Biodegradable microspherical implants containing teicoplanin for the treatment of methicillin-resistant Staphylococcus aureus osteomyelitis

Validation of the Osteomyelitis Induced by Methicillin-Resistant Staphylococcus aureus (MRSA) on Rat Model with Calvaria Defect

BACKGROUND

Osteomyelitis resulting from bacterial strains, such as methicillin-resistant Staphylococcus aureus (MRSA) that are resistant to multiple drugs, brings further clinical challenges. There is currently no model of osteomyelitis induced by MRSA using rats with calvaria defects. So, We induced osteomyelitis in rat models with the calvaria bone defect.

METHODS

The rats were randomly divided into six groups according to inoculation dose levels, which ranged from 6 × 10⁰ to 6 × 10⁵ CFU/5 µl. Bone tissues were retrieved from all rats used in the study and assessed using histology, microbiology, and radiobiology 4 weeks after surgery to evaluate the relationship between inoculation dose and infectivity.

RESULTS

In Histological results, high levels of inflammatory responses, bone necrosis, and bacteria were observed in treatment groups G3 to G5. In IHC staining, high levels of cox-2 expression were observed in treatment groups G3. Microbiological observations also indicated that significantly higher numbers of CFUs were found in G3 to G5. In radiography results, the bone mineral density in G3 to G5 was significantly higher than in the control group, G1, and G2. Our results indicate that an inoculating dose of 6 × 10³ CFU/5 μl is sufficient to induce the development of osteomyelitis in rat models.

CONCLUSION

This study suggests that the minimum dose (6 × 10³ CFU/5 µl) can induce osteomyelitis in calvaria rat model. This can offer information and ability of more accurately modeling osteomyelitis and simulating the challenge of osteomyelitis treat.

Use of Antibiotic Loaded Biomaterials for the Management of Bone Prosthesis Infections: Rationale and Limits

BACKGROUND

Periprosthetic joint infection still represents a challenging issue for the orthopedic community. In the United States approximately a million joint arthroplasties are performed each year, with infection rates ranging from 1 to 2%: revisions has significant implications on health care costs and appropriate resource management. The use of locally applied antibiotics as a prophylaxis measure or as a component of the therapeutic approach in primary or revision surgery is finalized at eliminating any microorganism and strengthening the effectiveness of systemic therapy.

OBJECTIVE

The present review of clinical and preclinical in vivo studies tried to identify advantages and limitations of the materials used in the clinical orthopedic practice and discuss developed biomaterials, innovative therapeutic approaches or strategies to release antibiotics in the infected environment.

METHODS

A systematic search was carried out by two independent observers in two databases (www.pubmed.com and www.scopus.com) in order to identify pre-clinical and clinical reports in the last 10 years.

RESULTS

71 papers were recognized eligible: 15 articles were clinical studies and 56 in vivo studies.

CONCLUSION

Polymethylmethacrylate was the pioneer biomaterial used to manage infections after total joint replacement. Despite its widespread use, several issues still remain debated: the methods to combine materials and antibiotics, the choice of antibiotics, releasing kinetics and antibiotics efficacy. In the last years, the interest was directed towards the selection of different antibiotics, loaded in association with more than only one class and biomaterials with special focus on delivery systems as implant surface coatings, hydrogels, ceramics, micro-carriers, microspheres or nanoparticles.

Studies on the cytocompatibility, mechanical and antimicrobial properties of 3D printed poly(methyl methacrylate) beads

Osteomyelitis is typically a bacterial infection (usually from Staphylococcus) or, more rarely, a fungal infection of the bone. It can occur in any bone in the body, but it most often affects the long bones (leg and arm), vertebral (spine), and bones of the foot. Microbial success in osteomyelitis is due to their ability to form biofilms which inhibit the wound healing process and increases resistance to anti-infective agents. Also, biofilms do not allow easy penetration of antibiotics into their matrix making clinical treatment a challenge. The development of local antibiotic delivery systems that deliver high concentrations of antibiotics to the affected site is an emerging area of research with great potential. Standard treatment includes antibiotic therapy, either locally or systemically and refractory cases of osteomyelitis may lead to surgical intervention and a prolonged course of antibiotic treatment involving placement of antibiotic-doped beads or spacers within the wound site. There are disadvantages with this treatment modality including insufficient mixing of the antibiotic, lack of uniform bead size, resulting in lower antibiotic availability, and limitations on the antibiotics employed. Thus, a method is needed to address biofilm formations in the wound and on the surface of the surgical implants to prevent osteomyelitis. In this study, we show that all antibiotics studied were successfully doped into PMMA and antibiotic-doped 3D printed beads, disks, and filaments were easily printed. The growth inhibition capacity of the antibiotic-loaded PMMA 3D printed constructs was also demonstrated.

