Antibacterial drug discovery in the resistance era

Leveraging molecular dynamics, physicochemical, and structural analysis to explore OMP33-36 protein as a drug target in Acinetobacter baumannii: An approach against nosocomial infection

The Acinetobacter baumannii is a member of the "ESKAPE" bacteria responsible for many serious multidrug-resistant (MDR) illnesses. This bacteria swiftly adapts to environmental cues leading to the emergence of multidrug-resistant variants, particularly in hospital/medical settings. In this work, we have demonstrated the outer membrane protein 33-36 (Omp33-36) porin as a potential therapeutic target in A. baumannii and the regulatory potential of phytocompounds using an in-silico drug screening approach. Omp33-36 protein receptor was retrieved from the protein data bank and characterized as a receptor protein. The possible compounds (ligands) from three plants namely Andrographis paniculata, Cascabela thevetia, and Prosopis cineraria, were evaluated for their potential against bacterial infections based on prior investigations and selected for further analysis. Initially, seventy potential phytocompounds were identified and retrieved from IMPPAT database, followed by Physio-chemical characterizations and toxicity assessment using swissADME and ProTox server respectively. 15 compounds have shown significant drug-likeliness and were implemented for their interaction analysis with Omp33-36 using Autodock Vina. The docking study presented seven compounds with the best binding affinities, ranging from -7.2 kcal/mol to -7.9 kcal/mol and further, based on the potential of these compounds, 4 phytocompounds were introduced for molecular dynamic simulation for 200ns. During MD simulation, compounds Prosogerin, Quercitin and Tamarixetin have shown a substantial affinity for the Omp33-36 protein and binding energy ranging from -18 to -33 kcal/mol. Overall, the analysis depicted the two compounds, Quercitin and Tamarixetin, with the most consistent interactions and indicated promise as drug leads in regulating A. baumannii infection. However, in-vitro and in-vivo experimental validation are required to propose the selected phytomolecules as a therapeutic lead against A. baumannii.

Natural sideromycins and siderophore-conjugated natural products as inspiration for novel antimicrobial agents

The widespread emergence of multidrug-resistant (MDR) Gram-negative pathogens has posed a major challenge to clinical anti-infective therapy, and new effective treatments are urgently needed. A promising "Trojan horse" strategy involves conjugating antibiotics to siderophore molecules; the resulting siderophore-antibiotic conjugates (SACs) deliver antibiotics directly into cells by hijacking the sophisticated iron transport systems of Gram-negative bacteria, bypassing the outer membrane permeability barrier to enhance uptake and antibacterial efficacy. The clinical release of the first siderophore-antibiotic conjugate, cefiderocol, has aroused tremendous interest in the field among researchers and pharmaceutical companies. To date, most of the reported SACs have focused on the conjugation of siderophores to traditional antibacterial drugs. However, these antibacterial agents designed on the basis of the traditional antibiotic skeleton theoretically bear the risk of cross-resistance caused by shared molecular scaffolds. In this case, exploring novel natural product antibacterial conjugate scaffolds to circumvent the risk of early cross-resistance represents a presumably more sustainable approach for the development of SACs. In this review, we systematically summarize the research progress on siderophore-natural product conjugates as novel antimicrobial agents reported since 2010. Additionally, we propose challenges to be overcome and prospects for future development in this field.

Stimuli-responsive dual-drug loaded microspheres with differential drug release for antibacterial and wound repair promotion

The healing of infected wounds is a complex and dynamic process requiring tailored treatment strategies that address both antimicrobial and reparative needs. Despite the development of numerous drugs, few approaches have been devised to optimize the timing of drug release for targeting distinct phases of infection control and tissue repair, limiting the overall treatment efficacy. Here, a stimuli-responsive microsphere encapsulating dual drugs was developed to facilitate differential drug release during distinct phases of antibacterial and repair promotion, thereby synergistically enhancing wound healing. Specifically, zeolite imidazolate backbone in poly (lactic-co-glycolic acid) (PLGA) microsphere was employed for the encapsulation of ciprofloxacin (CIP), responding to acidic environment of bacteria and releasing antibiotic for antibacterial therapy. Meanwhile, curcumin (CUR) encapsulated in PLGA exhibited a gradual release profile, contributing to synergistic antibacterial effects. During the tissue repair phase, near-infrared light stimulation of Fe3O4 embedded in PLGA generated heat, elevating the temperature to the glass transition point of PLGA, which significantly enhanced the release of CUR thereby promoting tissue repair. In vitro experiments demonstrated that the release of CIP and CUR achieved significant antibacterial effects in the early stages of treatment. Additionally, CUR could effectively enhance fibroblast migration and proliferation. In vivo studies using a mouse abscess model revealed that the microspheres exhibited remarkable antibacterial and wound-healing capabilities, effectively enhancing the re-epithelialization of wound tissue and reducing the infiltration of inflammatory cells. This study provides novel strategies for constructing drug delivery systems that match dynamic stages of wound healing, offering improved therapeutic outcomes for infected wounds.

Quaternized chitosan templated MoS2 nanohybrids for photothermal-enhanced synergistic antibacterial therapy

Bacterial infections have become a fatal issue for human health. The excessive use of antibiotics leads to bacterial resistance. It is of great importance to develop alternate antimicrobial nanomaterials for effective antibacterial therapy. Herein, we developed a simple one-step hydrothermal method to construct the antibacterial nanoplatform based on chitosan quaternary ammonium salt functionalized molybdenum disulfide nanohybrids (MoS2-QCS) with controllable morphology, surface composition, and structure. The photothermal performance of MoS2-QCS nanohybrids can be successfully optimized by regulating the morphology, surface composition, and structure by QCS during hydrothermal synthesis. The optimized MoS₂-QCS nanohybrids demonstrated satisfactory photothermal effects, excellent colloidal stability, and enhanced bacterial adhesion. In vitro experiments verified the synergistic antibacterial efficacy of MoS2-QCS nanohybrids, combining photothermal therapy with QCS to effectively inhibit both Gram-positive and Gram-negative bacteria. The nanohybrids exhibited excellent biocompatibility, indicating the suitability for biomedical applications. In vivo studies demonstrated their potent antibacterial activity against S. aureus, along with accelerated wound healing and enhanced tissue regeneration with minimal inflammatory response. The current work proposed a simple and effective strategy for precisely designing nanoplatforms with controllable morphology, surface composition, and structure for synergistic antimicrobial therapy. These results confirmed the great potential of tailored MoS2-QCS nanohybrids in effective synergistic antibacterial therapy.

A review of click chemistry in the synthesis of organophosphorus triazoles and their biological activities

Organophosphorus compounds, characterized by the incorporation of phosphorus into organic molecules, play a critical role in various fields such as medicine, agriculture, and industry. Their unique electronic properties and versatility make them essential in developing therapeutic agents, pesticides, and materials. One prominent class of organophosphorus compounds is organophosphorus heterocycles, which combine the benefits of both phosphorus and cyclic structures. Triazoles, a class of nitrogen-containing heterocyclic compounds, are particularly notable for their broad biological activities, including anticancer, antiviral, antibacterial, and antioxidant effects. Traditional methods for synthesizing triazoles often encounter challenges such as low yields and non-selective products, whereas click chemistry provides a more efficient and reliable alternative. The copper-catalyzed azide-alkyne [3 + 2] cycloaddition, a cornerstone of click chemistry, allows for the rapid and selective formation of triazoles under mild conditions. When functionalized with organophosphorus groups, triazoles not only retain but often enhance their biological activities, improving their potency, selectivity, and stability. This review covers the synthesis of organophosphorus-functionalized triazoles via click chemistry and explores their molecular structure, including the coordination chemistry of these compounds. The behavior and interactions of these organophosphorus derivatives with various metal ions are also addressed, as these interactions significantly influence their chemical reactivity, stability, and bioactivity.

Comparative lipidomics profiles of planktonic and biofilms of methicillin-resistant and -susceptible Staphylococcus aureus

Staphylococcus aureus is a significant human pathogen causing acute life-threatening, and chronic infections often linked to biofilms. This study conducted a comparative lipidomic analysis of a methicillin-resistant (MRSA) and a methicillin-susceptible (MSSA) S. aureus strain in both planktonic and biofilm cultures using liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR) spectroscopy. The developed protocol successfully differentiates between the strains in various living states (planktonic and biofilm) and growth media (Tryptic Soy Broth and Brain Heart Infusion) using S. aureus USA300 LAC (MRSA) and S. aureus Newman (MSSA). LC-MS and NMR lipidomics profiles revealed global differences and particular ones among the following classes of bacterial lipids: phosphatidylglycerols, diacylglycerols, monoglycosyldiacylglycerols, diglycosyldiacylglycerols, and cardiolipins. Lipid content was higher in the biofilm states for most of these classes. Growth media differences were significant, while differences between MRSA and MSSA were less pronounced but still detectable. Additionally, we provide data on hundreds of unknown compounds that differ based on living state, strain background, or growth media. This study offer insights into the dynamic nature of S. aureus lipid composition and the used methods are adaptable to other organisms.

