Thigh Model Research Articles

In vivo exposure-response relationship of meropenem against metallo-β-lactamase-harbouring Pseudomonas aeruginosa: an assessment using MICs from conventional and zinc-limited broth.

Previous investigations into metallo-β-lactamase (MBL)-harbouring Enterobacterales suggest that susceptibility testing in zinc-limited media may be more appropriate in predicting β-lactam in vivo activity. There are limited data with MBL-harbouring Pseudomonas aeruginosa. Forty-three MBL-harbouring P. aeruginosa isolates (IMP, n = 11; VIM, n = 12; NDM, n = 10; SPM, n = 10) and two P. aeruginosa control isolates (KPC, n = 1; WT, n = 1) were evaluated. Meropenem activity was evaluated in the murine neutropenic thigh model using humanized exposures. Susceptibility testing was conducted in conventional CAMHB, EDTA-supplemented CAMHB (3-300 mg/L EDTA) and Chelex-treated CAMHB (0-1.0 mg/L re-supplemented zinc), resulting in a range of meropenem MIC values for each isolate. A sigmoidal Emax model was fitted to fT>MIC versus change in log10 cfu/thigh to estimate the goodness of fit (R2). Increasing EDTA concentrations or limiting the amount of zinc in broth resulted in several-fold reductions in MIC among the majority of the MBL-harbouring P. aeruginosa while the MICs for the KPC and WT isolates were unchanged. Bacterial killing in vivo was variable, with the range of killing spanning -3.29 to +4.81 log10 change in cfu/thigh. Addition of 30 mg/L EDTA and Chelex-treated CAMHB (with no zinc supplementation) provided broth conditions for susceptibility testing that best predicted in vivo efficacy (R2 > 0.7). Among MBL-harbouring P. aeruginosa, meropenem in vivo efficacy is best represented by the pharmacodynamic profile generated using MICs determined in EDTA-supplemented or zinc-limited broth. In addition to previous data with Enterobacterales, antibiotic susceptibility testing in media that approximates physiological conditions makes it possible to uncover potential and existing therapeutic agents.

Phenotypes, genotypes and breakpoints: an assessment of β-lactam/ β-lactamase inhibitor combinations against OXA-48.

Two out of the three recently approved β-lactam (BL)/β-lactamase inhibitors (BLIs) have higher CLSI susceptibility breakpoints (ceftazidime/avibactam 8 mg/L; meropenem/vaborbactam 4 mg/L) compared with the BL alone (ceftazidime 4 mg/L; meropenem 1 mg/L). This can lead to a therapeutic grey area on susceptibility reports depending on resistance mechanism. For instance, a meropenem-resistant OXA-48 isolate (MIC 4 mg/L) may appear as meropenem/vaborbactam-susceptible (MIC 4 mg/L) despite vaborbactam's lack of OXA-48 inhibitory activity. OXA-48-positive (n = 51) and OXA-48-negative (KPC, n = 5; Klebsiella pneumoniae WT, n = 1) Enterobacterales were utilized. Susceptibility tests (broth microdilution) were conducted with ceftazidime/avibactam, imipenem/relebactam and meropenem/vaborbactam, as well as their respective BL partner. Antimicrobial activity of all six agents was evaluated in the murine neutropenic thigh model using clinically relevant exposures. Efficacy was assessed as the change in bacterial growth at 24 h, compared with 0 h controls. On average, the three BL/BLI agents resulted in robust bacteria killing among OXA-48-negative isolates. Among OXA-48-positive isolates, poor in vivo activity with imipenem/relebactam was concordant with its resistant phenotypic profile. Variable meropenem/vaborbactam activity was observed among isolates with a 'susceptible' MIC of 4 mg/L. Only 30% (7/23) of isolates at meropenem/vaborbactam MICs of 2 and 4 mg/L met the ≥1 log bacterial reduction threshold predictive of clinical efficacy in serious infections. In contrast, ceftazidime/avibactam resulted in marked bacterial density reduction across the range of MICs and 73% (37/51) of isolates exceeded the ≥1 log bacterial reduction threshold. Data demonstrate that current imipenem/relebactam and ceftazidime/avibactam CLSI breakpoints are appropriate. Data also suggest that higher meropenem/vaborbactam breakpoints relative to meropenem can translate to potentially poor clinical outcomes in patients infected with OXA-48-harbouring isolates.

