Search Results (302)

Background/Objectives: Neisseria gonorrhoeae is a high-priority pathogen for the development of new therapeutic alternatives. Efflux pumps are attractive drug targets because their inactivation influences N. gonorrhoeae susceptibility to multiple antimicrobials. Since most gonococcal efflux systems are energy-dependent, interference with energy metabolism and membrane transport may indirectly compromise efflux activity. Efflux inhibitors may increase intracellular antibiotic concentration, although this requires validation in resistant strains. The most effective efflux inhibitors interfere with energy metabolism, affecting several physiological processes, including efflux. In this work, we used an in silico drug repurposing strategy targeting proteins involved in membrane transport and energy metabolism in N. gonorrhoeae. A subset of candidate drugs were subsequently evaluated in vitro using only the reference strain N. gonorrhoeae ATCC 49226. Methods: Predicted drug–target interactions were identified using publicly available databases such as DrugBank and STITCH. Minimum inhibitory concentrations (MICs) of selected drugs against N. gonorrhoeae were determined by microdilution. Changes in intracellular ethidium bromide accumulation were assessed by real-time fluorometry as an indirect indicator of possible efflux-related interference. Results: In silico analysis identified 32 predicted targets associated with 57 approved drugs. Triclabendazole and dequalinium showed the lowest MIC values of the tested compounds (2 and 4 mg/L, respectively). Ketotifen and verapamil demonstrated activity consistent with possible efflux interference, as indicated by increased ethidium bromide accumulation. Atovaquone showed adjuvant-like effects in combination assays, suggesting that mechanisms other than efflux-related interference may contribute to its activity. Conclusions: Overall, this preliminary study identifies approved drugs with antimicrobial or adjuvant activity against a single N. gonorrhoeae reference strain, supporting further investigation in clinically relevant and efflux-variant strains. Full article

It is crucial to consider newer antibiotics with activity against anaerobes and Helicobacter pylori, given their healthcare importance, and the constantly growing antibiotic resistance/multidrug resistance, which complicates the therapy. The aim of this review was to emphasize certain recently approved or still-under-investigation antibiotics with potential benefits for treating Clostridioides difficile infections (CDIs), other anaerobic infections, and those caused by H. pylori, covering recent data from articles published primarily in 2020–2026. Given the limited number of antibiotics for treating CDI and fidaxomicin nonavailability in many countries, it is necessary to conduct more extensive laboratory and clinical studies of promising antibiotics such as ibezapolstat, delafloxacin, lascufloxacin, omadacycline, eravacycline, ridinilazole, and CRS3123. Against Bacteroides fragilis group species, delafloxacin and eravacycline showed good activity. Research on rifasutenizol for bacterial vaginosis, sarecycline and nadifloxacin for acne vulgaris and amixicile for periodontal diseases needs to be expanded. For H. pylori infection, delafloxacin, sitafloxacin, nemonoxacin, zoliflodacin, and rifasutenizol may improve the suboptimal success of most eradication regimens. However, more efforts, in coordination between medical, scientific, manufacturing, and government representatives, should ensure wider access to and research on the newer antibacterials. Establishing more research groups, careful examination of market issues, and additional approaches, such as nanomaterials, efflux pump inhibitors, phage therapy, and CRISPR-Cas systems, should be beneficial. Notwithstanding the difficulties, there are many opportunities to promote research on and potential use of newer antibiotics which show advantages over the older antibacterials, and to make them available to numerous countries and patients worldwide. Full article

