Karau, Melissa J.

Abstract Background Periprosthetic joint infection (PJI) is associated with significant morbidity. Management includes surgery and prolonged antibiotic treatment. Few studies have evaluated rates of acquired antimicrobial resistance in bacteria causing PJI. The aim of this study was to describe antimicrobial resistance profiles of bacteria causing PJI and to assess whether there was any apparent association between acquired resistance and clinical outcome. Methods Patients at Mayo Clinic with first episodes of knee or hip PJI whose implants underwent sonication between January 2012 and December 2021 were studied. Sonicate fluid cultures from cement spacers or cultures yielding more than one microorganism were excluded. PJI was defined according to IDSA guidelines. Multidrug resistance was defined as non-susceptibility to at least one agent in three or more antimicrobial classes. Outcomes of PJI recurrence, need for further surgery with negative cultures or cultures yielding a new microorganism and amputation were assessed, within one year. Analysis was performed using SAS software version 9.4 (SAS Inc). Results 256 PJI episodes were evaluated, 55% from knees and 45% from hips. Median patient age was 66 years, 52% were men. Resistance profiles are shown in the table. The most frequent microorganisms isolated were S. epidermidis (n=82) and S. aureus (n=50), of which 68% and 30%, respectively, were methicillin resistant. Streptococci, Enterococci, Enterobacterales, and P. aeruginosa were found in 34,16, 8 and 3 cases; none were multidrug-resistant. No differences in PJI recurrence within one year were found in subjects with methicillin-resistant compared to methicillin-susceptible staphylococci (S. aureus, 50% versus 50%, respectively, p, 0.44; S. epidermidis, none), need for further surgery with negative cultures (S. aureus, 20% versus 80%, p, 0.72; S. epidermidis, 80% versus 20%, p, 0.47) or with cultures yielding a new microorganism (S. aureus, none; S. epidermidis, 67% versus 33%, p, 0.96), or amputation (none in any subject with staphylococcal PJI). Conclusion Acquired antimicrobial resistance in PJI was most common in S. epidermidis with methicillin resistance found in 68% and multidrug resistance in 28%. Disclosures Matthew P Abdel, MD, OsteoRemedies: Royalties|Springer: Publishing royalties|Stryker: Royalties reltated to hip and knee implants 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

AbstractBiofilms formed by antibiotic‐resistant bacteria in wound beds challenge the treatment of wound infections. In this work, the activity of a novel electrochemical bandage (e‐bandage) composed of carbon fabric and controlled by a wearable potentiostat, designed to continuously deliver low amounts of hydrogen peroxide (H2O2), is evaluated against methicillin‐resistant Staphylococcus aureus (MRSA), multidrug‐resistant Pseudomonas aeruginosa (MDR‐PA) and mixed‐species (MRSA and MDR‐PA) wound infections. Wounds created on Swiss Webster mice are infected with the above‐named bacteria and biofilms allow to establish in wound beds for 3 days. e‐Bandages, which electrochemically reduce dissolved oxygen to H2O2 when polarized at −0.6 VAg/AgCl, are placed atop infected wound beds and polarized continuously for 48 h. Polarized e‐bandage treatment results in significant reductions (p <0.001) of both monospecies and mixed‐species wound infections. After e‐bandage treatment, electron microscopy shows degradation of bacterial cells, and histopathology shows no obvious alterations to the inflammatory host response. Blood biochemistries show no abnormalities. Taken all together, results of this work suggest that the described H2O2‐producing e‐bandage can reduce in vivo MRSA, MDR‐PA, and mixed‐species wound biofilms, and should be further developed as a potential antibiotic‐free strategy for treatment of wound infections.

