiles and associated health risks of airborne microorganisms in different indoor settings between urban and suburban areas by culturing, sequencing, and toxicological evaluation. The results indicated that the average level of culturable bacteria was higher in urban areas (955 ± 259 CFU/m3) compared to suburban areas (850 ± 85 CFU/m3), with the highest concentrations found in the market (2170 ± 798 CFU/m3) and gymnasium (2010 ± 300 CFU/m3). Conversely, the total number of airborne bacteria was higher in classroom (2.09 × 105) and laboratory (1.95 × 105 copies/m3), likely due to the presence of viable but non-culturable cells. Additionally, the concentrations of 0.5-2.0 μm total particles were higher in the market and cafeteria. Dominant airborne genera included Acinetobacter and Pseudomonas for bacteria, Cladosporium and Aspergillus for fungi, as well as Geneviridae and Herpesviridae for viruses. Bacterial and viral diversity and richness were significantly higher in suburban areas compared to urban areas, with distinct viral communities observed in hospital. Cytotoxicity assays revealed lower viability of cells in response to bioaerosols from the library (52.3 %) and laboratory (54.5 %); while lower proliferation rates were found for the cells exposed to bioaerosol from gymnasium (5.4 %) and market (6.0 %), suggesting higher toxicity of these environments. Additionally, bioaerosol exposure may impair cellular innate immunity by increasing the expression of IL-6, IL-8, TNF-α, IFN-γ. Our findings provide valuable information for assessing and controlling bioaerosol-related health risks in indoor environments.

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).

Wireless Optogenetic Targeting Nociceptors Helps Host Cells Win the Competitive Colonization in Implant-Associated Infections

The role of nociceptive nerves in modulating immune responses to harmful stimuli via pain or itch induction remains controversial. Compared to conventional surgery, various implant surgeries are more prone to infections even with low bacterial loads. In this study, an optogenetic technique is introduced for selectively activating peripheral nociceptive nerves using a fully implantable, wirelessly rechargeable optogenetic device. By targeting nociceptors in the limbs of awake, freely moving mice, it is found that activation induces anticipatory immunity in the innervated territory and enhances the adhesion of various host cells to the implant surface. This effect mediates acute immune cell-mediated killing of Staphylococcus aureus on implants and enables the host to win "implant surface competition" against Staphylococcus aureus. This finding provides new strategies for preventing and treating implant-associated infections.

Combining Multiple Spectroscopic Techniques to Reveal the Effects of Staphylococcus aureus Infection on Human Bone Tissues

Osteomyelitis (OM) and periprosthetic joint infections (PJIs) are major public health concerns in Western countries due to increased life expectancy. Infections usually occur due to bacterial spread through fractures, implants, or blood-borne transmission. The pathogens trigger an inflammatory response that hinders bone tissue regeneration. Treatment requires surgical intervention, which involves the precise removal of infected tissue, wound cleansing, and local and systemic antibiotic administration. Staphylococcus aureus (SA) is one of the most common pathogens causing infection-induced OM and PJIs. It forms antimicrobial-resistant biofilms and is frequently found in healthcare settings. In this proof-of-concept, we present an approach based on multiple spectroscopic techniques aimed at investigating the effects of SA infection on bone tissue, as well as identifying specific markers useful to detect early bacterial colonization on the tissue surface. A cross-section of a human femoral diaphysis, with negative-culture results, was divided into three parts, and the cortical and trabecular regions were separated from each other. Two portions of each bone tissue type were infected with SA for one and seven days, respectively. Multiple techniques were used to investigate the impact of the infection on bone tissue, Brillouin-Raman microspectroscopy and attenuated total reflection Fourier transform infrared spectroscopy were employed to assess and develop a new noninvasive diagnostic method to detect SA by targeting the bone of the host. The results indicate that exposure to SA infection significantly alters the bone structure, especially in the case of the trabecular type, even after just one day. Moreover, Raman spectral markers of the tissue damage were identified, indicating that this technique can detect the effect of the pathogens' presence in bone biopsies and pave the way for potential application during surgery, due to its nondestructive and contactless nature.

