New Trends in Diagnosis and Control Strategies for Implant Infections

Practical Guidance for Clinical Microbiology Laboratories: Microbiologic diagnosis of implant-associated infections

SUMMARYImplant-associated infections (IAIs) pose serious threats to patients and can be associated with significant morbidity and mortality. These infections may be difficult to diagnose due, in part, to biofilm formation on device surfaces, and because even when microbes are found, their clinical significance may be unclear. Despite recent advances in laboratory testing, IAIs remain a diagnostic challenge. From a therapeutic standpoint, many IAIs currently require device removal and prolonged courses of antimicrobial therapy to effect a cure. Therefore, making an accurate diagnosis, defining both the presence of infection and the involved microorganisms, is paramount. The sensitivity of standard microbial culture for IAI diagnosis varies depending on the type of IAI, the specimen analyzed, and the culture technique(s) used. Although IAI-specific culture-based diagnostics have been described, the challenge of culture-negative IAIs remains. Given this, molecular assays, including both nucleic acid amplification tests and next-generation sequencing-based assays, have been used. In this review, an overview of these challenging infections is presented, as well as an approach to their diagnosis from a microbiologic perspective.

Photodynamic inactivation of bacteria: Why it is not enough to excite a photosensitizer

BACKGROUND

The development of multidrug resistance (MDR) in infectious agents is one of the most serious global problems facing humanity. Antimicrobial photodynamic therapy (APDT) shows encouraging results in the fight against MDR pathogens, including those in biofilms.

METHODS

Photosensitizers (PS), monocationic methylene blue, polycationic and polyanionic derivatives of phthalocyanines, electroneutral and polycationic derivatives of bacteriochlorin were used to study photodynamic inactivation of Gram-positive and Gram-negative planktonic bacteria and biofilms under LED irradiation. Zeta potential measurements, confocal fluorescence imaging, and coarse-grained modeling were used to evaluate the interactions of PS with bacteria. PS aggregation and photobleaching were studied using absorption and fluorescence spectroscopy.

RESULTS

The main approaches to ensure high efficiency of bacteria photosensitization are analyzed.

CONCLUSIONS

PS must maintain a delicate balance between binding to exocellular and external structures of bacterial cells and penetration through the cell wall so as not to get stuck on the way to photooxidation-sensitive structures of the bacterial cell.

It is the time for quorum sensing inhibition as alternative strategy of antimicrobial therapy

Multiple drug resistance poses a significant threat to public health worldwide, with a substantial increase in morbidity and mortality rates. Consequently, searching for novel strategies to control microbial pathogenicity is necessary. With the aid of auto-inducers (AIs), quorum sensing (QS) regulates bacterial virulence factors through cell-to-cell signaling networks. AIs are small signaling molecules produced during the stationary phase. When bacterial cultures reach a certain level of growth, these molecules regulate the expression of the bound genes by acting as mirrors that reflect the inoculum density.Gram-positive bacteria use the peptide derivatives of these signaling molecules, whereas Gram-negative bacteria use the fatty acid derivatives, and the majority of bacteria can use both types to modulate the expression of the target gene. Numerous natural and synthetic QS inhibitors (QSIs) have been developed to reduce microbial pathogenesis. Applications of QSI are vital to human health, as well as fisheries and aquaculture, agriculture, and water treatment. Video Abstract.

Therapeutic Strategies against Biofilm Infections

A biofilm is an aggregation of surface-associated microbial cells that is confined in an extracellular polymeric substance (EPS) matrix. Infections caused by microbes that form biofilms are linked to a variety of animals, including insects and humans. Antibiotics and other antimicrobials can be used to remove or eradicate biofilms in order to treat infections. However, due to biofilm resistance to antibiotics and antimicrobials, clinical observations and experimental research clearly demonstrates that antibiotic and antimicrobial therapies alone are frequently insufficient to completely eradicate biofilm infections. Therefore, it becomes crucial and urgent for clinicians to properly treat biofilm infections with currently available antimicrobials and analyze the results. Numerous biofilm-fighting strategies have been developed as a result of advancements in nanoparticle synthesis with an emphasis on metal oxide np. This review focuses on several therapeutic strategies that are currently being used and also those that could be developed in the future. These strategies aim to address important structural and functional aspects of microbial biofilms as well as biofilms' mechanisms for drug resistance, including the EPS matrix, quorum sensing (QS), and dormant cell targeting. The NPs have demonstrated significant efficacy against bacterial biofilms in a variety of bacterial species. To overcome resistance, treatments such as nanotechnology, quorum sensing, and photodynamic therapy could be used.

Biofilms-What Should the Orthopedic Surgeon know?

Background

Musculoskeletal infections are a major source of morbidity for orthopedic and trauma patients, are associated with prolonged treatment times, and, unfortunately, suffer from poor functional outcomes. Further complicating the issue, antimicrobial resistance (AMR) is increasingly impacting the treatment of musculoskeletal infections with a diminishing repertoire of effective antibiotic agents for some highly resistant pathogens. Most orthopedic surgical procedures involve implants, and the formation of bacterial biofilms on these implants is now recognized as a major factor contributing to the failure of antibiotic therapy in orthopedic surgery.

Methods

This review presents an overview of the types, structure, formation, and pathogenesis of biofilms as they pertain to musculoskeletal infections. Furthermore, it describes the key concepts in the management of biofilms and future perspectives for the better treatment of patients with biofilm-related musculoskeletal infections.

Results

A bacterial biofilm is a dynamic, living conglomerate of bacteria encased in an extracapsular polysaccharide matrix (EPS). Biofilms are a natural mode of survival for virtually all bacterial species, including both Grampositive and Gram-negative bacteria, as well as fungi. The biofilm model of growth confers resistance by several well-defined mechanisms regardless of the species of the microorganism. In most cases, biofilm management often necessitates radical measures to ensure eradication including both surgical and medical interventions.

Conclusions

Orthopedic surgeons should be aware of the key concepts pertaining to biofilms, and the impact that these can have on clinical practice.

Engineering biomaterials to 3D-print scaffolds for bone regeneration: practical and theoretical consideration

There are more than 2 million bone grafting procedures performed annually in the US alone. Despite significant efforts, the repair of large segmental bone defects is a substantial clinical challenge which requires bone substitute materials or a bone graft. The available biomaterials lack the adequate mechanical strength to withstand the static and dynamic loads while maintaining sufficient porosity to facilitate cell in-growth and vascularization during bone tissue regeneration. A wide range of advanced biomaterials are being currently designed to mimic the physical as well as the chemical composition of a bone by forming polymer blends, polymer-ceramic and polymer-degradable metal composites. Transforming these novel biomaterials into porous and load-bearing structures via three-dimensional printing (3DP) has emerged as a popular manufacturing technique to develop engineered bone grafts. 3DP has been adopted as a versatile tool to design and develop bone grafts that satisfy porosity and mechanical requirements while having the ability to form grafts of varied shapes and sizes to meet the physiological requirements. In addition to providing surfaces for cell attachment and eventual bone formation, these bone grafts also have to provide physical support during the repair process. Hence, the mechanical competence of the 3D-printed scaffold plays a key role in the success of the implant. In this review, we present various recent strategies that have been utilized to design and develop robust biomaterials that can be deployed for 3D-printing bone substitutes. The article also reviews some of the practical, theoretical and biological considerations adopted in the 3D-structure design and development for bone tissue engineering.

