Experimental reproduction of periprosthetic joint infection: Developing a representative animal model

Development of an innovative in vivo model of PJI treated with DAIR

Introduction

Prosthetic Joint Infection (PJI) are catastrophic complications of joint replacement. Debridement, implant retention, and antibiotic therapy (DAIR) is the usual strategy in acute infections but fails in 45% of MRSA infections. We describe the development of a model of infected arthroplasty in rabbits, treated with debridement and a course of vancomycin with clinically relevant dosage.

Materials and methods

A total of 15 rabbits were assigned to three groups: vancomycin pharmacokinetics (A), infection (B), and DAIR (C). All groups received a tibial arthroplasty using a Ti-6Al-4V implant. Groups B and C were infected per-operatively with a 5.5 log10 MRSA inoculum. After 1 week, groups C infected knees were surgically debrided. Groups A and C received 1 week of vancomycin. Pharmacokinetic profiles were obtained in group A following 1st and 5th injections. Animals were euthanized 2 weeks after the arthroplasty. Implants and tissue samples were processed for bacterial counts and histology.

Results

Average vancomycin AUC_{0–12 h} were 213.0 mg*h/L (1st injection) and 207.8 mg*h/L (5th injection), reaching clinical targets. All inoculated animals were infected. CFUs were reproducible in groups B. A sharp decrease in CFU was observed in groups C. Serum markers and leukocytes counts increased significantly in infected groups.

Conclusion

We developed a reproducible rabbit model of PJI treated with DAIR, using vancomycin at clinically relevant concentrations.

Determination of the Elution Capacity of Dalbavancin in Bone Cements: New Alternative for the Treatment of Biofilm-Related Peri-Prosthetic Joint Infections Based on an In Vitro Study

Antibiotic-loaded bone cement is the most widely used approach for the treatment of biofilm-induced septic sequelae in orthopedic surgery. Dalbavancin is a lipoglycopeptide that acts against Gram-positive bacteria and has a long half-life, so we aimed to assess whether it could be a new alternative drug in antibiotic-loaded bone cement for the treatment of periprosthetic joint infections. We assessed the elution capacity of dalbavancin and compared it with that of vancomycin in bone cement. Palacos®R (Heraeus Medical GmbH, Wehrheim, Germany) bone cement was manually mixed with each of the antibiotics studied at 2.5% and 5%. Three cylinders were obtained from each of the mixtures; these were weighed and incubated in 5 mL phosphate-buffered saline at 37°C under shaking for 1 h, 2 h, 4 h, 8 h, 24 h, 48 h, 168 h, and 336 h. PBS was replenished at each time point. The samples were analyzed using high-performance liquid chromatography (vancomycin) and mass cytometry (dalbavancin). Elution was higher than the minimum inhibitory concentration (MIC)90 for both antibiotics after 14 days of study. The release of vancomycin at 14 days was higher than of dalbavancin at each concentration tested (p = 0.05, both). However, the cumulative release of 5% dalbavancin was similar to that of 2.5% vancomycin (p = 0.513). The elution capacity of dalbavancin reached a cumulative concentration similar to that of vancomycin. Moreover, considering that the MIC90 of dalbavancin is one third that of vancomycin (0.06 mg/L and 2 mg/L, respectively) and given the long half-life of dalbavancin, it may be a new alternative for the treatment of biofilm-related periprosthetic infections when loaded in bone cement.

The Current Knowledge on the Pathogenesis of Tissue and Medical Device-Related Biofilm Infections

Biofilm is the trigger for the majority of infections caused by the ability of microorganisms to adhere to tissues and medical devices. Microbial cells embedded in the biofilm matrix are highly tolerant to antimicrobials and escape the host immune system. Thus, the refractory nature of biofilm-related infections (BRIs) still represents a great challenge for physicians and is a serious health threat worldwide. Despite its importance, the microbiological diagnosis of a BRI is still difficult and not routinely assessed in clinical microbiology. Moreover, biofilm bacteria are up to 100–1000 times less susceptible to antibiotics than their planktonic counterpart. Consequently, conventional antibiograms might not be representative of the bacterial drug susceptibility in vivo. The timely recognition of a BRI is a crucial step to directing the most appropriate biofilm-targeted antimicrobial strategy.

[Experimental study of silkworm larvae plasma colorimetry based on immune cascade reaction in accurate diagnosis of periprosthetic joint infection]

OBJECTIVE

To investigate the diagnostic efficacy of silkworm larvae plasma (SLP) colorimetry in the accurate diagnosis of periprosthetic joint infection (PJI).

