Local control of polymicrobial infections via a dual antibiotic delivery system

The effect of different flushing and locking techniques on catheter occlusion rates in central venous catheters: protocol for a multicentre, randomized controlled, parallel-group, open-label, superiority clinical trial

BACKGROUND

Maintaining venous access is of great clinical importance. Running a slow continuous infusion to keep the vein open (KVO) is often used in peripheral intravenous catheters (PIVCs). Previous studies have compared the effects of intermittent flushing and continuous infusion via peripherally inserted central catheters (PICCs). In this study, we applied KVO to central venous catheters (CVCs) and compared the occlusion rate of this technique with that of the intermittent flushing technique.

METHOD

This is a randomized controlled trial of 14 hospitals in China. A total of 250 patients will be recruited in this study, and they will be randomized at a 1:1 ratio. After study inclusion, patients who will undergo CVC insertion will receive intermittent flushing with prefilled saline syringes (control group) or KVO infusion with elastic pumps (test group). All the catheters will be checked for patency by scoping Catheter Injection and Aspiration (CINAS) Classification on Days 3 and 7. The primary outcome is the rate of catheter occlusion in 7 days. Patients will be followed up until 9 days after CVC insertion, catheter occlusion, or catheter removal. The secondary outcomes are the rate of catheter occlusion in 3 days, nurse satisfaction, cost-effectiveness, adverse event rate, catheter-related bloodstream infection rate, catheter-related thrombosis rate, extravasation rate, phlebitis rate, and catheter migration.

DISCUSSION

We expect that the trial will generate findings that can provide an evidence-based basis for the improvement and optimization of clinical catheter flushing techniques.

TRIAL REGISTRATION

Chinese Clinical Trial Registry, ChiCTR2200064007. Registered on 23 September 2022. https://www.chictr.org.cn/showproj.html?proj=177311 .

Analysis of risk factors for the recurrence of osteomyelitis of the limb after treatment with antibiotic-loaded calcium sulfate and autologous bone graft

Objective

We aimed to evaluate the efficacy of antibiotic-loaded calcium sulfate combined with autologous iliac bone transplantation in the treatment of limb-localized osteomyelitis (Cierny-Mader type III) and analyze the causes and risk factors associated with infection recurrence.

Methods

Clinical data of 163 patients with localized osteomyelitis of the extremities treated with antibiotic-loaded calcium sulfate combined with autologous iliac bone transplantation in Xi'an Honghui Hospital from January 2017 to December 2022 were retrospectively analyzed. All patients were diagnosed with localized osteomyelitis through clinical examination and treated with antibiotic-loaded calcium sulfate combined with autologous iliac bone. Based on the infection recurrence status, the patients were divided into the recurrence group and the non-recurrence group. The clinical data of the two groups were compared using univariate analysis. Subsequently, the distinct datasets were included in the binary logistic regression analysis to determine the risk and protective factors.

Results

This study included 163 eligible patients, with an average age of 51.0 years (standard deviation: 14.9). After 12 months of follow-up, 25 patients (15.3%) experienced infection recurrence and were included in the recurrence group; the remaining 138 patients were included in the non-recurrence group. Among the 25 patients with recurrent infection, 20 required reoperation, four received antibiotic treatment alone, and one refused further treatment. Univariate analysis showed that education level, smoking, hypoproteinemia, open injury-related infection, and combined flap surgery were associated with infection recurrence (p < 0.05). Logistic regression analysis showed that open injury-related infection (odds ratio [OR] = 35.698; 95% confidence interval [CI]: 5.997-212.495; p < 0.001) and combined flap surgery (OR = 41.408; 95% CI: 5.806-295.343; p < 0.001) were independent risk factors for infection recurrence. Meanwhile, high education level (OR = 0.009; 95% CI: 0.001-0.061; p < 0.001) was a protective factor for infection recurrence.