Environmental, Microbiological, and Immunological Features of Bacterial Biofilms Associated with Implanted Medical Devices

The spread of biofilms on medical implants represents one of the principal triggers of persistent and chronic infections in clinical settings, and it has been the subject of many studies in the past few years, with most of them focused on prosthetic joint infections. We review here recent works on biofilm formation and microbial colonization on a large variety of indwelling devices, ranging from heart valves and pacemakers to urological and breast implants and from biliary stents and endoscopic tubes to contact lenses and neurosurgical implants. We focus on bacterial abundance and distribution across different devices and body sites and on the role of environmental features, such as the presence of fluid flow and properties of the implant surface, as well as on the interplay between bacterial colonization and the response of the human immune system.

Clinical utility of sonication for diagnosing infection and colonization of cardiovascular implantable electronic devices

Our study aimed to evaluate the sensitivity of the sonication tool for the microbiological diagnosis of cardiovascular implantable electronic device infections (CIEDIs). The extracted cardiac implants of 52 patients were assessed: 19 with CIEDI and 33 with elective generator replacement or revision without clinical infection. Sonication fluid culture of explanted CIEDs yielded higher numbers of microorganisms than pocket tissue or swab cultures. The sensitivity of sonication fluid culture was significantly higher than that of pocket swab and tissue culture for microbiological diagnosis of CIEDI. The microorganisms isolated most frequently via sonication of explanted CIEDs were Gram-positive cocci (70%), of which 50% was coagulase-negative Staphylococcus. Sonication fluid culture detected colonization in 36.4% of the non-infected patients. Sonication fluid culture represents a promising diagnostic strategy with increased sensitivity compared to conventional culture methods for microbiological diagnosis of cardiac devices associated with infection and colonization.

Novel strategies to diagnose prosthetic or native bone and joint infections

INTRODUCTION

Bone and Joint Infections (BJI) are medically important, costly and occur in native and prosthetic joints. Arthroplasties will increase significantly in absolute numbers over time as well as the incidence of Prosthetic Joint Infections (PJI). Diagnosis of BJI and PJI is sub-optimal. The available diagnostic tests have variable effectiveness, are often below standard in sensitivity and/or specificity, and carry significant contamination risks during the collection of clinical samples. Improvement of diagnostics is urgently needed.

AREAS COVERED

We provide a narrative review on current and future diagnostic microbiology technologies. Pathogen identification, antibiotic resistance detection, and assessment of the epidemiology of infections via bacterial typing are considered useful for improved patient management. We confirm the continuing importance of culture methods and successful introduction of molecular, mass spectrometry-mediated and next-generation genome sequencing technologies. The diagnostic algorithms for BJI must be better defined, especially in the context of diversity of both disease phenotypes and clinical specimens rendered available.

EXPERT OPINION

Whether interventions in BJI or PJI are surgical or chemo-therapeutic (antibiotics and bacteriophages included), prior sensitive and specific pathogen detection remains a therapy-substantiating necessity. Innovative tests for earlier and more sensitive and specific detection of bacterial pathogens in BJI are urgently needed.

Biomaterials and technologies in the management of periprosthetic infection after total hip arthroplasty: An updated review

Although total hip arthroplasty (THA) is considered one of the most efficacious procedures for managing various hip conditions, failures due to different mechanisms are still being reported. Periprosthetic joint infection (PJI) is one of the devastating causes of failure and revision of THA. PJI carries a burden on the patient, the surgeon, and the health-care system. The diagnosis and management of PJIs carry many morbidities and increased treatment costs. The development of PJI is multifactorial, including issues related to the patient’s general condition, the surgeon’s efficiency, surgical technique, and the implants used. Recent advances in the area of diagnosis and predicting PJI as well as introducing new technologies and biomaterials update for the prevention and treatment of PJI. Local implant coatings, advancement in the bearing surfaces technologies, and new technologies such as immunotherapy and bacteriophage therapy were introduced and suggested as contemporary PJI eradication solutions. In this review, we aimed at discussing some of the newly introduced materials and technologies for the sake of PJI control.

Challenges of antibiotic resistance biofilms and potential combating strategies: a review

In this modern era, medicine is facing many alarming challenges. Among different challenges, antibiotics are gaining importance. Recent years have seen unprecedented increase in knowledge and understanding of various factors that are root cause of the spread and development of resistance in microbes against antibiotics. The infection results in the formation of microbial colonies which are termed as biofilms. However, it has been found that a multiple factors contribute in the formation of antimicrobial resistance. Due to higher dose of Minimum Bactericidal Concentration (MBC) as well as of Minimum Inhibitory Concentration (MIC), a large batch of antibiotics available today are of no use as they are ineffective against infections. Therefore, to control infections, there is dire need to adopt alternative treatment for biofilm infection other than antibiotics. This review highlights the latest techniques that are being used to cure the menace of biofilm infections. A wide range of mechanisms has been examined with particular attention towards avenues which can be proved fruitful in the treatment of biofilms. Besides, newer strategies, i.e., matrix centered are also discussed as alternative therapeutic techniques including modulating microbial metabolism, matrix degrading enzyme, photodynamic therapy, natural compounds quorum sensing and nanotechnology which are being used to disrupt extra polymeric substances (EPS) matrix of desired bacterial biofilms.

