Broad-spectrum Antimicrobial Activity Research Articles

Biological, phytochemical and molecular docking characteristics of Laurus nobilis L. fresh leaves essential oil from Palestine

BackgroundThe historical use of Laurus nobilis L., the plant is native to the Mediterranean region and has been cultivated for its aromatic leaves, which are used as a flavoring agent in cooking and for their potential therapeutic properties.MethodsThe purpose of the current investigation was to characterize the essential oil composition of the fresh L. nobilis leaves from Palestine by using the gas chromatography-mass spectrometry (GC-MS) technique. DPPH (2,2-diphenyl-1-picrylhydrazyl), p-nitrophenyl butyrate, and 3,5-dinitro salicylic acid (DNSA) methods were employed to estimate the antioxidant, antiobesity, and antidiabetic effects of the essential oil. While MTS assay were used to evaluate their antiproliferative activities on panels of cell lines. Moreover, the docking studies were aided by the Prime MM GBSA method for estimating binding affinities.ResultsThe GC-MS investigation demonstrated that the fresh L. nobilis leaves essential oil has a variety of chemicals, about 31 different biochemicals were identified, and the major compounds were 1,8-cineole (48.54 ± 0.91%), terpinyl acetate (13.46 ± 0.34%), and α-terpinyl (3.84 ± 0.35%). Furthermore, the investigated oil demonstrated broad-spectrum antimicrobial activity against all tested bacterial and candidal strains and significantly inhibited the growth of MCF-7 cancerous cells more than the chemotherapeutic drug Doxorubicin. Furthermore, it contains robust DPPH free radicals, as well as porcine pancreatic α-amylase and lipase enzymes. Using the 1,8-cineole compound as the predominant biomolecule found in the L. nobilis essential oil, molecular docking studies were performed to confirm these observed fabulous results. The molecular docking simulations proposed that these recorded biological activities almost emanated from its high ability to form strong and effective hydrophobic interactions, this led to the getting of optimal fitting and interaction patterns within the binding sites of the applied crystallographic protein targets.ConclusionThe results of these experiments showed that the fresh L. nobilis leaves essential oil has outstanding pharmacological capabilities, making this oil a potential source of natural medications.

Photosensitizer-Amplified Antimicrobial Materials for Broad-Spectrum Ablation of Resistant Pathogens in Ocular Infections.

The emergence of multidrug resistant (MDR) pathogens and the scarcity of new potent antibiotics and antifungals are one of the biggest threats to human health. Antimicrobial photodynamic therapy (aPDT) combines light and photosensitizers to kill drug-resistant pathogens; however, there are limited materials that can effectively ablate different classes of infective pathogens. In the present work, a new class of benzodiazole-paired materials is designed as highly potent PDT agents with broad-spectrum antimicrobial activity upon illumination with nontoxic light. The results mechanistically demonstrate that the energy transfer and electron transfer between nonphotosensitive and photosensitive benzodiazole moieties embedded within pathogen-binding peptide sequences result in increased singlet oxygen generation and enhanced phototoxicity. Chemical optimization renders PEP3 as a novel PDT agent with remarkable activity against MDR bacteria and fungi as well as pathogens at different stages of development (e.g., biofilms, spores, and fungal hyphae), which also prove effective in an ex vivo porcine model of microbial keratitis. The chemical modularity of this strategy and its general compatibility with peptide-based targeting agents will accelerate the design of highly photosensitive materials for antimicrobial PDT.