A three-phase strategy of bionic drug reservoir scaffold by 3D printing and layer-by-layer modification for chronic relapse management in traumatic osteomyelitis

We have developed a novel three-phase strategy for osteomyelitis treatment, structured into three distinct phases: the "strong antimicrobial" phase, the "monitoring and osteogenesis" phase and the "bone repair" phase. To implement this staged therapeutic strategy, we engineered a bionic drug reservoir scaffold carrying a dual-drug combination of antimicrobial peptides (AMPs) and simvastatin (SV). The scaffold integrated a bilayer gel drug-carrying structure, based on an induced membrane and combined with a 3D-printed rigid bone graft using a layer-by-layer modification strategy. The mechanical strength of the composite scaffold (73.40 ± 22.44 MPa) is comparable to that of cancellous bone. This scaffold enables controlled, sequential drug release through a spatial structure design and nanoparticle drug-carrying strategy. AMPs are released rapidly, with the release efficiency of 74.90 ± 8.19 % at 14 days (pH = 7.2), thus enabling rapid antimicrobial therapy. Meanwhile, SV is released over a prolonged period, with a release efficiency of 98.98 ± 0.05 % over 40 days in vitro simulations, promoting sustained osteogenesis and facilitating the treatment of intracellular infections by activating macrophage extracellular traps (METs). The antimicrobial, osteogenic and immunomodulatory effects of the scaffolds were verified through in vitro and in vivo experiments. It was demonstrated that composite scaffolds were able to combat the chronic recurrence of osteomyelitis after debridement, by providing rapid sterilization, stimulating METs formation, and supporting osteogenic repair.

Advances of the multifaceted functions of PSTPIP2 in inflammatory diseases

The complex interaction between the immune system and autoinflammatory disorders highlights the centrality of autoimmune mechanisms in the pathogenesis of autoinflammatory diseases. With the exploration of PSTPIP2, it has been discovered to play an inhibitory role in immune diseases, suggesting its potential utility in the research and treatment of rheumatic diseases. This review outlines the mechanisms of PSTPIP2 in chronic multifocal osteomyelitis (CMO), rheumatoid arthritis (RA), synovitis-acne-pustulosis-hyperostosis-osteitis (SAPHO) syndrome, liver diseases, renal diseases, pressure ulcer sepsis and diabetic obesity. The mechanisms include inhibiting the IL-1β inflammatory responses, NF-κB, ERK phosphorylation etc., promoting Erβ, and modulating the polarization of macrophage to prevent the inflammatory diseases. This review summarized current findings and offered perspectives on future research directions, laying a foundation for applying of PSTPIP2 in inflammatory diseases.

Icariin-Enhanced Osteoclast-Derived Exosomes Promote Repair of Infected Bone Defects by Regulating Osteoclast and Osteoblast Communication

Background

Infected bone defects pose a challenging clinical issue due to an imbalance of osteoclasts (OC) and osteoblasts (OB). Exosomes are crucial for intercellular signaling of OC and OB in bone repair. Icariin, has been shown to regulate the balance between OC and OB. However, the specific mechanisms by which icariin influences exosomes derived from osteoclasts, and subsequently impacts osteoblast activity, remain unclear. This study aims to investigate the effects of icariin-treated osteoclast-derived exosomes (ICA-OC-Exo) on osteoblast function and bone repair in cases of infected bone defects.

Methods

We investigated the exosome profile and localization of multivesicular bodies (MVB) and quantification of intraluminal vesicles (ILVs) in osteoclasts by using transmission electron microscopy. Additionally, the expressions of Rab27A and MITF, which are associated with exosome release, were determined through immunofluorescence staining and Western blot. The profiling of exosomal miRNA expression was conducted via miRNA-sequencing. The effects of ICA-OC-Exo on osteoblast differentiation were determined using RT-qPCR, Western blot, alkaline phosphatase staining. Additionally, ICA-OC-Exo was administered into the localized bone defect of the infected bone rat models, and bone formation was assessed using Micro-CT.