A distinctive release profile of vancomycin and tobramycin from a new and injectable polymeric dicalcium phosphate dehydrate cement (P-DCPD)

A novel injectable polymeric dicalcium phosphate dehydrate (P-DCPD) cement was developed with superior mechanical strength and excellent cohesion. The purpose of this study was to assess the in vitro performance of P-DCPD loaded with vancomycin (VAN-P), tobramycin (TOB-P) and combination of both (VAN/TOB-P) (10%, w/w). There is a distinctive release profile between VAN and TOB. VAN-P showed decreased initial burst (<30% within 3 d) and sustained VAN release (76% in 28 d). In the presence of TOB (VAN/TOB-P), >90% of VAN was released within 3 d (p < 0.05). Slow and limited TOB release was observed both in TOB-P (<5%) and in TOB/VAN-P (<1%) over 28 d. Zone of inhibition (ZOI) of Staphylococcus aureus growth showed that eluents collected from VAN-P had stronger and longer ZOI (28 d) than that from TOB-P (14 d, p < 0.05). Direct contact of VAN-P, TOB-P and VAN/TOB-P cements displayed persistent and strong ZOI for >3 weeks. Interestingly, the cement residues (28 d after drug release) still maintained strong ZOI ability. P-DCPD with or without antibiotics loading were nontoxic and had no inferior impacts on the growth of osteoblastic MC3T3 cells. VAN-P and TOB-P were injectable. No significant influence on setting time was observed in both VAN-P (11.7 ± 1.9 min) and VAN/TOB-P (10.8 ± 1.5 min) as compared to control (12.2 ± 2.6 min). We propose that a distinctive release profile of VAN and TOB observed is mainly due to different distribution pattern of VAN and TOB within P-DCPD matrix. A limited release of TOB might be due to the incorporation of TOB inside the crystalline lattice of P-DCPD crystals. Our data supported that the bactericidal efficacy of antibiotics-loaded P-DCPD is not only depend on the amount and velocity of antibiotics released, but also probably more on the direct contact of attached bacteria on the degrading cement surface.

Update on Intraoperative Cultures, Biofilms, and Modifiable Factors During Revision of Clinically Non-Infected Penile Implants

INTRODUCTION

Penile implants have a limited lifespan, and as the population using inflatable penile prostheses ages, revision surgery has become increasingly common. Devices are frequently cultured during non-infectious revision surgeries, providing a burgeoning of evidence of positive cultures without clinical infection. However, the clinical significance of these cultures remains unclear.

OBJECTIVES

We aim to review the current literature on culture results from revision surgery for clinically non-infected devices and summarize the available data to formulate a synopsis of clinically significant organisms and their significance and modifiable approaches to prosthesis surgery.

METHODS

A literature review was performed on 1 March, 2020 in PubMed and Google Scholar. Search terms centered on penile prosthesis revision surgery, cultures, and infection. Titles and abstracts were reviewed for topical relevance with emphasis placed on literature from the last 20 years. Most publications comprised small case series aside from a single meta-analysis.

RESULTS

Since 1995, seven series have been published examining culture positivity at the time of revision surgery for clinically non-infected devices. Isolated organisms are most commonly from the Staphylococcus genus with Staphylococcus epidermidis being the most frequently isolated organism on clinically non-infected devices. Reported culture positivity rates at the time of revision range between 9.8% and 80%.

CONCLUSION

Current literature pertaining to the clinical significance of culture positivity at the time of revision surgery for clinically non-infected penile prostheses is lacking; however, multiple series do report high rates of culture positivity. This does appear to confer a higher rate of subsequent infection and a lower revision-free survival. Staphylococcus epidermidis is the most commonly isolated organism followed by other members of the Staphylococcus genus. Further studies are needed to determine the impact of modifiable variables or techniques on asymptomatic culture positivity and the ideal technologies for biofilm prevention. Nosé BD, Grimberg DCD, Lentz AC. Update on Intraoperative Cultures, Biofilms, and Modifiable Factors During Revision of Clinically Non-Infected Penile Implants. Sex Med Rev 2021;9:160-168.

Promising Therapeutic Strategies Against Microbial Biofilm Challenges

Biofilms are communities of microorganisms that are attached to a biological or abiotic surface and are surrounded by a self-produced extracellular matrix. Cells within a biofilm have intrinsic characteristics that are different from those of planktonic cells. Biofilm resistance to antimicrobial agents has drawn increasing attention. It is well-known that medical device- and tissue-associated biofilms may be the leading cause for the failure of antibiotic treatments and can cause many chronic infections. The eradication of biofilms is very challenging. Many researchers are working to address biofilm-related infections, and some novel strategies have been developed and identified as being effective and promising. Nevertheless, more preclinical studies and well-designed multicenter clinical trials are critically needed to evaluate the prospects of these strategies. Here, we review information about the mechanisms underlying the drug resistance of biofilms and discuss recent progress in alternative therapies and promising strategies against microbial biofilms. We also summarize the strengths and weaknesses of these strategies in detail.

Maltotriose-based probes for fluorescence and photoacoustic imaging of bacterial infections

Currently, there are no non-invasive tools to accurately diagnose wound and surgical site infections before they become systemic or cause significant anatomical damage. Fluorescence and photoacoustic imaging are cost-effective imaging modalities that can be used to noninvasively diagnose bacterial infections when paired with a molecularly targeted infection imaging agent. Here, we develop a fluorescent derivative of maltotriose (Cy7-1-maltotriose), which is shown to be taken up in a variety of gram-positive and gram-negative bacterial strains in vitro. In vivo fluorescence and photoacoustic imaging studies highlight the ability of this probe to detect infection, assess infection burden, and visualize the effectiveness of antibiotic treatment in E. coli-induced myositis and a clinically relevant S. aureus wound infection murine model. In addition, we show that maltotriose is an ideal scaffold for infection imaging agents encompassing better pharmacokinetic properties and in vivo stability than other maltodextrins (e.g. maltohexose).

Prevalence of methicillin-resistant <em>Staphylococcus aureus</em> and other pathogens in pus samples of orthopedic department at a tertiary care hospital in Pakistan

BACKGROUND Orthopedic infections are difficult to manage. Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most dangerous and harmful bacteria and is difficult to eradicate because of its changing strains as well as sensitivity to different antibiotics. The main aim of this study was to determine the prevalence of pathogens, especially MRSA, associated with orthopedic wounds and their sensitivity to different antibiotics. METHODS A prospective study was conducted from September 2015 to August 2016. Pus samples of 1,350 patients who presented at the out-patient department or admitted with a wound infection after an orthopedic intervention were taken with the help of culture swab and were sent for culture and sensitivity according to hospital protocol. Data analyses were made using the SPSS software, version 17 (IBM). RESULTS Adults aged between 15 and 30 years were most affected, with 444 (32.9%) cases. Of the patients, 268 (19.9%) had negative cultures. Among the patients with positive cultures, the gram-positive cocci and gram-negative rods were 497 (36.8%) and 377 (27.9%), respectively. The most common pathogen was MRSA (240; 17.8%), followed by Escherichia coli and methicillin-sensitive S. aureus. CONCLUSIONS Multiple pathogens are involved in patients having an orthopedic surgical intervention. The high occurrence of MRSA and E. coli has an increasing economic burden on patients because of these pathogens high resistance to antibiotics. Thus, proper preventive measures should be done to decrease the occurrence of such infections as well as their associated morbidity.

