Vancomycin microspheres reduce postoperative spine infection in an in vivo rabbit model

Local antimicrobial delivery systems for prophylaxis and treatment of periprosthetic traumatological infections

Infections associated with implants are the most serious complications in joint replacement surgeries and can jeopardize the functionality of orthopedic implants. Local antimicrobial delivery could enable antibiotics to attain concentrations above the minimum inhibitory concentration (MIC) threshold at the joint replacement site while preventing systemic side effects. Therefore, there is a dire need for the development of improved biomaterial-based delivery systems for local antibiotic administration in prosthetic infections. In this context, this review highlights the latest breakthroughs in the design of biomaterial-based formulations intended for the prophylaxis and treatment of prosthetic infections. Delivery systems for distinct forms of administration (i.e., direct intra-articular administration, loading into bone cements, coating of implant surfaces, or loading into hydrogels) are here comprehensively compiled with a focus on the design of microparticles and nanosystems for local antimicrobial administration and their impact on distinct in vitro and in vivo models of implant infections.

Impact of implant metal type and vancomycin prophylaxis on postoperative spine infection: an in-vivo study

PURPOSE

To evaluate the effectiveness of vancomycin prophylaxis on spinal implant metal types.

METHODS

42 rabbits underwent posterior, single-level instrumentation at L5-L6 with stainless steel (n = 18), cobalt chrome (n = 12), or titanium (n = 12) wire. All implants were inoculated with 1 × 106 colony forming units (CFU) of methicillin-resistant S. Aureus (MRSA). In the intrawound vancomycin subgroup (n = 18, 6 from each metal type), 40 mg of vancomycin powder was placed in the wound. In the IV vancomycin subgroup (n = 6, all stainless steel), 15 mg/kg of IV vancomycin was given preoperatively. Local soft tissue and implants were harvested 1-week postoperatively and separately cultured.

RESULTS

Intrawound vancomycin significantly reduced the rate of soft tissue infection (44.4% vs 100%) and implant infection (27.8% vs 100%) (p < 0.001). Within the intrawound vancomycin subgroup, cobalt chrome implants were associated with higher median soft tissue MRSA growth (130 CFU) than stainless steel (0 CFU) or titanium (0 CFU) (p = 0.02). Cobalt chrome implants were also more likely to develop soft tissue MRSA infection (83.3%) as compared to stainless steel (16.7%) or titanium (33.3%) (p = 0.04). Median soft tissue MRSA growth among stainless steel implants without prophylaxis, with IV vancomycin, and with vancomycin powder was 1.18 × 107, 195, and 0 CFU, respectively. The rate of soft tissue MRSA infection without prophylaxis, with IV vancomycin, and with vancomycin powder was 100, 66.7, and 16.7%, respectively (p = 0.015).

CONCLUSION

Intrawound vancomycin is more effective than IV vancomycin and effectively reduces the risk of infection, but is less effective in cobalt chrome implants due to residual soft tissue infection.

Epidemiology of postoperative spinal wound infection in the Middle East and North Africa (MENA) region

Background

Despite the extensive literature on postoperative spinal wound infection, yet to our knowledge, there is no previous study containing combined data from several sites in the Middle East and North Africa (MENA) region. This study aimed to estimate the incidence of surgical site infection (SSI) following spine surgeries, its associated factors, and management.

Methods

In a retrospective cohort study, medical records of all patients ≥18 years of age who underwent spine surgery at 6 tertiary referral centers in the MENA region between January 2014 to December 2019 (n=5,872) were examined to collect data on the following: (1) Patient's characteristics, (2) Disease characteristics, (3) Spine surgery approach, and (4) Characteristics of Postoperative SSI. The determinants of postoperative SSI were identified using logistic regression analysis. Receiver operating characteristic (ROC) curve was applied to identify the cut-off of the length of stay in the hospital postoperatively till the infection is likely to occur. Significance was set at p<.05.

Results

The overall incidence of SSI was 4.2% (95% CI: 3.72-4.77), in the form of deep (46.4%), superficial (43.1%), dehiscence (9.3%), and organ space (1.2%) infections. After adjusting for all possible confounders, significant predictors of postoperative SSI were; diabetes (OR=2.12, p<.001), smoking (OR=1.66, p=.002), revision surgery (OR=2.20, p<.001), open surgery (OR=2.73, p<.001), perioperative blood transfusion (OR=1.45, p=.033), ASA class III(OR=2.08, p=.002), and ≥4 days length of stay "LOS" (OR= 1.71, p=.001). A cut-off of 4 days was the optimum LOS above which postoperative SSI is more likely to occur, with 0.70 sensitivity, 0.47 specificity, and 0.61 area under the curve.

