Search Results (181)

We utilized silver nanoparticles synthesized from bitter melon (Momordica charantia) extracts for testing against the common agricultural pathogen Escherichia coli. The synthesized nanoparticles were characterized and confirmed as silver nanoparticles by using ultraviolet spectroscopy, Fourier transform infrared spectroscopy, and scanning electron microscopy analysis. The results show that AgNPs were effective against E. coli ATCC25922 strain. The AgNPs had an increased potency against the E. coli strain in optimum culture media compared to silver ions alone. AgNP-treated cultures achieved a kill percentage of 100% in less incubation time and at a lower dosage than those treated with silver ions alone. The powder form of the AgNPs also showed remarkable potency against E. coli in solution. Based on these findings, the current method is suitable for the industrial-scale production of AgNPs from a commonly available edible plant with known medicinal benefits in the fight against foodborne pathogens, including antibiotic-resistant strains. Full article

Disruption of the intestinal epithelial barrier is a key driver of gut-derived inflammation in various disorders, yet strategies to preserve or restore barrier integrity remain limited. To address this, we evaluated a four-strain Bifidobacterium mixture—selected for complementary anti-inflammatory potency and industrial scalability—in lipopolysaccharide (LPS)-challenged RAW 264.7 macrophages and a Caco-2/THP-1 transwell co-culture model. Pretreatment with the probiotic blend reduced nitric oxide (NO) release in a dose-dependent manner by 25.9–48.3% and significantly down-regulated the pro-inflammatory markers in macrophages. In the co-culture system, the formulation decreased these markers, increased transepithelial electrical resistance (TEER) by up to 31% at 10⁵ colony-forming unit (CFU)/mL after 48 h, and preserved the membrane localization of tight junction (TJ) proteins. Adhesion to Caco-2 cells (≈ 6%) matched that of the benchmark probiotic Lacticaseibacillus rhamnosus GG, suggesting direct epithelial engagement. These in vitro findings demonstrate that this probiotic mixture can attenuate LPS-driven inflammation and reinforce epithelial architecture, providing a mechanistic basis for its further evaluation in animal models and clinical studies of intestinal inflammatory disorders. Full article

Background: The benzamide MMV030666 from MMV’s Malaria Box Project, the starting point of herein presented study, was initially tested against various Plasmodium falciparum strains as well as Gram-positive and Gram-negative bacteria. It exhibits multi-stage antiplasmodial potencies and lacks resistance development. Methods: The favorable structural features from previous series were kept while the influence of the N-Boc-piperazinyl substituent per se, as well as its ring position and its replacement by various heteroaromatic rings, was evaluated. Thus, this paper describes the preparation of the MMV030666-derived 4′-(piperazin-1-yl)benzanilides for the first time, exhibiting broad-spectrum activity not only against plasmodia but also various bacterial strains. Results: A series of insightful structure–activity relationships were determined. Furthermore, pharmacokinetic and physicochemical parameters of the new compounds were determined experimentally or in silico. Drug-likeliness according to Lipinski’s rules was calculated as well. Conclusions: A diarylthioether derivative of the lead compound was promisingly active against P. falciparum and exhibited broad-spectrum antibacterial activity against Gram-positive as well as Gram-negative bacteria. It is considered for testing against multi-resistant bacterial strains and in vivo studies. Full article