Antimicrobial resistance (AMR) is a leading global cause of death, with recent World Health Organization (WHO) data revealing that one in six laboratory-confirmed bacterial infections shows resistance to at least one antibiotic treatment. This review comprehensively analyzes the AMR landscape in 2026, detailing its evolution, mechanisms, and the innovative strategies being deployed to combat it. Driven by Darwinian selection and accelerated by factors like antibiotic overuse during the Coronavirus Disease 2019 (COVID-19) pandemic (predominantly in hospitalized patients with suspected bacterial co-infection), AMR is propelled by a diverse molecular arsenal in bacteria. Key mechanisms include enzymatic drug inactivation (e.g., the diversifying β-lactamase superfamily), target site modification (e.g., mcr genes conferring colistin resistance), efflux pumps, and biofilm formation. The rapid global spread of these traits is facilitated by a dynamic “mobilome”, a network of plasmids and transposons that shuttle resistance genes between species. This crisis has sparked a major scientific mobilization. Advances include the discovery of novel antibiotic scaffolds like lariocidin and the regulatory approval of critical new antibiotic/inhibitor combinations such as sulbactam/durlobactam and aztreonam/avibactam, which target highly resistant Gram-negative bacteria. Moreover, the first-in-class antibiotic gepotidacin offers a new option for urinary tract infections. Beyond traditional drugs, the pipeline is diversifying to include phage therapy, antivirulence strategies, and artificial intelligence-guided drug discovery. This diversification is critical as it helps preserve the effectiveness of existing Medically Important Antimicrobials (MIAs), those deemed essential for human medicine, by providing alternative or adjunctive treatment options. However, scientific innovation alone is insufficient. This review argues that lasting success requires parallel progress in global policy and infrastructure. Strategic priorities beyond 2026 must include finalizing and funding updated global action plans, strengthening real-time surveillance and diagnostic capacity, especially in low-resource settings, and implementing new economic models to de-risk antibiotic development. Embedding effective antimicrobial stewardship within universal health coverage and pandemic preparedness plans is crucial. Ultimately, defeating AMR demands an unprecedented, coordinated global effort that outpaces the relentless adaptability of bacterial pathogens. Full article

Antimicrobial resistance (AMR) is a critical global public health crisis that is being exacerbated by widespread misuse of antibiotics and rapid bacterial adaptation. The progressive decrease in antibiotic efficacy is also compounded by a stagnating drug-discovery pipeline and underscores the urgent need for innovative and sustainable antimicrobial strategies. This review systematically delineates the core molecular mechanisms driving bacterial resistance, including enzymatic drug inactivation, target modification, reduced membrane permeability, and multidrug efflux pump overexpression. Furthermore, the potential of (flavonoids, alkaloids, and phenolics) as structurally diverse plant-derived compounds with multi-target activity is comprehensively assessed. The features of multi-target activity make them promising dual-function agents that may be capable of both direct antimicrobial action and resistance modulation. These natural products have distinct mechanisms from conventional antibiotics, low propensity for resistance, and versatile bioactivity as biofilm disruptors, enzyme inhibitors, and efflux pump blockers. Numerous phytochemicals exhibit potent synergistic effects with available antibiotics by effectively resensitizing resistant pathogens and extending the clinical utility of current antimicrobials. By integrating mechanistic understanding with translational potential, this review discusses phytochemicals as a sustainable resource for developing next-generation antimicrobial strategies as a complementary approach to revitalize therapeutic pipelines and combat multidrug-resistant infections. Full article

Auranofin (AF), an FDA-approved drug for rheumatoid arthritis, exhibits strong antibacterial activity against Gram-positive bacteria, while Gram-negative species remain largely tolerant. This study assessed the antimicrobial activity of AF and three analogues against clinically relevant Gram-negative pathogens and explored tolerance mechanisms in Pseudomonas aeruginosa. Broth microdilution assays were performed on reference strains and clinical isolates of Escherichia coli, Klebsiella pneumoniae, and P. aeruginosa. Synergy studies with the most active analogue, PEt₃AuCl (AF-Cl), were conducted against P. aeruginosa using polymyxin B (PMB), two efflux-pump inhibitors, and two glutathione (GSH) depletors. Gold compounds showed MICs between 4 and >64 µg/mL, with AF-Cl displaying the highest activity. AF-Cl activity was markedly enhanced by PMB and efflux-pump inhibitors, indicating that outer membrane permeability and efflux contribute to tolerance. Additionally, GSH depletion significantly potentiated AF-Cl, implicating redox homeostasis in resistance. Overall, AF-Cl shows potential against Gram-negative bacteria when combined with agents targeting membrane integrity, efflux systems, or redox balance, supporting combinatorial strategies to overcome resistance in P. aeruginosa and related pathogens. Full article