Structure, Function, and Biosynthesis of Siderophores Produced by Streptomyces Species

Since the natural supply of iron is low, microorganisms acquire iron by secreting siderophores. Streptomyces is known for its abundant secondary metabolites containing various types of siderophores, including hydroxamate, catecholate, and carboxylate. These siderophores are mainly synthesized through the nonribosomal peptide synthase (NRPS) and non-NRPS pathways and are regulated by ferric uptake regulator and diphtheria toxin regulators. Although both NRPS and non-NRPS pathways adenylate substrates, they differ significantly in the catalytic logic. Siderophores produced by Streptomyces play important roles in fields of agriculture, medicine, and environment. However, their structure, function, and synthetic mechanisms have been inadequately summarized. Therefore, this Review aimed to provide an overview of the classification, structure, biosynthesis, regulation, and applications of siderophores produced by Streptomyces. Finally, the need for a comprehensive and well-defined mechanism for synthesizing siderophores from Streptomyces was highlighted to further promote their commercialization and application in agriculture, medicine, and other areas.

A novel function of short cationic peptide FP-CATH9 without antimicrobial activity reverses resistance to minocycline in common multidrug-resistant gram-negative bacteria

The increase in bacterial resistance to minocycline and other tetracyclines poses a serious threat to global public health. Because the development of new antibiotics has proven problematic, antibiotic sensitization therapy is now an effective coping strategy. While antimicrobial peptides generally exhibit broad-spectrum antibacterial activity and good biocompatibility, naturally truncated portions of antimicrobial peptides (such as snake cathelicidin) often do not exhibit antimicrobial activity, and their function remains unknown. FP-CATH9 is a short cationic peptide derived from FP-CATH (snake cathelicidin antimicrobial peptide) with an amphiphilic α-helical structure and no discernible antibacterial activity. However, FP-CATH9 was previously found to significantly enhance the activity of minocycline against gram-negative bacteria. In the present paper, clinically relevant minocycline-resistant gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa) were used as test bacteria for antibiotic sensitization screening. The sensitization activity of FP-CATH9 was found to be dose dependent in a double-dilution assay. The synergistic activity of FP-CATH9 on minocycline was subsequently determined using the checkerboard method. An ethidium bromide efflux test revealed that FP-CATH9 caused an accumulation of minocycline in bacteria. Additionally, FP-CATH9 exhibited low hemolytic activity on red blood cells and low cytotoxicity on Raw264.7 cells. In an in vivo model of bacterial infection, FP-CATH9 combined with minocycline exhibited an 80% protective effect on Galleria mellonella larvae infected with multidrug-resistant K. pneumoniae. In summary, FP-CATH9 is a new antibiotic adjuvant that reverses the resistance of gram-negative bacteria to minocycline by increasing intracellular accumulation of minocycline. This finding has broad application potential.IMPORTANCEThe existence of the efflux pump system enables bacteria to expel antibiotics, reduce the concentration of antibiotics in cells, and make antibiotics unable to effectively inhibit or kill bacteria, which is one of the main mechanisms of bacterial resistance to antibiotics. However, some efflux pumps are substrate specific, while others are with a wide range of substrates. In this study, FP-CATH9 as a new antibiotic adjuvant can specifically reverse the resistance of gram-negative bacteria to minocycline by increasing the intracellular accumulation of minocycline in bacteria and provides a new way to solve the increasing problem of bacterial drug resistance.

Discovery of a Pseudomonas aeruginosa-specific small molecule targeting outer membrane protein OprH-LPS interaction by a multiplexed screen

The surge of antimicrobial resistance threatens efficacy of current antibiotics, particularly against Pseudomonas aeruginosa, a highly resistant gram-negative pathogen. The asymmetric outer membrane (OM) of P. aeruginosa combined with its array of efflux pumps provide a barrier to xenobiotic accumulation, thus making antibiotic discovery challenging. We adapted PROSPECT, a target-based, whole-cell screening strategy, to discover small molecule probes that kill P. aeruginosa mutants depleted for essential proteins localized at the OM. We identified BRD1401, a small molecule that has specific activity against a P. aeruginosa mutant depleted for the essential lipoprotein, OprL. Genetic and chemical biological studies identified that BRD1401 acts by targeting the OM β-barrel protein OprH to disrupt its interaction with LPS and increase membrane fluidity. Studies with BRD1401 also revealed an interaction between OprL and OprH, directly linking the OM with peptidoglycan. Thus, a whole-cell, multiplexed screen can identify species-specific chemical probes to reveal pathogen biology.

Activating Thermoplastic Polyurethane Surfaces with Poly(ethylene glycol)-Based Recombinant Human α-Defensin 5 Monolayers for Antibiofilm Activity

Addressing multidrug-resistant microbial infections linked to implantable biomedical devices is an urgent need. In recent years, there has been an active exploration of different surface coatings to prevent and combat drug-resistant microbes. In this research, we present a facile chemical modification of thermoplastic polyurethane (TPU) surfaces with poly(ethylene glycol)-based recombinant human α-defensin 5 (HD5) protein with antimicrobial activity. TPU is one of the most relevant materials used for medical devices with good mechanical properties but also good chemical resistance, which makes it difficult to modify. The chemical modification of TPU surfaces is achieved via a three-step procedure based on (i) TPU activation using hexamethylene diisocyanate (HDI); (ii) interfacial reaction with poly(ethylene glycol) (PEG) derivatives; and finally, (iii) a facile click reaction between the PEG-maleimide terminated assembled monolayers on the TPU and the cysteine (-thiol) termination of the recently designed recombinant human α-defensin 5 (HD5) protein. The obtained PEG based HD5 assembled monolayers on TPU were characterized using a surface science multitechnique approach including scanning electron microscopy, atomic force microscopy, contact angle, and X-ray photoelectron spectroscopy. The modified TPU surfaces with the HD5 protein derivative exhibit broad-spectrum antibacterial properties reducing biofilm formation against Pseudomonas aeruginosa (Gram-negative), methicillin-resistant Staphylococcus aureus (MRSA) (Gram-positive) and methicillin-resistant Staphylococcus epidermidis (MRSE) (Gram-positive). These findings underscore the substantial potential of protein-modified TPU surfaces for applications in combating bacterial infections associated with implantable materials and devices.

Unveiling the multifaceted bioactivity of copper(II)-Schiff base complexes: a comprehensive study of antioxidant, anti-bacterial, anti-inflammatory, enzyme inhibition and cytotoxic potentials with DFT insights

The rise of various diseases demands the development of new agents with antioxidant, antimicrobial, anti-inflammatory, enzyme-inhibiting, and cytotoxic properties. In this study, heterocyclic Schiff base complexes of Cu(II) featuring a benzo[b]thiophene moiety were synthesized and their biological activities evaluated. The complexes were characterized using FT-IR, UV-Vis, and EPR spectroscopy, TG-DTG analysis, magnetic moment measurements, molar conductivity measurements, and elemental analyses. Density functional theory (DFT) calculations were used to optimize the theoretical molecular orbital energies of the copper complexes. The complexes exhibited square pyramidal and square planar geometries. Biological assays demonstrated that these complexes generally outperformed the Schiff base ligands for various activities. The antioxidant capacity, measured via the DPPH assay in methanol, was comparable to those of the BHT and ascorbic acid standards, with 4BNPC showing the lowest IC50 value, which was attributed to the free OH group rather than coordination to the metal center. The anti-bacterial activity was assessed using the agar disc diffusion method against E. coli, P. aeruginosa, B. subtilis, and S. aureus, with BAC showing the largest inhibition zone compared to the others and ciprofloxacin as the reference. The anti-inflammatory activity, evaluated by the HRBC membrane stabilization method, showed that the 4BNPC Cu(II) complex had moderate activity similar to that of diclofenac. Enzyme inhibition studies against α-amylase revealed that the BAC complexes had the highest inhibition values, surpassing those of the Schiff base ligands. Cytotoxicity was assessed using Trypan blue exclusion for DLA and HepG2 cancer cell lines, and the MTT assay for H9c2 human cells. BMPC demonstrated superior cytotoxicity at both high and low concentrations against the normal H9c2 cell line. Among the tested compounds, BNPC showed moderate inhibition against HepG2 cells, while BMPC exhibited the greatest cytotoxicity at higher concentrations, particularly reaching nearly 100% cell death at 200 μg mL-1 in DLA cell lines. This suggests that BMPC is a promising candidate for further pharmacological research, particularly against DLA cells.