Conclusion

Antibiotic-loaded calcium sulfate combined with autologous iliac bone transplantation is an effective method for treating limb-localized osteomyelitis. Patients without previous combined flap surgery and non-open injury-related infections have a relatively low probability of recurrence of infection after treatment with this surgical method. Additionally, patients with a history of smoking and hypoproteinemia should pay attention to preventing the recurrence of infection after operation. Providing additional guidance and support, particularly in patients with lower education levels and compliance, could contribute to the reduction of infection recurrence.

Distribution of pathogens and risk factors for post-replantation wound infection in patients with traumatic major limb mutilation

PURPOSE

Even though replantation of limb mutilation is increasing, postoperative wound infection can result in increasing the financial and psychological burden of patients. Here, we sought to explore the distribution of pathogens and identify risk factors for postoperative wound infection to help early identification and managements of high-risk patients.

METHODS

Adult inpatients with severed traumatic major limb mutilation who underwent replantation from Suzhou Ruixing Medical Group between November 09, 2014, and September 6, 2022 were included in this retrospective study. Demographic, and clinical characteristics, treatments, and outcomes were collected. Data were used to analyze risk factors for postoperative wound infection.

RESULTS

Among the 249 patients, 185 (74.3%) were males, the median age was 47.0 years old. Postoperative wound infection in 74 (29.7%) patients, of whom 51 (20.5%) had infection with multi-drug resistant bacteria. Ischemia time (OR 1.31, 95% CI 1.13-1.53, P = 0.001), wound contamination (OR 6.01, 95% CI 2.38-15.19, P <0.001), and stress hyperglycemia (OR 23.37, 95% CI 2.30-236.93, P = 0.008) were independent risk factors, while the albumin level after surgery (OR 0.94, 95% CI 0.89-0.99, P = 0.031) was significant associated with the decrease of postoperative wound infection. Ischemia time (OR 1.21, 95% CI 1.05-1.40, P = 0.010), wound contamination (OR 8.63, 95% CI 2.91-25.57, P <0.001), and MESS (OR 1.32, 95% CI 1.02-1.71, P = 0.037 were independent risk factors for multi-drug resistant bacteria infection.

CONCLUSIONS

Post-replantation wound infection was common in patients with severe traumatic major limb mutilation, and most were multi-drug resistant bacteria. Ischemia time and wound contamination were associated with the increase of postoperative wound infection, including caused by multi-drug resistant. Positive correction of hypoproteinemia and control of stress hyperglycemia may be beneficial.

Effects of the low-speed continuous infusion catheter technique on double-lumen central venous catheters: A randomized controlled trial

BACKGROUND

Central venous catheters are widely used in clinical practice, and the incidence of central venous catheter occlusion is between 25 % and 38 %. The turbulence caused by the pulsatile flushing technique is harmful to the vascular endothelium and may lead to phlebitis. The low-speed continuous infusion catheter technique is a new type of continuous infusion that ensures that the catheter is always in a keep-vein-open state by continuous low-speed flushing; hence, avoiding the problem of catheter occlusion.

OBJECTIVE

To investigate the effectiveness of the low-speed continuous infusion catheter technique and the routine care of double-lumen central venous catheters.

DESIGN

This was a prospective, randomized, controlled, open-label trial.

SETTING

Patients were recruited from 14 medical institutions in China between February and June 2023.

PARTICIPANTS

In total, 251 patients were recruited, with 125 in the intervention group and 126 in the control group.

METHODS

Patients who used double-lumen central venous catheters for infusion treatment were selected, and those who met the sampling criteria were randomly divided into intervention and control groups using the random envelope method. The intervention group used the low-speed continuous infusion catheter technique to maintain catheter patency, whereas the control group used routine care with a trial period of 7 days. The primary outcome was the occlusion rate. The secondary outcomes included nursing satisfaction and complication rates of the two groups.

