Antibiotic-loaded phosphatidylcholine inhibits staphylococcal bone infection

Current Progress and Future Perspectives in Contact and Releasing-Type Antimicrobial Coatings of Orthopaedic Implants: A Systematic Review Analysis Emanated from In Vitro and In Vivo Models

Background: Despite the expanding use of orthopedic devices and the application of strict pre- and postoperative protocols, the elimination of postoperative implant-related infections remains a challenge. Objectives: To identify and assess the in vitro and in vivo properties of antimicrobial-, silver- and iodine-based implants, as well as to present novel approaches to surface modifications of orthopedic implants. Methods: A systematic computer-based review on the development of these implants, on PubMed and Web of Science databases, was carried out according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Results: Overall, 31 in vitro and 40 in vivo entries were evaluated. Regarding the in vitro studies, antimicrobial-based coatings were assessed in 12 entries, silver-based coatings in 10, iodine-based in 1, and novel-applied coating technologies in 8 entries. Regarding the in vivo studies, antimicrobial coatings were evaluated in 23 entries, silver-coated implants in 12, and iodine-coated in 1 entry, respectively. The application of novel coatings was studied in the rest of the cases (4). Antimicrobial efficacy was examined using different bacterial strains, and osseointegration ability and biocompatibility were examined in eukaryotic cells and different animal models, including rats, rabbits, and sheep. Conclusions: Assessment of both in vivo and in vitro studies revealed a wide antimicrobial spectrum of the coated implants, related to reduced bacterial growth, inhibition of biofilm formation, and unaffected or enhanced osseointegration, emphasizing the importance of the application of surface modification techniques as an alternative for the treatment of orthopedic implant infections in the clinical settings.

The efficacy of antibiotic-eluting material in a two-stage model of periprosthetic joint infection

Periprosthetic joint infections occur in about 2% of patients who undergo primary total joint arthroplasty, a procedure performed over 1 million times in the United States. The gold standard of treatment is a two-stage revision. This study aimed to establish a two-stage procedure in a preclinical small animal model (rat) to test and compare the efficacy of an antibiotic-eluting material in managing infection. Joint replacement was simulated by transchondylarly implanting a polyethylene (PE) plug into the distal femur and a titanium screw in the proximal tibia. Methicillin-sensitive Staphylococcus aureus (MSSA) 108  CFU/mL was injected into the tibial canal and the joint space before wound closure. The control groups were killed on postoperative day (POD) 18 (n = 12) and on POD 42 (n = 4) to assess both early and later-stage outcomes in the control group. The test group underwent revision surgery on POD 18 for treatment using gentamicin-eluting polyethylene (GPE, n = 4) and was observed until POD 42 to evaluate the efficacy of treatment. Our results showed that the bone loss for the treatment group receiving GPE was significantly less than that of the control (p < 0.05), which was supported by the histology images and an AI-tool assisted infection rate evaluation. Gait metrics duty factor imbalance and hindlimb temporal symmetry were significantly different between the treatment and control groups on Day 42. This animal model was feasible for evaluating treatments for peri-prosthetic joint infections (PJI) with a revision surgery and specifically that revision surgery and local antibiotic treatment largely hindered the peri-prosthetic bone loss. Statement of clinical significance: This revision model of peri-prosthetic infection has the potential of comparatively evaluating prophylaxis and treatment strategies and devices. Antibiotic-eluting UHMWPE is devised as at tool in treating PJI while providing weight bearing and joint space preservation.

Choosing the right animal model for osteomyelitis research: Considerations and challenges

Osteomyelitis is a debilitating bone disorder characterized by an inflammatory process involving the bone marrow, bone cortex, periosteum, and surrounding soft tissue, which can ultimately result in bone destruction. The etiology of osteomyelitis can be infectious, caused by various microorganisms, or noninfectious, such as chronic nonbacterial osteomyelitis (CNO) and chronic recurrent multifocal osteomyelitis (CRMO). Researchers have turned to animal models to study the pathophysiology of osteomyelitis. However, selecting an appropriate animal model that accurately recapitulates the human pathology of osteomyelitis while controlling for multiple variables that influence different clinical presentations remains a significant challenge. In this review, we present an overview of various animal models used in osteomyelitis research, including rodent, rabbit, avian/chicken, porcine, minipig, canine, sheep, and goat models. We discuss the characteristics of each animal model and the corresponding clinical scenarios that can provide a basic rationale for experimental selection. This review highlights the importance of selecting an appropriate animal model for osteomyelitis research to improve the accuracy of the results and facilitate the development of novel treatment and management strategies.