P05 In vivo efficacy of VRP-034 in lung and thigh infection models

BackgroundPolymyxin B-induced kidney injury is an important clinical concern that undermines patient care. This injury occurs in 30%–60% of patients receiving systemic polymyxin B (PMB). VRP-034, a novel PMB formulation, has previously shown a promising safety profile as compared with marketed PMB in animal models (Roy et al.1). The objective of this study was to assess the efficacy of VRP-034 versus marketed PMB in murine lung and thigh infection models.Materials and methods26 neutropenic BALB/c mice (n = 12 for lung; n = 14 for thigh) were infected by inoculating Pseudomonas aeruginosa (ATCC 27853, pathogenic, PMB MIC 0.5 μg/mL) either into the lungs (5 × 106 cfu) via intratracheal administration (lung model) or in both thighs (106 cfu/thigh) via intramuscular administration (thigh model). Treatment mice received VRP-034 or marketed PMB subcutaneously at 8 mg/kg every 8 h (HED: 2 mg/kg/day). Mice were humanely euthanized at 0 h (control) and at different timepoints post-treatment (24 h—lung model; 6 h and 12 h—thigh model). Lung or thigh tissues were collected, homogenized, serially diluted, plated on permissive media with cfu counted after 24 h of incubation. Changes in log10 cfu/mL at each timepoint were compared with 0 h control to assess efficacy.ResultsIn the lung infection model, the mean (±SEM) log10 cfu/mL increased from 8.01 ± 0.43 (at 0 h) to 12.02 ± 0.85 (at 24 h) in the vehicle control group. Treatment with marketed PMB and VRP-034 resulted in 1.96 ± 0.87 and 2.07 ± 0.42 log-reduction respectively in bacterial burden when compared with 0 h control. In the thigh infection model, the log10 cfu/mL increased from 6.40 ± 0.11 (at 0 h) to 9.85 ± 0.08 (at 6 h) and 11.23 ± 0.07 (at 12 h) in the vehicle control group. Treatment with marketed PMB reduced the bacterial burden by 0.65 ± 0.08 and 2.79 ± 0.14 log at 6 h and 12 h, respectively and treatment with VRP-034 reduced the bacterial burden by 0.85 ± 0.17 and 2.68 ± 0.01 log at 6 h and 12 h, respectively.ConclusionsThe results from the murine lung and thigh infection models suggest that there is no marked difference between the efficacy of VRP-034 and marketed PMB. Further work should explore the clinical utility of these findings in the light of the promising safety profile of VRP-034.

Discovery of Novel Pleuromutilin Derivatives as Potent Antibacterial Agents for the Treatment of MRSA Infection.

A series of novel pleuromutilin derivatives containing nitrogen groups on the side chain of C14 were synthesized under mild conditions. Most of the synthesized derivatives displayed potent antibacterial activities. Compound 9 was found to be the most active antibacterial derivative against MRSA (MIC = 0.06 μg/mL). Furthermore, the result of time-kill curves showed that compound 9 had a certain inhibitory effect against MRSA in vitro. Moreover, according to a surface plasmon resonance (SPR) study, compound 9 (KD = 1.77 × 10−8 M) showed stronger affinity to the 50S ribosome than tiamulin (KD = 2.50 × 10−8 M). The antibacterial activity of compound 9 was further evaluated in an MRSA-infected murine thigh model. Compared to the negative control group, tiamulin reduced MRSA load (~0.7 log10 CFU/mL), and compound 9 performed a treatment effect (~1.3 log10 CFU/mL). In addition, compound 9 was evaluated in CYP450 inhibition assay and showed only moderate in vitro CYP3A4 inhibition (IC50 = 2.92 μg/mL).