Tuberculosis (TB) poses a persistent global health threat exacerbated by the emergence of drug-resistant strains; hence, there is a continuous quest for novel antimicrobial agents. Despite efforts to develop effective therapies, existing treatments require a relatively long duration of therapy to eradicate the pathogen due to its virulence factors, pathogenesis patterns, and ability to enter dormant states. This can lead to a higher risk of treatment failure due to poor patient adherence to the complex regimen. As a result, considerable research is necessary to identify alternative antituberculosis agents. The marine environment, particularly marine-derived fungi, has recently gained interest due to its potential as an abundant source of bioactive natural products. This review covers 19 genera of marine-derived fungi and 139 metabolites, 131 of which exhibit antimycobacterial activity. The integrated dataset pinpoints the fungal genera and chemical classes that most frequently yield potent antimycobacterial hits while simultaneously exposing critical gaps, such as the minimal evaluation of compounds against dormant bacilli and the presence of underexplored ecological niches and fungal genera. Several compounds exhibit potent activity through uncommon mechanisms, including the inhibition of mycobacterial protein tyrosine phosphatases (MptpB/MptpA), protein kinase PknG, ATP synthase and the disruption of mycobacterial DNA via G-quadruplex stabilization. Structure–activity relationship (SAR) trends are highlighted for the most potent agents, illuminating how specific functional groups underpin target engagement and potency. This review also briefly proposes a dereplication strategy and approaches for toxicity mitigation in the exploration of marine-derived fungi’s natural products. Through this analysis, we offer insights into the potency and challenges of marine-derived fungi’s natural products as hit compounds or scaffolds for further antimycobacterial research. Full article

Background and Objectives: The rising prevalence of drug-resistant organisms presents a significant challenge to healthcare, underscoring the importance of implementing effective antimicrobial stewardship programs. The success of these programs depends on access to accurate, evidence-based data reflecting local patterns of antibiotic resistance. This study aims to assess the antimicrobial susceptibility profiles of gram-positive bacteria isolated from pediatric patients in a tertiary care hospital in Egypt. Materials and Methods: We carried out a retrospective study over a five-year period, from January 2018 to December 2022, using microbiology laboratory records. Clinical samples included blood, urine, respiratory secretions, pus, wound, cerebrospinal fluid (CSF), and pleural fluid. The analysis focused on the resistance patterns of gram-positive pathogens identified through routine culture procedures. Antimicrobial susceptibility testing was performed using the Kirby–Bauer disc diffusion method, and vancomycin MIC was confirmed using the VITEK 2 system. Results: A total of 3223 gram-positive bacterial isolates were identified. Staphylococcus aureus, including 82.5% methicillin-resistant strains (MRSA), exhibited high resistance to erythromycin (47.3%) and gentamicin (low potency) (32.1%). Coagulase-negative staphylococci (CoNS) showed the highest erythromycin resistance (up to 88.3%), while Enterococcus spp. demonstrated declining susceptibility to vancomycin, levofloxacin, and erythromycin. Across all isolates, vancomycin and gentamicin (high potency) showed the highest overall susceptibility. Resistance to cotrimoxazole and doxycycline declined over the five-year period. Conclusions: While a decline in resistance was noted for some agents, persistent resistance to key antibiotics (particularly erythromycin and gentamicin) among MRSA and CoNS remains concerning. These findings underscore the importance of targeted antimicrobial stewardship interventions and continuous surveillance to inform empirical therapy in pediatric settings. Full article

The antimicrobial and antibiofilm efficacy of two Ocimum basilicum L., essential oils sourced from Colombia (BEOC) and Italy (BEOI), was evaluated against multidrug-resistant fish isolates of Salmonella enterica subsp. salamae, Bacillus thuringiensis, and Bacillus oceanisediminis—species for which such activity has not been previously reported. Using a fish-based model system (FBMS), we found that BEOI, rich in linalool (69.86%), exhibited stronger antimicrobial activity than camphor-dominated BEOC (24.61%). The antimicrobial effects of both EOs were strain- and concentration-dependent, with minimum bactericidal concentration (MBC) 3.75–15.0 µL/mL for BEOI and 15.0–30.0 µL/mL for BEOC. Pure linalool showed even greater potency (MBC: 0.0125 to 0.025 µL/mL). Confocal laser scanning microscopy revealed that BEOI induced severe membrane damage (27% of the cells within 1 h), ultimately leading to the death of 96% of the cells after 24 h. Biofilm formation, assessed in both FBMS and tryptone soy broth (TSB), was strain-dependent, with FBMS promoting higher biofilm production than TSB. Moreover, significant differences in biofilm morphotypes were observed, with the morphotype PDAR (pink dry and rough), characterized by only cellulose, being the most frequently exhibited by the strains (7/15), while BDAR (brown dry and rough), characterized by only curli, was the least expressed (7/15); the remaining strains presented morphotype RDAR. In addition, the strains in polystyrene surfaces accumulated more biomass than stainless steel 304. Notably, BEOI and linaool significantly reduced biofilm formation across all strains, with a reduction of 90% in S. enterica subsp. salamae strains (TJC19 and TJC21. These strains with the RDAR phenotype likely contribute to their strong biofilm-forming capacity. Our findings highlight BEOI’s potential as a natural anti-biofilm agent in food processing environments, offering a promising strategy to combat multidrug-resistant bacteria biofilm-related challenges in the food industry. Full article

