Greenwood‐Quaintance, Kerryl E.

Abstract Background Wound biofilm infections impact ∼2% of the United States and at-risk individuals often have underlying morbidities such as diabetes. Antibiotics and topical approaches like debridement or silver dressings have had limited success, underscoring a need for strategies that efficiently target pathogens in wound beds. Methods We developed a hydrogen peroxide (H2O2) generating electrochemical bandage (e-bandage) composed of carbon fabric electrodes separated by cotton fabric with an Ag/AgCl reference electrode (RE) placed between cotton fabric layers. The e-bandage is controlled by a wearable micropotentiostat (MP); H2O2 is generated by O2 + 2H++ 2e- → H2O2. O2 is dissolved on a primary working electrode with negative polarity compared to the RE while a positively polarized secondary counter electrode generates H+ and e-. The H2O2 e-bandage/MP device has in vitro activity against mono- and dual-species bacterial and fungal biofilms. We showed that the H2O2 e-bandage decreased the burden of methicillin-resistant Staphylococcus aureus and/or Pseudomonas aeruginosa with difficult-to-treat resistance in a murine wound infection model. Given this, we initiated a H2O2 e-bandage safety assessment on healthy human skin. Here, testing of a non-polarized, circular (2 cm diameter) device pre-loaded with biocompatible hydrogel containing 0.9% NaCl is reported. Sterilized e-bandages assessed in a shelf-life study retained activity for two weeks. Adults with intact forearm skin were then recruited to the Clinical Research Trials Unit at the Mayo Clinic. Consented individuals had a non-polarized e-bandage covered by Tegaderm placed on their forearm. A MP enclosed in a biocompatible case was connected to the e-bandage and secured using skin tape. One day later, the device was removed and a follow-up phone call made six days later to assess for adverse effects. Results Three volunteers wearing a non-polarized H2O2 e-bandage experienced no discomfort, irritation, allergic reaction, or skin discoloration after device removal and seven days post device placement. Conclusion These preliminary studies combined with the previously performed murine bacterial biofilms work support further studies of this novel device for treating wound infections caused by antimicrobial resistant pathogens. Disclosures Robin Patel, MD, a patent on Bordetella pertussis/parapertussis PCR issued, a patent on a device/method for sonication with royalties paid by Samsung to Mayo Clinic, a: See above|MicuRx Pharmaceuticals and BIOFIRE: Grant/Research Support|PhAST, Day Zero Diagnostics, Abbott Laboratories, Sysmex, DEEPULL DIAGNOSTICS, S.L., Netflix, Oxford Nanopore Technologies and CARB-X: Advisor/Consultant|Up-to-Date and the Infectious Diseases Board Review Course.: Honoraria

Abstract Background Drug-resistant E. coli is a leading cause of antimicrobial resistance-associated deaths globally. Specifically, resistance to ceftriaxone (CRO-R) is increasing in E. coli. High-risk clonal group ST131 and its pandemic H30 subclone are of high concern yet studies characterizing these infections are limited. We evaluated baseline characteristics and clinical outcomes associated with H30 ST131, non-H30 ST131 and non-ST131 E. coli bloodstream infections (BSI). Methods Patients with monomicrobial carbapenem-susceptible E. coli BSI that were matched 1:1 by study site (CRO-R and CRO-susceptible community-acquired and hospital onset cases) were prospectively enrolled from 14 United