The enhanced photocatalytic properties of MnO2/g-C3N4 heterostructure for rapid sterilization under visible light

Herein, a heterostructure based on MnO₂ and g-C₃N₄ was constructed on the surface of metallic Ti implants, in which MnO₂ favored the transfer and separation of free charges to enhance the photoconversion efficiency of g-C₃N₄ by 21.11%. Consequently, the yield of ROS was promoted significantly, which denatured protein and damaged DNA to kill bacteria efficiently. In addition, glutathione (GSH, l-γ-glutamyl-l-cysteinyl-glycine) defending oxidative stress in bacteria, was oxidized by MnO₂ in the hybrid coating once the bacterial membrane was disrupted by ROS. Hence, after visible light irradiation for 20 min, MnO₂/g-C₃N₄ coating exhibited superior disinfection efficacy of 99.96% and 99.26% against S. aureus and E. coli severally. This work provided a practical sterilization strategy about MnO₂/g-C₃N₄ systems through the synergistic effects of enhanced photodynamic antibacterial therapy and oxidization effect of MnO₂ with great biosafety, in which MnO₂ enhanced the photocatalyst property of g-C₃N₄ to generate more ROS and deplete GSH to improve antibacterial efficiency. It will bring more insight into rapid and highly effective disinfection and antibacterial strategy without using traditional high-temperature, ultraviolet ray and antibiotics that cause side-effects.

Implant infections: adhesion, biofilm formation and immune evasion

Medical device-associated infections account for a large proportion of hospital-acquired infections. A variety of opportunistic pathogens can cause implant infections, depending on the type of the implant and on the anatomical site of implantation. The success of these versatile pathogens depends on rapid adhesion to virtually all biomaterial surfaces and survival in the hostile host environment. Biofilm formation on implant surfaces shelters the bacteria and encourages persistence of infection. Furthermore, implant-infecting bacteria can elude innate and adaptive host defences as well as biocides and antibiotic chemotherapies. In this Review, we explore the fundamental pathogenic mechanisms underlying implant infections, highlighting orthopaedic implants and Staphylococcus aureus as a prime example, and discuss innovative targets for preventive and therapeutic strategies.

Usefulness of Culturing the Periprosthetic Membrane or Neosynovium for the Diagnosis of Infection During Hip and Knee Revision Arthroplasty

INTRODUCTION

Identification of microorganisms is critical for correct management of an infected arthroplasty. Our hypothesis is that the culture yield depends on the location around the prosthesis from which samples are obtained.

METHODS

This prospective study included 298 revisions of the hip (123) and knee (175). We compared the yield of the intraoperative samples obtained, which included synovial fluid (two), neosynovium (two), and periprosthetic membrane (two).

RESULTS

Cultures were positive in 28 cases, in which 15 had the same diagnosis considering either the neosynovium or the membrane, and there were 3 cases in which the infection could have been diagnosed only by considering the combination of both. In all, there were 8 cases in which the infection might have been misdiagnosed unless considering a combination of both solid tissue samples (P = 0.004).

CONCLUSIONS

The yields of the periprosthetic membrane and neosynovium do not differ significantly, and we recommend considering a combination of both.

LEVEL OF EVIDENCE

Diagnostic Level II.

Preferential Colonization of Osteoblasts Over Co-cultured Bacteria on a Bifunctional Biomaterial Surface

Implant-related infection is a devastating complication in clinical trauma and orthopedics. The aim of this study is to use a bifunctional biomaterial surface in order to investigate the competitive colonization between osteoblasts and bacteria, which is the cause of implant-related infection. A bone-engineering material capable of simultaneously facilitating osteoblast adhesion and inhibiting the growth of Staphylococcus aureus (S. aureus) was prepared. Then, three different co-cultured systems were developed in order to investigate the competitive colonization between the two cohorts on the surface. The results suggested that while the pre-culturing of either cohort compromised the subsequent adhesion of the other according to the ‘race for the surface’ theory, the synergistic effect of preferential cell adhesion and antibacterial activity of the bifunctional surface led to the predominant colonization and survival of osteoblasts, effectively inhibiting the bacterial adhesion and biofilm formation of S. aureus in the co-culture systems with both cohorts. This research offers new insight into the investigation of competitive surface-colonization between osteoblasts and bacteria for implant-related infection.

The Bioactivity and Photocatalytic Properties of Titania Nanotube Coatings Produced with the Use of the Low-Potential Anodization of Ti6Al4V Alloy Surface

Titania nanotube (TNT) coatings were produced using low-potential anodic oxidation of Ti6Al4V substrates in the potential range 3-20 V. They were analysed by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The wettability was estimated by measuring the contact angle when applying water droplets. The bioactivity of the TNT coatings was established on the basis of the biointegration assay (L929 murine fibroblasts adhesion and proliferation) and antibacterial tests against Staphylococcus aureus (ATCC 29213). The photocatalytic efficiency of the TNT films was studied by the degradation of methylene blue under UV irradiation. Among the studied coatings, the TiO₂ nanotubes obtained with the use of 5 V potential (TNT5) were found to be the most appropriate for medical applications. The TNT5 sample possessed antibiofilm properties without enriching it by additional antimicrobial agent. Furthermore, it was characterized by optimal biocompatibility, performing better than pure Ti6Al4V alloy. Moreover, the same sample was the most photocatalytically active and exhibited the potential for the sterilization of implants with the use of UV light and for other environmental applications.

Evaluation of bacterial adherence of clinical isolates of Staphylococcus sp. using a competitive model: An in vitro approach to the "race for the surface" theory

Objectives

Implant-related infection is one of the most devastating complications in orthopaedic surgery. Many surface and/or material modifications have been developed in order to minimise this problem; however, most of the in vitro studies did not evaluate bacterial adhesion in the presence of eukaryotic cells, as stated by the ‘race for the surface’ theory. Moreover, the adherence of numerous clinical strains with different initial concentrations has not been studied.

Methods

We describe a method for the study of bacterial adherence in the presence of preosteoblastic cells. For this purpose we mixed different concentrations of bacterial cells from collection and clinical strains of staphylococci isolated from implant-related infections with preosteoblastic cells, and analysed the minimal concentration of bacteria able to colonise the surface of the material with image analysis.

Results

Our results show that clinical strains adhere to the material surface at lower concentrations than collection strains. A destructive effect of bacteria on preosteoblastic cells was also detected, especially with higher concentrations of bacteria.

Conclusions

The method described herein can be used to evaluate the effect of surface modifications on bacterial adherence more accurately than conventional monoculture studies. Clinical strains behave differently than collection strains with respect to bacterial adherence.

Cite this article: M. Martinez-Perez, C. Perez-Jorge, D. Lozano, S. Portal-Nuñez, R. Perez-Tanoira, A. Conde, M. A. Arenas, J. M. Hernandez-Lopez, J. J. de Damborenea, E. Gomez-Barrena, P. Esbrit, J. Esteban. Evaluation of bacterial adherence of clinical isolates of Staphylococcus sp. using a competitive model: An in vitro approach to the “race for the surface” theory. Bone Joint Res 2017;6:315–322. DOI: 10.1302/2046-3758.65.BJR-2016-0226.R2.

