Background. Exebacase, an antistaphylococcal lysin in Phase 3 of development as a treatment for S. aureus bacteremia/right-sided endocarditis has demonstrated antibiofilm activity in vitro and has previously been used as salvage therapy in four patients with relapsing multidrug-resistant (MDR) S. epidermidis knee prosthetic joint infection (PJI) using a procedure called LysinDAIR (administration of the lysin during the performance of an arthroscopic DAIR). Materials/methods. We performed a single center, exploratory, open-label prospective study using the LysinDAIR procedure in patients with chronic (inoculation >3 months prior to treatment) coagulase-negative staphylococci (CNS) PJI of the knee with two different clinical presentations and treatment paradigms. Cohort A: first episode of CNS knee PJI, for whom the LysinDAIR was followed by clindamycin + levofloxacin planned to be prescribed for three months and then stopped; and Cohort B: relapsing episodes of MDR CNS knee PJI for whom the LysinDAIR was followed by primary antimicrobial therapy for three months, followed by suppressive antimicrobial therapy (SAT). Exebacae susceptibility testing was performed before treatment for each patient. In agreement with the French Health authority, exebacase (2 to 3.5 total mg in 30–50 ml (∼0.067 – 0.075 mg/m) was administered directly into the joint during arthroscopy. Results. Eight patients were treated. Exebacase administration was well tolerated by all patients and no serious adverse drug reactions to exebacase were reported. In cohort A (n=4), patients had susceptible S. epidermidis PJI, a painful joint effusion without fistula and without loosening, and received three months of levofloxacin + clindamycin (one patient received an alternative regimen following antibiotic adverse events) and then antibiotics were stopped. During a follow-up of 14, 19, 26 and 36 months, no relapse, no recurrence of the joint effusion and no loosening occurred. In cohort B (n=4), patients had MDR CNS, clinical signs of septic arthritis with a joint effusion without fistula and without loosening and received daptomycin + linezolid or doxycycline. One patient died from COVID-19 at week 4. SAT (tedizolide, n=2; doxycycline, n=1) was then prescribed to other patients. One experienced an infection relapse involving S. caprae under tedizolid therapy at six months. The two other patients continue to do well under SAT 8 and 12 months after the LysinDAIR procedure. Conclusions. The LysinDAIR procedure is a minimally invasive procedure, which has been shown to be easy-to-perform, safe, and has the potential for use as initial treatment or salvage therapy in patients with CNS chronic knee PJI

Introduction. PJI is a devastating complication following total joint arthroplasty. In this study, we explore the efficacy of a bacteriophage-derived lysin, PlySs2, against in-vitro biofilm on titanium implant surfaces and in an acute in-vivo murine debridement antibiotic implant retention (DAIR) model of PJI. Methods. In-vitro: Xen 36 S. aureus biofilm was grown on Ti-6Al-4V mouse tibial implants for 1 day or 5 days and subsequently exposed to growth media, 1000× minimal inhibitory concentration (MIC) Vancomycin, or 5× MIC PlySs2. Implants were sonicated and analyzed for Colony Forming Units (CFU). In-vivo: A Ti-6Al-4V implant was inserted into the proximal tibia of C57BL/6J mice (n=21). All mice received 10. 4. CFU inoculation of Xen 36 S. aureus to the knee joint capsule and the infection was permitted 5 days to progress. On day 5 the mice were separated into three groups (n=7/group): (1) no further surgical intervention (control group), (2) irrigation and debridement (I&D) with saline, (3) I&D with 2mg/mL PlySs2. No implant-exchange was performed to mimic a debridement, antibiotic, and implant retention (DAIR) therapeutic strategy. All mice were sacrificed at day 10. Results. CFU counts for 1-day and 5-day in-vitro grown biofilm on implants demonstrate a >3log-fold reduction with PlySs2 compared to Vancomycin (p=0.01) with no significant difference between Vancomycin and control. In-vivo the addition of PlySs2 to Vancomycin treated mice reduces bacterial load in the periposthetic tissue and implant (p<0.05) with 5 days of treatment. Conclusion. PlySs2 5× MIC exhibits superior anti-microbial effect compared to Vancomycin on implants with 1-day and 5–5day biofilm maturities. The addition of PlySs2 to Vancomycin treatment of an acute established PJI further reduces tissue CFU and implants CFU. For any tables or figures, please contact the authors directly

Aim. Staphylococcus epidermidis (S. epidermidis) is one of the main pathogens responsible for bone and joint infections especially those involving prosthetic materials (PJI). Although less virulent than S. aureus, S. epidermidis is involved in chronic infections notably due to its ability to form biofilm. Moreover, it is frequently multiresistant to antibiotics. In this context, the development of additional or alternative antibacterial therapies targeting the biofilm is a priority. Method. The aim of this study was to evaluate in vitro the activity of phage lysin exebacase (CF-301) against biofilms formed by 19 S. epidermidis clinical strains responsible for PJI. We determined the remaining viable bacteria inside the biofilm (counting after serial dilution and plating) and the biomass (bacteria and extracellular matrix, using crystal violet staining) after 24h of exposition to exebacase at different concentrations, alone (0.05; 0.5; 5; 50 and 150 mg/L) or in combination (5, 50 and 150 mg/L) with antibiotics commonly used to treat multi-resistant S. epidermidis PJI (rifampin (1 mg/L), vancomycin (10mg/L) and daptomycin (10mg/L)). In this study, synergy was defined as a significantly higher effect of the association in comparison to the sum of the effect of each molecule. Results. Exebacase showed a dose-dependent reduction of biomass, ranging from 11 % at 0.5 mg/L to 66 % at 150 mg/L. Exebacase showed a significant bactericidal activity at 50 and 150 mg/l, with a mean decrease of the inoculum of 0.94 and 1.7 log, respectively. In addition, synergistic effects were observed in association with i) rifampin (1 mg/L) showing a mean decrease up to 84% of the biomass and 3.5 log CFU at 150 mg/L of exebacase, ii) vancomycin (10 mg/L) showing a mean decrease up to 81% of the biomass and 2.82 log CFU at 150 mg/L of exebacase, iii) and daptomycin (10 mg/L) showing a mean decrease up to 85% of the biomass and 3.1 log CFU at 150 mg/L of exebacase. Conclusions. Exebacase showed, in vitro, synergistic activity with antibiotics against S. epidermidis biofilms. It is a promising adjuvant therapy to rifampin, vancomycin and daptomycin in the context of PJI. Further studies are needed, in vitro to understand the mechanism of action on S. epidermidis biofilm and the heterogeneity of strain behaviour and in vivo to confirm the present data

Aims

Biofilm formation is one of the primary reasons for the difficulty in treating implant-related infections (IRIs). Focused high-energy extracorporeal shockwave therapy (fhESWT), which is a treatment modality for fracture nonunions, has been shown to have a direct antibacterial effect on planktonic bacteria. The goal of the present study was to investigate the effect of fhESWT on Staphylococcus aureus biofilms in vitro in the presence and absence of antibiotic agents.