Search Results (260)

Nosocomial infections caused by ESKAPE pathogens represent a significant burden to global health. These pathogens may exhibit multidrug resistance (MDR) mechanisms, of which mechanisms such as efflux pumps and biofilm formation are gaining significant importance. Multidrug resistance mechanisms in ESKAPE pathogens have led to an increase in the effective costs in health care and a higher risk of mortality in hospitalized patients. These pathogens utilize antimicrobial efflux pump mechanisms and bacterial biofilm-forming capabilities to escape the bactericidal action of antimicrobials. ESKAPE bacteria forming colonies demonstrate increased expression of efflux pump-encoding genes. Efflux pumps not only expel antimicrobial agents but also contribute to biofilm formation by bacteria through (1) transport of molecules and transcription factors involved in biofilm quorum sensing, (2) bacterial fimbriae structure transport for biofilm adhesion to surfaces, and (3) regulation of a transmembrane gradient to survive the difficult conditions of biofilm microenvironments. The synergistic role of these mechanisms complicates treatment outcomes. Given the mechanistic link between biofilms and efflux pumps, therapeutic strategies should focus on targeting anti-biofilm mechanisms alongside efflux pump inactivation with efflux pump inhibitors. This review explores the molecular interplay between efflux pumps and biofilm formation, emphasizing potential therapeutic strategies such as efflux pump inhibitors (EPIs) and biofilm-targeting agents. Full article

Efflux is one of the key mechanisms used by Gram-negative bacteria to reduce internal antibiotic concentrations. These active transport systems recognize and expel a wide range of toxic molecules, including antibiotics, thereby contributing to reduced antibiotic susceptibility and allowing the bacteria to acquire additional resistance mechanisms. To date, unlike other resistance mechanisms such as enzymatic modification or target mutations/masking, efflux is challenging to detect and counteract in clinical settings, and no standardized methods are currently available to diagnose or inhibit this mechanism effectively. This review first outlines the structural and functional features of major efflux pumps in Gram-negative bacteria and their role in antibiotic resistance. It then explores various strategies used to curb their activity, with a particular focus on efflux pump inhibitors under development, detailing their structural classes, modes of action, and pharmacological potential. We discuss the main obstacles to their development, including the structural complexity and substrate promiscuity of efflux mechanisms, the limitations of current screening methods, pharmacokinetic and tissue distribution issues, and the risk of off-target toxicity. Overcoming these multifactorial barriers is essential to the rational development of less efflux-prone antibiotics or of efflux pump inhibitors. Full article

The global rise of carbapenem-resistant Acinetobacter baumannii (CRAB) strains poses a critical challenge to healthcare systems due to limited therapeutic options and high mortality rates, especially in intensive care settings. This review explores the epidemiological landscape and molecular mechanisms driving carbapenem resistance, including the production of diverse beta-lactamases (particularly OXA-type enzymes), porin loss, efflux pump overexpression, and mutations in antibiotic targets. Emerging treatment strategies are discussed, such as the use of new beta-lactam–beta-lactamase inhibitor combinations (e.g., sulbactam–durlobactam), siderophore cephalosporins, next-generation polymyxins, as well as novel agents like zosurabalpin and rifabutin (BV100). Alternative approaches—including phage therapy, antimicrobial peptides, CRISPR-based gene editing, and nanoparticle-based delivery systems—are also evaluated for their potential to bypass traditional resistance mechanisms. Furthermore, advances in artificial intelligence and multi-omics integration are highlighted as tools for identifying novel drug targets and predicting resistance profiles. Together, these innovations represent a multifaceted strategy to overcome CRAB infections, yet their successful implementation requires further clinical validation and coordinated surveillance efforts. This analysis highlights the urgent need for continued investment in innovative treatments and effective resistance monitoring to limit the spread of CRAB and protect the effectiveness of last-line antibiotics. Full article