Microbiological diagnosis of device-related biofilm infections

Medical device-related infections cause undue patient distress, increased morbidity and mortality and pose a huge financial burden on healthcare services. The pathogens are frequently distributed heterogeneously in biofilms, which can persist without being effectively cleared by host immune defenses and antibiotic therapy. At present, there is no 'gold standard' available to reveal the presence of device-related biofilm infections. However, adequate sample collection and logistics, standardised diagnostic methods, and interpretation of results by experienced personnel are important steps in efficient diagnosis and treatment of these infections. The focus of this mini review is on prosthethic joint and cardiovascular implantable device infections, which exemplify permanent devices that are placed in a sterile body site. These device-related infections represent some of the most challenging in terms of both diagnosis and treatment.

Photoantimicrobials-are we afraid of the light?

Although conventional antimicrobial drugs have been viewed as miraculous cure-alls for the past 80 years, increasing antimicrobial drug resistance requires a major and rapid intervention. However, the development of novel but still conventional systemic antimicrobial agents, having only a single mode or site of action, will not alleviate the situation because it is probably only a matter of time until any such agents will also become ineffective. To continue to produce new agents based on this notion is unacceptable, and there is an increasing need for alternative approaches to the problem. By contrast, light-activated molecules called photoantimicrobials act locally via the in-situ production of highly reactive oxygen species, which simultaneously attack various biomolecular sites in the pathogenic target and therefore offer both multiple and variable sites of action. This non-specificity at the target circumvents conventional mechanisms of resistance and inhibits the development of resistance to the agents themselves. Photoantimicrobial therapy is safe and easy to implement and, unlike conventional agents, the activity spectrum of photoantimicrobials covers bacteria, fungi, viruses, and protozoa. However, clinical trials of these new, truly broad-spectrum, and minimally toxic agents have been few, and the funding for research and development is almost non-existent. Photoantimicrobials constitute one of the few ways forward through the morass of drug-resistant infectious disease and should be fully explored. In this Personal View, we raise awareness of the novel photoantimicrobial technologies that offer a viable alternative to conventional drugs in many relevant application fields, and could thus slow the pace of resistance development.

The role of biofilm on orthopaedic implants: the "Holy Grail" of post-traumatic infection management?

The development of post-traumatic infection is potentially a limb threatening condition. The orthopaedic trauma literature lags behind the research performed by our arthroplasty colleagues on the topic of implant-related infections. Surgical site infections in the setting of a recent ORIF are notoriously hard to eradicate due to biofilm formation around the implant. This bacteria-friendly, dynamic, living pluri-organism structure has the ability to morph and adapt to virtually any environment with the aim to maintain the causative organism alive. The challenges are twofold: establishing an accurate diagnosis with speciation/sensitivity and eradicating the infection. Multiple strategies have been researched to improve diagnostic accuracy, to prevent biofilm formation on orthopaedic implants, to mobilize/detach or weaken the biofilm or to target specifically bacteria embedded in the biofilm. The purpose of our paper is to review the patho-physiology of this mysterious pluri-cellular structure and to summarize some of the most pertinent research performed to improve diagnostic and treatment strategies in biofilm-related infections.

Orthopaedic device-related infection: current and future interventions for improved prevention and treatment

Orthopaedic and trauma device-related infection (ODRI) remains one of the major complications in modern trauma and orthopaedic surgery.Despite best practice in medical and surgical management, neither prophylaxis nor treatment of ODRI is effective in all cases, leading to infections that negatively impact clinical outcome and significantly increase healthcare expenditure.The following review summarises the microbiological profile of modern ODRI, the impact antibiotic resistance has on treatment outcomes, and some of the principles and weaknesses of the current systemic and local antibiotic delivery strategies.The emerging novel strategies aimed at preventing or treating ODRI will be reviewed. Particular attention will be paid to the potential for clinical impact in the coming decades, when such interventions are likely to be critically important.The review focuses on this problem from an interdisciplinary perspective, including basic science innovations and best practice in infectious disease. Cite this article: Moriarty TF, Kuehl R, Coenye T, et al. Orthopaedic device related infection: current and future interventions for improved prevention and treatment. EFORT Open Rev 2016;1:89-99. DOI: 10.1302/2058-5241.1.000037.

The management of periprosthetic infections in the future: a review of new forms of treatment

The number of arthroplasties being undertaken is expected to grow year on year, and periprosthetic joint infections will be an increasing socioeconomic burden. The challenge to prevent and eradicate these infections has resulted in the emergence of several new strategies, which are discussed in this review. Cite this article: Bone Joint J 2015;97-B:1162-9.

Microbial diagnosis of infection and colonization of cardiac implantable electronic devices by use of sonication

OBJECTIVES

The clinical utility of sonication as an adjunctive diagnostic tool for the microbial diagnosis of cardiac implantable device-associated infections (CIDAIs) was investigated.

METHODS

The implants of 83 subjects were investigated, 15 with a CIDAI and 68 without a clinical infection. Clinical data were analyzed prospectively and sonication fluid cultures (83 patients, 100%) and traditional cultures (31 patients, 37.4%) were performed

RESULTS

Generator pocket infection and device-related endocarditis were found in 13 (86.7%) and four (26.7%) subjects, respectively. The mean numbers of previous technical complications and infections were higher in the infected patients compared to the non-infected patients (8 vs. 1, p<0.001; 2 vs. 0, p<0.031, respectively). The sensitivity and specificity for detecting CIDAI was 73.3% (11/15) and 48.5% (33/68) for sonication fluid culture, and 26.7% (4/15) and 100% (16/16) for traditional culture (p<0.001), respectively. A higher number of organisms were identified by sonication fluid than by tissue culture (58 vs. 4 specimens; p<0.001). The most frequent organisms cultured were Gram-positive cocci (66.1%), mainly coagulase-negative staphylococci (35.5%). Thirty-five (51.5%) non-infected subjects were considered colonized due to the positive identification of organisms exclusively through sonication fluid culture.

CONCLUSIONS

Sonication fluid culture from the removed cardiac implants has the potential to improve the microbiological diagnosis of CIDAIs.

