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Serine/metallo-carbapenemase-coproducing pathogens, often referred to as "superbugs", are a significant clinical problem. They hydrolyze nearly all available β-lactam antibiotics, especially carbapenems considered as last-resort antibiotics, seriously endangering efficacious antibacterial treatment. Despite the continuous global spread of carbapenem resistance, no dual-action inhibitors are available in therapy. This Perspective is the first systematic investigation of all chemotypes, modes of inhibition, and crystal structures of dual serine/metallo-carbapenemase inhibitors. An overview of the key strategy for designing dual serine/metallo-carbapenemase inhibitors and their mechanism of action is provided, as guiding rules for the development of clinically available dual inhibitors, coadministrated with carbapenems, to overcome the carbapenem resistance issue.

Background: : The appearance of antibiotic resistance caused by metallo-β-lactamases (MβLs) is a global public health threat. Developing MβLs inhibitor is an effective way to overcome antibiotic resistance. Recently, azolylthioacetamides were reported to be promising MβLs inhibitors. Methods:: Triazolylthioacetamides were synthesized and tested for inhibition activity against the purified MβL IMP-1. Antimicrobial activities of these inhibitors in combination with cefazolin were evaluated. Isothermal Titration Calorimetry (ITC) was employed to characterize the binding of the inhibitor to IMP-1, and their action mechanism was studied by molecular docking. Results: Twenty compounds exhibited specific inhibitory activity against IMP-1 with an IC50 value in the range of 3.1-62.5 μM. Eight of the compounds can restore the antibacterial efficacy of cefazolin against E. coli BL21 strain producing IMP-1 by 2-4 fold. ITC monitoring showed that 1c exhibited dose-dependent inhibition on IMP-1. Docking studies revealed that the triazole group in 1c and 2d played an essential role in the inhibition activity. Cytotoxicity assay showed that 1c and 2d have low toxicity in L929 mouse fibroblastic cells. Conclusion: : The triazolylthioacetamides are efficient inhibitors of IMP-1 in vitro and in vivo.

The overuse of antibiotics exacerbates the development of antibiotic-resistant bacteria, threatening global public health, while most traditional antibiotics act on specific targets and sterilize through chemical modes. Therefore, it is a desperate need to design novel therapeutics or extraordinary strategies to overcome resistant bacteria. Herein, we report a positively charged nanocomposite PNs-Cur with a hydrodynamic diameter of 289.6 nm, which was fabricated by ring-opening polymerization of ε-caprolactone and Z-Lys

The drug resistance caused due to the overuse of antibiotics has grown into an emerging threat. It is urgent to develop novel strategies to combat bacterial resistance. In this work, a quinine-based quaternized polymer with amphiphilicity (QMTA) was prepared by free-radical copolymerization of quinine and (2-methacryloyloxyethyl) trimethyl ammonium chloride (MTA). Biological activity assays revealed that the polymer sterilized the drug-resistant Gram-negative E. coli and non-resistant Gram-positive bacteria B. subtilis, exhibiting a MIC value of 2 μg mL−1 and a bactericidal rate of more than 95%. Most importantly, both E. coli and B. subtilis treated with the polymer didn't develop resistance even after their 16th passages. Also, the polymer has low toxicity at a dose of up to 128 μg mL−1. The mechanism studies through SEM and 3D-SIM images, fluorescence staining and membrane potential determination reveal that the positively charged QMTA initially concentrates on the surface of bacteria by electrostatic adsorption, changes the membrane potential, binds to the bacteria by its quinine chain, and destroys the membrane structure of the bacteria. This study provides a potential approach through the existing drug to develop new bactericidal reagent/polymer materials without resistance.

It is imperative to develop innovative and efficient antibacterial agents, on account of the mounting prevalence of complicated infections induced by multidrug-resistant bacteria. In this work, Chol-b-Lys nanoparticles (CL-NPs) with a diameter of 304.9 nm were prepared by ring-opening polymerization of the monomers cholesterol-ethylenediamine conjugate (Chol-NH2) and L-Lys-N-carboxyanhydrides (L-Lys-NCAs) and further self-assembly. The nanoparticles exhibited biological activity against the drug-resistant and non-resistant bacteria, including Gram-negative E. coli and Gram-positive B. subtilis, E. faecalis and S. aureus, with a MIC value in the range of 32–2 μg mL−1 and a more than 95% bactericidal rate. Importantly, both bacteria treated with CL-NPs didn’t develop resistance even after their 16th passages. Also, the CL-NPs have low toxicity (32 μg mL−1). The mechanism characterization shows that the positively charged nanoparticles are initially gathered on the surface of bacteria by electrostatic adsorption, changes the membrane permeability, inserts into the lipid bilayer bacteria membrane with cholesterol groups, destroys the membrane structure and results in bacterial apoptosis. This work provides a potential approach by mimicking the structure of cell membrane to develop new bactericidal reagent/nanoparticle materials which is hard to cause resistance.