Enhanced chemodynamic porphyrin-modified magnetite nanoagents: A triple-action strategy for potent antimicrobial therapy and wound healing

The rise of drug-resistant bacteria, including multidrug-resistant (MDR) strains, has exposed the limitations of current antibiotic treatments. Chemodynamic therapy (CDT) has emerged as a promising approach due to its ability to generate reactive oxygen species (ROS) through Fenton or Fenton-like reactions in infection microenvironments (IMEs). However, the short lifespan, limited diffusion range of ·OH, and restricted variety of ROS reduce the effect of CDT. This study developed amine porphyrins (TAPP)-functionalized Fe3O4 nanoparticles (Fe3O4@TAPP NPs) as a multifunctional antibacterial platform. The TAPP layer can not only trap bacteria through electrostatic attraction in acidic environments but also increase the localized heat upon near-infrared (660 nm) excitation, reducing the effective action distance and boosting the production rate of ·OH. Notably, TAPP was covalently bonded to Fe3O4 nanoparticles via its amine groups and the carboxylic groups on Fe3O4, preventing TAPP self-aggregation under physiological conditions, and preserving the PDT effect. Therefore, the TAPP layer on Fe3O4 nanoparticles performs three functions, resolving the three limitations simultaneously to enhance CDT in a triple-action strategy. The developed Fe3O4@TAPP NPs exhibit improved antibacterial efficiency both in vitro and in vivo. Overall, this study provides an innovative strategy to construct an antibacterial nanoplatform for synergistically enhanced CDT antibacterial treatment, exhibiting great potential for future biomedical applications.

Antimicrobial Properties of Hive Products and Their Potential Applications in Human and Veterinary Medicine

Hive products, encompassing honey, propolis, bee venom, royal jelly, and pollen, are recognized for their antimicrobial and therapeutic properties. This review examines their chemical composition, explores their mechanisms of action, and discusses their potential applications in both human and veterinary medicine, particularly in addressing the challenge of antimicrobial resistance. This study utilized a comprehensive literature search strategy, gathering data from Google Scholar, MEDLINE PubMed, SciELO, and SCOPUS databases. Relevant search terms were employed to ensure a thorough retrieval of the pertinent literature. Honey, rich in bioactive compounds such as hydrogen peroxide and methylglyoxal, effectively disrupts biofilms and combats multi-drug-resistant pathogens, showing promise in treating a range of infections. Propolis, with its flavonoids and phenolic acids, demonstrates synergistic effects when used in conjunction with antibiotics. Bee venom, particularly its component melittin, exhibits antibacterial and immunomodulatory properties, although further research is needed to address toxicity concerns. Pollen and royal jelly demonstrate broad-spectrum antimicrobial activity, which is particularly relevant to animal health. Existing pre-clinical and clinical data support the therapeutic potential of these hive products. Hive products represent a vast and largely untapped natural resource for combating antimicrobial resistance and developing sustainable therapies, particularly in the field of veterinary medicine. However, challenges remain due to the inherent variability in their composition and the lack of standardized protocols for their preparation and application. Further research is essential to fully elucidate their mechanisms of action, optimize formulations for enhanced efficacy, and establish standardized protocols to ensure their safe and effective clinical use.

Antimicrobial Phenolic Materials: From Assembly to Function

Infectious diseases pose considerable challenges to public health, particularly with the rise of multidrug-resistant pathogens that globally cause high mortality rates. These pathogens can persist on surfaces and spread in public and healthcare settings. Advances have been made in developing antimicrobial materials to reduce the transmission of pathogens, including materials composed of naturally sourced polyphenols and their derivatives, which exhibit antimicrobial potency, broad-spectrum activity, and a lower likelihood of promoting resistance. This review provides an overview of recent advances in the fabrication of antimicrobial phenolic biomaterials, where natural phenolic compounds act as active antimicrobial agents or encapsulate other antimicrobial agents (e.g., metal ions, antimicrobial peptides, natural biopolymers). Various forms of phenolic biomaterials synthesized through these two strategies, including antimicrobial particles, capsules, hydrogels, and coatings, are summarized, with a focus on their application in wound healing, bone repair and regeneration, oral health, and antimicrobial coatings for medical devices. The potential of these advanced phenolic biomaterials provides a promising therapeutic approach for combating antimicrobial-resistant infections and reducing microbial transmission.

Discovery of Novel FtsZ Inhibitors With Antimicrobial Activity by Virtual Screening and In Vitro Biological Evaluation

The filamentous temperature-sensitive protein Z (FtsZ) plays a vital role in bacterial division, making it an important antibacterial target. The inhibitor activity targeting the cleft between the H7 helix and the C-terminal substructural domain exhibited superior binding compared to the GTP binding site. This highlights the potential of the cleft as a promising target for further inhibitor discovery. In this study, we established a virtual screening (VS) pipeline using Discovery Studio software and employed FRED for molecular docking and Functional-Class Fingerprints_6 (FCFP_6) for molecular clustering, resulting in the identification of 38 potentially active compounds. These 38 compounds were then subjected to the following FtsZ inhibition assays, resulting in the four active compounds B6, B21, B26, and B31. Further experiments showed that compounds B6 and B26 exhibited antimicrobial activity with minimum inhibitory concentration (MIC) values of 8 and 32 µg/mL. Finally, molecular dynamics (MD) was used to analyze the binding modes of the protein-ligand. In addition, we predicted the physicochemical properties and toxicity of B6 and B26. In summary, our study successfully identified novel FtsZ inhibitors with antimicrobial activity through VS and in vitro biological evaluation, demonstrating their potential for further investigation.

Photoantimicrobial anthraquinones in Australian fungi of the genus Cortinarius

Dermocyboid Cortinarius species of both hemispheres are usually intensely colored and known to contain anthraquinones. Australian dermocyboid fungi have distinct evolutionary histories which are clearly different from Northern Hemisphere species of similar appearance. Allopatric speciation often results in different metabolic adaptations. We were especially interested in the diversity of anthraquinonic pigments and in their photoantimicrobial potential. In this study 33 dried samples from eighteen Australian dermocyboid Cortinarius taxa were extracted with methanol and analyzed via HPLC-DAD-MS. The 9,10-dimethylanthracene (DMA) assay was used to measure the extracts' ability to produce singlet oxygen after irradiation. Furthermore, a photoantimicrobial screening method based on the protocols of Clinical and Laboratory Standards Institute (CLSI) and European Committee on Antimicrobial Susceptibility (EUCAST), employing the common human pathogens Candida albicans, Escherichia coli, and Staphylococcus aureus was used to identify photoantimicrobials. Based on chromatography, mass spectrometry, and UV/Vis data, peaks were annotated according to literature and in-house data. A chemotaxonomic pigment analysis was established to cluster the species according to their major anthraquinones and to allow identification of the groups by a minimum number of pigments. In agreement with the recorded pigment pattern of the photoactive anthraquinones, nine Cortinarius species (C. alienatus, C. atropurpureus, C. austrovenetus, C. basirubescens, C. canarius, C. clelandii 2, C. globuliformis, C. persplendidus 1, C. sp. "honey pileus 1") showed at least 70 % inhibition of Staphylococcus aureus (Gram-positive bacteria) growth under light irradiation (λ = 428 / 478 nm, H = 30 J/cm2, c = 50 μg/mL, pre-illumination time (tPI) = 60 min) in the photoantimicrobial screening. The extracts of three species (C. alienatus, C. austrovenetus, and C. clelandii 2) showed additional photoactivity against Candida albicans (yeast) under the same conditions. Several relevant (photo)antimicrobials were identified: Emodin, dermocybin, skyrin, physcion (synonym: parietin), 7,7'-biphyscion, and hypericin; From the photoactive extracts, that were not reported to contain photoactive compounds before, austrocortinin and xanthorin were isolated and used for further testing. For austrocortinin a singlet oxygen yield of 0.03 (reference: [Ru(bpy3)Cl2], d4-MeOH) was detected. Accordingly, the anthraquinone did not show activity in the photoantimicrobial assay. Xanthorin, with a singlet oxygen yield of 0.10, led to an inhibition of growth of 78.1 % against Staphylococcus aureus (4.00 μg/mL, λ = 428 nm, 30 J/cm2, tPI = 60 min).

