Etiology of Implant Orthopedic Infections: A Survey on 1027 Clinical Isolates

Microbiology, Treatment, and Postoperative Outcomes of Gram-Negative Prosthetic Joint Infections-A Systematic Review of the Literature

INTRODUCTION

Gram-negative prosthetic joint infections (PJIs) represent 10% to 25% of all PJIs and are associated with worse outcomes than gram-positive infections. We sought to assess the microbiology, surgical treatment, and outcomes of patients with gram-negative PJIs.

METHODS

A systematic review using the PubMed and Embase databases was conducted. Our study was conducted following the PRISMA guidelines. Included studies were assessed for quality using the STROBE checklist. The primary outcome of analysis was treatment failure.

RESULTS

A total of 593 patients with gram-negative PJIs were included. Two-year survival free of treatment failure for hip and knee PJIs was 66% and 68% for acute infections, 39% and 78% for acute hematogenous infections, and 75% and 63% for chronic infections, respectively. Two-year survival free of treatment failure for acute infections treated with débridement, antibiotics, and implant retention was 65% and 67% for hip and knee PJIs, respectively. Exchange of the polyethylene during débridement, antibiotics, and implant retention was associated with higher treatment success ( P = 0.045). Chronic PJIs treated with two-stage revision had a two-year treatment success rate of 87% and 65% for the hip and knee, respectively. Risk factors of treatment failure were chronic obstructive pulmonary disease and C-reactive protein ≥30 mg/L in acute PJIs and female sex, knee infection, and previously revised implant in chronic PJIs. Acute PJIs caused by Pseudomonas spp. were associated with lower treatment failure rates.

CONCLUSION

Gram-negative PJIs are associated with a high treatment failure rate. Patient comorbidities, preoperative biochemical tests, microorganism etiology, and PJI characteristics affected the treatment success rate.

Functionalization of collagen fiber with nano-islands of silver via atomic layer deposition to promote bone healing

Modern techniques of thin film deposition (e.g., atomic layer deposition [ALD]) have paved the way for the modification of the surface of target substrates with thin films, nanoparticles, or other types of nanomaterials. This novel way can improve the base material's properties and enhance specific properties through adding functionalized groups to the surface. In this study, ALD of silver was conducted on commercially available Type I collagen membrane to improve its bioactivity and promote bone healing. Two different sample groups were studied: pristine collagen and silver-coated collagen via ALD (Ag/Collagen). Chemical and morphological changes of the collagen membrane were investigated with X-ray photoelectron spectroscopy and scanning electron microscopy and the bioactivity of functionalized collagen with silver was studied in vitro and in vivo. Nano-islands of silver were obtained on collagen fibrils with an average diameter of ∼16 nm. Comparison of gingival cells cultured on pristine collagen, and silver-coated collagen, demonstrated that the attained silver nanoparticle size and concentration are below the toxicity level of silver. In vivo assessment in rat model showed the biocompatibility of the Ag/Collagen, and greater new bone formation compared to control. This novel solvent-free method can be used to functionalize sensitive materials used in surgeries as bone grafting agents to enhance osteopromotive properties without any adverse effects to the cellular environment.

Optimizing biofilm inhibitors: Balancing activity and toxicity in 2N-aminated 5-aryl-2-aminoimidazoles

To evaluate the effect of amination on biofilm inhibition against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus, representative compounds of two previously described 5-aryl-2-aminoimidazole (5-Ar-2-AI) classes were aminated by installing an amino group at the end of the substituted n-alkyl chain. Amination led to an improvement in activity for one of the two classes, the 2N-substituted 5-Ar-2-AI class. Based on these findings, a more extensive library of 2N-substituted-aminated 5-Ar-2-AIs was synthesized having different n-alkyl and halogen substitutions on the 2N-position and the 4(5)-phenyl ring, respectively. Compounds were evaluated for their biofilm inhibitory activity against E. coli, P. aeruginosa, S. aureus, Staphylococcus epidermidis and MRSA. Additionally, their toxicity was tested on eight continuous cell lines, peripheral blood mononuclear cells and Caenorhabditis elegans, along with their genotoxicity on Capan-1. Halogenation and elongation of the n-alkyl substituent showed a positive effect on biofilm inhibitory activity, but also increased toxicity. Compromising between activity and toxicity, a non-halogenated 2N-substituted-aminated 5-Ar-2-AI compound with an intermediate n-heptyl substitution demonstrated promising broad-spectrum biofilm inhibition, making it a suitable candidate for further research in anti-infectious medical applications.

Piezoelectric Biomaterial with Advanced Design for Tissue Infection Repair

Bacterial infection has become the most dangerous factor in tissue repair, which strongly affects the tissue regeneration efficiency and wellness of patients. Piezoelectric materials exhibit the outstanding advantage of producing electrons without external power supply. The ability of electron enrichment and reactive oxygen species generation through noninvasive stimulations enables piezoelectric materials the potential applications of antibacterial. Many studies have proved the feasibility of piezoelectric materials as a functional addition in antibacterial biomaterial. In fact, numerous piezoelectric materials with ingenious designs are reported to be effective in antibacterial processes. This review summarizes the antibacterial mechanisms of piezoelectric, illuminating their potential in combating bacteria. Recent advancement in the design and construction of piezoelectric biomaterial including defect engineering, heterojunction, synergy with metal and the composite scaffold configuration are thoroughly reviewed. Moreover, the applications and therapeutic effects of piezoelectric materials in common tissues with antibacterial requirements are introduced, such as orthopedics, dental, and wound healing. Finally, the development prospects and points deserving further exploration are listed. This review is expected to provide valuable insight into the relationship between antibacterial processes and piezoelectric materials, further inspiring constructive development in this emerging scientific discipline.

Implant-Derived S. aureus Isolates Drive Strain-Specific Invasion Dynamics and Bioenergetic Alterations in Osteoblasts

Background: Implants are integral to modern orthopedic surgery. The outcomes are good, but infections remain a serious issue. Staphylococcus aureus (S. aureus), along with Staphylococcus epidermidis, are predominant pathogens responsible for implant-associated infections, as conventional antibiotic treatments often fail due to biofilm formation or the pathogens' ability to invade cells and to persist intracellularly. Objectives: This study therefore focused on interactions of S. aureus isolates from infected implants with MG63 and SaOS2 osteoblasts by investigating the adhesion, invasion, and the impact on the bioenergetics of osteoblasts. Methods and Results: We found that the ability of S. aureus to adhere to osteoblasts depends on the isolate and was not associated with a single gene or expression pattern of characteristic adhesion proteins, and further, was not correlated with invasion. However, analysis of invasion capabilities identified better invasion conditions for S. aureus isolates with the SaOS2 osteoblastic cells. Interestingly, metabolic activity of osteoblasts remained unaffected by S. aureus infection, indicating cell survival. In contrast, respiration assays revealed an altered mitochondrial bioenergetic turnover in infected cells. While basal as well as maximal respiration in MG63 osteoblasts were not influenced statistically by S. aureus infections, we found increased non-mitochondrial respiration and enhanced glycolytic activity in the osteoblasts, which was again, more pronounced in the SaOS2 osteoblastic cells. Conclusions: Our findings highlight the complexity of S. aureus-host interactions, where both the pathogen and the host cell contribute to intracellular persistence and survival, representing a major factor for therapeutic failures.

Progress in Designing Therapeutic Antimicrobial Hydrogels Targeting Implant-associated Infections: Paving the Way for a Sustainable Platform Applied to Biomedical Devices

Implantable biomedical devices have found widespread use in restoring lost functions or structures within the human body, but they face a significant challenge from microbial-related infections, which often lead to implant failure. In this context, antimicrobial hydrogels emerge as a promising strategy for treating implant-associated infections owing to their tunable physicochemical properties. However, the literature lacks a comprehensive analysis of antimicrobial hydrogels, encompassing their development, mechanisms, and effect on implant-associated infections, mainly in light of existing in vitro, in vivo, and clinical evidence. Thus, this review addresses the strategies employed by existing studies to tailor hydrogel properties to meet the specific needs of each application. Furthermore, this comprehensive review critically appraises the development of antimicrobial hydrogels, with a particular focus on solving infections related to metallic orthopedic or dental implants. Then, preclinical and clinical studies centering on providing quantitative microbiological results associated with the application of antimicrobial hydrogels are systematically summarized. Overall, antimicrobial hydrogels benefit from the tunable properties of polymers and hold promise as an effective strategy for the local treatment of implant-associated infections. However, future clinical investigations, grounded on robust evidence from in vitro and preclinical studies, are required to explore and validate new antimicrobial hydrogels for clinical use.