The global spread of multidrug-resistant (MDR) Gram-negative pathogens has significantly narrowed therapeutic options for serious infections. MDR organisms frequently harbor multiple resistance mechanisms, such as β-lactamases and non-β-lactam determinants, which limit the activity of many β-lactam/β-lactamase inhibitor combinations and complicate the clinical utility of newer agents such as cefiderocol and aztreonam–avibactam. These challenges highlight the need for mechanistically distinct, non-β-lactam therapies capable of maintaining activity in MDR settings. Eravacycline is a fully synthetic fluorocycline antibiotic that inhibits bacterial protein synthesis through high-affinity binding to the 30S ribosomal subunit, a mechanism unaffected by β-lactamase-mediated resistance. Structural modifications at key positions confer stability against common tetracycline resistance mechanisms, including efflux pumps and ribosomal protection proteins. In vitro surveillance studies consistently demonstrate potent activity against a broad range of MDR Gram-negative pathogens, notably carbapenem-resistant Enterobacterales and isolates harboring metallo-β-lactamases. The clinical efficacy and safety of eravacycline have been established in pivotal Phase 3 trials for complicated intra-abdominal infections. Although highly resistant phenotypes were underrepresented in these trials, emerging real-world data describe off-label use in MDR Gram-negative infections, often as salvage or step-down therapy. These experiences suggest acceptable clinical outcomes and favorable tolerability in complex, high-risk patients. This review synthesizes mechanistic, microbiologic, pharmacologic, and clinical evidence supporting eravacycline’s potential role in the management of MDR Gram-negative infections. Full article

The increasing prevalence of infections caused by multidrug-resistant (MDR) Gram-negative bacteria represents a major global public health challenge. Among hospital-acquired infections (HAIs), ventilator-associated pneumonia (VAP) caused by non-fermenting Gram-negative pathogens, particularly the Acinetobacter baumannii-calcoaceticus complex, it is associated with limited therapeutic options and high mortality. Sulbactam–durlobactam is a novel combination consisting of sulbactam, a β-lactamase inhibitor with intrinsic activity against Acinetobacter spp., and durlobactam, a diazabicyclooctane β-lactamase inhibitor targeting Ambler class A, C, and D enzymes. This review summarizes current evidence on the pharmacological properties, clinical efficacy, and resistance mechanisms associated with this combination. Clinical trials have demonstrated that sulbactam–durlobactam is non-inferior to colistin in the treatment of infections caused by carbapenem-resistant A. baumannii, with a significantly lower risk of nephrotoxicity. The combination is generally well tolerated and represents a promising therapeutic option for difficult-to-treat infections. However, emerging resistance mechanisms, including PBP3 mutations, metallo-β-lactamase production, and efflux pump overexpression, may limit its long-term effectiveness. Further research is required to better understand resistance development and optimize clinical use. Full article

Background/Objectives: Microbial resistance to antibiotics has become a major global public health problem, threatening the effectiveness of current therapeutic strategies. The present study seeks to investigate natural compounds originating from fungal sources for their ability to interfere with efflux pump-mediated resistance in multidrug-resistant (MDR) bacteria, with the overarching goal of uncovering new candidates for antimicrobial therapeutic development. A chemical investigation of the ethanol extract of Termitomyces clypeatus was carried out to isolate and identify its constituents. Methods: Structural elucidation of the isolated metabolites was achieved through 1D and 2D NMR spectroscopy supported by mass spectrometric data. The crude extract and the purified compounds were then evaluated for their antibacterial activities individually, in the presence of an efflux pump inhibitor, and in combination with three antibiotics, using standardized microdilution assays. Results: Chromatographic separation of the extract yielded eleven known compounds, including three sphingolipids: (9Z,12Z)-N-(1,3,4-trihydroxyoctadecan-2-yl)octadeca-9,12-dienamide (1), 2-hydroxy-N-(1,3,4-trihydroxyoctadecan-2-yl)hexadecanamide (2), and cerebroside B (3); four steroids: ergosterol (4), cerevisterol (5), ergosterol peroxide (6), and 5α,6α-epoxy-(22E,24R)-ergosta-8(14),22-diene-3β,7α-diol (7); one alkaloid: piperine (8); one carbohydrate: D-mannitol (9); and two phthalates: dimethyl phthalate (10) and bis(2-ethylhexyl) terephthalate (11). GC–MS analysis led to the identification of eight fatty acid derivatives (12–19). Sub-fraction A, along with compounds 3, 4, and 8, exhibited moderate antibacterial activity against some tested strains, with MIC values of 64 μg/mL. These compounds were identified as substrates of bacterial efflux pumps, and their presence enhanced the antibacterial effects of ciprofloxacin, doxycycline, and amikacin. Conclusions: The findings of the present work indicate that Termitomyces clypeatus contains compounds with potential therapeutic value, as adjuvants that enhance the activity of conventional antibiotics. Full article