A slime-inspired phycocyanin/κ-carrageenan-based hydrogel bandage with ultra-stretchability, self-healing, antioxidative, and antibacterial activity for wound healing

Hydrogels have attracted extensive attention as wound dressing owing to their excellent multifunctionality, flexibility, and biocompatibility. Due to the frequent movement and stretching of skin as well as complex surface of wound, traditional wound dressings have difficulty to adapt to motion and irregular wounds. Furthermore, excessive reactive oxygen species (ROS) and bacterial infection can induce delayed wound healing. To this end, we developed a set of versatile phycocyanin-based dual network hydrogels (PPC hydrogels) with polyvinyl alcohol (PVA) and κ-carrageenan (CRG) as substrate via forming of borate ester bonds, hydrogen bonds, and electrostatic interaction. The PPC hydrogels not only possessed adaptivity, ultra-stretchability (7036.12 %), efficient self-healing and injectability, but also possessed antioxidative and antibacterial capacities conferred by C-phycocyanin (PC) and rhein. Moreover, the hydrogels also exhibited excellent hemostatic ability and high biocompatibility. More remarkably, the PPC-I hydrogel could accelerate wound healing by effect of anti-inflammation (downregulating TNF-α and IL-6) and promoting collagen deposition and angiogenesis (upregulating CD31), which may be utilized as hydrogel bandages and applied to motion and irregular wounds, thereby promising the application prospect of the hydrogels as wound dressing.

Impairing protein-protein interactions in an essential tRNA modification complex: An innovative antimicrobial strategy against Pseudomonas aeruginosa

Protein-protein interactions (PPIs) have been recognized as a promising target for the development of new drugs, as proved by the growing number of PPI modulators reaching clinical trials. In this context, peptides represent a valid alternative to small molecules, owing to their unique ability to mimic the target protein structure and interact with wider surface areas. Among the possible fields of interest, bacterial PPIs represent an attractive target to face the urgent necessity to fight antibiotic resistance. Growing attention has been paid to the YgjD/YeaZ/YjeE complex responsible for the essential t6A37 tRNA modification in bacteria. We previously identified an α-helix on the surface of Pseudomonas aeruginosa YeaZ, crucial for the YeaZ-YeaZ homodimer formation and the conserved YeaZ-YgjD interactions. Herein, we present our studies for impairing the PPIs involved in the formation of the YeaZ dimers through synthetic peptide derivatives of this helical moiety, both in vitro with purified components and on P. aeruginosa cells. Our results proved the possibility of targeting those PPIs which are usually essential for protein functioning and thus are refractory to mutational changes and antibiotic resistance development.

Ester derivatives of Dictyostelium differentiation-inducing factors exhibit antibacterial activity, possibly via a prodrug-like function

OBJECTIVE

Dictyostelium differentiation-inducing factors 1 and 3 [DIF-1 (1) and DIF-3 (2), respectively], along with their derivatives, such as Ph-DIF-1 (3) and Bu-DIF-3 (4), demonstrate antibacterial activity in vitro against Gram-positive bacteria, including methicillin-sensitive Staphylococcus aureus (MSSA), methicillin-resistant S. aureus (MRSA), vancomycin-sensitive Enterococcus faecalis (VSE), and vancomycin-resistant Enterococcus faecium [VRE (VanA)]. This study investigates the therapeutic potential of DIF compounds against these Gram-positive bacteria.

RESULTS

In vitro tests revealed that the antibacterial activity of 3 and 4 was lost in the presence of human serum albumin (HSA), suggesting that HSA might inhibit their effectiveness. Further evaluation of less hydrophobic derivatives, DIF-1-NH2 (5) and NH2-Bu-DIF-3 (6), showed no antibacterial activity, even in the absence of HSA. However, ester derivatives Ph-DIF-1(AHA) (7) and Bu-DIF-3(2Ac) (8) exhibited antibacterial activity against the target bacteria in vitro, although this activity was also lost in the presence of HSA. We hypothesize that these ester derivatives may function as prodrugs, with their antibacterial activity possibly restored by hydrolysis through bacterial esterases. The results suggest that suitable ester modifications could enhance the in vivo antibacterial potential of DIF compounds, particularly if they can bypass HSA binding and be activated by bacterial enzymes.

Study on the Mechanism of Black Phosphorus Nanosheets Loading Sr2+ Used in Photothermal Antibacterial Treatment

Purpose

Bacterial infections seriously affect the health of patients and their incidence is very high. Photothermal therapy has shown promising prospects in the treatment of bacterial infections as it can effectively kill bacteria and reduce inflammation. Black phosphorus (BP) is an emerging nanoparticle that can generate heat under the action of near-infrared light, it can safely and effectively kill bacteria through photothermal therapy. In this experiment, black phosphorus was used as a photothermal agent to kill bacteria and strontium ions were loaded onto BP to enhance its stability and antibacterial performance.

Methods

BP was obtained by liquid phase exfoliation and Sr2+ was loaded onto the surface of BP by electrostatic interaction.

Results

BP-Sr was synthesized via electrostatic interactions and characterized using various techniques. The cytocompatibility of BP-Sr was evaluated by CCK8 assay and live/dead staining which showed no significant cytotoxicity with a concentration not exceed 50 μg/mL. Meanwhile, the antibacterial effects showed 99% of bacteria died after 10 min under the action of a 2 W/cm2 laser and the structure of bacteria was destroyed. Finally, the transcriptomic results suggest that bacteria death may be related to membrane destruction, metabolic disorders, and transport damage. HE staining and Gram staining also showed that inflammation was significantly alleviated after laser treatment.

Conclusion

These findings propose a great solution for bacterial infection and also enrich the theoretical framework supporting the application of BP-Sr in the field of antibiosis.

Advances in peptide/polymer antimicrobial assemblies

Antimicrobial peptides (AMPs) have been extensively exploited as promising drugs to cope with antibiotic-resistant bacteria in clinical treatment. Peptide/polymer assembly provides a particularly important contribution to this topic and has emerged as a new paradigm for the development of nano-antimicrobial systems with previously unattainable outcomes. In this review article, we systematically summarize the recent advances in antimicrobial peptide/polymer assemblies. We describe a brief background and several classified systems based on peptide/polymer assemblies. We discuss the molecular design and the general rules behind the assembled nanostructures and bioactivities. The key role of polymers in improving the antimicrobial activity, stability, cytotoxicity, and bioavailability of peptides is emphasized based on the reported systems. The resulting peptide/polymer assemblies with stimuli-responsiveness, value-added properties and potential applications are demonstrated. The outlook of the antimicrobial peptide/polymer assemblies is also presented from the viewpoint of bio-applications.

A benzoxazolyl urea inhibits VraS and enhances antimicrobials against vancomycin intermediate-resistant Staphylococcus aureus

Vancomycin intermediate-resistant Staphylococcus aureus (VISA) is a pathogen of concern. VraS, a histidine kinase, facilitates the VISA phenotype. Here, we reveal a benzoxazolyl urea (chemical 1) that directly inhibits VraS and enhances vancomycin to below the clinical breakpoint against an archetypal VISA strain, Mu50. 50 μM of 1 enhances vancomycin 16-fold to 0.25 μg/mL. The MIC of oxacillin is enhanced 32-fold to 8 μg/mL, only slightly above its clinical breakpoint. The chemical also showed promising enhancement of oxacillin against several MRSA strains. 1 shows ∼30 % inhibition of ATPase activity in VraS and reduces vra gene auto-upregulation typical upon vancomycin exposure. Therefore, 1 inhibits VraS to block normal vra operon function, leading to potent enhancement of cell wall-directed antibiotics. Interestingly, a molecular modeling approach suggests 1 does not displace ATP from the active site, but acts elsewhere. While VraS inhibitors have previously been reported to function against MRSA, to the best of our knowledge, this is the first direct VraS inhibitor ever reported that shows significant enhancement of vancomycin against VISA.