Injectable vancomycin-loaded silk fibroin/methylcellulose containing calcium phosphate-based in situ thermosensitive hydrogel for local treatment of osteomyelitis: Fabrication, characterization, and in vitro performance evaluation

The conventional treatment of osteomyelitis with antibiotic-loaded nondegradable polymethylmethacrylate (ATB-PMMA) beads has certain limitations, including impeded bone reconstruction and the need for secondary surgery. To overcome this challenge, this study aimed to develop and characterize an injectable vancomycin-loaded silk fibroin/methylcellulose containing calcium phosphate-based in situ thermosensitive hydrogel (VC-SF/MC-CAPs). The VC-SF/MC-CAPs solution can be easily administered at room temperature with a low injectability force of ≤30 N and a high vancomycin (VC) content of ~96%. Additionally, at physiological temperature (37 °C), the solution could transform into a rigid hydrogel within 7 minutes. In vitro drug release performed under both physiological (pH 7.4) and infection conditions (pH 4.5) revealed a prolonged release pattern of VC-SF/MC-CAPs following the Peppas-Sahlin kinetic model. In addition, the released VC from VC-SF/MC-CAPs hydrogels exhibited antibacterial activity against Staphylococcus aureus for a period exceeding 35 days, as characterized by the disk diffusion assay. Furthermore, at pH 7.4, the VC-SF/MC-CAPs demonstrated >60% degradation within 35 days. Importantly, when exposed to physiological pH conditions, CAPs are transformed into bioactive hydroxyapatite, which benefits bone formation. Therefore, VC-SF/MC-CAPs showed significant potential as a local drug delivery system for treating osteomyelitis.

Next generation sequencing identifies an increased diversity of microbes in post lavage specimens in infected TKA using a biofilm disrupting irrigant

BACKGROUND

Periprosthetic joint infection (PJI) is a devastating complication of joint arthroplasty. In chronic PJI, a biofilm envelops the surface of implants, which contains microbiota within an extra-microbial polymeric matrix (EMPM). Microbial identification is paramount for effective treatment. In this study, we use a multi-modal, EMPM disrupting, neoadjuvant irrigant and compare the microbiota detected pre-lavage to post-lavage by two techniques: culture and Next Generation Sequencing (NGS). We suspect more organisms to be identified after applying an EMPM disrupting irrigant.

METHODS

A multicenter, prospective study was conducted on 38 patients with known Total Knee Arthroplasty PJI. At initial arthrotomy, synovial fluid was obtained and analyzed for quantitative cultures and microbial NGS. Joint was then irrigated with Bactisure Lavage followed by Normal Saline. Post-lavage samples were similarly obtained and analyzed.

RESULTS

In pre-lavage samples for cultures, 55.3% of samples were positive, identifying 11 unique organisms. In post-lavage samples for cultures, 13.2% of samples were positive, identifying 5 unique organisms. In pre-lavage samples for NGS, 79% were DNA signal positive, identifying 126 unique organisms. In post-lavage samples for NGS, 74% of samples were DNA signal positive, identifying 177 unique organisms. Moreover, 135/177 of these organisms were not identified pre-lavage.

CONCLUSION

In this pre-to-post irrigant study, culture showed a decrease in the number of identifiable organisms post-lavage. In contrast NGS revealed an increase in the number of identifiable organisms post-lavage. Furthermore, NGS identified 135 additional organisms, not detected pre-lavage. This suggests an increased diversity of microbes may exist within EMPM, which are not cultivable.

The impact of adjuvant antibiotic hydrogel application on the primary stability of uncemented hip stems

Objectives

To assess the effect of adjuvant antibiotic-loaded hydrogel application on the primary stability of implanted uncemented hip stems.

Design

Biomechanical study.

Setting

An electro-mechanic material test system (#5866, Instron, Norwood, MA, USA) equipped with a 10-kN load cell was used. A staircase loading protocol was applied via quasi-static ramped compression loading at 0.005 mm/s and six different load levels between 500 N and 3000 N in 500 N intermittent load increase steps.

Participants

12 artificial femora were prepared and received a collarless uncemented standard offset stem (Corail; DePuy Synthes, Zuchwil, Switzerland).

Interventions

The two groups were prepared with or without the antibiotic-loaded hydrogel.

Main outcome measures

Construct stiffness was determined from the recorded load-displacement curves and stem subsidence was measured via motion tracking.

Results

Construct stiffness (control: 4176±240 N/mm; intervention: 4588±448 N/mm) was not significantly different between the groups (p=0.076). Stem subsidence increased significantly over the increasing load levels in each separate group (p≤0.002) and remained not significantly different between the groups (p=0.609).

Conclusions

The application of antibiotic-loaded hydrogel was associated with non-inferior performance in terms of primary uncemented hip stem stability. This finding makes the prospect of adjuvant antibiotic-loaded hydrogel application potentially feasible; however, it requires further investigations prior to translation in the clinical practice.

Prosthetic Joint Infection Research Models in NZW Rabbits: Opportunities for Standardization-A Systematic Review

Prosthetic joint infection (PJI) is a major complication following total arthroplasty. Rising antimicrobial resistance (AMR) to antibiotics will further increase therapeutic insufficiency. New antibacterial technologies are being developed to prevent PJI. In vivo models are still needed to bridge the translational gap to clinical implementation. Though rabbit models have been used most frequently, there is no consensus about methodology and measured outcomes. The PubMed, Scopus, and EMBASE databases were searched for literature on PJI in rabbit models. Data extraction included bias control, experimental design, and outcome measures of the NZW rabbit models in the articles. A total of 60 articles were included in this systematic literature review. The articles were divided into six groups based on the PJI intervention: no intervention used (21%), revision surgery (14%), prevention with only antibiotics (21%), prevention with surface modifications (7%), prevention with coatings (23%), and others (14%). Despite the current availability of guidelines and recommendations regarding experimental design, bias control, and outcome measures, many articles neglect to report on these matters. Ultimately, this analysis aims to assist researchers in determining suitable clinically relevant methodologies and outcome measures for in vivo PJI models using NZW rabbits to test new antimicrobial technologies.

The Opportunistic Pathogen Staphylococcus warneri: Virulence and Antibiotic Resistance, Clinical Features, Association with Orthopedic Implants and Other Medical Devices, and a Glance at Industrial Applications

In recent decades, the risk of developing opportunistic infections has increased in parallel with the ever-increasing number of people suffering from chronic immunosuppressive diseases or undergoing prosthetic surgery. Staphylococcus warneri is a Gram-positive and coagulase-negative bacterium. Usually found as a component of the healthy human and animal microbiota of the skin and mucosae, it can take on the role of an opportunistic pathogen capable of causing a variety of infections, ranging from mild to life-threatening, not only in immunocompromised patients but even, although rarely, in healthy people. Here, in addition to a concise discussion of the identification and distinguishing features of S. warneri compared to other staphylococcal species, a systematic overview of the findings from case reports and clinical studies is provided. The paper highlights the virulence and antibiotic resistance profiles of S. warneri, the different clinical contexts in which it has proven to be a serious pathogen, emphasizing its ability to colonize artificial prosthetic materials and its tropism for musculoskeletal and cardiovascular tissues. Some original data on orthopedic implant infections by S. warneri complement the discussion. Finally, from a different perspective, the paper addresses the possibilities of industrial exploitation of this bacterium.

In Vitro Evaluation of Electrospun PCL Bioscaffold with Zinc-Doped Bioactive Glass Powder Addition

Preparing electrospun fibers by applying a potential difference between a polymeric solution and a contacting substrate is increasingly attracting attention in tissue engineering applications. Among the numerous polymers, polycaprolactone (PCL) bioscaffold has been widely investigated due to its biocompatibility and biodegradability. Bioactive powder can be added to further improve its performance. In the present study, bioactive glass powder modified by adding 0-6 wt.% antibacterial zinc element (coded as ZBG) was prepared through the sol-gel process. Furthermore, PCL bioscaffolds with various ZBG additions were prepared using the electrospinning technique. The zinc-doped bioactive glass powder and electrospun PCL/ZBG bioscaffolds were evaluated using scanning electron microscopy, X-ray diffraction and Fourier-transform infrared spectroscopy to determine their structural properties. Additionally, in vitro bioactivity, biocompatibility and antibacterial performance were investigated. Experimental results showed that sol-gelled ZBG powder possessed superior bioactivity and 0.8 g ZBG was the optimal addition to prepare PCL/ZBG bioscaffolds with. All the electrospun PCL/ZBG bioscaffolds were biocompatible and their antibacterial performance against two S. aureus strains (SA133 and Newman) improved with increasing zinc concentration. Electrospun PCL/ZBG bioscaffolds exhibited excellent bioactivity and have great potential for biomedical application.

