Potential Antibacterial Mechanism Research Articles

Development of Nanomaterials-Based Agents for Selective Antibacterial Activity.

Bacterial infections continue to threaten public health due to limitations in rapid and accurate diagnostic techniques. While broad-spectrum antibiotics offer empirical treatment, their overuse has fuelled the emergence of antimicrobial resistance (AMR) pathogens, posing a critical global public health challenge. In this critical scenario, nanomaterial-based antibacterial agents emerge as a promising solution to combat bacteria and inhibit their proliferation. However, selective elimination of pathogenic bacteria is paramount. This review highlights recent advancements in developing nanomaterials for selective antibacterial activity. We categorize these agents based on their mode of action, exploring how they selectively interact with bacteria and their potential antibacterial mechanisms. This review offers crucial insights for researchers exploring the potential of nanotechnology to address the growing threat of AMR.

Eco-Friendly Synthesis of ZnO Nanoparticles for Quinoline Dye Photodegradation and Antibacterial Applications Using Advanced Machine Learning Models

Community drinking water sources are increasingly contaminated by various point and non-point sources, with emerging organic contaminants and microbial strains posing health risks and disrupting ecosystems. This study explores the use of zinc oxide nanoparticles (ZnO-NPs) as a non-specific agent to address groundwater contamination and combat microbial resistance effectively. The ZnO-NPs were synthesized via a green chemistry approach, employing a sol-gel method with lemon peel aqueous extract. The catalyst was characterized using techniques including XRD, ATR-FTIR, SEM-EDAX, UV-DRS, BET, and Raman spectroscopy. ZnO-NPs were then tested for photodegradation of quinoline yellow dye (QY) under sunlight irradiation, as well as for their antibacterial and antioxidant properties. The ZnO-NP photocatalyst showed significant photoactivity, attributed to effective separation of photogenerated charge carriers. The efficiency of sunlight dye photodegradation was influenced by catalyst dosage (0.1–0.6 mg L−1), pH (3–11), and initial QY concentration (10–50 mg L−1). The study developed a first-order kinetic model for ZnO-NPs using the Langmuir–Hinshelwood equation, yielding kinetic constants of equilibrium adsorption and photodegradation of Kc = 6.632 × 10−2 L mg−1 and kH = 7.104 × 10−2 mg L−1 min−1, respectively. The results showed that ZnO-NPs were effective against Gram-positive bacterial strains and showed moderate antioxidant activity, suggesting their potential in wastewater disinfection to achieve sustainable development goals. A potential antibacterial mechanism of ZnO-NPs involving interactions with microbial cells is proposed. Additionally, Gaussian Process Regression (GPR) combined with an improved Lévy flight distribution (FDB-LFD) algorithm was used to model QY photodegradation by ZnO-NPs. The ARD-Exponential kernel function provided high accuracy, validated through residue analysis. Finally, an innovative MATLAB-based application was developed to integrate the GPR_FDB-LFD model and FDB-LFD algorithm, streamlining optimization for precise photodegradation rate predictions. The results obtained in this study show that the GPR and FDB-LFD approaches offer efficient and cost-effective methods for predicting dye photodegradation, saving both time and resources.

Improved Anti-Oxidant and Anti-Bacterial Capacities of Skim Milk Fermented by Lactobacillus plantarum.

Milk, on account of its abundant protein content, is recognized as a vital source of bioactive substances. In this study, the bioactive ingredients in milk were obtained by a combination of protease hydrolysis and fermentation with Lactobacillus plantarum. The compositions of protease hydrolysate (PM) and fermentation supernatant (FM) were determined, and their anti-oxidant and anti-bacterial activities were evaluated. Using LC-MS/MS, the molecular weights and sequences of the peptides were characterized, among which a total of 25 bioactive peptides were identified. The DPPH radical scavenging results demonstrated that FM exhibited an enhanced anti-oxidant capacity compared to PM. The bacterial survival rate results revealed that FM had a remarkable anti-bacterial ability compared to PM. Additionally, the anti-bacterial component and potential anti-bacterial mechanisms were determined. The results of cytoplasmic membrane depolarization, cell membrane permeability, and morphological observation indicated that FM could interact with bacterial membranes to achieve its anti-bacterial effect. These findings suggested that FM, as a bioactive substance of natural origin, holds potential applications in the functional food, pharmaceutical, and cosmetic industries.