Antarmycins: Discovery, Biosynthesis, Anti-pathogenic Bacterial Activity, and Mechanism of Action from Deep-Sea-Derived Pseudonocardia antarctica

The rapid emergence of antimicrobial-resistant pathogenic microbes has accelerated the search for novel therapeutic agents. Here we report the discovery of antarmycin A (1), an antibiotic containing a symmetric 16-membered macrodiolide core with two pendant vancosamine moieties, one of which is glucosylated, from deep-sea-derived Pseudonocardia antarctica SCSIO 07407. The biosynthetic gene cluster of 1 was identified on a giant plasmid featuring transferable elements. In-depth biosynthetic investigation enabled us to (i) identify a set of seven genes associated with the product of the vancosamine moiety; (ii) discover two glycosyltransferases dedicated to the transfer of pendant sugars; and (iii) isolate rhamnose-modified antarmycin B (2) and a deglucosylated derivative antarmycin C (3) from genetically engineered mutant strains. Antibacterial assays revealed that 1 displays superior antibacterial properties with potent in vitro activities against the critical priority pathogens, multidrug-resistant Enterococcus faecium and methicillin-resistant Staphylococcus aureus, fast bacterial killing, insusceptibility to antimicrobial resistance, and high in vivo efficiency in infection models. Mechanistic investigations revealed that 1 disrupts the bacterial cell membrane through a mechanism involving interactions between the vancosamine moieties and membrane-embedded phosphatidylglycerol/phosphatidylethanolamine. The results provide insights into the biological generation of vancosamine in natural products and demonstrate the potential of 1 as an effective lead to address the growing antimicrobial resistance threats.

A supramolecular diazapyrene radical assembly with NIR absorption for selective photothermal antibacterial activity

A supramolecular radical assembly that can be induced in situ by facultative anaerobic bacteria has been reported and used for selective near-infrared (NIR) photothermal antibacterial action. Herein, we report the synthesis of a water-soluble diazapyrene derivative (DAPNP), which could be in situ initiated into the corresponding radicals by facultative anaerobic bacteria, such as E. coli or S. aureus. The introduction of cucurbit[10]uril (CB[10]) alters the stacking mode of the diazapyrene radical cations, resulting in a redshift of their characteristic absorption peak from the visible region to the NIR region. Under 660 nm laser irradiation, the in situ-induced supramolecular radical assembly exhibits great photothermal conversion properties and achieves highly efficient antibacterial activity (up to 98%). In contrast, with the aerobic B. subtilis it is difficult to induce the formation of diazapyrene radical cations in situ and maintain good activity under light irradiation. In addition, DAPNP@CB[10] exhibits excellent biocompatibility and has great potential as an intelligent photothermal material for antibacterial applications.

Establishing the Comprehensive Structure-Activity Relationship of the Natural Antibiotic Kibdelomycin/Amycolamicin

Kibdelomycin (KBD) and amycolamicin (AMM) are potent natural antibiotics effective against antibiotic-resistant Gram-positive pathogens, including vancomycin-intermediate Staphylococcus aureus (S. aureus, VISA), methicillin-resistant S. aureus (MRSA), and quinolone-resistant S. aureus (QRSA). Their antibacterial activity stems from an unprecedented dual mechanism: the lower binding sites occupy the adenosine triphosphate (ATP) binding pocket of bacterial type II topoisomerases, while the upper binding sites disrupt the enzyme dimer interface. This dual action, combined with their unique chemical structures, positions KBD and AMM as promising scaffolds for developing new antibiotics. However, the structure-activity relationship (SAR) of KBD/AMM remains underexplored due to their highly complex chemical structures. In this study, we utilized total synthesis to produce KBD/AMM analogs with various site modifications and evaluated their antimicrobial activities. Our findings establish the first comprehensive SAR for KBD/AMM, paving the way for the development of novel KBD/AMM-based antibiotics.

Antistaphylococcal Triazole-Based Molecular Hybrids: Design, Synthesis and Activity

BACKGROUND

In the era of resistance, the design and search for new "small" molecules with a narrow spectrum of activity that target a protein or enzyme specific to a certain bacterium with high selectivity and minimal side effects remains an urgent problem of medicinal chemistry. In this regard, we developed and successfully implemented a strategy for the search for new hybrid molecules, namely, the not broadly known [2-(3-R-1H-[1,2,4]-triazol-5-yl)phenyl]amines. They can act as "building blocks" and allow for the introduction of certain structural motifs into the desired final products in order to enhance the antistaphylococcal effect.

METHODS

The "one-pot" synthesis of the latter is based on the conversion of substituted 4-hydrazinoquinazolines or substituted 2-aminobenzonitriles and carboxylic acid derivatives to the target products. The possible molecular mechanism of the synthesized compounds (DNA gyrase inhibitors) was investigated and discussed using molecular docking, and their further study for antistaphylococcal activity was substantiated.

RESULTS

A significant part of the obtained compounds showed high antibacterial activity against Staphylococcus aureus (MIC: 10.1-62.4 µM) and 5-bromo-2-(3-(furan-3-yl)-1H-1,2,4-triazol-5-yl)aniline and 5-fluoro-2-(3-(thiophen-3-yl)-1H-1,2,4-triazol-5-yl)aniline, with MICs of 5.2 and 6.1 µM, respectively, approaching the strength of the effect of the reference drug, "Ciprofloxacin" (MIC: 4.7 µM). The conducted SAR and ADME analyses confirm the prospects of the further structural modification of these compounds. The obtained [2-(3-R-1H-[1,2,4]-triazol-5-yl)phenyl]amines reveal significant antimicrobial activity and deserve further structural modification and detailed study as effective antistaphylococcal agents. The SAR analysis revealed that the presence of a cycloalkyl or electron-rich heterocyclic fragment in the third position of the triazole ring was essential for the antibacterial activity of the obtained compounds. At the same time, the introduction of a methyl group into the aniline moiety led to an enhancement of activity. The introduction of halogen into the aniline fragment has an ambiguous effect on the level of antistaphylococcal activity and depends on the nature of the substituent in the third position.

CONCLUSIONS

Obtained [2-(3-R-1H-[1,2,4]-triazol-5-yl)phenyl]amines reveal significant antistaphylococcal activity and deserve for further detailed study as effective antibacterial agents.

Discovery of Quinazolone Pyridiniums as Potential Broad-Spectrum Antibacterial Agents

The overprescription of antibiotics in medicine and agriculture has accelerated the development and spread of antibiotic resistance in bacteria, which severely limits the arsenal available to clinicians for treating bacterial infections. This work discovered a new class of heteroarylcyanovinyl quinazolones and quinazolone pyridiniums to surmount the increasingly severe bacterial resistance. Bioactive assays manifested that the highly active compound 19a exhibited strong inhibition against MRSA and Escherichia coli with extremely low MICs of 0.5 μg/mL, being eightfold more active than that of norfloxacin (MICs = 4 μg/mL). The highly active 19a with rapid bactericidal properties displayed imperceptible resistance development trends, negligible hemolytic toxicity, and effective biofilm inhibitory effects. Preliminary explorations on antibacterial mechanisms revealed that compound 19a could cause membrane damage, embed in intracellular DNA to hinder bacterial DNA replication, and induce metabolic dysfunction. Surprisingly, active 19a was found to trigger the conformational change in PBP2a of MRSA to open the active site, which might account for its high inhibition against MRSA. In addition, the little effect of molecule 19a on the production of reactive oxygen species indicated that bacterial death was not caused by oxidative stress. The above comprehensive analyses highlighted the large potential of quinazolone pyridiniums as multitargeting broad-spectrum antibacterial agents.

Refactoring the pikromycin synthase for the modular biosynthesis of macrolide antibiotics in E. coli

While engineering modular polyketide synthases (PKSs) using the recently updated module boundary has yielded libraries of triketide-pentaketides, this strategy has not yet been applied to the combinatorial biosynthesis of macrolactones or macrolide antibiotics. We developed a 2-plasmid system for the construction and expression of PKSs and employed it to obtain a refactored pikromycin synthase in E. coli that produces 85 mg of narbonolide per liter of culture. The replacement, insertion, deletion, and mutagenesis of modules enabled access to hexaketide, heptaketide, and octaketide derivatives. Supplying enzymes for desosamine biosynthesis and transfer enabled production of narbomycin, pikromycin, YC-17, methymycin, and 6 derivatives thereof. Knocking out pathways competing with desosamine biosynthesis and supplying the editing thioesterase PikAV boosted the titer of narbomycin 55-fold to 37 mgL-1. The replacement of the 3rd pikromycin module with its 5th yielded a new macrolide antibiotic and demonstrates how libraries of macrolide antibiotics can be readily accessed.

Fangchinoline eliminates intracellular Salmonella by enhancing lysosomal function via the AMPK-mTORC1-TFEB axis

INTRODUCTION

Salmonella, a foodborne zoonotic pathogen, is a significant cause of morbidity and mortality in animals and humans globally. With the prevalence of multidrug-resistant strains, Salmonellosis has become a formidable challenge. Host-directed therapy (HDT) has recently emerged as a promising anti-infective approach for treating intracellular bacterial infections.

OBJECTIVES

Plant-derived natural products, owing to their structural and functional diversity, are increasingly being explored and utilized as encouraging candidates for HDT compounds. This study aims to identify and screen natural compounds with potential as HDT for the treatment of intracellular Salmonella infections.

