Inhibition Of Efflux Research Articles

Identifying how drug efflux mechanisms impact Acinetobacter baumannii evolutionary paths to ciprofloxacin resistance

Acinetobacter baumannii is a multi-drug resistant pathogen commonly found in clinical settings. This pathogen frequently uses efflux pumps to mitigate antibiotic treatment stress and eliminate the drug. When A. baumannii is exposed to antibiotics, it often develops mutations in the efflux pump regulator genes, causing an increase in efflux pump production. We hypothesize that efflux is a key pathway that leads to treatment failure in A. baumannii infections. The extent to which increasing drug efflux impacts other cellular functions remains unknown. To identify how efflux pump mutations impact growth, resistance, and evolvability, wildtype A. baumannii laboratory strain 17978UN, along with four mutants of this strain, each with a single nucleotide polymorphism (SNP) in an efflux pump regulator (adeL L341R, adeN I49N, adeR D23Y, and adeS R152S), were propagated in the presence of antibiotic and an efflux pump inhibitor to place selective pressure on the isolates. SNPs increase the production of efflux pumps; inhibiting efflux ability will determine if the effect of each SNP is nullified. All evolved populations demonstrated differences in fitness and antibiotic resistance in comparison to their respective ancestors; the extent of adaptation affecting each phenotype was highly dependent on the regulator that was mutated. Counterintuitively, efflux inhibitors also placed stress on wild-type A. baumannii which leads to antibiotic resistance. These results demonstrate that efflux regulator mutations can influence population adaptability and cause treatment failure. Understanding the role that different efflux systems play in treatment failure and drug resistance evolution will be instrumental in developing treatment strategies that hinder the development of antibiotic resistance.

Astrocyte aquaporin mediates a tonic water efflux maintaining brain homeostasis.

Brain water homeostasis not only provides a physical protection, but also determines the diffusion of chemical molecules key for information processing and metabolic stability. As a major type of glia in brain parenchyma, astrocytes are the dominant cell type expressing aquaporin water channel. How astrocyte aquaporin contributes to brain water homeostasis in basal physiology remains to be understood. We report that astrocyte aquaporin 4 (AQP4) mediates a tonic water efflux in basal conditions. Acute inhibition of astrocyte AQP4 leads to intracellular water accumulation as optically resolved by fluorescence-translated imaging in acute brain slices, and in vivo by fiber photometry in mobile mice. We then show that aquaporin-mediated constant water efflux maintains astrocyte volume and osmotic equilibrium, astrocyte and neuron Ca2+ signaling, and extracellular space remodeling during optogenetically induced cortical spreading depression. Using diffusion-weighted magnetic resonance imaging (DW-MRI), we observed that in vivo inhibition of AQP4 water efflux heterogeneously disturbs brain water homeostasis in a region-dependent manner. Our data suggest that astrocyte aquaporin, though bidirectional in nature, mediates a tonic water outflow to sustain cellular and environmental equilibrium in brain parenchyma.

Astrocyte aquaporin mediates a tonic water efflux maintaining brain homeostasis

Brain water homeostasis not only provides a physical protection, but also determines the diffusion of chemical molecules key for information processing and metabolic stability. As a major type of glia in brain parenchyma, astrocytes are the dominant cell type expressing aquaporin water channel. How astrocyte aquaporin contributes to brain water homeostasis in basal physiology remains to be understood. We report that astrocyte aquaporin 4 (AQP4) mediates a tonic water efflux in basal conditions. Acute inhibition of astrocyte AQP4 leads to intracellular water accumulation as optically resolved by fluorescence-translated imaging in acute brain slices, and in vivo by fiber photometry in mobile mice. We then show that aquaporin-mediated constant water efflux maintains astrocyte volume and osmotic equilibrium, astrocyte and neuron Ca2+ signaling, and extracellular space remodeling during optogenetically induced cortical spreading depression. Using diffusion-weighted magnetic resonance imaging (DW-MRI), we observed that in vivo inhibition of AQP4 water efflux heterogeneously disturbs brain water homeostasis in a region-dependent manner. Our data suggest that astrocyte aquaporin, though bidirectional in nature, mediates a tonic water outflow to sustain cellular and environmental equilibrium in brain parenchyma.

