Broad-spectrum Antibacterial Activity Research Articles

Antibacterial, Phytochemical and Toxicological Activities of Garcinia kola Extracts against Multidrug Resistant Clinical Bacteria

Objective: The rise in multiple antibiotic resistant microorganisms has led to a decline in the efficacy of many antibiotics, prompting the investigation of alternative solutions such as medicinal plants. To tackle this concerning issue, this study was undertaken to evaluate the phytochemical composition, antibacterial activity, and toxicological characteristics of Garcinia kola extracts against multidrug-resistant bacteria commonly found in clinical settings. Material-Method: The cold maceration technique was employed to extract the root and leaf of Garcinia kola using water and methanol. The extracts were then subjected to phytochemical screening. To evaluate the extracts' potential to inhibit bacterial growth, five multidrug-resistant isolates were utilized in this study. Agar well assay was used to determine the zones of inhibition. The Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) were determined using the broth macro dilution technique. Additionally, Brine shrimp lethality assay was conducted to determine the lethal concentration (LC50) of the extracts. The extracts were also combined for synergism. Results: The investigation found that the root extract in methanol had the highest yield at 25.58%. All four extracts contained ten out of the fourteen tested phytochemicals. The methanol leaf and root extracts exhibited the highest and lowest inhibition zones of 20mm and 9mm against Staphylococcus aureus, respectively. The MIC values ranged from 250 to 600 mg/ml, indicating broad-spectrum antibacterial activity. The cytotoxicity test showed a range of 33.03 to 126.3µg/mL for the aqueous and methanol extracts. Conclusion: Although Garcinia kola shows potential as a source of antibacterial compounds, caution should be exercised due to its toxic effects.

Sprayable biogenic Ag-collagen nanocomposites with potent antibacterial and antibiofilm activity for Acinetobacter baumannii infected wound healing under hyperglycemic condition

Owing to their susceptibility to infection by drug-resistant bacteria, refractory wounds pose a formidable risk to the well-being of patients with diabetes and other immune-compromised conditions, and their management poses significant economic distress to the healthcare system, particularly in low and middle-income countries. Therefore, deployable interventions for rapid and effective management of such wounds are needed. In the present study, we report the processing of sprayable biogenic Ag-collagen nanocomposites (Ag-Col NCs) with cogent antibacterial and healing activity in Acinetobacter baumannii infected wounds under hyperglycemic conditions. Silver nanoparticles (Ag NPs) has been synthesized by using the plant extract of Urginea indica (U. indica), which was further used for the processing of Ag-Col NCs. Synthesized NCs were found to have notable broad spectrum antibacterial activity against clinically significant strains (Acinetobacter baumannii, Staphylococcus aureus and Methicillin-resistant Staphylococcus aureus) and appreciable biocompatibility towards RAW 264.7 and 3 T3 mouse fibroblast cell lines. The sprayable NC system was found to promote the wound healing activity in mouse model (Balb/c) not only in normal but also in hyperglycemic conditions. Our experimental findings suggest the potential of the Ag-Col NC spray in chronic wound management and an exploitable option in both clinical and personalized settings.

Antibacterial Polyketides from the Deep-Sea Cold-Seep-Derived Fungus Talaromyces sp. CS-258.

Thirty-two fungal polyketide derivatives, including eleven new compounds, namely (3R,5'R)-5-hydroxytalaroflavone (1), talaroisochromenols A-C (3, 5, and 11), (8R,9R,10aR)-5-hydroxyaltenuene (13), (8R,9R,10aS)-5-hydroxyaltenuene (14), (8R,9S,10aR)-5-hydroxyaltenuene (15), nemanecins D and E (25 and 26), 2,5-dimethyl-8-iodochromone (27), and talarofurolactone A (29), together with one new naturally occurring but previously synthesized metabolite, 6-hydroxy-4-methoxycoumarin (28), were isolated and identified from the deep-sea cold-seep-derived fungus Talaromyces sp. CS-258. Among them, racemic ((±)-11) or epimeric (13-15, 25, and 26) mixtures were successfully separated by chiral or gradient elution HPLC. Meanwhile, compound 27 represents a rarely reported naturally occurring iodinated compound. Their planar structures as well as absolute configurations were determined by extensive analysis via NMR, MS, single-crystal X-ray diffraction, Mosher's method, and ECD or NMR calculation (with DP4+ probability analysis). Possible biosynthetic routes of some isolated compounds, which are related to chromone or isochromone biosynthetic pathways, were put forward. The biological analysis results revealed that compounds 7, 9, 10, 18-22, 24, 30, and 31 showed broad-spectrum antibacterial activities against several human and aquatic pathogens with MIC ranges of 0.5-64 μg/mL.

