Inhibition of Biofilm Formation of Foodborne Staphylococcus aureus by the Citrus Flavonoid Naringenin

Sinensetin interferes with Staphylococcus aureus infections by targeting staphylocoagulase and improves infection survival rates in mouse model of pneumonia

AIMS

Coagulase (Coa), a crucial virulence factor of Staphylococcus aureus (S. aureus), is considered a vital target for anti-virulence strategies. The research aimed to discover a natural compound capable of inhibiting S. aureus infection by targeting the virulence factor Coa.

METHODS AND RESULTS

The study showed that sinensetin at a concentration of 128 μg mL-1 effectively inhibited both Coa-induced coagulation and biofilm formation in S. aureus. However, western blot results indicated that sinensetin did not impact the expression of Coa protein, suggesting that sinensetin may directly target Coa to counteract the virulence of S. aureus. Thermal shift assay results demonstrated that sinensetin enhanced the thermal stability of Coa, supporting the theory of direct binding. Molecular docking and point mutation experiments identified two key binding sites for sinensetin to Coa as R73A-Coa and R204A-Coa. In vivo studies on mice revealed that sinensetin not only reduced lung tissue damage caused by S. aureus infection, but also decreased inflammatory factors in the lung lavage fluid. Furthermore, combining sinensetin with oxacillin improved the survival rates of the Galleria mellonella and mice.

CONCLUSIONS

Sinensetin is a promising natural compound that acts as a direct inhibitor of Coa against S. aureus infections.

An injectable hydrogel based on sodium alginate and gelatin treats bacterial keratitis through multimodal antibacterial strategy

Bacterial keratitis is among the most prevalent causes of blindness. Currently, the abuse of antibiotics in clinical settings not only lacks bactericidal effects but also readily induces bacterial resistance, making the clinical treatment of bacterial keratitis a significant challenge. In this study, we present an injectable hydrogel (GS-PNH-FF@CuS/MnS) containing self-assembled diphenylalanine dipeptide (FF) and CuS/MnS nanocomposites (CuS/MnS NCs) that destroy bacterial cell walls through a synergistic combination of mild photothermal therapy (PTT), chemodynamic therapy (CDT), ion release chemotherapy, and self-assembled dipeptide contact, thereby eliminating Pseudomonas aeruginosa. Under 808 nm laser irradiation, the bactericidal efficiency of GS-PNH-FF@CuS/MnS hydrogel against P. aeruginosa in vitro reach up to 96.97 %. Furthermore, GS-PNH-FF@CuS/MnS hydrogel is applied topically to kill bacteria, reduce inflammation, and promote wound healing. Hematoxylin-eosin (H&E) staining, Masson staining, immunohistochemistry and immunofluorescence staining are used to evaluate the therapeutic effect on infected rabbit cornea models in vivo. The GS-PNH-FF@CuS/MnS demonstrate good biocompatibility with human corneal epithelial cells and exhibit no obvious eyes side effects. In conclusion, the GS-PNH-FF@CuS/MnS hydrogel in this study provides an effective and safe treatment strategy for bacterial keratitis through a multimodal approach.

Antibiofilm and Antivirulence Potentials of 3,2'-Dihydroxyflavone against Staphylococcus aureus

Staphylococcus aureus, particularly drug-resistant strains, poses significant challenges in healthcare due to its ability to form biofilms, which confer increased resistance to antibiotics and immune responses. Building on previous knowledge that several flavonoids exhibit antibiofilm activity, this study sought to identify a novel flavonoid capable of effectively inhibiting biofilm formation and virulence factor production in S. aureus strains including MRSA. Among the 19 flavonoid-like compounds tested, 3,2'-dihydroxyflavone (3,2'-DHF) was identified for the first time as inhibiting biofilm formation and virulence factors in S. aureus with an MIC 75 µg/mL. The antibiofilm activity was further confirmed by microscopic methods. Notably, 3,2'-DHF at 5 µg/mL was effective in inhibiting both mono- and polymicrobial biofilms involving S. aureus and Candida albicans, a common co-pathogen. 3,2'-DHF reduces hemolytic activity, slime production, and the expression of key virulence factors such as hemolysin gene hla and nuclease gene nuc1 in S. aureus. These findings highlight the potential of 3,2'-DHF as a novel antibiofilm and antivirulence agent against both bacterial and fungal biofilms, offering a promising alternative to traditional antibiotics in the treatment of biofilm-associated infections.