Liposomal formulation with thiazolic compounds against bacterial efflux pumps

This study aimed to evaluate the effects of liposome-encapsulated eugenol-based thiazolic derivatives against efflux pump-carrying bacteria. The Minimum Inhibitory Concentration (MIC) was determined to evaluate the antibacterial activity and antibiotic potentiation against Pseudomonas aeruginosa and Staphylococcus aureus, as well as to analyze the inhibition of efflux pumps in S. aureus strains 1199B and K2068 in the ethidium bromide assay. The direct antibacterial activity analysis showed no clinically relevant results since the compounds presented MICs ≥1024 µg/mL. Regarding the analysis of antibiotic potentiation against multidrug-resistant (MDR) strains of S. aureus, compound LF16 reduced norfloxacin MIC from 128 µg/mL to 64 µg/mL. All associated with gentamicin caused a significant antibiotic MIC reduction. None of the compounds could potentate the activity of norfloxacin against P. aeruginosa. However, all of them potentiated the activity of gentamicin against the same strain. Only the LF 26 caused a significant MIC reduction in the ethidium bromide assay, suggesting efflux inhibition in the S. aureus 1199B strain. Similar results were observed with the K2068 strain. Observing antibiotic MIC reduction S. aureus strains carrying the NorA and MepA proteins brought additional evidence of efflux pump inhibition. Our results indicate that while eugenol-based thiazoles didn’t exhibit direct activity, they can potentiate the antibiotics activity against MDR strains of P. aeruginosa and S. aureus. Among them, compound LF 26 potentiated the inhibitory effects of ethidium bromide and antibiotics against S. aureus strains carrying the NorA and MepA proteins, indicating a potential role of this class of compounds as efflux pump inhibitors.

A CC-Type Glutaredoxins GRX480 Functions in Cadmium Tolerance by Maintaining Redox Homeostasis in Arabidopsis.

Cadmium (Cd) toxicity causes oxidative stress damage in plant cells. Glutaredoxins (GRXs), a type of small oxidoreductase, play a crucial role in modulating thiol redox states. However, whether GRXs act in Cd stress remains to be identified. Here, we reveal that Arabidopsis GRX480, a member of the CC-type family, enhances plant Cd stress tolerance. The GRX480 mutants exhibit enhanced sensitivity to Cd stress, manifested by shortened root, reduced biomass, lower chlorophyll and proline levels, and decreased photosynthetic efficiency compared with the wild type. The Cd concentration in GRX480 mutants is higher than the wild type, resulting from the inhibition of Cd efflux and transport genes transcription. Lower levels of GSH were detected in Cd-treated GRX480 mutants than in the wild type, indicating that GRX480 regulates plant Cd tolerance by influencing the balance between GSH and GSSG. Furthermore, the hyperaccumulation of reactive oxygen species (ROS) is associated with decreased expression of H2O2 scavenging genes in Cd-treated GRX480 mutants. Additionally, more toxic reactive carbonyl species (RCS), produced during oxidative stress, accumulate in Cd-treated GRX480 mutants than in wild type. Overall, our study establishes a critical role of GRX480 in response to Cd stress, highlighting its multifaceted contributions to detoxification and the maintenance of redox homeostasis.

Cell-Based Screen Identifies a Highly Potent and Orally Available ABCB1 Modulator for Treatment of Multidrug Resistance.

Targeting ABCB1 is a promising strategy in combating multidrug resistance. Our cell-based phenotypic screening led to the discovery of novel triazolo[1,5-a]pyrimidone-based ABCB1 modulators. Notably, WS-917 was identified as a significant contributor to heightened sensitization of human colorectal adenocarcinoma cells (SW620/Ad300) to paclitaxel (IC50 = 5 nM). Mechanistic elucidation revealed that this compound substantially augmented intracellular paclitaxel and [3H]-paclitaxel, concurrently mitigating the efflux of [3H]-paclitaxel in SW620/Ad300 through the inhibition of ABCB1 efflux. The cellular thermal shift assay underscored its ability to stabilize ABCB1 through direct binding. Additionally, WS-917 induced stimulation of ABCB1 ATPase activity while exhibiting negligible inhibitory effect against CYP3A4. Remarkable was its capacity to enhance the sensitivity of SW620/Ad300 to paclitaxel, as well as the sensitivity of CT26/TAXOL to paclitaxel and PD-L1 inhibitor (Atezolizumab) in vivo, all achieved without inducing observable toxicity. The discovery of WS-917 holds promise for the development of more potent ABCB1 modulators.