Membrane-Active All-Hydrocarbon-Stapled α-Helical Amphiphilic Tat Peptides: Broad-Spectrum Antibacterial Activity and Low Incidence of Drug Resistance.

Multidrug resistance against conventional antibiotics has dramatically increased the difficulty of treatment and accelerated the need for novel antibacterial agents. The peptide Tat (47-57) is derived from the transactivating transcriptional activator of human immunodeficiency virus 1, which is well-known as a cell-penetrating peptide in mammalian cells. However, it is also reported that the Tat peptide (47-57) has antifungal activity. In this study, a series of membrane-active hydrocarbon-stapled α-helical amphiphilic peptides were synthesized and evaluated as antibacterial agents against Gram-positive and Gram-negative bacteria, including multidrug-resistant strains. The impact of hydrocarbon staple, the position of aromatic amino acid residue in the hydrophobic face, the various types of aromatic amino acids, and the hydrophobicity on bioactivity were also investigated and discussed in this study. Among those synthesized peptides, analogues P3 and P10 bearing a l-2-naphthylalanine (Φ) residue at the first position and a Tyr residue at the eighth position demonstrated the highest antimicrobial activity and negligible hemolytic toxicity. Notably, P3 and P10 showed obviously enhanced antimicrobial activity against multidrug-resistant bacteria, low drug resistance, high cell selectivity, extended half-life in plasma, and excellent performance against biofilm. The antibacterial mechanisms of P3 and P10 were also preliminarily investigated in this effort. In conclusion, P3 and P10 are promising antimicrobial alternatives for the treatment of the antimicrobial-resistance crisis.

Enzyme-Triggered Polyelectrolyte Complex for Responsive Delivery of α-Helical Polypeptides to Optimize Antibacterial Therapy.

Responsive nanomaterials hold significant promise in the treatment of bacterial infections by recognizing internal or external stimuli to achieve stimuli-responsive behavior. In this study, we present an enzyme-responsive polyelectrolyte complex micelles (PTPMN) with α-helical cationic polypeptide as a coacervate-core for the treatment of Escherichia coli (E. coli) infection. The complex was constructed through electrostatic interaction between cationic poly(glutamic acid) derivatives and phosphorylation-modified poly(ethylene glycol)-b-poly(tyrosine) (PEG-b-PPTyr) by directly dissolving them in aqueous solution. The cationic polypeptide adopted α-helical structure and demonstrated excellent broad-spectrum antibacterial activity against both Gram-negative and Gram-positive bacteria, with a minimum inhibitory concentration (MIC) as low as 12.5 μg mL-1 against E. coli. By complexing with anionic PEG-b-PPTyr, the obtained complex formed β-sheet structures and exhibited good biocompatibility and low hemolysis. When incubated in a bacterial environment, the complex cleaved its phosphate groups triggered by phosphatases secreted by bacteria, exposing the highly α-helical conformation and restoring its effective bactericidal ability. In vivo experiments confirmed accelerated healing in E. coli-infected wounds.

Zinc oxide nanoparticles mediate bacterial toxicity in Mueller-Hinton Broth via Zn2.

As antibiotic resistance increases and antibiotic development dwindles, new antimicrobial agents are needed. Recent advances in nanoscale engineering have increased interest in metal oxide nanoparticles, particularly zinc oxide nanoparticles, as antimicrobial agents. Zinc oxide nanoparticles are promising due to their broad-spectrum antibacterial activity and low production cost. Despite many studies demonstrating the effectiveness of zinc oxide nanoparticles, the antibacterial mechanism is still unknown. Previous work has implicated the role of reactive oxygen species such as hydrogen peroxide, physical damage of the cell envelope, and/or release of toxic Zn2+ ions as possible mechanisms of action. To evaluate the role of these proposed methods, we assessed the susceptibility of S. aureus mutant strains, ΔkatA and ΔmprF, to zinc oxide nanoparticles of approximately 50 nm in size. These assays demonstrated that hydrogen peroxide and electrostatic interactions are not crucial for mediating zinc oxide nanoparticle toxicity. Instead, we found that Zn2+ accumulates in Mueller-Hinton Broth over time and that removal of Zn2+ through chelation reverses this toxicity. Furthermore, we found that the physical separation of zinc oxide nanoparticles and bacterial cells using a semi-permeable membrane still allows for growth inhibition. We concluded that soluble Zn2+ is the primary mechanism by which zinc oxide nanoparticles mediate toxicity in Mueller-Hinton Broth. Future work investigating how factors such as particle morphology (e.g., size, polarity, surface defects) and media contribute to Zn2+ dissolution could allow for the synthesis of zinc oxide nanoparticles that possess chemical and morphological properties best suited for antibacterial efficacy.