Combined Metabolomics and Transcriptomics Analysis of the Distribution of Flavonoids in the Fibrous Root and Taproot of Polygonatum kingianum Coll.et Hemsl

Polygonati rhizoma, known for its distinct yellow rhizomes, is a common therapeutic and culinary plant in Far East Asia. The hue of medicinal plants is closely tied to the flavonoid biosynthesis and content levels. In this research, the fibrous root and taproot of Polygonatum kingianum Coll.et Hemsl. were studied to explore the secondary metabolite expression and flavonoid biosynthesis mechanisms using transcriptomics and metabolomics. Metabolic analysis identified that the differentially accumulated metabolites (DAMs) in the fibrous root and taproot were predominantly flavonoids, steroids, alkaloids, and phenolic acids. Overall, 200 flavonoids were identified in P. kingianum Coll.et Hemsl., with 170 exhibiting variances between the fibrous root and taproot. The transcriptome analysis revealed that a total of 289 unigenes encoding 32 enzymes were annotated into four flavonoid biosynthesis pathways, which include phenylpropanoid biosynthesis pathway, flavonoid biosynthesis pathway, isoflavonoid biosynthesis pathway, and flavone and flavonol biosynthesis pathway. The integration of transcriptomic and metabolomic data elucidated that the 76 differentially expressed genes (DEGs) encoding 13 enzyme genes (HCT, CCOMT, C4H, C3'H, CHI, PGT1, FLS, F3'H, CHS, ANR, DFR, F3'5'H, and LAR) and 15 DAMs preferred to be regulated in the flavonoid biosynthesis pathway. The expression of 10 DEGs was validated by qRT-PCR, agreeing with the same results by RNA-Seq. These findings shed light into the biosynthesis of secondary metabolites in P. kingianum Coll.et Hemsl., offering valuable information for the sustainable utilization and enhancement of this plant species.

NF-κB-Signaling-Targeted Immunomodulatory Nanoparticle with Photothermal and Quorum-Sensing Inhibition Effects for Efficient Healing of Biofilm-Infected Wounds

The development of therapeutics with high antimicrobial activity and immunomodulatory effects is urgently needed for the treatment of infected wounds due to the increasing danger posed by recalcitrant-infected wounds. In this study, we developed light-controlled antibacterial, photothermal, and immunomodulatory biomimetic N/hPDA@M nanoparticles (NPs). This nanoplatform was developed by loading flavonoid naringenin onto hollow mesoporous polydopamine NPs in a π-π-stacked configuration and encasing them with macrophage membranes. First, our N/hPDA@M NPs efficiently neutralized inflammatory factors present within the wound microenvironment by the integration of macrophage membranes. Afterward, the N/hPDA@M NPs effectively dismantled bacterial biofilms through a combination of the photothermal properties of PDA and the quorum sensing inhibitory effects of naringenin. It is worth noting that N/hPDA@M NPs near-infrared-enhanced release of naringenin exhibited specificity toward the NF-κB-signaling pathway, effectively mitigating the inflammatory response. This innovative design not only conferred remarkable antibacterial properties upon the N/hPDA@M NPs but also endowed them with the capacity to modulate inflammatory responses, curbing excessive inflammation and steering macrophage polarization toward the M2 phenotype. As a result, this multifaceted approach significantly contributes to expediting the healing process of infected skin wounds.