States hospitals between November 12, 2020 to April 28, 2021 in the multicenter Study of Highly Resistant E. coli (SHREC). Isolates underwent whole genome sequencing. The primary outcome was a 30-day Desirability of Outcome Ranking (DOOR) after index culture including clinical response to treatment and all-cause mortality. Results There were 92 (33%) H30 ST131, 29 (10%) non-H30 ST131, and 161 (57%) non-ST131 isolates in 282 E. coli BSI (Table 1). Most ceftriaxone resistance was conferred by CTX-M-15 produced by H30 ST131 isolates (Figure 1, Table 1). H30 ST131 BSI patients were older (median age [IQR] 70.5 [63,76] vs. 67 [56,77] vs 65 [51,74] years, p = 0.017), had higher Charlson comorbidity indices (3 [2,5] vs. 2 [1,4] vs. 2 [1,4], p=0.009), and were more often admitted from long-term care facilities (18/92 [20%] vs. 3/29 [10%] vs. 7/161 [4%], p = 0.003) compared to non-H30 ST131 and non-ST131 BSI patients. Among H30 ST131 isolates, high rates of antibiotic resistance were observed to cephalosporins and fluoroquinolones, resulting in significantly more carbapenem use compared with non-H30 ST131 and non-ST131 isolates (75/92 [82%] vs. 14/29 [48%] vs. 50/161 [31%], p < 0.001) (Figure 2). 30-day DOOR and hospital length of stay did not differ between groups (Table 2). Conclusion Compared with non-H30 ST131 and non-ST131 E. coli BSI, H30 ST131 E. coli BSI have a unique epidemiology with more healthcare exposures, comorbidities and antibiotic resistance and are more likely to be treated with carbapenems, though no significant difference in clinical outcomes was observed. Disclosures Yohei Doi, MD, PHD, AbbVie: Honoraria|Entasis: Grant/Research Support|Gilead: Advisor/Consultant|GSK: Advisor/Consultant|Meiji Seika: Advisor/Consultant|Moderna: Advisor/Consultant|Pfizer: Advisor/Consultant|Shionogi: Advisor/Consultant|Shionogi: Honoraria Elie Saade, MD, MPH, FIDSA, Janssen Global Services: Advisor/Consultant|Janssen Global Services: Advisor/Consultant|Janssen Research and Development: Advisor/Consultant|Janssen Research and Development: Advisor/Consultant Loren G. Miller, MD MPH, Armata: Grant/Research Support|Contrafect: Grant/Research Support|GSK: Grant/Research Support|Merck: Grant/Research Support|Paratek: Grant/Research Support Michael J. Satlin, MD, AbbVie: DSMB participant|bioMerieux: Grant/Research Support|Merck: Grant/Research Support|Selux Diagnostics: Grant/Research Support|SNIPRBiome: Grant/Research Support W. Charles Huskins, MD, MSc, ADMA Biologics: Advisor/Consultant|Bristol Myers Squibb: Stocks/Bonds (Public Company)|Pfizer: Advisor/Consultant|Pfizer: Stocks/Bonds (Public Company)|Zimmer Biomet: Stocks/Bonds (Public Company) Carol Hill, PhD, Glaxo SmithKline: Retirement Health, Cash Balance Plan|Glaxo SmithKline: Stocks/Bonds (Public Company) Robin Patel, MD, a patent on Bordetella pertussis/parapertussis PCR issued, a patent on a device/method for sonication with royalties paid by Samsung to Mayo Clinic, a: See above|MicuRx Pharmaceuticals and BIOFIRE: Grant/Research Support|PhAST, Day Zero Diagnostics, Abbott Laboratories, Sysmex, DEEPULL DIAGNOSTICS, S.L., Netflix, Oxford Nanopore Technologies and CARB-X: Advisor/Consultant|Up-to-Date and the Infectious Diseases Board Review Course.: Honoraria Vance G. Fowler, MD, MHS, Affinergy: Advisor/Consultant|ArcBio: Stocks/Bonds (Private Company)|Armata: Advisor/Consultant|Astra Zeneca: Advisor/Consultant|Astra Zeneca: Grant/Research Support|Basilea: Advisor/Consultant|Basilea: Grant/Research Support|ContraFect: Advisor/Consultant|ContraFect: Grant/Research Support|Debiopharm: Advisor/Consultant|Destiny: Advisor/Consultant|EDE: Grant/Research Support|Genentech: Advisor/Consultant|Genentech: Grant/Research Support|GSK: Advisor/Consultant|Janssen: Advisor/Consultant|Karius: Grant/Research Support|MedImmune: Grant/Research Support|Merck: Grant/Research Support|sepsis diagnostics: Patent pending|UptoDate: Royalties|Valanbuio: Stocks/Bonds (Private Company)|Valanbuio: Stocks/Bonds (Private Company) David van Duin, MD, PhD, Merck: Advisor/Consultant|Merck: Grant/Research Support|Pfizer: Advisor/Consultant|Qpex: Advisor/Consultant|Roche: Advisor/Consultant|Shionogi: Advisor/Consultant|Shionogi: Grant/Research Support

ABSTRACT Wound infections, exacerbated by the prevalence of antibiotic-resistant bacterial pathogens, necessitate innovative antimicrobial approaches. Polymicrobial infections, often involving Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus (MRSA), present challenges due to biofilm formation and antibiotic resistance. Hypochlorous acid (HOCl), a potent antimicrobial agent, holds promise as an alternative therapy. An electrochemical bandage (e-bandage) that generates HOCl in situ via precise polarization controlled by a miniaturized potentiostat was evaluated for the treatment of murine wound biofilm infections containing both P. aeruginosa with “difficult-to-treat” resistance and MRSA. Previously, HOCl-producing e-bandage was shown to reduce murine wound biofilms containing P. aeruginosa alone. Here, in 5-mm excisional skin wounds containing 48-h biofilms comprising MRSA and P. aeruginosa combined, polarized e-bandage treatment reduced MRSA by 1.1 log 10 CFU/g ( P = 0.026) vs non-polarized e-bandage treatment (no HOCl production), and 1.4 log 10 CFU/g (0.0015) vs Tegaderm only controls; P. aeruginosa was similarly reduced by 1.6 log 10 CFU/g ( P = 0.0032) and 1.6 log 10 CFU/g ( P = 0.0015), respectively. For wounds infected with MRSA alone, polarized e-bandage treatment reduced bacterial load by 1.1 log 10 CFU/g ( P = 0.0048) and 1.3 log 10 CFU/g ( P = 0.0048) compared with non-polarized e-bandage and Tegaderm only, respectively. The e-bandage treatment did not negatively impact wound healing or cause tissue toxicity. The addition of systemic antibiotics did not enhance the antimicrobial efficacy of e-bandages. This study provides additional evidence for the HOCl-producing e-bandage as a novel antimicrobial strategy for managing wound infections, including in the context of antibiotic resistance and polymicrobial infections. IMPORTANCE New approaches are needed to combat the rise of antimicrobial-resistant infections. The HOCl-producing electrochemical bandage (e-bandage) leverages in situ generation of HOCl, a natural biocide, for broad-spectrum killing of wound pathogens. Unlike traditional therapies that may exhibit limited activity against biofilms and antimicrobial-resistant organisms, the e-bandage offers a potent, standalone solution that does not contribute to further resistance or require adjunctive antibiotic therapy. Here, we show the ability of the e-bandage to address polymicrobial infection by antimicrobial resistant clinical isolates of Staphylococcus aureus and Pseudomonas aeruginosa , two commonly isolated, co-infecting wound pathogens. Effectiveness of the HOCl-producing e-bandage in reducing pathogen load while minimizing tissue toxicity and avoiding the need for systemic antibiotics underscores its potential as a tool in managing complex wound infections.