65. In Vivo Efficacy of Human Simulated Minocycline (MIN) against Stenotrophomonas maltophilia (STM)

BackgroundThe current susceptibility breakpoint for MIN against STM is 4mg/L, yielding >99% of isolates susceptible. Unfortunately, there are limited pre-clinical and clinical data to support this breakpoint for STM. The purpose of this study was to evaluate the efficacy of a MIN human simulated regimen (HSR) against STM across a wide range of MICs in the murine neutropenic thigh model.MethodsClinical STM with modal MIN MICS of 0.25-8mg/L were included. Confirmatory pharmacokinetic (PK) studies were performed in infected neutropenic mice to develop a MIN HSR providing an area under the curve (AUC) and maximum concentration (Cmax) exposure similar to MIN 100mg intravenous (IV) q12h at steady-state based on PK parameters from critically ill adult patients. The murine neutropenic thigh infection model was utilized to examine the antibacterial effects of the confirmed MIN HSR against 17 STM. Both thighs of neutropenic ICR mice were inoculated with bacterial suspensions of 107 colony forming units (CFU)/mL. Two hours after inoculation, the MIN HSR was administered subcutaneously (SC) over 24h. Control mice received normal saline. Efficacy was measured as the change in log10CFU/thigh at 24h compared with 0h controls.ResultsMIN 22, 10, 14, and 10mg/kg dosed SC at 0, 6, 12, and 18h best recapitulated the human Cmax and AUC profile. Mean ± standard deviation bacterial burden at 0h across all isolates was 6.03±0.32 log10CFU/thigh. Bacterial growth was 1.35±0.68 log10CFU/thigh in 24h controls. Six of 7 isolates (86%) with MIC ≤ 0.5mg/L achieved 1-log kill with MIN HSR (-1.44±1.37 log10CFU/thigh). All STM with MIC ≥ 1mg/L experienced bacterial growth (1.18±0.79 log10CFU/thigh) (Figure).Figure. Efficacy of a minocycline human simulated exposure of 100mg intravenous Q12h in the murine neutropenic thigh model against 17 clinical Stenotrophomonas maltophilia isolates ConclusionThese data describe the in vivo efficacy of a MIN HSR with exposures similar to MIN 100mg IV q12h in critically ill adults. Lack of antibacterial activity against STM with MICs ≥ 1mg/L justifies a reassessment of the current susceptibility breakpoint. The study was funded under FDA Contract 75F40120C00171. Disclosures David P. Nicolau, PharmD, Abbvie, Cepheid, Merck, Paratek, Pfizer, Wockhardt, Shionogi, Tetraphase (Other Financial or Material Support, I have been a consultant, speakers bureau member, or have received research funding from the above listed companies.) Joseph L. Kuti, PharmD, Allergan (Speaker’s Bureau)BioMérieux (Consultant, Research Grant or Support, Speaker’s Bureau)Contrafect (Scientific Research Study Investigator)GSK (Consultant)Merck (Research Grant or Support)Paratek (Speaker’s Bureau)Roche Diagnostics (Research Grant or Support)Shionogi (Research Grant or Support)Summit (Scientific Research Study Investigator)

Abstract 9197: Lesion Size and Adverse Event Profile of the TactiFlex™ Ablation Catheter, Sensor Enabled™ in a Porcine Thigh Model

Background: Advanced irrigated catheters, such as the FlexAbility™ Ablation Catheter, Sensor Enabled™ (FlexAbility SE), improve safety during RF ablation. Integration of contact force sensing technology with FlexAbility SE is clinically desirable to further enhance procedural efficacy and safety. Objective: To compare lesion size and adverse events in a perfused porcine thigh model for the TactiFlex™ Ablation Catheter, Sensor Enabled™ (TactiFlex SE) and its market-released predecessor, FlexAbility SE. Methods: Power controlled RF ablations were performed in 5 swine at either a nominal (30W, 60s; N=88) or maximum (50W, 10s; N=74) setting (20 g, 13 ml/min irrigation rate for all). Trials were balanced between parallel and perpendicular tip orientations. Coagulum formation, steam pops, char and lesion depth and width were documented. At each setting, lesion depth and width were assessed for equivalence between catheters (linear mixed model). Results for both orientations were pooled and adverse events were evaluated for non-inferiority of TactiFlex SE compared to FlexAbility SE (logistic regression). Results: Lesion depth and width were equivalent between TactiFlex SE and FlexAbility SE for all conditions (pre-specified- equivalence interval = ±1.67mm). TactiFlex SE was non-inferior to FlexAbility SE for rate of coagulum and char (pre-specified upper -non-inferiority margin = 20% ). No steam pops occurred with either catheter. Conclusion: The TactiFlex™ Ablation Catheter, Sensor Enabled™ produced equivalent lesion sizes and a favorable adverse event profile when compared to the FlexAbility™ Ablation Catheter, Sensor Enabled™ in a perfused porcine thigh model.