Biocompatibility analysis of titanium bone wedges coated by antibacterial ceramic-polymer layer

This paper presents the surface treatment results of titanium, veterinary bone wedges. The functional coating is composed of a porous oxide layer (formed by a plasma electrolytic oxidation process) and a polymer poly(sebacic anhydride) (PSBA) layer loaded with amoxicillin (formed by dip coatings). The coatings were porous and composed of Ca (4.16%-6.54%) and P (7.64%-9.89% determined by scanning electron microscopy with EDX) in the upper part of the implant. The titanium bone wedges were hydrophilic (54° water contact angle) and rough (surface area (Sa):1.16 μm) The surface tension determined using diiodomethane was 68.6 ± 2.0° for the anodized implant and was similar for hybrid coatings: 60.7 ± 2.2°. 12.87 ± 0.91 µg/mL of amoxicillin was released from the implants during the first 30 min after immersion in the phosphate-buffered saline (PBS) solution. This concentration was enough to inhibit the Staphylococcus aureus ATCC 25923, and Staphylococcus epidermidis ATCC12228 growth. The obtained inhibition zones were between 27.3 ± 2.1 mm-30.7 ± 0.6 mm when implant extract after 1 h or 4 h immersion in PBS was collected. Various implant biocompatibility analyses were performed under in vivo conditions, including pyrogen test (3 rabbits), intracutaneous reactivity (3 rabbits, 5 places by side), acute systemic toxicity (20 house mice), and local lymph node assay (LLNA) (20 house mice). The extracts from implants were collected in polar and non-polar solutions, and the tests were conducted according to ISO 10993 standards. The results from the in vivo tests showed, that the implant's extracts are not toxic (mass body change below 5%), not sensitizing (SI < 1.6), and do not show the pyrogen effect (changes in the temperature 0.15ºC). The biocompatibility tests were performed in a certificated laboratory with a good laboratory practice certificate after all the necessary permissions.

Alkyl Pyridinol Compounds Exhibit Antimicrobial Effects against Gram-Positive Bacteria

Background/Objectives. The rise of antibiotic-resistant pathogens represents a significant global challenge in infectious disease control, which is amplified by the decline in the discovery of novel antibiotics. Staphylococcus aureus continues to be a highly significant pathogen, causing infections in multiple organs and tissues in both healthcare institutions and community settings. The bacterium has become increasingly resistant to all available antibiotics. Consequently, there is an urgent need for novel small molecules that inhibit the growth or impair the survival of bacterial pathogens. Given their large structural and chemical diversity, as well as often unique mechanisms of action, natural products represent an excellent avenue for the discovery and development of novel antimicrobial treatments. Anaephene A and B are two such naturally occurring compounds with significant antimicrobial activity against Gram-positive bacteria. Here, we report the rapid syntheses and biological characterization of five novel anaephene derivatives, which display low cytotoxicity against mammalian cells but potent antibacterial activity against various S. aureus strains, including methicillin-resistant S. aureus (MRSA) and the multi-drug-resistant community-acquired strain USA300LAC. Methods. A Sonogashira cross-coupling reaction served as the key step for the synthesis of the alkyl pyridinol products. Results/Conclusions. Using the compound JC-01-074, which displays bactericidal activity already at low concentrations (MIC: 16 μg/mL), we provide evidence that alkyl pyridinols target actively growing and biofilm-forming cells and show that these compounds cause disruption and deformation of the staphylococcal membrane, indicating a membrane-associated mechanism of action.

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

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

Longitudinal intravital imaging of the bone marrow for analysis of the race for the surface in a murine osteomyelitis model

Critical knowledge gaps of orthopedic infections pertain to bacterial colonization. The established dogma termed the Race for the Surface posits that contaminating bacteria compete with host cells for the implant post-op, which remains unproven without real-time in vivo evidence. Thus, we modified the murine longitudinal intravital imaging of the bone marrow (LIMB) system to allow real-time quantification of green fluorescent protein (GFP+) host cells and enhanced cyan fluorescent protein (ECFP+) or red fluorescent protein (RFP+) methicillin-resistant Staphylococcus aureus (MRSA) proximal to a transfemoral implant. Following inoculation with ~105 CFU, an L-shaped metal implant was press-fit through the lateral cortex at a 90° angle ~0.150 mm below a gradient refractive index (GRIN) lens. We empirically derived a volume of interest (VOI) = 0.0161 ± 0.000675 mm3 during each imaging session by aggregating the Z-stacks between the first (superior) and last (inferior) in-focus LIMB slice. LIMB postimplantation revealed very limited bacteria detection at 1 h, but by 3 h, 56.8% of the implant surface was covered by ECFP+ bacteria, and the rest were covered by GFP+ host cells. 3D volumetric rendering of the GFP+ and ECFP+ or RFP+ voxels demonstrated exponential MRSA growth between 3 and 6 h in the Z-plane, which was validated with cross-sectional ex vivo bacterial burden analyses demonstrating significant growth by ~2 × 104 CFU/h on the implant from 2 to 12 h post-op (p < 0.05; r2  > 0.98). Collectively, these results show the competition at the surface is completed by 3 h in this model and demonstrate the potential of LIMB to elucidate mechanisms of bacterial colonization, the host immune response, and the efficacy of antimicrobials.

2023 International Consensus Meeting on musculoskeletal infection: Summary from the treatment workgroup and consensus on treatment in preclinical models

In vitro and in vivo studies are critical for the preclinical efficacy assessment of novel therapies targeting musculoskeletal infections (MSKI). Many preclinical models have been developed and applied as a prelude to evaluating safety and efficacy in human clinical trials. In performing these studies, there is both a requirement for a robust assessment of efficacy, as well as a parallel responsibility to consider the burden on experimental animals used in such studies. Since MSKI is a broad term encompassing infections varying in pathogen, anatomical location, and implants used, there are also a wide range of animal models described modeling these disparate infections. Although some of these variations are required to adequately evaluate specific interventions, there would be enormous value in creating a unified and standardized criteria to animal testing in the treatment of MSKI. The Treatment Workgroup of the 2023 International Consensus Meeting on Musculoskeletal Infection was responsible for questions related to preclinical models for treatment of MSKI. The main objective was to review the literature related to priority questions and estimate consensus opinion after voting. This document presents that process and results for preclinical models related to (1) animal model considerations, (2) outcome measurements, and (3) imaging.

Emerging Issues and Initial Insights into Bacterial Biofilms: From Orthopedic Infection to Metabolomics

Bacterial biofilms, enigmatic communities of microorganisms enclosed in an extracellular matrix, still represent an open challenge in many clinical contexts, including orthopedics, where biofilm-associated bone and joint infections remain the main cause of implant failure. This study explores the scenario of biofilm infections, with a focus on those related to orthopedic implants, highlighting recently emerged substantial aspects of the pathogenesis and their potential repercussions on the clinic, as well as the progress and gaps that still exist in the diagnostics and management of these infections. The classic mechanisms through which biofilms form and the more recently proposed new ones are depicted. The ways in which bacteria hide, become impenetrable to antibiotics, and evade the immune defenses, creating reservoirs of bacteria difficult to detect and reach, are delineated, such as bacterial dormancy within biofilms, entry into host cells, and penetration into bone canaliculi. New findings on biofilm formation with host components are presented. The article also delves into the emerging and critical concept of immunometabolism, a key function of immune cells that biofilm interferes with. The growing potential of biofilm metabolomics in the diagnosis and therapy of biofilm infections is highlighted, referring to the latest research.

Etiology of Total Knee Arthroplasty Revisions: A Two-Decade Institutional Perspective

Total knee arthroplasty (TKA) implant survival time is determined by various patient and implant-related factors and varies significantly in recent worldwide reports. In our study, we have included 247 TKA revisions in 203 patients performed in our hospital over the last 20 years. Multiple etiologies of revisions were identified and classified into 10 categories. Time to failure was analyzed with regard to etiology, patient demographics, and other relevant data. The overall average time to revision was 44.08 months (95% confidence interval (CI) between 33.34 and 49.82 months). Age at primary implant was negatively correlated with time to revision (hazard ratio (HR) = 1.0521 and 95% CI of HR = 1.0359 to 1.0685) and female patients showed a 1.59 times higher risk of implant failure than males. Periprosthetic joint infection was the cause of 46.56% (n=115) of revisions (out of which 12.55% (n=31) were early infections, diagnosed within the first three months), while aseptic loosening was found in 31.98% (n=79) of cases. Infection correlated with a shorter time to revision compared to aseptic loosening (p<0.05). These findings emphasize the need to intensify efforts to deliver the best patient care, select the best antibiotic regimen, and improve surgical techniques to decrease the incidence of infectious complications.