Fabrication and antimicrobial properties of novel meropenem-honey encapsulated chitosan nanoparticles against multiresistant and biofilm-forming Staphylococcus aureus as a new antimicrobial agent.

Honey exhibits a broad spectrum of antibacterial activity against Gram-positive and Gram-negative bacteria, including methicillin-resistant Staphylococcus aureus (MRSA) ones. Chitosan (Cs) is a mucoadhesive polymer that also has antibacterial properties. Special attention has been paid to the design of polymeric nanoparticles (NPs) as new nano drug delivery systems to overcome bacterial resistance and its problems. The aim of the present study is to synthesize Cs-meropenem NPs with/without honey as an antibiofilm and antibacterial agent to inhibit Staphylococcus aureus. This study synthesized meropenem and honey-loaded Cs nanogels and subsequently characterized them by Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared Spectroscopy (FTIR), and DLS-zeta potential. Using the broth microdilution and crystal violet assays, the antibacterial and antibiofilm activity of meropenem and honey-loaded Cs nanogel, free meropenem, free honey, and free Cs NPs were investigated in vitro against MRSA strains. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) was also used to test the cytotoxicity of several Cs-NPs compound against the HEK-293 regular cell line. The average size of meropenem and honey-Cs-NPs was reported to be 119.885nm, and encapsulation efficiency was 88.33 ± 0.97 with stability up to 60 days at 4°C. The NPs showed enhanced antibiofilm efficacy against S. aureus at sub-minimum inhibitory concentrations. Additionally, the cytotoxicity of meropenem and honey-encapsulated Cs against the HEK-293 normal cell line was insignificant. Our findings suggested that meropenem and honey-Cs-NPs might be potential antibacterial and antibiofilm materials.

Bactericidal Permeability-Increasing Protein (BPI) Inhibits Mycobacterium tuberculosis Growth.

Bactericidal permeability-increasing protein (BPI) is a multifunctional cationic protein produced by neutrophils, eosinophils, fibroblasts, and macrophages with antibacterial anti-inflammatory properties. In the context of Gram-negative infection, BPI kills bacteria, neutralizes the endotoxic activity of lipopolysaccharides (LPSs), and, thus, avoids immune hyperactivation. Interestingly, BPI increases in patients with Gram-positive meningitis, interacts with lipopeptides and lipoteichoic acids of Gram-positive bacteria, and significantly enhances the immune response in peripheral blood mononuclear cells. We evaluated the antimycobacterial and immunoregulatory properties of BPI in human macrophages infected with Mycobacterium tuberculosis. Our results showed that recombinant BPI entered macrophages, significantly reduced the intracellular growth of M. tuberculosis, and inhibited the production of the proinflammatory cytokine tumor necrosis factor-alpha (TNF-α). Furthermore, BPI decreased bacterial growth directly in vitro. These data suggest that BPI has direct and indirect bactericidal effects inhibiting bacterial growth and potentiating the immune response in human macrophages and support that this new protein's broad-spectrum antibacterial activity has the potential for fighting tuberculosis.

Antimicrobial and Probiotic Potential of Lactobacilli Associated with Traditional Fermented Beverages.