Extensive use of classical antibiotics has led to the growing emergence of many resistant strains of pathogenic bacteria. To combat this challenge, researchers have turned to the antimicrobial peptides (AMPs). Aurein 1.2 (GLFDIIKKIAESF-NH2) was demonstrated to have broad spectrum bi-functionality against bacterial and cancer cells. The Solid Phase Peptide Synthesis (Fmoc-strategy) was used for the synthesis of new analogs of aurein 1.2. The purity of all compounds was monitored by HPLC, and their structures were proven using mass spectrometry. Cytotoxicity and antiproliferative effects were studied using 3T3 NRU and MTT tests, respectively. The antibacterial activity was estimated against Gram-positive and Gram-negative bacteria using broth microdilution method in concentrations from 0 to 320 µg/mL to determine the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). The antiproliferative activity test shows that the peptide analog EH [Orn]⁸ has the highest activity (IC₅₀ = 44 ± 38 μM) for the three cell lines studied (MCF-12F, MCF-7, and MDA-MB-231). The same compound exhibited good antimicrobial activity. The obtained results reveal that replacement of Lys with non-proteinogenic amino acids can increase both the potency and activity spectra of natural template peptides, making them suitable candidates for new drug development. Full article

Fusidic acid (FA), a tetracyclic triterpenoid, has been approved to treat methicillin-resistant Staphylococcus aureus (MRSA) infections. However, there are few reports about FA derivatives with high efficacy superior to FA, manifesting the difficulty of discovering the derivatives based on experience-based drug design. In this study, we employed a stepwise method to discover novel FA derivatives. First, molecular dynamics (MD) simulations were performed to identify the molecular mechanism of FA against elongation factor G (EF-G) and drug resistance. Then, we utilized a scaffold decorator to design novel FA derivatives at the 3- and 21-positions of FA. The ligand-based and structure-based screening models, including Chemprop and RTMScore, were employed to identify promising hits from the generated set. Ten generated FA derivatives with high efficacy in the Chemprop and RTMScore models were synthesized for in vitro testing. Compounds 4 and 10 demonstrated a 2-fold increase in potency against MRSA strains compared to FA. This study highlights the significant impact of AI-based methods on the design of novel FA derivatives with drug efficacy, which provides a new approach for drug discovery. Full article

