Treatment of periprosthetic joint infections guided by minimum biofilm eradication concentration (MBEC) in addition to minimum inhibitory concentration (MIC): protocol for a prospective randomised clinical trial

Safety Profile of Seven-Day Intra-articular Antibiotic Irrigation for the Treatment of Chronic Periprosthetic Joint Infection: A Prospective Randomized Phase II Comparative Study

BACKGROUND

Systemic intravenous antimicrobials yield poor outcomes during treatment of periprosthetic joint infection due to the inability to obtain minimum biofilm eradication concentrations. This study evaluated the safety of a novel method of optimized local delivery of intra-articular antibiotics (IAAs).

METHODS

This was a Phase II, multicenter, prospective randomized trial evaluating safety of a rapid (seven-day) two-stage exchange arthroplasty with IAA irrigation compared to standard two-stage exchange. The Experimental Group received irrigation using 80 mg tobramycin daily with a 2-hour soak, followed by hourly irrigation using 125 mg vancomycin with a 30-minute soak via an intramedullary irrigation device. The Control Group received an antibiotic-loaded cement spacer with vancomycin (average 8.4 g) and tobramycin (average 7.1 g, total 16 g antibiotics). Both groups received 12 weeks of systemic antibiotics following Stage 2. Safety measures included adverse events, peak vancomycin/tobramycin serum concentrations (Experimental Group), blood transfusion, and mortality. There were thirty-seven patients randomized to the Experimental Group and 39 to control. There was no difference in baseline demographics or comorbidities.

RESULTS

There were no antibiotic medication-related adverse events and 2 serious adverse events related to antibiotic instillation. Of 188 vancomycin peak measurements, 69% had detectable serum level concentrations, with all concentrations well below the maximum acceptable trough threshold of 20 μg/mL. Of the 103 tobramycin peak measurements, 45% had detectable levels, with all below the maximum acceptable peak threshold of 18 to 24 μg/mL. There was no difference in blood transfused per subject (Experimental: 655 mL versus Control: 792 mL; P = .4188). There were two (2) deaths in the Experimental Group and four (4) in the control.

CONCLUSIONS

The use of IAA is safe with minimal systemic antibiotic exposure. There was no difference in the rates or severity of serious adverse events between groups. Further research is being conducted to examine treatment efficacy.

Investigating the translational value of Periprosthetic Joint Infection (PJI) models to determine the risk and severity of Staphylococcal biofilms

With the advent of antibiotic-eluting polymeric materials for targeting recalcitrant infections, using preclinical models to study biofilm is crucial for improving the treatment efficacy in periprosthetic joint infections. The stratification of risk and severity of infections is needed to develop an effective clinical dosing framework with better outcomes. Here, using in-vivo and in-vitro implant-associated infection models, we demonstrate that methicillin-sensitive and resistant Staphylococcus aureus (MSSA and MRSA) have model-dependent distinct implant and peri-implant tissue colonization patterns. The maturity of biofilms and the location (implant vs tissue) were found to influence the antibiotic susceptibility evolution profiles of MSSA and MRSA and the models could capture the differing host-microbe interactions in vivo. Gene expression studies revealed the molecular heterogeneity of colonizing bacterial populations. The comparison and stratification of the risk and severity of infection across different preclinical models provided in this study can guide clinical dosing to effectively prevent or treat PJI.

Antibiotic-Loaded Ultrahigh Molecular Weight Polyethylenes

The occurrence of periprosthetic joint infections (PJI) after total joint replacement constitutes a great burden for the patients and the healthcare system. Antibiotic-loaded polymethylmethacrylate (PMMA) bone cement is often used in temporary spacers during antibiotic treatment. PMMA is not a load-bearing solution and needs to be replaced by a functional implant. Elution from the ultrahigh molecular weight polyethylene (UHMWPE) bearing surface for drug delivery can combine functionality with the release of clinically relevant doses of antibiotics. In this study, the feasibility of incorporating a range of antibiotics into UHMWPE is investigated. Drug stability is assessed by thermo-gravimetric analysis and nuclear magnetic resonance spectroscopy. Drug-loaded UHMWPEs are prepared by compression molding, using eight antibiotics at different loading. The predicted intra-articular concentrations of drugs eluted from UHMWPE are above minimum inhibitory concentration for at least 3 weeks against Staphylococci, which are the major causative bacteria for PJI. The antibacterial efficacy is confirmed for samples covering 2% of a representative knee implant in vitro over 72 h, showing that a small fraction of the implant surface loaded with antibiotics may be sufficient against Staphylococci.

Biofilm antimicrobial susceptibility testing: where are we and where could we be going?

Our knowledge about the fundamental aspects of biofilm biology, including the mechanisms behind the reduced antimicrobial susceptibility of biofilms, has increased drastically over the last decades. However, this knowledge has so far not been translated into major changes in clinical practice. While the biofilm concept is increasingly on the radar of clinical microbiologists, physicians, and healthcare professionals in general, the standardized tools to study biofilms in the clinical microbiology laboratory are still lacking; one area in which this is particularly obvious is that of antimicrobial susceptibility testing (AST). It is generally accepted that the biofilm lifestyle has a tremendous impact on antibiotic susceptibility, yet AST is typically still carried out with planktonic cells. On top of that, the microenvironment at the site of infection is an important driver for microbial physiology and hence susceptibility; but this is poorly reflected in current AST methods. The goal of this review is to provide an overview of the state of the art concerning biofilm AST and highlight the knowledge gaps in this area. Subsequently, potential ways to improve biofilm-based AST will be discussed. Finally, bottlenecks currently preventing the use of biofilm AST in clinical practice, as well as the steps needed to get past these bottlenecks, will be discussed.