https://ogma.newcastle.edu.au/vital/access/ /manager/Index ${session.getAttribute("locale")} 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:51195 Wed 28 Feb 2024 15:48:19 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:45284 Wed 26 Oct 2022 17:20:38 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:19079 Wed 20 May 2020 07:11:37 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:34293 Pseudomonas aeruginosa, Klebsiella pneumoniae, and Acinetobacter baumannii. However, when used in combination, clinically relevant concentrations of polymyxin B and SERMs displayed synergistic killing against the polymyxin-resistant P. aeruginosa, K. pneumoniae, and A. baumannii isolates as demonstrated by a ≥2–3 log10 decrease in bacterial count (CFU/ml) after 24 hours. The combination of polymyxin B with toremifene demonstrated very potent antibacterial activity against P. aeruginosa biofilms in an artificial sputum media assay. Moreover, polymyxin B combined with toremifene synergistically induced cytosolic green fluorescence protein release, cytoplasmic membrane depolarization, permeabilizing activity in a nitrocefin assay, and an increase of cellular reactive oxygen species from P. aeruginosa cells. In addition, scanning and transmission electron micrographs showed that polymyxin B in combination with toremifene causes distinctive damage to the outer membrane of P. aeruginosa cells, compared with treatments with each compound per se. In conclusion, the combination of polymyxin B and SERMs illustrated a synergistic activity against XDR Gram-negative pathogens, including highly polymyxin-resistant P. aeruginosa isolates, and represents a novel combination therapy strategy for the treatment of infections because of problematic XDR Gram-negative pathogens.]]> Wed 15 Dec 2021 16:08:26 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:2667 Wed 11 Apr 2018 16:03:13 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:17083 a, R_d and R_e rough LPS mutants. The SAR analysis enabled by the binding data suggested that, in addition to the important role played by the lipid A and core components of LPS, it is predominately the unique species- and strain-specific carbohydrate structure of the O-antigen polysaccharide that largely determines the binding affinity for AGP. Together, these data are consistent with the role of AGP in the binding and transport of LPS in plasma during acute-phase inflammatory responses to invading Gram-negative bacteria.]]> Wed 11 Apr 2018 11:39:50 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:19783 Wed 11 Apr 2018 11:37:08 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:36947 Pseudomonas aeruginosa (P. aeruginosa) in the lungs of cystic fibrosis patients makes eradication of infections with antibiotic therapy very difficult. The lipopeptide antibiotics polymyxin B and colistin are currently the last-resort therapies for infections caused by multidrug-resistant P. aeruginosa. In the present study, we investigated the antibacterial activity of a series of polymyxin lipopeptides (polymyxin B, colistin, FADDI-003, octapeptin A₃, and polymyxin A₂) against a panel of polymyxin-susceptible and polymyxin-resistant P. aeruginosa cystic fibrosis isolates grown under planktonic or biofilm conditions in artificial sputum and their interactions with sputum component biomolecules. In sputum media under planktonic conditions, the lipopeptides FADDI-003 and octapeptin A₃ displayed very promising activity against the polymyxin-resistant isolate FADDI-PA066 (polymyxin B minimum inhibitory concentration (MIC) = 32 mg/L), while retaining their activity against the polymyxin-sensitive strains FADDI-PA021 (polymyxin B MIC = 1 mg/L) and FADDI-PA020 (polymyxin B MIC = 2 mg/L). Polymyxin A₂ was only effective against the polymyxin-sensitive isolates. However, under biofilm growth conditions, the hydrophobic lipopeptide FADDI-003 was inactive compared to the more hydrophilic lipopeptides, octapeptin A₃, polymyxin A₂, polymyxin B, and colistin. Transmission electron micrographs revealed octapeptin A₃ caused reduction in the cell numbers in biofilm as well as biofilm disruption/“antibiofilm” activity. We therefore assessed the interactions of the lipopeptides with the component sputum biomolecules, mucin, deoxyribonucleic acid (DNA), surfactant, F-actin, lipopolysaccharide, and phospholipids. We observed the general trend that sputum biomolecules reduce lipopeptide antibacterial activity. Collectively, our data suggests that, in the airways, lipopeptide binding to component sputum biomolecules may reduce antibacterial efficacy and is dependent on the physicochemical properties of the lipopeptide.]]