Indigenous Ethiopian traditional medicinal plant leaf extract, Croton macrostachyus, loaded PCL electrospun nanofibrous mat as potential wound dressing: In vitro analysis

The main aim of this study was to investigate the potential application of an indiginous Ethiopian medicinal plant, Croton macrostachyus, into PCL nanofibers through electrospinning for the first time. Croton macrostachyus (CM) leaf has antibacterial and wound healing properties. Croton macrostachyus of 1%, 3%, 5%, and 7% (w/v) incorporated PCL nanofibrous mats were produced through electrospinning. The produced nanofibrous mats morphology observed by scanning electron microscopy (SEM) was found to be continuous, bead-free, and interconnected. The average diameters of PCL, PCL-1%CM, PCL-3%CM, PCL-5%CM, and PCL-7%CM nanofibrous mat is 309 ± 114, 271 ± 66, 235 ± 56, 226 ± 65, and 216 ± 42 nm, respectively. According to the FTIR results, the CM leaf extract was successfully incorporated into the PCL nanofibers. The bacterial reduction percentage value of PCL-1%CM, PCL-3%CM, PCL-5%CM, and PCL-7%CM nanofiber mats against S. aureus is 77.00%, 99.88%, 99.91%, and 99.99%, and 35.00%, 78.00%, 90.00%, and 99.30% against E. coli. The in vitro release study showed that there was an immediate release of CM within 24 h and then a steady sustained release of 51.36, 53.92, 54.99, and 57.12% up to 72 h at 1%, 3%, 5%, and 7% concentration, respectively. The presence of CM leaf extract in the PCL nanofiber increased the hydrophilicity of the pure PCL nanofiber (100% hydrophilic at 7% leaf extract concentration). In general, the results of the in vitro study confirmed that the PCL nanofibrous mats loaded with CM leaf extract are suitable for use as an effective wound dressing with a broad spectrum of antimicrobial activity and hydrophilic properties.

Heterologous expression of frog antimicrobial peptide Odorranain-C1 in Pichia pastoris: Biological characteristics and its application in food preservation

To reduce food spoilage and deterioration caused by microbial contamination, antimicrobial peptides (AMPs) have gradually gained attention as a biological preservative. Odorranain-C1 is an α-helical cationic antimicrobial peptide extracted from the skin of frogs with broad-spectrum antimicrobial activity. In this study, we achieved the expression of Odorranain-C1 in Pichia pastoris (P. pastoris) (also known as Komagataella phaffii) by employing DNA recombination technology. The recombinant Odorranain-C1 showed broad-spectrum antibacterial activity and displayed a minimum inhibitory concentration within the range of 8–12 μg.mL-1. Meanwhile, Odorranain-C1 exhibited superior stability and lower hemolytic activity. Mechanistically, Odorranain-C1 disrupted the bacterial membrane's integrity, ultimately causing membrane rupture and subsequent cell death. In tilapia fillets preservation, Odorranain-C1 inhibited the total colony growth and pH variations, while also reducing the production of total volatile basic nitrogen (TVB-N) and thiobarbituric acid (TBA). In conclusion, these studies demonstrated the efficient recombinant expression of Odorranain-C1 in P. pastoris, highlighting its promising utilization in food preservation.

A First-in-Human Randomized Clinical Study Investigating the Safety and Tolerability of Stabilized Hypochlorous Acid in Patients with Chronic Leg Ulcers.

Objective: Biofilm infections in chronic wounds are common and pose a significant clinical challenge. This challenge was addressed by developing the SoftOx Biofilm Eradicator (SBE) composed of hypochlorous acid (HOCl) and acetic acid with strong broad-spectrum antimicrobial activity. Approach: First-in-human study investigating the safety and tolerability as primary endpoints and wound size effect and antimicrobial efficacy as secondary endpoints of SBE treatment in chronic leg wound patients. The study was divided into two as follows: a randomized, double-blinded, Single Ascending Dose (SAD) phase (n = 16 SBE; n = 4 placebo), where patients were treated with SBE or saline (placebo) only once, followed by an open-label, Multiple Ascending Dose (MAD) phase (n = 8), where patients were treated with SBE once daily or twice daily over five days. Reporting is according to CONSORT guidelines. Results: SBE was safe and well-tolerated in chronic leg wound patients. There were no significant differences in pain during and after treatment with SBE or the placebo. The SBE treatment reduced bioburden in wounds compared to baseline, with 98% and 49% median reduction after SBE or placebo treatment, respectively. A dose-dependent trend in absolute wound size reduction was observed in the MAD groups with a median (min, max) change of -2.99 (-14.25, -1.5) cm2 in the once-daily and -10.48 (-17.95, -0.38) cm2 in the twice-daily group, respectively. Innovation and Conclusion: This study demonstrated the safe use of HOCl-based SBE in chronic leg wounds with promising trends of immediate antimicrobial action and beneficial effect on wound healing.