Fermented foods have been recognized as a source of probiotic bacteria which can have a positive effect when administered to humans and animals. Discovering new probiotics in fermented food products poses a global economic and health importance. In this study, we investigated the antimicrobial and probiotic potential of lactobacilli isolated from fermented beverages produced traditionally by ethnic groups in Northeast India. Out of thirty Lactobacilli, fifteen exhibited strong antimicrobial activity against Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter aerogenes with significant anti-biofilm and anti-quorum sensing activity. These isolates also showed characteristics associated with probiotic properties, such as tolerance to low pH and bile salts, survival in the gastric tract, auto-aggregation, and hydrophobicity without exhibiting hemolysis formation or resistance to certain antibiotics. The isolates were identified using gram staining, biochemical tests, and 16S rDNA sequencing. They exhibited probiotic potential, broad-spectrum of antibacterial activity, promising anti-biofilm, anti-quorum sensing activity, non-hemolytic, and tolerance to acidic pH and bile salts. Overall, four specific Lactobacillus isolates, Lactiplantibacillus plantarum BRD3A and Lacticaseibacillus paracasei RB10OW from fermented rice-based beverage, and Lactiplantibacillus plantarum RB30Y and Lacticaseibacillus paracasei MP11A from traditional local curd demonstrated potent antimicrobial and probiotic properties. These findings suggest that these lactobacilli isolates from fermented beverages have the potential to be used as probiotics with therapeutic benefits, highlighting the importance of traditional fermented foods for promoting gut health and infectious disease management.

Natural product guvermectin inhibits guanosine 5′-monophosphate synthetase and confers broad-spectrum antibacterial activity

Bacterial diseases caused substantial yield losses worldwide, with the rise of antibiotic resistance, there is a critical need for alternative antibacterial compounds. Natural products (NPs) from microorganisms have emerged as promising candidates due to their potential as cost-effective and environmentally friendly bactericides. However, the precise mechanisms underlying the antibacterial activity of many NPs, including Guvermectin (GV), remain poorly understood. Here, we sought to explore how GV interacts with Guanosine 5′-monophosphate synthetase (GMPs), an enzyme crucial in bacterial guanine synthesis. We employed a combination of biochemical and genetic approaches, enzyme activity assays, site-directed mutagenesis, bio-layer interferometry, and molecular docking assays to assess GV's antibacterial activity and its mechanism targeting GMPs. The results showed that GV effectively inhibits GMPs, disrupting bacterial guanine synthesis. This was confirmed through drug-resistant assays and direct enzyme inhibition studies. Bio-layer interferometry assays demonstrated specific binding of GV to GMPs, with dependency on Xanthosine 5′-monophosphate. Site-directed mutagenesis identified key residues crucial for the GV-GMP interaction. This study elucidates the antibacterial mechanism of GV, highlighting its potential as a biocontrol agent in agriculture. These findings contribute to the development of novel antibacterial agents and underscore the importance of exploring natural products for agricultural disease management.

Characterization and Assessment of Native Lactic Acid Bacteria from Broiler Intestines for Potential Probiotic Properties.

Probiotics are the most promising alternative to antibiotics for improving animal production and controlling pathogenic infections, while strains derived from natural hosts are considered highly desirable due to their good adaptation to the gastrointestinal tract. The aim of this study was to screen Lactobacillus with broad-spectrum antibacterial activity from broilers fed an antibiotic-free diet and evaluate their potential as poultry probiotics. A total of 44 lactic acid bacteria (LAB) strains were isolated from the intestines of healthy broilers, among which 3 strains exhibited outstanding antimicrobial activity and were subsequently identified through 16S rRNA sequencing as Enterococcus faecium L8, Lactiplantibacillus plantarum L10, and Limosilactobacillus reuteri H11. These three isolates demonstrated potent bacteriostatic activity against Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, and Salmonella cholerae, with inhibition zones ranging from 15.67 ± 1.53 to 21.33 ± 0.58 mm. The selected LAB strains exhibited high tolerance to acid and bile salts, with L. reuteri H11 displaying the highest survival rate (ranging from 34.68% to 110.28%) after exposure to 0.3% (w/v) bile salts for 6 h or a low pH environment (pH 2, 2.5, and 3) for 3 h. Notably, L. reuteri H11 outperformed other strains in terms of hydrophobicity (84.31%), auto-aggregation (53.12%), and co-aggregation with E. coli ATCC 25922 (36.81%) and S. aureus ATCC 6538 (40.20%). In addition, the three LAB isolates were either fully or moderately susceptible to the tested antibiotics, except for strain L8, which resisted gentamycin and vancomycin. Consequently, these three LAB strains, especially L. reuteri H11, isolated from the intestines of broiler chickens, represent promising probiotic candidates that can be employed as feed additives to enhance production performance and control poultry pathogens.

