Pharmacodynamics of Piperacillin-Tazobactam/Amikacin Combination versus Meropenem against Extended-Spectrum ß-Lactamase-Producing Escherichia coli in a Hollow Fiber Infection Model.

Carbapenems are recommended for the treatment of urosepsis caused by extended-spectrum ß-lactamase (ESBL)-producing, multidrug-resistant Escherichia coli; however, due to selection of carbapenem resistance, there is an increasing interest in alternative treatment regimens including the use of ß-lactam-aminoglycoside combinations. We compared the pharmacodynamic activity of piperacillin-tazobactam and amikacin as mono and combination therapy versus meropenem monotherapy against extended-spectrum ß-lactamase (ESBL)-producing, piperacillin-tazobactam resistant E. coli using a dynamic hollow fiber infection model (HFIM) over 7 days. Broth-microdilution was performed to determine the MIC of E. coli isolates. Whole genome sequencing was conducted. Four E. coli isolates were tested in HFIM with an initial inoculum of ~107 CFU/mL. Dosing regimens tested were piperacillin-tazobactam 4.5 g, 6-hourly, plus amikacin 30 mg/kg, 24-hourly, as combination therapy, and piperacillin-tazobactam 4.5 g, 6-hourly, amikacin 30 mg/kg, 24-hourly, and meropenem 1 g, 8-hourly, each as monotherapy. We observed that piperacillin-tazobactam and amikacin monotherapy demonstrated initial rapid bacterial killing but then led to amplification of resistant subpopulations. The piperacillin-tazobactam/amikacin combination and meropenem experiments both attained a rapid bacterial killing (~4-5 log10) within 24 h and did not result in any emergence of resistant subpopulations. Genome sequencing demonstrated that all ESBL-producing E. coli clinical isolates carried multiple antibiotic resistance genes including blaCTX-M-15, blaOXA-1, blaEC, blaTEM-1, and aac(6')-Ib-cr. These results suggest that the combination of piperacillin-tazobactam/amikacin may have a potential role as a carbapenem-sparing regimen, which should be tested in future urosepsis clinical trials.

Evaluation of the stability of ceftazidime/avibactam in elastomeric infusion devices used for outpatient parenteral antimicrobial therapy utilizing a national stability protocol framework.

Objectives: To evaluate the stability of ceftazidime/avibactam in elastomeric infusers, utilizing the UK's Yellow Cover Document (YCD) stability testing framework, in conditions representative of OPAT practice. Methods: Ceftazidime/avibactam was reconstituted with sodium chloride 0.9% (w/v) in two elastomeric infusers at concentrations (dose) levels of 1500/375, 3000/750 and 6000 mg/1500 mg in 240 mL. The infusers were exposed to a fridge storage (2°C-8°C) for 14 days followed by 24 h in-use temperature (32°C). Results: After 14 days of fridge storage and subsequent 24 h exposure to 32°C, mean ±â€ŠSD of ceftazidime percent remaining was 75.5% ±â€Š1.8%, 79.9% ±â€Š1.1%, 82.4% ±â€Š0.6%, for Easypump, and 81.7% ±â€Š1.2%, 82.5% ±â€Š0.5%, 85.4% ±â€Š1.1% for Dosi-Fuser devices at the high, intermediate and low doses tested, respectively. For avibactam, mean ±â€ŠSD percent remaining was 83.2% ±â€Š1.8%, 87.4% ±â€Š2.0%, 93.1% ±â€Š0.9% for Easypump, and 85.1% ±â€Š2.0%, 86.7% ±â€Š0.1%, 92.5% ±â€Š0.1% for Dosi-Fuser devices. The cumulative amount of pyridine generated in the devices ranged from 10.4 mg at low dose to 76.9 mg at high dose. Regression-based simulation showed that the degradation of both ceftazidime and avibactam was <10% for at least 12 h of the running phase, if stored in a fridge for not more than 72 h prior to in-use temperature exposure. Conclusions: Whilst not meeting the strict UK YCD criteria for ≤5% degradation, ceftazidime/avibactam may be acceptable to administer as a continuous 12 hourly infusion in those territories where degradation of ≤10% is deemed acceptable.

COVID-19 Drug Treatments Are Prone to Sequestration in Extracorporeal Membrane Oxygenation Circuits: An Ex Vivo Extracorporeal Membrane Oxygenation Study.

Drug treatments for coronavirus disease 2019 (COVID-19) dramatically improve patient outcomes, and although extracorporeal membrane oxygenation (ECMO) has significant use in these patients, it is unknown whether ECMO affects drug dosing. We used an ex vivo adult ECMO model to measure ECMO circuit effects on concentrations of specific COVID-19 drug treatments. Three identical ECMO circuits used in adult patients were set up. Circuits were primed with fresh human blood (temperature and pH maintained within normal limits). Three polystyrene jars with 75 ml fresh human blood were used as controls. Remdesivir, GS-441524, nafamostat, and tocilizumab were injected in the circuit and control jars at therapeutic concentrations. Samples were taken from circuit and control jars at predefined time points over 6 h and drug concentrations were measured using validated assays. Relative to baseline, mean (± standard deviation [SD]) study drug recoveries in both controls and circuits at 6 h were significantly lower for remdesivir (32.2% [±2.7] and 12.4% [±2.1], p < 0.001), nafamostat (21.4% [±5.0] and 0.0% [±0.0], p = 0.018). Reduced concentrations of COVID-19 drug treatments in ECMO circuits is a clinical concern. Remdesivir and nafamostat may need dose adjustments. Clinical pharmacokinetic studies are suggested to guide optimized COVID-19 drug treatment dosing during ECMO.