The Effect of Nanoscale Modification of Nisin by Different Milk-Derived Proteins on Its Physicochemical Properties and Antibacterial Activity.

Nisin is used as a natural food preservative because of its broad-spectrum antimicrobial activity against Gram-positive bacteria. However, free nisin is susceptible to various factors that reduce its antimicrobial activity. Milk protein, a protein derived from milk, has self-assembly properties and is a good carrier of bioactive substances. In this study, lactoferrin-nisin nanoparticles (L-N), bovine serum albumin-nisin nanoparticles (B-N), and casein-nisin nanoparticles (C-N) were successfully prepared by a self-assembly technique, and then their properties were investigated. The studies revealed that lactoferrin (LF) and nisin formed L-N mainly through hydrophobic interactions and hydrogen bonding, and L-N had the best performance. The small particle size (29.83 ± 2.42 nm), dense reticular structure, and good thermal stability, storage stability, and emulsification of L-N laid a certain foundation for its application in food. Further bacteriostatic studies showed that L-N enhanced the bacteriostatic activity of nisin, with prominent inhibitory properties against Listeria monocytogenes, Staphylococcus aureus, and Bacillus cereus, which mainly disrupted the cell membrane of the bacteria. The above results broaden our understanding of milk protein-nisin nanoparticles, while the excellent antibacterial activity of L-N makes it promising for application as a novel food preservative, which will help to improve the bioavailability of nisin in food systems.

In vitro characterization of lactic acid bacteria from Indian fermented rice for probiotic applications

AimTo investigate probiotic attributes of lactic acid bacteria (LAB) isolated from under-explored Indian fermented rice for potential application in consumer health and functional product development. Methods and resultsThe isolates endured conditions resembling gastric stress, including pH (3), bile salt (4%), NaCl (6%), and phenol (0.6%). The selected isolates were identified as L. fermentum and L. plantarum strains by 16 S rRNA sequencing. In a simulated gastrointestinal tract (GIT), isolate SR1 outperformed other cultures in terms of viability. Auto-aggregation, and mucin adhesion abilities were tested for colonization potential. In which, compared to other isolates, MCR1 showed greater mucin adherence. SR1 and MCR1 showed higher percentages of auto-aggregation than GG. The auto-aggregation ranged from 9% to 88%., the levels significantly increase after 24 h incubation. The lower Salt aggregation Test (SAT) values indicated efficient hydrophobicity necessary for persistence in GIT and competitive inhibition to pathogens. All the isolates displayed considerably higher galactosidase activity than GG, isolate FCR2 expressed the highest, up to 613±0.92 Miller’s unit/ml activity. The probiotic candidates displayed broad spectrum antimicrobial activity against food-spoilage fungi and entero-pathogens. The study of safety aspects such as hemolytic, DNase activity, antibiotic susceptibility confirmed unavailability of any virulent factor. ConclusionThe isolates developed substantial galactosidase activity and significant broad-spectrum antibacterial activity. These characteristics make isolates an effective commercial option for β-galactosidase production in the food sector to create low-lactose or lactose-free products. Overall, the isolates' capacity for survival, colonization, and other useful traits may be of commercial relevance. Additionally, isolates can be researched for the production of antibacterial agents and in vivo studies for development of future functional food products. Moreover, these findings lay a robust groundwork for future exploration in probiotics, functional foods and nutraceuticals, while also shedding light on the mechanisms underlying the health benefits of the specified traditional food source. SignificanceThis investigation uncovered potential probiotic LAB of Indian fermented rice origin. By doing so, it expands our understanding of LAB diversity and presents promising candidates for applications in gut health improvement, functional food development, and exploration of natural antibacterial solutions.

