Patel, Robin

Introduction Infection following extensor mechanism reconstruction with Marlex mesh is a devastating and limb threatening complication. The purpose of this study was to evaluate whether vancomycin-loaded mesh reduced staphylococcal infection in a murine extensor mechanism reconstruction model with Marlex mesh. Methods Mouse-sized, eight-layer Marlex mesh constructs were fabricated to simulate clinical reconstruction and soaked in a vancomycin solution (50 mg/mL) for in vitro and in vivo testing. Three methicillin-resistant clinical isolates from human periprosthetic knee infections were evaluated: Staphylococcus aureus, Staphylococcus epidermidis , and Staphylococcus lugdunensis. In vitro testing assessed vancomycin loading, mechanical properties, antibacterial activity, and early biofilm inhibition. For in vivo experiments, plain or vancomycin-loaded Marlex meshes were implanted into the murine extensor mechanism and inoculated intraoperatively (5 per group per isolate). Meshes and surrounding tissues were harvested on postoperative day 9 for quantitative culture. Results For all three isolates, vancomycin-loaded Marlex mesh exhibited sustained antibacterial activity for up to 3 days in vitro based on zone of inhibition testing (days 1–3, p < 0.0001 for each isolate). In vitro testing of biofilm inhibition demonstrated significant reduction in biofilm-associated colony-forming units at 6 hours after inoculation and remained low thereafter (p<0.05 for each isolate). In vivo , vancomycin-loaded Marlex mesh reduced bacterial burden on meshes and surrounding tissues by > 3 log₁₀ compared with plain mesh for all three isolates (p<0.01 for both mesh and tissue for all isolates). Conclusion Vancomycin-loaded Marlex mesh provided sustained local antibacterial activity and significantly reduced staphylococcal infection without compromising mechanical properties in a murine extensor mechanism reconstruction model. This approach may represent a promising adjunct to reduce infection risk in extensor mechanism reconstructions with Marlex mesh after total knee arthroplasty.

Background: Infection following extensor mechanism reconstruction (EMR) with Marlex mesh (C.R. Bard) is devastating and limb-threatening. The purpose of this study was to evaluate whether vancomycin-loaded mesh reduces staphylococcal infection in a murine EMR model. Methods: Mouse-sized, 8-layer mesh constructs were fabricated to simulate clinical reconstruction and soaked in a vancomycin solution (50 mg/mL) for in vitro and in vivo testing. Three methicillin-resistant clinical isolates from human periprosthetic Staphylococcus aureus, Staphylococcus epidermidis, and Staphylococcus lugdunensis knee infections were evaluated. In vitro testing assessed vancomycin loading capacity, mechanical properties, antibacterial activity, and inhibition of biofilm formation. For in vivo experiments, plain or vancomycin-loaded mesh was implanted into C57BL/6 mouse extensor mechanisms, which were intraoperatively contaminated with 1 of the 3 study isolates (5 per group). Mesh and surrounding tissue were harvested for quantitative culture on postoperative day 9. Results: For all 3 isolates, vancomycin-loaded mesh produced zones of inhibition and exhibited antibacterial activity through at least 3 days in vitro (p < 0.0001). Mechanical testing revealed that loading mesh with vancomycin did not negatively impact tensile strength, hysteresis, or suture pull-through properties. In vitro testing of inhibition of biofilm formation demonstrated reduced colony-forming units 6 hours after inoculation, which remained low throughout the 9-day experimental period (p < 0.05 for all isolates). In vivo, vancomycin-loaded mesh reduced bacterial burden on mesh and in surrounding tissue by >3 log 10 compared with plain mesh for all 3 isolates (p < 0.01 for both mesh and tissue). Conclusions: Vancomycin-loaded mesh provided in vitro antibacterial activity without compromising mesh mechanical properties and reduced staphylococcal infection in a murine EMR model. Further work is needed to evaluate translational potential and safety before clinical application. Clinical Relevance: Mesh-associated infection after EMR is devastating and difficult to treat. These preclinical findings suggest that local vancomycin delivery may serve as an adjunct to systemic prophylaxis, warranting further study before clinical use.