Results

Icariin increased the presence of MVBs in the cytoplasm through modulation of the MITF/Rab27A signaling pathway, resulting in higher number of ICA-OC-Exo compared to OC-Exo. Additionally, miR-331-3p expression in ICA-OC-Exo was found to be elevated compared to OC-Exo. ICA-OC-Exo was observed to stimulate osteoblast function by targeting FGF23, reducing DKK1, and subsequently upregulating ALP. In the in vivo study, ICA-OC-Exo exhibited the capacity to enhance bone healing at the site of a local bone defect following anti-infection treatment.

Conclusion

Icariin enhanced the quantification of OC-Exo and the expression of miRNA-331-3p in OC-Exo, leading to the regulation of osteoblast function via activation of the miRNA-331-3p/FGF23/DKK1 pathway. ICA-OC-Exo demonstrated potential clinical applicability in bone repair of infected bone defects.

Hypoxia-Activated Biodegradable Porphyrin-Based Covalent Organic Frameworks for Photodynamic and Photothermal Therapy of Wound Infection

Wound infections have gradually become a major threat to human health. Recently, covalent organic frameworks (COFs) have shown great potential in antibacterial and wound healing; however, difficult biodegradability and long-time in vivo retention limit their further application. Herein, biodegradable COFs containing porphyrin backbones and hypoxia-sensitive azobenzene group, namely, HRCOFs, are fabricated for photodynamic therapy (PDT) and photothermal therapy (PTT) of wound infection. Due to the introduction of a porphyrin molecule, HRCOFs can produce singlet oxygen (1O2) under 660 nm laser irradiation. The prepared HRCOFs can also generate thermal energy under 808 nm NIR laser irradiation. HRCOFs show excellent synergetic antibacterial ability against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in vitro. The in vivo experiments also demonstrate synergistic PDT and PTT effects of HRCOFs against wound infection. Importantly, HRCOFs are response to wound microenvironment, can be degraded for clearance, and avoid some adverse effects caused by long-time retention in vivo, exhibiting good biocompatibility. In general, the obtained biodegradable HRCOFs with both photodynamic and photothermal effects can be used for antibacterial infections and provide great value for promoting wound healing.

Nano-scaffold-based delivery systems of antimicrobial agents in the treatment of osteomyelitis ; a narrative review

Osteomyelitis caused by drug-resistant pathogens is one of the most important medical challenges due to high rates of mortality and morbidity, and limited therapeutical options. The application of novel nano-scaffolds loaded with antibiotics has widely been studied and extensively evaluated for in vitro and in vivo inhibition of pathogens, regenerating damaged bone tissue, and increasing bone cell proliferation. The treatment of bone infections using the local osteogenic scaffolds loaded with antimicrobial agents may efficiently overcome the problems of the systemic use of antimicrobial agents and provide a controlled release and sufficient local levels of antibiotics in the infected sites. The present study reviewed various nano-scaffolds delivery systems of antimicrobial drugs evaluated to treat osteomyelitis. Nano-scaffolds offer promising approaches because they simulate natural tissue regeneration in terms of their mechanical, structural, and sometimes chemical properties. The potential of several nano-scaffolds prepared by natural polymers such as silk, collagen, gelatin, fibrinogen, chitosan, cellulose, hyaluronic, alginate, and synthetic compounds such as polylactic acid, polyglycolic acid, poly (lactic acid-co-glycolic acid), poly-ɛ-caprolactone have been studied for usage as drug delivery systems of antimicrobial agents to treat osteomyelitis. In addition to incorporated antimicrobial agents and the content of scaffolds, the physical and chemical characteristics of the prepared delivery systems are a determining factor in their effectiveness in treating osteomyelitis.