Biosynthesis of ZnO-NPs from mycoendophyte Alternaria alternata

Fungi-mediated biosynthesis of nanoparticles is a potentially beneficial strategy for large-scale production. In this study, ZnO-NPs were synthesized biogenically using a cell free broth from mycoendophyte Alternaria alternata inhabiting Piper cubeba as a reducer and stabilizer agent. ZnO-NPs appeared to be spherical in transmission electron microscopy, Histogram reveals the nanoparticle size between 20 and 60 nm, and FTIR experiments were employed to analyze the structure, shape, and physicochemical characteristics of the ZnO-NPs. The biosynthesized nanoparticles exhibited an absorption peak at 346 nm in the UV–visible spectrum, which corresponded to the plasmon resonance of ZnO-NPs. The X-ray diffraction spectra of the nanoparticles revealed the formation of crystal planes and hexagonal crystal geometry metal oxides of zinc. In experiments, biosynthesised ZnO-NPs were proven to be exhibit broad spectrum antimicrobial activity. Based on antimicrobial studies bacteria were found to be more susceptible when compare to fungi exhibiting antibacterial activity equal that of co-assayed standard (18–21 mm zone of inhibition). As a result, ZnO-NPs could be mass-produced sustainably, with the potential to be used in a range of biological processes.

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.

Dual-function antimicrobial-antibiofilm peptide hybrid to tackle biofilm-forming Staphylococcus epidermidis

BackgroundDue to their resistance and difficulty in treatment, biofilm-associated infections are problematic among hospitalized patients globally and account for 60% of all bacterial infections in humans. Antibiofilm peptides have recently emerged as an alternative treatment since they can be effectively designed and exert a different mode of biofilm inhibition and eradication.MethodsA novel antibiofilm peptide, BiF, was designed from the conserved sequence of 18 α-helical antibiofilm peptides by template-assisted technique and its activity was improved by hybridization with a lipid binding motif (KILRR). Novel antibiofilm peptide derivatives were modified by substituting hydrophobic amino acids at positions 5 or 7, and both, with positively charged lysines (L5K, L7K). These peptide derivatives were tested for antibiofilm and antimicrobial activities against biofilm-forming Staphylococcus epidermidis and multiple other microbes using crystal violet and broth microdilution assays, respectively. To assess their impact on mammalian cells, the toxicity of peptides was determined through hemolysis and cytotoxicity assays. The stability of candidate peptide, BiF2_5K7K, was assessed in human serum and its secondary structure in bacterial membrane-like environments was analyzed using circular dichroism. The action of BiF2_5K7K on planktonic S. epidermidis and its effect on biofilm cell viability were assessed via viable counting assays. Its biofilm inhibition mechanism was investigated through confocal laser scanning microscopy and transcription analysis. Additionally, its ability to eradicate mature biofilms was examined using colony counting. Finally, a preliminary evaluation involved coating a catheter with BiF2_5K7K to assess its preventive efficacy against S. epidermidis biofilm formation on the catheter and its surrounding area.ResultsBiF2_5K7K, the modified antibiofilm peptide, exhibited dose-dependent antibiofilm activity against S. epidermidis. It inhibited biofilm formation at subinhibitory concentrations by altering S. epidermidis extracellular polysaccharide production and quorum-sensing gene expression. Additionally, it exhibited broad-spectrum antimicrobial activity and no significant hemolysis or toxicity against mammalian cell lines was observed. Its activity is retained when exposed to human serum. In bacterial membrane-like environments, this peptide formed an α-helix amphipathic structure. Within 4 h, a reduction in the number of S. epidermidis colonies was observed, demonstrating the fast action of this peptide. As a preliminary test, a BiF2_5K7K-coated catheter was able to prevent the development of S. epidermidis biofilm both on the catheter surface and in its surrounding area.ConclusionsDue to the safety and effectiveness of BiF2_5K7K, we suggest that this peptide be further developed to combat biofilm infections, particularly those of biofilm-forming S. epidermidis.