Multidrug (MDR) resistances against various classes of antibiotics used in S. aureus and MRSA infections have emerged. With limited options for novel antibacterial compounds, there is a strong focus on finding agents against MDR phenomenon, namely causative efflux pumps. We synthesised novel benzo-annelated 1,4-dihydropyridines with various substitution patterns both at the 4- and N-alkyl substituents and, additionally, at the annelated aromatic residues. MDR efflux pump-inhibiting activity was evaluated in S. aureus strains including MRSA and was measured in a fluorescent assay system using ethidium bromide as the overall substrate of S. aureus efflux pumps. Favourable substituents for inhibiting efflux pump activity in S. aureus have been 4-methoxy and 4- and 3-chloro at the 4-phenyl position of the 1,4-dihydropyridine ring combined with an N-benzyl residue. The most favourable substituents for the activity inMRSA strains have been those 4-phenyl chloro substituents combined with additional pyrido residues attached to the benzo substituent at the 1,4-dihydropyridine core. Benzo-annelated 1,4-dihydropyridines are a novel class of inhibitors of MDR relevant efflux pumps in S. aureus strains including MRSA. Full article

Background/Objectives: Multidrug resistance (MDR) remains a major pathophysiological barrier to effective chemotherapy based on anthracyclines, including daunorubicin (DNR), in the treatment of leukemia. However, conventional population-level measurements of drug uptake do not resolve variability in uptake kinetics among individual leukemia cells, which may influence intracellular drug accumulation and therapeutic response. Methods: In this study, real-time DNR uptake was quantified at the single-cell level using a microfluidic biochip that enabled long-term cellular retention and continuous monitoring. Both wild-type drug-sensitive leukemia cells and a multidrug-resistant mutant overexpressing the P-glycoprotein (P-gp) efflux pump were examined. Results: Kinetic analysis revealed that DNR uptake in drug-sensitive cells was well described by a single dominant uptake process, whereas uptake in MDR cells required a model incorporating two kinetically distinct processes. In both cell populations, pronounced cell-to-cell variation was observed in uptake rates and intracellular drug retention, indicating substantial functional heterogeneity within phenotypically similar cells. This variability persisted following the treatment with an MDR inhibitor and obscured the differences between inhibitor-treated and untreated cells when the uptake was compared across different single cells. To overcome this limitation, a same-single-cell analysis (SASCA) approach was employed, enabling direct comparison of DNR uptake in the same individual cell before and after inhibitor exposure, thereby revealing enhanced intracellular DNR retention and accelerated uptake kinetics following inhibition. Conclusions: Together, these results demonstrate that real-time single-cell kinetic analysis reveals functionally relevant heterogeneity in multidrug-resistant leukemia cells and provides insight into the pathophysiology of MDR that cannot be obtained from population-averaged measurements. Full article