Development of a dextrin-vitamin D3 micelle nanocarrier for the antimicrobial peptide LLKKK18 as a potential therapeutic agent for bone infections

In this work, an expedite synthesis was developed for a self-assembled micelle carrier for the antimicrobial peptide LL18. Covalent one-pot functionalization of dextrin with succinylated vitamin D3 and succinic anhydride produced an amphiphilic material that undergoes self-assembly into micelles in aqueous medium. Succinylated dextrin-vitamin D3 micelles were efficiently loaded with LL18 by electrostatic and hydrophobic interactions. Remarkably, the LL18-loaded micelle formulation dramatically improves the antibacterial activity of free LL18 against S. aureus, completely abrogates its severe hemolytic activity, redirects the internalization of LL18 from the perinuclear region of osteoblasts to the lysosomes and reduces cellular toxicity towards osteoblasts and macrophages. Overall, this work demonstrates that self-assembled micelle formulations based on dextrin, vitamin D3 and antimicrobial peptides, are promising platforms to develop multifunctional antibiotic-independent antimicrobial agents, not prone to the development of bacterial resistance, to treat bone infections.

Local Delivery of Exosomes and Antibiotics in Hydroxyapatite-Based Nanocement for Osteomyelitis Management

The management of bone and joint infections is a formidable challenge in orthopedics and poses a global health concern. While clinical management emphasizes infection prevention and complete eradication, an effective strategy for stabilizing skeletal tissue with adequate soft tissue coverage remains limited. In this study, we have employed a novel approach of using the local delivery of exosomes and antibiotics (rifampicin) using a hydroxyapatite-based nanocement carrier to manage the residual space created during debridement effectively. Additionally, we synthesized a periosteum-guiding antioxidant herbal membrane to leverage the inherent periosteum regeneration capability of the bone, facilitating bone callus repair and natural healing. The synthesized scaffolds were biocompatible and demonstrated potent antibacterial activity in vitro. When evaluated in vivo in the Staphylococcus aureus-induced rat tibial osteomyelitis model, the released drugs successfully cleared the residual bacteria and the released exosome promoted bone healing, resulting in 3-fold increase in bone volume as analyzed via micro-CT analysis. Immunofluorescence staining of periosteum-specific markers also indicated the complete formation of periosteal layers, thus highlighting the complete bone repair.

Drug-Free "Triboelectric Immunotherapy" Activating Immunity for Osteomyelitis Treatment and Recurrence Prevention

Treatment of osteomyelitis is clinically challenging with low therapeutic efficacy and high risk of recurrence owing to the immunosuppressive microenvironment. Existing therapies are limited by drug concentration and single regulatory effect on the immune network, and emphasize the role of anti-inflammatory effects in reducing osteoclast rather than the role of proinflammatory effects in accelerating infection clearance, which is not conducive to complete bacteria elimination and recurrence prevention. Herein, a direct-current triboelectric nanogenerator (DC-TENG) is established to perform antibacterial effects and modulate immunological properties of infectious microenvironments of osteomyelitis through electrical stimulation, namely triboelectric immunotherapy. Seeing from the results, the triboelectric immunotherapy successfully activates polarization to proinflammatory (M1) macrophages in vitro, accompanied by satisfying direct antibacterial effects. The antibacterial and osteogenic abilities of triboelectric immunotherapy are verified in rat cranial osteomyelitis models. The effects on the polarization and differentiation of immune-related cells in vivo are investigated by establishing in situ tibial osteomyelitis models and immunosurveillance models in C57 mice respectively, indicating the ability of activating immunity and producing immunological memory for in situ infection and secondary recurrence, thus accelerating healing and preventing relapse. This study provides an efficient, long-acting, multifunctional, and wearable triboelectric immunotherapy strategy for drug-free osteomyelitis treatment systems.