How antimicrobial peptide indolicidin and its derivatives interact with phospholipid membranes: Molecular dynamics simulation

Infections by drug-resistant bacteria pose a growing threat to human health, so developing new antimicrobial drugs is becoming an increasingly urgent requirement. Antimicrobial peptides are an important part of the innate immune system of many organisms, which have a broad spectrum of antimicrobial activity and little likelihood to trigger resistance, so they are considered good candidates for developing new antimicrobial drugs. In this paper, the interaction of indolicidin (IR13) and its derived peptides CP10A, CP-11 and cycloCP-11 with Gram-negative bacterial model membranes is investigated using coarse-grained molecular dynamics approach. The aim is to analyse the behaviour of these antimicrobial peptides when interacting with Gram-negative bacterial membranes. The widely studied phospholipid bilayer consisting of POPC and POPG is used as a Gram-negative bacterial membrane model in the simulations. The results show that the derived peptides CP-11 and cycloCP-11 are more active against Gram-negative bacteria than IR13 and CP10A. The dynamic behaviour of the four antimicrobial peptides on the membrane is different, and the peptide-membrane interactions induce changes in the thickness and surface area of the phospholipid bilayer, diminish membrane mobility, and so on. The present study provides important insights into the mechanism of interaction between antimicrobial peptides and phospholipid membranes by analysing them at the molecular level, and is therefore informative for designing new derivative peptides.

Chemical composition and bioactivity variability of two-step extracts derived from traditional and “QiNan” agarwood (Aquilaria spp.)

One of the primary applications for agarwood lies in the extracts, instead, there are obvious differences in the demands for agarwood components with different application fields. To obtain the rough separation and clarify each part's activity, four extracts of essential oil, hydrolat, extractum, and ethanol precipitation from traditional agarwood (TraA) and “Qinan” agarwood (QinA) were obtained by steam-solvent multistage extraction and ethanol precipitation. We investigated the chemistry and biological activity of multistage extracts using gas chromatography–mass spectrometry (GC–MS), high-performance liquid chromatography (HPLC), and in vitro activity testing. The results demonstrated that two kinds of agarwood essential oils contained mainly sesquiterpenoids, yet the sesquiterpene species were remarkably diverse in two kinds of agarwood essential oils. Then, the TraA and QinA hydrolat, all predominantly aromatic and sesquiterpene, but with differences from the essential oil ingredients. Additionally, the extractum chiefly contained chromones and the ethanol precipitation method worked well to separate the impurities in the TraA extract, however, it was ineffective for the QinA extract. Ultimately, essential oils and extractums all have antioxidant properties, with extractums outperforming essential oils. Moreover, both extractums and essential oils exhibited excellent broad-spectrum antimicrobial activity and anti-inflammatory activity. The findings pointed to the feasibility of separating the primary components from TraA and QinA using a multi-stage extraction technique, providing a scientific basis for the efficient utilization of all components of agarwood, as well as the functional product development and differentiated utilization of extract products in incense, fragrance, perfume, and daily chemicals.

Simultaneous Biofilm Disruption, Bacterial Killing, and Inflammation Elimination for Wound Treatment Using Silver Embellished Polydopamine Nanoplatform.

Due to the presence of spatial barriers, persistent bacteria, and excessive inflammation in bacteria biofilm-infected wounds, current nanoplatforms cannot effectively address these issues simultaneously during the therapeutic process. Herein, a novel biomimetic photothermal nanoplatform integrating silver and polydopamine nanoparticles (Ag/PDAs) that can damage biofilms, kill bacterial persisters, and reduce inflammation for wound treatment is presented. These findings reveal that Ag/PDAs exhibit a broad-spectrum antimicrobial activity through direct damage to the bacterial membrane structure. Additionally, Ag/PDAs demonstrate a potent photothermal conversion efficiency. When combined with near-infrared (NIR) irradiation, Ag/PDAs effectively disrupt the spatial structure of biofilms and synergistically eradicate the resident bacteria. Furthermore, Ag/PDAs show remarkable anti-inflammatory properties in counteracting bacterium-induced macrophage polarization. The in vivo results confirm that the topical application of Ag/PDAs significantly suppress Staphylococcus aureus biofilm-infected wounds in murine models, concurrently facilitating wound healing. This research provides a promising avenue for the eradication of bacterial biofilms and the treatment of biofilm-infected wounds.