Chitosan/starch based unoxidized tannic acid modified microparticles for rapid hemostasis with broad spectrum antibacterial activity

The development of a rapid hemostat through a facile method with co-existing antibacterial activity and minimum erythrocyte lysis property stands as a major requirement in the field of hemostasis. Herein, a series of novel microparticle hemostats were synthesized using chitosan, different hydrothermally-treated starches, and cross-linked with tannic acid (TA) simultaneously in an unoxidized environment via ionotropic gelation method. Hemostats' comparative functional properties, such as adjustable antibacterial and erythrocyte compatibility upon various starch additions were evaluated. The in vivo hemostatic study revealed that the developed hemostats for mouse liver laceration and rat tail amputation had clotting times (13 s and 38 s, respectively) and blood loss (51 mg and 62 mg, respectively) similar to those of Celox™. The erythrocyte adhesion test suggested that erythrocyte distortion can be lowered by modifying the antibacterial hemostats with different starches. The broad-spectrum antibacterial efficacy of the hemostats remained intact against S. aureus (>90 %), E. coli (>80 %), and P. mirabilis bacteria upon starch modification. They also demonstrated high hemocompatibility (<3 % hemolysis ratio), moderate cell viability (>81 %), in vivo biodegradation, and angiogenesis indicating adequate biocompatibility and wound healing. The developed hemostats hold significant promise to be employed as rapid hemostatic agents for preventing major bleeding and bacterial infection in emergencies.

Graphene oxide/ε-poly-L-lysine self-assembled functionalized coatings improve the biocompatibility and antibacterial properties of titanium implants.

The construction of an antibacterial biological coating on titanium surface plays an important role in the long-term stability of oral implant restoration. Graphene oxide (GO) has been widely studied because of its excellent antibacterial properties and osteogenic activity. However, striking a balance between its biological toxicity and antibacterial properties remains a significant challenge with GO. ε-poly-L-lysine (PLL) has broad-spectrum antibacterial activity and ultra-high safety performance. Using Layer-by-layer self-assembly technology (LBL), different layers of PLL/GO coatings and GO self-assembly coatings were assembled on the surface of titanium sheet. The materials were characterized using scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and contact angle test. The antibacterial properties of Porphyromonas gingivalis (P.g.) were analyzed through SEM, coated plate experiment, and inhibition zone experiment. CCK-8 was used to determine the cytotoxicity of the material to MC3T3 cells, and zebrafish larvae and embryos were used to determine the developmental toxicity and inflammatory effects of the material. The results show that the combined assembly of 20 layers of GO and PLL exhibits good antibacterial properties and no biological toxicity, suggesting a potential application for a titanium-based implant modification scheme.

Biotransformation characteristics of tetracycline by strain Serratia marcescens MSM2304 and its mechanism evaluation based on products analysis and genomics

Microbial biotransformation is a recommended and reliable method in face of formidable tetracycline (TC) with broad-spectrum antibacterial activity. Herein, comprehensive characteristics of a newfound strain and its molecular mechanism in process of TC bioremediation were involved in this study. Specifically, Serratia marcescens MSM2304 isolated from pig manure sludge grew well in presence of TC and achieved optimal removal efficiency of 61% under conditions of initial TC concentration of 10 mg/L, pH of 7.0, cell inoculation amount of 5%, and tryptone of 10 g/L as additional carbon. The pathways of biotransformation include EPS biosorption, cell surface biosorption and biodegradation, which enzymatic processes of biodegradation were occurred through TC adsorbed by biofilms was firstly broken down by extracellular enzymes and part of TC migrated towards biofilm interior and degraded by intracellular enzymes. Wherein extracellular polysaccharides in extracellular polymeric substances (EPS) from biofilm of strain MSM2304 mainly performed extracellular adsorption, and changes in position and intensity of CO, =CH and C–O–C/C–O of EPS possible further implied TC adsorption by it. Biodegradation accounting for 79.07% played a key role in TC biotransformation and could be fitted well by first-order model that manifesting rapid and thorough removal. Potential biodegradation pathway including demethylation, dihydroxylation, oxygenation, and ring opening possibly involved in TC disposal process of MSM2304, TC-degrading metabolites exhibited lower toxicity to indicator bacteria relative to parent TC. Whole genome sequencing as underlying molecular evidence revealed that TC resistance genes, dehydrogenases-encoding genes, monooxygenase-encoding genes, and methyltransferase-encoding genes of strain MSM2304 were positively related to TC biodegradation. Collectively, these results favored a theoretical evaluation for Serratia marcescens MSM2304 as a promising TC-control agent in environmental bioremediation processes.