The emergence and prevalence of carbapenem-resistant bacterial infection have seriously threatened the clinical use of almost all β-lactam antibacterials. The development of effective metallo-β-lactamase (MβL) inhibitors to restore the existing antibiotics efficacy is an ideal alternative. Although several types of serine-β-lactamase inhibitors have been successfully developed and used in clinical settings, MβL inhibitors are not clinically available to date. Herein, we identified that cisplatin and Pd(II) complexes are potent broad-spectrum inhibitors of the B1 and B2 subclasses of MβLs and effectively revived Meropenem efficacy against MβL-expressing bacteria in vitro. Enzyme kinetics, thermodynamics, inductively coupled plasma atomic emission spectrometry (ICP-AES), matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS), and site-directed mutation assays revealed that these metal complexes irreversibly inhibited NDM-1 through a novel inhibition mode involving binding to Cys208 and displacing one Zn(II) ion of the enzyme with one Pt(II) containing two NH3's or one Pd(II) ion. Importantly, the combination therapy of Meropenem and metal complexes significantly suppressed the development of higher-level resistance in bacteria producing NDM-1, also effectively reduced the bacterial burden in liver and spleen of mice infected by carbapenem-resistant Enterobacteriaceae producing NDM-1. These findings will offer potential lead compounds for the further development of clinically useful inhibitors targeting MβLs.

The emerging COVID-19 pandemic generated by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has severely threatened human health. The main protease (M

Bacterial resistance caused by metallo-β-lactamases (MβLs) has become an emerging public health threat, and the development of MβLs inhibitor is an effective way to overcome the resistance. In this study, thirteen novel O-aryloxycarbonyl hydroxamates were constructed and assayed against MβLs. The obtained molecules specifically inhibited imipenemase-1 (IMP-1) and New Delhi metallo-β-lactamase-1 (NDM-1), exhibiting an IC50 value in the range of 0.10-18.42 and 0.23-22.33 μM, respectively. The hydroxamate 5 was found to be the most potent inhibitor, with an IC50 of 0.1 and 0.23 μM using meropenem and cefazolin as substrates. ICP-MS analysis showed that 5 did not coordinate to the Zn(II) ions at the active-site of IMP-1, while the rapid dilution, thermal shift and MALDI-TOF assays revealed that the hydroxamate formed a covalent bond with the enzyme. Cytotoxicity assays indicated that the hydroxamates have low toxicity in MCF-7 cells. This work provided a potent scaffold for the development of MβLs inhibitors.

Metallo-β-lactamases (MβLs) hydrolyze almost all β-lactam antibiotics, including last-resort carbapenems, and is emerging as a global antibiotic resistance threat. Discovering novel fluorescent molecules for visualizing MβLs has proved challenging. Herein, based on covalent and Zn(II)-binding scaffold of MβLs inhibitor, we designed and synthesized a novel series of environment-sensitive fluorescent probes ESA, DHA and DHS, to detect and inhibit the enzymatic activity of MβLs. Of these probes, ESA is a highly active NDM-1 inhibitor (IC

Antibiotic resistance mediated by β-lactamases including metallo-β-lactamases (MβLs) has become an emerging threat. In this study, we employed UV-vis to monitor the activity and inhibition of New Delhi MβL (NDM), K. pneumoniae carbapenemase (KPC) and MβL VIM-2 in live bacterial cells in real time. The monitoring showed that the faropenem was hydrolyzed by six strains which express β-lactamases, K. pneumoniae, P. aeruginosa, E. coli expressing extended-spectrum β-lactamase (ESBL), NDM-1 (EC07), VIM-2, and methicillin-resistant S. aureus (MRSA), but not by E. coli and S. aureus which do not express β-lactamases. Also, four β-lactams cefazolin, meropenem, faropenem and amoxicillin were hydrolyzed by the NDM and KPC expressed in K. pneumoniae. Cell-based studies revealed that the targets NDM and KPC expressed in K. pneumoniae cells were inhibited by three known inhibitors ethylene diamine tetraacetic acid (EDTA), ebselen and clavulanic acid, with a fifty percent inhibitory concentration (IC50) of 1.2, 84.7 and 13.3 μM, and the VIM-2 expressed in E. coli cells was inhibited by EDTA, D-captopril and rhodanine with an IC50 of 1.3, 510.8 and 9.3 μM, respectively. This study provides an approach that could be applied to screen and evaluate small molecule inhibitors of β-lactamases in whole cells or to identify drug resistant bacteria.

The overuse of traditional antibiotics has resulted in a large number of bacteria that are resistant to antibiotics; therefore, the development of new antibacterial agents is urgently required to combat the drug-resistant bacteria. In this work, a series of cationic polyacrylate copolymers N1–N4 was synthesized by free-radical copolymerization. Amphiphilic N3 self-assembled into positively charged nanostructures (N3-NSs) with a diameter of 455.9 nm and a zeta potential of 33.4 mV in aqueous solution, which was confirmed by SEM and DLS. N3-NSs exhibited a broad-spectrum and high sterilization efficacy against both Gram-positive and Gram-negative bacteria, with a MIC value in the range of 2–8 μg mL−1 and a more than 94% sterilization rate against the drug-resistant E. coli, P. aeruginosa, E. faecalis, VRE, and B. subtilis tested. Most importantly, the nanostructures did not result in resistance of the VRE and P. aeruginosa even after their 16th passages. N3-NSs caused serious damage to E. coli and E. faecalis membranes, with significant loss of membrane potential from −43.9 ± 0.6 and −39.1 ± 1.4 to −6.3 ± 0.3 and −4.6 ± 0.2 mV, respectively. Fluorescence staining, SEM and membrane potential characterization reveal the action mechanism of the nanostructures, which is that N3-NSs initially bind to the surface of bacteria, then pierce into the bacterial membranes with their hydrophobic groups, and finally disrupt the membranes, therefore exhibiting broad-spectrum antibacterial efficacy. N3-NSs exhibit low toxicity on mouse fibroblasts (L929) at a dose of 40 μg mL−1. This work provides a promising way for the development of efficient antibacterial materials that do not cause drug-resistance.