Biogenic amine tryptamine in human vaginal probiotic isolates mediates matrix inhibition and thwarts uropathogenic E. coli biofilm

Probiotics offer a promising prophylactic approach against various pathogens and represent an alternative strategy to combat biofilm-related infections. In this study, we isolated vaginal commensal microbiota from 54 healthy Indian women to investigate their probiotic traits. We primarily explored the ability of cell-free supernatant (CFS) from Lactobacilli to prevent Uropathogenic Escherichia coli (UPEC) colonization and biofilm formation. Our findings revealed that CFS effectively reduced UPEC’s swimming and swarming motility, decreased cell surface hydrophobicity, and hindered matrix production by downregulating specific genes (fimA, fimH, papG, and csgA). Subsequent GC–MS analysis identified Tryptamine, a monoamine compound, as the potent bioactive substance from Lactobacilli CFS, inhibiting UPEC biofilms with an MBIC of 4 µg/ml and an MBEC of 8 µg/ml. Tryptamine induced significant changes in E. coli colony biofilm morphology, transitioning from the Red, Dry, and Rough (RDAR) to the Smooth and White phenotype, indicating reduced extracellular matrix production. Biofilm time-kill assays demonstrated a four-log reduction in UPEC viability when treated with Tryptamine, highlighting its potent antibacterial properties, comparable to CFS treatment. Biofilm ROS assays indicated a significant elevation in ROS generation within UPEC biofilms, suggesting a potential antibacterial mechanism. Gene expression studies with Tryptamine-treated samples showed a reduction in expression of curli gene (csgA), consistent with CFS treatment. This study underscores the potential of Tryptamine from probiotic Lactobacilli CFS as a promising antibiofilm agent against UPEC biofilms.

Correction to: Unveiling the potential antibacterial mechanism of Melaleuca cajuputi leaf extract by cell morphology studies and molecular docking analysis

Correction to: Unveiling the potential antibacterial mechanism of Melaleuca cajuputi leaf extract by cell morphology studies and molecular docking analysis

Preparation of h-BN@ZnO composite epoxy coating for improve durability and antibacterial properties of concrete

Microbiological corrosion is a significant concern because it causes the deterioration of concrete structures in marine and sewage environments. Based on a hybrid antibacterial strategy, a novel antibacterial coating with h-BN@ZnO as filler was successfully prepared to improve the durability and antibacterial properties of concrete structures in harsh environmental conditions. The properties of h-BN@ZnO were characterized, with a focus on investigating its potential antibacterial mechanisms. Furthermore, three types of composite coatings were prepared by incorporating ZnO, h-BN and h-BN@ZnO as fillers. The microstructure, thermal stability, breathability and antibacterial performance of these composite coatings were thoroughly characterized. Immersion test and pull-off test were conducted to evaluate the effectiveness of these composite coatings in improving the durability of concrete structures. The results demonstrated that h-BN@ZnO exhibited excellent antibacterial activity, primarily attributed to the presence of ZnO. Moreover, the unique structure of ZnO on h-BN sheets contributed to enhancing the dispersion stability of h-BN@ZnO. As filler within the coating, h-BN@ZnO demonstrated significant improvements in antibacterial performance and barrier properties. With 2 wt% h-BN@ZnO, the composite coating achieved an impressive 99 % anti-adhesion rate against Escherichia coli and Staphylococcus aureus. In comparison to pure coatings, this coating demonstrated a 50 % reduction in the penetration depth of sulfate ions. It was also observed that a high content of h-BN@ZnO led to further improvements in the barrier properties and antibacterial adhesion rates of the coating. These findings contribute to understanding the potential of incorporating h-BN@ZnO filler into coatings to improve the durability of concrete structures.