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Local antibiotic delivery systems that provide high antibiotic concentrations is an emerging area of research.

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A method for 3D printing antibiotic-doped PMMA was developed to prevent and remediate bone infection and biofilm formation.

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Antibiotics were doped into PMMA and antibiotic-doped 3D printed beads, disks, and filaments were successfully printed.

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Growth inhibition assays showed the efficacy of antibiotic-loaded PMMA 3D printed constructs in inhibiting bacterial growth.

Sustainable Release of Vancomycin from Silk Fibroin Nanoparticles for Treating Severe Bone Infection in Rat Tibia Osteomyelitis Model

The successful treatment of bone infections is a major challenge in the field of orthopedics. There are some common methods for treating bone infections, including systemic antibiotic administration, local nondegradable drug vehicles, and surgical debridement, and each of these approaches has advantages and disadvantages. In the present study, the antibiotic vancomycin (VANCO) was loaded in silk fibroin nanoparticles (SFNPs) and the complexes were then entrapped in silk scaffolds to form sustained drug delivery systems. The release kinetics of VANCO from SFNPs alone and when the SFNPs were entrapped in silk scaffolds were assessed at two different pH values, 4.5 and 7.4, that affected the release profiles of VANCO. Disk diffusion tests performed with pathogens causing osteomyelitis methicillin-resistant Staphylococcus aureus (MRSA) showed antibacterial activity of the released drug at two different pH values. Additionally, injection of 8 × 10⁶ CFU MRSA in rat's tibia induced severe osteomyelitis disease. Radiographic and histopathological analyses were performed to evaluate the effectiveness of treatment after 6 weeks. The VANCO-loaded silk fibroin nanoparticles entrapped in scaffolds reduced bone infections at the defected site with better outcomes than the other treatment groups. In conclusion, the delivery system with good biocompatibility and sustained release properties would be appropriate for further study in the context of osteomyelitis disease.

Synthesis, Properties, and In Vitro Hydrolytic Degradation of Poly(d,l-lactide-co-glycolide-co-ε-caprolactone)

Random copolymers of poly(d,l-lactide-co-glycolide-co-ε-caprolactone) (PLGC) were synthesized by the ring-opening polymerization of d,l-lactide (DLLA), glycolide (GA), andε-caprolactone (CL). The effects of CL on the copolymers were evaluated to prepare suitable copolymers with controlled properties. Our results showed that the CL content significantly influenced the thermal and mechanical properties of the copolymers and that the CL content in compositions could be altered to control properties of random copolymers. The in vitro hydrolytic degradation of the resulting implants showed that the degradation rate of PLGC was lower than that of PLGA, which could markedly reduce acidic degradation products. Finally, we demonstrated that higher CL contents in compositions slowed degradation rates.

Biomaterials approaches to treating implant-associated osteomyelitis

Orthopaedic devices are the most common surgical devices associated with implant-related infections and Staphylococcus aureus (S. aureus) is the most common causative pathogen in chronic bone infections (osteomyelitis). Treatment of these chronic bone infections often involves combinations of antibiotics given systemically and locally to the affected site via a biomaterial spacer. The gold standard biomaterial for local antibiotic delivery against osteomyelitis, poly(methyl methacrylate) (PMMA) bone cement, bears many limitations. Such shortcomings include limited antibiotic release, incompatibility with many antimicrobial agents, and the need for follow-up surgeries to remove the non-biodegradable cement before surgical reconstruction of the lost bone. Therefore, extensive research pursuits are targeting alternative, biodegradable materials to replace PMMA in osteomyelitis applications. Herein, we provide an overview of the primary clinical treatment strategies and emerging biodegradable materials that may be employed for management of implant-related osteomyelitis. We performed a systematic review of experimental biomaterials systems that have been evaluated for treating established S. aureus osteomyelitis in an animal model. Many experimental biomaterials were not decisively more efficacious for infection management than PMMA when delivering the same antibiotic. However, alternative biomaterials have reduced the number of follow-up surgeries, enhanced the antimicrobial efficacy by delivering agents that are incompatible with PMMA, and regenerated bone in an infected defect. Understanding the advantages, limitations, and potential for clinical translation of each biomaterial, along with the conditions under which it was evaluated (e.g. animal model), is critical for surgeons and researchers to navigate the plethora of options for local antibiotic delivery.