Conclusions

This is the first study that highlighted the incidence of postoperative SSI in spine surgery in the MENA region. Incidence figures are comparable to figures in different areas of the world. Identifying predictors of SSI might help high‑risk patients benefit from more intensive wound management.

Role of Animal Models to Advance Research of Bacterial Osteomyelitis

Osteomyelitis is an inflammatory bone disease typically caused by infectious microorganisms, often bacteria, which causes progressive bone destruction and loss. The most common bacteria associated with chronic osteomyelitis is Staphylococcus aureus. The incidence of osteomyelitis in the United States is estimated to be upwards of 50,000 cases annually and places a significant burden upon the healthcare system. There are three general categories of osteomyelitis: hematogenous; secondary to spread from a contiguous focus of infection, often from trauma or implanted medical devices and materials; and secondary to vascular disease, often a result of diabetic foot ulcers. Independent of the route of infection, osteomyelitis is often challenging to diagnose and treat, and the effect on the patient's quality of life is significant. Therapy for osteomyelitis varies based on category and clinical variables in each case. Therapeutic strategies are typically reliant upon protracted antimicrobial therapy and surgical interventions. Therapy is most successful when intensive and initiated early, although infection may recur months to years later. Also, treatment is accompanied by risks such as systemic toxicity, selection for antimicrobial drug resistance from prolonged antimicrobial use, and loss of form or function of the affected area due to radical surgical debridement or implant removal. The challenges of diagnosis and successful treatment, as well as the negative impacts on patient's quality of life, exemplify the need for improved strategies to combat bacterial osteomyelitis. There are many in vitro and in vivo investigations aimed toward better understanding of the pathophysiology of bacterial osteomyelitis, as well as improved diagnostic and therapeutic strategies. Here, we review the role of animal models utilized for the study of bacterial osteomyelitis and their critically important role in understanding and improving the management of bacterial osteomyelitis.

Animal Models for Postoperative Implant‐Related Spinal Infection

Postoperative infections following implant‐related spinal surgery are severe and disastrous complications for both orthopaedic surgeons and patients worldwide. They can cause neurological damage, disability, and death. To better understand the mechanism of these destructive complications and intervene in the process, further research is needed. Therefore, there is an urgent need for efficient, accurate, and easily available animal models to study the pathogenesis of spinal infections and develop new and effective anti‐bacterial methods. In this paper, we provide a general review of the commonly used animal models of postoperative implant‐related spinal infections, describe their advantages and disadvantages, and highlight the significance of correctly choosing the model according to the infection aspect under investigation. These models are valuable tools contributing to the better understanding of postoperative spinal infections and will continue to facilitate the invention of novel preventative and treatment strategies for patients with postoperative spinal infections. However, although they are valid and reproducible in some respects, the current animal models present certain limitations. Future ideal spinal infection animal models may assess the bacterial load of the same animal in real‐time in vivo, and better mimic the human anatomy as well as surgical techniques. Strains other than Staphylococcus aureus account for a large proportion of postoperative spinal infections, and thus, the establishment of models to evaluate other types of microbial infections is expected in the future. Furthermore, novel transgenic models established on advancements in genome editing are also likely to be developed in the future.

Preventing Staphylococcus aureus stainless steel-associated infections in orthopedics. A systematic review and meta-analysis of animal literature