In recent years, one of the most important issues in public health is the rapid growth of antibiotic resistance among pathogens. Multidrug-resistant (MDR) strains (mainly Enterobacteriaceae and non-fermenting bacilli) cause severe infections, against which commonly used pharmaceuticals are ineffective. Therefore, there is an urgent need for new treatment options and drugs with innovative mechanisms of action. Natural compounds, especially alkaloids, are showing promising potential in this area. This review focuses on the ability of the isoquinoline alkaloid berberine (BRB) to overcome various resistance mechanisms against conventional antimicrobial agents. BRB has demonstrated significant activity in inhibiting efflux pumps of the RND (Resistance-Nodulation-Cell Division) family, such as MexAB-OprM (P. aeruginosa) and AdeABC (A. baumannii). Moreover, BRB was able to decrease quorum sensing activity in both Gram-positive and Gram-negative pathogens, resulting in reduced biofilm formation and lower bacterial virulence. Additionally, BRB has been identified as a potential inhibitor of FtsZ, a key protein responsible for bacterial cell division. Particularly noteworthy, though requiring further investigation, are reports suggesting that BRB might inhibit β-lactamase enzymes, including NDM, AmpC, and ESβL types. The pleiotropic antibacterial actions of BRB, distinct from the mechanisms of traditional antibiotics, offer hope for breaking bacterial resistance. However, more extensive studies, especially in vivo, are necessary to fully evaluate the clinical potential of BRB and determine its practical applicability in combating antibiotic-resistant infections. Full article

Helicobacter pylori is a Gram-negative bacterium that infects almost half of the global population and is linked to gastric conditions like peptic ulcers and gastric cancer, as well as other diseases such as neurological disorders, cardiovascular problems, and iron deficiency anemia. Its survival in the acidic stomach environment is due to virulence factors like urease, flagella, and adhesion proteins (BabA, SabA). Current treatments involve a combination of antibiotics (clarithromycin, metronidazole, amoxicillin, tetracycline) and proton pump inhibitors, but increasing antibiotic resistance, especially to clarithromycin and metronidazole, poses a major challenge. Resistance mechanisms include mutations in drug targets, efflux pump overexpression, and enzymatic degradation of antibiotics. This has prompted exploration of alternative therapies targeting bacterial processes like urease activity, biofilm formation, and metabolic pathways (energy production, amino acid synthesis, iron acquisition). Natural compounds, such as chitosan and plant extracts, show promise in combating H. pylori growth and virulence. Vaccine development is also ongoing, with DNA vaccines showing potential for broad immune responses. However, no vaccine is yet close to widespread clinical use. Full article

The dramatic increase in antimicrobial resistance (AMR) in recent decades has created an urgent need to develop new antimicrobial agents and compounds that can modify and/or block bacterial resistance mechanisms. An understanding of these resistance mechanisms and how to overcome them would substantially assist in the development of new antibiotic chemotherapies. Bacteria may develop AMR through multiple differing mechanisms, including modification of the antibiotic target site, limitation of antibiotic uptake, active efflux of the antibiotic, and via direct modification and inactivation of the antibiotic. Of these, efflux pumps and the production of β-lactamases are the most common resistance mechanisms that render antibiotics inactive. The development of resistance-modifying agents (particularly those targeting efflux pumps and β-lactamase enzymes) is an important consideration to counteract the spread of AMR. This strategy may repurpose existing antibiotics by blocking bacterial resistance mechanisms, thereby increasing the efficacy of the antibiotic compounds. This review focuses on known phytochemicals that possess efflux pump inhibitory and/or β-lactamase inhibitory activities. The interaction of phytochemicals possessing efflux pumps and/or β-lactamase inhibitory activities in combination with clinical antibiotics is also discussed. Additionally, the challenges associated with further development of these phytochemicals as potentiating agents is discussed to highlight their therapeutic potential, and to guide future research. Full article