Highly Adhesive Antimicrobial Coatings for External Fixation Devices

Pin site infections arise from the use of percutaneous pinning techniques (as seen in skeletal traction, percutaneous fracture pinning, and external fixation for fracture stabilization or complex deformity reconstruction). These sites are niduses for infection because the skin barrier is disrupted, allowing for bacteria to enter a previously privileged area. After external fixation, the rate of pin site infections can reach up to 100%. Following pin site infection, the pin may loosen, causing increased pain (increasing narcotic usage) and decreasing the fixation of the fracture or deformity correction construct. More serious complications include osteomyelitis and deep tissue infections. Due to the morbidity and costs associated with its sequelae, strategies to reduce pin site infections are vital. Current strategies for preventing implant-associated infections include coatings with antibiotics, antimicrobial polymers and peptides, silver, and other antiseptics like chlorhexidine and silver-sulfadiazine. Problems facing the development of antimicrobial coatings on orthopedic implants and, specifically, on pins known as Kirschner wires (or K-wires) include poor adhesion of the drug-eluting layer, which is easily removed by shear forces during the implantation. Development of highly adhesive drug-eluting coatings could therefore lead to improved antimicrobial efficacy of these devices and ultimately reduce the burden of pin site infections. In response to this need, we developed two types of gel coatings: synthetic poly-glycidyl methacrylate-based and natural-chitosan-based. Upon drying, these gel coatings showed strong adhesion to pins and remained undamaged after the application of strong shear forces. We also demonstrated that antibiotics can be incorporated into these gels, and a K-wire with such a coating retained antimicrobial efficacy after drilling into and removal from a bone. Such a coating could be invaluable for K-wires and other orthopedic implants that experience strong shear forces during their implantation.

Recent Advancements in Metallic Drug-Eluting Implants

Over the past decade, metallic drug-eluting implants have gained significance in orthopedic and dental applications for controlled drug release, specifically for preventing infection associated with implants. Recent studies showed that metallic implants loaded with drugs were substituted for conventional bare metal implants to achieve sustained and controlled drug release, resulting in a desired local therapeutic concentration. A number of secondary features can be provided by the incorporated active molecules, including the promotion of osteoconduction and angiogenesis, the inhibition of bacterial invasion, and the modulation of host body reaction. This paper reviews recent trends in the development of the metallic drug-eluting implants with various drug delivery systems in the past three years. There are various types of drug-eluting implants that have been developed to meet this purpose, depending on the drug or agents that have been loaded on them. These include anti-inflammatory drugs, antibiotics agents, growth factors, and anti-resorptive drugs.

Can phosphatidylcholine increase the efficacy of bioactive glass graft when used as a carrier? an experimental study

Aim: Bioactive glass (Bioglass) is a substance causing strong mechanical bondings at the interface of soft tissue-biomaterial-bone through a series of biochemical and biophysical reactions, commonly used to restore developing bone defects due to surgery. On the other hand, phosphatidylcholine is a lipid substance increasing antibiotics’ efficiency as a carrier. Since we met no study using the combination of Bioglass and phosphatidylcholine for bone defects, we aimed to investigate whether the bioglass-phosphatidylcholine combination would be more effective. Material and Method: Thirty Sprague-Dawley 3-6-months-old female rats with a mean weight of 400 gr were divided into five subgroups (six in each group). A 5-mm critical defect was created in the middle of the condyle throughout the burr’s diameter bilaterally. The phosphatidylcholine-bioglass graft was placed at one side, and Bioglass contralaterally to fill the defect. The rats were sacrificed at 24 hours, 72 hours, first, third, and sixth weeks postoperatively. The right and left rat femurs were removed and examined histopathologically. Results: There was no statistically significant difference between the groups regarding filling volume, newly formed and necrotic bone, fibrous tissue, residual graft material, integration, foreign body reaction, and defect organization, indicating that Bioglass served efficiently for filling the defect. In addition, phosphatidylcholine neither augmented nor impaired the healing process. Conclusion: These results indicated that Bioglass served efficiently for filling the defect, and the presence of phosphatidylcholine neither augmented nor impaired the healing process. However, further experimental studies are required until its clinical application is implemented.