Exploration of vanoxerine analogues as antibacterial agents.

Mycobacterium tuberculosis is a bacterial pathogen, responsible for approximately 1.3 million deaths in 2022 through tuberculosis infections. The complex treatment regimen required to treat tuberculosis and growing rates of drug resistance, necessitates the development of new anti-mycobacterial agents. One approach is to repurpose drugs from other clinical applications. Vanoxerine (GBR 12909) was previously shown to have anti-mycobacterial activity, through dissipating the membrane electric potential and hence, cellular energetics. Several vanoxerine analogues were synthesised in this study, which exhibited a range of activities against mycobacteria and enterococcus. All active analogues had similar impacts on the membrane electric potential and inhibition of ethidium bromide efflux. The most active compound displayed reduced inhibitory activity against the known human target of vanoxerine, the dopamine transporter. This work has identified a promising analogue, which could provide a starting point for further medicinal chemistry and drug development efforts to target mycobacteria.

Prediction of structure of mycobacterial efflux pump protein Rv0194 and molecular dynamics simulation of the predicted structures

Tuberculosis is a major cause of morbidity and mortality primarily in developing nations. The rising number of cases of multidrug resistance and extensive drug resistance are a critical concern for the management of the condition. Even though new antibiotics are being developed, eventually there are also strains that are resistant to them. The evolution of resistance in Mycobacterium tuberculosis is significantly influenced by drug efflux caused by efflux pumps. Rv0194 is an important efflux pump associated with resistance to multiple drugs like beta lactam antibiotics like ampicillin and also erythromycin and novobiocin. The introduction of efflux inhibitors for Rv0194 could shorten the course of current therapy and improve the efficacy of second-line medications. Building a trustworthy molecular model of this efflux pump is the goal of this study. We created 3 models using different modeling tools. These models were then subjected to a 20 ns molecular dynamics simulation in a lipid bilayer. We find that the model built by Swiss Model shows the best results in molecular modeling and validation and the structure is also stable throughout the 20 ns MD simulations. Consequently, this model is reliable and can be used for further studies.

A multichannel nucleic acid-based Ca2+ nanomodulator induces multilevel destruction of mitochondria for cancer therapy

Mitochondria play a crucial function in tumor proliferation and apoptosis, and inducing mitochondrial dysfunction in cells has emerged as a promising therapeutic approach for tumors. Here, curcumin (CUR) is enrolled in amorphous calcium phosphate (ACP) through the coprecipitation method, followed by Cy5.5-labeled DNA was adsorbed on its surface to propose an acidity-responsive nucleic acid-based nanomodulator (ACP@C-D) to enhance Ca2+ overload and mitochondrial biomineralization for cancer therapy by amplifying intra-mitochondrial Ca2+ concentration. After tumor cell administration, the ACP@C-D will disintegrate in the acidic environment to enhance Ca2+ overload by the combined interaction of a dramatic increase in Ca2+ concentration and Ca2+ efflux inhibition by Cur. Moreover, the mitochondrial targeting ability of Cy5.5 allows DNA enrichment at mitochondrial, and the phosphate on DNA provides reaction sites for Ca2+ to achieve mitochondrial biomineralization thus mitochondrial dysfunction, which is reported for the first time. The facile and functional strategy of the nanomodulator will provide new insights into inmitochondria-based cancer therapy.

Exploring common modulations induced by three fish RNA viruses in turbot (Scophthalmus maximus): Cholesterol, vitamin D3 and retinol metabolism as shared targets

Viral diseases pose a significant challenge in the fish aquaculture sector, as effective vaccines are lacking for many of them, and there are no approved antiviral treatments for use in aquaculture. Understanding how fish respond to diseases is fundamental for developing antiviral strategies, with a strong preference for broad-spectrum and economically accessible options. Therefore, identifying specific processes affected by multiple pathogens could help identify targets for wide-range therapeutic intervention. In this work, we conducted RNA-Seq to analyze the response to three RNA viruses (VHSV, IPNV, and RGNNV) at 3 days postinfection in flatfish turbot. For this purpose, head kidney samples from turbot infected with the different viruses and brain samples from the animals infected with RGNNV, as along with their corresponding uninfected controls, were sequenced. In head kidney samples, we found that the three RNA viruses shared the modulation of a set of genes that were predominantly involved in three metabolic pathways: cholesterol biosynthesis, vitamin D3 metabolism and retinol (vitamin A) metabolism. This observation, together with the systemic modulation of cholesterol and retinoic acid levels following viral infection, suggests that these metabolic processes could play a significant role in the antiviral immune response and/or the pathogenesis of these fish RNA viruses. Based on this, we used different metabolic modulators and metabolites to bring some light to the significance of these disturbances in the context of the viral infections. Statins (inhibitors of cholesterol synthesis) demonstrated in vitro antiviral activity, while valspodar (an inhibitor of cholesterol efflux) exhibited a proviral effect. Similarly, calcitriol (the active form of vitamin D3), retinol, and retinoic acid exhibited potent antiviral activity against the three RNA viruses. These findings underscore that metabolism represents a compelling target for broad-spectrum antiviral interventions, and future studies on immunometabolism will provide valuable insights for identifying specific therapeutic targets to fight fish viral diseases.