823 The ‘Blue Blood' Chicken Thigh Model: Microsurgery Simulation Teaching for Surgical Trainees

Abstract Introduction The simulation of microsurgery via various models helps surgical trainees to further their instrument handling and techniques. This model allows trainees to strengthen hand-microscope-eye coordination; a crucial ability required when handling critical vessels and tissues. The ‘Blue Blood’ Chicken Thigh Model imitates delicate vessels enabling the enhancement of dexterity. Aim To raise awareness amongst trainees in how the model may be used as a simulation tool for learning. To outline the arrangement of the ‘Blue Blood’ chicken thigh model allowing the practice of exceptionally fine suturing such as end-end anastomosis and end-side anastomosis. To improve trainee confidence in instrument handling and technique. Method A Microsurgery course was set up for maxillofacial surgical trainees within the West Midlands Deanery in November 2019. Detailed steps of dissecting the femoral vessels and preparing the ‘Blue Blood’ Chicken Thigh Model were presented. Microsurgical tools were then used to practise end-end and end-side anastomosis. Results The feedback received from the trainees was positive and it is hoped this will become an annual session for all trainees. Many trainees felt this was a resourceful tool to help them practise - even at home. Conclusions It is important for trainees to be able to display precise hand-eye movements especially when concerned with anastomosis techniques. This model will allow trainees to be able to simulate such an environment outside of theatre where they can spend time to hone skills and become comfortable with handling finer tissues and instruments.

3D Printed Chest Wall: A Tool for Advanced Microsurgical Training Simulating Depth and Limited View.

Summary:The deep inferior epigastric perforator (DIEP) flap has become the free flap of choice for autologous breast reconstruction. However, anastomoses of DIEP pedicles to internal mammary vessels in the chest wall are difficult due to restricted access and the depth of the vessels. Successful performance of such demanding procedures necessitates advanced requirements for microsurgical training models. The current chicken thigh model has been used to acquire microsurgical skills, allowing early learning curve trainees to practice repeatedly in inconsequential environments. Despite the increasing use of this model for training purposes, the resemblance to a clinical environment is tenuous. Such models should include anastomosis practice within the depth where the recipient vessels are located. To address this, we developed a three-dimensional (3D) printed chest wall as an addition to the current chicken thigh model, which reliably mimics the complexity of the anastomosis performed during DIEP breast reconstruction. This form of rapid prototyping facilitates a newfound ability for early learning curve trainees to exercise end-to-end anastomoses on vessels located with variable depths. Our enhancement of the current chicken thigh model is simple, cost-effective and offers a significantly more realistic resemblance to a clinical situation.

Phenotypic/Genotypic Profile of OXA-10-Like-Harboring, Carbapenem-Resistant Pseudomonas aeruginosa: Using Validated Pharmacokinetic/Pharmacodynamic In Vivo Models To Further Evaluate Enzyme Functionality and Clinical Implications.

In vitro MICs and in vivo pharmacodynamics of ceftazidime and cefepime human-simulated regimens (HSR) against modified carbapenem inactivation method (mCIM)-positive Pseudomonas aeruginosa isolates harboring different OXA-10-like subtypes were described. The murine thigh model assessed ceftazidime (2 g every 8 h [q8h] HSR) and cefepime (2 g and 1 g q8h HSR). Phenotypes were similar despite possessing OXA-10-like subtypes with differing spectra. Ceftazidime produced ≥1-log10 killing in all isolates. Cefepime activity was dose dependent and MIC driven. This approach may be useful in assessing the implications of β-lactamase variants.

Assessing the Relationship of Applied Force and Ablation Duration on Lesion Size Using a Diamond Tip Catheter Ablation System.

Background:Contact force has proven to be influential for lesion formation in power-controlled radiofrequency ablation. Lesion formation and morphology from a temperature-controlled diamond tip radiofrequency ablation catheter is not well described. We hypothesize that lesion formation from a temperature-controlled radiofrequency system is independent of applied force over short application durations.Methods:This study examined lesion depth, surface width, temperature, and ablation parameters of the DiamondTemp Ablation (Medtronic, Inc) system for ablation applications delivered with varying application duration (5, 10, and 15 s) and applied force (5, 10, and 30 g). Lesions from perpendicular radiofrequency applications were analyzed in a stepwise fashion from a computational model, thermochromic gel data (n=36), and porcine thigh preparation (n=231) experiments.Results:Varying applied force across each application duration consistently generated comparable lesion dimensions for each model. In the computational model, lesion depths from a 5 s application with 5, 10, and 30 g of applied force were similar (2.3, 2.6, and 3.0 mm, respectively). Also, the 5 s lesion depths in the gel model were consistent across applied force (5 g, 3.2±0.1 mm; 10 g, 3.5±0.1 mm; 30 g, 3.5±0.2 mm). In the thigh model, the 5, 10, and 30 g applied forces for 5 s created lesion depths of 3.1±0.5, 3.2±1.0, and 3.2±1.1 mm, respectively. For the 10 and 15 s durations, the lesion depth and width remained consistent for the 10 and 30 g applied forces. Increases in lesion depth and width, percentage of impedance reduction, minimum power, and maximum temperature were only significant when application duration increased (from 5 to 15 s).Conclusions:Lesion dimensions with the DiamondTemp Ablation temperature-controlled radiofrequency ablation system showed no marked change with increased applied force. Short application durations generated consistent lesion dimensions across computational, thermochromic gel, and thigh models.