Emerging titanium surface modifications: The war against polymicrobial infections on dental implants

Abstract Dental implants made of titanium (Ti) material is recognized as the leading treatment option for edentulous patients’ rehabilitation, showing a high success rate and clinical longevity. However, dental implant surface acts as a platform for microbial adhesion and accumulation once exposed to the oral cavity. Biofilm formation on implant surfaces has been considered the main etiologic factor to induce inflammatory diseases, known as peri-implant mucositis and peri-implantitis; the latter being recognized as the key reason for late dental implant failure. Different factors, such as biofilm matrix production, source of carbohydrate exposure, and cross-kingdom interactions, have encouraged increased microbial accumulation on dental implants, leading to a microbiological community shift from a healthy to a pathogenic state, increasing inflammation and favoring tissue damage. These factors combined with the spatial organization of biofilms, reduced antimicrobial susceptibility, complex microbiological composition, and the irregular topography of implants hamper biofilm control and microbial killing. In spite of the well-known etiology, there is still no consensus regarding the best clinical protocol to control microbial accumulation on dental implant surfaces and treat peri-implant disease. In this sense, different coatings and Ti surface treatments have been proposed in order to reduce microbial loads and control polymicrobial infections on implantable devices. Therefore, this critical review aims to discuss the current evidence on biofilm accumulation on dental implants and central factors related to the pathogenesis process of implant-related infections. Moreover, the potential surface modifications with anti-biofilm properties for dental implant devices is discussed to shed light on further promising strategies to control peri-implantitis.

Fitting pieces into the puzzle: The impact of titanium-based dental implant surface modifications on bacterial accumulation and polymicrobial infections

Polymicrobial infection is the main cause of dental implant failure. Although numerous studies have reported the ability of titanium (Ti) surface modifications to inhibit microbial adhesion and biofilm accumulation, the majority of solutions for the utilization of Ti antibacterial surfaces have been testedin in vitro and animal models, with only a few developed surfaces progressing into clinical research. Motivated by this huge gap, we critically reviewed the scientific literature on the existing antibacterial Ti surfaces to help understand these surfaces' impact on the "puzzle" of undesirable dental implant-related infections. This manuscript comprises three main sections: (i) a narrative review on topics related to oral biofilm formation, bacterial-implant surface interactions, and on how implant-surface modifications can influence microbial accumulation; (ii) a critical evidence-based review to summarize pre-clinical and clinical studies in an attempt to "fit pieces into the puzzle" to unveil the best way to reduce microbial loads and control polymicrobial infection around dental implants showed by the current in vivo evidence; and (iii) discussion and recommendations for future research testing emerging antibacterial implant surfaces, connecting basic science and the requirements for future clinical translation. The findings of the present review suggest no consensus regarding the best available Ti surface to reduce bacterial colonization on dental implants. Smart release or on-demand activation surface coatings are a "new piece of the puzzle", which may be the most effective alternative for reducing microbial colonization on Ti surfaces, and future studies should focus on these technologies.

Antibiotics- and Heavy Metals-Based Titanium Alloy Surface Modifications for Local Prosthetic Joint Infections

Prosthetic joint infection (PJI) is the second most common cause of arthroplasty failure. Though infrequent, it is one of the most devastating complications since it is associated with great personal cost for the patient and a high economic burden for health systems. Due to the high number of patients that will eventually receive a prosthesis, PJI incidence is increasing exponentially. As these infections are provoked by microorganisms, mainly bacteria, and as such can develop a biofilm, which is in turn resistant to both antibiotics and the immune system, prevention is the ideal approach. However, conventional preventative strategies seem to have reached their limit. Novel prevention strategies fall within two broad categories: (1) antibiotic- and (2) heavy metal-based surface modifications of titanium alloy prostheses. This review examines research on the most relevant titanium alloy surface modifications that use antibiotics to locally prevent primary PJI.