RESULTS

After 7 days, the rate of catheter occlusion was 28.0 % (35/125, 95 % confidence interval (CI):0.203, 0.367) in the intervention group and 53.97 % (68/126, 95 % CI: 0.449-0.629) in the control group, with a statistically significant difference (χ2 = 17.488, p < 0.001); at 3 days of intervention, the rate of catheter blockage was 8.0 % (10/125, 95 % CI: 0.039-0.142) in the intervention group and 23.8 % (30/126, 0.167-0.322) in the control group, with a statistically significant difference (χ2 = 11.707, p < 0.001). Nurse satisfaction was significantly higher in the intervention group (115/125, 92.0 %, 95 % CI: 0.858-0.961) than in the control group (104/126, 82.54 %, 95 % CI: 0.748-0.887) (χ2 = 5.049, p = 0.025). There were no statistically significant complication rates in either group (p = 0.622).

CONCLUSION

The low-speed continuous infusion catheter technique helps maintain catheter patency, improves nurse satisfaction, and provides a high level of safety.

REGISTRATION

Chinese Clinical Trial Registry (ChiCTR2200064007, www.chictr.org.cn). The first recruitment was conducted in February. https://www.chictr.org.cn/showproj.html?proj=177311.

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

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

Chitosan Sponges Are Associated With Higher Rates of Wound Complications Compared to Calcium Sulfate Beads

Background In this study, we aimed to determine if there is a difference in the rates of wound dehiscence, delayed union, nonunion, and unanticipated surgery after the use of bioabsorbable local antibiotic-delivery systems (LADS), specifically comparing antibiotic-impregnated calcium sulfate pellets (Osteoset-T, Wright Medical Technology Inc., Arlington, TN, USA, hereafter referred to as beads) and chitosan sponge (Sentrex BioSponge, Bionova Medical, Germantown, TN, USA, hereafter referred to as sponges) in the management of acute and chronic extremity wounds. Methodology We conducted a retrospective comparative cohort study in the setting of a level 1 trauma center. All patients who received either beads or sponges as an adjunct to surgical debridement from January 2010 to December 2017 were included, and 136 patients met the inclusion criteria. The intervention studied was extremity wounds that were treated with bioabsorbable LADS, either beads or sponges. The main outcome measurement was wound dehiscence and the need for unanticipated surgery. Results Of the 136 patients in the study cohort, 78% (106/136) were treated with beads, and 22% (30/136) were treated with sponges. Of the 136 patients, 50 (37%) experienced wound dehiscence, and 49 patients required unanticipated surgery. Overall, 62% (31/50) of patients with wound dehiscence and 67.4% (33/49) of patients requiring unanticipated surgery were seen in the bead cohort (p = 0.0001 and 0.025, respectively). However, in multivariable analyses, we found that the odds of having wound dehiscence and undergoing unanticipated surgery were, respectively, 4.9 (p = 0.001) and 2.8 (p = 0.021) times more likely to occur in the sponge than in the bead group. Conclusions Sentrex sponges appear to be associated with higher rates of wound dehiscence and the need for unanticipated surgery compared to Osteoset beads.

Changes of the microbiological spectrum and antibiotic resistance pattern in postoperative spinal implant infections with multiple culture-positive revision surgeries

BACKGROUND CONTEXT

In severe cases of postoperative spinal implant infections (PSII) multiple revision surgeries may be needed. Little is known if changes in the microbiological spectrum and antibiotic resistance pattern occur between revision surgeries.

PURPOSE

Analysis of the microbiological spectrum and antibiotic resistance pattern in patients with multiple revision surgeries for the treatment of PSII STUDY DESIGN: Retrospective database analysis.

PATIENT SAMPLE

Between 01/2011 and 12/2018, 103 patients underwent 248 revision surgeries for the treatment of PSII. Twenty patients (19.4%) who underwent multiple revision surgeries for PSII were included in this study.

OUTCOME MEASURES

Microbiological spectrum, antibiotic resistance pattern.

METHODS

A retrospective analysis of a prospectively maintained single center spine infection database was performed with a minimum follow-up of 3 years. Overall, 20 patients (six male/14 female) underwent 82 revisions for PSII (median 3; range 2-12). There were 55 of 82 (67.1%) procedures with a positive microbiological result. Microbiological analysis was performed on tissue and implant sonication fluid. Changes in microbial spectrum and antibiotic resistance pattern between surgeries were evaluated using Chi-Square and Fisher's exact test.