Unveiling the potential antibacterial mechanism of Melaleuca cajuputi leaf extract by cell morphology studies and molecular docking analysis

Unveiling the potential antibacterial mechanism of Melaleuca cajuputi leaf extract by cell morphology studies and molecular docking analysis

In vitro anti-Helicobacter pylori activity and antivirulence activity of cetylpyridinium chloride.

The primary treatment method for eradicating Helicobacter pylori (H. pylori) infection involves the use of antibiotic-based therapies. Due to the growing antibiotic resistance of H. pylori, there has been a surge of interest in exploring alternative therapies. Cetylpyridinium chloride (CPC) is a water-soluble and nonvolatile quaternary ammonium compound with exceptional broad-spectrum antibacterial properties. To date, there is no documented or described specific antibacterial action of CPC against H. pylori. Therefore, this study aimed to explore the in vitro activity of CPC against H. pylori and its potential antibacterial mechanism. CPC exhibited significant in vitro activity against H. pylori, with MICs ranging from 0.16 to 0.62 μg/mL and MBCs ranging from 0.31 to 1.24 μg/mL. CPC could result in morphological and physiological modifications in H. pylori, leading to the suppression of virulence and adherence genes expression, including flaA, flaB, babB, alpA, alpB, ureE, and ureF, and inhibition of urease activity. CPC has demonstrated in vitro activity against H. pylori by inhibiting its growth, inducing damage to the bacterial structure, reducing virulence and adherence factors expression, and inhibiting urease activity.

Selected Australian Terminalia Species Extracts Inhibit β-Lactam Drug-Resistant Bacteria Growth and Potentiate the Activity of Conventional Antibiotics: Bioactivities and Phytochemistry.

Terminalia ferdinandiana Exell, Terminalia grandiflora Benth., Terminalia microcarpa Decne., and Terminalia muelleri Benth. (family: Combretaceae) belong to the genus Terminalia. Plants of this genus have been extensively used as traditional medicines to treat a variety of illnesses, including pathogen infections. However, we were unable to find any studies that have investigated the antibacterial activity of T. microcarpa. Similarly, whilst some preliminary studies have examined the antimicrobial properties of T. muelleri and T. grandiflora, they did not test the extracts against antibiotic-resistant pathogens. This study screens the antimicrobial activity of T. grandiflora, T. microcarpa, and T. muelleri and compares it to that of T. ferdinandiana extracts prepared from both the fruit and leaves against a range of pathogens, including multi-antibiotic-resistant strains. Solvents with varying polarities were used to extract different phytochemical constituents from the leaves of T. grandiflora, T. microcarpa, and T. muelleri and from the fruit and leaves of T. ferdinandiana. The aqueous and methanolic extracts each displayed significant antimicrobial activity when tested against the bacterial pathogens, including against the multidrug-resistant strains. When these extracts were tested in combination with selected antibiotics, some extracts potentiated the antimicrobial activity. This study identifies twelve synergistic, fifty-eight additive, and sixty non-interactive combinations, as well as thirty antagonistic effects. The extracts were evaluated for toxicity using the Artemia franciscana nauplii lethality assay (ALA) and were each classified as non-toxic, with the exception of the methanolic and aqueous T. ferdinandiana fruit extracts and the aqueous and ethyl acetate T. ferdinandiana leaf extracts. Metabolomic analysis using liquid chromatography-mass spectrometry (LC-MS) highlighted several flavonoids and tannins that may contribute to the antimicrobial activities reported herein. The potential antibacterial mechanism(s) of the T. ferdinandiana extracts are discussed in this study.