Photodynamic Antimicrobial Chemotherapy (PACT) in osteomyelitis induced by Staphylococcus aureus: Microbiological and histological study

Osteomyelitis is an inflammation either of medullar spaces or of the surface of cortical bones, which represents a bacterial infection. Photodynamic Antimicrobial Chemotherapy (PACT) is a treatment based on a cytotoxic photochemical reaction that induces a series of metabolic reactions and culminates in bacterial suppression. Such effect led to the idea that it could be used as a treatment of osteomyelitis. Following approval by the Animal Experimentation Committee of the School of Dentistry of the Federal University of Bahia, the present randomized study used eighty Wistar rats with the aim to evaluate, by microbiological and histological analysis, the effects of Photodynamic Antimicrobial Chemotherapy - PACT on tibial surgical bone defects in rats infected by Staphylococcus aureus. The animals were divided in groups: Control (non-infected); Control Osteomyelitis Induction; Saline solution; Photosensitizer; Red Laser and PACT - on this group, a diode laser (40mW; λ660nm ∅=0.04cm(2), CW, 10J/cm(2)) was used in combination with 5μg/ml of toluidine blue as the photosensitizer. On the microbiological study, immediately after treatment, the PACT group presented a bacterial reduction of 97.4% (p<0.001). Thirty days after treatment, there was a bacterial reduction of more than 99.9% (p<0.001). In the histological study, it was observed that the PACT group demonstrated an intense presence of osteocytes and absence of bone sequestration and micro-abscesses. The PACT using toluidine blue was effective in reducing the number of S. aureus enabling a better quality bone repair.

In vitro antibiofilm activity of bioactive glass S53P4

AIM

This work aimed to investigate the ability of different formulations of bioactive glass (BAG)-S53P4 to interfere with bacterial biofilm produced on prosthetic material by methicillin-resistant Staphylococcus aureus and multi-drug-resistant Pseudomonas aeruginosa.

MATERIALS & METHODS

Antibiofilm activity of three formulations of bioglass was assessed at different time points through two different analyses: Crystal Violet and confocal laser scanning microscopy assays.

RESULTS

Significant differences in the whole biofilm were observed between BAG-S53P4-treated and control samples, while no marked changes in antibiofilm activity were observed among the tested formulations. Data from colorimetric assay were confirmed by confocal laser scanning microscopy analysis, which evidenced the significant reduction in biomass and a decrease of total cell volume when both S. aureus and P. aeruginosa biofilms were treated with BAG-S53P4.

CONCLUSION

BAG-S53P4 can be considered as an excellent adjuvant in the treatment of prosthetic infections related to biofilm.

The role of microbial biofilms in prosthetic joint infections

Prosthetic joint infection (PJI) still remains a significant problem. In line with the forecasted rise in joint replacement procedures, the number of cases of PJI is also anticipated to rise. The formation of biofilm by causative pathogens is central to the occurrence and the recalcitrance of PJI. The subject of microbial biofilms is receiving increasing attention, probably as a result of the wide acknowledgement of the ubiquity of biofilms in the natural, industrial, and clinical contexts, as well as the notorious difficulty in eradicating them. In this review, we discuss the pertinent issues surrounding PJI and the challenges posed by biofilms regarding diagnosis and treatment. In addition, we discuss novel strategies of prevention and treatment of biofilm-related PJI.

Antimicrobial photodynamic activity of hypericin against methicillin-susceptible and resistant Staphylococcus aureus biofilms

ABSTRACT 

Aim: To evaluate the effectiveness of the photodynamic therapy using hypericin (HYP) against both planktonic and biofilm-forming Staphylococcus aureus. Materials & methods: HYP photoactivity was evaluated against methicillin-susceptible and resistant S. aureus. Bacterial suspension or biofilm were preincubated with HYP and subjected to LED illumination. Viable bacteria were determined by colony counting. Results: Preincubation with HYP (5 min) plus light exposure (10 min) showed bactericidal effect against planktonic methicillin-susceptible S. aureus and methicillin-resistant S. aureus. Longer preincubation times (24 h) and time light exposure (30 min) were required to reach HYP-photoactivity against S. aureus biofilms. HYP-photoactivity was correlated to the biofilm production. Conclusion: HYP could be a potential photosensitizer for the inactivation of staphylococcal biofilms forming on the surfaces accessible to visible light.

Biofilm-based implant infections in orthopaedics

The demand for joint replacement surgery is continuously increasing with rising costs for hospitals and healthcare systems. Staphylococci are the most prevalent etiological agents of orthopedic infections. After an initial adhesin-mediated implant colonization, Staphylococcus aureus and Staphylococcus epidermidis produce biofilm. Biofilm formation proceeds as a four-step process: (1) initial attachment of bacterial cells; (2) cell aggregation and accumulation in multiple cell layers; (3) biofilm maturation and (4) detachment of cells from the biofilm into a planktonic state to initiate a new cycle of biofilm formation elsewhere. The encasing of bacteria in biofilms gives rise to insuperable difficulties not only in the treatment of the infection, but also in assessing the state and the nature of the infection using traditional cultural methods. Therefore, DNA-based molecular methods have been developed to provide rapid identification of all microbial pathogens. To combat biofilm-centered implant infections, new strategies are being developed, among which anti-infective or infective-resistant materials are at the forefront. Infection-resistant materials can be based on different approaches: (i) modifying the biomaterial surface to give anti-adhesive properties, (ii) doping the material with antimicrobial substances, (iii) combining anti-adhesive and antimicrobial effects in the same coating, (iv) designing materials able to oppose biofilm formation and support bone repair.

Evaluation of implant sonication as a diagnostic tool in implant-associated infections

Infections of implants pose a severe problem in the field of orthopedic surgery, because they can cause bone degradation with subsequent loosening of the implant. The discrimination between septic implant loosening and aseptic loosening can be a challenge, and hence novel diagnostic methods have been introduced to improve the detection of bacteria. Because a major problem is their firm adherence to implants due to biofilm formation, sonication has been introduced, followed by identification of bacteria by culture or genetic methods. In this study, we compared the results obtained after sonication pretreatment with those of microbiological testing of tissue samples and histopathological evaluation of the same tissue. Furthermore, we related the results obtained following sonication to the clinical diagnosis of septic or aseptic implant loosening, respectively. Sonication of explanted devices also enhances the likelihood of detecting bacterial growth in patients who were considered "aseptic" based on the clinical evaluation.

Risk factors for failure in early prosthetic joint infection treated with debridement. Influence of etiology and antibiotic treatment

PURPOSES

The aim of the present study was to evaluate the importance of isolated microorganisms according to the Gram stain and the type of antibiotic received on the outcome of early prosthetic joint infection (PJI) treated with debridement, antibiotics and implant retention (DAIR).

METHODS

From January 1999 to December 2009, all patients with an early PJI were prospectively registered in a database and they were retrospectively reviewed for this study.