Interface/Dipole Polarized Antibiotics-Loaded Fe3O4/PB Nanoparticles for Non-Invasive Therapy of Osteomyelitis Under Medical Microwave Irradiation

Due to their poor light penetration, photothermal therapy and photodynamic therapy are ineffective in treating deep tissue infections, such as osteomyelitis caused by Staphylococcus aureus (S. aureus). Here, a microwave (MW)-responsive magnetic targeting composite system consisting of ferric oxide (Fe3O4)/Prussian blue (PB) nanoparticles, gentamicin (Gent), and biodegradable poly(lactic-co-glycolic acid) (PLGA) is reported. The PLGA/Fe3O4/PB/Gent complex is used in combination with MW thermal therapy (MTT), MW dynamic therapy (MDT), and chemotherapy (CT) to treat acute osteomyelitis infected with S. aureus-infected. The powerful antibacterial effect of the PLGA/Fe3O4/PB/Gent is determined by the synergistic effects of heat and reactive oxygen species (ROS) generation by the Fe3O4/PB nanoparticles under MW irradiation and the effective release of Gent at the infection site via magnetic targeting. The antibacterial mechanism of the PLGA/Fe3O4/PB/Gent under MW irradiation is analyzed using bacterial transcriptome RNA sequencing. The MW heat and ROS reduce the activity of the protein transporters on the bacterial membrane, along with the transport of various ions and the acceleration of phosphate metabolism, which can lead to increased permeability of the bacterial membrane, damage the ribosome and DNA, and accompany the internal protein efflux of the bacteria, thus effectively killing the bacteria.

Heat-killed Lancefieldella Rimae Induces Bone Resorption by Promoting Osteoclast Differentiation

INTRODUCTION

Apical periodontitis, mainly caused by bacterial infection in the dental pulp, is often accompanied by abscess, periapical inflammation, and alveolar bone loss. Lancefieldella rimae has been detected in the root canals of patients with apical periodontitis. Here, we investigated whether L. rimae is associated with bone resorption.

METHODS

L. rimae was anaerobically cultured and heat-killed (HKLr). A mouse calvarial implantation model was used to determine the bone resorption in vivo. Committed osteoclasts prepared from C57BL/6 wild-type or Toll-like receptor 2 (TLR2)-deficient mice were differentiated into mature osteoclasts in the presence or absence of HKLr. The mRNA expression of tartrate-resistant acid phosphatase (TRAP), ATPase H+ transporting V0 subunit D2, cathepsin K, interleukin-6, tumor necrosis factor-α, and glyceraldehyde 3-phosphate dehydrogenase was quantified using real-time reverse transcription-polymerase chain reaction. The protein levels of c-Fos and NFATc1 were determined by Western blot analysis.

RESULTS

Implantation of HKLr onto the mouse calvaria induced the bone destruction with an increase of TRAP-positive areas. While HKLr enhanced the differentiation of osteoclasts, this effect was not observed in TLR2-deficient osteoclasts. HKLr dose-dependently increased the mRNA expression of genes associated with osteoclast differentiation including TRAP, ATPase H+ transporting V0 subunit D2, and cathepsin K. In addition, HKLr enhanced the expression of c-Fos and NFATc1, which are important transcription factors for osteoclast differentiation. Moreover, HKLr increased the expression of interleukin-6 and tumor necrosis factor-α.

CONCLUSION

L. rimae induces bone resorption by enhancing osteoclast differentiation through the TLR2 signaling pathway, implying that L. rimae is a causative agent responsible for the alveolar bone resorption accompanying apical periodontitis.

A multifunctional self-reinforced injectable hydrogel for enhancing repair of infected bone defects by simultaneously targeting macrophages, bacteria, and bone marrow stromal cells