Design, Synthesis, and Biological Evaluation of Novel Pyrimido[4,5-b]indole Derivatives Against Gram-Negative Multidrug-Resistant Pathogens.

Due to the poor permeability across Gram-negative bacterial membranes and the troublesome bacterial efflux mechanism, only a few GyrB/ParE inhibitors with potent activity against Gram-negative pathogens have been reported. Among them, pyrimido[4,5-b]indole derivatives represented by GP-1 demonstrated excellent broad-spectrum antibacterial activity against both Gram-positive and Gram-negative bacteria but were limited by hERG inhibition and poor pharmacokinetics profile. To improve their drug-like properties, we designed a series of novel pyrimido[4,5-b]indole derivatives based on the tricyclic scaffold of GP-1 and the C-7 moiety of acorafloxacin. These efforts have culminated in the discovery of a promising compound 18r with reduced hERG liability and an improved PK profile. Compound 18r exhibited superior broad-spectrum in vitro antibacterial activity compared to GP-1, including a variety of clinical multidrug G- pathogens, especially Acinetobacter baumannii, and the in vivo efficacy was also demonstrated in a neutropenic mouse thigh model of infection with multidrug-resistant A. baumannii.

Chicken or the thumb? Comparing chicken femora with human metacarpals

Introduction While the gold standard for simulation training in hand surgery is cadaveric hands, ethical issues and cost limit their use. Chicken thighbones have been utilised to replicate human metacarpals but there is a lack of literature to validate such a model. The aim of this study was to determine whether chicken femurs are morphologically similar to human metacarpal bones. Methods Computed tomography imaging was obtained of hands undertaken at our institute between 1 January and 31 December 2015. A total of 114 chicken thighs were also scanned. Bones with previous trauma or incomplete imaging were excluded. Bone length, distance to isthmus, radius of curvature, medullary canal diameter and cortical thickness were compared between the groups. Statistical analysis was conducted using Student’s t-test or the Mann-Whitney U test, with statistical significance implied with a p-value of < 0.05. Results A total of 146 human CT scans were identified, of which 36 were included in the study, resulting in 158 human metacarpals in 5 female and 31 male patients, with an average age of 39.5 years (range: 16–77 years). Of 114 chickens scanned, 101 were suitable for analysis. Mean length, distance to isthmus, radius of curvature, medullary canal diameter and cortical thickness were 57.3mm (standard deviation [SD]: 8.7mm), 32.9mm (SD: 8.2mm), 68.8mm (SD: 19.5mm), 9.3mm (SD: 1.6mm) and 1.7mm (SD: 0.4mm) respectively in human metacarpals, compared with 66.7mm (SD: 5.1mm), 34.1mm (SD: 6.4mm), 89.1mm (SD: 15.1mm), 6.4mm (SD: 0.6mm) and 1.6mm (SD: 0.1mm) respectively in chicken femurs. There was no significant difference in bone geometry between the groups, with p-values of >0.05 for all parameters described. Conclusions The chicken thigh model provides an anatomically suitable and more cost effective alternative to human cadaveric metacarpals in simulation training for hand surgery.

Design, synthesis, in vitro and in vivo evaluation against MRSA and molecular docking studies of novel pleuromutilin derivatives bearing 1, 3, 4-oxadiazole linker

A class of pleuromutilin derivatives containing 1, 3, 4-oxadiazole were designed and synthesized as potential antibacterial agents against Methicillin-resistant staphylococcus aureus (MRSA). The ultrasound-assisted reaction was proposed as a green chemistry method to synthesize 1, 3, 4-oxadiazole derivatives (intermediates 85–110). Among these pleuromutilin derivatives, compound 133 was found to be the strongest antibacterial derivative against MRSA (MIC = 0.125 μg/mL). Furthermore, the result of the time-kill curves displayed that compound 133 could inhibit the growth of MRSA in vitro quickly (- 4.36 log10 CFU/mL reduction). Then, compound 133 (- 1.82 log10 CFU/mL) displayed superior in vivo antibacterial efficacy than tiamulin (- 0.82 log10 CFU/mL) in reducing MRSA load in mice thigh model. Besides, compound 133 exhibited low cytotoxicity to RAW 264.7 cells. Molecular docking studies revealed that compound 133 was successfully localized in the binding pocket of 50S ribosomal subunit (ΔGb = -10.50 kcal/mol). The results indicated that these pleuromutilin derivatives containing 1, 3, 4-oxadiazole might be further developed into novel antibiotics against MRSA.