Stability of nafamostat in intravenous infusion solutions, human whole blood and extracted plasma: implications for clinical effectiveness studies.

Aim: To describe the stability of nafamostat in infusion solutions, during blood sample collection and in extracted plasma samples in the autosampler. Methods: Nafamostat infusion solutions were stored at room temperature in the light for 24 h. For sample collection stability, fresh blood spiked with nafamostat was subjected to combinations of anticoagulants, added esterase inhibitor and temperature. Nafamostat was monitored in the extracted plasma samples in the autosampler. Results: Nafamostat was stable in infusion solutions. Nafamostat in whole blood was stable for 3 h before centrifugation when collected in sodium fluoride/potassium oxalate tubes (4°C). Nafamostat in extracted plasma samples degraded at 4.7 ± 0.7% per h. Conclusion: Viable samples can be obtained using blood collection tubes with sodium fluoride, chilling and processing promptly.

Involvement of small GTPase RhoA in the regulation of superoxide production in BV2 cells in response to fibrillar Aß peptides.

Fibrillar amyloid-beta (fAß) peptide causes neuronal cell death, which is known as Alzheimer's disease. One of the mechanisms for neuronal cell death is the activation of microglia which releases toxic compounds like reactive oxygen species (ROS) in response to fAß. We observed that fAß rather than soluble form blocked BV2 cell proliferation of microglial cell line BV2, while N-acetyl-l-cysteine (NAC), a scavenger of superoxide, prevented the cells from death, suggesting that cell death is induced by ROS. Indeed, both fAß1-42 and fAß25-35 induced superoxide production in BV2 cells. fAß25-35 produced superoxide, although fAß25-35 is not phagocytosed into BV2 cells. Thus, superoxide production by fAß does not seem to be dependent on phagocytosis of fAß. Herein we studied how fAß produces superoxide in BV2. Transfection of dominant negative (DN) RhoA (N19) cDNA plasmid, small hairpin (sh)-RhoA forming plasmid, and Y27632, an inhibitor of Rho-kinase, abrogated the superoxide formation in BV2 cells stimulated by fAß. Furthermore, fAß elevated GTP-RhoA level as well as Rac1 and Cdc42. Tat-C3 toxin, sh-RhoA, and Y27632 inhibited the phosphorylation of p47(PHOX). Moreover, peritoneal macrophages from p47(PHOX) (-/-) knockout mouse could not produce superoxide in response to fAß. These results suggest that RhoA closely engages in the regulation of superoxide production induced by fAß through phosphorylation of p47(PHOX) in microglial BV2 cells.

Interaction of microglia and amyloid-beta through beta2-integrin is regulated by RhoA.

Amyloid-beta (Abeta) is one of the main factors to cause Alzheimer's disease. Although fibrillar Abeta (fAbeta) activates microglial cells that release toxic compounds to induce partial neuronal death, the mechanism of interaction between Abeta and microglia remains unclear. Therefore, we examined the interaction of microglial cells (BV2) and fAbeta on a gelatin-precoated plate. The binding was markedly enhanced by RhoA inactivation using Tat-C3, dominant negative RhoA, and si-RhoA. To identify the receptor for fAbeta, we tested various antibodies to mask receptors. Among them, anti-beta2-integrin antibody mostly suppressed cell binding to fAbeta. The incremental binding of cells induced by RhoA inhibition was also blocked by addition of anti-beta2-integrin antibody. These results suggest that RhoA inhibition stimulates beta2-integrin-mediated cell interaction to fAbeta.

Transforming growth factor-beta1 regulates macrophage migration via RhoA.

Brief treatment with transforming growth factor (TGF)-beta1 stimulated the migration of macrophages, whereas long-term exposure decreased their migration. Cell migration stimulated by TGF-beta1 was markedly inhibited by 10 mug/mL Tat-C3 exoenzyme. TGF-beta1 increased mRNA and protein levels of macrophage inflammatory protein (MIP)-1alpha in the initial period, and these effects also were inhibited by 10 mug/mL Tat-C3 and a dominant-negative (DN)-RhoA (N19RhoA). Cycloheximide, actinomycin D, and antibodies against MIP-1alpha and monocyte chemoattractant protein-1 (MCP-1) abolished the stimulation of cell migration by TGF-beta1. These findings suggest that migration of these cells is regulated directly and indirectly via the expression of chemokines such as MIP-1alpha and MCP-1 mediated by RhoA in response to TGF-beta1. TGF-beta1 activated RhoA in the initial period, and thereafter inactivated them, suggesting that the inactivation of RhoA may be the cause of the reduced cell migration in response to TGF-beta1 at later times. We therefore attempted to elucidate the molecular mechanism of the inactivation of RhoA by TGF-beta1. First, TGF-beta1 phosphorylated RhoA via protein kinase A, leading to inactivation of RhoA. Second, wild-type p190 Rho GTPase activating protein (p190RhoGAP) reduced and DN-p190RhoGAP reversed the reduction of cell migration induced by TGF-beta, suggesting that it inactivated RhoA via p190 Rho GAP.