Injectable hydrogels (IHs) have demonstrated huge potential in promoting repair of infected bone defects (IBDs), but how to endow them with desired anti-bacterial, immunoregulatory, and osteo-inductive properties as well as avoid mechanical failure during their manipulation are challenging. In this regard, we developed a multifunctional AOHA-RA/Lap nanocomposite IH for IBDs repair, which was constructed mainly through two kinds of reversible cross-links: (i) the laponite (Lap) crystals mediated electrostatic interactions; (ii) the phenylboronic acid easter bonds between the 4-aminobenzeneboronic acid grafted oxidized hyaluronic acid (AOHA) and rosmarinic acid (RA). Due to the specific structural composition, the AOHA-RA/Lap IH demonstrated superior injectability, self-recoverability, spatial adaptation, and self-reinforced mechanical properties after being injected to the bone defect site. In addition, the RA molecules could be locally released from the hydrogel following a Weibull model for over 10 days. Systematic in vitro/vivo assays proved the strong anti-bacterial activity of the hydrogel against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Moreover, its capability of inducing M2 polarization of macrophages (Mφ) and osteogenic differentiation of bone marrow stromal cells (BMSCs) was verified either, and the mechanism of the former was identified to be related to the JAK1-STAT1 and PI3K-AKT signaling pathways and that of the latter was identified to be related to the calcium signaling pathway, extracellular matrix (ECM) receptor interaction and TGF-β signaling pathway. After being implanted to a S. aureus infected rat skull defect model, the AOHA-RA/Lap IH significantly accelerated repair of IBDs without causing significant systemic toxicity. STATEMENT OF SIGNIFICANCE: Rosmarinic acid and laponite were utilized to develop an injectable hydrogel, promising for accelerating repair of infected bone defects in clinic. The gelation of the hydrogel was completely driven by two kinds of reversible cross-links, which endow the hydrogel superior spatial adaption, self-recoverability, and structural stability. The as-prepared hydrogel demonstrated superior anti-bacterial/anti-biofilm activity and could induce M2 polarization of macrophages and osteogenic differentiation of BMSCs. The mechanism behind macrophages polarization was identified to be related to the JAK1-STAT1 and PI3K-AKT signaling pathways. The mechanism behind osteogenic differentiation of BMSCs was identified to be related to the ECM receptor interaction and calcium signaling/TGF-β signaling pathways.

A natural killer cell mimic against intracellular pathogen infections

In the competition between the pathogen infection and the host defense, infectious microorganisms may enter the host cells by evading host defense mechanisms and use the intracellular biomolecules as replication nutrient. Among them, intracellular Staphylococcus aureus relies on the host cells to protect itself from the attacks by antibiotics or immune system to achieve long-term colonization in the host, and the consequent clinical therapeutic failures and relapses after antibiotic treatment. Here, we demonstrate that intracellular S. aureus surviving well even in the presence of vancomycin can be effectively eliminated using an emerging cell-mimicking therapeutic strategy. These cell mimics with natural killer cell-like activity (NKMs) are composed of a redox-responsive degradable carrier, and perforin and granzyme B within the carrier. NKMs perform far more effectivly than clinical antibiotics in treating intracellular bacterial infections, providing a direct evidence of the NK cell-mimicking immune mechanism in the treatment of intracellular S. aureus.

Understanding bacterial diversity, infection dynamics, prevention of antibiotic resistance: an integrated study in an Algerian hospital context

PURPOSE

Bacterial infections, particularly bacteremia, urinary tract infections (UTIs), and pus infections, remain among hospitals' most worrying medical problems. This study aimed to explore bacterial diversity, infection dynamics, and antibiotic resistance profiles of bacterial isolates.

METHODS

We analyzed data from 1750 outpatients and 920 inpatients, of whom 1.6% and 8.47% respectively had various bacterial infections.