Innovations in osteomyelitis research: A review of animal models

Infection of bone tissue, or osteomyelitis, has become a growing concern in modern healthcare due in no small part to a rise in antibiotic resistance among bacteria, notably Staphylococcus aureus. The current standard of care involves aggressive, prolonged antibiotic therapy combined with surgical debridement of infected tissues. While this treatment may be sufficient for resolving a portion of cases, recurrences of the infection and associated risks including toxicity with long-term antibiotic usage have been reported. Therefore, there exists a need to produce safer, more efficacious options of treatment for osteomyelitis. In order to test treatment regimens, animal models that closely mimic the clinical condition and allow for accurate evaluation of therapeutics are necessary. Establishing a model that replicates features of osteomyelitis in humans continues to be a challenge to scientists, as there are many variables involved, including choosing an appropriate species and method to establish infection. This review addresses the refinement of animal models of osteomyelitis to reflect the clinical disease and test prospective therapeutics. The aim of this review is to explore studies regarding the use of animals for osteomyelitis therapeutics research and encourage further development of such animal models for the translation of results from the animal experiment to human medicine.

Targeting implant-associated infections: titanium surface loaded with antimicrobial

Implant devices have = proven a successful treatment modality in reconstructive surgeries. However, increasing rates of peri-implant diseases demand further examination of their pathogenesis. Polymicrobial biofilm formation on titanium surfaces has been considered the main risk factor for inflammatory processes on tissues surrounding implant devices, which often lead to implant failure. To overcome microbial accumulation on titanium surfaces biofilm targeting strategies have been developed to modify the surface and incorporate antimicrobial coatings. Because antibiotics are widely used to treat polymicrobial infections, these agents have recently started to be incorporated on titanium surface. This review discusses the biofilm formation on titanium dental implants and key factors to be considered in therapeutic and preventative strategies. Moreover, a systematic review was conducted on coatings developed for titanium surfaces using different antibiotics. This review will also shed light on potential alternative strategies aiming to reduce microbial loads and control polymicrobial infection on implanted devices.

Antioxidant and antibacterial polyelectrolyte wound dressing based on chitosan/hyaluronan/phosphatidylcholine dihydroquercetin

Antioxidant and antimicrobial wound dressings are the most favorable for acute and chronic wounds treatment. Herein, we formulated a multifunctional polyelectrolyte wound dressing membrane on the basis of chitosan (Ch) and hyaluronan (HA) enhanced by phosphatidylcholine dihydroquercetin (PCDQ). Physicochemical properties and microstructures of fabricated films were investigated adopting Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA) and scanning electron microscope (SEM). Furthermore, water uptakes, wettability profiles, surface roughness, and mechanical characteristics of the developed membranes were studied. The developed wound dressing revealed free radical scavenging potency, hemocompatibility with a tendency to enhance blood clotting. Furthermore, incorporation of PCDQ significantly promoted the antibacterial and anti-inflammatory activities of Ch/HA/PCDQ. Moreover, Ch/HA/PCDQ films exhibited cellular compatibility towards mouse fibroblast cells. The capability of Ch/HA/PCDQ to promote wound healing was evaluated using adult Wistar albino female rats. The in vivo findings demonstrated that Ch/HA/PCDQ films significantly ameliorated mouse full-thickness wounds as evidenced by a reduction in the wound area. Moreover, histological examinations of wounds dressed with Ch/HA/PCDQ illustrated a prominent re-epithelialization compared with wounds handled with the cotton gauze and Ch/HA dressings, exposing the efficiency of PCDQ. These findings emphasized that a Ch/HA/PCDQ membrane has outstanding potential for wound healing and skin regeneration.