Background: The efflux system is one of the resistance mechanisms that bacteria use to reduce the effectiveness of antibiotics, leading to the development of multidrug resistance. To evaluate other treatment choices, esomeprazole (ESO), omeprazole (OME), pantoprazole (PAN), vitamin D (VD), and vitamin K (VK) were tested for potential efflux pump (EP)-inhibiting activity. Methods: The minimum inhibitory concentrations (MICs) of the tested drugs were determined against K. pneumoniae ATCC 51503 and P. aeruginosa PAO1. Quantitative estimation of the EP-inhibiting activity of the tested medications was phenotypically investigated with a semi-automated fluorometric system and genotypically confirmed by real-time polymerase chain reaction (RT-PCR). Data were confirmed through docking study. Results: K. pneumoniae ATCC 51503 and P. aeruginosa PAO1 were positive efflux standard strains. VD and VK revealed an MIC_VD of 625–1250 µg/mL and MIC_VK of 2500–5000 µg/mL, lower than what was detected for PPIs (MIC_PPIs = 16,000–32,000 µg/mL). Vitamins showed powerful anti-efflux activity with remarkable ethidium bromide accumulation in K. pneumoniae ATCC 51503 and P. aeruginosa PAO1. Also, VD and VK significantly lowered the MIC of ciprofloxacin by 64-fold. On the molecular level, OME showed a notable decrease in the relative expression of the efflux-encoding genes acrB and mexA by 91.5% and 99.7% in ATCC 51503 and PAO1, respectively. Conclusion: This study highlights the anti-efflux activity of ESO, OME, PAN, VD, and VK against the tested Gram-negative strains. Hence, these PPIs and vitamins could be valuable adjuvant treatments to enhance the effectiveness of curing infections caused by MDR strains. Full article

The genus Terminalia has a long history of use in traditional medicine to treat various diseases, including bacterial infections. We previously reported a metabolomic analysis using liquid chromatography–mass spectrometry of selected Australian Terminalia spp. and highlighted numerous flavonoids that may contribute to the antimicrobial activities of those plants. This study examines the antibacterial activities of fifteen flavonoids found in Terminalia spp. against a range of gastrointestinal pathogens using broth dilution assays. Flavonoids were also combined with six different classes of conventional antibiotics to investigate interactions. The efflux pump inhibitory activity of the flavonoid was evaluated using ethidium bromide accumulation and efflux assays. Toxicities were assessed via human dermal fibroblast cell line assays. Fisetin, hispidulin, isoorientin, orientin, rutin, and vitexin showed noteworthy growth inhibitory activity (MIC values 62.5–250 µg/mL). Isoorientin and orientin were most potent against Bacillus cereus and Alcaligenes faecalis, displaying MIC values of 62.5 µg/mL against both bacteria. All flavonoids except genistein, isorhamnetin, kaempferol, luteolin, taxifolin, and vitexin were nontoxic in human dermal fibroblast (HDF) cell proliferation assays. When individual flavonoids were combined with selected antibiotics, some potentiated the activity of these antibiotics. Two synergistic, eighteen additive and thirty-one non-interactive interactions were observed. The synergistic interactions were all observed in combination with orientin. Notably, orientin exhibited efflux pump inhibitory effects at concentrations from 15.26 µg/mL to 125 µg/mL. The findings reported herein indicate that the selected flavonoids have the potential for addressing bacterial antibiotic resistance and highlight the need for further study. Full article

P-glycoprotein (P-gp), a transmembrane efflux pump encoded by the ABCB1/MDR1 gene, is a major contributor to multidrug resistance in hematological malignancies. These malignancies, arising from hematopoietic precursors at various differentiation stages, can manifest in the bone marrow, circulate in the bloodstream, or infiltrate tissues. P-gp overexpression in malignant cells reduces the efficacy of chemotherapeutic agents by actively expelling them, decreasing intracellular drug concentrations, and promoting multidrug resistance, a significant obstacle to successful treatment. This review examines recent advances in combating P-gp-mediated resistance, including the development of novel P-gp inhibitors, innovative drug delivery systems (e.g., nanoparticle-based delivery), and strategies to modulate P-gp expression or activity. These modulation strategies encompass targeting relevant signaling pathways (e.g., NF-κB, PI3K/Akt) and exploring drug repurposing. While progress has been made, overcoming P-gp-mediated resistance remains crucial for improving patient outcomes. Future research directions should prioritize the development of potent, selective, and safe P-gp inhibitors with minimal off-target effects, alongside exploring synergistic combination therapies with existing chemotherapeutics or novel agents to effectively circumvent multidrug resistance in hematological malignancies. Full article