RESULTS

During the study period, 160 patients met the inclusion criteria of the study. After a mean (SD) post-debridement follow-up of 5.2 (2.5) years, 117 patients (73.1%) were considered to be in remission and 43 (26.9%) were classified as failure. Variables associated with failure were liver cirrhosis (66.7% vs. 22.8%, p=0.001), diagnosis within the first 30 days from arthroplasty (30.4% vs. 8.0%, p=0.020), C-reactive protein (CRP) >12 mg/dl (46.7% vs. 21.2%, p=0.005), microorganism isolated in all deep samples (31.1% vs. 16.0%, p=0.047) and Gram-negative (GN) infection not treated with a fluoroquinolone (57.1% vs. 20.0%, P=0.004). Gram-positive (GP) infection not treated with rifampin was close to be statistically significantly associated with failure (34.4% vs. 19.2%, p=0.067). A multivariate analysis identified liver cirrhosis (OR: 12.4 CI95%: 3.1-49.7, p<0.001), CRP-value (OR: 1.06 CI95%: 1.0-1.11, p=0.049), and when a GN-infection was not treated with a fluoroquinolone (OR: 6.5, CI95%: 1.8-23.8, p=0.005) as independent predictors of failure.

CONCLUSION

The remission rate of PJI treated with DAIR after 3 years of follow-up was 73%. The main predictors of failure were liver cirrhosis, the selected antibiotic most specially fluoroquinolones for GN and rifampin for GP infections, the C-reactive protein and the number of samples culture positive as a potential surrogate markers of bacterial density.

Biofilm formation on titanium implants counteracted by grafting gallium and silver ions

Biofilm-associated infections remain the leading cause of implant failure. Thanks to its established biocompatibility and biomechanical properties, titanium has become one of the most widely used materials for bone implants. Engineered surface modifications of titanium able to thwart biofilm formation while endowing a safe anchorage to eukaryotic cells are being progressively developed. Here surfaces of disks of commercial grade 2 titanium for bone implant were grafted with gallium and silver ions by anodic spark deposition. Scanning electron microscopy of the surface morphology and energy dispersive X-ray spectroscopy were used for characterization. Gallium-grafted titanium was evaluated in comparison with silver-grafted titanium for both in vivo and in vitro antibiofilm properties and for in vitro compatibility with human primary gingival fibroblasts. Surface-modified materials showed: (i) homogeneous porous morphology, with pores of micrometric size; (ii) absence of cytotoxic effects; (iii) ability to support in vitro the adhesion and spreading of gingival fibroblasts; and (iv) antibiofilm properties. Although both silver and gallium exhibited in vitro strong antibacterial properties, in vivo gallium was significantly more effective than silver in reducing number and viability of biofilm bacteria colonies. Gallium-based treatments represent promising titanium antibiofilm coatings to develop new bone implantable devices for oral, maxillofacial, and orthopedic applications.

Lavage with allicin in combination with vancomycin inhibits biofilm formation by Staphylococcus epidermidis in a rabbit model of prosthetic joint infection

BACKGROUND AND AIM

The present anti-infection strategy for prosthetic joint infections (PJI) includes the use of antibiotics and surgical treatments, but the bacterial eradication rates are still low. One of the major challenges is the formation of biofilm causing poor bacterial eradication. Recently it has been reported that allicin (diallyl thiosulphinate), an antibacterial principle of garlic, can inhibit bacteria adherence and prevent biofilm formation in vitro. However, whether allicin could inhibit biofilm formation in vivo is unknown. The aim of this study was to investigate the effects of allicin on biofilm formation, and whether allicin could potentiate the bactericidal effect of vancomycin in a rabbit PJI model.

METHODS

A sterile stainless-steel screw with a sterile ultra-high molecular weight polyethylene washer was inserted into the lateral femoral condyle of the right hind knee joint of rabbit, and 1 mL inoculum containing 104 colony-forming units of Staphylococcus epidermidis was inoculated into the knee joint (n = 32). Fourteen days later, rabbits randomly received one of the following 4 treatments using continuous lavages: normal saline, vancomycin (20 mcg/mL), allicin (4 mg/L), or allicin (4 mg/L) plus vancomycin (20 mcg/mL). Three days later, the washer surface biofilm formation was examined by scanning electron microscopy (SEM). The bacterial counts within the biofilm of implanted screws were determined by bacterial culture.

RESULTS

The lowest number of viable bacterial counts of Staphylococcus epidermidis recovered from the biofilm was in the rabbits treated with allicin plus vancomycin (P<0.01 vs. all other groups). The biofilm formation was significantly reduced or undetectable by SEM in rabbits receiving allicin or allicin plus vancomycin.

CONCLUSION

Intra-articular allicincan inhibit biofilm formation and enhance the bactericidal effect of vancomycin on implant surface in vivo. Allicin in combination with vancomycin may be a useful anti-infection strategy for the treatment of PJI.

The interaction of bacteria with engineered nanostructured polymeric materials: a review

Bacterial infections are a leading cause of morbidity and mortality worldwide. In spite of great advances in biomaterials research and development, a significant proportion of medical devices undergo bacterial colonization and become the target of an implant-related infection. We present a review of the two major classes of antibacterial nanostructured materials: polymeric nanocomposites and surface-engineered materials. The paper describes antibacterial effects due to the induced material properties, along with the principles of bacterial adhesion and the biofilm formation process. Methods for antimicrobial modifications of polymers using a nanocomposite approach as well as surface modification procedures are surveyed and discussed, followed by a concise examination of techniques used in estimating bacteria/material interactions. Finally, we present an outline of future sceneries and perspectives on antibacterial applications of nanostructured materials to resist or counteract implant infections.

The expanding horizon of prosthetic joint infections

Prosthetic joint infection (PJI) is a serious and potentially devastating complication of arthroplasty. Prior arthroplasty, immunosuppression, severe comorbid conditions, and prolonged surgical duration are important risk factors for PJI. More than half of the cases of PJI are caused by Staphylococcus aureus and coagulase-negative staphylococci. The biofilm plays a central role in its pathogenesis. The diagnosis of PJI requires the presence of purulence, sinus tract, evidence of inflammation on histopathology, or positive microbiologic cultures. The use of diagnostic imaging techniques is generally limited but may be helpful in selected cases. The most effective way to prevent PJI is to optimize the health of patients, using antibiotic prophylaxis in a proper and timely fashion. Management of PJI frequently requires removal of all hardware and administration of intravenous antibiotics. This review summarizes and analyzes the results of previous reports of PJI and assesses the prevention and management of this important entity.

Cytocompatibility and antibacterial properties of capping materials

The aim of this study was to evaluate and compare the antimicrobial activity and cytocompatibility of six different pulp-capping materials: Dycal (Dentsply), Calcicur (Voco), Calcimol LC (Voco), TheraCal LC (Bisco), MTA Angelus (Angelus), and Biodentine (Septodont). To evaluate antimicrobial activity, materials were challenged in vitro with Streptococcus mutans, Streptococcus salivarius, and Streptococcus sanguis in the agar disc diffusion test. Cytocompatibility of the assayed materials towards rat MDPC-23 cells was evaluated at different times by both MTT and apoptosis assays. Results significantly differed among the different materials tested. Both bacterial growth inhibition halos and cytocompatibility performances were significantly different among materials with different composition. MTA-based products showed lower cytotoxicity and valuable antibacterial activity, different from calcium hydroxide-based materials, which exhibited not only higher antibacterial activity but also higher cytotoxicity.

pH-mediated potentiation of aminoglycosides kills bacterial persisters and eradicates in vivo biofilms

BACKGROUND

Limitations in treatment of biofilm-associated bacterial infections are often due to subpopulation of persistent bacteria (persisters) tolerant to high concentrations of antibiotics. Based on the increased aminoglycoside efficiency under alkaline conditions, we studied the combination of gentamicin and the clinically compatible basic amino acid L-arginine against planktonic and biofilm bacteria both in vitro and in vivo.