Therapeutics and delivery vehicles for local treatment of osteomyelitis

Osteomyelitis, or the infection of the bone, presents a major complication in orthopedics and may lead to prolonged hospital visits, implant failure, and in more extreme cases, amputation of affected limbs. Typical treatment for this disease involves surgical debridement followed by long-term, systemic antibiotic administration, which contributes to the development of antibiotic-resistant bacteria and has limited ability to eradicate challenging biofilm-forming pathogens including Staphylococcus aureus-the most common cause of osteomyelitis. Local delivery of high doses of antibiotics via traditional bone cement can reduce systemic side effects of an antibiotic. Nonetheless, growing concerns over burst release (then subtherapeutic dose) of antibiotics, along with microbial colonization of the nondegradable cement biomaterial, further exacerbate antibiotic resistance and highlight the need to engineer alternative antimicrobial therapeutics and local delivery vehicles with increased efficacy against, in particular, biofilm-forming, antibiotic-resistant bacteria. Furthermore, limited guidance exists regarding both standardized formulation protocols and validated assays to predict efficacy of a therapeutic against multiple strains of bacteria. Ideally, antimicrobial strategies would be highly specific while exhibiting a broad spectrum of bactericidal activity. With a focus on S. aureus infection, this review addresses the efficacy of novel therapeutics and local delivery vehicles, as alternatives to the traditional antibiotic regimens. The aim of this review is to discuss these components with regards to long bone osteomyelitis and to encourage positive directions for future research efforts.

Longitudinal Model of Periprosthetic Joint Infection in the Rat

The majority of periprosthetic joint infections occur shortly after primary joint replacement (<3 months) and require the removal of all implant components for the treatment period (~4 months). A clinically relevant animal model of periprosthetic infection should, therefore, establish an infection with implant components in place. Here, we describe a joint replacement model in the rat with ultrahigh molecular weight polyethylene (UHMWPE) and titanium components inoculated at the time of surgery by methicillin-sensitive Staphylococcus aureus (S. aureus), which is one of the main causative microorganisms of periprosthetic joint infections. We monitored the animals for 4 weeks by measuring gait, weight-bearing symmetry, von Frey testing, and micro-CT as our primary endpoint analyses. We also assessed the infection ex vivo using colony counts on the implant surfaces and histology of the surrounding tissues. The results confirmed the presence of a local infection for 4 weeks with osteolysis, loosening of the implants, and clinical infection indicators such as redness, swelling, and increased temperature. The utility of specific gait analysis parameters, especially temporal symmetry, hindlimb duty factor imbalance, and phase dispersion was identified in this model for assessing the longitudinal progression of the infection, and these metrics correlated with weight-bearing asymmetry. We propose to use this model to study the efficacy of using different local delivery regimens of antimicrobials on addressing periprosthetic joint infections. Statement of clinical significance: We have established a preclinical joint surgery model, in which postoperative recovery can be monitored over a multi-week course by assessing gait, weight-bearing, and allodynia. This model can be used to study the efficacy of different combinations of implant materials and medication regimens. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:1101-1112, 2020.

Evolving concepts in bone infection: redefining "biofilm", "acute vs. chronic osteomyelitis", "the immune proteome" and "local antibiotic therapy"

Osteomyelitis is a devastating disease caused by microbial infection of bone. While the frequency of infection following elective orthopedic surgery is low, rates of reinfection are disturbingly high. Staphylococcus aureus is responsible for the majority of chronic osteomyelitis cases and is often considered to be incurable due to bacterial persistence deep within bone. Unfortunately, there is no consensus on clinical classifications of osteomyelitis and the ensuing treatment algorithm. Given the high patient morbidity, mortality, and economic burden caused by osteomyelitis, it is important to elucidate mechanisms of bone infection to inform novel strategies for prevention and curative treatment. Recent discoveries in this field have identified three distinct reservoirs of bacterial biofilm including: Staphylococcal abscess communities in the local soft tissue and bone marrow, glycocalyx formation on implant hardware and necrotic tissue, and colonization of the osteocyte-lacuno canalicular network (OLCN) of cortical bone. In contrast, S. aureus intracellular persistence in bone cells has not been substantiated in vivo, which challenges this mode of chronic osteomyelitis. There have also been major advances in our understanding of the immune proteome against S. aureus, from clinical studies of serum antibodies and media enriched for newly synthesized antibodies (MENSA), which may provide new opportunities for osteomyelitis diagnosis, prognosis, and vaccine development. Finally, novel therapies such as antimicrobial implant coatings and antibiotic impregnated 3D-printed scaffolds represent promising strategies for preventing and managing this devastating disease. Here, we review these recent advances and highlight translational opportunities towards a cure.