Surgical site infection in the presence of orthopedic implants poses significant healthcare and socioeconomic burden. To assess the potential of various prevention strategies against Staphylococcus-induced stainless steel-associated infections, a review of animal evidence was designed. The databases of PubMed, Embase, and CENTRAL were searched until March 10, 2020, for articles including animal models with stainless steel instrumentation and techniques to prevent Staphylococcus infection. We conducted a random-effects meta-analysis of standardized mean differences (SMD) with subgroup analysis linked to various protection strategies and we recorded complications. Quality was assessed with the SYRCLE's risk of bias tool. Twenty-five studies were included. Combined active coating (featuring organic antibacterial compound release) and degradable passive finishing (lipid- or polymer-based structure modification reducing bacterial adhesion) was favored over untreated controls (SMDs for methicillin-sensitive Staphylococcus aureus [MSSA] and methicillin-resistant Staphylococcus aureus [MRSA] were -3.46, 95% CI [-4.53 to -2.4], p < .001 [n = 4 head-to-head comparisons]; and -6.67, 95% CI [-10.53 to -3], p < .001 [n = 5 head-to-head comparisons], respectively). Systemic vitamin D supplementation and systemic antibiotic administration with or without local antibiotics demonstrated favorable outcomes against MSSA infection. On the contrary, no benefit was seen following vaccination. Of note, no side effects were documented. On the basis of data gathered from eight studies, which comprised 294 animals, a bioresorbable polymer- or lipid-based surface modification supplemented with organic coating yielded improved infection-related outcomes against MSSA and MRSA stainless steel infections, and therefore, this strategy could be further investigated in human research.

A Novel Strategy to Coat Dopamine-Functionalized Titanium Surfaces With Agarose-Based Hydrogels for the Controlled Release of Gentamicin

Introduction

The use of spinal implants for the treatment of back disorders is largely affected by the insurgence of infections at the implantation site. Antibacterial coatings have been proposed as a viable solution to limit such infections. However, despite being effective at short-term, conventional coatings lack the ability to prevent infections at medium and long-term. Hydrogel-based drug delivery systems may represent a solution controlling the release of the loaded antibacterial agents while improving cell integration. Agarose, in particular, is a biocompatible natural polysaccharide known to improve cell growth and already used in drug delivery system formulations. In this study, an agarose hydrogel-based coating has been developed for the controlled release of gentamicin (GS).

Methods

Sand blasted Ti6Al4V discs were grafted with dopamine (DOPA) solution. After, GS loaded agarose hydrogels have been produced and additioned with tannic acid (TA) and calcium chloride (CaCl₂) as crosslinkers. The different GS-loaded hydrogel formulations were deposited on Ti6Al4V-DOPA surfaces, and allowed to react under UV irradiation. Surface topography, wettability and composition have been analyzed with profilometry, static contact angle measurement, XPS and FTIR spectroscopy analyses. GS release was performed under pseudo-physiological conditions up to 28 days and the released GS was quantified using a specific ELISA test. The cytotoxicity of the produced coatings against human cells have been tested, along with their antibacterial activity against S. aureus bacteria.

Results

A homogeneous coating was obtained with all the hydrogel formulations. Moreover, the coatings presented a hydrophilic behavior and micro-scale surface roughness. The addition of TA in the hydrogel formulations showed an increase in the release time compared to the normal GS-agarose hydrogels. Moreover, the GS released from these gels was able to significantly inhibit S. aureus growth compared to the GS-agarose hydrogels. The addition of CaCl₂ to the gel formulation was able to significantly decrease cytotoxicity of the TA-modified hydrogels.

Conclusions

Due to their surface properties, low cytotoxicity and high antibacterial effects, the hereby proposed gentamicin-loaded agarose-hydrogels provide new insight, and represent a promising approach for the surface modification of spinal implants, greatly impacting their application in the orthopedic surgical scenario.

Preclinical models of vertebral osteomyelitis and associated infections: Current models and recommendations for study design

Spine-related infections, such as vertebral osteomyelitis, discitis, or spondylitis, are rare diseases that mostly affect adults, and are usually of hematogenous origin. The incidence of this condition has gradually risen in recent years because of increases in spine-related surgery and hospital-acquired infections, an aging population, and intravenous (IV) drug use. Spine infections are most commonly caused by Staphylococcus aureus, while other systemic infections such as tuberculosis and brucellosis can also cause spondylitis. Various animal models of vertebral osteomyelitis and associated infections have been investigated in mouse, rat, chicken, rabbit, dog, and sheep models by hematogenous and direct inoculation in surgery, each with their strengths and limitations. This review is the first of its kind to concisely analyze the various existing animal models used to reproduce clinically relevant models of infection. Spine-related infection models must address the unique anatomy of the spine, the avascular nature of its structures and tissues and the consequences of tissue destruction such as spinal cord compression. Further investigation is necessary to elucidate the specific mechanisms of host-microbe response to inform antimicrobial therapy and administration techniques in a technically demanding body cavity. Small-animal models are not suitable for large instrumentation, and difficult IV access thwarts antibiotic administration. In contrast, large-animal models can be implanted with clinically relevant instrumentation and are resilient to repeat procedures to study postoperative infection. A canine model of infection offers a unique opportunity to design and investigate antimicrobial treatments through recruitment a rich population of canine patients, presenting with a natural disease that is suitable for randomized trials.