Discovery and Optimization of DNA Gyrase and Topoisomerase IV Inhibitors with Potent Activity against Fluoroquinolone-Resistant Gram-Positive Bacteria.

Herein, we describe the discovery and optimization of a novel series that inhibits bacterial DNA gyrase and topoisomerase IV via binding to, and stabilization of, DNA cleavage complexes. Optimization of this series led to the identification of compound 25, which has potent activity against Gram-positive bacteria, a favorable in vitro safety profile, and excellent in vivo pharmacokinetic properties. Compound 25 was found to be efficacious against fluoroquinolone-sensitive Staphylococcus aureus infection in a mouse thigh model at lower doses than moxifloxacin. An X-ray crystal structure of the ternary complex formed by topoisomerase IV from Klebsiella pneumoniae, compound 25, and cleaved DNA indicates that this compound does not engage in a water-metal ion bridge interaction and forms no direct contacts with residues in the quinolone resistance determining region (QRDR). This suggests a structural basis for the reduced impact of QRDR mutations on antibacterial activity of 25 compared to fluoroquinolones.

Semiautomatic Assessment of Fetal Fractional Limb Volume for Weight Prediction in Clinical Praxis: How Does It Perform in Routine Use?

Semiautomatic fractional limb volume (FLV) models have recently produced promising results for fetal birth weight (BW) estimation. We tested those models in a more unselected population hypothesizing that the FLV models would improve accuracy and precision of fetal BW estimation compared to the Hadlock model. We compared the performance of different BW prediction models: Hadlock (biparietal diameter [BPD], abdominal circumference (AC), femur diaphysis length) and modified Lee thigh volume (TVol) and arm volume (AVol) (BPD, AC, automated fractional TVol, and AVol). Accuracy (systematic errors, mean percent differences) and precision (random errors, ± 1 SD of percent differences) were calculated. A total of 75 fetuses were included for final analysis. The Hadlock model showed the most consistent results with accurate BW estimation not significantly different from zero (-0.37 ± 8.53%). The modified fractional thigh and arm volume models were less accurate but trended toward more precise results (-2.63 ± 7.69% and -3.85 ± 7.47%, respectively). In addition, the modified TVol model showed the trend to predict more BWs within ±10% of the actual BW compared to the Hadlock model (81.3 versus 74.67%, ns). Based on our results, fetal weight estimation using the modified semiautomatic FLV models generates less accurate results in third-trimester fetuses compared to the Hadlock model. Those models recently published might improve the results of BW prediction by showing a higher precision than conventional models, especially in small and large fetuses. Further studies are needed to investigate the clinical usefulness of the new models.

Design, synthesis and biological evaluation of novel pleuromutilin derivatives as potent anti-MRSA agents targeting the 50S ribosome

A series of novel pleuromutilin derivatives were designed and synthesized with 1,2,4-triazole as the linker connected to benzoyl chloride analogues under mild conditions. The in vitro antibacterial activities of the synthesized derivatives against four strains of Staphylococcus aureus (MRSA ATCC 43300, ATCC 29213, AD3 and 144) were tested by the broth dilution method. Most of the synthesized derivatives displayed potent activities, and 22-(3-amino-2-(4-methyl-benzoyl)-1,2,4-triazole-5-yl)-thioacetyl)-22-deoxypleuromutilin (compound 12) was found to be the most active antibacterial derivative against MRSA (MIC = 0.125 μg/mL). Furthermore, the time-kill curves showed compound 12 had a certain inhibitory effect against MRSA in vitro. The in vivo antibacterial activity of compound 12 was further evaluated using MRSA infected murine thigh model. Compound 12 exhibited superior antibacterial efficacy than tiamulin. It was also found that compound 12 had no significant inhibitory effect on the proliferation of RAW264.7 cells. Compound 12 was further evaluated in CYP450 inhibition assay and showed moderate inhibitory effect on CYP3A4 (IC50 = 3.95 μM). Moreover, seven candidate compounds showed different affinities with the 50S ribosome by SPR measurement. Subsequently, binding of compound 12 and 20 to the 50S ribosome was further investigated by molecular modeling. Three strong hydrogen bonds were formed through the interaction of compound 12 and 20 with 50S ribosome. The binding free energy of compound 12 and 20 with the ribosome was calculated to be −10.7 kcal/mol and −11.66 kcal/mol, respectively.