Background Staphylococcus aureus causes a multiplicity of human diseases acquired in community and healthcare settings alike around the globe. While most studies focus on coding changes to assess genome evolution and study genetic adaptation, interrogation of silent mutations in the form of synonymous codon usage bias is less well-studied. As such, understanding of patterns in codon bias at the gene and genome levels, and how codon bias impacts protein expression in S. aureus remains incomplete. Methods The codon bias of 2,565 protein encoding genes from NCTC 8325 was queried against all publicly available closed S. aureus genomes. Using public BioSample data, genomes were sorted by disease state, submitting institution, and collection site. Codon bias was assessed at the level of gene and genome using the codon adaptation index (CAI), calculated using 30S and 50S ribosomal genes. Gene set enrichment analysis was applied to determine associations between physiological functions, CAI gene scores, and interquartile ranges. CAI scores were also compared to an in vitro S. aureus proteomics database to correlate codon bias and protein expression. Results CAI scores varied within and between isolates at the gene and genome levels. Genes with ribosome-associated functions were most enriched among high CAI genes, and had low CAI interquartile ranges (IQR), suggesting selective pressure to maintain high expression of these genes across all S. aureus isolates. Genome sequences submitted by Aga Khan University Hospital, Nairobi, Kenya were most different from others. For the LAC USA 300 strain, CAI and protein expression were moderately positively correlated (cor = 0.534, p < 2.2e-16). Conclusions Codon bias in S. aureus was shown to vary between gene, and to be a source of genetic variation between isolates; CAI and in vitro protein expression were positively correlated.

Background: Staphylococcus aureus causes bloodstream and skin infections in humans. The prevalence of multidrug-resistant S. aureus strains means new antibiotics are needed. A novel antimicrobial drug named SK-03-92, a synthetic aromatic organic stilbenoid compound, kills S. aureus cells within 30 min, but an increase in both biofilm formation and persister cells occurs. SK-03-92 treatment downregulates transcription of the biofilm regulating protein regulator (brpR) gene and biofilm regulating protein sensor (brpS) gene in S. aureus. BrpR/BrpS system may be a LytTR regulatory system tied to biofilm formation, creation of persister cells, and late-stage competence in S. aureus. The aim of this study was to determine what biofilm, late-stage competence, and persister-associated genes were regulated in a brpR mutant compared to wild-type strains. Methods: In this study, involvement of BrpR in regulating other genes was assessed by comparing transcriptional changes in a brpR mutant strain to the S. aureus parent strain via RNA sequencing (RNA-Seq). Bioinformatic analysis was then performed on the RNA-Seq data to assess what biochemical pathways might be involved. Results: From these analyses, 440 genes were identified that had significant differences in transcript abundance when comparing the brpR mutant to wild-type strains. Quantitative reverse transcription polymerase chain reaction analysis confirmed bacA, icd, metE, and pdhA transcript levels were lower, whereas alr and mraY were higher in the brpR mutant versus wild-type strain. Furthermore, an enzymatic assay targeting NADH production from the pyruvate dehydrogenase complex showed lower levels in the mutant compared to wild-type strain. Conclusions: Overall, the study demonstrated several biosynthetic pathways tied to biofilm formation and late-stage competency may be regulated by BrpR and some potential leads for the mechanism of action of the SK-03-92 drug were uncovered.

Aims Extensor mechanism disruption is a major complication following total knee arthroplasty, with treatment often consisting of extensor mechanism reconstruction utilizing monofilament polypropylene mesh (Marlex mesh, C. R. Bard, Inc). Infection following this procedure is devastating, often resulting in revision surgery and mesh removal, with permanent limb dysfunction. This study evaluated the in vitro ability of vancomycin-loaded polypropylene mesh to inhibit growth of isolates of three Staphylococcus species from patients with periprosthetic joint infection. Methods The mesh was prepared in two configurations – single-layer and eight-layer – and soaked for ten minutes in either sterile water (control) or vancomycin solution (50 mg/ml), after which the mesh was placed on tryptic soy agar plates inoculated with staphylococci and incubated at 37°C for 18 to 24 hours. Zones of inhibition were measured daily over seven days, with mesh transferred to freshly inoculated plates daily. Testing was performed in triplicate, with experiments repeated three times for each bacterial isolate. A total of 30 clinical isolates were tested (five methicillin-susceptible Staphylococcus epidermidis , five methicillin-resistant S. epidermidis , ten methicillin-resistant Staphylococcus aureus , and ten Staphylococcus lugdunensis ). Results Across all species, the eight-layer vancomycin-loaded mesh produced statistically significantly larger median zones of inhibition than the single-layer mesh. The antibacterial activity of the eight-layer mesh persisted through to day 7, while the single-layer mesh showed reduced activity by days 4 to 5. Conclusion Compared with single-layer vancomycin-loaded mesh, multilayer vancomycin-loaded mesh, which mimics clinical application, provides enhanced and sustained antibacterial activity in vitro. Cite this article: Bone Joint Res 2026;15(8):998–1004.