Assessment In vitro and In silico of the Activity of Thiadiazines as NorA Efflux Pump Inhibitors.

Antimicrobials fight microorganisms, preventing and treating infectious diseases. However, antimicrobial resistance (AMR) is a growing concern due to the inappropriate and excessive use of these drugs. Several mechanisms can lead to resistance, including efflux pumps such as the NorA pump in Staphylococcus aureus, which reduces the effectiveness of fluoroquinolones. Thiadiazines are heterocyclic compounds whose chemical structure resembles that of cephalosporins. Therefore, these compounds and their derivatives have been studied for their potential in combating increased bacterial resistance. To analyze this hypothesis, direct activity assays, antibiotic action-modifying activity, fluorescence assays to evaluate the retention of ethidium bromide inside bacteria, and molecular docking were carried out. These experiments involved serial dilutions in microplates against Staphylococcus aureus strain 1199B under the influence of six thiadiazine derivatives (IJ10, IJ11, IJ21, IJ22, IJ23, and IJ25). The tests revealed that, despite not showing effective direct activity, some thiadiazine derivatives (IJ11, IJ21, and IJ22) inhibited the function of the bromide pump both in microdilution tests and in fluorescence and docking assays. Particularly, the IJ11 compound stood out for its activity similar to efflux inhibitors, as well as its inhibition of the norfloxacin pump of this bacterium. Among the results of this study, it deserves to be highlighted for anchoring future experiments, as it represents the first investigation of this group of thiadiazine derivatives against the NorA pump.

Different Strategies to Overcome Resistance to Proteasome Inhibitors-A Summary 20 Years after Their Introduction.

Proteasome inhibitors (PIs), bortezomib, carfilzomib, and ixazomib, are the first-line treatment for multiple myeloma (MM). They inhibit cytosolic protein degradation in cells, which leads to the accumulation of misfolded and malfunctioned proteins in the cytosol and endoplasmic reticulum, resulting in cell death. Despite being a breakthrough in MM therapy, malignant cells develop resistance to PIs via different mechanisms. Understanding these mechanisms drives research toward new anticancer agents to overcome PI resistance. In this review, we summarize the mechanism of action of PIs and how MM cells adapt to these drugs to develop resistance. Finally, we explore these mechanisms to present strategies to interfere with PI resistance. The strategies include new inhibitors of the ubiquitin-proteasome system, drug efflux inhibitors, autophagy disruption, targeting stress response mechanisms, affecting survival and cell cycle regulators, bone marrow microenvironment modulation, and immunotherapy. We list potential pharmacological targets examined in in vitro, in vivo, and clinical studies. Some of these strategies have already provided clinicians with new anti-MM medications, such as panobinostat and selinexor. We hope that further exploration of the subject will broaden the range of therapeutic options and improve patient outcomes.

Anodic Cyclization Reactions and an Approach to the Chrysosporazine Family of Natural Products