Background/Objectives: Monkeypox, twice declared a public health emergency of international concern by the WHO, currently lacks approved targeted therapeutics. This study focused on the development of monkeypox virus (MPXV) E8-specific human monoclonal antibodies (mAbs) derived from recipients of the recombinant vaccinia vaccine (rTV), with subsequent evaluation of their cross-neutralizing activity against orthopoxviruses, including the vaccinia virus (VACV) and MPXV. Methods: Three mAbs (C5, C9, and F8) were isolated from rTV vaccinees. Structural mapping characterized their binding domains on the MPXV E8 and VACV D8 proteins. Neutralization potency was assessed against the VACV TianTan strain and MPXV clade IIb. A combo was further evaluated in a VACV-infected mice model for clinical recovery and viral load reduction. Complement-dependent enhancement mechanisms were also investigated in vitro. Results: C9 targets the virion surface region of E8 and both the virion surface region and intravirion region of D8, showing cross-neutralization activity against the MPXV (IC₅₀ = 3.0 μg/mL) and VACV (IC₅₀ = 51.1 ng/mL) in vitro. All three antibodies demonstrated potent neutralization against the VACV in vitro: C5 (IC₅₀ = 3.9 ng/mL), C9 (IC₅₀ = 51.1 ng/mL), and F8 (IC₅₀ = 101.1 ng/mL). Notably, complement enhanced neutralization against the VACV by >50-fold, although no enhancement was observed for the MPXV. In vivo administration accelerated clinical recovery by 24 h and achieved significant viral clearance (0.9-log reduction). Conclusions: E8-targeting mAbs exhibited broad-spectrum neutralization against orthopoxviruses, demonstrating therapeutic potential against both historical (VACV) and emerging (MPXV) pathogens. However, MPXV’s resistance to complement-dependent enhancement highlights the necessity for pathogen-adapted optimization. These findings establish E8 as a critical conserved target for pan-poxvirus VACV and MPXV countermeasure development. Full article

Background/Objectives: Multidrug-resistant Gram-negative ESKAPE pathogens, including E. coli, K. pneumoniae, P. aeruginosa, and A. baumannii, pose a significant global health threat. Gramicidin S, a potent cyclic antimicrobial peptide, is largely ineffective against these bacteria, and its high haemolytic toxicity limits its clinical usage. This study reports on several novel gramicidin S analogues with improved efficacy and safety profiles against multidrug-resistant Gram-negative bacteria. Methods: A total of 19 gramicidin S derivatives were synthesised using Fmoc-based solid-phase peptide synthesis with targeted substitutions to enhance cationicity and modulate hydrophobicity. Minimum inhibitory concentrations (MICs) were determined against standard Gram-negative and Gram-positive strains. Haemolytic toxicity and in vitro nephrotoxicity were evaluated using human red blood cells and HEK-293 cells, respectively. All peptides were characterised by RP-HPLC and HRMS. Results: The selective incorporation of ^DArg and Trp significantly enhanced activity against Gram-negative bacteria while reducing cytotoxicity. Peptide 8 improved the therapeutic index (TI) against E. coli by 10-fold (MIC: 8 µg/mL; TI: 4.10) compared to gramicidin S (MIC: 32 µg/mL; TI: 0.38). Peptide 9 exhibited an 8-fold potency increase against K. pneumoniae and a 25-fold TI improvement. Peptide 19 enhanced activity against P. aeruginosa 8-fold over gramicidin S, while peptide 7 showed a 27-fold TI enhancement. All active peptides retained broad-spectrum activity against S. aureus, including MRSA. Conclusions: The findings highlight the critical role of balancing hydrophobicity and cationicity to overcome species-specific resistance mechanisms. Our gramicidin S analogues demonstrate potent broad-spectrum activity with significantly reduced toxicity compared to the parent peptide, providing a robust platform for the development of new antibiotics against ESKAPE bacterial pathogens. Full article