Implant Coating Manufactured by Micro-Arc Oxidation and Dip Coating in Resorbable Polylactide for Antimicrobial Applications in Orthopedics

Prophylaxis and the treatment of implant-related infections has become a key focus area for research into improving the outcome of orthopedic implants. Functional resorbable coatings have been developed to provide an antimicrobial surface on the implant and reduce the risk of infection. However, resorbable coatings developed to date still suffer from low adhesive strength and an inadequate release rate of antibiotics. This study presents a novel double-coating of micro-arc oxidation and resorbable polylactide copolymer on a Ti-6Al-4V implant with the aim of reducing the risk of infection post-implantation. The adhesive strength, rate of coating degradation, and antibiotic release rate were investigated. A key finding was that the micro-arc oxidation coating with the addition of antibiotics increased the adhesive strength of the poly-l-lactide-co-ε-caprolactone (PLC) coatings. The adhesive strength was influenced by the concentration of the PLC solution, the surface structure of the titanium substrate, and the composition of the coatings. The antibiotics blended into the PLC coating had a release cycle of approximately 10 days, which would be long enough to reduce the risk of developing an infection after implantation. The double coatings presented in this study have an excellent potential for reducing the incidence and severity of implants-related early infections.

Animal models of orthopaedic infections. A review of rabbit models used to induce long bone bacterial infections

The development of infections is one of the main complications in orthopaedics, especially in the presence of implants for the osteosynthesis of compound fractures and joint prosthesis. Indeed, foreign materials and implants act as substrates for the adhesion and proliferation of bacterial strains able to produce biofilm, causing peri-implant osteomyelitis. The eradication of biofilm remains a great challenge for the host immune system, as well as for medical and surgical approaches, thus imposing the need for new prophylactic and/or therapeutic strategies in which animal models have an essential role. In vivo orthopaedic models have mainly been used to study the pathogenesis of infections, biofilm behaviour and the efficacy of antimicrobial strategies, to select diagnostic techniques and test the efficacy of novel materials or surface modifications to impede both the establishment of bone infections and the associated septic loosening of implants. Among several models of osteomyelitis and implant-related infections described in small rodents and large animals, the rabbit has been widely used as a reliable and reproducible model of orthopaedic infections. This review examines the relevance of rabbits for the development of clinically representative models by analysing the pros and cons of the different approaches published in the literature. This analysis will aid in increasing our knowledge concerning orthopaedic infections by using this species. This review will be a tool for researchers who need to approach pre-clinical studies in the field of bone infection and have to identify the most appropriate animal model to verify their scientific hypothesis.

Coatings as the useful drug delivery system for the prevention of implant-related infections

Implant-related infections (IRIs) which led to a large amount of medical expenditure were caused by bacteria and fungi that involve the implants in the operation or in ward. Traditional treatments of IRIs were comprised of repeated radical debridement, replacement of internal fixators, and intravenous antibiotics. It needed a long time and numbers of surgeries to cure, which meant a catastrophe to patients. So how to prevent it was more important than to cure it. As an excellent local release system, coating is a good idea by its local drug infusion and barrier effect on resisting biofilms which were the main cause of IRIs. So in this review, materials used for coatings and evidences of prevention were elaborated.