Identifying and characterization of novel broad-spectrum bacteriocins from the Shanxi aged vinegar microbiome: Machine learning, molecular simulation, and activity validation

Shanxi aged vinegar microbiome encodes a wide variety of bacteriocins. The aim of this study was to mine, screen and characterize novel broad-spectrum bacteriocins from the large-scale microbiome data of Shanxi aged vinegar through machine learning, molecular simulation and activity validation. A total of 158 potential bacteriocins were innovatively mined from 117,552 representative genes based on metatranscriptomic information from the Shanxi aged vinegar microbiome using machine learning techniques and 12 microorganisms were identified to secrete bacteriocins at the genus level. Subsequently, employing AlphaFold2 structure prediction and molecular dynamics simulations, eight bacteriocins with high stability were further screened, and all of them were confirmed to have bacteriostatic activity by the Escherichia coli BL21 expression system. Then, gene_386319 (named LAB-3) and gene_403047 (named LAB-4) with the strongest antibacterial activities were purified by two-step methods and analyzed by mass spectrometry. The two bacteriocins have broad-spectrum antimicrobial activity with minimum inhibitory concentration values of 6.79 μg/mL-15.31 μg/mL against Staphylococcus aureus and Escherichia coli. Furthermore, molecular docking analysis indicated that LAB-3 and LAB-4 could interact with dihydrofolate reductase through hydrogen bonds, salt-bridge forces and hydrophobic forces. These findings suggested that the two bacteriocins could be considered as promising broad-spectrum antimicrobial agents.

E-CLEAP: An ensemble learning model for efficient and accurate identification of antimicrobial peptides.

With the increasing problem of antimicrobial drug resistance, the search for new antimicrobial agents has become a crucial task in the field of medicine. Antimicrobial peptides, as a class of naturally occurring antimicrobial agents, possess broad-spectrum antimicrobial activity and lower risk of resistance development. However, traditional screening methods for antimicrobial peptides are inefficient, necessitating the development of an efficient screening model. In this study, we aimed to develop an ensemble learning model for the identification of antimicrobial peptides, named E-CLEAP, based on the Multilayer Perceptron Classifier (MLP Classifier). By considering multiple features, including amino acid composition (AAC) and pseudo amino acid composition (PseAAC) of antimicrobial peptides, we aimed to improve the accuracy and generalization ability of the identification process. To validate the superiority of our model, we employed five-fold cross-validation and compared it with other commonly used methods for antimicrobial peptide identification. In the experimental results on an independent test set, E-CLEAP achieved accuracies of 97.33% and 84% for the AAC and PseAAC features, respectively. The results demonstrated that our model outperformed other methods in all evaluation metrics. The findings of this study highlight the potential of the E-CLEAP model in enhancing the efficiency and accuracy of antimicrobial peptide screening, which holds significant implications for drug development, disease treatment, and biotechnology advancement. Future research can further optimize the model by incorporating additional features and information, as well as validating its reliability on larger datasets and in real-world environments. The source code and all datasets are publicly available at https://github.com/Wangsicheng52/E-CLEAP.

AMP-Mimetic Antimicrobial Polymer-Involved Synergic Therapy with Various Coagents for Improved Efficiency.