Background/Objectives. One of the pressing challenges in global public health is the rise in infections caused by carbapenem-resistant Enterobacteriaceae. Growing bacterial drug resistance, coupled with the slow development of new antibiotics, highlights the critical need to explore and develop new broad-spectrum antimicrobial agents able to inhibit bacterial growth efficiently. In recent years, antimicrobial peptides (AMPs) have gained significant attention as a promising alternative to conventional drugs, owing to their antimicrobial potency, low toxicity, and reduced propensity for fostering resistance. Our research aims to investigate the antibacterial ability of three amphibian AMPs, namely Hylin-a1, AR-23, and RV-23, against both antibiotic-sensitive and carbapenem-resistant strains of Escherichia coli and Klebsiella pneumoniae. Methods. A 3-(4,5 dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay (MTT) was performed to identify non-cytotoxic concentrations of peptides. A microdilution assay evaluated the antibacterial effect, determining the peptides’ minimum inhibitory concentration (MIC). In addition, the checkerboard test analyzed the compounds’ synergistic effect with meropenem. Results. We demonstrated that peptides with low toxicity profile and resistance to proteolytic activity exhibited strong antibacterial activity, with MIC ranging from 6.25 to 25 μM. The antibiofilm mechanism of action of peptides was also investigated, suggesting that they had a crucial role during the biofilm formation step by inhibiting it. Finally, we highlighted the synergistic effects of peptides with meropenem. Conclusions. Our study identifies Hylin-a1, AR-23, and RV-23 as promising candidates against Gram-negative bacterial infections with a favorable therapeutic profile. This effect could be related to their great flexibility, as evidenced by circular dichroism data, confirming that the peptides could assume an α-helical conformation interacting with bacterial membranes. Full article

Background/Objectives: Acne vulgaris is a skin disorder that affects millions worldwide, with Cutibacterium acnes playing a key role in its inflammation. Antibiotics reduce C. acnes and inflammation, but growing antibiotic resistance has limited their efficacy. Additionally, other common acne treatments with bactericidal activity, like benzoyl peroxide, cause irritation, dryness, and peeling. To fulfill the unmet need for alternative therapies, our strategy focused on identifying potent phage lysins and/or their derived cationic peptides. Methods: The C-terminal cationic antimicrobial peptide of the Prevotella intermedia phage lysin PlyPi01 was synthesized along with several sequence-engineered variants in an attempt to enhance their bactericidal efficacy. In vitro bacterial killing assays evaluated the potency of the lysin-derived peptide derivatives against C. acnes and Staphylococcus aureus, another skin bacterium associated with acne. Antibacterial activity was assessed both in conditions simulating the human skin and in combination with retinoids. Results: The variant peptide P156 was engineered by adding arginine residues at both the N- and C-terminal ends of the parental peptide PiP01. P156 was highly potent and eradicated all tested strains of C. acnes and S. aureus. P156 acted rapidly (>5-log kill in 10 min), further reducing the potential of resistance development. Additionally, P156 maintained its potency under conditions (e.g., temperature, pH, and salt concentration) observed on the skin surface and in hair follicles, as well as in combination with retinoid—all without being toxic to human cells. Conclusions: These collective findings position P156 as a promising topical drug for clinical applications to control acne vulgaris. Full article

Melittin, a naturally occurring antimicrobial peptide, demonstrates broad-spectrum activity, effectively suppressing and eliminating both Gram-positive and Gram-negative bacteria, including specific drug-resistant strains. In this study, molecular simulation software was employed to investigate and modify the structure of melittin with the aim of synthesizing a modified peptide exhibiting enhanced antibacterial potency and assessing its bacteriostatic and antibacterial properties. The primary research objectives were as follows: 1. Preparation and characterization of melittin-modified peptide—Using molecular simulation software, the structure of the melittin-modified peptide was adjusted to predict its activity and select the most appropriate amino acid sequence. The peptide was synthesized through solid-phase peptide synthesis employing the Fmoc strategy and subsequently purified using liquid chromatography. The yield of the purified modified melittin was determined to be 30.97%, and the identity of the product was confirmed by LC-MS and MALDI-TOF-MS. 2. Evaluation of the antimicrobial activity of the melittin-modified peptide—The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of melittin and its modified peptide were measured using gradient dilution and plate counting techniques. The results revealed that both melittin and its modified peptide exhibited strong antibacterial efficacy against Gram-positive and Gram-negative bacteria, as well as certain drug-resistant strains. This showed that melittin and its modified peptide have the same antibacterial (killing) effect. A scanning electron microscope analysis indicated that both melittin and its modified peptide were capable of disrupting bacterial cell structures, leading to bacterial cell death. Full article