We report a promising NDM-1 inhibitor, disulfiram, which can covalently bind to NDM-1 by forming an S–S bond with the Cys208 residue. Its copper-containing metabolite in vivo, Cu(DTC)2, also inactivated NDM-1 through oxidizing the Zn(II) thiolate site of the enzyme, therefore exhibiting dual functional inhibitory potential against B1 and B2 subclass MβLs.

The traditional antibiotics have specific intracellular targets and disinfect in chemical ways, and the drug-resistance induced by the antibiotics has grown into an emerging threat. It is urgent to...

The d , d -dipeptidase enzyme VanX is the main cause of vancomycin resistance in gram-positive bacteria because of hydrolysis of the D-Ala-D-Ala dipeptide used in cell-wall biosynthesis. Continuous assay of VanX has proven challenging due to lack of a chromophoric substrate. Here, we report a direct approach for continuous assay of VanX in vitro and in vivo from hydrolysis of D-Ala-D-Ala, based on the heat-rate changes measured with isothermal titration calorimetry (ITC). With the ITC approach, determination of kinetic parameters of VanX hydrolyzing D-Ala-D-Ala and the inhibition constant of d -cysteine inhibitor yielded KM of 0.10 mM, kcat of 11.5 s−1, and Ki of 18.8 μM, which are consistent with the data from ninhydrin/Cd(II) assays. Cell-based ITC studies demonstrated that the VanX expressed in E. coli and in clinical strain VRE was inhibited by d -cysteine with IC50 values of 29.8 and 28.6 μM, respectively. Also, the total heat from D-Ala-D-Ala (4 mM) hydrolysis decreases strongly (in absolute value) from 1.26 mJ for VRE to 0.031 mJ for E. faecalis, which is consistent with the large MIC value of vancomycin of 512 μg/mL for VRE and the much smaller value of 4 μg/mL for E. faecalis. The ITC approach proposed here could be applied to screen and evaluate small molecule inhibitors of VanX or to identify drug resistant bacteria.

A series of multivalent zwitterionic poly(methacrylate) copolymers (PMGT) containing different reactive ligands (epoxy and –Si–OCH3) are designed and synthesized for surface modification of 3-aminopropyltriethoxysilane activated PDMS (PDMS-A) via a simple incubation and subsequent post-crosslinking procedure. The co-existence of protonated primary amine (NH3+), terminal primary amine (−NH2) and Si–OH/Si–OC2H5 surface receptors on PDMS-A created a platform to fabricate stable PMGT coatings through multivalent interactions with epoxy and –Si–OCH3 ligands in the polymer chains. The effect of molar ratio of epoxy and –Si–(OCH3)3 ligands (ne/nSi) in the polymer chains on the cooperativity of multivalent interactions is studied. The results show that ne/nSi in the PMGT polymer chain plays a crucial role in the regulation of the coating formation. At higher ne/nSi (1.78), a relatively rough and thin biomimetic coating is formed. By contrast, lower ne/nSi (1.04) in the polymer chain is helpful to produce a more uniform and dense polymer coating. It is attributed to the good balance between the anchoring of polymer chains and the growth of coating thickness in the incubation step through suppressing the competitive autocatalytic crosslinking reactions of epoxy-amine system, demonstrating positive cooperativity of multivalent interactions. The following post-crosslinking procedure under moisture atmosphere containing triethylamine (TEA) facilitates to realize the formation of durable PMGT polymer coating, in which zwitterionic PC moieties are orientated towards the outer surface, providing the PDMS with greatly improved controllable hydrophilicity, coating stability and antifouling properties.

The superbug infection caused by New Delhi metallo-β-lactamase (NDM-1) has grown into an emerging threat, labelling and inhibition of NDM-1 has proven challenging due to its shuttling between pathogenic bacteria. Here, we report a potent covalent scaffold, ebsulfur, for targeting the protein in vitro and in vivo. Enzymatic kinetic study indicated that eighteen ebsulfurs gained except 1a–b and 1f inhibited NDM-1, exhibiting an IC50 value ranging of 0.16–9 μM, and 1g was found to be the best, dose- and time-dependent inhibitor with an IC50 of 0.16 μM. Also, these ebsulfurs effectively restored the antibacterial activity of cefazolin against E. coli expressing NDM-1, and the best effect was observed to be from 1g, 1i and 1n, resulting in an 256-fold reduction in MIC of the antibiotic at a dose of 16 μg/mL. The equilibrium dialysis study implied that the ebsulfur disrupted the coordination of one Zn(II) ion at active site of NDM-1. Labelling of NDM-1 using a constructed fluorescent ebsulfur Ebs-R suggested that the inhibitor covalently bound to the target through SDS-PAGE analysis in vitro. Also, labelling NDM-1 in living E. coli cells with Ebs-R by confocal microscopic imaging showed the real-time distribution change process of intracellular recombinant protein NDM-1. Moreover, the cytotoxicity of these ebsulfurs against L929 mouse fibroblastic cells was tested, and their capability to restore antibacterial activity of antibiotic against clinical strains E. coli EC08 producing NDM-1 was determined. The ebsulfur scaffold proposed here is valuable for development of the covalent irreversible inhibitors of NDM-1, and also for labelling the target in vitro and in vivo.

