Citations

ABSTRACT Biofilm‐associated staphylococcal infections remain exceptionally difficult to treat due to the presence of resilient staphylococcal biofilms and the limited effectiveness of currently available antibiotics. To combat persistent infections, providers are often forced to use prolonged courses of combination antimicrobial therapies that have significant toxicities with limited effectiveness, leading to increased hospital stays, substantial health care costs and a rise in patient morbidity and mortality. Staphylococcus aureus is a dominant cause of recalcitrant biofilms, for which novel non‐antibiotic therapeutics are critically needed. Lysins, a class of protein‐based antimicrobials, rapidly kill staphylococci, exhibit potent anti‐biofilm activity, have a low propensity of resistance development and synergy with antibiotics. To address this unmet need, we evaluate an extracellular vesicle (EV)‐based delivery platform for the engineered anti‐staphylococcal lysin LYSG101, designed to improve stability and localization at sites of infection. Initial proof‐of‐concept work is provided here, demonstrating that human serum‐derived EVs can be loaded with LYSG101 to exert a potent in vitro antimicrobial effect against both planktonic and biofilm forms of S. aureus . EV‐mediated delivery achieved activity equivalent to free lysin, with additional translational advantages including stability and the potential for sustained intra‐articular retention. This work supports further development of the EV‐mediated lysin delivery as a broadly applicable antimicrobial platform, with potential future applications in biofilm‐associated infections, including prosthetic joint infection (PJI).

➢ Periprosthetic joint infection (PJI) remains the most common cause of failure after total joint arthroplasty, with current standard therapies associated with failure rates between 10% and 30%. ➢ The 2025 International Consensus Meeting in Istanbul, Türkiye, highlighted the potential benefits of bacteriophage (phage) therapy in managing PJI. ➢ One of the barriers to integrating phage therapy into standard clinical PJI care is the knowledge gap between preclinical research and clinical practice. ➢ This Expert Review summarizes the key therapeutic advantages of using phages as an adjuvant therapeutic platform for PJI. It also highlights the current challenges that are continuing to limit the integration of phages into standard PJI care.

Abstract Background Upper-airway and respiratory conditions impose a large and growing global burden, yet there is no standardized way to assess whether a nasal microbiome is “healthy”. Currently, monitoring remains reactive, beginning only after symptoms manifest. The nasal cavity is well suited to proactive monitoring: it shapes respiratory health and pathogen colonization resistance, and can be sampled non-invasively and repeatedly. To address this gap, we introduce the Nasal Microbiome Wellness Index (NMWI), a disease-agnostic, continuous score of nasal microbiome health derived from LASSO-penalized logistic regression. Rather than counting taxa, it learns which taxa (and in what balance) characterize a healthy nose and returns the predicted log-odds that a profile resembles a healthy state. The index was trained on 1654 nasal 16S rRNA gene amplicon sequencing samples (589 healthy, 1065 non-healthy) pooled from 27 publicly available studies, uniformly reprocessed through a single computational pipeline. Results The NMWI comprises an interpretable signature of 24 taxa whose combined relative abundances determine the health-associated log-odds. Health-associated genera such as Corynebacterium and Cutibacterium raised the score, while dysbiosis-associated genera such as Pseudomonas and Escherichia – Shigella lowered it. The NMWI substantially outperformed the Shannon, Simpson, and Chao1 diversity indices, which showed negligible, directionally inconsistent separation between healthy and non-healthy samples (|Cliff’s δ | = 0.01–0.20), whereas the NMWI produced large, consistent separation ( δ = 0.65). It achieved a balanced accuracy of 74.37% on the training data (resubstitution estimate), and 73.43% under repeated 10-times 10-fold cross-validation. Performance remained stable at mean balanced accuracy of 73.82% under a leave-one-study-out framework, reflecting cross-study generalizability. In independent external cohorts, the balanced accuracy was 71.49%, and leave-one-disease-out analysis (in which each disease condition was withheld from training) showed a mean balanced accuracy of 63.92% across unseen conditions, consistent with a disease-agnostic design. The index also generalized across heterogeneous datasets spanning multiple 16S rRNA gene hypervariable regions—to our knowledge the first demonstration of such cross-study, cross-region transferability for the nasal cavity. Conclusions The NMWI distills a complex nasal microbial profile into a single interpretable score computed directly from the 16S rRNA gene data that dominate existing nasal research, making it immediately applicable to published and future datasets without re-sequencing. By replacing descriptive, diversity-based comparison with a quantitative standard, it offers a reproducible, open-source foundation for cross-study benchmarking, individual-level phenotyping, and longitudinal respiratory wellness monitoring.