Bacterial biofilms are structured microbial communities enclosed within a self-produced extracellular polymeric substance matrix composed of polysaccharides, proteins, extracellular DNA, and lipids. This matrix promotes adhesion, structural stability, and the development of heterogeneous microenvironments that restrict antimicrobial penetration and shield bacteria from host immune responses. As a result, biofilms are major contributors to chronic, recurrent, device-related, and difficult-to-treat infections, posing a major challenge for clinical management and antimicrobial stewardship. This review summarizes current understandings of biofilm biology, its clinical relevance, including the stages of biofilm development, the composition and protective roles of the matrix, and the physiological heterogeneity that arises during maturation. It also examines key mechanisms underlying biofilm tolerance and resistance, such as limited antibiotic diffusion, and sequestration, enzymatic inactivation, efflux pump upregulation, persister cell formation, and horizontal gene transfer. In addition, it highlights important clinical settings in which biofilms are implicated, including cystic fibrosis, chronic wounds, osteomyelitis, implant- or device-associated infections, and breast implant illness, in which persistent implant-associated biofilms and the resulting chronic inflammatory milieu have been hypothesized to contribute to local and systemic manifestations in a subset of patients. The review further discusses conventional and emerging approaches for biofilm detection alongwith real-time monitoring. Biofilm-associated infections remain difficult to eradicate because persistence is driven by multiple interconnected protective mechanisms. Effective management therefore requires integrated strategies that combine accurate detection with multifaceted therapies, including antibiotics alongside matrix-disrupting enzymes, quorum-sensing inhibitors, bacteriophages, metabolic reactivators, and nanotechnology-based delivery systems. Advances in multi-omics and system-level modeling will be essential for developing next-generation strategies to prevent, monitor, and treat biofilm-associated disease. Full article

Objectives: Multidrug-resistant (MDR) Pseudomonas aeruginosa represents a major clinical challenge, driven in part by resistance–nodulation–division (RND) efflux pumps that reduce intracellular antibiotic concentrations and limit the efficacy of many antibacterial agents, including fluoroquinolones. The aim of this study was to identify and characterize TXA11114 as a small-molecule efflux pump inhibitor (EPI) capable of restoring the activity of the fluoroquinolone levofloxacin against MDR P. aeruginosa. Methods: The antibacterial activity of the TXA11114–levofloxacin combination was evaluated using minimum inhibitory concentration (MIC) assays against panels of clinical isolates. Mechanistic studies included levofloxacin accumulation assays, ethidium bromide accumulation assays, outer-membrane permeability measurements, and whole-genome sequencing of mutants with altered potentiation phenotypes. In vivo efficacy was evaluated in murine thigh and lung infection models, while preliminary safety and drug-like properties were assessed using cytotoxicity assays and in vitro ADME profiling. Results: The TXA11114–levofloxacin combination produced > 1 log₁₀ CFU reductions in bacterial burden in murine thigh and lung infection models, exceeding the activity of levofloxacin monotherapy. TXA11114 markedly potentiated levofloxacin activity, producing substantial reductions in levofloxacin MIC values across multiple MDR clinical isolates, and also enhanced the activity of several additional efflux pump substrates, including β-lactams, tetracyclines, chloramphenicol, and trimethoprim–sulfamethoxazole. Mechanistic experiments demonstrated increased intracellular accumulation of efflux substrates without evidence of nonspecific membrane disruption, and mutations in ompH were associated with altered potentiation phenotypes. Conclusions: The TXA11114–levofloxacin combination produced significantly greater bacterial reductions than levofloxacin monotherapy in murine infection models. Levofloxacin was selected because fluoroquinolone resistance in P. aeruginosa is frequently driven by efflux-mediated mechanisms. While this study focused on levofloxacin potentiation, future work will evaluate additional efflux pump substrates and further define the molecular target of TXA11114. Full article