Natural medicine delivery from 3D printed bone substitutes

Unmet medical needs in treating critical-size bone defects have led to the development of numerous innovative bone tissue engineering implants. Although additive manufacturing allows flexible patient-specific treatments by modifying topological properties with various materials, the development of ideal bone implants that aid new tissue regeneration and reduce post-implantation bone disorders has been limited. Natural biomolecules are gaining the attention of the health industry due to their excellent safety profiles, providing equivalent or superior performances when compared to more expensive growth factors and synthetic drugs. Supplementing additive manufacturing with natural biomolecules enables the design of novel multifunctional bone implants that provide controlled biochemical delivery for bone tissue engineering applications. Controlled release of naturally derived biomolecules from a three-dimensional (3D) printed implant may improve implant-host tissue integration, new bone formation, bone healing, and blood vessel growth. The present review introduces us to the current progress and limitations of 3D printed bone implants with drug delivery capabilities, followed by an in-depth discussion on cutting-edge technologies for incorporating natural medicinal compounds embedded within the 3D printed scaffolds or on implant surfaces, highlighting their applications in several pre- and post-implantation bone-related disorders.

Biofilms in Periprosthetic Orthopedic Infections Seen through the Eyes of Neutrophils: How Can We Help Neutrophils?

Despite advancements in our knowledge of neutrophil responses to planktonic bacteria during acute inflammation, much remains to be elucidated on how neutrophils deal with bacterial biofilms in implant infections. Further complexity transpires from the emerging findings on the role that biomaterials play in conditioning bacterial adhesion, the variety of biofilm matrices, and the insidious measures that biofilm bacteria devise against neutrophils. Thus, grasping the entirety of neutrophil-biofilm interactions occurring in periprosthetic tissues is a difficult goal. The bactericidal weapons of neutrophils consist of the following: ready-to-use antibacterial proteins and enzymes stored in granules; NADPH oxidase-derived reactive oxygen species (ROS); and net-like structures of DNA, histones, and granule proteins, which neutrophils extrude to extracellularly trap pathogens (the so-called NETs: an allusive acronym for "neutrophil extracellular traps"). Neutrophils are bactericidal (and therefore defensive) cells endowed with a rich offensive armamentarium through which, if frustrated in their attempts to engulf and phagocytose biofilms, they can trigger the destruction of periprosthetic bone. This study speculates on how neutrophils interact with biofilms in the dramatic scenario of implant infections, also considering the implications of this interaction in view of the design of new therapeutic strategies and functionalized biomaterials, to help neutrophils in their arduous task of managing biofilms.

Joint fluid concentrations of amphotericin B after local application with calcium sulphate-report of 2 cases

Fungal periprosthetic joint infections (PJI) are difficult to treat, due to important biofilm formation and limited local penetration of systemically administered antifungals. Calcium sulphate (CaSO4 ) might be a promising carrier to increase local concentration of antifungals. We hypothesized that local amphotericin B release from CaSO4 is high enough to significantly contribute to treatment of fungal PJI. We report joint fluid and serum concentrations of amphotericin B after local application with CaSO4 as an implanted resorbable carrier material as adjunct to standard surgical and systemic antifungal treatment in two cases of PJI with Candida spp. Maximal joint fluid amphotericin B concentration was 14.01 mg/L 5 days after the second local administration of liposomal amphotericin in Case One and 25.77 mg/L 14 days after the second local administration in Case Two. Concentrations higher than minimal inhibitory concentrations (MIC) could be measured for 21 days and 17 days after local administration in Case One and Two, respectively. In Case Two, serum concentration of amphotericin B was <0.01 mg/L 3 days after local administration of 450 mg liposomal amphotericin B. No local or systemic adverse reaction was observed. Fungal PJI was successfully eradicated in both cases with a follow-up of 12 months in Case One and 20 months in Case Two. Application of amphotericin B-loaded CaSO4 was associated with joint fluid concentrations higher than minimal inhibitory concentrations for Candida spp. for approximately 3 weeks, with the advantage that the carrier material dissolves spontaneously and does not require secondary removal. Relapse of fungal infections did not occur in these two patients.

A New In Vitro Blood Flow Model for the Realistic Evaluation of Antimicrobial Surfaces

Device-associated bloodstream infections can cause serious medical problems and cost-intensive postinfection management, defining a need for more effective antimicrobial coatings. Newly developed coatings often show reduced bacterial colonization and high hemocompatibility in established in vitro tests, but fail in animal studies or clinical trials. The poor predictive power of these models is attributed to inadequate representation of in vivo conditions. Herein, a new single-pass blood flow model, with simultaneous incubation of the test surface with bacteria and freshly-drawn human blood, is presented. The flow model is validated by comparative analysis of a recently developed set of antiadhesive and contact-killing polymer coatings, and the corresponding uncoated polycarbonate surfaces. The results confirm the model's ability to differentiate the antimicrobial activities of the studied surfaces. Blood activation data correlate with bacterial surface coverage: low bacterial adhesion is associated with low inflammation and hemostasis. Shear stress correlates inversely with bacterial colonization, especially on antiadhesive surfaces. The introduced model is concluded to enable the evaluation of novel antimicrobial materials under in vivo-like conditions, capturing interactions between bacteria and biomaterials surfaces in the presence of key components of the ex vivo host response.

Corynebacterium periprosthetic joint infection: a systematic review of 52 cases at 2.5 years follow-up

INTRODUCTION

While large progress has been achieved in identifying and treating the most common pathogens involved in periprosthetic joint infections (PJI), there remains limited knowledge on atypical pathogens such as Corynebacterium. For that reason, we analyzed infection and diagnostical characteristics, as well as treatment outcome in Corynebacterium PJI.

METHODS

A systematic review was performed based on a structured PubMed and Cochrane Library analysis using the PRISMA algorithm. The search was performed by 2 independent reviewers, and articles from 1960 to 2022 considered eligible for inclusion. Out of 370 search results, 12 studies were included for study synthesis.

RESULTS

In total, 52 cases of Corynebacterium PJI were identified (31 knees, 16 hips, 4 elbows, 1 shoulder). Mean age was 65 years, with 53% females, and a mean Charlson Comorbidity Index of 3.9. The most common species was Corynebacterium striatum in 37 cases (71%). Most patients were treated with two-stage exchange (40%), isolated irrigation and debridement (21%), and resection arthroplasty (19%). Mean duration of antibiotic treatment was 8.5 weeks. At a mean follow-up of 2.5 years, there were 18 reinfections (33%), and 39% were for Corynebacterium. Initial infection by Corynebacterium striatum species was predictive of reoperation (p = 0.035) and reinfection (p = 0.07).

CONCLUSION

Corynebacterium PJI affects multimorbid and elderly patients, with one in three developing a reinfection at short term. Importantly, the relative majority of reinfections was for persistent Corynebacterium PJI.

Trends in microbiological epidemiology of orthopedic infections: a large retrospective study from 2008 to 2021

BACKGROUND

This study assessed the distribution characteristics of pathogens isolated from cases of orthopedic infections and focused on the antimicrobial susceptibility of the main pathogens.

METHODS

This retrospective study involved patients with orthopedic infection in a tertiary medical center located in Shanghai, China, from 2008 to 2021.Pathogen information and the basic information of patients were identified from clinical microbiology laboratory data and the institutional medical record system.

RESULTS

In total, the pathogen information of 2821 patients were enrolled in the study. S. aureus (37.71%) was the main causative pathogen responsible for orthopedic infection. Gender, pathogens distribution and polymicrobial infection rates were significantly different (P < 0.05) among patients with different orthopedic infection diseases.The trends in the distribution of pathogens in the total cohort, implant-related infection group (Group A), non-implant-related infection group (Group B), and the sub-group of cases with arthroplasty showed significant linear changes over time. And the polymicrobial infection rates of the total cohort (from 17.17% to 11.00%), Group B(from 24.35% to 14.47%), and the sub-group of cases with internal fixation (from 10.58% to 4.87%) decreased significantly. The antimicrobial susceptibility showed changing trends with time for some main pathogens, especially for S.aureus and Enterobacter spp.