The superbug infection mediated by metallo-β-lactamases (MβLs) has grown into anemergent health threat, and development of MβL inhibitors is an ideal strategy to combat the infection. In this work, twenty-five thiosemicarbazones 1a-e, 2a-e, 3a-e, 4a-d, 5a-d and 6a-b were synthesized and assayed against MβLs ImiS, NDM-1 and L1. The gained molecules specifically inhibited NDM-1 and ImiS, exhibiting an IC

The irregular use of antibiotics has created a natural selection pressure for bacteria to adapt resistance. Bacterial resistance caused by metallo-β-lactamases (MβLs) has been the most prevalent in terms of posing a threat to human health. The New Delhi metallo-β-lactamase-1 (NDM-1) has been shown to be capable of hydrolyzing almost all β-lactams. In this work, eight aromatic Schiff bases 1-8 were prepared and identified by enzyme kinetic assays to be the potent inhibitors of NDM-1 (except 4). These molecules exhibited a more than 95 % inhibition, and an IC

The expression of β-lactamases, especially metallo-β-lactamases (MβLs) in bacteria is one of the main causes of drug resistance. In this work, an effective N-acylhydrazone scaffold as MβL inhibitor was constructed and characterized. The biological activity assays indicated that the synthesized N-acylhydrazones 1–11 preferentially inhibited MβL NDM-1, and 1 was found to be the most effective inhibitor with an IC50 of 1.2 µM. Analysis of IC50 data revealed a structure–activity relationship, which is that the pyridine and hydroxylbenzene substituents at 2-position improved inhibition of the compounds on NDM-1. ITC and enzyme kinetics assays suggested that it reversibly and competitively inhibited NDM-1 (Ki = 0.29 ± 0.05 µM). The synthesized N-acylhydrazones showed synergistic antibacterial activities with meropenem, reduced 4–16-fold MIC of meropenem on NDM-1- producing E. coli BL21 (DE3), while 1 restored 4-fold activity of meropenem on K. pneumonia expressing NDM-1 (NDM-K. pneumoniae). The mice experiments suggested that 1 combined meropenem to fight against NDM-K. pneumoniae infection in the spleen and liver. Cytotoxicity assays showed that 1 and 2 have low cytotoxicity. This study offered a new framework for the development of NDM-1 inhibitors.

To combat the superbug infection caused by metallo-β-lactamases (MβLs), a dipyridyl-substituted thiosemicarbazone (DpC), was identified to be the broad-spectrum inhibitor of MβLs (NDM-1, VIM-2, IMP-1, ImiS, L1), with an IC50 value in the range of 0.021–1.08 µM. It reversibly and competitively inhibited NDM-1 with a Ki value of 10.2 nM. DpC showed broad-spectrum antibacterial effect on clinical isolate K. pneumonia, CRE, VRE, CRPA and MRSA, with MIC value ranged from 16 to 32 µg/mL, and exhibited synergistic antibacterial effect with meropenem on MβLs-producing bacteria, resulting in a 2–16-, 2–8-, and 8-fold reduction in MIC of meropenem against EC-MβLs, EC01-EC24, K. pneumonia, respectively. Moreover, mice experiments showed that DpC also had synergistic antibacterial action with meropenem. In this work, DpC was identified to be a potent scaffold for the development of broad-spectrum inhibitors of MβLs.

The emerging COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has raised a global catastrophe. To date, there is no specific antiviral drug available to combat this virus, except the vaccine. In this study, the main protease (Mpro) required for SARS-CoV-2 viral replication was expressed and purified. Thirty-six compounds were tested as inhibitors of SARS-CoV-2 Mpro by fluorescence resonance energy transfer (FRET) technique. The half-maximal inhibitory concentration (IC50) values of Ebselen and Ebsulfur analogs were obtained to be in the range of 0.074–0.91 μM. Notably, the molecules containing furane substituent displayed higher inhibition against Mpro, followed by Ebselen 1i (IC50 = 0.074 μM) and Ebsulfur 2k (IC50 = 0.11 μM). The action mechanism of 1i and 2k were characterized by enzyme kinetics, pre-incubation and jump dilution assays, as well as fluorescent labeling experiments, which suggested that both compounds covalently and irreversibly bind to Mpro, while molecular docking suggested that 2k formed an S S bond with the Cys145 at the enzymatic active site. This study provides two very potent scaffolds Ebsulfur and Ebselen for the development of covalent inhibitors of Mpro to combat COVID-19.