ABSTRACT Over 2.5 million prosthetic joint implantation surgeries occur annually in the United States. Periprosthetic joint infections (PJIs), though occurring in only 1–2% of patients receiving replacement joints, are challenging to diagnose and treat and are associated with significant morbidity. The Gram-positive bacterium Enterococcus faecalis , which can be highly antibiotic-resistant and is a robust biofilm producer on indwelling medical devices, accounts for 2–11% of PJIs. E. faecalis PJIs are understudied compared to those caused by other pathogens, such as Staphylococcus aureus . This motivates the need to generate a comprehensive understanding of E. faecalis PJIs to guide future treatments for these infections. To address this, we describe a panel of E. faecalis strains isolated from the surface of prosthetic joints in a cohort of individuals treated at the Mayo Clinic in Rochester, MN. Here, we present the first complete genome assemblage of E. faecalis PJI isolates. Comparative genomics shows differences in genome size, virulence factors, antimicrobial resistance genes, plasmids, and prophages, underscoring the genetic diversity of these strains. These isolates have strain-specific differences in in vitro biofilm biomass, biofilm burden, and biofilm morphology. We measured robust changes in biofilm architecture and aggregation for all isolates when grown in simulated synovial fluid (SSF). Finally, we evaluated the antibiotic efficacy of these isolates and found strain-specific changes across all strains when grown in SSF. Results of this study highlight the existence of genetic and phenotypic heterogeneity among E. faecalis PJI isolates which will provide valuable insight and resources for future E. faecalis PJI research. IMPORTANCE Periprosthetic joint infections (PJIs) affect ~1–2% of those who undergo joint replacement surgery. Enterococcus faecalis is a Gram-positive opportunistic pathogen that causes ~10% of PJIs in the United States each year, but our understanding of how and why E. faecalis causes PJIs is limited. E. faecalis infections are typically biofilm-associated and can be difficult to clear with antibiotic therapy. Here, we provide complete genomes for four E. faecalis PJI isolates from the Mayo Clinic. These isolates have strain-specific differences in biofilm formation, aggregation, and antibiotic susceptibility in simulated synovial fluid. These results provide important insight into the genomic and phenotypic features of E. faecalis isolates from PJI.

Abstract Introduction Implant sonication is useful for recovery of periprosthetic joint infection (PJI) pathogens in culture, but exact cutoff points for definition of clinically significant sonicate fluid culture results vary from study to study. The aim of this study was to define ideal sonicate fluid culture cutoff points for PJI diagnosis. Methods Sonicate fluid cultures from hip and knee prosthesis components removed between February 2007 and December 2020 were studied. Prosthesis components were placed in solid containers in the operating room; in the clinical microbiology laboratory, 400 mL Ringer's solution was added, and containers subjected to vortexing, sonication and then vortexing, followed by centrifugation. Concentrated sonicate fluid was plated on aerobic and anaerobic solid media, and culture results reported semiquantitatively, as no growth, <20, 20–50, 51–100, or >100 CFU/10 mL sonicate fluid. Sonicate cultures from cement spacers and cultures yielding more than 1 microorganism were excluded. Sensitivity and specificity of each cutoff point was evaluated. Results A total of 1448 sonicate fluid cultures were evaluated, 68% from knees and 32% from hips. PJI was present in 644 (44%) cases. Sensitivity of sonicate culture was 75.0% at <20 CFU/10 mL, 55.3% at ≥20 CFU/10 mL, 46.9% at >51 CFU/10 mL, and 39.8% at >100 CFU/10 mL. Specificity was 78.2%, 99.8%, 100%, and 100%, at the 4 cutoff points, respectively. Conclusions A cutoff point for sonicate fluid culture positivity of ≥20 CFU/10 mL is suitable for PJI diagnosis.

ABSTRACT The activity of a novel β-lactamase inhibitor combination, sulbactam-durlobactam (SUL-DUR), was tested against 87 colistin-resistant and/or cefiderocol-non-susceptible carbapenem-resistant Acinetobacter baumannii clinical isolates collected from U.S. hospitals between 2017 and 2019. Among them, 89% and 97% were susceptible to SUL-DUR and imipenem plus SUL-DUR, with MIC 50 /MIC 90 values of 2 µg/mL/8 µg/mL and 1 µg/mL/4 µg/mL, respectively. The presence of amino acid substitutions in penicillin-binding protein 3, including previously reported A515V or T526S, was associated with SUL-DUR non-susceptibility.