METHODS

Using Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli bioluminescent strains, we studied the combination of L-arginine and gentamicin against planktonic persisters through time-kill curves of late stationary-phase cultures. In vitro biofilm tolerance towards gentamicin was assessed using PVC 96 well-plates assays. Efficacy of gentamicin as antibiotic lock treatment (ALT) at 5 mg/mL at different pH was evaluated in vivo using a model of totally implantable venous access port (TIVAP) surgically implanted in rats.

RESULTS

We demonstrated that a combination of gentamicin and the clinically compatible basic amino acid L-arginine increases in vitro planktonic and biofilm susceptibility to gentamicin, with 99% mortality amongst clinically relevant pathogens, i.e. S. aureus, E. coli and P. aeruginosa persistent bacteria. Moreover, although gentamicin local treatment alone showed poor efficacy in a clinically relevant in vivo model of catheter-related infection, gentamicin supplemented with L-arginine led to complete, long-lasting eradication of S. aureus and E. coli biofilms, when used locally.

CONCLUSION

Given that intravenous administration of L-arginine to human patients is well tolerated, combined use of aminoglycoside and the non-toxic adjuvant L-arginine as catheter lock solution could constitute a new option for the eradication of pathogenic biofilms.

Comparison of bacterial results from conventional cultures of the periprosthetic membrane and the synovial or pseudocapsule during hip revision arthroplasty

INTRODUCTION

Bacterial identification is essential to diagnose and treat a revision for prosthetic loosening of an infected hip. The purpose of this study was to determine whether conventional cultures from the periprosthetic membrane are superior to synovial/pseudocapsule samples in the diagnosis of infection in hip revision arthroplasty.

MATERIALS AND METHODS

We performed a prospective study including all hip revisions from October 2009 to October of 2011. Once the implants were removed and prior to the administration of the antibiotic prophylaxis, six periprosthetic samples from different sites were sent to the laboratory for culturing: two periprosthetic fluid samples, two solid material (synovial/pseudocapsule) samples and two swabs. Once the six samples were taken, antibiotic prophylaxis was administered and just as the implant was removed, two more solid samples of the periprosthetic membrane were obtained.

RESULTS

Of a total of 86 hip revision surgeries, 22 were considered septic revisions postoperatively, of which 16 resulted in positive cultures. Of these 16 revisions, 14 obtained the same microbiologic diagnostic when considering either the synovial/pseudocapsule culture results or the solid membrane sample.

CONCLUSIONS

We conclude that the membrane sample for a conventional culture is not superior to the synovial/pseudocapsule sample in detecting microorganisms.

Conventional and molecular diagnostic strategies for prosthetic joint infections

An accurate diagnosis of prosthetic joint infection (PJI) is the mainstay for an optimized clinical management. This review analyzes different diagnostic strategies of PJI, with special emphasis on molecular diagnostic tools and their current and future applications. Until now, the culture of periprosthetic tissues has been considered the gold standard for the diagnosis of PJI. However, sonication of the implant increases the sensitivity of those cultures and is being increasingly adopted by many centers. Molecular diagnostic methods compared with intraoperative tissue culture, especially if combined with sonication, have a higher sensitivity, a faster turnaround time and are not influenced by previous antimicrobial therapy. However, they still lack a system for detection of antimicrobial susceptibility, which is crucial for an optimized and less toxic therapy of PJI. More studies are needed to assess the clinical value of these methods and their cost-effectiveness.

The role of extracellular DNA in the establishment, maintenance and perpetuation of bacterial biofilms

The significance of extracellular DNA (eDNA) in biofilms was overlooked until researchers added DNAse to a Pseudomonas aeruginosa biofilm and watched the biofilm disappear. Now, a decade later, the widespread importance of eDNA in biofilm formation is undisputed, but detailed knowledge about how it promotes biofilm formation and conveys antimicrobial resistance is only just starting to emerge. In this review, we discuss how eDNA is produced, how it aids bacterial adhesion, secures the structural stability of biofilms and contributes to antimicrobial resistance. The appearance of eDNA in biofilms is no accident: It is produced by active secretion or controlled cell lysis - sometimes linked to competence development. eDNA adsorbs to and extends from the cell surface, promoting adhesion to abiotic surfaces through acid-base interactions. In the biofilm, is it less clear how eDNA interacts with cells and matrix components. A few eDNA-binding biomolecules have been identified, revealing new concepts in biofilm formation. Being anionic, eDNA chelates cations and restricts diffusion of cationic antimicrobials. Furthermore, chelation of Mg(2+) triggers a genetic response that further increases resistance. The multifaceted role of eDNA makes it an attractive target to sensitize biofilms to conventional antimicrobial treatment or development of new strategies to combat biofilms.

Antibiofilm agents and implant-related infections in orthopaedics: where are we?

Orthopaedics is currently the largest market of biomaterials worldwide and implant-related infections, although relatively rare, remain among the first reasons for joint arthroplasty and osteosynthesis failure. Bacteria start implant infection by adhering to biomaterials and producing biofilms, which represent a major reason for bacterial persistence, in spite of antibiotic treatment and host's defence. In the last two decades, a number of different antibiofilm agents have been studied and both in vitro and in vivo results appear now promising, even if their effective role in orthopaedics remains to be assessed. In this review, we introduce an original classification of antibiofilm agents, based on their mechanism of action and examine the available data concerning their possible application to orthopaedic implant-related infections. Molecules that interfere with biofilm production (biofilm prevention agents) include anti-adhesion compounds, quorum sensing inhibitors, non-steroideal anti-inflammatory drugs, and antimicrobial peptides; N-acetylcysteine and specific enzymes promise the greatest therapeutic possibilities by disrupting established biofilms (biofilm disrupting agents). The identification of antimicrobials able to bypass the biofilm barrier (biofilm bypassing agents), and antibiofilm vaccines are further strategies aimed to reduce the impact of biofilm-related infections, opening new pathways in controlling implant-related infections. However, this review shows that still insufficient knowledge is currently available as to regard the efficacy and safety of the investigated antibiofilm strategies to treat infection that involve bone tissue and biomaterials commonly implanted in orthopaedics, pointing out the need for further research in this promising field.