Background: Infections caused by metallo-β-lactamases (MβLs)-producing antibiotic-resistant bacteria pose a severe threat to public health. The synergistic use of current antibiotics in combination with MβL inhibitors is a promising therapeutic mode against these antibiotic-resistant bacteria. Objectives: The study aimed to probe the inhibition of MβLs and obtain the active component, P1, in the degradation product after imipenem was hydrolyzed by ImiS. Methods: The hydrolysis of two carbapenems with MβL ImiS was monitored by UV-Vis in real-time, and the degradation product from the leaving group produced after imipenem was hydrolyzed (but not for faropenem) was purified by HPLC to give one component, P1. Results: Kinetic assays revealed that P1 exhibited a broad-spectrum inhibition against VIM-2, NDM-1, ImiS, and L1, from three sub-classes of MβLs, with IC50 values of 8 - 32, 13.8 - 29.3, and 14.2 - 19.2 µM, using imipenem, cefazolin, and nitrocefin as substrates, respectively. Also, P1 showed synergistic antibacterial efficacy against drug-resistant Escherichia coli producing VIM-2, NDM-1, ImiS, and L1, in combination with antibiotics, restoring 16 to 32-fold and 32 to 128-fold efficacies of imipenem and cefazolin, respectively. Spectroscopic and Ellman's reagent analyses suggested that P1, a mercaptoethyl-form imidamide, is a mechanism-based inhibitor, while faropenem has no substrate inhibition, due to the lack of a leaving group. Conclusions: This work reveals that the hydrolysate of imipenem, a carbapenem with a good leaving group, can be used in screening for broad-spectrum inhibitors of MβLs.

The superbug infection caused by metallo-β-lactamases (MβLs) carrying drug-resistant bacteria, specifically, New Delhi metallo-β-lactamase (NDM-1) has become an emerging threat. In an effort to develop novel inhibitors of NDM-1, thirteen thiosemicarbazones (1a-1m) were synthesized and assayed. The obtained molecules specifically inhibited NDM-1, with an IC50 in the range of 0.88–20.2 µM, and 1a and 1f were found to be the potent inhibitors (IC50 = 1.79 and 0.88 μM) using cefazolin as substrate. ITC and kinetic assays indicated that 1a irreversibly and non-competitively inhibited NDM-1 in vitro. Importantly, MIC assays revealed that these molecules by themselves can sterilize NDM-producing clinical isolates EC01 and EC08, exhibited 78-312-fold stronger activities than the cefazolin. MIC assays suggest that 1a (16 μg ml−1) has synergistic antimicrobial effect with ampicillin, cefazolin and meropenem on E. coli producing NDM-1, resulting in MICs of 4-32-, 4-32-, and 4-8-fold decrease, respectively. These studies indicate that the thiosemicarbazide is a valuable scaffold for the development of inhibitors of NDM-1 and NDM-1 carrying drug-resistant bacteria.

The emergence and prevalence of carbapenem-resistant bacterial infection have seriously threatened the clinical use of almost all β-lactam antibacterials. The development of effective metallo-β-lactamase (MβL) inhibitors to restore the existing antibiotics efficacy is an ideal alternative. Although several types of serine-β-lactamase inhibitors have been successfully developed and used in clinical settings, MβL inhibitors are not clinically available to date. Herein, we identified that cisplatin and Pd(II) complexes are potent broad-spectrum inhibitors of the B1 and B2 subclasses of MβLs and effectively revived Meropenem efficacy against MβL-expressing bacteria

The "superbug" infection caused by metallo-β-lactamases (MβLs) has grown into anemergent health threat, and development of effective MβL inhibitors to restore existing antibiotic efficacy is an ideal alternative. Although the serine-β-lactamase inhibitors have been used in clinical settings, MβL inhibitors are not available to date. In this work, thirty-one quinolinyl sulfonamides 1a-p and sulphonyl esters 2a-o were synthesized and assayed against MβL NDM-1. The obtained molecules specifically inhibited NDM-1, 1a-p and 2a-o exhibited an IC

A biomimetic total synthesis of scabellone B is described. Through sequential regioselective introduction of a geranyl group by means of silyl protection, oxidative dimerization, and biomimetic oxo-6π electrocyclization with good cyclization selectivity, a biomimetic ­approach to scabellone B was achieved in five steps and 32% overall yield.

The worldwide prevalence of NDM-1-producing Gram-negative pathogens has drastically undermined the clinical efficacy of carbapenems, prompting a need to devise an effective strategy to preserve their clinical value. Here we constructed a focused compound library of dithiocarbamates and systematically evaluated their potential synergistic antibacterial activities combined with copper. SA09-Cu exhibited excellent inhibition against a series of clinical NDM-1-producing carbapenem-resistant Enterobacteriaceae (CRE) in restoring meropenem effect, and slowed down the development of carbapenem resistance. Enzymatic kinetic and isothermal titration calorimetry studies demonstrated that SA09-Cu was a noncompetitive NDM-1 inhibitor. The electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) revealed a novel inhibition mechanism, which is that SA09-Cu could convert NDM-1 into an inactive state by oxidizing the Zn(II)-thiolate site of the enzyme. Importantly, SA09-Cu showed a unique redox tuning ability, and avoided to be reduced by intracellular thiols of bacteria. In vivo experiments indicated that SA09 combined with CuGlu could effectively potentiate MER's effect against NDM-1-producing E. coli (EC23) in the murine infection model. This study provides a highly promising scaffold in developing novel inhibitors to combat NDM-1-producing CREs.