ABSTRACT The growing threat of antibiotic-resistant bacterial pathogens necessitates the development of alternative antimicrobial approaches. This is particularly true for chronic wound infections, which commonly harbor biofilm-dwelling bacteria. A novel electrochemical bandage (e-bandage) delivering low-levels of hypochlorous acid (HOCl) was evaluated against Pseudomonas aeruginosa murine wound biofilms. 5 mm skin wounds were created on the dorsum of mice and infected with 10 6 colony-forming units (CFU) of P. aeruginosa . Biofilms were formed over 2 days, after which e-bandages were placed on the wound beds and covered with Tegaderm. Mice were administered Tegaderm-only (control), non-polarized e-bandage (no HOCl production), or polarized e-bandage (using an HOCl-producing potentiostat), with or without systemic amikacin. Purulence and wound areas were measured before and after treatment. After 48 hours, wounds were harvested for bacterial quantification. Forty-eight hours of polarized e-bandage treatment resulted in mean biofilm reductions of 1.4 log 10 CFUs/g ( P = 0.0107) vs non-polarized controls and 2.2 log 10 CFU/g ( P = 0.004) vs Tegaderm-only controls. Amikacin improved CFU reduction in Tegaderm-only ( P = 0.0045) and non-polarized control groups ( P = 0.0312) but not in the polarized group ( P = 0.3876). Compared to the Tegaderm-only group, there was less purulence in the polarized group ( P = 0.009). Wound closure was neither impeded nor improved by either polarized or non-polarized e-bandage treatment. Concurrent amikacin did not impact wound closure or purulence. In conclusion, an HOCl-producing e-bandage reduced P. aeruginosa in wound biofilms with no impairment in wound healing, representing a promising antibiotic-free approach for addressing wound infection.

Abstract Background Several randomized controlled trials (RCT) have shown that short-course (∼7 days) antibiotic treatment is non-inferior to longer antibiotic courses (∼14 days) in patients with uncomplicated bloodstream infection (BSI) with mostly susceptible Gram-negative bacteria. Here, we evaluate short-course therapy in ceftriaxone-resistant E. coli BSI. Methods In a prospective cohort of 300 patients with E. coli BSI at 14 United States hospitals between November 2020 and April 2021, each patient with ceftriaxone-R E. coli BSI, and the next consecutive patient with a ceftriaxone-S E. coli BSI was included. Patients who received 5-8 days (“short”) or 9-21 days (“long”) of antibiotics were included in this analysis. Patients who died before day 9 were excluded. Primary outcome was a Desirability of Outcome Ranking (DOOR, Table 1) based on disposition at day 30 after collection of the index blood culture. Ceftriaxone susceptibility was centrally determined using broth microdilution for all bacterial isolates. Desirability of outcome ranking (DOOR) categories Results Of 300 patients in the original cohort, 227 were included; 44 patients (24 ceftriaxone-S, 20 ceftriaxone-R) received short (median 8 days, range 5-8 days), and 183 patients (96 ceftriaxone-S, 87 ceftriaxone-R) received long duration (median 15 days, range 9-21 days). Age (median 68 years, IQR 57-77 years), sex (125/227 [55%] female), and Charlson comorbidity index (median 2, IQR 1-4) were similar between groups. Notably, almost all patients (18/19, 95%) with solid organ or stem cell transplant were in the long duration group. The median Pitt bacteremia score was 2 (IQR 1-3) in the short duration group vs. 1 (IQR 0-3) in the long duration group (Wilcoxon Rank Sum p=0.07). DOOR outcomes were similar in both groups (Figure and Table 2). Numerically more patients in the ceftriaxone-resistant group on short treatment were in category 3; 4/20 (20%) vs 5/87 (6%) in