Electrochemistry has long offered new opportunities for the construction of biologically relevant molecules. Many of these opportunities are based on the ability that electrochemistry provides for reversing the polarity of known functional groups. For example, consider the brief retrosynthetic analysis shown in the Scheme below. The analysis proposes a route to the Chrysosporazine family of natural products (specifically Chrysosporazine D in this case) from readily available amino acid and lignin derived starting materials. The Chrysosporazines are efflux inhibitors that improve the effectiveness of chemotherapy agents.1 The plan calls for a coupling of the two starting materials to afford a cyclization substrate. However, the proposed cyclization reaction would combine a nucleophilic amide nitrogen with a nucleophile electron rich styrene derivative. In principle, an anodic oxidation reaction can solve this issue by either converting the amide nitrogen into a radical or oxidizing the styrene derivative to form a radical cation. Either mode would effectively reverse the polarity of one of the nucleophilic groups and allow for the cyclization. Previous efforts examining these cyclizations have focused on the generation of a N-radical intermediate.2 Yet while these efforts have been very successful, they require the presence of a phenyl ring on the amide nitrogen in order to lower its pKa. This is essential for the formation of an amide anion that is in turn oxidized to the desired N-radical. Such a plan is not compatible with the synthesis of the Chrysosporazines that simply do not have a phenyl ring on the nitrogen of the amide. Placing one there would prevent the intramolecular cyclization. So, how can this problem be resolved? There are two possible answers to this question. One involves a change in the overall strategy that converts the amide into an electron-rich olefin equivalent that can be oxidized to from a radical cation. The second involves finding an alternative method for dropping the pKa of the amide so that the anion and subsequent N-radical can still be made. In the chemistry to be discussed, both strategies will be examined and the propensity for the cyclic product to undergo over-oxidation shown to be the determining factor for which pathway is preferred; a preference that has led to a new approach to N-based radical cyclizations. 1. Elbanna, A. H., Khalil, Z. G., Bernhardt, P., V., Capon, R. J. Org. Lett. 2019, 21, 8097–8100. 2. Xiong, P.; Xu, H-C. Acc. Chem. Res. 2019, 52, 3339-3350. Figure 1

7-Ketocholesterol promotes cholesterol uptake and inflammation in macrophage: Potential mechanisms of dietary COP in atherosclerosis promotion

This study investigated the effects and mechanisms of 7-ketocholesterol in promoting macrophage foaming and inflammation. Single-cell RNA sequencing showed that dietary cholesterol oxidation products increased the inflammatory macrophage and Trem2high macrophage numbers in the atherosclerotic aorta of ApoE−/− mice. Enrichment analysis demonstrated activation of inflammation-related pathways (NF-κB pathway and NLRP3 inflammasome) in inflammatory macrophages and cholesterol metabolism-related pathways (LDLR and ABCG1) in Trem2high macrophages. An oxidized-LDL-treated macrophage model was employed to verify the effects and mechanisms of 7-KC on macrophage inflammation and foam cell formation. 7-KC promoted the inflammation and M1 polarization of macrophage in association with the activations of the NF-κB pathway and NLRP3 inflammasome. Furthermore, 7-KC-mediated excessive cholesterol accumulation was attributed to enhanced cholesterol uptake rather than inhibition of cholesterol efflux. Consequently, LDLR expression was up-regulated by 7-KC, while no significant effect on ABCG1 expression was observed.

Discovery of pyridoquinoxaline-based new P-gp inhibitors as coadjutant against Multi Drug Resistance in cancer

Multi-drug resistance (MDR) is a serious challenge in contemporary clinical practice and is mostly responsible for the failure of cancer medication therapies. Several experimental evidence links MDR to the overexpression of the drug efflux transporter P-gp, therefore, the discovery of novel P-glycoprotein inhibitors is required to treat or prevent MDR and to improve the absorption of chemotherapy drugs via the gastrointestinal system. In this work, we explored a series of novel pyridoquinoxaline-based derivatives designed from parental compounds, previously proved active in enhancing anticancer drugs in MDR nasopharyngeal carcinoma (KB). Among them, derivative 10d showed the most potent and selective inhibition of fluorescent dye efflux, if compared to reference compounds (MK-571, Novobiocin, Verapamil), and the highest MDR reversal activity when co-administered with the chemotherapeutic agents Vincristine and Etoposide, at non-cytotoxic concentrations. Molecular modelling predicted the two compound 10d binding mode in a ratio of 2:1 with the target protein. No cytotoxicity was observed in healthy microglia cells and off-target investigations showed the absence of CaV1.2 channel blockade. In summary, our findings indicated that 10d could potentially be a novel therapeutic coadjutant by inhibiting P-gp transport function in vitro, thereby reversing cancer multidrug resistance.

Repurposing of dibucaine and niflumic acid as antimicrobial agents in combination with antibiotics against Staphylococcus aureus.