METHODS

Ninety healthy male New Zealand white rabbits were used for knee arthroplasty with Swanson prosthesis. Then they were randomly divided into 3 groups according to different pathogenic bacteria: group A ( Staphylococcus aureus group), group B ( Staphylococcus epidermidis group) and group C ( Escherichia coli group), with 30 rats in each group. The PJI model was prepared by knee injection with 1 mL of pathogenic bacteria of different concentrations. Samples were taken before inoculation and at 7, 14, and 21 days after inoculation, and based on the 2018 PJI Philadelphia International Consensus diagnostic criteria, the success rate of modeling among 3 groups of experimental animals was determined. The sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic efficiency of SLP colorimetry were calculated.

RESULTS

At 21 days after inoculation, 26, 18, and 23 rabbits in groups A, B, and C were diagnosed as infection, respectively. The success rates of modeling were 86.7%, 60.0%, and 76.7%, respectively, showing no significant difference among the 3 groups ( χ ²=5.724, P=0.073). The results of PJI colorimetry showed that 1 false-positive animal (specificity 75.0%) appeared in group A at 7 days, and the specificity of SLP increased to 100.0% over time (on 14 and 21 days); on 14 and 21 days, another animal appeared false-negative results (sensitivity decreased from 100.0% to 96.2%). One false-positive animal appeared in group B at 7 days (specificity 91.7%), the specificity returned to 100.0% over time; 1 and 4 false-negative animals appeared at 14 and 21 days, respectively (sensitivity 94.4% and 83.3%, respectively). In group C, two false-positive animals (specificity 71.4%) were found at 7 days, and then returned to 100.0%. The diagnostic efficiency of groups A and C was very high at 21 days (96.7% and 100.0%), even for the low virulence Staphylococcus epidermidis in group B, the diagnostic efficiency could be maintained at 90.0% (21 days), and the overall diagnostic efficiency was very good (95.6%).

CONCLUSION

SLP colorimetry has high sensitivity, specificity, and diagnostic efficiency in the diagnosis of PJI, which is a potential diagnostic method.

The tale of microencapsulated rifampicin: is it useful for the treatment of periprosthetic joint infection?

Purpose

Microencapsulation techniques have allowed the addition of rifampicin to bone cement, but its in vivo efficacy has not been proven. The aim of our study is to determine the superiority of cement containing gentamicin and rifampicin microcapsules in the treatment of PJI versus cement exclusively containing gentamicin.

Methods

An S. aureus PJI was induced in 15 NZW rabbits. A week after inoculation, the first stage of replacement was carried out, and the animals were divided into two groups: group R received a spacer containing gentamicin and rifampicin microcapsules, and group C received a spacer containing gentamicin. Intra-articular release curve of rifampicin and infection and toxicity markers were monitored for four weeks post-operatively, when microbiological analysis was performed.

Results

The microbiological cultures showed a significantly lower growth of S. aureus in soft tissue (2.3·10⁴ vs 0; p = 0.01) and bone (5.7·10² vs 0; p = 0.03) in the group with rifampicin microcapsules. No differences were found in systemic toxicity markers. Rifampicin release from the cement spacer showed higher concentrations than the staphylococcal MIC throughout the analysis.

Conclusion

The in vivo analyses demonstrated the superiority of cement containing gentamicin and rifampicin microcapsules versus the isolated use of gentamicin in the treatment of PJI in the rabbit model without serious side effects due to the systemic absorption of rifampicin. Given the increasing incidence of staphylococci-related PJI, the development of new strategies for intra-articular administration of rifampicin for its treatment has a high clinical impact.

Recent Advances in the Evaluation of Antimicrobial Materials for Resolution of Orthopedic Implant-Associated Infections In Vivo

While orthopedic implant-associated infections are rare, revision surgeries resulting from infections incur considerable healthcare costs and represent a substantial research area clinically, in academia, and in industry. In recent years, there have been numerous advances in the development of antimicrobial strategies for the prevention and treatment of orthopedic implant-associated infections which offer promise to improve the limitations of existing delivery systems through local and controlled release of antimicrobial agents. Prior to translation to in vivo orthopedic implant-associated infection models, the properties (e.g., degradation, antimicrobial activity, biocompatibility) of the antimicrobial materials can be evaluated in subcutaneous implant in vivo models. The antimicrobial materials are then incorporated into in vivo implant models to evaluate the efficacy of using the material to prevent or treat implant-associated infections. Recent technological advances such as 3D-printing, bacterial genomic sequencing, and real-time in vivo imaging of infection and inflammation have contributed to the development of preclinical implant-associated infection models that more effectively recapitulate the clinical presentation of infections and improve the evaluation of antimicrobial materials. This Review highlights the advantages and limitations of antimicrobial materials used in conjunction with orthopedic implants for the prevention and treatment of orthopedic implant-associated infections and discusses how these materials are evaluated in preclinical in vivo models. This analysis serves as a resource for biomaterial researchers in the selection of an appropriate orthopedic implant-associated infection preclinical model to evaluate novel antimicrobial materials.