the long duration group. These 4 patients all had unsuccessful discharge combined with renal failure (n=2), and/or lack of clinical response (n=3). Desirability of outcome ranking (DOOR) analysesFigure.DOOR outcomes Shown are the percentages of patients in each group with a specific DOOR category outcome. Conclusion Short duration of therapy was less frequently used than long duration of therapy in this prospective cohort of E. coli BSI. Further studies are needed to determine whether short-course therapy is appropriate for ceftriaxone-R E. coli BSI. Disclosures Yohei Doi, MD, PHD, bioMerieux: Advisor/Consultant|FujiFilm: Advisor/Consultant|Gilead: Advisor/Consultant|Gilead: Honoraria|GSK: Advisor/Consultant|Meiji Seika Pharma: Advisor/Consultant|Moderna: Advisor/Consultant|Moderna: Honoraria|MSD: Advisor/Consultant|MSD: Honoraria|Shionogi: Advisor/Consultant|Shionogi: Grant/Research Support|Shionogi: Honoraria Owen Albin, MD, Charles River Laboratories: Advisor/Consultant|Shionogi: Advisor/Consultant Elie Saade, MD, MPH, FIDSA, Envision Pharma: Speaker, Presenter|Johnson and Johnson: Speaker, Travel, Lodging|Protein Sciences Corp: Grant/Research Support|Sanofi Pasteur: Speaker, Travel and Lodging Loren G. Miller, MD MPH, ContraFect: Grant/Research Support|GSK: Grant/Research Support|Medline: Grant/Research Support|Merck: Grant/Research Support|Paratek: Grant/Research Support Michael J. Satlin, MD, AbbVie: IDMC member|Biomerieux: Grant/Research Support|Merck: Grant/Research Support|Shionogi: Advisor/Consultant|SNIPRBiome: Grant/Research Support Martin Krsak, MD, MSc, FASAM, AbbVie: Grant/Research Support|Melinta: Honoraria W. Charles Huskins, MD, MSc, ADMA Biologics: Advisor/Consultant|Bristol Myers Squibb: Stocks/Bonds|Pfizer: Advisor/Consultant|Pfizer: Stocks/Bonds|Zimmer Biomet: Stocks/Bonds Robin Patel, MD, Abbott Laboratories: Advisor/Consultant|Adaptive Phage Therapeutics: Grant/Research Support|Adaptive Phage Therapeutics: Mayo Clinic has a royalty-bearing know-how agreement and equity in Adaptive Phage Therapeutics.|BIOFIRE: Grant/Research Support|CARB-X: Advisor/Consultant|ContraFect: Grant/Research Support|Day Zero Diagnostics: Advisor/Consultant|HealthTrackRx: Advisor/Consultant|Mammoth Biosciences: Advisor/Consultant|Netflix: Advisor/Consultant|Oxford Nanopore Technologies: Advisor/Consultant|PhAST: Advisor/Consultant|See details: Patent on Bordetella pertussis/parapertussis PCR issued, a patent on a device/method for sonication with royalties paid by Samsung to Mayo Clinic|See details: continued, patent on an anti-biofilm substance issued|TenNor Therapeutics Limited: Grant/Research Support|Torus Biosystems: Advisor/Consultant|Trellis Bioscience, Inc.: Advisor/Consultant Vance G. Fowler, MD, MHS, Amphliphi Biosciences, Integrated Biotherapeutics; C3J, Armata, Valanbio; Akagera, Aridis, Roche, Astra Zeneca: Advisor/Consultant|Genentech, Regeneron, Deep Blue, Basilea, Janssen;: Grant/Research Support|Infectious Diseases Society of America: Honoraria|MedImmune, Allergan, Pfizer, Advanced Liquid Logics, Theravance, Novartis, Merck; Medical Biosurfaces; Locus; Affinergy; Contrafect; Karius;: Grant/Research Support|Novartis, Debiopharm, Genentech, Achaogen, Affinium, Medicines Co., MedImmune, Bayer, Basilea, Affinergy, Janssen, Contrafect, Regeneron, Destiny,: Advisor/Consultant|Sepsis diagnostic: Patent pending|UpToDate: Royalties|Valanbio and ArcBio: Stock Options David van Duin, MD, PhD, Entasis: Advisor/Consultant|Merck: Advisor/Consultant|Merck: Grant/Research Support|Pfizer: Advisor/Consultant|Pfizer: Honoraria|Qpex: Advisor/Consultant|Roche: Advisor/Consultant|Shionogi: Advisor/Consultant|Shionogi: Grant/Research Support|Union: Advisor/Consultant|Utility: Advisor/Consultant