The misuse of antibiotics contributes to the emergence of multidrug-resistant (MDR) bacteria. Infections caused by MDR bacteria are rapidly evolving into a significant threat to global healthcare due to the lack of effective and safe treatments. Antimicrobial peptides (AMPs) with broad-spectrum antibacterial activity kill bacteria generally through a membrane disruption mechanism; hence, they tend not to induce resistance readily. However, AMPs exhibit disadvantages, such as high cost and susceptibility to proteolytic degradation, which limit their clinical application. AMP-mimetic antimicrobial polymers, with low cost, stability to proteolysis, broad-spectrum antimicrobial activity, negligible antimicrobial resistance, and rapid bactericidal effect, have received extensive attention as a new type of antibacterial drugs. Lately, AMP-mimetic polymer-involved synergic therapy provides a superior alternative to combat MDR bacteria by distinct mechanisms. In this Review, we summarize the AMP-mimetic antimicrobial polymers involved in synergic therapy, particularly focusing on the different combinations between the polymers with commercially available antimicrobials, organic small molecule photosensitizers, inorganic nanomaterials, and nitric oxide.

Enhancing the stability and therapeutic potential of the antimicrobial peptide Feleucin-K3 against Multidrug-Resistant a. Baumannii through rational utilization of a D-amino acid substitution strategy

Antimicrobial peptides (AMPs), which have a low probability of developing resistance, are considered the most promising antimicrobial agents for combating antibiotic resistance. Feleucin-K3 is an amphiphilic cationic AMP that exhibits broad-spectrum antimicrobial activity. In our previous research, the first phenylalanine residue was identified as the critical position affecting its biological activity. Here, a series of Feleucin-K3 analogs containing hydrophobic D-amino acids were developed, leveraging the low sensitivity of proteases to unnatural amino acids and the regulatory effect of hydrophobicity on antimicrobial activity. Among them, K-1dF, which replaced the phenylalanine of Feleucin-K3 with its enantiomer (D-phenylalanine), exhibited potent antimicrobial activity with a therapeutic index of 46.97 and MICs between 4 to 8 μg/ml against both sensitive and multidrug-resistant Acinetobacter baumannii. The introduction of D-phenylalanine increased the salt tolerance and serum stability of Feleucin-K3. Moreover, K-1dF displayed a rapid bactericidal effect, a low propensity to develop resistance, and a synergistic effect when combined with antibiotics. More importantly, it exhibited considerable or superior efficacy to imipenem against pneumonia and skin abscess infection. In brief, the K-1dF obtained by simple and effective modification strategy has emerged as a promising candidate antimicrobial agent for tackling multidrug-resistant Acinetobacter baumannii infections.

Purification, characterization, and identification of a novel bacteriocin produced by Lacticaseibacillus casei KLS1, and its antimicrobial mechanism against Staphylococcus aureus

Staphylococcus aureus (S. aureus) and its biofilm were recognized as one of the major threats to food safety and human health. Bacteriocins produced by Lacticaseibacillus species have been demonstrated to inhibit the growth of foodborne pathogenic bacteria and their biofilm formation. Herein, a novel bacteriocin KLS1 from Lacticaseibacillus casei KLS1 was extracted by ethyl acetate and purified using an AKTA Pure 25 protein chromatography purification system. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyses revealed that the molecular mass of bacteriocin KLSI was 3786.91 Da and the amino acid sequence was DTSASIASNKSETNDLLKQIEAANTEVINLNKQID. Bacteriocin KLS1 was stable at pH 2.0–6.0, sensitive to proteases, and showed excellent thermal stability. Furthermore, bacteriocin KLS1 exhibited broad-spectrum antimicrobial activity against both Gram-positive and Gram-negative bacteria, even fungi. The crystal violet staining assay indicated that bacteriocin KLS1 significantly reduced the relative percentage of S. aureus biofilm (P < 0.05). Meanwhile, bacteriocin KLS1 was found to significantly decrease the metabolic activity of S. aureus by Cell Counting Kit-8 assay (P < 0.05). In addition, scanning electron microscopy and confocal laser scanning microscope showed that bacteriocin KLS1 disrupted the structure of S. aureus biofilm and cell membrane integrity, leading to cell deformation and leakage of contents. These results suggested that bacteriocin KLS1 might have the potential to serve as a biological preservative in the food industry.