CONCLUSIONS

Our research indicated that the pathogen distribution and antimicrobial susceptibility in orthopedic infections changed over time. And the distribution of pathogens varied significantly among different types of orthopedic infectious diseases. These findings may serve as a reference for prophylaxis and empirical treatment strategies of orthopedic infection.

Clinical investigation of use of an antimicrobial peptide hydrogel wound dressing on intact skin

A material with the ability to rapidly eradicate bacteria via a contact-killing mechanism has the benefit of a more localised treatment that is easy to implement when needed to prevent or treat a bacterial infection. Here, we present an antimicrobial material based on covalently attached antimicrobial peptides (AMPs) to a soft amphiphilic hydrogel. This results in a material that exhibits an antimicrobial effect based on contact-killing. In this study, the antimicrobial efficacy of the AMP-hydrogel was investigated by observing the changes in total bioburden on the intact skin of healthy human volunteers when the AMP-hydrogel dressing was placed on the forearm for three hours. The AMP-hydrogel significantly reduced the bioburden on the skin from a mean value of 1200CFU/cm² for the untreated skin to 23CFU/cm². Biocompatibility evaluations of the AMP-hydrogel showed no sign of cytotoxicity, acute systemic toxicity, irritation or sensitisation, demonstrating the safety of the AMP-hydrogel as a potential wound dressing. Leachability studies confirmed no release of AMPs and that the antimicrobial effect was localised to the surface of the hydrogels, demonstrating a pure contact-killing mode of action.

Zinc (Zn) Doping by Hydrothermal and Alkaline Heat-Treatment Methods on Titania Nanotube Arrays for Enhanced Antibacterial Activity

Titanium (Ti) is a popular biomaterial for orthopedic implant applications due to its superior mechanical properties such as corrosion resistance and low modulus of elasticity. However, around 10% of these implants fail annually due to bacterial infection and poor osseointegration, resulting in severe pain and suffering for the patients. To improve their performance, nanoscale surface modification approaches and doping of trace elements on the surfaces can be utilized which may help in improving cell adhesion for better osseointegration while reducing bacterial infection. In this work, at first, titania (TiO₂) nanotube arrays (NT) were fabricated on commercially available pure Ti surfaces via anodization. Then zinc (Zn) doping was conducted following two distinct methods: hydrothermal and alkaline heat treatment. Scanning electron microscopic (SEM) images of the prepared surfaces revealed unique surface morphologies, while energy dispersive X-ray spectroscopy (EDS) revealed Zn distribution on the surfaces. Contact angle measurements indicated that NT surfaces were superhydrophilic. X-ray photoelectron spectroscopy (XPS) provided the relative amount of Zn on the surfaces and indicated that hydrothermally treated surfaces had more Zn compared to the alkaline heat-treated surfaces. X-ray crystallography (XRD) and nanoindentation techniques provided the crystal structure and mechanical properties of the surfaces. While testing with adipose-derived stem cells (ADSC), the surfaces showed no apparent cytotoxicity to the cells. Finally, bacteria adhesion and morphology were evaluated on the surfaces after 6 h and 24 h of incubation. From the results, it was confirmed that NT surfaces doped with Zn drastically reduced bacteria adhesion compared to the Ti control. Zn-doped NT surfaces thus offer a potential platform for orthopedic implant application.

Antibacterial Activity on Orthopedic Clinical Isolates and Cytotoxicity of the Antimicrobial Peptide Dadapin-1

In orthopedic surgery, biomaterial-associated infections represent a complication of serious concern. Most promising strategies to prevent these infections currently rely on the use of anti-infective biomaterials. Desirably, in anti-infective biomaterials, the antibacterial properties should be achieved by doping, grafting, or coating the material surfaces with molecules that are alternative to conventional antibiotics and exhibit a potent and highly specific activity against bacteria, without altering the biocompatibility. Antimicrobial peptides (AMPs) are among the most interesting candidate molecules for this biomaterial functionalization. Here, the potential expressed by the recently discovered peptide Dadapin-1 was explored by assaying its MIC, MBIC and MBC on clinical strains of relevant bacterial species isolated from orthopedic infections and by assessing its cytotoxicity on the human osteoblast-like MG63 cells. When appropriately tested in diluted Mueller Hinton Broth II (MHB II), Dadapin-1 exhibited significant antibacterial properties. MIC values were in the range of 3.1-6.2 µM for the gram-positive bacteria Staphylococcus aureus, Staphylococcus epidermidis, and Staphylococcus warneri, and 12.4-24.9 µM for the gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa. Interestingly, the peptide was found non-cytotoxic, with an IC50 exceeding the highest concentration tested of 179 µM. Overall, Dadapin-1 expresses considerable potential for future application in the production of anti-infective biomaterials.

Effect of the Biopolymer Carrier on Staphylococcus aureus Bacteriophage Lytic Activity

The use of implant materials is always associated with the risk of infection. Moreover, the effectiveness of antibiotics is reduced due to antibiotic-resistant pathogens. Thus, selecting the appropriate alternative antimicrobials for local delivery systems is correlated with successful infection management. We evaluated immobilization of the S. aureus specific bacteriophages in clinically recognized biopolymers, i.e., chitosan and alginate, to control the release profile of the antimicrobials. The high-titre S. aureus specific bacteriophages were prepared from commercial bacteriophage cocktails. The polymer mixtures with the propagated bacteriophages were then prepared. The stability of the S. aureus bacteriophages in the biopolymer solutions was assessed. In the case of chitosan, no plaques indicating the presence of the lytic bacteriophages were observed. The titre reduction of the S. aureus bacteriophages in the Na-alginate was below 1 log unit. Furthermore, the bacteriophages retained their lytic activity in the alginate after crosslinking with Ca2+ ions. The release of the lytic S. aureus bacteriophages from the Ca-alginate matrices in the TRIS-HCl buffer solution (pH 7.4 ± 0.2) was determined. After 72 h-0.292 ± 0.021% of bacteriophages from the Ca-alginate matrices were released. Thus, sustained release of the lytic S. aureus bacteriophages can be ensured.

Phage-Based Control of Methicillin Resistant Staphylococcus aureus in a Galleria mellonella Model of Implant-Associated Infection

Staphylococcus aureus implant-associated infections are difficult to treat because of the ability of bacteria to form biofilm on medical devices. Here, the efficacy of Sb-1 to control or prevent S. aureus colonization on medical foreign bodies was investigated in a Galleria mellonella larval infection model. For colonization control assays, sterile K-wires were implanted into larva prolegs. After 2 days, larvae were infected with methicillin-resistant S. aureus ATCC 43300 and incubated at 37 °C for a further 2 days, when treatments with either daptomycin (4 mg/kg), Sb-1 (10⁷ PFUs) or a combination of them (3 x/day) were started. For biofilm prevention assays, larvae were pre-treated with either vancomycin (10 mg/kg) or Sb-1 (10⁷ PFUs) before the S. aureus infection. In both experimental settings, K-wires were explanted for colony counting two days after treatment. In comparison to the untreated control, more than a 4 log¹⁰ CFU and 1 log¹⁰ CFU reduction was observed on K-wires recovered from larvae treated with the Sb-1/daptomycin combination and with their singular administration, respectively. Moreover, pre-infection treatment with Sb-1 was found to prevent K-wire colonization, similarly to vancomycin. Taken together, the obtained results demonstrated the strong potential of the Sb-1 antibiotic combinatory administration or the Sb-1 pretreatment to control or prevent S. aureus-associated implant infections.

Prevalence and Antibiogram of Escherichia coli and Staphylococcus spp. Isolated from Cattle Milk Products Sold in Juja Sub-County, Kenya

Dairy ruminant milk provides a conducive environment for bacterial proliferation. In animals, these bacteria are exposed to antibiotics, whose overuse has led to increased cases of drug resistance. A cross-sectional study was conducted on milk and milk products vended in Juja Sub-County, Kenya to determine the prevalence of bacteria and antibiogram of Staphylococcus spp. and Escherichia coli. A total of 169 milk samples were obtained from various outlets in the study area. Milk samples were cultured and isolated bacteria were identified using standard bacteriological procedures. Various bacteria (15 species) were isolated in different proportions. Staphylococcus spp. and E. coli were isolated from 25.4% and 11.8% of the collected samples, respectively. The highest number of Staphylococcus spp. were isolated from raw milk (n = 34) while the highest number of E. coli where isolated from fermented milk (n = 15). Staphylococcus spp. and E. coli isolates were subjected to antimicrobial susceptibility tests using CLSI guidelines. The Staphylococcus spp. isolates were highly resistant to penicillin G (93%) but susceptible to norfloxacin (100%), gentamicin (90.6%), and chloramphenicol (86%). The E. coli isolates were highly resistant to cephalexin (85%) and ceftazidime (60%) but susceptible to chloramphenicol (100%), norfloxacin (95%), gentamicin (95%), azithromycin (95%) and cefepime (80%). Furthermore, 44.3% of Staphylococcus spp. and 50% of E. coli isolates had a Multiple Antibiotic Resistance (MAR) Index greater than 0.2. This implies that these bacteria were high-risk bacteria whose treatment with current antibiotics would be challenging. The high prevalence and multidrug resistance patterns shown by the Staphylococcus spp. and E. coli isolated from milk products in Juja Sub-county highlights the importance of proper handling and processing of milk from the farm to consumers. This will in turn reduce the possibility of zoonotic transfer of multidrug-resistant bacteria.