Antimicrobial resistance (AMR) is one of the most pressing global public health challenges, compromising the effectiveness of standard antibiotic therapies and increasing morbidity, mortality, and healthcare costs. The scarcity of new antibiotics has driven research into alternative strategies to restore or enhance the effectiveness of existing drugs. Natural compounds, including polyphenols, alkaloids, terpenes and terpenoids, antimicrobial peptides, and microbial secondary metabolites, exhibit multitarget activities such as membrane disruption, efflux pump inhibition, biofilm suppression, and quorum sensing interference. In parallel, synthetic and semi-synthetic small-molecule inhibitors have been rationally designed to target specific resistance determinants, including β-lactamases, efflux systems, quorum sensing pathways, and stress-induced mutagenesis mechanisms such as the SOS response and DNA repair processes. These agents act as adjuvants, restoring susceptibility or reducing bacterial virulence without exerting strong selective pressure. The integration of natural bioactive compounds and targeted small-molecule inhibitors represents a promising complementary strategy for conventional antibiotics. Further pharmacological and clinical investigations are required to translate these approaches into effective tools within antimicrobial stewardship programs and broader public health strategies aimed at mitigating the global burden of AMR. This narrative review analyses the recent literature on natural compounds and synthetic or semi-synthetic small-molecule inhibitors with documented activity against antimicrobial resistance mechanisms. Full article

The berberine derivative 13-(2-methylbenzyl)-berberine (BED) has been shown to inhibit the MexXY-OprM efflux system of Pseudomonas aeruginosa (PA), a key contributor to aminoglycoside resistance, by interacting with the inner membrane protein MexY at an allosteric pocket (ALP). To enhance binding efficacy, this study aims to identify novel chemical scaffolds that target the MexY allosteric pocket through an integrated computational strategy. In this work, a ligand-based virtual screening (LBVS) approach was employed using a 2D/3D pharmacophore model derived from BED to perform in silico screening of an Enamine compound library, which encompasses a broad and diverse chemical space. A key objective was to compare the predictive performance of this pharmacophore-based workflow with a structure-based (SB) strategy incorporating molecular docking and molecular dynamics (MD) simulations. Notably, the top-ranked LBVS hits were consistently validated by docking and MD analyses, showing stable binding and interaction patterns comparable or superior to those of BED. This convergence between ligand-based (LB) and SB methods highlights the internal coherence of the workflow and supports the robustness of the pharmacophore hypothesis. The identified scaffolds generally displayed high hydrophobicity, consistent with the physicochemical nature of the binding site, but resulting in limited aqueous solubility and complicating their experimental evaluation. While these features confirm the importance of hydrophobic interactions in MexY recognition, with a particular focus on some few residues, such as Phe560, it also underscores the need for formulation strategies or rational scaffold modifications introducing moderate polarity without weakening key contacts. Overall, the integrated computational strategy not only yields promising lead chemical structures but also provides a solid basis for their future optimization, ultimately supporting the design of new efflux pump inhibitors (EPIs) capable of contributing to improved antibiotic susceptibility in multidrug-resistant PA strains. Full article

Background/Objectives: Hydrazones are organic compounds with the general structure R₂C=NNHR₁, distinguished by their versatility and modifiability, and are widely used in various applications due to their physicochemical and biological properties. They exhibit anticancer, anti-inflammatory, antibiofilm, and antibacterial activities. Antibiotic-resistant bacteria pose a serious public health threat, employing mechanisms such as enzymatic inactivation and efflux pumps. This study evaluated the antibacterial activity of the hydrazone HDZH1,4BENZ, a hydralazine-derived compound, as well as its potential adjuvant effect in combination with antibiotics against Staphylococcus aureus strains expressing efflux pumps. Methods: The strains used were 1199B (NorA efflux pump-expressing) and K2068 (MepA efflux pump-expressing). All assays were conducted using the broth microdilution method in Brain Heart Infusion (BHI) medium. Initially, the intrinsic antibacterial activity of the compound was determined. Subsequently, modulation assays were performed to evaluate its potential effect on efflux pump activity, with a standard efflux pump inhibitor included as a positive control. Results: Although HDZH1,4BENZ did not demonstrate significant direct antibacterial activity, the results indicate that this hydrazone exerts a notable inhibitory effect on the NorA (Norfloxacin resistance efflux pump A) and MepA (Multidrug efflux protein A) efflux pumps in S. aureus, thereby enhancing the efficacy of antibacterial agents. Conclusions: The activity of the hydrazone was comparable to that of chlorpromazine, suggesting that it may represent a promising alternative in the fight against antibiotic-resistant bacterial infections. Full article