Topical vancomycin for treatment of methicillin-resistant Staphylococcus epidermidis infection in a rat spinal implant model

STUDY DESIGN

Basic science.

OBJECTIVE

Investigate the ability of local applicaiton of vancomycin, either in powder form or suspended within poly(lactic-co-glycolic acid) microspheres (MS), to treat infection using a rat spinal model. Surgical site infections (SSIs) are a serious complication after spine surgery and are associated with high morbidity and mortality and often caused my coagulase negative staphylococci. A comprehensive approach to reduce SSIs has been recommended including the use of topical vancomycin. Animal and human studies have shown improved control of infection with local compared to systemic antibiotics.

METHODS

K-wires seeded with methicillin-resistant Staphylococcus epidermidis RP62A (MRSE) were treated with vancomycin powder, carboxymethylcellulose sodium salt (CMC) (microsphere carrier), vancomycin powder, blank MS or vancomycin-loaded MS for 24 or 48 h in vitro after which bacteria were enumerated. In addition, a spinal instrumentation model was developed in rats with a bacterial seeded K-wire implanted into the right side of L4 and L5. Rats underwent no treatment or were treated locally with either vancomycin powder, blank MS or vancomycin-loaded MS. After 8 weeks, the K-wire, bone, soft tissue and wire fastener were cultured and results analyzed.

RESULTS

Vancomycin powder and vancomycin-loaded MS resulted in significantly fewer bacteria remaining in vitro than did CMC. Vancomycin powder- treated animals' cultures were significantly lower than all other groups (P < 0.0001) with negative culture results, except for one animal. The vancomycin-loaded MS-treated animals had lower bone bacterial counts than the controls (P < 0.0279); blank MS-treated animals had no differences in bacterial densities when compared to non-treated animals.

CONCLUSION

Vancomycin powder and vancomycin-loaded MS were active against MRSE in vitro, in a rat MRSE implant model; however, vancomycin MS were inferior to the topical vancomycin powder. Vancomycin powder prevented MRSE infection in a rat spinal implant infection model.

Spinal Fusion Surgery and Local Antibiotic Administration: A Systematic Review on Key Points From Preclinical and Clinical Data

STUDY DESIGN

Systematic review.

OBJECTIVE

The present review of clinical and preclinical in vivo studies focused on the local antibiotic administration for surgical site infection (SSI) in spinal fusion procedures and identifying new approaches or research direction able to release antibiotics in the infected environment.

SUMMARY OF BACKGROUND DATA

SSI is a severe complication of spinal fusion procedures that represents a challenging issue for orthopedic surgeons. SSIs can range from 0.7% to 2.3% without instrumentation up to 6.7% with the use of instrumentation with significant implications in health care costs and patient management.

METHOD

A systematic search was carried out by two independent researchers according to the PRISMA statement in three databases (www.pubmed.com, www.scopus.com and www.webofknowledge.com) to identify preclinical in vivo and clinical reports in the last 10 years. Additionally, to evaluate ongoing clinical trials, three of the major clinical registry websites were also checked (www.clinicaltrials.gov, www.who.int/ictrp, https://www.clinicaltrialsregister.eu).

RESULTS

After screening, a total of 43 articles were considered eligible for the review: 36 clinical studies and seven preclinical studies. In addition, six clinical trials were selected from the clinical registry websites.

CONCLUSION

The results reported that the topical vancomycin application seem to represent a strategy to reduce SSI incidence in spine surgery. However, the use of local vancomycin as a preventive approach for SSIs in spine surgery is mostly based on retrospective studies with low levels of evidence and moderate/severe risk of bias that do not allow to draw a clear conclusion. This review also underlines that several key points concerning the local use of antibiotics in spinal fusion still remains to be defined to allow this field to make a leap forward that would lead to the identification of specific approaches to counteract the onset of SSIs.

LEVEL OF EVIDENCE

4.