RESULTS

In total, 74 microorganisms (83.3% gram-positive; 10.8% gram-negative) were identified. The most common microorganisms were Staphylococcus epidermidis (18.9%) and Cutibacterium acnes (18.9%). All S. epidermidis identified were methicillin-resistant (MRSE). Overall, there were 15 of 55 (27.3%) polymicrobial infections. The microbiological spectrum changed in 57.1% (20/35) between the revision stages over the entire PSII period. In 42.9% (15/35) the microorganism persisted between the revision surgeries stages. Overall, changes of the antibiotic resistance pattern were seen in 17.4% (8/46) of the detected microorganisms, comparing index revision and all subsequent re-revisions. Moreover, higher resistance rates were found for moxifloxacin and for ciprofloxacin at first re-revision surgery compared with index PSII revision. Resistances against vancomycin increased from 4.5% (1/23) at index PSII revision to 7.7% (2/26) at first re-revision surgery.

CONCLUSIONS

Changes of the microbiological spectrum and the resistance pattern can occur in patients with severe PSII who require multiple revision surgeries. It is important to consider these findings in the antimicrobial treatment of PSII. The microbiological analysis of intraoperative tissue samples should be performed at every revision procedure for PSII.

Localized, on-demand, sustained drug delivery from biopolymer-based materials

INTRODUCTION

Local drug delivery facilitiates higher concentrations of drug molecules at or near the treatment site to enhance treatment efficiency and reduce drug toxicity and other systemic side effects. However, local drug delivery systems face challenges in terms of encapsulation, delivery, and controlled release of therapeutics.

AREAS COVERED

We provide an overview of naturally derived biopolymer-based drug delivery systems for localized, sustained, and on-demand treatment. We introduce the advantages and limitations of these systems for drug encapsulation, delivery, and local release, as well as recent applications.

EXPERT OPINION

Naturally derived biopolymers like cellulose, silk fibroin, chitosan, alginate, hyaluronic acid, and gelatin are good candidates for localized drug delivery because they are readily chemically modified, biocompatible, biodegradable (with the generation of metabolically compatible degradation products), and can be processed in aqueous and ambient environments to maintain the bioactivity of various therapeutics. The tradeoff between the effective treatment dosage and the response by local healthy tissue should be balanced during the design of these delivery systems. Future directions will be focused on strategies to design tunable and controlled biodegradation rates, as well as to explore commercial utility in substituting biopolymer-based systems for currently utilized synthetic polymers for implants for drug delivery.

Fracture Related Infections and Their Risk Factors for Treatment Failure—A Major Trauma Centre Perspective

Fracture related infections (FRI) are debilitating and costly complications of musculoskeletal trauma surgery that can result in permanent functional loss or amputation. Surgical treatment can be unsuccessful, and it is necessary to determine the predictive variables associated with FRI treatment failure, allowing one to optimise them prior to treatment and identify patients at higher risk. The clinical database at a major trauma centre was retrospectively reviewed between January 2015 and January 2021. FRI treatment failure was defined by infection recurrence or amputation. A univariable logistic regression analysis was performed, followed by a multivariable regression analysis for significant outcomes between groups on univariable analysis, to determine risk factors for treatment failure. In total, 102 patients were identified with a FRI (35 open, 67 closed fractures). FRI treatment failure occurred in 24 patients (23.5%). Risk factors determined by our multivariate logistic regression model were obesity (OR 2.522; 95% CI, 0.259–4.816; p = 0.006), Gustilo Anderson type 3c (OR 4.683; 95% CI, 2.037–9.784; p = 0.004), and implant retention (OR 2.818; 95% CI, 1.588–7.928; p = 0.041). Given that FRI treatment in 24 patients (23.5%) ended up in failure, future management need to take into account the predictive variables analysed in this study, redirect efforts to improve management and incorporate adjuvant technologies for patients at higher risk of failure, and implement a multidisciplinary team approach to optimise risk factors such as diabetes and obesity.