Synthesis, structure, theoretical calculation and antibacterial property of two novel Zn(II)/Ni(II) compounds based on 3, 5-dichlorosalicylaldehyde thiocarbamide ligand

Two new compounds namely [Zn(L1)phen]31 and Ni(L1)phen(MeOH) 2 (L1 = 3, 5-dichlorosalicylaldehyde thiosemicarbazone) were synthesized by the slow evaporation method at room temperature. The structure of ligand L1 was determined using 1H NMR and 13C NMR spectra. X-ray single crystal diffraction analysis revealed that compounds 1–2 can form 3D supramolecular network structures through π···π stacking and hydrogen bonding interactions. The DFT calculation shows that the coordination of ligand and metal is in good agreement with the experimental results. Hirshfeld surface analysis revealed that H…H and Cl…H interactions were the predominant interactions in compounds 1–2. Energy framework analysis indicated that dispersion energy played a dominant role in the energy composition of compounds 1–2. The inhibitory effects of compounds 1–2 against Escherichia coli (E. coli) and Methicillin-resistant Staphylococcus aureus (MRSA) were tested using the paper disk diffusion method (1: E. coli: 18 mm, MRSA: 17 mm, 2: E. coli: 15 mm, MRSA: 16 mm). Ion releasing experiments were conducted to assess the ion release capacity of compounds 1–2 (Zn2+, 4 days, 38.33 µg/mL; Ni2+, 4 days, 29.12 µg/mL). Molecular docking demonstrated the interaction modes of compounds 1–2 with UDP-N-acetylenolpyruvoylglucosamine reductase (MurB) and dihydrofolate reductase (DHFR) in bacteria, involving hydrophobic, stacking, hydrogen bonding and halogen bonding interactions. The generation of reactive oxygen species (ROS) in bacteria under the presence of compounds 1–2 were evaluated using a fluorescent dye known as dichlorodihydrofluorescein diacetate (DCFH-DA). Potential antibacterial mechanisms of compounds 1–2 were proposed.

Formulation of novel bioactive gelatin inspired by cinnamaldehyde for combating multi-drug resistant bacteria: Characterization, molecular docking, pharmacokinetic analyses, and in vitro assessments

This study set out to formulate antibacterial and antioxidant gelatin boosted by cinnamaldehyde for combating multi-drug resistant bacteria previously obtained from chronic wounds. Towards this end, gelatin amine groups were conjugated with carbonyl groups of cinnamaldehyde, producing cinnamyl-gelatin Schiff bases. The physicochemical attributes of cinnamyl-gelatin Schiff bases were probed concerning alterations in chemical structures and microstructures compared to native gelatin. Besides, cinnamyl-gelatin Schiff bases exhibited higher thermal stability than gelatin, with a diminishing in solubility due to increases in hydrophobicity features. Interestingly, cinnamyl-gelatin derivatives exerted antibacterial activities versus multi-drug resistant Gram-negative and Gram-positive bacteria, showing maximum growth inhibition at the highest concentration of cinnamaldehyde incorporated into gelatin. The scavenging activities of gelatin against DPPH and ABTS•+ were promoted in cinnamyl-gelatin derivatives from 11.93 ± 0.6 % to 49.9 ± 2.5 % and 12.54 ± 0.63 % to 49.9 ± 3.12 %, respectively. Remarkably, cinnamyl-gelatin derivatives induced the proliferation of fibroblast cells, implying their prospective applications in tissue engineering. Molecular docking and pharmacokinetic investigations disclosed the potential antibacterial mechanisms of cinnamyl-gelatin derivatives alongside their biopharmaceutical applications. Altogether, these findings suggest that cinnamyl-gelatin derivatives could be utilized to tailor antibacterial-free antibiotics and antioxidant wound dressings against virulent bacteria to promote chronic wound recovery.

Antibacterial and biofilm prevention metabolites from Acanthophora spicifera

Abstract Acanthophora spicifera harbors a diverse array of secondary metabolites with therapeutic potential. The aim of this study is to isolate and characterize secondary metabolites from A. spicifera and then evaluate the antiproliferation, antibacterial, and biofilm prevention properties, followed by an analysis of molecular docking experiments. By employing chromatographic analysis and NMR spectroscopy, the isolated compounds were, the known flavonol, 8-hydroxyquercetagetin (1), three recognized steroids cholest-4-ene-3,6-dione (2), cholest-5-en-3β-ol (3), and 5α-cholestane-3,6-dione (4), and 2-bromohexadecanoic acid (5). These compounds exhibited antimicrobial effects against various Gram-negative and Gram-positive bacteria with inhibition zones ranging from 6.5 ± 0.2 to 17.2 ± 0.12 mm and 7.0 ± 0.4 to 15.3 ± 0.60 mm, respectively. Compounds 1 and 2 inhibited biofilm formation in P. aeruginosa and S. aureus. Compounds 1–4 demonstrated binding affinity values between −7.5 and −9.4 kcal/mol to protein 1A0G. These binding affinity values were akin to that of amoxicillin, implying that one potential antibacterial mechanism of action of these compounds may involve the inhibition of bacterial cell wall synthesis. All compounds showed no toxicity against Artemia salina and weak activity against Lymphoma and Lewis lung carcinoma cell lines with LD50 > 100 μg/mL.