Drug-resistant Gram-positive bacterial infections are still a substantial burden on the public health system, with two bacteria ( Staphylococcus aureus and Streptococcus pneumoniae ) accounting for over 1.5 million drug-resistant infections in the United States alone in 2017. In 2019, 250,000 deaths were attributed to these pathogens globally. We have developed a preclinical glycopeptide antibiotic, MCC5145, that has excellent potency (MIC 90 ≤ 0.06 μg/ml) against hundreds of isolates of methicillin-resistant S. aureus (MRSA) and other Gram-positive bacteria, with a greater than 1000-fold margin over mammalian cell cytotoxicity values. The antibiotic has therapeutic in vivo efficacy when dosed subcutaneously in multiple murine models of established bacterial infections, including thigh infection with MRSA and blood septicemia with S. pneumoniae , as well as when dosed orally in an antibiotic-induced Clostridioides difficile infection model. MCC5145 exhibited reduced nephrotoxicity at microbiologically active doses in mice compared to vancomycin. MCC5145 also showed improved activity against biofilms compared to vancomycin, both in vitro and in vivo, and a low propensity to select for drug resistance. Characterization of drug action using a transposon library bioinformatic platform showed a mechanistic distinction from other glycopeptide antibiotics.

Rifampin is an antibiotic with antistaphylococcal biofilm activity used in the management of staphylococcal periprosthetic joint infection with irrigation and debridement with component retention; some patients are unable to receive rifampin due to drug interactions or intolerance. We recently showed rifabutin and rifapentine to have in vitro activity against planktonic and biofilm states of rifampin-susceptible periprosthetic joint infection-associated staphylococci.

Abstract Background The vancapticins are modified vancomycin derivatives developed by adding membrane targeting motifs to the C-terminus of vancomycin. We determined the in vitro activity of a lead vancapticin candidate against periprosthetic joint infection-associated methicillin-resistant Staphylococcus aureus (MRSA) in the planktonic and biofilm states, and the effect of adding 0.002% polysorbate 80 (P-80; Sigma-Aldrich) on vancapticin susceptibility testing. Methods Thirty-seven clinical isolates of MRSA collected at Mayo Clinic (Rochester, Minnesota) were studied. Vancapticin minimum inhibitory concentrations (MICs) were determined using Clinical and Laboratory Standards Institutes guidelines. Minimum biofilm bactericidal concentrations (MBBCs) were determined using a pegged lid microtiter plate assay. Vancapticin MIC and MBBC values were assessed with and without P-80. Vancapticin, vancomycin, and dalbavancin biofilm time-kill assays were performed using biofilms formed by 10 MRSA isolates on Teflon coupons. Results Vancapticin MICs with and without P-80 ranged from 0.015 to 0.12 μg/mL and 0.25 to 1 μg/mL, respectively. Vancapticin MBBCs with and without P-80 ranged from 0.25 to 4 μg/mL and 1 to 8 μg/mL, respectively. Reductions of biofilm bacterial densities on Teflon coupons after 8 and 24 hours of incubation with vancapticin, vancapticin with P-80, vancomycin, or dalbavancin with P-80 were less than 3-log10 cfu/cm2 for all isolates tested. Conclusion Vancapticin has promising in vitro activity against planktonic MRSA and MRSA in a pegged lid biofilm assay, but was not bactericidal against biofilms on Teflon coupons. P-80 decreased vancapticin MICs and MBBCs. Disclosures Mark A. Blaskovich, PhD, MAB Consulting (Consultant)The University of Queensland (Employee, Grant/Research Support, Other Financial or Material Support, Inventor on patent) Robin Patel, MD, Accelerate Diagnostics (Grant/Research Support)CD Diagnostics (Grant/Research Support)Contrafect (Grant/Research Support)Curetis (Consultant)GenMark Diagnostics (Consultant)Heraeus Medical (Consultant)Hutchison Biofilm Medical Solutions (Grant/Research Support)Merck (Grant/Research Support)Next Gen Diagnostics (Consultant)PathoQuest (Consultant)Qvella (Consultant)Samsung (Other Financial or Material Support, Dr. Patel has a patent on Bordetella pertussis/parapertussis PCR issued, a patent on a device/method for sonication with royalties paid by Samsung to Mayo Clinic, and a patent on an anti-biofilm substance issued.)Selux Dx (Consultant)Shionogi (Grant/Research Support)Specific Technologies (Consultant)

Cefiderocol (CFDC) is a siderophore cephalosporin with activity against Gram-negative bacterial species that are resistant to carbapenems and other drugs. The MICs of CFDC were determined for 610 Gram-negative bacilli, including 302 multinational Enterobacterales isolates with characterized mechanisms of beta-lactam resistance, 180 clinical isolates from the Mayo Clinic and Mayo Clinic Laboratories not characterized for specific resistance mechanisms, and 128 isolates with CFDC MICs of ≥8 μg/ml obtained from International Health Management Associates, Inc.