Identifying alternative antibiotics that elute from calcium sulfate beads for treatment of orthopedic infections

There has been increasing interest in the use of a synthetic absorbable calcium sulfate (CaSO₄ ) for local antibiotic delivery in orthopaedic infections. The purpose of this study was to quantify elution kinetics of six antibiotics (amikacin, meropenem, fosfomycin, minocycline, cefazolin, and dalbavancin) from a clinically relevant CaSO₄ bead model and compare elution and antimicrobial activity to the current clinical gold standards: vancomycin and tobramycin. Antibiotic-loaded synthetic CaSO₄ beads were immersed in phosphate buffered saline and incubated at 37°C. Eluent was harvested at eight time points over 28 days. Antibiotic concentrations were measured by high performance liquid chromatography to quantify elution rates. CaSO₄ beads demonstrated burst release kinetics. Dalbavancin, cefazolin, and minocycline all demonstrated similar elution profiles to vancomycin. Amikacin and meropenem demonstrated favorable elution profiles and durations of above-minimum inhibitory concentration when compared to tobramycin. Clinical Significance: This study provides important novel data regarding the utility of amikacin, meropenem and dalbavancin as alternative choices to place in CaSO₄ carriers when treating orthopaedic infections.

Effect of Local Delivery of Vancomycin and Tobramycin on Bone Regeneration

OBJECTIVE

A bone defect rat model was established to investigate the osteogenic effect of local delivery two antibiotics (vancomycin and tobramycin powder) on bone regeneration.

METHODS

Twenty-four Sprague-Dawley (SD) male rats (6 to 8 weeks, 200 to 250 g) were used in this study. All these rats were randomly divided into four groups. Based on dose conversion between rat and human via body surface area, the rat dose of two antibiotics was 88μg/g and 176 μg/g for vancomycin and tobramycin, respectively. Con group (no antibiotic), Van group (vancomycin, 88 μg/g), Tob group (tobramycin 176 μg/g), and Van+Tob group (vancomycin 88μg/g combined with tobramycin 176 μg/g). A 5.0-mm full-thickness standardized mandibular bone defect was performed with a drill in each rat and different antibiotic powders were placed over the bone defect space, respectively. All these animals were sacrificed after 12 weeks post-operation. The mandible bones were harvested for further radiographic and histologic analysis. The bone volume/total volume (BV/TV) ratio, bone volume (BV), and bone fractional area (BFA) in the defect area via micro-computed tomography (μCT scanning) were further analyzed. Then, we performed a histological assessment via hematoxylin and eosin (H&E) and Masson's trichrome staining to analyze bone regeneration and also analyze the number of osteoblasts per filed.

RESULTS

There were no postoperative deaths, signs of vancomycin-related or tobramycin-related toxicity, or signs of systemic illness in any of the four groups. All wounds healed well, and no complications or surgical site infection were observed in all rats. From the μCT scans analyses, there was less bone regeneration in the Van group than in the Con group (BV/TV: F = 64.29, R²  = 0.9602; P = 0.0052; BFA: F = 76.17, R²  = 0.9662, P = 0.0007; BV: F = 194.4, R²  = 0.9865, P = 0.0022). However, when the tobramycin and vancomycin were combined, an increase in bone defect re-ossification was found in the Van+Tob group than in the Van group (BV/TV: F = 64.29, R²  = 0.9602, P = 0.0033; BFA: F = 76.17, R²  = 0.9662, P = 0.0006; BV: F = 194.4, R²  = 0.9865, P = 0.0033). Routine H&E and Masson staining supported the finding of μCT scanning. Quantitative indices confirmed that both the bone regeneration and the number of osteoblasts per filed in the defect area was higher in the Van+Tob group than in the Van group (percentage of bone tissue: F = 145.7, R²  = 0.9562, P = 0.0008; number of osteoblasts per file; F = 67.3, R²  = 0.9098, P < 0.0001). There was no significant difference between the Con group and the Van+Tob group on the number of osteoblasts each field (F = 145.7, R²  = 0.9562, P > 0.9999).