Background: We describe an investigation of a cluster of eight Corynebacterium amycolatum sternal surgical site infections (SSIs) that occurred among cardiac surgery patients from February to October 2025. Although C. amycolatum is a member of the skin microbiota, clinically significant infections caused by this organism may occur in cardiac surgery patients. Methods: The investigation included retrospective reviews of SSIs, clinical cultures and medical records, surgical observations, and operating room (OR) assessment. Line lists of surgical case criteria and infection prevention practices were created to assess common factors among cases (e.g., staffing, instrumentation, equipment, skin preparation and antisepsis, nasal decolonization, antibiotic protocols, and closure). Whole genome sequencing of isolates was performed and analyzed using SNIPPY for single-nucleotide polymorphism (SNP)-based phylogenetic analysis. Results: Phylogenetic analysis indicated isolates from five of eight case patients who had cardiac surgeries occurring over a six-week period from February to April 2025 were genetically related (?7 SNPs across the genome), suggesting a common source of infection. These five isolates were ceftriaxone, meropenem, and penicillin resistant. The other three case patient isolates were unrelated (<3181 to <15,000 SNPs); two were ceftriaxone, meropenem and penicillin resistant (one also doxycycline intermediate resistant), and the third penicillin resistant. Use of sternal tape for closure was identified as a recent practice change. Four of five genetically related cases involved the same surgeons and suture tape for sternal closure (wire for all other cases). Sternal tape was discontinued with three cases occurring afterwards. Seven patients completed chlorhexidine gluconate bathing and nasal decolonization. Hair was removed in the OR with reusable surgical clippers. All received the same skin antiseptic, and antibiotic prophylaxis was appropriate. No trends were identified in instrument or equipment use. Broad infection control measures were implemented, including surgical clipper replacement, OR cleaning and ultraviolet light disinfection, headlamp cleaning, and environmental repairs. Leadership was engaged through frequent meetings and audits. Infection control practices such as minimizing OR traffic, double gloving, glove changes, and strict adherence to hand hygiene and attire were reinforced. Two of eight cases occurred after these recommendations were completed but were not genetically related to the primary cluster. Conclusion: We describe a cluster of invasive C. amycolatum sternotomy SSIs. Only two genetically unrelated cases of C. amycolatum occurred following infection control investigation and interventions, underscoring the effectiveness of a comprehensive, multidisciplinary approach. This organism has rarely been reported as a cause of SSIs and may be an emerging pathogen.

ABSTRACT Blood culture contamination can lead to false-positive blood culture results, potentially contributing to increased costs and unneeded antibiotic utilization. Initial specimen diversion devices (ISDD) have been proposed to reduce blood culture contamination rates. A single-center, observational study conducted at Mayo Clinic Rochester compared blood culture contamination rates using Steripath or Kurin ISDDs versus standard blood culture collection protocols. Over 255 phlebotomists were trained in the use of the ISDDs, with 31,215 blood cultures, 410 of which were contaminated, collected from adults in the emergency department and inpatient wards. Baseline contamination rates were 1.29%–2.53% with standard collection methods. The Steripath ISDD with direct-to-media inoculation of blood culture bottles (Steripath-DTM) reduced blood culture contamination compared to standard practice (0.34% vs. 1.43%, respectively, P < 0.001). Follow-up studies with the alternative Steripath configuration with an integrated syringe (Steripath-syringe), and then the Kurin ISDD with syringe collection (Kurin-syringe), did not meet the primary endpoint of <0.5% contamination (Steripath-syringe: 1.28%; Kurin-syringe: 1.76%). All three ISDD configurations failed to meet our goal of >75% utilization, with an average measured utilization of 26% for the Steripath-DTM, 26.4% for the Steripath ISDD (combined DTM and syringe) in a follow-up study, and 41.5% in the Kurin study. Additionally, a survey of phlebotomists revealed low staff satisfaction with both Steripath ISDD configurations. Staff reported multiple ergonomic barriers limiting the Steripath ISDD’s utility, which precluded implementation of the Steripath-DTM in routine clinical practice. IMPORTANCE We conducted a very large, real-world study of two blood diversion devices to determine whether either would meet goals for reduced blood culture contamination and a high rate of utilization by phlebotomists.