Abstract Background Dalbavancin is increasingly used off-label for chronic Gram-positive bone and joint infections (BJIs) requiring prolonged antimicrobial therapy, but optimal dosing strategies and the role of therapeutic drug monitoring (TDM) remain unclear. We evaluated the real-world implementation of a proactive TDM-guided dalbavancin workflow within an outpatient parenteral antimicrobial therapy (OPAT) programme. Methods Single-centre prospective observational implementation study including adult patients with BJIs consecutively treated with dalbavancin in OPAT service between July 2022 and August 2025. A multidisciplinary team developed a workflow incorporating TDM-guided pharmacokinetic modelling to individualize dosing intervals after fixed initial administrations (Days 1, 8 and 43). Target Cmin concentrations were ≥8 mg/L, later increased to ≥15 mg/L after European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoint revision. Primary outcomes included implementation metrics (feasibility, fidelity and appropriateness). Secondary outcomes were clinical effectiveness, safety and overall workflow success. Results The workflow was applied to 101 patients accounting for 418 TDM-guided dalbavancin administrations (feasibility). Three patient-driven treatment discontinuations were observed (3/101, 3.0%), and scheduled administrations occurred within the predefined time window in 335/418 (83.5%) of cases (fidelity). Pharmacological target attainment was achieved in 285/342 (89.6%) of administrations without dosing delays (appropriateness). Clinical effectiveness was achieved in 55/73 (75.3%) patients completing therapy, with 28/101 (28%) still on treatment. Adverse events–related discontinuation occurred in 3/101 (3%) patients. Overall workflow success was observed in 74/101 (73.2%) patients. Conclusions A multidisciplinary TDM-guided dalbavancin workflow within an OPAT programme was feasible and safe, achieving high target attainment and favourable clinical outcomes. This approach supports individualized long-acting dalbavancin therapy for complex chronic BJIs.

Background: Prosthetic joint infections (PJIs) pose a significant treatment challenge due to biofilm-associated resistance, which limits antibiotic effectiveness. Bacteriophages, naturally occurring viruses that selectively infect and lyse bacteria, can disrupt biofilms, potentially enhancing antibiotic activity. We present the case of a male in his 70s with a history of total hip arthroplasty in 1973 who developed a chronic methicillin-susceptible Staphylococcus aureus (MSSA) PJI. Despite eight surgical interventions and multiple courses of suppressive antibiotics, the infection persisted, necessitating the use of bacteriophage therapy. Methods: The patient's MSSA isolate was sent to a bacteriophage laboratory in Quebec, which identified effective bacteriophages, and a two-bacteriophage cocktail was selected. Following approval by Health Canada and the University of Calgary (REB23-1733), bacteriophages were administered during a planned incision and drainage (I&D). Locally, bacteriophage was applied topically into the hip, followed by 2 weeks of twice-daily intravenous bacteriophage therapy with standard-of-care intravenous antibiotics. Results: Therapy was well tolerated except for initial mild rigors. Now, 24 weeks after bacteriophage administration, there is cessation of pain, normalization of inflammatory markers, and significant improvement in quality of life while continuing on suppressive antibiotics. Conclusions: Bacteriophage therapy was safe in our case, and emerging evidence is promising for its use in PJIs. However, regulatory hurdles, cost, and lack of standardized protocols currently limit its use. Classified as experimental therapy in Canada, bacteriophage use is restricted to clinical trials. This case underscores the potential for broader adoption of bacteriophage therapy in managing PJIs across Canada.