Abstract Background Methicillin-resistant Staphylococcus aureus (MRSA) biofilms can be resilient to the human immune system and antibiotics, a challenge augmented by acquired antimicrobial resistance. Phage therapy is being evaluated for biofilm-associated infections. Methods Here, model phages SaMD07ø1 and SaRB105030ø5 were evaluated against their hosts SaMD07 and SaRB105030, respectively, grown as biofilms in 96-well plates, as biofilms on glass beads and planktonically. Trypticase soy broth (TSB) and phosphate buffered saline (PBS) were evaluated as testing media (Figure 1). Biofilms were incubated with phages in the presence of media containing tetrazolium dye in 96-well plates and assessed for hold times (delays in reaching bacterial log-phase metabolic activity compared to controls) over 48 hours (h) using a Biolog Omnilog® system and by assessing colony forming units (CFUs). Subsequently, using the beads biofilm assay in TSB medium performed on the Omnilog® (BBTO) (Figure 2), test phage SaMD22ø1 was evaluated in quintuplicate against biofilms formed by MRSA isolates IDRL-6130, IDRL-6927, IDRL-6987, IDRL-7381, IDRL-7542 and IDRL-10947, all recovered from periprosthetic joint infection. Test phage K was evaluated against GFP-labelled MRSA AH1263 using BBTO method and simultaneously by fluorescence microscopy.Figure 1.Biofilm phage susceptibility testing methods evaluated (created with BioRender.com)Figure 2.Biofilm phage susceptibility testing using biofilms grown on beads assessed in TSB medium using the Omnilog® (BBTO) method with phage SaMD22ø1. Results A comparison of result of testing of biofilms in wells and on beads and against planktonic bacteria is shown in Figure 3. Phage SaMD07ø1 showed no growth at 4 h; whereas phage SaRB105030ø5 showed ∼1-log decrease in CFUs at 4 h and ∼3-log decrease in CFUs at 8 h (Figure 3). BBTO hold-times of 37, 28 and 15 h were observed for phages SaMD07ø1, SaRB105030ø5 and phage K respectively. Phage SaMD22ø1 had an average hold time of 9 h and showed hold times >6 hours for all isolates tested (Figure 4). Microscopic inspection showed eradication of GFP-labelled MRSA biofilm by phage K (Figure 5).Figure 3.Results of quantitative culture of biofilms treated with phages SaMD07ø1 and SaRB105030ø5 in TSB medium.Panel 1 shows results of phage SaMD07ø1 with biofilms grown in wells (1a), on beads (1b) and planktonically (1c). Panel 2 shows results of phage SaRB105030ø5 with biofilms grown in wells (2a), on beads (2b) and planktonically (2c).Figure 4.Activity of phage SaMD22ø1 against biofilms formed by six MRSA strains determined using the Omnilog® (BBTO) method. The solid blue line indicates a hold time of 8 hours.Figure 5.Efficacy of Phage K to efficiently eradicate GFP-labelled MRSA strain AH1263 observed under the fluorescence microscope at 40X magnification. The authors are thankful to Dr. Alexander Horswill at University of Colorado for providing the GFP-labelled MRSA strain. Conclusion In conclusion, BBTO is a promising method for testing biofilm phage susceptibility although clinical correlation and testing of larger numbers of phage and bacterial isolates are needed. Disclosures Joseph Fackler, n/a, Adaptive Phage Therapeutics, Inc: Employee|Adaptive Phage Therapeutics, Inc: Stocks/Bonds John M. Sowers, n/a, Adaptive Phage Therapeutics: Employee|Adaptive Phage Therapeutics: Stocks/Bonds Robin Patel, MD, Abbott Laboratories: Advisor/Consultant|Adaptive Phage Therapeutics: Grant/Research Support|Adaptive Phage Therapeutics: Mayo Clinic has a royalty-bearing know-how agreement and equity in Adaptive Phage Therapeutics.|BIOFIRE: Grant/Research Support|CARB-X: Advisor/Consultant|ContraFect: Grant/Research Support|Day Zero Diagnostics: Advisor/Consultant|HealthTrackRx: Advisor/Consultant|Mammoth Biosciences: Advisor/Consultant|Netflix: Advisor/Consultant|Oxford Nanopore Technologies: Advisor/Consultant|PhAST: Advisor/Consultant|See details: Patent on Bordetella pertussis/parapertussis PCR issued, a patent on a device/method for sonication with royalties paid by Samsung to Mayo Clinic|See details: continued, patent on an anti-biofilm substance issued|TenNor Therapeutics Limited: Grant/Research Support|Torus Biosystems: Advisor/Consultant|Trellis Bioscience, Inc.: Advisor/Consultant