Nanostructured platforms for the sustained and local delivery of antibiotics in the treatment of osteomyelitis

This article provides a critical view of the current state of the development of nanoparticulate and other solid-state carriers for the local delivery of antibiotics in the treatment of osteomyelitis. Mentioned are the downsides of traditional means for treating bone infection, which involve systemic administration of antibiotics and surgical debridement, along with the rather imperfect local delivery options currently available in the clinic. Envisaged are more sophisticated carriers for the local and sustained delivery of antimicrobials, including bioresorbable polymeric, collagenous, liquid crystalline, and bioglass- and nanotube-based carriers, as well as those composed of calcium phosphate, the mineral component of bone and teeth. A special emphasis is placed on composite multifunctional antibiotic carriers of a nanoparticulate nature and on their ability to induce osteogenesis of hard tissues demineralized due to disease. An ideal carrier of this type would prevent the long-term, repetitive, and systemic administration of antibiotics and either minimize or completely eliminate the need for surgical debridement of necrotic tissue. Potential problems faced by even hypothetically "perfect" antibiotic delivery vehicles are mentioned too, including (i) intracellular bacterial colonies involved in recurrent, chronic osteomyelitis; (ii) the need for mechanical and release properties to be adjusted to the area of surgical placement; (iii) different environments in which in vitro and in vivo testings are carried out; (iv) unpredictable synergies between drug delivery system components; and (v) experimental sensitivity issues entailing the increasing subtlety of the design of nanoplatforms for the controlled delivery of therapeutics.

Vancomycin containing PLLA/β-TCP controls experimental osteomyelitis in vivo

Background

Implant-related osteomyelitis (IRO) is recently controlled with local antibiotic delivery systems to overcome conventional therapy disadvantages. In vivo evaluation of such systems is however too little.

Questions/purposes

We asked whether vancomycin (V)-containing poly-l-lactic acid/β-tricalcium phosphate (PLLA/β-TCP) composites control experimental IRO and promote bone healing in vivo.

Methods

Fifty-six rats were distributed to five groups in this longitudinal controlled study. Experimental IRO was established at tibiae by injecting methicillin-resistant Staphylococcus aureus (MRSA) suspensions with titanium particles in 32 rats. Vancomycin-free PLLA/β-TCP composites were implanted into the normal and infected tibiae, whereas V-PLLA/β-TCP composites and coated (C)-V-PLLA/β-TCP composites were implanted into IRO sites. Sham-operated tibiae established the control group. Radiological and histological scores were quantified with microbiological findings on weeks 1 and 6.

Results

IRO is resolved in the CV- and the V-PLLA/β-TCP groups but not in the PLLA/β-TCP group. MRSA was not isolated in the CV- and the V-PLLA/β-TCP groups at all times whereas the bacteria were present in the PLLA/β-TCP group. Radiological signs secondary to infection are improved from 10.9 ± 0.9 to 3.0 ± 0.3 in the V-PLLA/β-TCP group but remained constant in the PLLA/β-TCP group. Histology scores are improved from 24.7 ± 6.5 to 17.6 ± 4.8 and from 27.6 ± 7.9 to 32.4 ± 8.9 in the CV-PLLA/β-TCP and the V-PLLA/β-TCP groups, respectively. New bone was formed in all the PLLA/β-TCP group at weeks 1 and 6.

Conclusions

CV- and V-PLLA/β-TCP composites controlled experimental IRO and promoted bone healing.

Clinical relevance

CV- and V-PLLA/β-TCP composites have the potential of controlling experimental IRO and promoting bone healing.