> Wed 09 Mar 2022 15:59:20 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:52176 Wed 04 Oct 2023 11:04:42 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:41403 Wed 03 Aug 2022 10:42:28 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:55147 256 mg/L) revealed modified expression of several genes related to membrane transport (porin ompK36 and efflux pump regulator oqxR) and nitroreductase activity (ribC and nfsB, involved in nitrofurantoin reduction). Untargeted metabolomics analysis of total metabolites extracted at 1 and 4 h post-nitrofurantoin treatment revealed that exposure to the drug caused a delayed effect on the metabolome which was most pronounced after 4 h. Pathway enrichment analysis illustrated that several complex interrelated metabolic pathways related to nitrofurantoin bacterial killing (aminoacyl-tRNA biosynthesis, purine metabolism, central carbohydrate metabolism, and pantothenate and CoA biosynthesis) and the development of nitrofurantoin resistance (riboflavin metabolism) were significantly perturbed. This study highlights for the first time the key role of efflux pump regulator oqxR in nitrofurantoin resistance and reveals global metabolome perturbations in response to nitrofurantoin, in K. pneumoniae.]]> Tue 16 Apr 2024 15:16:15 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:34464 in vivo. Collectively, these results indicate that autophagy triggered by DAMPs during lung I/R injury amplifies the inflammatory response through enhancing K63-linked ubiquitination of TRAF6 and activation of the downstream MAPK and NF-κB signaling.]]> Tue 03 Sep 2019 18:27:11 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:34845 Thu 28 Oct 2021 12:35:34 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:25164 Pseudomonas aeruginosa. The in vitro synergistic activity of polymyxin B combined with ivacaftor or lumacaftor was assessed using checkerboard and static time-kill assays against a panel of polymyxin-susceptible and polymyxin-resistant P. aeruginosa isolates from the lungs of CF patients. Polymyxin B, ivacaftor, and lumacaftor were ineffective when used individually against polymyxin-resistant (MIC ≥ 4 mg/L) isolates. However, when used together, the combination of clinically relevant concentrations of polymyxin B (2 mg/L) combined with ivacaftor (8 mg/L) or ivacaftor (8 mg/L) + lumacaftor (8 mg/L) displayed synergistic killing activity against polymyxin-resistant P. aeruginosa isolates as demonstrated by a 100-fold decrease in the bacterial count (CFU/mL) even after 24 h. The combinations also displayed excellent antibacterial activity against P. aeruginosa under CF relevant conditions in a sputum medium assay. The combination of lumacaftor (alone) with polymyxin B showed additivity against P. aeruginosa. The potential antimicrobial mode of action of the combinations against P. aeruginosa was investigated using different methods. Treatment with the combinations induced cytosolic GFP release from P. aeruginosa cells and showed permeabilizing activity in the nitrocefin assay, indicating damage to both the outer and inner Gram-negative cell membranes. Moreover, scanning and transmission electron micrographs revealed that the combinations produce outer membrane damage to P. aeruginosa cells that is distinct from the effect of each compound per se. Ivacaftor was also shown to be a weak inhibitor of the bacterial DNA gyrase and topoisomerase IV with no effect on either human type I or type IIα topoisomerases. Lumacaftor displayed the ability to increase the cellular production of damaging reactive oxygen species. In summary, the combination of polymyxin B with KALYDECO or ORKAMBI exhibited synergistic activity against highly polymyxin-resistant P. aeruginosa CF isolates and can be potentially useful for otherwise untreatable CF lung infections.]]> Thu 04 Nov 2021 10:40:12 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:19082 Sat 24 Mar 2018 08:05:20 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:19306 Sat 24 Mar 2018 07:50:00 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:27252 in vitro microbiological assays. We show that fibrinogen, complement C4, haptoglobulin, α-1-antitrypsin, fibronectin, transferrin, immunoglobulin G, hemopexin, and humans serum albumin are responsible for the majority of the sequestering activity in plasma. No binding was observed to α-1-acid-glycoprotein. The findings of this study have broad reaching implications for antibiotic drug design and for dose tailoring to suit the plasma protein levels of individual patients in order to maximize the clinical efficacy of important first-line antibiotics such as ertapenem.]]> Sat 24 Mar 2018 07:29:09 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:28305 97%) to plasma proteins, there is the strong possibility that co-administered CF drugs may compete for the same plasma protein binding sites and impact the free drug concentration. This, in turn, could lead to drastic changes in the in vivo efficacy of ivacaftor and therapeutic outcomes. This biochemical study compares the binding affinity of ivacaftor and co-administered CF drugs for human serum albumin (HSA) and α₁-acid glycoprotein (AGP) using surface plasmon resonance and fluorimetric binding assays that measure the displacement of site-selective probes. Because of their ability to strongly compete for the ivacaftor binding sites on HSA and AGP, drug–drug interactions between ivacaftor are to be expected with ducosate, montelukast, ibuprofen, dicloxacillin, omeprazole, and loratadine. The significance of these plasma protein drug–drug interactions is also interpreted in terms of molecular docking simulations. This in vitro study provides valuable insights into the plasma protein drug–drug interactions of ivacaftor with co-administered CF drugs. The data may prove useful in future clinical trials for a staggered treatment that aims to maximize the effective free drug concentration and clinical efficacy of ivacaftor.]]