634 Utilizing Simulation Based Training to Teach Wound Management Strategies When Caring for Burns Treated with Autologous Skin Cell Suspension

Abstract Introduction Simulation based training (SBT) is an experience meant to replace real-life events with guided simulated clinical scenarios. The goal is fully interactive training that closely replicates the real world. SBT is well known in military and aviation and has been well integrated into the education of new nurses and physicians however, it has not been fully integrated into the ongoing development of skills for clinicians practicing in hospitals that are learning new technologies. Following FDA approval of a regenerative medicine platform that prepares autologous skin cell suspension (ASCS), an opportunity was identified to augment conventional training with a SBT educational program giving clinicians the opportunity to practice wound care in a simulated learning environment. Methods A prototype was developed alongside experts from a university-based experiential learning center. It included an anatomical silicone mold of a thigh (model) with silicone cartridges of ASCS treatment areas (excised deep partial-thickness burn with dermis and excised full-thickness burn with wide meshed split thickness skin graft). The cartridges fit in a depressed area of the thigh and can be exchanged between case scenarios. The cartridge allows for moulage to be applied, enhancing the life-like appearance of the model. The initial prototype was tested during a pilot with burn center staff. A total of 4 case scenarios related to ASCS aftercare were evaluated. Following the pilot, the program was demonstrated to our internal clinical team to gain additional insight. The feedback was incorporated into a final design. Results There were 17 participants in the pilot training (6 hands-on/11 observers). All hands-on participants either agreed or strongly agreed that SBT was useful to their clinical practice. Comments included: “Very realistic”, “really liked the hands-on”, “confidence booster”, “these are the most common scenarios we see”. One participant commented that even though she had never participated in an ASCS dressing change, she has the confidence to do so now. Soliciting feedback from our internal team on the design and portability of the model was an important step to ensure barriers to use were removed. To date, 11 training systems including models, cartridges, case scenarios, debrief tools and dressing kits have been distributed with a total of 30 systems expected by the end of 2020. Conclusions During development of the SBT program, input from clinicians and educators helped gain insight to the program and ensured the scenarios were relative to real-world experiences. Early findings suggest SBT is a value add for clinicians caring for patients post ASCS application.

Pharmacodynamics of Ceftibuten: An Assessment of an Oral Cephalosporin against Enterobacterales in a Neutropenic Murine Thigh Model.

Efforts to develop and pair novel oral β-lactamase inhibitors with existing β-lactam agents to treat extended spectrum β-lactamase (ESBL) and carbapenemase-producing Enterobacterales are gaining ground. Ceftibuten is an oral third-generation cephalosporin capable of achieving high urine concentrations; however, there are no robust data describing its pharmacodynamic profile. This study characterizes ceftibuten pharmacokinetics and pharmacodynamics in a neutropenic murine thigh infection model. Enterobacterales isolates expressing no known clinically-relevant enzymatic resistance (n = 7) or harboring an ESBL (n = 2) were evaluated. The ceftibuten minimum inhibitory concentrations (MICs) were 0.03–4 mg/L. Nine ceftibuten regimens, including a human-simulated regimen (HSR) equivalent to clinical ceftibuten doses of 300 mg taken orally every 8 h, were utilized to achieve various fT > MICs. A sigmoidal Emax model was fitted to fT > MIC vs. change in log10 CFU/thigh to determine the requirements for net stasis and 1-log10 CFU/thigh bacterial burden reduction. The growth of the 0 h and 24 h control groups was 5.97 ± 0.37 and 8.51 ± 0.84 log10 CFU/thigh, respectively. Ceftibuten HSR resulted in a -0.49 to -1.43 log10 CFU/thigh bacterial burden reduction at 24 h across the isolates. Stasis and 1-log10 CFU/thigh reduction were achieved with a fT > MIC of 39% and 67%, respectively. The fT > MIC targets identified can be used to guide ceftibuten dosage selection to optimize the likelihood of clinical efficacy.