Borneol-Modified Chitosan Coating with Antibacterial Properties via Layer-by-Layer Strategy

Chitosan exhibits remarkable broad-spectrum antibacterial activity, especially in acidic environments. However, its poor solubility in water and significantly decreased antibacterial performance after membrane formation greatly limit its extensive application. To address this issue, glycol chitosan-4-pyridylcarboxaldehydeborneol (GCBP) was synthesized by conjugating glycol chitosan (GC) with 4-pyridylcarboxaldehydeborneol ester (BP) through dynamic Schiff base bonds utilizing a layer-by-layer self-assembly strategy. When bacteria come into contact with the surface, the local acidic microenvironment triggers the cleavage of the Schiff base, resulting in the release of bactericidal BP and GC for combined sterilization. In vitro results demonstrated that the antibacterial properties of GCBP were positively related to the modification layers. The excellent antibacterial performance of the GCBP modification demonstrates not only great potential for clinical urinary catheters but also for broad antibacterial applications in the medical field.

Enhanced biodegradation of sulfamethoxazole by pyrogenic carbon derived from aquacultural waste sludge

Sulfamethoxazole (SMX) is a widely utilized antibiotic that exhibits a broad spectrum of antibacterial activity, but its inadvertent release into the environment poses a significant threat to human society. The inefficacy of SMX degradation in microbial pipelines constantly challenges the regulation of antibiotics, making it a pressing and compelling concern. Former research has demonstrated the enhancement of the waste sludge-derived materials on SMX biodegradation, but the impact of these materials on microbial behavior remains unclear. In this study, two pyrogenic carbon materials (FBC and RBC) were prepared from aquacultural waste sludge and its downstream river sediment, respectively, to collaborate with SMX degrading species, Alcaligenes sp., for highly efficient removal of SMX. The cells of Alcaligenes sp. successfully colonized onto the biocompatible surface of the materials, and this hybrid structure nearly doubled the SMX degradation efficiency of the group without the carbon materials. The transcriptome analysis revealed that the existence of carbon materials significantly upregulated the expression of SMX degrading-related genes, including metCF and paaCIK, which led to bond breaking and benzene ring breakdown for the degradation of sulfamethoxazole. This work provides new insights into the mechanisms and environmental significance of SMX degradation by microbial immobilization onto waste-derived carbon-rich materials.

Rational molecular design converting fascaplysin derivatives to potent broad-spectrum inhibitors against bacterial pathogens via targeting FtsZ

The filamentous temperature-sensitive mutant Z protein (FtsZ), a key player in bacterial cell division machinery, emerges as an attractive target to tackle the plight posed by the ever growing antibiotic resistance over the world. Therefore in this regard, agents with scaffold diversities and broad-spectrum antibacterial activity against Gram-positive and Gram-negative pathogens are highly needed. In this study, a new class of marine-derived fascaplysin derivatives has been designed and synthesized by Suzuki-Miyaura cross-coupling. Some compounds exhibited potent bactericidal activities against a panel of Gram-positive (MIC = 0.024–6.25 μg/mL) and Gram-negative (MIC = 1.56–12.5 μg/mL) bacteria including methicillin-resistant S. aureus (MRSA). They exerted their effects by dual action mechanism via disrupting the integrity of the bacterial cell membrane and targeting FtsZ protein. These compounds stimulated polymerization of FtsZ monomers and bundling of the polymers, and stabilized the resulting polymer network, thus leading to the dysfunction of FtsZ in cell division. In addition, these agents showed negligible hemolytic activity and low cytotoxicity to mammalian cells. The studies on docking and molecular dynamics simulations suggest that these inhibitors bind to the hydrophilic inter-domain cleft of FtsZ protein and the insights obtained in this study would facilitate the development of potential drugs with broad-spectrum bioactivities.

A magnetic nanozyme platform for bacterial colorimetric detection and chemodynamic/photothermal synergistic antibacterial therapy.