A systematic review of animal models for Staphylococcus aureus osteomyelitis

Staphylococcus aureus (S. aureus) osteomyelitis is a significant complication for orthopaedic patients undergoing surgery, particularly with fracture fixation and arthroplasty. Given the difficulty in studying S. aureus infections in human subjects, animal models serve an integral role in exploring the pathogenesis of osteomyelitis, and aid in determining the efficacy of prophylactic and therapeutic treatments. Animal models should mimic the clinical scenarios seen in patients as closely as possible to permit the experimental results to be translated to the corresponding clinical care. To help understand existing animal models of S. aureus, we conducted a systematic search of PubMed and Ovid MEDLINE to identify in vivo animal experiments that have investigated the management of S. aureus osteomyelitis in the context of fractures and metallic implants. In this review, experimental studies are categorised by animal species and are further classified by the setting of the infection. Study methods are summarised and the relevant advantages and disadvantages of each species and model are discussed. While no ideal animal model exists, the understanding of a model's strengths and limitations should assist clinicians and researchers to appropriately select an animal model to translate the conclusions to the clinical setting.

Intra-discal vancomycin-loaded PLGA microsphere injection for MRSA discitis: an experimental study

OBJECTIVE

To prepare the vancomycin hydrochloride (VA)-loaded poly lactic acid-glycolic acid (PLGA) copolymer microsphere by the multiple emulsion method and evaluate its therapeutic effects on infective discitis.

METHODS

Firstly, the particle diameter distribution, shape, encapsulation efficiency, drug-loaded dosage and release curve of VA-PLGA microspheres were evaluated in vitro. Rabbits with methicillin-resistant Staphylococcus aureus infective discitis were treated with VA-PLGA intra-discal injection. Meanwhile, VA intravenous injection, blank PLGA microspheres intra-discal injection served as controls. Thirty days later, therapeutic effects were evaluated through X-ray radiophotography, histopathological and bacteriological examination.

RESULTS

Mean particle diameter was between 61.57 ± 4.37 and 67.45 ± 8.13 μm, and mean encapsulation efficiency was between 60.20 ± 1.61 and 75.27 ± 1.60 %m/m. In vitro release experiment showed that the release time was over 30 days. The result of in vivo experiment showed that inflammatory reaction in the VA-PLGA intra-discal injection group was milder than the intravenous injection group (P < 0.05), also with less inflammation. The bacterial count was also significantly lower (1.02 × 10(3) ± 1.22 × 10(3) CFU/g) than the intravenous injection group (7.51 × 10(4) ± 7.16 × 10(4) CFU/g) (P < 0.05). Besides these data, the amount used in VA-PLGA intra-discal injection group is about 20 mg, and that used in the intravenous injection group is about 2.4 g. So, we just use 1/120 of VA i.v. to obtain the better results with our microparticles.

CONCLUSION

Intra-discal injection with VA-PLGA sustained-release microspheres can use much less dosage, and effectively control and reduce infective discitis, and the therapeutic effect is superior to that of intravenous injection. A need for the clinical trials will be carried out in the near future.

Efficacy of moxifloxacin compared to teicoplanin in the treatment of implant-related chronic osteomyelitis in rats

Treatment of implant-related chronic osteomyelitis is often difficult and usually consists of implant removal, extensive surgical debridement, and prolonged antibiotic use. This study was performed to assess the efficacy of moxifloxacin compared to a glycopeptide, teicoplanin in chronic implant-related methicillin-sensitive Staphylococcus aureus (MSSA) osteomyelitis. The left femoral medullar cavities of 60 Wistar male rats were contaminated with 100 µl of 10(8) cfu/ml methicillin-sensitive S. aureus (ATCC 29213) and Kirschner wires were placed into the medulla of the femur. After 6 weeks, rats were randomly divided into five groups. In two groups, the Kirschner wires were removed. Experimental groups were as follows: group 1: contaminated, Kirschner wire inside, received teicoplanin; group 2: contaminated, Kirschner wire removed, received teicoplanin; group 3: contaminated, Kirschner wire inside, received moxifloxacin; group 4: contaminated, Kirschner wire removed, received moxifloxacin; group 5: contaminated, Kirschner wire inside, no antibiotics (control group). Groups 1 and 2 received teicoplanin (20 mg/kg once daily), whereas groups 3 and 4 received moxifloxacin (10 mg/kg twice daily) intraperitoneally for 28 days. At the end of the treatment, animals were sacrificed by inhalation anesthesia with ether and femora were retrieved and bacterial counts (cfu/g) were determined. Bacterial counts in all study groups were significantly reduced relative to the control. The decrease of bacterial counts was more prominent in group 4 compared to group 1 (p = 0.001) and group 2 (p = 0.003). Moxifloxacin therapy is an effective alternative to teicoplanin for chronic implant-related MSSA osteomyelitis.