Wound fluid ceftriaxone concentrations after local application with calcium sulphate as carrier material in the treatment of orthopaedic device-associated hip infections

Aims

There is a considerable challenge in treating bone infections and orthopaedic device-associated infection (ODAI), partly due to impaired penetration of systemically administrated antibiotics at the site of infection. This may be circumvented by local drug administration. Knowledge of the release kinetics from any carrier material is essential for proper application. Ceftriaxone shows a particular constant release from calcium sulphate (CaSO4) in vitro, and is particularly effective against streptococci and a large portion of Gram-negative bacteria. We present the clinical release kinetics of ceftriaxone-loaded CaSO4 applied locally to treat ODAI.

Methods

A total of 30 operations with ceftriaxone-loaded CaSO4 had been performed in 28 patients. Ceftriaxone was applied as a single local antibiotic in 21 operations and combined with vancomycin in eight operations, and in an additional operation with vancomycin and amphotericin B. Sampling of wound fluid was performed from drains or aspirations. Ceftriaxone concentrations were measured by liquid chromatography with tandem mass spectrometry (LC-MS/MS).

Results

A total of 37 wound fluid concentrations from 16 operations performed in 14 patients were collected. The ceftriaxone concentrations remained approximately within a range of 100 to 200 mg/l up to three weeks. The median concentration was 108.9 mg/l (interquartile range 98.8 to 142.5) within the first ten days. No systemic adverse reactions were observed.

Conclusion

Our study highlights new clinical data of locally administered ceftriaxone with CaSO4 as carrier material. The near-constant release of ceftriaxone from CaSO4 observed in vitro could be confirmed in vivo. The concentrations remained below known local toxicity thresholds. Cite this article: Bone Joint Res 2022;11(11):835–842.

Remote Eradication of Bacteria on Orthopedic Implants via Delayed Delivery of Polycaprolactone Stabilized Polyvinylpyrrolidone Iodine

Bacteria-associated late infection of the orthopedic devices would further lead to the failure of the implantation. However, present ordinary antimicrobial strategies usually deal with early infection but fail to combat the late infection of the implants due to the burst release of the antibiotics. Thus, to fabricate long-term antimicrobial (early antibacterial, late antibacterial) orthopedic implants is essential to address this issue. Herein, we developed a sophisticated MAO-I₂-PCLx coating system incorporating an underlying iodine layer and an upper layer of polycaprolactone (PCL)-controlled coating, which could effectively eradicate the late bacterial infection throughout the implantation. Firstly, micro-arc oxidation was used to form a microarray tubular structure on the surface of the implants, laying the foundation for iodine loading and PCL bonding. Secondly, electrophoresis was applied to load iodine in the tubular structure as an efficient bactericidal agent. Finally, the surface-bonded PCL coating acts as a controller to regulate the release of iodine. The hybrid coatings displayed great stability and control release capacity. Excellent antibacterial ability was validated at 30 days post-implantation via in vitro experiments and in vivo rat osteomyelitis model. Expectedly, it can become a promising bench-to-bedside strategy for current infection challenges in the orthopedic field.

Efficacy of an Antibiotic Loaded Ceramic-Based Bone Graft Substitute for the Treatment of Infected Non-Unions

The treatment of non-unions is often complicated by segmental bone defects and bacterial colonization. Because of the limited availability of autologous bone grafts, tissue engineering focuses on antibiotic-loaded bone graft substitutes. HACaS+G is a resorbable calcium sulphate-hydroxyapatite loaded with gentamicin. The osteoinductive, osteoconductive, and anti-infective effect of HACaS+G has already been demonstrated in clinical studies on patients with chronic osteomyelitis. However, especially for the treatment of infected non-unions with segmental bone defects by HACaS+G, reliable clinical testing is difficult and sufficient experimental data are lacking. We used an already established sequential animal model in infected and non-infected rat femora to investigate the osteoinductive, osteoconductive, and anti-infective efficacy of HACaS+G for the treatment of infected non-unions. In biomechanical testing, bone consolidation could not be observed under infected and non-infected conditions. Only a prophylactic effect against infections, but no eradication, could be verified in the microbiological analysis. Using µ-CT scans and histology, osteoinduction was detected in both the infected and non-infected bone, whereas osteoconduction occurred only in the non-infected setting. Our data showed that HACaS+G is osteoinductive, but does not have added benefits in infected non-unions in terms of osteoconduction and mechanical bone stability, especially in those with segmental bone defects.

Bioengineering Approaches to Fight against Orthopedic Biomaterials Related-Infections

One of the most serious complications following the implantation of orthopedic biomaterials is the development of infection. Orthopedic implant-related infections do not only entail clinical problems and patient suffering, but also cause a burden on healthcare care systems. Additionally, the ageing of the world population, in particular in developed countries, has led to an increase in the population above 60 years. This is a significantly vulnerable population segment insofar as biomaterials use is concerned. Implanted materials are highly susceptible to bacterial and fungal colonization and the consequent infection. These microorganisms are often opportunistic, taking advantage of the weakening of the body defenses at the implant surface–tissue interface to attach to tissues or implant surfaces, instigating biofilm formation and subsequent development of infection. The establishment of biofilm leads to tissue destruction, systemic dissemination of the pathogen, and dysfunction of the implant/bone joint, leading to implant failure. Moreover, the contaminated implant can be a reservoir for infection of the surrounding tissue where microorganisms are protected. Therefore, the biofilm increases the pathogenesis of infection since that structure offers protection against host defenses and antimicrobial therapies. Additionally, the rapid emergence of bacterial strains resistant to antibiotics prompted the development of new alternative approaches to prevent and control implant-related infections. Several concepts and approaches have been developed to obtain biomaterials endowed with anti-infective properties. In this review, several anti-infective strategies based on biomaterial engineering are described and discussed in terms of design and fabrication, mechanisms of action, benefits, and drawbacks for preventing and treating orthopaedic biomaterials-related infections.

Microbial resistance to nanotechnologies: An important but understudied consideration using antimicrobial nanotechnologies in orthopaedic implants

Microbial resistance to current antibiotics therapies is a major cause of implant failure and adverse clinical outcomes in orthopaedic surgery. Recent developments in advanced antimicrobial nanotechnologies provide numerous opportunities to effective remove resistant bacteria and prevent resistance from occurring through unique mechanisms. With tunable physicochemical properties, nanomaterials can be designed to be bactericidal, antifouling, immunomodulating, and capable of delivering antibacterial compounds to the infection region with spatiotemporal accuracy. Despite its substantial advancement, an important, but under-explored area, is potential microbial resistance to nanomaterials and how this can impact the clinical use of antimicrobial nanotechnologies. This review aims to provide a better understanding of nanomaterial-associated microbial resistance to accelerate bench-to-bedside translations of emerging nanotechnologies for effective control of implant associated infections.

Can intracellular Staphylococcus aureus in osteomyelitis be treated using current antibiotics? A systematic review and narrative synthesis

Approximately 40% of treatments of chronic and recurrent osteomyelitis fail in part due to bacterial persistence. Staphylococcus aureus, the predominant pathogen in human osteomyelitis, is known to persist by phenotypic adaptation as small-colony variants (SCVs) and by formation of intracellular reservoirs, including those in major bone cell types, reducing susceptibility to antibiotics. Intracellular infections with S. aureus are difficult to treat; however, there are no evidence-based clinical guidelines addressing these infections in osteomyelitis. We conducted a systematic review of the literature to determine the demonstrated efficacy of all antibiotics against intracellular S. aureus relevant to osteomyelitis, including protein biosynthesis inhibitors (lincosamides, streptogramins, macrolides, oxazolidines, tetracyclines, fusidic acid, and aminoglycosides), enzyme inhibitors (fluoroquinolones and ansamycines), and cell wall inhibitors (beta-lactam inhibitors, glycopeptides, fosfomycin, and lipopeptides). The PubMed and Embase databases were screened for articles related to intracellular S. aureus infections that compared the effectiveness of multiple antibiotics or a single antibiotic together with another treatment, which resulted in 34 full-text articles fitting the inclusion criteria. The combined findings of these studies were largely inconclusive, most likely due to the plethora of methodologies utilized. Therefore, the reported findings in the context of the models employed and possible solutions for improved understanding are explored here. While rifampicin, oritavancin, linezolid, moxifloxacin and oxacillin were identified as the most effective potential intracellular treatments, the scientific evidence for these is still relatively weak. We advocate for more standardized research on determining the intracellular effectiveness of antibiotics in S. aureus osteomyelitis to improve treatments and patient outcomes.