Anti-virulence potential of patuletin, a natural flavone, against Staphylococcus aureus: In vitro and In silico investigations

Staphylococcus aureus is a highly prevalent and aggressive human pathogen causing a wide range of infections. This study aimed to explore the potential of Patuletin, a rare natural flavone, as an anti-virulence agent against S. aureus. At a sub-inhibitory concentration (1/4 MIC), Patuletin notably reduced biofilm formation by 27 % and 23 %, and decreased staphyloxanthin production by 53 % and 46 % in Staphylococcus aureus isolate SA25923 and clinical isolate SA1, respectively. In order to gain a more comprehensive understanding of the in vitro findings, several in silico analyses were conducted. Initially, a 3D-flexible alignment study demonstrated a favorable structural similarity between Patuletin and B70, the co-crystallized ligand of CrtM, an enzyme that plays a pivotal role in the biosynthesis of staphyloxanthin. Molecular docking highlighted the strong binding of Patuletin to the active site of CrtM, with a high affinity of -20.95 kcal/mol. Subsequent 200 ns molecular dynamics simulations, along with MM-GBSA, ProLIF, PLIP, and PCAT analyses, affirmed the stability of the Patuletin-CrtM complex, revealing no significant changes in CrtM's structure upon binding. Key amino acids crucial for binding were also identified. Collectively, this study showcased the effective inhibition of CrtM activity by Patuletin in silico and its attenuation of key virulence factors in vitro, including biofilm formation and staphyloxanthin production. These findings hint at Patuletin's potential as a valuable therapeutic agent, especially in combination with antibiotics, to counter antibiotic-resistant Staphylococcus aureus infections.

Ultrasonically functionalized chitosan-gallic acid films inactivate Staphylococcus aureus through envelope-disruption under UVA light exposure

The significant threat of foodborne pathogens contamination has continuously promoted the development of efficient antimicrobial food packaging materials. Here, an antimicrobial film was prepared with gallic acid-grafted-chitosan (CS/GA) that obtained by a two-step ultrasound method. The resultant films exhibited good transparency, improved UV barrier performance, and enhanced mechanical strength. Specifically, with the grafting of 1.2 % GA, the UV blocking ability of CS/GA film at 400 nm was significantly increased by 19.7 % and the tensile strength was nearly two times higher than that of CS film. Moreover, the CS/GA films exhibited an inspiring photoactivated bactericidal ability under 400 nm UVA light irradiation that eradicated almost 99.9 % of Staphylococcus aureus (S. aureus) cells within 60 min. To gain more insights into the antibacterial mechanism, the treated S. aureus cells were further investigated by visualizing bacterial ultrastructure and analyzing membrane properties. The results pointed to the peptidoglycan layer as the primary action target when bacteria come into contact with CS/GA films. Afterward, the intracellular oxidative lesions, disrupted bacterial integrity, and disordered membrane functional properties collectively resulted in eventual cell death. The findings revealed the unique peptidoglycan targeting and membrane disruptive mechanisms of CS/GA films, confirming the application values in controlling foodborne pathogens.

The Most Potent Natural Pharmaceuticals, Cosmetics, and Food Ingredients Isolated from Plants with Deep Eutectic Solvents

There is growing interest in reducing the number of synthetic products or additives and replacing them with natural ones. The pharmaceutical, cosmetic, and food industries are especially focused on natural and bioactive chemicals isolated from plants or microorganisms. The main challenge here is to develop efficient and ecological methods for their isolation. According to the strategies and rules of sustainable development and green chemistry, green solvents and environmentally friendly technologies must be used. The application of deep eutectic solvents as efficient and biodegradable solvents seems to be a promising alternative to traditional methods. They are classified as being green and ecological but, most importantly, very efficient extraction media compared to organic solvents. The aim of this review is to present the recent findings on green extraction, as well as the biological activities and the possible applications of natural plant ingredients, namely, phenolics, flavonoids, terpenes, saponins, and some others. This paper thoroughly reviews modern, ecological, and efficient extraction methods with the use of deep eutectic solvents (DESs). The newest findings, as well as the factors influencing the efficiency of extraction, such as water content, and hydrogen bond donor and acceptor types, as well as the extraction systems, are also discussed. New solutions to the major problem of separating DESs from the extract and for solvent recycling are also presented.