> Sat 24 Mar 2018 07:27:06 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:22095 Sat 24 Mar 2018 07:15:17 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:45522 Acinetobacter baumannii, Klebsiella pneumoniae, and Pseudomonas aeruginosa. The combination of polymyxin B and sertraline showed synergistic antibacterial activity in checkerboard and static time-kill assays at clinically relevant concentrations against both polymyxin-susceptible and polymyxin-resistant isolates. The potential antimicrobial mode of action of the combination was investigated against P.aeruginosa FADDI-PA024 using untargeted metabolomics alongside scanning and transmission electron microscopy (EM). Scanning and transmission EM revealed that the polymyxin B and sertraline combination resulted in greater damage to the bacterial cell compared to each drug alone. Metabolomics results showed that the combination significantly affected the bacterial ability to remodel its outer membrane. This was reflected by the major perturbation of glycerophospholipids and fatty acids and the pantothenate and coenzyme A (CoA) pathways, which feed fatty acid elongation (e.g., trans-hexadec-2-enoyl-CoA) as well as inhibit the biosynthesis of lipopolysaccharide and peptidoglycan. The combination also inhibited the polymyxin resistance phosphoethanolamine (pEtN) lipid A modification pathway, indicated by the declined levels of phosphoethanolamine. In summary, the present study highlights the potential possibilities of a polymyxin-sertraline combination for the treatment of infections caused by multidrug resistant Gram-negative bacteria such as central nervous system (CNS) infections via direct intraventricular/intrathecal delivery.]]> Mon 31 Oct 2022 14:09:59 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:52959 Mon 29 Jan 2024 18:42:22 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:46649 2NP) following environmental exposure. At present, the consequences of TiO₂NP exposure in bone are not well known. The aim of this study was to investigate the effects of TiO₂NP on mesenchymal stem cells (MSCs) and potential underlying mechanisms. Mesenchymal bone marrow-derived cells were cultured and treated with various concentrations of TiO₂NP. Results showed that TiO₂NP incubation produced cytotoxicity as evidenced by reduced cell viability. Using Western blotting TiO₂NP was found to increase autophagy as determined by elevation in ratio of LC3-II from LC3-I without evidence of necrotic cell death as estimated by lactic dehydrogenase (LDH) level. TiO2NP produced a rise in intracellular reactive oxygen species (ROS) levels. The observed alterations in autophagy and oxidant stress were associated with upregulation of protein expression of p38, JNK, and ERK. Data indicate that TiO₂NP-mediated decrease in MSC survival involves a complex series of events associated stimulation of mitogen-activated protein kinase (MAPK) pathway and consequent autophagy and oxidative damage.]]> Mon 28 Nov 2022 17:22:23 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:25757 Mon 23 Jan 2017 12:23:41 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:17366 Mon 15 Jan 2024 14:36:47 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:54174 Mon 12 Feb 2024 09:35:16 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:40845 Mon 08 Aug 2022 15:39:55 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:39571 Mon 08 Aug 2022 11:34:21 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:42820 Mon 05 Sep 2022 11:35:27 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:42239 Fri 26 Aug 2022 09:43:19 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:51933 Fri 22 Sep 2023 11:06:44 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:31380 Pseudomonas aeruginosa using neutron reflectometry, together with fluorimetric and calorimetry methods. For the first time, our neutron reflectometry results reveal that the interaction of octapeptin A3 with the Gram-negative outer membrane involves an initial transient polar interaction with the phospholipid and lipid A headgroups, followed by the penetration of the entire octapeptin molecule into the fatty acyl core of the outer membrane. This mechanism contrasts with that of polymyxin B, which specifically targets lipid A, whereas octapeptins appear to target both lipid A and phospholipids. Furthermore, the mechanism of octapeptins does not appear to be highly dependent on an initial complementary electrostatic interaction with lipid A, which accounts for their ability to bind to lipid A of polymyxin-resistant Gram-negative bacteria that is modified with cationic moieties that act to electrostatically repel the cationic polymyxin molecule. The presented findings shed new light on the mechanism whereby octapeptins penetrate the outer membrane of polymyxin-resistant Gram-negative pathogens and highlight their potential as candidates for development as new antibiotics against problematic multi-drug-resistant pathogens.]]> Fri 18 Sep 2020 14:00:17 AEST ]]>