The global healthcare system is increasingly challenged by the rising prevalence of multidrug-resistant bacteria and the limited therapeutic options for related infections. Efflux-mediated antibiotic resistance represents a significant obstacle, primarily due to the absence of drugs specifically designed to target bacterial efflux pumps. Recent research has identified polyphenols, a broad class of plant-derived organic compounds, as potential inhibitors of efflux pump activity. This review consolidates data on the inhibitory properties of eight widely distributed polyphenols: curcumin, quercetin, luteolin, tannic acid, naringenin, epigallocatechin-3-gallate, ellagic acid, and resveratrol. These compounds have demonstrated the capacity to inhibit efflux pumps, either through direct interference with bacterial protein function or by downregulating the expression of genes encoding pump subunits. Importantly, several polyphenols exhibit synergistic interactions with antibiotics, including colistin, ciprofloxacin, and tetracycline. For instance, quercetin has shown inhibitory potency comparable to that of established efflux pump inhibitors such as verapamil and reserpine. These findings suggest that polyphenols represent promising candidates for the development of novel efflux pump inhibitors. However, further research is required to validate their efficacy and safety and facilitate their translation into clinical applications for combating antibiotic resistance. Full article

Antibiotic-resistant Pseudomonas aeruginosa is a pathogen notorious for its resilience in clinical settings due to biofilm formation, efflux pumps, and the rapid acquisition of resistance genes. With traditional antibiotic therapy rendered ineffective against Pseudomonas aeruginosa infections, we explore alternative therapies that have shown promise, including antimicrobial peptides, nanoparticles and quorum sensing inhibitors. While these approaches offer potential, they each face challenges, such as specificity, stability, and delivery, which require careful consideration and further study. We also delve into emerging alternative strategies, such as bacteriophage therapy and CRISPR-Cas gene editing that could enhance targeted treatment for personalized medicine. As most of them are currently in experimental stages, we highlight the need for clinical trials and additional research to confirm their feasibility. Hence, we offer insights into new therapeutic avenues that could help address the pressing issue of antibiotic-resistant Pseudomonas aeruginosa, with an eye toward practical applications in future healthcare. Full article

Helicobacter pylori is a Gram-negative bacterium from the Epsilonproteobacteria class, associated with various gastric diseases, including gastric cancer. It infects both adults and children, with a high prevalence in developing countries due to poor health conditions. The International Agency for Research on Cancer has classified H. pylori as a class I carcinogen, linked not only to gastric cancer but also to neurological disorders. Current treatment involves proton pump inhibitors combined with antibiotics for 10 to 14 days, but patient non-compliance can lead to increased antibiotic resistance. This review examines studies from the past decade that explore flavonoids as potential future treatments for H. pylori. Flavonoids like kaempferol, rutin, quercetin, myricetin, catechin, epicatechin, eupatilin, chrysin, apigenin, and hesperetin have been shown to regulate the expression of key H. pylori genes, alter cell membrane permeability, and affect proton efflux. These biomolecules, found in various plants, have demonstrated the potential to inhibit H. pylori, even in resistant strains. Gene expression and molecular docking studies reveal how these flavonoids interact with the membrane, bacterial genes, and proteins, affecting host cell transcription, translation, and bacterial adherence. While promising, clinical trials are needed to better understand their mechanisms and efficacy. Full article