Efficacy of a novel lantibiotic, CMB001, against MRSA.

To evaluate the efficacy of a novel lantibiotic, CMB001, against MRSA biofilms in vitro and in an in vivo experimental model of bacterial infection. Antibacterial activity of CMB001 was measured in vitro after its exposure to whole blood or to platelet-poor plasma. In vitro efficacy of CMB001 against a Staphylococcus aureus biofilm was studied using scanning electron microscopy. The maximum tolerable dose in mice was determined and a preliminary pharmacokinetic analysis for CMB001 was performed in mice. In vivo efficacy was evaluated in a neutropenic mouse thigh model of infection. CMB001 maintained its antibacterial activity in the presence of blood or plasma for up to 24 h at 37°C. CMB001 efficiently killed S. aureus within the biofilm by causing significant damage to the bacterial cell wall. The maximum tolerable dose in mice was established to be 10 mg/kg and could be increased to 30 mg/kg in mice pretreated with antihistamines. In neutropenic mice infected with MRSA, treatment with CMB001 reduced the bacterial burden with an efficacy equivalent to that of vancomycin. CMB001 offers potential as an alternative treatment option to combat MRSA. It will be of interest to evaluate the in vivo efficacy of CMB001 against infections caused by other pathogens, including Clostridioides difficile and Acinetobacter baumannii, and to expand its pharmacokinetic/pharmacodynamic parameters and safety profile.

1296. Efficacy of Human-Simulated Exposures of Meropenem/Vaborbactam (MVB) and Meropenem (MEM) against OXA-48 β-lactamase-producing Enterobacterales in the Neutropenic Murine Thigh Infection Model

BackgroundOXA-48 exhibits variable hydrolytic activity toward carbapenems, with imipenem and meropenem MICs, though increased, often reporting within the ‘susceptible’ or ‘intermediate’ ranges defined by CLSI and EUCAST. Although vaborbactam (VAB) does not enhance MEM activity against OXA-48, ~ 1/3 of OXA-48-producing Enterobacterales will test susceptible to MVB due to its higher breakpoint. Clinical implications of this discordance warrant investigation.Methods26 isolates harboring OXA-48 (n=24) and KPC (n=2) were evaluated in the neutropenic murine thigh model. MICs were determined in triplicate per CLSI. Human-simulated regimens of MVB (simulating doses of 2-2 g IV q 8 hours (h) over 3 h) and MEM (2 g IV q 8 h over 3 h) were administered resulting in similar f%T >MIC and fAUC as humans for MEM and VAB, respectively. Mice received MVB, MEM, or sham control for 24 h. Efficacy was assessed on the resulting overall change in mean± SD log10 CFU/thigh as well as the achievement of ≥ 1 log10 reduction as an established surrogate marker predictive of success for serious infections.ResultsMVB and MEM MICs ranged from 1- 64 and 2 - > 64 mg/L, respectively. Relative to 0 h control, the mean bacterial growth (mean ± SD, CFU/thigh) at 24 h in the untreated control mice was 2.69 ± 1.31. As anticipated for KPCs, MVB resulted in a mean bacterial reduction ≥ 1 log10 (-1.10 ± 0.26), whereas growth was observed on MEM (+1.45 ± 0.88). For all OXA-48 isolates, MVB resulted in variable bacterial densities ranging from -2.54 to +2.68, similarly MEM resulted in -2.18 to +2.66. Addition of vaborbactam did not enhance MEM activity for any isolate. For isolates with MVB MICs ≥ 16 (n=5), 8 (n=5, EUCAST breakpoint), 4 (n=9, CLSI breakpoint), and ≤ 2 (n=5) mg/L, 0%, 0%, 44%, and 60% of isolates treated with MVB or MEM achieved the target reduction of ≥ 1 log10 kill, respectively.ConclusionAcross the range of MICs evaluated, MVB and MEM humanized exposures in vivo resulted in similar reductions and growth in bacterial density for OXA-48-producing Enterobacterales. Moreover, these data highlight the poor efficacy of MVB for OXA-48 defined as susceptible using the current EUCAST and CLSI susceptibility criterion. Caution is therefore warranted when treating Enterobacterales testing susceptible to MVB without the genotypic profile.Disclosures David P. Nicolau, PharmD, Cepheid (Other Financial or Material Support, Consultant, speaker bureau member or has received research support.)Merck & Co., Inc. (Consultant, Grant/Research Support, Speaker’s Bureau)Wockhardt (Grant/Research Support)