Naringenin: A flavanone with anti-inflammatory and anti-infective properties

Although a growing body of research has recently shown how crucial inflammation and infection are to all major diseases, several of the medications currently available on the market have various unfavourable side effects, necessitating the development of alternative therapeutic choices. Researchers are increasingly interested in alternative medications or active components derived from natural sources. Naringenin is a commonly consumed flavonoid found in many plants, and since it was discovered to have nutritional benefits, it has been utilized to treat inflammation and infections caused by particular bacteria or viruses. However, the absence of adequate clinical data and naringenin's poor solubility and stability severely restrict its usage as a medicinal agent. In this article, we discuss naringenin's effects and mechanisms of action on autoimmune-induced inflammation, bacterial infections, and viral infections based on recent research. We also present a few suggestions for enhancing naringenin's solubility, stability, and bioavailability. This paper emphasizes the potential use of naringenin as an anti-inflammatory and anti-infective agent and the next prophylactic substance for the treatment of various inflammatory and infectious diseases, even though some mechanisms of action are still unclear, and offers some theoretical support for its clinical application.

Dietary (poly)phenols mitigate inflammatory bowel disease: Therapeutic targets, mechanisms of action, and clinical observations

Inflammatory bowel diseases (IBD), which include Crohn's disease and ulcerative colitis, are a rapidly growing public health concern worldwide. These diseases are heterogeneous at the clinical, immunological, molecular, genetic, and microbial level, but characteristically involve a disrupted immune-microbiome axis. Shortcomings in conventional treatment options warrant the need for novel therapeutic strategies to mitigate these life-long and relapsing disorders of the gastrointestinal tract. Polyphenols, a diverse group of phytochemicals, have gained attention as candidate treatments due to their array of biological effects. Polyphenols exert broad anti-inflammatory and antioxidant effects through the modulation of cellular signaling pathways and transcription factors important in IBD progression. Polyphenols also bidirectionally modulate the gut microbiome, supporting commensals and inhibiting pathogens. One of the primary means by which gut microbiota interface with the host is through the production of metabolites, which are small molecules produced as intermediate or end products of metabolism. There is growing evidence to support that modulation of the gut microbiome by polyphenols restores microbially derived metabolites critical to the maintenance of intestinal homeostasis that are adversely disrupted in IBD. This review aims to define the therapeutic targets of polyphenols that may be important for mitigation of IBD symptoms, as well as to collate evidence for their clinical use from randomized clinical trials.

Attenuation of quorum sensing system and virulence in Vibrio cholerae by phytomolecules

The Vibrio cholerae, a gram-negative bacterium, is the causative agent of cholera. Quorum sensing is a cell-to-cell communication that leads to gene expression, accumulation of signaling molecules, biofilm formation, and production of virulence factors. The quorum sensing pathway in V. cholerae is regulated by luxO, and biofilm formation and other virulence factors are positively controlled by aphA and negatively by hapR. Hence, targeting the global regulator luxO would be a promising approach to modulate the QS to curtail V. cholerae pathogenesis. The present study investigated the modulating activity of quercetin and naringenin on biofilm formation and quorum-sensing regulated phenotypes in V. cholerae. Then after we determined the anti-quorum sensing capability of phytomolecules against the model organism Chromobacterium violaceum. Also, we performed flow cytometry for live/dead bacteria, MTT assay, CLSM, and growth curve analysis to determine their role as QS modulators rather than anti-bacterial. V. cholerae strains VC287 and N16961 formed thick biofilm. We observed a two-fold reduction in the expression of biofilm-associated genes comprising gbpA, vpsA, rbmA, and mbaA in the presence of phytomolecules indicating that phytomolecules modulate quorum sensing pathway rather than killing the bacteria. These phytomolecules were non-toxic and non-hemolytic and had anti-adhesion and anti-invasion properties. In addition, quercetin and naringenin were found to be highly effective compared to known quorum-sensing inhibitors terrein and furanone C-30. Thus, this study provides evidence that phytomolecules: quercetin and naringenin modulate the quorum-sensing pathway rather than killing the bacteria and can be used as an anti-quorum-sensing molecule for therapy against the pathogen.