CONCLUSION

For bone defect, local application of vancomycin combined with tobramycin was recommended over vancomycin alone. This animal study presents data suggesting that the use of local delivery of vancomycin and tobramycin should be investigated further in clinical studies.

Therapeutic effects of chitosan in veterinary dermatology: A systematic review of the literature

Chitosan is a natural polysaccharide with biocompatibility, biodegradability, nontoxicity, antimicrobial, and hemostatic properties. This biopolymer has been used in different pharmaceutical forms; therefore, it has an attractive potential for dermal applications in veterinary medicine. The aim of this review is to assess the healing potential of chitosan, based on its dermatological effects on animals, to enrich the therapeutic options of veterinary clinicians. A systematic review was conducted based on the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) strategy, retrieving 1,032 studies and selecting 39 after the inclusion and exclusion criteria were applied. The studies included reports with confirmed positive effects (n = 46/99, 46.5 %) (P < 0.05), with positive effects (n = 49.5/99, 49.5 %), and with no effect (n = 4/99, 4 %); none of the studies reported adverse effects. There is an association between frequency of application and a decrease in healing time (P = 0.038); applying chitosan "every 48-72 hours" was the most recommended frequency (n = 10/19, 52.9 %). Chitosan, when applied to skin lesions on animals, produces positive effects on healing, potentially becoming a safe biomaterial for skin treatments in veterinary practice. As an initial protocol, we suggest applying chitosan every 48-72 hours for at least 2 weeks (7 applications).

Negative pressure wound therapy does not diminish efficacy of topical antibiotic powder in a preclinical contaminated wound model

AIMS

High-energy injuries can result in multiple complications, the most prevalent being infection. Vancomycin powder has been used with increasing frequency in orthopaedic trauma given its success in reducing infection following spine surgery. Additionally, large, traumatic injuries require wound coverage and management by dressings such as negative pressure wound therapy (NPWT). NPWT has been shown to decrease the ability of antibiotic cement beads to reduce infection, but its effect on antibiotic powder is not known. The goal of this study was to determine if NPWT reduces the efficacy of topically applied antibiotic powder.

METHODS

Complex musculoskeletal wounds were created in goats and inoculated with a strain of Staphylococcus aureus modified to emit light. Six hours after contaminating the wounds, imaging, irrigation, and debridement and treatment application were performed. Animals received either vancomycin powder with a wound pouch dressing or vancomycin powder with NPWT.

RESULTS

There were no differences in eradication of bacteria when vancomycin powder was used in combination with NPWT (4.5% of baseline) compared to vancomycin powder with a wound pouch dressing (1.7% of baseline) (p = 0.986), even though approximately 50% of the vancomycin was recovered in the NPWT exudate canister.

CONCLUSION

The antimicrobial efficacy of the vancomycin powder was not diminished by the application of NPWT. These topical and locally applied therapies are potentially effective tools that can provide quick, simple treatments to prevent infection while providing coverage. By reducing the occurrence of infection, the recovery is shortened, leading to an overall improvement in quality of life. Cite this article: Bone Joint Res 2021;10(2):149-155.

The Osteogenic Effect of Local Delivery of Vancomycin and Tobramycin on Bone Marrow Stromal Cells

Purpose

Bone tissue infections are a difficult problem in orthopedic surgery. Topical application of vancomycin and tobramycin powder has been proved to significantly reduce infection rates. However, the osteogenic effect of the topical application of these two antibiotics is unclear. In this study, the osteogenic effect of local delivery antibiotics on bone regeneration was investigated in vitro.

Methods

Bone marrow stromal cells (BMSCs) were incubated in the presence of vancomycin (14.28μg/mL), tobramycin (28.57μg/mL), or vancomycin combined with tobramycin (vancomycin 14.28μg/mL and tobramycin 28.57μg/mL). Cell viability, proliferation, and migration were analyzed. The alizarin red staining as well as the alkaline phosphatase staining was investigated. Then, the quantitative real-time (qRT)-PCR of osteogenic mRNA expression levels were also evaluated.