The versatile human commensal bacteria and pathogen Staphylococcus aureus cause several community and hospital-acquired illnesses associated with significant morbidity and death. Antibiotic therapy for S. aureus infections has grown increasingly difficult as the organism has developed a wide spectrum of antibiotic resistance mechanisms. This situation emphasizes the significance of developing and advocating new antimicrobials for preventative and therapeutic measures. Our study aimed to identify and evaluate new therapeutic options against S. aureus. We investigated the efficacy of two drugs, dibucaine, and niflumic acid, as potential adjuvant for anti-staphylococcal therapeutics. Dibucaine and niflumic acid found to have bactericidal activity against S. aureus. These drugs acted synergistically with antibiotics reducing the required dose of antibiotics up to 4 times. In combination with antibiotics, they were effectively and synergistically inhibited the formation of biofilms of S. aureus. The best synergistic partner of dibucaine was with kanamycin and tetracycline, whereas niflumic acid was with streptomycin and ampicillin. Both the drugs showed significant efflux inhibition in the bacteria. Moreover, the drugs are found to be safe at synergistic doses. Our findings suggest that dibucaine and niflumic acid could be potential adjuvant with antibiotics for the treatment of S. aureus infections. Their ability to significantly enhance the efficacy of antibiotics highlights their potential clinical significance as adjunct therapies.

Ginsenoside Rh2 Regulates the Calcium/ROS/CK1α/MLKL Pathway to Promote Premature Eryptosis and Hemolysis in Red Blood Cells.

Ginsenoside Rh2 (GRh2) exhibits significant potential as an anticancer agent; however, progress in developing chemotherapeutic drugs is impeded by their toxicity toward off-target tissues. Specifically, anemia caused by chemotherapy is a debilitating side effect and can be caused by red blood cell (RBC) hemolysis and eryptosis. Cells were exposed to GRh2 in the antitumor range and hemolytic and eryptotic markers were examined under different experimental conditions using photometric and cytofluorimetric methods. GRh2 caused Ca2+-independent, concentration-responsive hemolysis in addition to disrupted ion trafficking with K+ and Cl- leakage. Significant increases in cells positive for annexin-V-fluorescein isothiocyanate, Fluo4, and 2,7-dichlorofluorescein were noted upon GRh2 treatment coupled with a decrease in forward scatter and acetylcholinesterase activity. Importantly, the cytotoxic effects of GRh2 were mitigated by ascorbic acid and by blocking casein kinase 1α (CK1α) and mixed lineage kinase domain-like (MLKL) signaling. In contrast, Ca2+ omission, inhibition of KCl efflux, and isosmotic sucrose aggravated GRh2-induced RBC death. In whole blood, GRh2 selectively targeted reticulocytes and lymphocytes. Altogether, this study identified novel mechanisms underlying GRh2-induced RBC death involving Ca2+ buildup, loss of membrane phospholipid asymmetry and cellular volume, anticholinesterase activity, and oxidative stress. These findings shed light on the hematologic toxicity of GRh2 which is crucial for optimizing its utilization in cancer treatment.

Pharmacokinetic Modeling of the Effect of Tariquidar on Ondansetron Disposition into the Central Nervous System

PurposeSerotonin (5-HT3) receptor antagonists are promising agents for treatment of neuropathic pain. However, insufficient drug exposure at the central nervous system (CNS) might result in lack of efficacy. The goal of this study was to evaluate the impact of administration of a Pgp inhibitor (tariquidar) on ondansetron exposure in the brain, spinal cord, and cerebrospinal fluid in a wild-type rat model.MethodsOndansetron (10 mg/kg) and tariquidar (7.5 mg/kg) were administered intravenously, plasma and tissue samples were collected and analyzed by HPLC. A mathematical model with brain, spinal cord, cerebrospinal fluid and two systemic disposition compartments was developed to describe the data.ResultsThe results demonstrate that tariquidar at 7.5 mg/kg resulted in a complete inhibition of Pgp efflux of ondansetron in the brain and spinal cord. The compartmental model successfully captured pharmacokinetics of ondansetron in wild type and Pgp knockout (KO) animals receiving the drug alone or in wild type animals receiving the ondansetron and tariquidar combination.ConclusionsThe study provided important quantitative information on enhancement of CNS exposure to ondansetron using co-administration of Pgp Inhibitor in a rat model, which will be further utilized in conducting a clinical study. Tariquidar co-administration resulted in ondansetron CNS exposure comparable to observed in Pgp KO rats. Results also highlighted the effect of tariquidar on plasma disposition of ondansetron, which may not be dependent on Pgp inhibition, and should be evaluated in future studies.