Bioactive metabolites from endophytes of African club moss- Selaginella kraussiana (Kunze) A. Braun exhibit broad-spectrum pharmaceutical utilities

The search for potent natural compounds from plant and microbial sources is increasing logarithmically to combat various types of health issues of which multidrug-resistant microbes and problems related to oxidative stress are the prime ones. Novel secondary metabolites from endophytes have always been potent alternatives to contemporary antimicrobials and antioxidants. The present study shows that two potent endophytic fungal isolates Ascochyta medicaginicola SK16 and Phomopsis sp. SK5 synthesises non-proteinaceous, thermostable secondary metabolites with broad-spectrum antimicrobial, antioxidative, and cytotoxic activity. Bioassay-guided fractionation revealed that the Ethyl acetate (EA) extract of the cell-free culture extract (CFCE) of SK5 and SK16 constitutes ten and eleven secondary metabolites of which 2,4, -di tert butyl phenol, aziridine- 1,2-amino ethyl, actinobolin, bactobolin, azulene, menthyl acetate, phenol, p-[2-(methylamino)ethyl], and imidazole components were significant. SK16 exhibited strong antimicrobial activity against seventeen pathogens including Methicillin-resistant Staphylococcus aureus (MRSA), and C. albicans with a minimum microbicidal concentration of 100- 400 µg mL−1. These metabolites disrupt the microbial cell membranes causing lethal leakage of biomacromolecules- nucleic acid, protein, and potassium ions. Enzymes involved in the EMP pathway, TCA cycle, and gluconeogenesis were also blocked. Both the biofilm formation and transition of Candida cells from the yeast-to-hyphal form were inhibited. SK5 metabolites are potent radical scavengers with an IC50 of 34.25 ± 0.87 – 195.21 ± 5.73 µg mL−1 against DPPH, ABTS, FRAP, and H2O2 free radical generators and significantly increased antioxidant parameters in treated peritoneal macrophage cells of male Wistar rats. Also, SK5 metabolites were cytotoxic against breast (T47D), pancreatic (MIA Paca-2), lung (A549) and colon (HCT-116) cancer cells. The present findings suggest that metabolites from endophytes of African club moss hold potent pharmaceutical utilities.

An esculentin-1 homolog from a dark-spotted frog (Pelophylax nigromaculatus) possesses antibacterial and immunoregulatory properties

BackgroundEsculentin-1, initially discovered in the skin secretions of pool frogs (Pelophylax lessonae), has demonstrated broad-spectrum antimicrobial activity; however, its immunomodulatory properties have received little attention.ResultsIn the present study, esculentin-1 cDNA was identified by analysing the skin transcriptome of the dark-spotted frog (Pelophylax nigromaculatus). Esculentin-1 from this species (esculentin-1PN) encompasses a signal peptide, an acidic spacer peptide, and a mature peptide. Sequence alignments with other amphibian esculentins-1 demonstrated conservation of the peptide, and phylogenetic tree analysis revealed its closest genetic affinity to esculentin-1P, derived from the Fukien gold-striped pond frog (Pelophylax fukienensis). Esculentin-1PN transcripts were observed in various tissues, with the skin exhibiting the highest mRNA levels. Synthetic esculentin-1PN demonstrated antibacterial activity against various pathogens, and esculentin-1PN exhibited bactericidal activity by disrupting cell membrane integrity and hydrolyzing genomic DNA. Esculentin-1PN did not stimulate chemotaxis in RAW264.7, a murine leukemic monocyte/macrophage cell line. However, it amplified the respiratory burst and augmented the pro-inflammatory cytokine gene (TNF-α and IL-1β) expression in RAW264.7 cells.ConclusionsThis novel finding highlights the immunomodulatory activity of esculentin-1PN on immune cells.