Abstract Background Owing to patient intolerance or drug interactions, alternative agents to rifampin are needed for management of staphylococcal periprosthetic joint infection. In the current study, we evaluated rifabutin, rifapentine and rifampin, with and without vancomycin, in a rat model of foreign body osteomyelitis. Methods Proximal tibiae were inoculated with methicillin-resistant Staphylococcus aureus (MRSA) and a Kirschner wire (K-wire) implanted in each. After 4 weeks of infection, rifampin, rifabutin, or rifapentine were administered, alone or with vancomycin. Tibiae and K-wires were cultured, and medians were reported as log10 colony-forming units (CFUs) per gram of bone or log10 CFUs per K-wire, respectively. Results Rifampin, rifabutin or rifapentine administered with vancomycin yielded less MRSA from bones (0.10, 3.02, and 0.10 log10 CFUs/g, respectively) than did no treatment (4.36 log10 CFUs/g) or vancomycin alone (4.64 log10 CFUs/g) (both P ≤ .02). The K-wires of animals receiving no treatment or vancomycin monotherapy recovered medians of 1.76 and 2.91 log10 CFUs/g per K-wire, respectively. In contrast, rifampin, rifabutin and rifapentine administered with vancomycin yielded medians of 0.1 log10 CFUs per K-wire, respectively. Rifampin resistance was detected in a single animal in the rifampin monotherapy group. Conclusions Rifabutin or rifapentine with vancomycin were as active as rifampin with vancomycin against MRSA in rat foreign body osteomyelitis, suggesting that rifabutin and/or rifapentine may be alternatives to rifampin in the clinical management of staphylococcal periprosthetic joint infections.

Abstract Background Orthopedic foreign body-associated infection can be difficult to treat due to the formation of biofilms protecting microorganisms from both antimicrobials and the immune system. Exebacase (EXE) is a phage-derived lysin which acts as a direct lytic agent by hydrolyzing the peptidoglycan cell wall of Staphylococcus aureus. In this study, the activity of EXE was evaluated in comparison to daptomycin against MRSA biofilms on orthopedic Kirschner wires (K-wires). Methods MRSA strain IDRL-6169 was studied; it has a MIC of 0.5 µg/mL for both daptomycin (DAP) and EXE. Biofilms were formed in 1 mL of 106 cfu/mL tryptic soy broth on 0.5x0.1 mm threaded stainless steel K-wires for 10 hours, after which the wires were removed from the media and placed into 0.04 mL of either DAP or EXE at 0 (vehicle only), 0.098, 0.98, or 9.8 mg/mL. DAP+EXE was also tested, each at 0.098 mg/mL. Bacteria were quantified after 0, 2, 4, 8, and 12 hours of incubation at 37ºC. Testing was performed in triplicate. Results were reported as log10 cfu/K-wire reduction relative to vehicle alone. A 3-log10 cfu/K-wire reduction was considered bactericidal. P-values were calculated using Kruskal–Wallis. Results The bacterial burden of vehicle alone ranged from 5.49- to 6.33-log10 cfu/K-wire at all time points. Bacterial reductions for each treatment compared with carrier solution are shown in the table. DAP showed no bactericidal activity. EXE showed bactericidal activity at all concentrations at all time points studied except 0.098 mg/mL at 8 hours. There was no significant difference between EXE at 0.098 and 0.98 mg/mL at any time point but EXE at 9.8 mg/mL did show superiority over the lower concentrations. DAP+EXE 0.098 mg/mL was bactericidal at all time points. Conclusion EXE showed a rapid effect against MRSA biofilms on orthopedic K-wires apparent within the first 2 hours of exposure and was more active than daptomycin alone at the same concentrations. Disclosures All authors: No reported disclosures.