Effect of phenylalanine arginyl β-naphthylamide on the imipenem resistance, elastase production, and the expression of quorum sensing and virulence factor genes in Pseudomonas aeruginosa clinical isolates.

Pseudomonas aeruginosa is one of the most important nosocomial pathogens that possess the ability to produce multiple antibiotic resistance and virulence factors. Elastase B (LasB) is the major factor implicated in tissue invasion and damage during P. aeruginosa infections, whose synthesis is regulated by the quorum sensing (QS) system. Anti-virulence approach is now considered as potential therapeutic alternative and/or adjuvant to current antibiotics' failure. The aim of this study is primarily to find out the impact of the efflux pump inhibitor (EPI) phenylalanine arginyl β-naphthylamide (PAβN) on the production of elastase B and the gene expression of lasI quorum sensing and lasB virulence factor in clinical isolates of P. aeruginosa. Five P. aeruginosa isolates recovered from patients with respiratory tract infections were examined in this study. Antimicrobial susceptibility of isolates was performed by the disk agar diffusion method. Effect of the PAβN on imipenem susceptibility, bacterial viability, and elastase production was evaluated. The expression of lasB and lasI genes was measured by quantitative real-time PCR in the presence of PAβN. All isolates were identified as multidrug-resistant (MDR) and showed resistance to carbapenem (MIC = 64-256µg/mL). Susceptibility of isolates to imipenem was highly increased in the presence of efflux inhibitor. PAβN significantly reduced elastase activity in three isolates tested without affecting bacterial growth. In addition, the relative expression of both lasB and lasI genes was diminished in all isolates in the presence of inhibitor. Efflux inhibition by using the EPI PAβN could be a potential target for controlling the P. aeruginosa virulence and pathogenesis. Furthermore, impairment of drug efflux by PAβN indicates its capability to be used as antimicrobial adjuvant that can decrease the resistance and lower the effective doses of current drugs.

Resistance to aztreonam-avibactam among clinical isolates of Escherichia coli is primarily mediated by altered penicillin-binding protein 3 and impermeability

This study was conducted to investigate decreased susceptibility (minimum inhibitory concentrations [MICs] 0.25–4 mg/L) and resistance (MICs > 4 mg/L) to aztreonam-avibactam (ATM-AVI). Contemporary non-replicate clinical isolates of carbapenemase-producing Escherichia coli (CP-EC) (n=90) and ESBL-producing E. coli (EP-EC) (n=12) were used. CP-EC belonged to 25 distinct sequence types (STs) and all EP-EC belonged to ST405. All strains were isolated from 2019 to 2022 at the Karolinska University Laboratory, Stockholm, Sweden. ATM-AVI MICs were determined using broth microdilution. The EUCAST epidemiological cut-off value of 0.125 mg/L was used to define the wild type (WT). Whole-genome sequences (Illumina) were analysed for detecting resistance determinants among WT vs. non-WT isolates. Among 102 isolates, 40 (39%) and 62 (61%) were WT and non-WT, respectively. Among non-WT isolates, resistance was noted for 20 and decreased susceptibility for 42. Resistance was observed among 14/47 New Delhi metallo-β-lactamase (NDM)-producers, 5/43 OXA-48 group producers, and 1/12 EP-EC. Decreased susceptibility was observed among 29/47 NDM, 13/43 OXA-48 group, and 3/12 EP-EC. Resistant isolates predominantly belonged to ST405, followed by STs 410, 361, 167, 617, and 1284. Penicillin-binding protein 3 (PBP3) inserts (YRIK/YRIN) were observed in 20/20 and CMY-42 in 5/20 resistant isolates. Several mutations in the ftsI (encoding PBP3) and regulatory genes of outer membrane proteins (OmpC and OmpF) and efflux pumps (AcrAB-TolC) were detected. A ≥ 2-fold reduction in MICs was observed among 20/20 vs. 7/20 isolates tested in the presence of the membrane permeabiliser, polymyxin B nanopeptide (PMBN) and efflux inhibitor, phenylalanine arginine β-naphthylamide (PAβN), respectively. In conclusion, resistance to ATM-AVI is a result of interplay of various determinants, including target alterations, deactivating enzymes, and decreased permeability.