Periprosthetic bacterial biofilm and quorum sensing

Periprosthetic joint infection (PJI) is a common complication after total joint arthroplasty leading to severe morbidity and mortality. With an aging population and increasing prevalence of total joint replacement procedures, the burden of PJI will be felt not only by individual patients, but in increased healthcare costs. Current treatment of PJI is inadequate resulting in incredibly high failure rates. This is believed to be largely mediated by the presence of bacterial biofilms. These polymicrobial bacterial colonies form within secreted extracellular matrices, adhering to the implant surface and local tissue. The biofilm architecture is believed to play a complex and critical role in a variety of bacterial processes including nutrient supplementation, metabolism, waste management, and antibiotic and immune resistance. The establishment of these biofilms relies heavily on the quorum sensing communication systems utilized by bacteria. Early stage research into disrupting bacterial communication by targeting quorum sensing show promise for future clinical applications. However, prevention of the biofilm formation via early forced induction of the biofilm forming process remains yet unexplored. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2331-2339, 2018.

Phosphatidylcholine Coatings Deliver Local Antimicrobials and Reduce Infection in a Murine Model: A Preliminary Study

BACKGROUND

Phosphatidylcholine coatings have been shown to elute antibiotics for several days. A recently developed biofilm inhibitor, cis-2-decenoic acid (C2DA), has been shown to exhibit synergistic activity with several common antibiotics. This study aims to evaluate the effectiveness of C2DA and amikacin dual drug delivery from a phosphatidylcholine coating.

QUESTIONS/PURPOSES

(1) What are the in vitro elution profiles of amikacin and C2DA from phosphatidylcholine-coated coupons in incubated phosphate-buffered saline? (2) Does the presence of C2DA in eluate samples lower the amount of amikacin needed for bacterial inhibition in overnight bacterial turbidity assays? (3) Does addition of amikacin and C2DA result in decreased colony-forming units (CFUs) on wire implants and bone when compared with phosphatidylcholine coatings alone in a mouse model of periprosthetic joint infection?

METHODS

Effects of loading concentrations were assessed during 7-day in vitro elution studies for coatings containing all mixtures of 0%, 5%, 15%, and 25% wt of amikacin and C2DA (n = 4) through quantitative high-performance liquid chromatography concentration determination and plotting concentration eluted over time. Antimicrobial activity was assessed by overnight turbidity testing of elution study samples against Staphylococcus aureus or Pseudomonas aeruginosa. In vivo efficacy was assessed using phosphatidylcholine-coated wire implants in a murine (mouse) model of infection (n = 3). Wire implants were coated with phosphatidylcholine containing no antimicrobials, amikacin alone, C2DA alone, or amikacin and C2DA and then inserted into the intramedullary femur of each mouse and inoculated with S aureus. The number of viable bacterial colonies on the implant surface and in the surrounding bone was determined after 1 week with the goal of achieving complete bacterial clearance. Total viable CFU count and proportion of samples achieving complete clearance were compared between groups.

RESULTS

Elution samples showed a burst response of amikacin and C2DA for 1 to 2 days with C2DA release continuing at low levels through Day 4. All tested eluate samples inhibited P aeruginosa. Samples from coatings containing 25% amikacin or 15% amikacin and any amount of C2DA were able to inhibit S aureus formation, but all coatings with 5% amikacin or 15% amikacin but no C2DA were not inhibitory. All in vivo treatment groups achieved complete bacterial clearance on the wire implant, and the C2DA alone and amikacin alone coatings cleared all CFUs in bone (pin: phosphatidylcholine only one of three; amikacin three of three, C2DA three of three, amikacin + C2DA three of three, p = 0.04 [Fisher's exact test]; bone: coating only: zero of three; amikacin: three of three; C2DA; three of three; C2DA + amikacin: one of three; p = 0.03 [Fisher's exact test]).

CONCLUSIONS

Phosphatidylcholine coatings elute antimicrobials in vitro under infinite sink conditions for up to 4 days in phosphate-buffered saline and were able to reduce bacterial colonies in a preliminary in vivo model. Turbidity testing with eluate samples containing varying amounts of C2DA and amikacin agrees with previous studies showing synergy between them.

CLINICAL RELEVANCE

Used as an adjunctive to systemic therapy, C2DA-loaded phosphatidylcholine coatings have potential value as a prophylactic infection prevention measure. Future studies may include different antibiotics, animal studies with larger sample sizes and more controls, and advanced coating delivery methods.