METHODS

A cell-based screening approach was deployed to identify natural compounds capable of mitigating the intracellular replication of S. enterica. Safety and efficacy of the candidate compounds were evaluated using multiple animal models. RNA sequencing, ELISA, and immunoblotting analyses were conducted to elucidate the underlying mechanisms of action.

RESULTS

Our results reveal that fangchinoline (FAN) effectively reduces S. enterica survival both in vitro and in vivo. Meanwhile, FAN also displays anti-infective activity against other intracellular pathogens, including multidrug-resistant isolates. A 14-day safety evaluation in mice showed no significant toxic or adverse effects from FAN administration. RNA sequencing analysis reveals an upregulation of lysosome pathways in S. enterica-infected cells treated with FAN. Mechanistic studies indicate that FAN increases acid lysosomal quantities and fosters autophagic response in Salmonella-infected cells via the AMPK-mTORC1-TFEB axis. In addition, FAN alleviates the inflammatory response in Salmonella-infected cells by inactivating the NF-κB pathway.

CONCLUSION

Our findings suggest that FAN represents a lead HDT compound for tackling recalcitrant infections caused by intracellular bacterial pathogens.

Assessment of the potential and application of Be12O12 nanocage for removal of ciprofloxacin from water employing density functional theory

The modern world is facing the issue of emerging pollutants for its sustainable development. We report a detailed study on the abatement of ciprofloxacin (CIP) by Be12O12 nanocage. Five different geometries of Be12O12 nanocage with CIP i.e., Com-A, Com-B, Com-C, Com-D and Com-E are optimized. All the complexes show chemisorption with the highest adsorption energies (Eads) of - 39.86 kcal/mol for Com-E followed by Com-A, Com-B, Com-C and Com-D without any structural change. The O and F atoms of ciprofloxacin (CIP) interacts strongly with the Be atoms of the nanocage respectively. Charge transfer from the nanocage to CIP reveals strong interaction in all the optimized complexes, with maximum charge transfer of -0.199 e for Com-E with the smallest bond lengths of 1.52 Å and 1.63 Å. The decrease in the bandgap of the optimized geometries witnesses increase in the sensing ability of the adsorbent and demonstrates strong interaction between the adsorbent and adsorbate supporting the adsorption energies. The positive values of Hb and ∇2ρb for all complexes reveals strong interaction of electrostatic nature between CIP and Be12O12 nature which is supported by different tools of DFT. The overall study suggests Be12O12 an efficient, reusable adsorbent for the purification of water from CIP and therefore Be12O12 can be used effectively to eliminate antibiotics from water.

Novel coumarin linked pyrazoles, thiazoles, and thiadiazoles: synthetic strategies and in vitro antimicrobial investigation

AIM

Emerging resistance among pathogens necessitates the development of novel antimicrobial agents. As a result, we aimed to synthesize new coumarins and study their antimicrobial activity with the hope of obtaining effective drugs.

METHOD

A series of coumarins were synthesized, characterized, and assessed for antimicrobial activity using broth microdilution and agar diffusion methods against Gram-positive (Bacillus pumilis, Streptococcus faecalis), Gram-negative (Escherichia coli, Enterobacter cloacae) bacteria, and fungi (Saccharomyces cerevisiae, Candida albicans).

RESULTS

Pyrazoles 15 and 16 revealed promising activities against all bacterial strains with MIC values ranging from 1.95 to 15.6 µg/ml. Notably, pyrazole 15 with CF3 in 3-position of pyrazole ring demonstrated higher ability to inhibit Streptococcus faecalis strain with MIC value equal to penicillin G (3.91 µg/ml). It also exhibited the best bactericidal potency against Escherichia coli with MBC value of 15.6 µg/ml while, pyrazole 16 recorded the same MBC value against Enterobacter cloacae. Pyrazole 15 demonstrated the strongest antifungal activity against both fungal strains with MIC and MFC values of 15.6, 7.81, 62.5, and 31.3 µg/ml against Saccharomyces cerevisiae and Candida albicans, respectively.

CONCLUSION

These findings underscore the potential of coumarins, particularly compounds 15 and 16, as effective antimicrobial agents and provide critical insights into the design of bioactive molecules.

6-aryloxy-2-aminopyrimidine-benzonitrile hybrids as anti-infective agents: Synthesis, bioevaluation, and molecular docking

This report explores the potential of novel 6-aryloxy-2-aminopyrimidine-benzonitrile scaffolds as promising anti-infective agents in the face of the increasing threat of infectious diseases. Starting from 2-amino-4,6-dichloropyrimidine, a series of 24 compounds inspired from the antiviral drugs dapivirine, etravirine, and rilpivirine were designed and synthesized via a two-step reaction sequence in good yields. Biological testing of synthetic analogs revealed potent inhibition against both viral and tuberculosis targets. Notably, compounds 5p (2,4-dimethyl substitution; IC50 = 44 ± 4.9 µM; selectivity index [SI] = 20) and 5 s (3-thiophenphenyl; IC50 = 6 ± 1 µM; SI = 120) showed significant antiviral activity against pandemic influenza virus A/Puerto Rico/8/34 (H1N1) with positive toxicity profiles and also exhibited good IC50 values (5p, IC50 = 10 ± 2 µM; SI = 9 and 5 s, IC50 = 16 ± 2 µM; SI = 60) against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (Wuhan strain) compared with favipiravir. In addition, analogs 5a, 5r, 5t, and 5u showed good antitubercular activity against Mycobacterium tuberculosis H37Rv strain and compounds 3, 5f, 5n, and 5q showed moderate antibacterial activity against gram+ve and gram-ve bacterial strains, suggesting that this scaffold has a broad spectrum of therapeutic effects.

Proteases, a powerful biochemical tool in the service of medicine, clinical and pharmaceutical

Proteases, enzymes that hydrolyze peptide bonds, have various applications in medicine, clinical applications, and pharmaceutical development. They are used in cancer treatment, wound debridement, contact lens cleaning, prion degradation, biofilm removal, and fibrinolytic agents. Proteases are also crucial in cardiovascular disease treatment, emphasizing the need for safe, affordable, and effective fibrinolytic drugs. Proteolytic enzymes and protease biosensors are increasingly used in diagnostic and therapeutic applications. Advanced technologies, such as nanomaterials-based sensors, are being developed to enhance the sensitivity, specificity, and versatility of protease biosensors. These biosensors are becoming effective tools for disease detection due to their precision and rapidity. They can detect extracellular and intracellular proteases, as well as fluorescence-based methods for real-time and label-free detection of virus-related proteases. The active utilization of proteolytic enzymatic biosensors is expected to expand significantly in biomedical research, in-vitro model systems, and drug development. We focused on journal articles and books published in English between 1982 and 2024 for this study.

Exploiting the fitness cost of metallo-β-lactamase expression can overcome antibiotic resistance in bacterial pathogens

Carbapenems are last-resort antibiotics for treating bacterial infections. The widespread acquisition of metallo-β-lactamases, such as VIM-2, contributes to the emergence of carbapenem-resistant pathogens, and currently, no metallo-β-lactamase inhibitors are available in the clinic. Here we show that bacteria expressing VIM-2 have impaired growth in zinc-deprived environments, including human serum and murine infection models. Using transcriptomic, genomic and chemical probes, we identified molecular pathways critical for VIM-2 expression under zinc limitation. In particular, disruption of envelope stress response pathways reduced the growth of VIM-2-expressing bacteria in vitro and in vivo. Furthermore, we showed that VIM-2 expression disrupts the integrity of the outer membrane, rendering VIM-2-expressing bacteria more susceptible to azithromycin. Using a systemic murine infection model, we showed azithromycin's therapeutic potential against VIM-2-expressing pathogens. In all, our findings provide a framework to exploit the fitness trade-offs of resistance, potentially accelerating the discovery of additional treatments for infections caused by multidrug-resistant bacteria.

AIE-based ruthenium complexes as photosensitizers for specifically photo-inactivate gram-positive bacteria

The emergence of multidrug-resistant bacterial have caused severe burden for public health. Particularly, Staphylococcus aureus as one of ESKAPE pathogens have induced various infectious diseases and resulted in increasing deaths. Developing new antibacterial agents is still urgent and challenging. Fortunately, in this study, based on aggregation-induced emission (AIE) ruthenium complexes were designed and synthesized, which realized the high efficiency of reactive oxygen species generation and remarkably killed S. aureus unlike conventional antibiotics action. Significantly, owing to good singlet oxygen production ability, Ru1 at only 4 μg/mL of concentration displayed good antibacterial photodynamic therapy effect upon white light irradiation and could deplete essential coenzyme NADH to disrupt intracellular redox balance. Also, the electrostatic interaction between Ru1 and bacteria enhanced the possibility of antibacterial. Under light irradiation, Ru1 could efficiently inhibit the biofilm growth and avoid the development of drug-resistant. Furthermore, Ru1 possessed excellent biocompatibility and displayed remarkable therapy effect in treating mice-wound infections in vivo. These findings indicated that AIE-based ruthenium complexes as new antibacterial agent had great potential in photodynamic therapy of bacteria and addressing the drug-resistance crisis.