RESULTS

The analysis revealed that UTIs were the most prevalent at 41.01%, particularly affecting women. UTIs also showed a distinct distribution across admission departments, notably in emergency (23.07%) and pediatric (14.10%) units. The most frequently isolated microorganisms were Escherichia coli (E. coli), followed by Klebsiella ornithinolytica. Skin infections followed UTIs, accounting for 35.88% of cases, more prevalent in men, with Staphylococcus aureus (S. aureus) being the primary pathogen (57%). Gram-negative bacteria (GNB) like E. coli and Pseudomonas aeruginosa contributed significantly to skin infections (43%). Bacteremia cases constituted 11.52% of bacterial infections, predominantly affecting women (67%) and linked to GNB (78%). A comparative study of antibiotic susceptibility profiles revealed more pronounced resistance in GNB strains isolated from inpatients, particularly to antibiotics such as Amoxicillin/clavulanic acid, Tetracyclin, Gentamicin, Chloramphenicol, and Ampicillin. In contrast, strains from ambulatory patients showed greater resistance to Colistin. Gram-positive bacteria from hospitalized patients showed higher resistance to quinolones and cephalosporins, while ambulatory strains showed high resistance to aminoglycosides, macrolides, fluoroquinolones, and penicillin. Furthermore, these analyses identified the most effective antibiotics for the empirical treatment of both community-acquired and nosocomial infections. Ciprofloxacin, aztreonam, and amikacin exhibited low resistance rates among GNB, with gentamicin and chloramphenicol being particularly effective for community-acquired strains. For S. aureus, ciprofloxacin, rifampicin, and cefoxitin were especially effective, with vancomycin showing high efficacy against community-acquired isolates and fosfomycin and chloramphenicol being effective for hospital-acquired strains.

CONCLUSION

These results are essential for guiding antibiotic therapy and improving clinical outcomes, thus contributing to precision medicine and antimicrobial stewardship efforts.

Deficiency of hasB accelerated the clearance of Streptococcus equi subsp. Zooepidemicus through gasdermin d-dependent neutrophil extracellular traps

Streptococcus equi subsp. zooepidemicus (S. zooepidemicus, SEZ) is an essential zoonotic bacterial pathogen that can cause various inflammation, such as meningitis, endocarditis, and pneumonia. UDP-glucose dehydrogenase (hasB) is indispensable in synthesizing SEZ virulence factor hyaluronan capsules. Our study investigated the infection of hasB on mice response to SEZ by employing a constructed capsule-deficient mutant strain designated as the ΔhasB strain. This deficiency was associated with a reduced SEZ bacterial load in the mice's blood and peritoneal lavage fluid (PLF) post-infection. Besides, the ΔhasB SEZ strain exhibited a higher propensity for neutrophil infiltration and release of cell-free DNA (cfDNA) in vivo compared to the wild-type (WT) SEZ strain. In vitro experiments further revealed that ΔhasB SEZ more effectively induced the formation of neutrophil extracellular traps (NETs) containing histone 3 (H3), neutrophil elastase (NE), and DNA, than its WT counterpart. Moreover, the release of NETs was determined to be gasdermin D (GSDMD)-dependent during the infection process. Taken together, these findings underscore that the deficiency of the hasB gene in SEZ leads to enhanced GSDMD-dependent NET release from neutrophils, thereby reducing SEZ's capacity to resist NETs-mediated eradication during infection. Our finding paves the way for the development of innovative therapeutic strategies against SEZ.

An Andrias davidianus derived composite hydrogel with enhanced antibacterial and bone repair properties for osteomyelitis treatment

Effective antibacterial therapy while accelerating the repair of bone defects is crucial for the treatment of osteomyelitis. Inspired by the protective mechanism of Andrias davidianus, we constructed an antibacterial hydrogel scaffold with excellent rigidity and long-term slow-release activity. While retaining the toughness of the skin secretion of Andrias davidianus (SSAD), the rigidity of the hydrogel material is increased by incorporating hydroxyapatite to meet the demands of bone-defect-filling materials. It also exerted antibacterial effects via the slow-release of vancomycin from local osteomyelitis lesions. Notably, the hydrogel can also carry a high stable recombinant miR-214-3p inhibitor (MSA-anti214). By the delivery of nano vector polyvinylamine, the long-term slow-release of MSA-anti214 is achieved to promote bone repair, making this composite hydrogel a potential SSAD-based osteomyelitis alleviator (SOA). In vitro and vivo results verified that the SOA effectively eliminated Staphylococcus aureus and repaired bone defects, ultimately mitigating the progression of osteomyelitis. This composite hydrogel extends the economic application prospects of A. davidianus and has provided new insights for the treatment of osteomyelitis. The study also explored new insights for the bone filling materials of bone defection and other skeletal system diseases.