Early Postoperative Infections After Closed Reduction and Percutaneous Pinning in Type II and Type III Pediatric Supracondylar Humerus Fractures

BACKGROUND

Supracondylar humerus fractures (SCHF) are the most common elbow fracture type in children, and one of the most common pediatric fracture types overall. Excellent outcomes are generally reported with closed reduction and pinning (CRPP), but the technique involves leaving the pins outside the skin. External pins can act as a nidus for infection. We characterize the infection complications from SCHF treatment at a single-centre tertiary children's hospital over 10 years. This is the largest series on infectious outcomes after CRPP of SCHF reported to date.

METHODS

Pediatric patients undergoing CRPP for a type II or type III SCHF from 2011 to 2021 with postsurgical infections within 90 days were identified. Demographic and clinical data were retrieved from medical records. Descriptive statistics were estimated and reported as means or medians with range values or counts with percentages.

RESULTS

A total of 18 patients met inclusion criteria, 10 and 8 with type II and III SCHF, respectively. The average age at diagnosis of fracture was 4.7 (2 to 9) years. The average operating time for the index surgery was 29 minutes (12 to 42). The average number of postoperative days until pin removal was 29.8 (18 to 52), and the average number of postoperative days until readmission or visit with symptoms was 38.9 (18 to 77). There was a documented history of a wet cast in 6 patients (33%). Ten (56%) patients presented with fever, and the most common positive culture was methicillin-sensitive Staphylococcus aureus (9, 50%). Thirteen (72%) patients returned to the operating room for incision and drainage. There were no cases with continued complications after the original infection after a median follow-up of 63 days (8 to 559). Infection after CRPP of SCHF is a rare adverse event. In our series, it was most often associated with common pathogens and wet casts. The necessity of return to the operating room will vary with the presentation, but if efficaciously treated afterwards with oral antibiotics, there is a low chance of recurrence or subsequent complications. Patients should be carefully instructed in cast care and demonstrate understanding of risks and complications, and to contact their orthopaedist if their cast demonstrates lack of integrity.

LEVEL OF EVIDENCE

Prognostic level IV.

Mg-, Zn-, and Fe-Based Alloys With Antibacterial Properties as Orthopedic Implant Materials

Implant-associated infection (IAI) is one of the major challenges in orthopedic surgery. The development of implants with inherent antibacterial properties is an effective strategy to resolve this issue. In recent years, biodegradable alloy materials have received considerable attention because of their superior comprehensive performance in the field of orthopedic implants. Studies on biodegradable alloy orthopedic implants with antibacterial properties have gradually increased. This review summarizes the recent advances in biodegradable magnesium- (Mg-), iron- (Fe-), and zinc- (Zn-) based alloys with antibacterial properties as orthopedic implant materials. The antibacterial mechanisms of these alloy materials are also outlined, thus providing more basis and insights on the design and application of biodegradable alloys with antibacterial properties as orthopedic implants.

An Antibiotic-Loaded Hydrogel Demonstrates Efficacy as Prophylaxis and Treatment in a Large Animal Model of Orthopaedic Device-Related Infection

Local antibiotic therapy is increasingly being recognised for its role in preventing and treating orthopaedic device-related infection (ODRI). A bioresorbable, injectable gentamicin-loaded hydrogel has been developed to deliver local antibiotics at the time of surgery with potential for both prevention and treatment of ODRI. In a prophylaxis model, the antibiotic hydrogel was compared with systemic perioperative antibiotic prophylaxis alone in twelve sheep (six per group) at the time of intramedullary (IM) nail insertion to the tibia, which was inoculated with methicillin-sensitive Staphylococcus aureus (MSSA). In a treatment model of single-stage revision surgery, adjunctive antibiotic-loaded hydrogel was compared with systemic antibiotics alone in a single stage revision of MSSA infection associated with a tibia intramedullary nail in eleven sheep (five/six per group). The primary endpoint was quantitative microbiological results of soft tissue, bone and sonicate fluid from explanted hardware at the time of euthanasia. At euthanasia, the control sheep that received no local antibiotics in the prophylaxis model were all culture-positive (median 1x10⁸, range 7x10⁶-3x10⁸ colony forming units, CFU) while only two of six sheep receiving local gentamicin had any culture positive biopsies (median 1x10¹, range 0 - 1x10⁵ CFU). For the treatment model, sheep receiving only systemic antibiotics were all culture-positive (median 8x10⁵, range 2x10³- 9x10⁶ CFU) while only two of six sheep treated with gentamicin-loaded hydrogel had any culture positive biopsies (median 3x10², range 0 - 7x10⁴ CFU). Local gentamicin concentrations measured in extracellular fluid in the tibial canal show a burst release of gentamicin from the hydrogel. Serum gentamicin concentrations peaked in both models at one day post application and were below detection limit thereafter. This study has demonstrated the effective use of a locally delivered antibiotic hydrogel for both the prevention and treatment of ODRI that is superior to that of systemic antibiotics alone. Future studies will endeavour to translate from preclinical to clinical research trials.

Recent Advances in Multifunctional Hydrogels for the Treatment of Osteomyelitis

Osteomyelitis (OM), a devastating disease caused by microbial infection of bones, remains a major challenge for orthopedic surgeons. Conventional approaches for prevention and treatment of OM are unsatisfactory. Various alternative strategies have been proposed, among which, hydrogel-based strategies have demonstrated potential due to their unique properties, including loadable, implantable, injectable, printable, degradable, and responsive to stimuli. Several protocols, including different hydrogel designs, selection of antimicrobial agent, co-administration of bone morphogenetic protein 2 (BMP 2), and nanoparticles, have been shown to improve the biological properties, including antimicrobial effects, osteo-induction, and controlled drug delivery. In this review, we describe the current and future directions for designing hydrogels and their applications to improve the biological response to OM in vivo.

Synergistic Antibacterial Effect of Zinc Oxide Nanoparticles and Polymorphonuclear Neutrophils

Zinc oxide nanoparticles (ZnONPs) are inorganic nano-biomaterials with excellent antimicrobial properties. However, their effects on the anti-infection ability of the innate immune system remains poorly understood. The aim of the present study was to explore the potential immunomodulatory effects of ZnONPs on the innate immune system, represented by polymorphonuclear leukocytes (PMNs), and determine whether they can act synergistically to resist pathogen infections. In vitro experiment showed that ZnONPs not only exhibit obvious antibacterial activity at biocompatible concentrations but also enhance the antibacterial property of PMNs. In vivo experiments demonstrated the antibacterial effect of ZnONPs, accompanied by more infiltration of subcutaneous immune cells. Further ex vivo and in vitro experiments revealed that ZnONPs enhanced the migration of PMNs, promoted their bacterial phagocytosis efficiency, proinflammatory cytokine (TNF-α, IL-1β, and IL-6) expression, and reactive oxygen species (ROS) production. In summary, this study revealed potential synergistic effects of ZnONPs on PMNs to resist pathogen infection and the underlying mechanisms. The findings suggest that attempts should be made to fabricate and apply biomaterials in order to maximize their synergy with the innate immune system, thus promoting the host’s resistance to pathogen invasion.

Comparison of Automated Ribotyping, spa Typing, and MLST in 108 Clinical Isolates of Staphylococcus aureus from Orthopedic Infections

108 isolates of Staphylococcus aureus, belonging to six large ribogroups according to the automated Ribo-Printer^® system, were studied with two highly used molecular methods for epidemiological studies, namely multi-locus sequence typing (MLST) and spa typing, followed by BURP and eBURST v3 analysis for clustering spa types and sequence (ST) types. The aim was to evaluate whether automated ribotyping could be considered a useful screening tool for identifying S. aureus genetic lineages with respect to spa typing and MLST. Clarifying the relationship of riboprinting with these typing methods and establishing whether ribogroups fit single clonal complexes were two main objectives. Further information on the genetic profile of the isolates was obtained from agr typing and the search for the mecA, tst genes, and the IS256 insertion sequence. Automated ribotyping has been shown to predict spa clonal complexes and MLST clonal complexes. The high cost and lower discriminatory power of automated ribotyping compared to spa and MSLT typing could be an obstacle to fine genotyping analyzes, especially when high discriminatory power is required. On the other hand, numerous advantages such as automation, ease and speed of execution, stability, typeability and reproducibility make ribotyping a reliable method to be juxtaposed to gold standard methods.