Ultralow Dose Iron-Copper Bimetallic Single-Atom Nanozymes for Efficient Photothermal-Chemodynamic Antibacterial and Wound Healing

The combination of photothermal and chemodynamic therapy (PTT-CDT) using single-atom nanozymes (SAzymes) shows great promise in combating pathogenic and drug-resistant bacteria. However, the photothermal conversion efficiency and catalytic activity of SAzymes with solely metal sites remain inadequate, often requiring high doses for effectiveness. Herein, a bimetallic single-atomic nanozymes with Fe and Cu active sites (FeCu BSNs) designed is reported for efficient treatment of bacterial infections through hyperthermia-amplified nanozyme catalysis strategy. The FeCu BSNs demonstrate remarkable peroxidase (POD) activity with a specific activity (SA) of 752.25 U mg-1, which is 2.3 folds larger than that of Fe SAzymes (323.45 U mg-1). Additionally, their photothermal effect achieve a photothermal conversion efficiency up to 56.26%, which is two times higher that of Fe SAzymes (29.69%) and Cu SAzymes (25.55%). These enhancements can be attributed to the hybridization of Fe and Cu sites. The FeCu BSNs-mediated PTT-CDT combination therapy demonstrates potent antibacterial effects in both in vitro and in vivo models, attributed to high levels of reactive oxygen species (ROS) generation and hyperthermia. This study effectively validates the application of ultralow-dose bimetallic single-atom nanozymes in PTT-CDT for wound healing, offering a promising approach for enhanced wound recovery.

A Polypeptosome Spray To Heal Antibiotic-Resistant Bacteria-Infected Wound by Photocatalysis-Induced Metabolism-Interference

With the booming antimicrobial drug resistance worldwide, traditional antibacterial agents (e.g., antibiotics) are usually powerless against superbug. Targeting antibacterial pathways different from traditional antibiotics could be an effective approach to treating wounds with a resistant bacterial infection. In this work, an antibacterial polymersome was developed to physically induce bacterial membrane damage and interfere with bacterial metabolism. First, we synthesized an antibacterial poly(ε-caprolactone)-block-poly(glutamic acid)-block-poly(Lys-stat-Phe) copolymer, which was then self-assembled into polypeptosome with the amplification of surface positive charges to disrupt bacterial membranes. In addition, the polypeptosome was further decorated with photocatalytic bismuth sulfide (Bi2S3) nanoparticles as a photocatalyst to interfere with reduced nicotinamide adenine dinucleotide (NADH) conversion. Specifically, near-infrared light generated free electrons from Bi2S3 nanoparticles could effectively interfere with NADH homeostasis to induce antibiotic-resistant bacteria death, as verified by transcriptome sequence analysis. Moreover, effective healing of antibiotic-resistant bacteria-infected wounds of mice was achieved with a spray of polypeptosome dispersion. Overall, we provided a fresh strategy to integrate bacterial membrane damage and metabolism interference functions within antibacterial polymersomes for healing antibiotic-resistant bacteria-infected wound.

Evaluation of the alkyl chain length and photocatalytic antibacterial performance of cation g-C3N4

Several cation graphite carbon nitrides (g-C3N4-(CH2)n-ImI+) were synthesized by chemically attaching imidazolium appended alkane chains with different lengths (n = 2, 4, 8, 12 and 16) to g-C3N4. The introduction of a cation segment potentially improved the interaction between the carbon material and Gram negative (MDR-A. baumannii) and Gram positive (S. aureus) bacteria as characterized by ζ potential measurement. Short alkane chain (carbon numbers of 2, 4 and 8) carbon materials displayed relatively stronger bacterial interactions compared to long alkane chain bearing ones (n = 12 and 16). In addition, short chain carbon materials (g-C3N4-(CH2)4-ImI+) displayed relatively higher photocatalytic reactive oxygen species (1O2, ˙O2- and ˙OH) production efficiency. Bacterial interaction and ROS production efficiency synergistically contribute to photocatalytic antibacterial performance. The current data revealed that g-C3N4 with short flexible cations attached exhibited bacterial interaction and ROS production. Among these synthesized materials, g-C3N4-(CH2)4-ImI+ exhibited the most pronounced photocatalytic antibacterial efficiency (>99%).

Phenotypic-Based Discovery and Exploration of a Resorufin Scaffold with Activity against Mycobacterium tuberculosis

Tuberculosis remains a leading cause of death by infectious disease. The long treatment regimen and the spread of drug-resistant strains of the causative agent Mycobacterium tuberculosis (Mtb) necessitates the development of new treatment options. In a phenotypic screen, nitrofuran-resorufin conjugate 1 was identified as a potent sub-micromolar inhibitor of whole cell Mtb. Complete loss of activity was observed for this compound in Mtb mutants affected in enzyme cofactor F420 biosynthesis (fbiC), suggesting that 1 undergoes prodrug activation in a manner similar to anti-tuberculosis prodrug pretomanid. Exploration of the structure-activity relationship led to the discovery of novel resorufin analogues that do not rely on the deazaflavin-dependent nitroreductase (Ddn) bioactivation pathway for their antimycobacterial activity. These analogues are of interest as they work through an alternative, currently unknown mechanism that may expand our chemical arsenal towards the treatment of this devastating disease.

Unleashing nature's defense: potent antimicrobial power of plant extracts against oral pathogens and Streptococcus mutans biofilms

Objectives

The increasing demand for alternatives to antibiotics against resistant bacteria has led to research on natural products. The aim of this study was to analyze the antimicrobial and antibiofilm activity of 16 Mediterranean herb extracts.

Materials and methods

The extracts were analyzed using High Performance Thin Layer Chromatography. The minimum inhibitory concentration and minimum bactericidal concentration of the extracts from Achillea taygetea, Cistus creticus ssp. creticus, Cistus monspeliensis, Lavandula stoechas, Mentha aquatica, Mentha longifolia, Origanum vulgare, Phlomis cretica, Rosmarinus officinalis, Salvia sclarea, Satureja parnassica, Satureja thymbra, Sideritis euboea, Sideritis syriaca, Stachys spinosa, and Thymus longicaulis were determined against eight oral bacteria and fungus Candida albicans. Microtiter plate test was conducted to evaluate the antibiofilm activity against Streptococcus mutans.

Results

Overall, all tested extracts efficiently suppressed the growth of obligate anaerobic bacteria. When applied at concentrations ≥0.15 mg/ml, the extracts exhibited moderate to high antibiofilm activity comparable to that of chlorhexidine (CHX) against S. mutans. Interestingly, R. officinalis (MIC: 0.01-0.06 mg/ml) and O. vulgare (MIC: 0.04-1.25 mg/ml) demonstrated the highest antibacterial activity against oral bacteria. Additionally, R. officinalis and L. stoechas significantly inhibited S. mutans biofilm formation at 0.15 mg/ml.

Conclusions

The tested plant extracts can be considered as alternative natural antimicrobial and antibiofilm agents.

Clinical relevance

Mediterranean herb extracts show promise as natural alternatives to combat oral bacteria and biofilm formation, offering potential new therapies for infectious oral diseases in the context of antibiotic resistance.

An Asymmetric Bacterial Cellulose Membrane Incorporating CuPt Nanozymes and Curcumin for Accelerating Wound Healing

Damaged skin compromises its ability to effectively prevent the invasion of harmful bacteria into the tissue, leading to bacterial infection of the wound and hindering the healing process. To address this challenge, we have developed a multifunctional asymmetric wound dressing (CuPt-Cur-ABC) that effectively addresses the lack of bactericidal activity and the release of active ingredients in conventional bacterial cellulose (BC), which can be employed to create a barrier of defense between the wound and its surrounding environment. Compared with BC, asymmetric bacterial cellulose (ABC) used starch as a pore-causing agent, forming holes of different sizes at the top and bottom, which enhanced the ability of ABC to load and moderate-release drugs. First, as-synthesized CuPt nanozymes with an octopod nanoframe structure had multiple enzymatic activities including peroxidase-like, catalase-like, and glutathione peroxidase-like activities. Then, CuPt and curcumin (Cur) were loaded into ABC under ultrasound. Under 808 nm laser irradiation, the nanocomposites possessed good photothermal properties. So the photothermal therapy combined with chemodynamic therapy and inherent antibacterial performance of Cur achieved 99.3% and 99.6% in vitro bactericidal efficacy against Staphylococcus aureus and Escherichia coli, respectively. Moderate release of Cur can clear the excess reactive oxygen species and promote the polarization of macrophages toward the M2 type. In vivo experiments additionally confirmed that the constructed wound dressing achieved multiple functions, including effective antibacterial activity, reversing the inflammatory microenvironment, and promoting wound healing.