Abstract Background Biofilms formed by antibiotic-resistant bacteria in wound beds present unique challenges in terms of treating wound infections. In this work, the in vivo anti-biofilm activity of a novel electrochemical bandage (e-bandage) designed to continuously deliver low amounts of hypochlorous acid (HOCl) was evaluated against wound biofilm infections caused by a clinical isolate of Pseudomonas aeruginosa resistant to all antibiotic classes except aminoglycosides. Methods 5 mm skin wounds were created on the dorsal surface of Swiss-Webster mice and infected with 106 CFU of P. aeruginosa. Biofilms were allowed to form over 2 days, after which e-bandages with Tegaderm™ or Tegaderm only were placed on the wound beds. Specifically, mice were randomized to one of three experimental groups (n = 7-8): 1) Tegaderm only (control); 2) non-polarized e-bandage; 3) polarized e-bandage using a wearable potentiostat. After 48 hours, animals were sacrificed and 10 mm skin biopsies containing the wound and surrounding tissue were harvested for bacterial quantification. Histopathology was performed on H&E-stained sections of wound beds from each treatment group. Blood was screened with an inflammatory cytokine panel. Wound healing (% area reduction; digital measurement) and purulence (observational scoring) were assessed in pre- and post-treatment wounds. Results 48 hours of polarized e-bandage treatment resulted in a mean reduction of 1.86 log10 biofilm CFUs/g (p < 0.0001) vs non-polarized controls, and 2.18 log10 CFU/g reduction (p < 0.0001) vs Tegaderm only controls (polarized, 7.6 ± 0.66 log10 CFU/g; non-polarized, 9.45 ± 0.26 log+10 CFU/g; Tegaderm only, 9.78 ± 0.16 log10 CFU/g). Compared to Tegaderm only, purulence reduction and wound healing were significantly higher for both non-polarized (purulence - p < 0.0001; healing - p < 0.01 ) and polarized treatment (purulence - p < 0.0001; healing - p < 0.0001) groups, but were not significantly different from each other. Histopathology and blood inflammation panel testing showed no significant differences between groups. Conclusion An HOCl-producing e-bandage reduced P. aeruginosa in wound biofilms, representing a potential antibiotic-free strategy for the treatment of recalcitrant wound infections. Disclosures Audrey N. Schuetz, MD, Merck: Advisor/Consultant Robin Patel, MD, Abbott Laboratories: Advisor/Consultant|Adaptive Phage Therapeutics: Grant/Research Support|Adaptive Phage Therapeutics: Mayo Clinic has a royalty-bearing know-how agreement and equity in Adaptive Phage Therapeutics.|BIOFIRE: Grant/Research Support|CARB-X: Advisor/Consultant|ContraFect: Grant/Research Support|Day Zero Diagnostics: Advisor/Consultant|HealthTrackRx: Advisor/Consultant|Mammoth Biosciences: Advisor/Consultant|Netflix: Advisor/Consultant|Oxford Nanopore Technologies: Advisor/Consultant|PhAST: Advisor/Consultant|See details: Patent on Bordetella pertussis/parapertussis PCR issued, a patent on a device/method for sonication with royalties paid by Samsung to Mayo Clinic|See details: continued, patent on an anti-biofilm substance issued|TenNor Therapeutics Limited: Grant/Research Support|Torus Biosystems: Advisor/Consultant|Trellis Bioscience, Inc.: Advisor/Consultant