ITRAQ-based quantitative proteomic analysis of the antibacterial mechanism of silver nanoparticles against multidrug-resistant Streptococcus suis.

The increase in antibiotic resistance of bacteria has become a major concern in clinical treatment. Silver nanoparticles (AgNPs) have significant antibacterial effects against Streptococcus suis. Therefore, this study aimed to investigate the antibacterial activity and mechanism of action of AgNPs against multidrug-resistant S. suis. The effect of AgNPs on the morphology of multidrug-resistant S. suis was observed using scanning electron microscopy (SEM). Differentially expressed proteins were analyzed by iTRAQ quantitative proteomics, and the production of reactive oxygen species (ROS) was assayed by H2DCF-DA staining. SEM showed that AgNPs disrupted the normal morphology of multidrug-resistant S. suis and the integrity of the biofilm structure. Quantitative proteomic analysis revealed that a large number of cell wall synthesis-related proteins, such as penicillin-binding protein and some cell cycle proteins, such as the cell division protein FtsZ and chromosomal replication initiator protein DnaA, were downregulated after treatment with 25 μg/mL AgNPs. Significant changes were also observed in the expression of the antioxidant enzymes glutathione reductase, alkyl hydroperoxides-like protein, α/β superfamily hydrolases/acyltransferases, and glutathione disulfide reductases. ROS production in S. suis positively correlated with AgNP concentration. The potential antibacterial mechanism of AgNPs may involve disrupting the normal morphology of bacteria by inhibiting the synthesis of cell wall peptidoglycans and inhibiting the growth of bacteria by inhibiting the cell division protein FtsZ and Chromosomal replication initiator protein DnaA. High oxidative stress may be a significant cause of bacterial death. The potential mechanism by which AgNPs inhibit S. suis biofilm formation may involve affecting bacterial adhesion and interfering with the quorum sensing system.

Development and application of in silico models to design new antibacterial 5-amino-4-cyano-1,3-oxazoles against colistin-resistant E. coli strains

Here we describe the results of QSAR analysis based on artificial neural networks, synthesis, activity evaluation and molecular docking of a number of 1,3-oxazole derivatives as anti-E. coli antibacterials. All developed QSAR models showed excellent statistics on training (with determination coefficient q2 as 0.76 ± 0.01) and test samples (with q2 as 0.78 ± 0.01). The models were successfully used to identify nine novel 5-amino-4-cyano-1,3-oxazoles with potential anti-E. coli activity. All nine 1,3-oxazoles with predicted high antibacterial potential showed different levels of anti- E. coli in vitro activity. 5-amino-4-cyano-1,3-oxazoles 1 and 3 showed the highest antibacterial activity on average from 17 to 27 mm against MDR, hemolytic MDR and ATCC 25922 E. coli colistin-resistant strains, respectively. The comparative docking analysis demonstrated a possible mechanism of the antibacterial action of the studied 1, 3-oxazoles 1 and 3 through inhibition of E. coli enoyl-ACP reductase (ENR) involved in the biosynthesis of bacterial fatty acids. The localization type is shown of 5-amino-4-cyano-1,3-oxazoles 1 and 3 into the E. coli ENR active site with estimated binding energy from − 10.1 to − 9.5 kcal/mol and hydrogen bonds formation with key amino acids similar to Triclosan. These facts confirm the validity of the hypothesis put forward about the potential antibacterial mechanism of 5-amino-4- cyano-1,3-oxazoles.