In recent years, fungal infections have emerged as a significant health concern across veterinary species, especially in livestock such as cattle, where fungal diseases can result in considerable economic losses, as well as in humans. In particular, Aspergillus species, notably Aspergillus flavus and Aspergillus versicolor, are opportunistic pathogens that pose a threat to both animals and humans. This study focuses on the synthesis and antifungal evaluation of novel 9-fluorenylmethoxycarbonyl (Fmoc)-protected 1,2,4-triazolyl-α-amino acids and their dipeptides, designed to combat fungal pathogens. More in detail, we evaluated their antifungal activity against various species, including Aspergillus versicolor (ATCC 12134) and Aspergillus flavus (ATCC 10567). The results indicated that dipeptide 7a exhibited promising antifungal activity against Aspergillus versicolor with an IC₅₀ value of 169.94 µM, demonstrating greater potency than fluconazole, a standard treatment for fungal infections, which showed an IC₅₀ of 254.01 µM. Notably, dipeptide 7a showed slightly enhanced antifungal efficacy compared to fluconazole also in Aspergillus flavus (IC₅₀ 176.69 µM vs. 184.64 µM), suggesting that this dipeptide might be more potent even against this strain. Remarkably, 3a and 7a are also more potent than fluconazole against A. candidus 10711. On the other hand, the protected amino acid 3a demonstrated consistent inhibition across all tested Aspergillus strains, but with an IC₅₀ value of 267.86 µM for Aspergillus flavus, it was less potent than fluconazole (IC₅₀ 184.64 µM), still showing some potential as a good antifungal molecule. Overall, our findings indicate that the synthesized 1,2,4-triazolyl derivatives 3a and 7a hold significant promise as potential antifungal agents in treating Aspergillus-induced diseases in cattle, as well as for broader applications in human health. Our mechanistic studies based on molecular docking revealed that compounds 3a and 7a bind to the same region of the sterol 14-α demethylase as fluconazole. Given the rising concerns about antifungal resistance, these amino acid derivatives, with their unique bioactive structures, could serve as a novel class of therapeutic agents. Further research into their in vivo efficacy and safety profiles is warranted to fully realize their potential as antifungal drugs in clinical and agricultural settings. Full article

Background/Objectives: There is an urgent need for new and improved anthelmintics that are not constrained by existing resistance pathways and that can safeguard the health and welfare of animals. Methods: An integrated platform of chemical, bioassay, and cultivation profiling applied to a library of microbes isolated from Australian livestock pasture soil was used to detect and guide the production, isolation, characterization, identification, and evaluation of new natural products with anthelmintic properties. Results: A global natural products social (GNPS) molecular network analysis of 110 Australian pasture-soil-derived microbial extracts prioritized for antiparasitic activity identified unique molecular families in the extract of Streptomyces sp. S4S-00185A06, a strain selectively active against Dirofilaria immitis microfilariae. UPLC-DAD analysis identified metabolites with unique UV-vis chromophores and unprecedented molecular formulas. A chemical investigation of Streptomyces sp. S4S-00185A06 yielded goondicones A–H (1–8) as new examples of a rare class of spiro-isoindolinones, with structures assigned on the basis of detailed spectroscopic analysis, ECD calculations, and biosynthetic considerations. Conclusions: While goondicones 1–8 exhibit little to no in vitro inhibitory activity against Gram-positive, Gram-negative, and/or fungal pathogens, human carcinoma cells, or the livestock gastrointestinal parasite Haemonchus contortus L1–L3 larvae, 5 and 6 (and, to a lesser extent, 1) inhibit the motility of heartworm Dirofilaria immitis microfilaria (IC₅₀ 10–11 μM). A structure activity relationship analysis based on the co-metabolites 1–8 suggests that (i) an 8-OH is preferable to 8–oxo moiety, (ii) 20-NMe and 3-OH moieties are essential, and (iii) C-9 epimerization exerts no discernible impact on in vitro potency. Full article