In an effort to develop new inhibitors of metallo-β-lactamases (MβLs), twenty-eight azolylthioacetamides were synthesized and assayed against MβLs. The obtained benzimidazolyl and benzioxazolyl substituted 1-19 specifically inhibited the enzyme ImiS, and 10 was found to be the most potent inhibitor of ImiS with an IC50 value of 15 nM. The nitrobenzimidazolyl substituted 20-28 specifically inhibited NDM-1, with 27 being the most potent inhibitor with an IC50 value of 170 nM. Further studies with 10, 11, and 27 revealed a mixed inhibition mode with competitive and uncompetitive inhibition constants in a similar range as the IC50 values. These inhibitors resulted in a 2-4-fold decrease in imipenem MIC values using E. coli cells producing ImiS or NDM-1. While the source of uncompetitive (possibly allosteric) inhibition remains unclear, docking studies indicate that 10 and 11 may interact orthosterically with Zn2 in the active site of CphA, while 27 could bridge the two Zn(II) ions in the active site of NDM-1 via its nitro group.

Metallo-β-lactamase (MβL) ImiS contributes to the emergence of carbapenem resistance. A potent scaffold, meta-substituted benzenesulfonamide, was constructed and assayed against MβLs. The twenty-one obtained molecules specifically inhibited ImiS (IC(50) = 0.11–9.3 μM); 2g was found to be the best inhibitor (IC(50) = 0.11 μM), and 1g and 2g exhibited partially mixed inhibition with K(i) of 8.0 and 0.55 μM. The analysis of the structure–activity relationship revealed that the meta-substitutes improved the inhibitory activity of the inhibitors. Isothermal titration calorimetry (ITC) assays showed that 2g reversibly inhibited ImiS. The benzenesulfonamides exhibited synergistic antibacterial effects against E. coli BL21 (DE3) cells with ImiS, resulting in a 2–4-fold reduction in the MIC of imipenem and meropenem. Also, mouse experiments showed that 2g had synergistic efficacy with meropenem and significantly reduced the bacterial load in the spleen and liver after a single intraperitoneal dose. Tracing the ImiS in living E. coli cells by RS at a super-resolution level (3D-SIM) showed that the target was initially associated on the surface of the cells, then there was a high density of uniform localization distributed in the cytosol of cells, and it finally accumulated in the formation of inclusion bodies at the cell poles. Docking studies suggested that the sulfonamide group acted as a zinc-binding group to coordinate with Zn(ii) and the residual amino acid within the CphA active center, tightly anchoring the inhibitor at the active site. This study provides a highly promising scaffold for the development of inhibitors of ImiS, even the B2 subclasses of MβLs.

Metallo-beta-lactamase (MBL)-producing bacteria resistant to beta-lactam antibiotics are a serious threat to human health. Despite great efforts and important progress in the discovery of MBL inhibitors (MBLIs), there is none in clinical use. Herein, inhibitor complexes of the MBL CcrA were investigated by NMR spectroscopy to provide perspectives on the further development of 2-(triazolylthio)acetamide-type MBLIs. By using the NMR-based chemical shift perturbation (CSP) and direction of CSP methodologies together with molecular docking, the spatial orientation of three compounds in the CcrA active site was investigated (4-6). Inhibitor 6 showed the best binding affinity (K-d approximate to 2.3 +/- 0.3 mu M), followed by 4 (K-d approximate to 11 +/- 11 mu M) and 5 (K-d = 34 +/- 43 mu M), as determined from the experimental NMR data. Based on the acquired knowledge, analogues of other MBLIs (1-3) were designed and evaluated in silico with the purpose of examining a strategy for promoting their interactions with the catalytic zinc ions.

Inhibition of &beta, lactamases presents a promising strategy to restore the &beta, lactams antibacterial activity to resistant bacteria. In this work, we found that aromatic carboxyl substituted 2-triazolylthioacetamides 1a&ndash, j inhibited VIM-2, exhibiting an IC50 value in the range of 20.6&ndash, 58.6 &mu, M. The structure-activity relationship study revealed that replacing the aliphatic carboxylic acid with aromatic carboxyl improved the inhibitory activity of 2-triazolylthioacetamides against VIM-2. 1a&ndash, j (16 mg/mL) restored the antibacterial activity of cefazolin against E. coli cell expressing VIM-2, resulting in a 4&ndash, 8-fold reduction in MICs. The isothermal titration calorimetry (ITC) characterization suggested that the primary binding 2-triazolylthioacetamide (1b, 1c, or 1h) to VIM-2 was a combination of entropy and enthalpy contributions. Further, the crystal structure of VIM-2 in complex with 1b was obtained by co-crystallization with a hanging-drop vapour-diffusion method. The crystal structure analysis revealed that 1b bound to two Zn(II) ions of the enzyme active sites, formed H-bound with Asn233 and structure water molecule, and interacted with the hydrophobic pocket of enzyme activity center utilizing hydrophobic moieties, especially for the phenyl of aromatic carboxyl which formed &pi, &pi, stacking with active residue His263. These studies confirmed that aromatic carboxyl substituted 2-triazolylthioacetamides are the potent VIM-2 inhibitors scaffold and provided help to further optimize 2-triazolylthioacetamides as VIM-2 even or broad-spectrum M&beta, Ls inhibitors.