Abstract Background Native joint septic arthritis (NJSA) is a serious musculoskeletal infection requiring timely surgical intervention to prevent long-term morbidity. Although current guidelines recommend early surgical debridement, supporting data, particularly on long-term outcomes, remain scarce. Given this, we evaluated the association between surgical timing and 1-year clinical outcomes using the Desirability of Outcome Ranking (DOOR) framework, applied for the first time in NJSA.Table 1.Desirability of Outcome Ranking (DOOR) ordinal scaleTable 2.Baseline demographic, clinical characteristics, and treatment outcomes Methods We conducted a retrospective multicenter cohort study of adults (≥18 years) with NJSA who underwent surgery across Mayo Clinic campuses between 2012 and 2021. Clinical outcomes at one year were assessed using a 9-level DOOR scale, incorporating survival, treatment failure (relapse, reinfection, readmission, or significant surgical events), and joint recovery (full vs qualified) (Table 1). Time to surgery from hospital admission was analyzed both as a continuous variable and as categories: < 1, 1–2, or ≥3 days.Table 3.Associations between duration and outcomesFigure 1.Association Between Time to Surgery and DOOR Scores in Native Joint Septic Arthritis.A) Distribution of Modified DOOR Scores by Surgical Timing. B) Modeled Probability of DOOR Scores by Time to Surgery. Results Among 268 patients (median age 62 years, 61% male), 30% underwent surgery < 1 day from admission, 47% within 1–2 days, and 24% at ≥3 days. At 1 year, 57% achieved full recovery without unfavorable events (DOOR score 1), while treatment failure occurred in 34% (Table 2). In unadjusted analyses, longer surgical delay was significantly associated with higher DOOR scores (per IQR increase [from 0 to 2 days], OR: 1.5; 95% CI: 1.0–2.1; p = 0.026) and with increased 1-year mortality (HR: 1.7; 95% CI: 1.1–2.6; p = 0.019) and treatment failure (HR: 1.5; 95% CI: 1.1–2.0; p = 0.007). Similar results were obtained when delay was used as a categorical 3-level variable, with the highest risk observed in patients undergoing surgery after ≥3 days. After adjusting for age and Charlson index, only the association between surgical delay and treatment failure remained statistically significant (HR: 1.5; 95% CI, 1.1–2.0; p=0.016) (Table 3, Figure 1). Conclusion Delayed surgical intervention for management of NJSA was independently associated with higher risk of treatment failure at 1 year. These findings reinforce current guideline recommendations for timely operative management and further underscore the potential of the DOOR framework to capture clinically meaningful, multidimensional outcomes in NJSA. Disclosures All Authors: No reported disclosures

Background: Phages are being assessed for treatment of periprosthetic joint infection (PJI). Staphylococci are the most common cause of PJI. Phages are traditionally considered to be strain-specific and restricted to specific species. We aimed to assess the in vitro activity of a collection of staphylococcal phages against a selection of clinical Staphylococcus isolates recovered from PJI over a 20-year period. Methods: The activity of 37 staphylococcal phages was evaluated against 204 staphylococcal isolates, including 102 Staphylococcus aureus, 81 Staphylococcus epidermidis , and 21 Staphylococcus lugdunensis , using a tetrazolium dye–based metabolic assay. Standardized inocula of bacteria and phage were incubated over 48 hours. Growth inhibition ≥8 hours was considered indicative of phage activity. Results: A total of 7,548 phage-isolate pairs were assessed. Overall, 31 of 37 phages had activity against at least 1 isolate. The most broadly active phage showed activity against 50 of 195 isolates (26%) tested. Twenty-three phages showed cross-species activity, with 11 phages active against all 3 Staphylococcus species, and 12 phages active against 2 species. Of all S. aureus isolates tested, 61% were susceptible to at least 1 phage, while 31% and 76% of S. epidermidis and S. lugdunensis isolates were susceptible to at least 1 phage, respectively. Conclusions: This is the largest library of phages evaluated against staphylococci from PJI. Results show that staphylococcal phages can have cross-species activity, suggesting that phage libraries may offer cross-species coverage of clinically encountered staphylococcal isolates from PJI. Level of Evidence: Level V . Mechanism-based reasoning. See Instructions for Authors for a complete description of levels of evidence.