Smartphone-triggered targeted inactivation of MRSA under SERS monitoring

Silver nanoparticles-based multifunctional agents show tremendous potential for simultaneous imaging and against the methicillin-resistant Staphylococcus aureus (MRSA)-induced superficial infection. However, it is still a challenge to achieve a balance between high precision, high antibacterial efficiency, and biocompatibility. Herein, we present a 4-mercaptophenylboronic acid (4-MPBA)-modified Ag2CO3/Ag2O nano-heterojunctions (AgH@M) that can recognize single MRSA cell by surface-enhanced Raman scattering (SERS) and effectively eradicate MRSA under smartphone irradiation. Moreover, the 4-MPBA molecule acts as triple identities for MRSA targeted binding, SERS tag, and inhibition of excessive release of toxic silver ions for the Raman Imaging guided bacterial treatment. AgH@M simultaneously targeted binding on the surface of bacteria and made full use of the released limited Ag+ into the MRSA, thereby reducing the toxicity to mammalian cells. In addition, the potential antibacterial mechanism involves ROS production from photocatalytic behavior, interference with functional genes of quorum sensing, virulence, biofilm, and ATP-binding cassette transporter. Also, the AgH@M can monitor the residual bacteria in MRSA-infected wounds and keratitis animal models in real-time for at least 7 days by SERS and accomplishes a satisfactory therapeutic effect. This work may provide promising visualized heterojunctions for the targeted eradication of MRSA with a portable light source.

Black Phosphorus-Based ZnO-Ag Nanocomposite for Antibacterial Activity against Tigecycline-Resistant Acinetobacter baumannii

Acinetobacter baumannii is a critically hard-to-treat gram-negative pathogen responsible for a range of infectious diseases. Tigecycline is a last-resort antibiotic for A. baumannii infection; however, tigecycline-resistant (TIG-R) A. baumannii has been increasingly reported. Therefore, new strategies must be developed to treat these detrimental infections. Nanoantibiotics composed of two-dimensional (2D) black phosphorus (BP) and its derived nanocomposites have emerged as excellent alternatives to current antibiotics. However, the development of unique materials to target specific pathogens is challenging. Here, we report the preparation of a BP-based ZnO-Ag (ZPBA) nanocomposite. A low-temperature solution synthesis method was used to prepare ZnO and Ag nanoparticles immobilized on BP nanosheets. X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy were used to characterize the ZPBA nanocomposite. The antibacterial activity of ZPBA nanocomposite was assessed by determining its minimum inhibitory concentration against type (ATCC 19606, ATCC 15150) and TIG-R (ATCC 19606-R) A. baumannii strains. From the assays, ZPBA showed superior activity against TIG-R A. baumannii strain with MIC of 12.5 µg·mL−1 compared to all other prepared samples. Finally, the combination of bacterial membrane disruption and ROS generation was demonstrated to be a potential antibacterial mechanism of ZPBA. Our results show that ZPBA could be a potential nanoantibiotic platform for eradicating TIG-R A. baumannii.

Efficient titanium surface modified using bifunctional chimeric peptides to prevent biofilm formation by multiple microorganisms.

It is still a challenge to prevent the formation of bacterial biofilms on the surfaces of oral implants. A chemical peptide with binding and antibacterial properties may be a promising agent if used to modify titanium (Ti) surfaces to inhibit biofilm formation. In this study, peptides were designed by linking the antimicrobial sequence derived from human β-defensin-3 (hBD-3) to the Ti-binding peptide-1 (TBP-1) sequence by using a triple glycine (G) linker. The antimicrobial activity and biocompatibility characteristics of the chemical-peptide-modified Ti surface were then evaluated and the potential antibacterial mechanism was investigated. This study demonstrated that the chemical-peptide-modified surface exhibited satisfactory bactericidal activities against Streptococcus gordonii, Fusobacterium nucleatum, and Porphyromonas gingivalis. In addition to its potent bacteria-killing efficacy, the surface-immobilised chemical peptide also demonstrated excellent biocompatibility to L929 cells. Moreover, the disruption of the integrity of the bacterial membrane partially revealed the antibacterial mechanism of the peptide. This study demonstrated the potential of chemical-peptide-modified Ti surfaces for preventing the occurrence of peri-implant diseases, thereby providing a promising approach to improving the survival rate of oral implants.