The traditional antibiotics have specific intracellular targets and disinfect in chemical ways, and the drug-resistance induced by the antibiotics has grown into an emerging threat. It is urgent to call for novel strategies and antibacterial materials to control this situation. Herein, we report a class of silver-decorated nanocomposite AgNPs@PCL

Aim: The discovery and development of novel broad-spectrum MβLs inhibitors are urgent to overcome antibiotic resistance mediated by MβLs. Methods & results: Herein, the synthesized 21 compounds exhibited potent inhibition to the clinically important MβLs (NDM-1, IMP-1 and ImiS) and effectively restored the antibacterial efficacy of cefazolin and imipenem against Escherichia coli harboring MβLs. 5b was first identified to be dual functional broad-spectrum MβLs inhibitor through assemblage of covalent and metal binding scaffold, which irreversibly inhibited B1, B2 MβLs via forming a Se–S covalent bond, and competitively inhibited B3 MβLs by coordinating the metals at active site. Conclusion: The designed compounds can serve as potent broad-spectrum MβLs inhibitors and combat MβLs-producing ‘superbug’ in combination with β-lactams.

The bacteria, harboring metallo-β-lactamases (MβLs), become resistant on most β-lactam antibiotics, specifically New Delhi metallo-β-lactamase-1 (NDM-1), which hydrolyzes almost all β-lactam antibiotics leading to bacterial multiple-drug resistance. It is highly desirable to develop effective NDM-1 inhibitors in reviving the efficacy of existing antibiotics. Here, we report a potent covalently reversible scaffold, 3-Bromopyruvate (3BP) to target the NDM-1 in vitro and in vivo. Enzymatic kinetic studies revealed that 3BP is capable of inhibiting the B1 and B2 MβLs and exhibited the best inhibition on NDM-1 with an IC50 of 2.57 μM, also, it was found to be a dose- and time-dependent inhibitor. The study of inhibition mechanism suggested that 3BP reversibly inactivate NDM-1, and may form a dynamic reversible covalent bond with cysteine at active site of the enzyme. Besides, 3BP effectively restored the activity of five β-lactam antibiotics on three clinical strains expressing NDM-1, resulting in 2–8-fold reduction in MIC. Moreover, the toxicity evaluation of 3BP against L929 mouse fibroblastic cells indicated that 3BP had low cytotoxicity, implying it may be used as lead molecule for future drug candidate.

The emergence of drug-resistant bacteria poses a serious threat to public health. The traditional antibiotics have specific intracellular targets and disinfect via chemical ways, which easily lead to the development of drug resistance, therefore, cationic peptides as promising antibiotic agents have attracted extensive attention due to their unique properties. Herein, we report a class of amphiphilic peptide-based pectinate polymers with primary amino groups. The polymers spontaneously self-assembled into the positively charged nanoparticles, which were evaluated and confirmed by scanning electron microscopy (SEM) and dynamic light scattering (DLS). Biological assays revealed that the nanoparticles showed broad-spectrum antibacterial efficacy against both Gram-positive and Gram-negative bacteria, exhibiting a MIC of 16 μg mL-1 against six clinical bacteria, namely, E. faecalis, S. aureus, MRSA, VRE, P. aeruginosa, and K. pneumonia, and three bacterial strains E. coli and E. coli producing NDM-1 and ImiS, and showed a sterilization rate of 95.6% and 94.7% on S. aureus and E. coli, respectively. Importantly, the nanoparticles did not result in drug-resistance for both the normal and drug-resistant bacteria tested after 14 passages and showed low toxicity on the mouse fibroblast cells (L929). The fluorescence staining, electrical conductivity, SEM, and surface plasmon resonance (SPR) characterization suggested that the nanoparticles initially bound to the surface of the bacteria, then pierced into the membranes of the bacteria with their phenyl groups, and finally disrupted the membranes, resulting in ions leaking out and thus exhibiting broad-spectrum antibacterial efficacy. This bactericidal mechanism that the nanoparticles employed does not lead the bacteria susceptible to developing drug resistance. This study provides a promising pathway for the development of the efficient antibacterial materials.

Antibiotic-resistant bacteria has become one of the greatest challenges to global human health today. Innovative strategies are needed to identify new therapeutic leads to tackle infections of drug-resistant Gram-negative bacteria. We herein synthesize a series of EB analogues to investigate their antibacterial activities. Select polar functionality at N-terminus of EB exhibited higher activities against multi-drug-resistant Gram-negative pathogens, including E. coli, P. aeruginosa and K. pneumoniae. EB analogue 4g and 4i exhibited potent antibacterial activities against E. coli-ESBL (MIC = 1–4 µg/mL) and E. coli producing NDM-1 (MIC = 4–32 µg/mL), which is superior to the traditional antibiotics (cefazolin, imipenem). Furthermore, the time-kill kinetics studies and the inhibition zone tests indicated that analogue 4i effectively and rapidly cause death of E. coli-ESBL and E. coli-NDM-1. Additionally, accumulation assays and SEM images showed that 4i could permeate bacterial membranes, leading to an irregular cell morphology. Importantly, bacterial resistance for analogue 4i was difficult to induce against E. coli-ESBL. EB analogues here reported low cytotoxicity against L-929 cells and mice model in vivo. We believe that EB analogues with polar functionality could play a pivotal role in the development of novel antibacterial agents in eradicating multi-drug-resistant Gram-negative pathogens infections.