A novel cathelicidin TS-CATH derived from Thamnophis sirtalis combats drug-resistant gram-negative bacteria in vitro and in vivo

Antimicrobial peptides are promising therapeutic agents for treating drug-resistant bacterial disease due to their broad-spectrum antimicrobial activity and decreased susceptibility to evolutionary resistance. In this study, three novel cathelicidin antimicrobial peptides were identified from Thamnophis sirtalis, Balaenoptera musculus, and Lipotes vexillifer by protein database mining and sequence alignment and were subsequently named TS-CATH, BM-CATH, and LV-CATH, respectively. All three peptides exhibited satisfactory antibacterial activity and broad antibacterial spectra against clinically isolated E. coli, P. aeruginosa, K. pneumoniae, and A. baumannii in vitro. Among them, TS-CATH displayed the best antimicrobial/bactericidal activity, with a rapid elimination efficiency against the tested drug-resistant gram-negative bacteria within 20 min, and exhibited the lowest cytotoxicity toward mammalian cells. Furthermore, TS-CATH effectively enhanced the survival rate of mice with ceftazidime-resistant E. coli bacteremia and promoted wound healing in meropenem-resistant P. aeruginosa infection. These results were achieved through the eradication of bacterial growth in target organs and wounds, further inhibiting the systemic dissemination of bacteria and the inflammatory response. TS-CATH exhibited direct antimicrobial activity by damaging the inner and outer membranes, resulting in leakage of the bacterial contents at super-MICs. Moreover, TS-CATH disrupted the bacterial respiratory chain, which inhibited ATP synthesis and induced ROS formation, significantly contributing to its antibacterial efficacy at sub-MICs. Overall, TS-CATH has potential for use as an antibacterial agent.

Chemical strategies for antisense antibiotics

Antibacterial resistance is a severe threat to modern medicine and human health. To stay ahead of constantly-evolving bacteria we need to expand our arsenal of effective antibiotics. As such, antisense therapy is an attractive approach. The programmability allows to in principle target any RNA sequence within bacteria, enabling tremendous selectivity. In this Tutorial Review we provide guidelines for devising effective antibacterial antisense agents and offer a concise perspective for future research. We will review the chemical architectures of antibacterial antisense agents with a special focus on the delivery and target selection for successful antisense design. This Tutorial Review will strive to serve as an essential guide for antibacterial antisense technology development.

Antibacterial, Antibiofilm, and Anti-inflammatory Effects of a Novel Thrombin-Derived Peptide in Sepsis Models: Insights into Underlying Mechanisms

We developed two short helical antimicrobial peptides, HVF18-a3 and its d-enantiomer, HVF18-a3-d, derived from the thrombin C-terminal peptide HVF18. These peptides exhibit potent antimicrobial activity against various bacteria by compromising both the outer and inner membranes, with low hemolytic activity. They are stable in the presence of physiological salts and human serum, exhibiting a low potential for developing drug resistance and excellent antibiofilm activity against Gram-negative bacteria. HVF18-a3-d also neutralized lipopolysaccharide (LPS) through direct binding interactions and suppressed the production of inflammatory cytokines through the inflammatory signaling pathway mediated by Toll-like receptor 4 in RAW264.7 cells stimulated with LPS. Both pre- and post-treatment with HVF18-a3-d significantly protected mice against fatal septic shock induced by carbapenem resistant Acinetobacter baumannii. These findings suggest HVF18-a3 and HVF18-a3-d are promising candidates for developing antibiotics against Gram-negative sepsis.

Rapidly in situ forming antibiotic-free injectable hydrogel wound dressing for eradicating drug-resistant bacterial infections in human skin organoids

The rising prevalence of global antibiotic resistance evokes the urgent requirement to explore the alternative antimicrobial candidates. It is of great significance to overcome these serious threats of multidrug-resistant bacterial infections and difficult-to-heal cutaneous wounds to human health. Herein, we proposed a rapidly in situ forming innovative antibiotic-free hydrogel dressing with excellent biocompatibility, easy injectability, strong tissue adhesion and superior antibacterial activity against drug-resistant bacteria. An octa-armed poly(ethylene glycol) amine (Octa-PEG-NH2) was quickly crosslinked with a green industrial microbicide tetrakis (hydroxymethyl) phosphonium chloride (THPC) to form an antibacterial hydrogel (OPTH) by simple mixing without any other initiators or crosslinkers. A significant broad-spectrum antibacterial efficacy was demonstrated against Gram-positive Staphylococcus aureus (S. aureus), Gram-negative Escherichia coli (E. coli) and methicillin-resistant Staphylococcus aureus (MRSA). Significantly, benefiting from its flexible injectability and reliable tissue adhesion, the excellent antibacterial performances were further evidenced by employing human-induced pluripotent stem cell (iPSC)-derived skin organoids in a 3D culture system and rat animal wound models in vivo with MRSA infection, thus allowing for reepithelization promotion and wound healing. Collectively, the findings not only propose a facile gelatinization strategy for readily accessible antibiotic-free hydrogel dressings for effective MRSA therapy but also hold great clinical translation potential in obliterating multi-pathogenic bacteria and accelerating wound healing.

Injectable Photocrosslinked Hydrogel Dressing Encapsulating Quercetin-Loaded Zeolitic Imidazolate Framework-8 for Skin Wound Healing

Background: Wound management is a critical component of clinical practice. Promoting timely healing of wounds is essential for patient recovery. Traditional treatments have limited efficacy due to prolonged healing times, excessive inflammatory responses, and susceptibility to infection. Methods: In this research, we created an injectable hydrogel wound dressing formulated from gelatin methacryloyl (GelMA) that encapsulates quercetin-loaded zeolitic imidazolate framework-8 (Qu@ZIF-8) nanoparticles. Next, its ability to promote skin wound healing was validated through in vitro experiments and animal studies. Results: Research conducted both in vitro and in vivo indicated that this hydrogel dressing effectively mitigates inflammation, inhibits bacterial growth, and promotes angiogenesis and collagen synthesis, thus facilitating a safe and efficient healing process for wounds. Conclusions: This cutting-edge scaffold system provides a novel strategy for wound repair and demonstrates significant potential for clinical applications.

High-Throughput Discovery of Synthetic Siderophores for Trojan Horse Antibiotics

To cause infection, bacterial pathogens must overcome host immune factors and barriers to nutrient acquisition. Reproducing these aspects of host physiology in vitro has shown great promise for antibacterial drug discovery. When used as a bacterial growth medium, human serum replicates several aspects of the host environment, including innate immunity and iron limitation. We previously reported that a high-throughput chemical screen using serum as the growth medium enabled the discovery of novel growth inhibitors overlooked by conventional screens. Here, we report that a subset of compounds from this high-throughput serum screen display an unexpected growth enhancing phenotype and are enriched for synthetic siderophores. We selected 35 compounds of diverse chemical structure and quantified their ability to enhance bacterial growth in human serum. We show that many of these compounds chelate iron, suggesting they were acting as siderophores and providing iron to the bacteria. For two different pharmacophores represented among these synthetic siderophores, conjugation to the β-lactam antibiotic ampicillin imparted iron-dependent enhancement in antibacterial activity. Conjugation of the most potent growth-enhancing synthetic siderophore with the monobactam aztreonam produced MLEB-22043, a broad-spectrum antibiotic with significantly improved activity against Klebsiella pneumoniae, Escherichia coli, Acinetobacter baumannii, and Pseudomonas aeruginosa. This synthetic siderophore-monobactam conjugate uses multiple TonB-dependent transporters for uptake into P. aeruginosa. Like aztreonam, MLEB-22043 demonstrated activity against metallo-β-lactamase expressing bacteria, and, when combined with the β-lactamase inhibitor avibactam, was active against clinical strains coexpressing the NDM-1 metallo-β-lactamase and serine β-lactamases. Our work shows that human serum is an effective bacterial growth medium for the high-throughput discovery of synthetic siderophores, enabling the development of novel Trojan Horse antibiotics.