Micrococcal Nuclease stimulates Staphylococcus aureus Biofilm Formation in a Murine Implant Infection Model

Advancements in contemporary medicine have led to an increasing life expectancy which has broadened the application of biomaterial implants. As each implant procedure has an innate risk of infection, the number of biomaterial-associated infections keeps rising. Staphylococcus aureus causes 34% of such infections and is known as a potent biofilm producer. By secreting micrococcal nuclease S. aureus is able to escape neutrophil extracellular traps by cleaving their DNA-backbone. Also, micrococcal nuclease potentially limits biofilm growth and adhesion by cleaving extracellular DNA, an important constituent of biofilms. This study aimed to evaluate the impact of micrococcal nuclease on infection persistence and biofilm formation in a murine biomaterial-associated infection-model with polyvinylidene-fluoride mesh implants inoculated with bioluminescent S. aureus or its isogenic micrococcal nuclease deficient mutant. Supported by results based on in-vivo bioluminescence imaging, ex-vivo colony forming unit counts, and histological analysis it was found that production of micrococcal nuclease enables S. aureus bacteria to evade the immune response around an implant resulting in a persistent infection. As a novel finding, histological analysis provided clear indications that the production of micrococcal nuclease stimulates S. aureus to form biofilms, the presence of which extended neutrophil extracellular trap formation up to 13 days after mesh implantation. Since micrococcal nuclease production appeared vital for the persistence of S. aureus biomaterial-associated infection, targeting its production could be a novel strategy in preventing biomaterial-associated infection.

Human monoclonal antibodies against Staphylococcus aureus surface antigens recognize in vitro and in vivo biofilm

Implant-associated Staphylococcus aureus infections are difficult to treat because of biofilm formation. Bacteria in a biofilm are often insensitive to antibiotics and host immunity. Monoclonal antibodies (mAbs) could provide an alternative approach to improve the diagnosis and potential treatment of biofilm-related infections. Here, we show that mAbs targeting common surface components of S. aureus can recognize clinically relevant biofilm types. The mAbs were also shown to bind a collection of clinical isolates derived from different biofilm-associated infections (endocarditis, prosthetic joint, catheter). We identify two groups of antibodies: one group that uniquely binds S. aureus in biofilm state and one that recognizes S. aureus in both biofilm and planktonic state. Furthermore, we show that a mAb recognizing wall teichoic acid (clone 4497) specifically localizes to a subcutaneously implanted pre-colonized catheter in mice. In conclusion, we demonstrate the capacity of several human mAbs to detect S. aureus biofilms in vitro and in vivo.

Therapeutic evaluation of immunomodulators in reducing surgical wound infection

Despite many advances in infection control practices, including prophylactic antibiotics, surgical site infections (SSIs) remain a significant cause of morbidity, prolonged hospitalization, and death worldwide. Our innate immune system possesses a multitude of powerful antimicrobial strategies which make it highly effective in combating bacterial, fungal, and viral infections. However, pathogens use various stealth mechanisms to avoid the innate immune system, which in turn buy them time to colonize wounds and damage tissues at surgical sites. We hypothesized that immunomodulators that can jumpstart and activate innate immune responses at surgical sites, would likely reduce infection at surgical sites. We used three immunomodulators; fMLP (formyl-Methionine-Lysine-Proline), CCL3 (MIP-1α), and LPS (Lipopolysaccharide), based on their documented ability to elicit strong inflammatory responses; in a surgical wound infection model with Pseudomonas aeruginosa to evaluate our hypothesis. Our data indicate that one-time topical treatment with these immunomodulators at low doses significantly increased proinflammatory responses in infected and uninfected surgical wounds and were as effective, (or even better), than a potent prophylactic antibiotic (Tobramycin) in reducing P. aeruginosa infection in wounds. Our data further show that immunomodulators did not have adverse effects on tissue repair and wound healing processes. Rather, they enhanced healing in both infected and uninfected wounds. Collectively, our data demonstrate that harnessing the power of the innate immune system by immunomodulators can significantly boost infection control and potentially stimulate healing. We propose that topical treatment with these immunomodulators at the time of surgery may have therapeutic potential in combating SSI, alone or in combination with prophylactic antibiotics.

An Engineered Multimodular Enzybiotic against Methicillin-Resistant Staphylococcus aureus

Development of multidrug antibiotic resistance in bacteria is a predicament encountered worldwide. Researchers are in a constant hunt to develop effective antimicrobial agents to counter these dreadful pathogenic bacteria. Here we describe a chimerically engineered multimodular enzybiotic to treat a clinical isolate of methicillin-resistant Staphylococcus aureus (S. aureus). The cell wall binding domain of phage ϕ11 endolysin was replaced with a truncated and more potent cell wall binding domain from a completely unrelated protein from a different phage. The engineered enzybiotic showed strong activity against clinically relevant methicillin-resistant Staphylococcus aureus. In spite of a multimodular peptidoglycan cleaving catalytic domain, the engineered enzybiotic could not exhibit its activity against a veterinary isolate of S. aureus. Our studies point out that novel antimicrobial proteins can be genetically engineered. Moreover, the cell wall binding domain of the engineered protein is indispensable for a strong binding and stability of the proteins.

Interactions between the foreign body reaction and Staphylococcus aureus biomaterial-associated infection. Winning strategies in the derby on biomaterial implant surfaces

Biomaterial-associated infections (BAIs) are an increasing problem where antibiotic therapies are often ineffective. The design of novel strategies to prevent or combat infection requires a better understanding of how an implanted foreign body prevents the immune system from eradicating surface-colonizing pathogens. The objective of this review is to chart factors resulting in sub-optimal clearance of Staphylococcus aureus bacteria involved in BAIs. To this end, we first describe three categories of bacterial mechanisms to counter the host immune system around foreign bodies: direct interaction with host cells, modulation of intercellular communication, and evasion of the immune system. These mechanisms take place in a time frame that differentiates sterile foreign body reactions, BAIs, and soft tissue infections. In addition, we identify experimental interventions in S. aureus BAI that may impact infectious mechanisms. Most experimental treatments modulate the host response to infection or alter the course of BAI through implant surface modulation. In conclusion, the first week after implantation and infection is crucial for the establishment of an S. aureus biofilm that resists the local immune reaction and antibiotic treatment. Although established and chronic S. aureus BAI is still treatable and manageable, the focus of interventions should lie on this first period.

Clindamycin-loaded titanium prevents implant-related infection through blocking biofilm formation

Implant-related infection is a disastrous complication. Surface modification of titanium is considered as an important strategy to prevent implant-related infection. However, there is no recognized surface modification strategy that can be applied in clinic so far. We explored a new strategy of coating. The clindamycin-loaded titanium was constructed by layer-by-layer self-assembly. The release of clindamycin from titanium was detected through high performance liquid chromatography. Different titanium was co-cultured with Staphylococcus aureus for 24 h in vitro, then the effect of different titanium on bacterial colonization and biofilm formation was determined by spread plate method and scanning electron microscopy. Cytotoxicity and cytocompatibility of clindamycin-loaded titanium on MC3T3-E1 cells were measured by CCK8. The antibacterial ability of clindamycin-loaded titanium in vivo was also evaluated using a rat model of osteomyelitis. The number of osteoclasts in bone defect was observed by tartrate-resistant acid phosphatase staining. Bacterial burden of surrounding tissues around the site of infection was calculated by tissue homogenate and colony count. Clindamycin-loaded titanium could release clindamycin slowly within 160 h. It reduced bacterial colonization by three orders of magnitude compare to control (p < .05) and inhibits biofilm formation in vitro. Cells proliferation and adhesion were similar on three titanium surfaces (p > .05). In vivo, clindamycin-loaded titanium improved bone healing, reduced microbial burden, and decreased the number of osteoclasts compared control titanium in the rat model of osteomyelitis. This study demonstrated that clindamycin-loaded titanium exhibited good biocompatibility, and showed antibacterial activity both in vivo and in vitro. It is promising and might have potential for clinical application.