Metallo-β-lactamases (MβLs) are the target enzymes of β-lactam antibiotic resistance, and there are no effective inhibitors against MβLs available for clinic so far. In this study, thirteen halogen-substituted triazolethioacetamides were designed and synthesized as a potent skeleton of MβLs inhibitors. All the compounds displayed inhibitory activity against ImiS with an IC50 value range of 0.032–15.64 μM except 7. The chlorine substituted compounds (1, 2 and 3) inhibited NDM-1 with an IC50 value of less than 0.96 μM, and the fluorine substituted 12 and 13 inhibited VIM-2 with IC50 values of 38.9 and 2.8 μM, respectively. However, none of the triazolethioacetamides exhibited activity against L1 at inhibitor concentrations of up to 1 mM. Enzyme inhibition kinetics revealed that 9 and 13 are mixed inhibitors for ImiS with Ki values of 0.074 and 0.27μM using imipenem as the substrate. Docking studies showed that 1 and 9, which have the highest inhibitory activity against ImiS, fit the binding site of CphA as a replacement of ImiS via stable interactions between the triazole group bridging ASP120 and hydroxyl group bridging ASN233.

Superbug infection caused by metallo-β-lactamases (MβLs) is a global public health threat. Previous studies reported that the thioesters specifically inhibited the B3 subclass MβL L1. In this work, nine amino acid thioesters 1-9 were synthesized, the activity evaluation revealed that all of these molecules exhibited broad-spectrum inhibitory efficacy against ImiS, IMP-1, NDM-1, and L1, with IC50 values range of 0.02-54.9 µM (except 5 and 7 on NDM-1), and 1 was found to be the best inhibitor with IC50 range of 0.02-16.63 µM. Minimal inhibitory concentration (MIC) assays showed that thioesters 1, 5 and 9 restored 2-32-fold antibacterial activity of cefazolin and/or imipenem against both Escherichia coli BL21 and DH10B strain expressing ImiS, L1, IMP-1 and NDM-1 (except 5 on NDM-1), and also, thioester 1 increased 2-4-fold antimicrobial activity of cefazolin on two clinical strains Pseudomonas aeruginosa and Klebsiella pneumoniae producing NDM-1. Stability evaluation indicated that thioester 1 was partially hydrolysed by MβLs to be converted into the mercaptoacetic acid, revealing that the thioester and its hydrolysate mercaptoacetic acid jointly inhibit MβLs. Isothermal titration calorimetry (ITC) monitoring showed that thioester 1 exhibited dose-dependent inhibition on four MβLs tested, and the binding of 1/L1 showed mainly enthalpy driven, while 1/NDM-1 was found to be more entropy driven. Docking studies suggested that 1 bound to Zn(II) ion(s) preferentially via its carboxylate group, while other moieties interacted mostly with the conserved active site residues.

The superbug infection caused by New Delhi metallo-β-lactamase (NDM-1) has become an emerging public health threat. Inhibition of NDM-1 has proven challenging due to its shuttling between pathogenic bacteria. A potent scaffold, diaryl-substituted thiosemicarbazone, was constructed and assayed with metallo-β-lactamases (MβLs). The obtained twenty-six molecules specifically inhibited NDM-1 with IC50 0.038–34.7 µM range (except 1e, 2e, and 3d), and 1c is the most potent inhibitor (IC50 = 0.038 µM). The structure-activity relationship of synthetic thiosemicarbazones revealed that the diaryl-substitutes, specifically 2-pyridine and 2-hydroxylbenzene improved inhibitory activities of the inhibitors. The thiosemicarbazones exhibited synergistic antimycobacterial actions against E. coli-NDM-1, resulted a 2–512-fold reduction in MIC of meropenem, while 1c restored 16–256-, 16-, and 2-fold activity of the antibiotic on clinical isolates ECs, K. pneumonia and P. aeruginosa harboring NDM-1, respectively. Also, mice experiments showed that 1c had a synergistic antibacterial ability with meropenem, reduced the bacterial load clinical isolate EC08 in the spleen and liver. This work provided a highly promising scaffold for the development of NDM-1 inhibitors.

We discovered a promising metallo-β-lactamase inhibitor, a DNA nanoribbon, by enzymatic kinetics and isothermal titration calorimetry evaluations. Atomic force microscopy, gel electrophoresis, competitive binding experiments, circular dichroic and thermal denaturation studies suggested that the DNA nanoribbon could bind to the enzyme through a minor groove.

The metallo-β-lactamases (MβLs) cleave the β-lactam ring of β-lactam antibiotics, conferring resistance against these drugs to bacteria. Twenty-four triazolylthioacetamides were prepared and evaluated as inhibitors of representatives of the three subclasses of MβLs. All these compounds exhibited specific inhibitory activity against NDM-1 with an IC50 value range of 0.15-1.90 μM, but no activity against CcrA, ImiS, and L1 at inhibitor concentrations of up to 10 μM. Compounds 4d and 6c are partially mixed inhibitors with K i values of 0.49 and 0.63 μM using cefazolin as the substrate. Structure-activity relationship studies reveal that replacement of hydrogen on the aromatic ring by chlorine, heteroatoms, or alkyl groups can affect bioactivity, while leaving the aromatic ring of the triazolylthiols unmodified maintains the inhibitory potency. Docking studies reveal that the typical potent inhibitors of NDM-1, 4d and 6c, form stable interactions in the active site of NDM-1, with the triazole bridging Zn1 and Zn2, and the amide interacting with Lys 211 (Lys224).