Abstract Background Although recent guidance recommends early surgical debridement for native joint septic arthritis (NJSA), supporting data, particularly on long-term outcomes, remains scarce. Methods We conducted a retrospective multicenter cohort study of adults (≥18 years) with NJSA who underwent surgery across Mayo Clinic campuses between 2012 and 2021. Clinical outcomes at 1 year were assessed using a 9-level Desirability of Outcome Ranking (DOOR) scale, incorporating survival, treatment failure (relapse, reinfection, readmission, or significant surgical events), and joint recovery. Time to surgery from hospital admission was analyzed both as a continuous variable and as categories: < 1, 1–2, or ≥3 days. Results Among 268 patients, 30% underwent surgery <1 day from admission, 47% in 1–2 days, and 24% in ≥3 days. At 1 year, 57% achieved full recovery without unfavorable events (DOOR score 1), while treatment failure occurred in 34%. In unadjusted analyses, longer surgical delay was significantly associated with higher (worse) DOOR scores (per IQR increase [from 0 to 2 days], OR: 1.5; 95% CI: 1.0–2.1; P = .026), increased 1-year mortality (HR: 1.7; 95% CI: 1.1–2.6; P = .019) and treatment failure (HR: 1.5; 95% CI: 1.1–2.0; P = .007). Even after adjusting for age and Charlson comorbidity index, the association between surgical delay and treatment failure remained significant (HR: 1.5; 95% CI, 1.1–2.0; P = .016). Conclusions The finding that delayed surgical intervention is associated with an increased risk of treatment failure reinforces current expert recommendations for timely surgical management in NJSA.

We describe the first use of phage therapy in Canada for the treatment of a life-threatening periprosthetic joint infection (PJI), with successful outcome. PJI is a devastating complication of joint replacement surgery, with high morbidity and mortality. Our patient presented with early sepsis from a chronic recalcitrant multidrug-resistant (MDR) Staphylococcus epidermidis hip PJI which had repeatedly failed standard therapy. She had previously undergone 10 operations of the right hip, and only three weeks after completing a prolonged course of daptomycin following her most recent hip revision, she developed a draining sinus tract. Given the high burden of disease, inability to achieve surgical source control, and lack of antibiotic treatment options for long-term suppressive therapy, bacteriophage (phage) therapy was pursued. The patient underwent irrigation and debridement with complex flap reconstruction: intraoperative tissue cultures again yielded MDR S. epidermidis. We developed a novel phage therapy protocol for this patient, with twice daily, intra-articular and intravenous (7 × 109 PFU/dose) phage delivery over a planned 14-day course. Complete healing of the wound with cessation of drainage occurred within one month after treatment. A marked improvement in right hip pain and mobility occurred within three months after treatment. Twelve months following phage treatment, there is normalization of serum inflammatory markers with diminished pain, increased mobility, and no recurrent surgery. Our patient continues to improve and is currently living independently at home, with sustained clinical control of infection.

Bacteriophage (phage) therapy has emerged as a promising solution to combat the growing crisis of multidrug-resistant (MDR) infections. There are several international centers actively engaged in implementation of phage therapy, and recent case series have reported encouraging success rates in patients receiving personalized, compassionate phage therapy for difficult-to-treat infections. Nonetheless, substantial hurdles remain in the way of more widespread adoption and more consistent success. This Review offers a comprehensive overview of current phage therapy technologies and therapeutic approaches. We first delineate the common steps in phage therapy development, from phage bank establishment to clinical administration, and examine the spectrum of therapeutic approaches, from personalized to fixed phage cocktails. Using the framework of a conventional drug development pipeline, we then identify critical knowledge gaps in areas such as cocktail design, formulation, pharmacology, and clinical trial design. We conclude that, while phage therapy holds promise, a structured drug development pipeline and sustained government support are crucial for widespread adoption of phage therapy for MDR infections.