Results

The results showed that vancomycin combined with tobramycin has no adverse effect on the viability and proliferation of BMSCs. The topical application of vancomycin alone may interfere with the bone regenerative processes. However, the tobramycin can promote the osteogenic differentiation of BMSCs and also rescue the osteogenic potential of BMSCs inhibited by vancomycin both in vitro.

Conclusion

From this in vitro study, local application of vancomycin combined with tobramycin does not affect the osteogenic potential of BMSCs.

The Antimicrobial Effectiveness and Cytotoxicity of the Antibiotic-Loaded Chitosan: ECM Scaffolds

Background: The development of multifunctional wound dressings with the ability to control hemostasis, limit infection and promote rapid wound healing and constructive tissue remodeling has been a challenge for many years. In view of these challenges, a hybrid scaffold platform was developed that combined two different extracellular matrices (ECM): ECM from decellularized mammalian tissue and ECM (chitosan) from crustaceans. Both types of ECM have well established clinical benefits that support and promote wound healing and control hemostasis. This scaffold platform could also be augmented with antibiotics to provide bactericidal activity directly to the wound site. Methods: Four different scaffold formulations were developed containing chitosan supplemented with either 20% or 50% urinary bladder matrix (UBM) hydrogel or 1% (w/v) or 10% (w/v) UBM–ECM particulates. 100% chitosan scaffolds were used as controls. The scaffolds were augmented with either minocycline or rifampicin. Escherichia Coli and Staphylococcus Aureus were used to assesses antimicrobial efficacy and duration of activity, while neutral red uptake assays were performed to establish direct and indirect cytotoxicity. Results: Results showed that scaffold handling properties, scaffold integrity over time and the efficacy and release rate of loaded antibiotics could be modified by altering scaffold composition. Moreover, antibiotics were easily released from the scaffold and could remain effective for up to 24 h by modifying the scaffold composition. Variable results with cytotoxicity testing show that further work is required to optimize the scaffold formulations but these proof of principle experiments suggest that these scaffolds have potential as bioactive wound dressings.

A systematic review on current osteosynthesis-associated infection animal fracture models

Objective

Osteosynthesis-associated infection is a challenging complication post fracture fixation, burdening the patients and the orthopaedic surgeons alike. A clinically relevant animal model is critical in devising new therapeutic strategies. Our aim was to perform a systematic review to evaluate existing preclinical models and identify their applications in aspects of animal selection, bacterial induction, fracture fixation and complications.

Methods

A systematic literature research was conducted in PubMed and Embase up to February 2020. A total of 31 studies were included. Information on the animal, bacterial induction, fracture fixation, healing result and complications were extracted.

Results

Animals selected included murine (23), rabbit (6), ewe (1) and goat (1). Larger animals had enabled the use of human-sized implant, however small animals were more economical and easier in handling. Staphylococcus aureus (S. aureus) was the most frequently chosen bacteria for induction. Bacterial inoculation dose ranged from 10^2-8 ​CFU. Consistent and replicable infections were observed from 10⁴ ​CFU in general. Methods of inoculation included injections of bacterial suspension (20), placement of foreign objects (8) and pretreatment of implants with established biofilm (3). Intramedullary implants (13), plates and screws (18) were used in most models. Radiological (29) and histological evaluations (24) in osseous healing were performed. Complications such as instability of fracture fixation (7), unexpected surgical death (5), sepsis (1) and persistent lameness (1) were encountered.

Conclusion

The most common animal model is the S. aureus infected open fracture internally fixated. Replicable infections were mainly from 10⁴ ​CFU of bacteria. However, with the increase in antibiotic resistance, future directions should explore polymicrobial and antibiotic resistant strains, as these will no doubt play a major role in bone infection. Currently, there is also a lack of osteoporotic bone infection models and the pathophysiology is unexplored, which would be important with our aging population.

The translational potential of this article

This systematic review provides an updated overview and compares the currently available animal models of osteosynthesis-associated infections. A discussion on future research directions and suggestion of animal model settings were made, which is expected to advance the research in this field.