Efficacy and Cost-effectiveness of Topical Vancomycin Powder in Primary Cementless Total Hip Arthroplasty

Topical vancomycin has been shown to effectively reduce infections after spinal surgery while remaining safe and cost-effective; however, there are few studies evaluating topical vancomycin in total hip arthroplasty. The authors hypothesized that the incidence of periprosthetic joint infection would decrease with the use of topical vancomycin in total hip arthroplasty and that topical vancomycin would be cost-effective. A retrospective patient chart review was performed to evaluate consecutive primary cementless total hip arthroplasties performed in the authors' hospital system between April 2015 and December 2016. Demographic data were collected. Periprosthetic joint infection was defined by Musculoskeletal Infection Society criteria. Statistical analysis included t test, Fisher's exact test, and logistic regression. The costs of vancomycin and postoperative infection were used to determine the absolute risk reduction (1/number needed to treat) threshold needed for topical vancomycin to be cost-effective. In this study, 309 patients (55.7%) undergoing total hip arthroplasty were treated with topical vancomycin, and 246 patients (44.3%) did not receive treatment. There were 2 infections in the vancomycin group (0.6% incidence), and 4 in the no vancomycin group (1.6% incidence). There was no statistical difference in infection rate between the 2 cohorts (P=.414). The absolute risk reduction was 0.98%, and the number needed to treat with topical vancomycin was 102 patients to prevent 1 periprosthetic joint infection. Topical vancomycin ($12 per vial) resulted in an expected cost savings of $904 per patient. Topical vancomycin is inexpensive and cost-effective. Although not statistically significant, the topical vancomycin group had a 60% lower incidence of infection. Further research regarding appropriate prophylactic topical and intravenous antibiotic use is needed prior to widespread adoption. [Orthopedics. 2019; 42(5):e430-e436.].

Postoperative Spine Infection: Diagnosis and Management

STUDY DESIGN

Review article.

OBJECTIVES

A review of the literature on postoperative spinal infections, their diagnosis, and management.

METHODS

A systematic computerized Medline literature search was performed using PubMed, Cochrane Database of Systematic Reviews, and EMBASE. The electronic databases were searched for publication dates from the last 10 years. The searches were performed from Medical Subject Headings (MeSH) used by the National Library of Medicine. Specifically, MeSH terms "spine," "infections," "management," and "diagnosis" were used.

RESULTS

Currently, the gold standard for diagnosis of postoperative spine infection is positive deep wound culture. Many of the current radiologic and laboratory tests can assist with the initial diagnosis and monitoring treatment response. Currently erythrocyte sedimentation rate, C-reactive protein, computed tomography scan, and magnetic resonance imaging with and without contrast are used in combination to establish diagnosis. Management of postoperative spine infection involves thorough surgical debridement and targeted antibiotic therapy.

CONCLUSIONS

Postoperative spine infection is a not uncommon complication following surgery that may have devastating consequences for a patient's short- and long-term health. A high index of suspicion is needed to make an early diagnosis.

Options and Limitations in Clinical Investigation of Bacterial Biofilms

Bacteria can form single- and multispecies biofilms exhibiting diverse features based upon the microbial composition of their community and microenvironment. The study of bacterial biofilm development has received great interest in the past 20 years and is motivated by the elegant complexity characteristic of these multicellular communities and their role in infectious diseases. Biofilms can thrive on virtually any surface and can be beneficial or detrimental based upon the community's interplay and the surface. Advances in the understanding of structural and functional variations and the roles that biofilms play in disease and host-pathogen interactions have been addressed through comprehensive literature searches. In this review article, a synopsis of the methodological landscape of biofilm analysis is provided, including an evaluation of the current trends in methodological research. We deem this worthwhile because a keyword-oriented bibliographical search reveals that less than 5% of the biofilm literature is devoted to methodology. In this report, we (i) summarize current methodologies for biofilm characterization, monitoring, and quantification; (ii) discuss advances in the discovery of effective imaging and sensing tools and modalities; (iii) provide an overview of tailored animal models that assess features of biofilm infections; and (iv) make recommendations defining the most appropriate methodological tools for clinical settings.

Mesoporous silica nanoparticles/gelatin porous composite scaffolds with localized and sustained release of vancomycin for treatment of infected bone defects

A highly porous composite scaffold with localized and sustained antibiotic release property for treatment of infected bone defects.