Background/Objectives: Multidrug resistance is one the leading problems in cancer treatment, where the overexpression of P-gp and other drug efflux pumps is regarded as the primary cause. With the intention to develop transporter inhibitors, natural products such as phenolics have shown great potential and diverse attention recently. Among these, isorhamnetin (ISO), an O-methylated flavonol, is predominantly found in the fruits and leaves of various plants. Thus, this study aimed to investigate the effects of ISO on the mRNA expression of membrane transporters P-gp, BCRP, MRP 1, 2, and 5, the protein expression of P-gp, as well as the GSTP1 and GSH content in DLD1 and HCT-116 colon cancer cells. Methods: The cytotoxic effect of isorhamnetin is assessed using an MTT test, while qPCR and immunocytochemistry methods were used to determine gene and protein expression levels. The concentration of reduced glutathione was determined using the colorimetric method. Results: Based on the results, ISO can modulate the expression of transporters responsible for the resistance development (all transporters on the transcriptional level were downregulated in DLD1 cells, while only MRP1 on HCT-116 cells, and reduced P-gp protein expression on both investigated cell lines). Increased glutathione content in treated cells and GSTP1 expression suggest metabolizing the ISO and potential ejection with GSH-dependent pumps. Conclusions: Thus, in future experiments, ISO as a natural medicinal compound could be used as a chemosensitizer to prevent or overcome membrane transporter-mediated drug resistance. Full article

Background: Staphylococcus aureus is a highly lethal Gram-positive bacterium that is responsible for over one million deaths annually. As a member of the ESKAPE pathogens, its methicillin-resistant strains (MRSA) are prevalent worldwide and exhibit significant antimicrobial resistance (AMR). Bacterial efflux pumps play a pivotal role in the development of AMR by facilitating the expulsion of a range of antimicrobial agents. Methods: The S. aureus strain SA-1199B, which overexpresses NorA and carries a GrlA mutation, was utilized to comprehensively profile the mechanism of the compounds PQQ16P and PQK4F. To assess the toxicity and genotoxicity of these compounds, RAW macrophages, HEK 293T, and HepG2 cell lines were utilized. Female BALB/c mice were utilized to assess the in vivo synergism of EPIs with CPX, Results: NorA efflux pump inhibitors (EPIs), PQQ16P and PQK4F, enhanced the efficacy of the antibacterial ciprofloxacin (CPX) against resistant S. aureus strains. The mechanism of EPIs involved the inhibition of NorA efflux pump, without compromising bacterial membrane permeability, ATP levels, or mammalian calcium channels. Moreover, the EPIs significantly augmented the bactericidal and post-antibiotic effects of CPX, elevating its mutation prevention concentration without manifesting substantial toxicity to human cells. Furthermore, the EPIs reduced S. aureus invasiveness in macrophages, indicating a role for NorA in bacterial virulence. Notably, the in vivo synergism of these EPIs with CPX was observed in a mouse infection model. Conclusions: This study provides substantial evidence for the potential of employing EPIs in a combination with CPX to counteract AMR, both in vitro and in vivo. Full article

Non-fermenting Gram-negative bacteria (NFGNB) are a heterogeneous group of opportunistic pathogens increasingly associated with healthcare-associated infections. While Pseudomonas aeruginosa, Acinetobacter baumannii, and Stenotrophomonas maltophilia are well known, rarer species such as Burkholderia cepacia complex, Achromobacter spp., Chryseobacterium spp., Elizabethkingia spp., Ralstonia spp., and others pose emerging therapeutic challenges. Their intrinsic and acquired resistance mechanisms limit effective treatment options, making targeted therapy essential. Objectives: This narrative review summarizes the current understanding of rare and unusual NFGNB, their clinical significance, resistance profiles, and evidence-based therapeutic strategies. Methods: A literature review was conducted using PubMed, Scopus, and Web of Science to identify relevant studies on the epidemiology, antimicrobial resistance, and treatment approaches to rare NFGNB. Results: Rare NFGNB exhibits diverse resistance mechanisms, including β-lactamase production, efflux pumps, and porin modifications. Treatment selection depends on species-specific susceptibility patterns, but some cornerstones can be individuated. Novel β-lactam/β-lactamase inhibitors and combination therapy approaches are being explored for multidrug-resistant isolates. However, clinical data remain limited. Conclusions: The increasing incidence of rare NFGNB requires heightened awareness and a tailored therapeutic approach. Given the paucity of clinical guidelines, antimicrobial stewardship and susceptibility-guided treatment are crucial in optimizing patient outcomes. Full article