Abstract A low-cost, easy-to-adopt noninvasive imaging modality for differentiating bacterial infection from inflammation is desirable to accurately diagnose bacterial infections. Herein, a bacteria-specific PET probe, [68Ga]Ga-BP, was developed and evaluated in rat models of foreign body-associated osteomyelitis induced by methicillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella pneumoniae and was directly compared with sterile inflammation and uninstrumented uninfected controls. [68Ga]Ga-BP-based imaging of MRSA-infected tibiae was also compared to [68Ga]Ga-citrate and [18F]FDG. After iron depletion, dynamic PET/CT imaging was performed at 15–120 min postinjection of radiotracers, followed by assessment of ex vivo biodistribution. [68Ga]Ga-BP successfully detected tibial infection and demonstrated &gt;6-fold higher uptake in infected tibiae with all three bacterial species versus contralateral tibiae via PET imaging. [68Ga]Ga-BP outperformed [68Ga]Ga-citrate and [18F]FDG in identifying MRSA infection. [68Ga]Ga-BP represents a promising, noninvasive PET imaging agent for direct bacterial detection and bacterial infection treatment monitoring.

ABSTRACT Legionella species are important causes of community-acquired pneumonia. The diagnostic performance and clinical implications of a fluorescence resonance energy transfer (FRET)-based real-time PCR assay targeting the Legionella 5S rRNA gene were evaluated, with emphasis on melting temperature (Tm) analysis to differentiate detected species and associated clinical outcomes. A retrospective multicenter cohort study of adults with laboratory-confirmed Legionella infection between 2019 and 2025 was conducted. PCR crossing point (Cp) and Tm data were analyzed and compared with species identified in culture from respiratory specimens. Associations between Tm and clinical outcomes were assessed using multivariable logistic regression. Among 51,489 PCR tests performed, 823 (1.6%) were positive. Among 376 Legionella infections, PCR demonstrated the highest diagnostic yield. Among patients undergoing all three diagnostic tests, the addition of PCR increased detection from 49% with urine antigen and culture combined to 100% ( P < 0.001). Of 189 PCR-positive patient specimens with available Tm data, Tm showed a bimodal distribution, being either <66°C or ≥66°C. A Tm cutoff of ≥66°C discriminated L. pneumophila / L. longbeachae from other Legionella species with excellent performance (AUC, 1.00). Overall, 29.6% of infections had a Tm <66°C, consistent with non- pneumophila/ non- longbeachae Legionella species. Infections due to L. pneumophila / L. longbeachae , which correspond to high Tm values in the study assay, were independently associated with ICU admission (adjusted odds ratio, 2.85; 95% CI, 1.33–6.11; P = 0.007), but not 90-day mortality. Real-time PCR targeting the Legionella 5S rRNA gene provides superior detection compared to culture and/or urine antigen testing and enables higher-risk species discrimination through Tm analysis. IMPORTANCE Nearly one-third of Legionella infections in this cohort were attributable to non- pneumophila species, highlighting limitations of diagnostic strategies reliant on Legionella urine antigen testing or L. pneumophila PCR. The findings suggest that species-level inference can be derived from melting-temperature data generated during routine PCR testing. Incorporating validated melting-temperature interpretation into reporting workflows may improve epidemiologic surveillance and clinical understanding of characteristics of Legionella pneumonia.

ABSTRACT Novel β-lactam/β-lactamase inhibitors (βL/βLIs) are important therapies for carbapenem-resistant Pseudomonas aeruginosa (CRPA). However, the global extent of resistance to these agents and the impact of resistance on patient outcomes are unclear. We therefore evaluated patients with CRPA isolates at 35 hospitals (nine countries) from December 2018 to November 2019. Antimicrobial susceptibility testing was performed at a central laboratory by agar dilution for ceftolozane-tazobactam (C/T) and ceftazidime-avibactam (CZA) and by broth microdilution for imipenem-relebactam (I/R). Characteristics and outcomes, including desirability of outcome rankings (DOOR), were compared between patients infected with isolates not susceptible vs susceptible to each agent. Of 800 CRPA isolates, susceptibility to C/T, CZA, and I/R was 69%, 67%, and 33%, respectively. USA isolates ( n = 526) were more frequently susceptible to these agents than isolates from other countries ( n = 274; C/T: 83% vs 42%; CZA: 77% vs 47%; I/R: 37% vs 23%; P < 0.001 for each comparison) and isolates with carbapenemases ( n = 157) were less frequently susceptible than isolates without carbapenemases ( n = 643; C/T: 7% vs 84%; CZA: 24% vs 77%; I/R: 6% vs 39%; P < 0.001 for each comparison). Thirty-day mortality and DOOR were similar overall in patients infected with isolates not susceptible vs susceptible to each βL/βLI. However, the adjusted probability of a better DOOR outcome for a randomly selected patient with bacteremia due to a C/T-not susceptible vs -susceptible isolate was 38.2% (95% confidence interval, 25.6%–52.7%). Resistance to novel βL/βLIs, especially I/R, is common in CRPA, particularly outside the USA and in carbapenemase-producing isolates. Additional treatment options are needed for CRPA infections.