Rapid, convenient, and sensitive detection of bacteria and development of novel antibacterial materials are conducive to accurate treatment of bacterial infection and reducing the generation of drug-resistant bacteria caused by overuse of antibiotics. A dual-function magnetic nanozyme, Fc-MBL@rGO@Fe3O4, has been constructed with broad-spectrum bacterial affinity and good peroxidase-like activity. Detection signal amplification was realized in the presence of 3,3',5,5'-tetramethylbenzidine (TMB) with a detection limit of 26 CFU/mL. In addition, the excellent photothermal properties of Fc-MBL@rGO@Fe3O4 could realize synergistic chemodynamic/photothermal antibacterial therapy. Furthermore, the good bacterial affinity of Fc-MBL@rGO@Fe3O4 enhances the accurate and rapid attack of hydroxyl radical (·OH) on the bacterial membrane and achieves efficient sterilization (100%) at low concentration (40µg/mL) and mild temperature (47℃). Notably, Fc-MBL@rGO@Fe3O4 has a broad spectrum of antibacterial activity against Gram-negative, Gram-positive, and drug-resistant bacteria. The magnetic nanoplatform integrating detection-sterilization not only meets the need for highly sensitive and accurate detection in different scenarios, but can realize low power density NIR-II light-responsive chemodynamic/photothermal antibacterial therapy, which has broad application prospects.

Synthesis and characterization of hydroxy propyl methyl Cellulose/Copper nanobiocomposites for antibacterial and antioxidant smart materials

The synthesis of hydroxy propyl methyl cellulose (HPMC)/copper nanobiocomposites adopting a microwave treatment. In this study, HPMC and copper nitrate at various concentration were mixed and subjected to varying microwave treatment times (10, 20, 30, 40, 50 and 60 s). UV–Vis spectroscopy was employed to analyse the physicochemical characteristics of HPMC/copper nanobiocomposites, with a maximal absorbance at 380 nm, indicating the formation of copper nanoparticles within the HPMC matrix. The interaction between copper nanoparticles and HPMC was further confirmed through FT-IR analysis. The SEM analysis displayed microporous structures ranging from 5 to 14 µm in diameter, with an average pore size of 7.0 ± 2.0 nm. The compositional analysis was done with EDS mapping. TEM analysis revealed spherical shaped copper nanoparticles with an average particle size about 2.5 nm in HPMC matrix. Remarkably, these nanobiocomposites exhibited a broad-spectrum antibacterial activity, displaying minimal inhibitory concentrations against both Gram-negative and Gram-positive bacterium. Significantly, the assessment of antibacterial activity in HPMC/copper nanobiocomposites demonstrated their efficacy against both Escherichia coli and Staphylococcus aureus. In addition to the antioxidant property, the antibacterial properties holds significant implications for their potential applications of HPMC/ copper nanobiocomposites in the fields of food packaging and biomedicine.

Antibacterial mechanism and enhancement of antibacterial activity under visible light in Er3+-doped BiOBr

The introduction of oxygen defects in semiconductor electronic structures is considered to be an effective strategy to improve their photocatalytic activity. In this work, rare-earth Er3+−doped BiOBr (Er/BiOBr) with oxygen-rich vacancies (OVs) was prepared via simple hydrothermal method. Compared with pure BiOBr, Er/BiOBr has a narrower band gap and more abundant OVs, which together improve the separation efficiency of photogenerated carriers. The introduction of Er not only creates impurity states between conduction band (CB) and valence band (VB), but also produces more OVs as electron traps. Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) were used as evaluation systems for these materials with different Er3+ doping contents. The results showed that under the combined action of ·O2− and H2O2, 2.0% EBB samples with Er3+ doping content of BiOBr showed the best broad-spectrum antibacterial activity, and E. coli and S. aureus were completely inactivated at 0.03 mg ml−1 and 0.05 mg ml−1 concentrations. The surface and interfacial structures of Er/BiOBr samples were studied by XRD, brunauer-emmet-teller method, SEM, TEM and EDX. OVs and photogenerated carrier separation in Er/BiOBr were determined by ESR, PL and photochemical detection methods. More importantly, through the detection of lipid peroxidation and bacterial respiratory chain dehydrogenase activities, the internal and external processes of ROS on bacterial inactivation were determined, and the photocatalytic antibacterial mechanism was summarized. This study for the antimicrobial properties of rare earth ions doped improve photocatalytic materials provides a new train of thought.