In Vitro and In Silico Studies of Antimicrobial Saponins: A Review

Antibiotics are important drugs for the treatment of microbial infections and related diseases. However, due to the abuse of antibiotics, drug resistance has become a serious and urgent problem. The development of new antibiotics is a crucial area of research, and natural products are one of the main sources of novel antibiotics. Among various potential natural antimicrobial products, saponins attracted much attention due to their excellent and broad-spectrum antimicrobial properties. Although there are several reviews on antibacterial saponins, this review is the first to highlight the potential antibacterial mechanisms of saponins from both experimental and molecular simulation perspectives to provide a comprehensive panorama of the field. This review presents the current progress in the development and repurposing of natural-product antibiotics. The focus is centered on antimicrobial saponins discovered in recent years as well as the synergistic effect of some saponins with traditional antibiotics. This review presents experimental and simulation studies in this field to provide a multiscale overview of the antimicrobial mechanisms of saponins and potential directions for future research.

Synthesis and Characteristics of a Fish Scale-Based Biochar–Nanosilver Antibacterial Material

Microbial contamination has caused various diseases via pathogenic bacteria, endangering people’s lives every day. Recently, increasing attention has been paid to the exploration of new and effective antibacterial materials. In this paper, we attempted to synthesize a fish scale charcoal nanosilver antibacterial composite using waste fish scale as a carbon substrate. X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetry-differential scanning calorimetry, and scanning electron microscopy showed that the structure of the nanosilver fish scale material formed and the nanosilver particles formed account for 72.1% of the silver element. Its antibacterial ability against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa was examined using the plate counting method and inhibition zones; the maximum inhibition zone was 32 mm. The antibacterial rate could reach >99.9%, indicating that this prepared material had excellent antibacterial activity. After 20 batches of bacteriostasis, the bacteriostasis rate was more than 90%, indicating that the fish scale/silver composite had sustained antibacterial ability and excellent antibacterial reusability. Finally, potential antibacterial mechanism was proposed. Overall, the fish scale/silver composite has a good application prospect and a wide range of applications in the handling of microbial pollution in the future.

Transcriptomic analyses reveal the potential antibacterial mechanism of citral against Staphylococcus aureus.

The emergence of multi-drug resistant Staphylococcus aureus (S. aureus) has posed a challenging clinical problem for treating its infection. The development of novel or new antibacterial agents becomes one of the useful methods to solve this problem, and has received more attention over the past decade. Citral is reported to have antibacterial activity against S. aureus, but its mechanism is yet entirely clear. To reveal the antibacterial mechanism of citral against S. aureus, comparative transcriptomic analysis was carried out to analyze the gene expression differences between the citral-treated and untreated groups. The changes of protein, adenosine triphosphate (ATP) and reactive oxygen species (ROS) content in S. aureus caused by citral were also examined. Six hundred and fifty-nine differentially expressed genes were obtained according to the comparative transcriptomic analysis, including 287 up-regulated genes and 372 down-regulated genes. The oxidoreductase activity and fatty acid degradation pathway were enriched in up-regulated genes, and ribosome and S. aureus infection pathway were enriched in down-regulated genes. Meanwhile, physiological trials revealed a decline in ATP and protein levels, but an increase in ROS content within the citral-treated group. Thus, it can be inferred that the antibacterial effects of citral against S. aureus were likely due to its ability to decrease ATP content by down-regulating ATP synthase genes (atpD and atpG), reduce protein content, induce cell membrane and cell wall damages, accumulate ROS, and down-regulate virulence factor genes to reduce pathogenicity. These findings revealed the antibacterial mechanism of citral was likely a type of multi-target mode that affected multiple molecular processes in S. aureus, which lays the groundwork for further exploitation of citral as a therapeutic candidate against S. aureus infections.