Phenolic Compounds in Bacterial Inactivation: A Perspective from Brazil

Phenolic compounds are natural substances that are produced through the secondary metabolism of plants, fungi, and bacteria, in addition to being produced by chemical synthesis. These compounds have anti-inflammatory, antioxidant, and antimicrobial properties, among others. In this way, Brazil represents one of the most promising countries regarding phenolic compounds since it has a heterogeneous flora, with the presence of six distinct biomes (Cerrado, Amazon, Atlantic Forest, Caatinga, Pantanal, and Pampa). Recently, several studies have pointed to an era of antimicrobial resistance due to the unrestricted and large-scale use of antibiotics, which led to the emergence of some survival mechanisms of bacteria to these compounds. Therefore, the use of natural substances with antimicrobial action can help combat these resistant pathogens and represent a natural alternative that may be useful in animal nutrition for direct application in food and can be used in human nutrition to promote health. Therefore, this study aimed to (i) evaluate the phenolic compounds with antimicrobial properties isolated from plants present in Brazil, (ii) discuss the compounds across different classes (flavonoids, xanthones, coumarins, phenolic acids, and others), and (iii) address the structure-activity relationship of phenolic compounds that lead to antimicrobial action.

Exploring Possible Ways to Enhance the Potential and Use of Natural Products through Nanotechnology in the Battle against Biofilms of Foodborne Bacterial Pathogens

Biofilms enable pathogenic bacteria to survive in unfavorable environments. As biofilm-forming pathogens can cause rapid food spoilage and recurrent infections in humans, especially their presence in the food industry is problematic. Using chemical disinfectants in the food industry to prevent biofilm formation raises serious health concerns. Further, the ability of biofilm-forming bacterial pathogens to tolerate disinfection procedures questions the traditional treatment methods. Thus, there is a dire need for alternative treatment options targeting bacterial pathogens, especially biofilms. As clean-label products without carcinogenic and hazardous potential, natural compounds with growth and biofilm-inhibiting and biofilm-eradicating potentials have gained popularity as natural preservatives in the food industry. However, the use of these natural preservatives in the food industry is restricted by their poor availability, stability during food processing and storage. Also there is a lack of standardization, and unattractive organoleptic qualities. Nanotechnology is one way to get around these limitations and as well as the use of underutilized bioactives. The use of nanotechnology has several advantages including traversing the biofilm matrix, targeted drug delivery, controlled release, and enhanced bioavailability, bioactivity, and stability. The nanoparticles used in fabricating or encapsulating natural products are considered as an appealing antibiofilm strategy since the nanoparticles enhance the activity of the natural products against biofilms of foodborne bacterial pathogens. Hence, this literature review is intended to provide a comprehensive analysis of the current methods in nanotechnology used for natural products delivery (biofabrication, encapsulation, and nanoemulsion) and also discuss the different promising strategies employed in the recent and past to enhance the inhibition and eradication of foodborne bacterial biofilms.

Antibiofilm effects of punicalagin against Staphylococcus aureus in vitro

Staphylococcus aureus is a common foodborne pathogen which can form biofilms to help them resist to antimicrobials. It brings great harm to human health. Punicalagin has good antimicrobial activities against S. aureus, but its effect on biofilm formation has not been clearly illustrated. The aim of this study was to explore the antibiofilm effects of punicalagin against S. aureus. Results showed that punicalagin did not significantly interfere with the growth of S. aureus at the concentrations of 1/64 MIC to 1/16 MIC. The biomass and metabolic activity of biofilms were significantly reduced when exposed to sub-inhibitory concentrations of punicalagin. The number of viable cells in the biofilms was also decreased after punicalagin treatment. Scanning electron microscopy and confocal laser scanning microscopy images confirmed that punicalagin damaged the structure of biofilms. The antibiofilm mechanism was partly due to the modification of the cell surface which led to the reduction of cell surface hydrophobicity. These findings suggest that punicalagin has the potential to be developed as an alternative to control S. aureus biofilms.

Sonosynthesis of nanobiotics with antimicrobial and antioxidant properties

Transforming small-molecule antibiotics into carrier-free nanoantibiotics represents an opportunity for developing new multifunctional therapeutic agents. In this study, we demonstrate that acoustic cavitation produced by high-frequency ultrasound transforms the antibiotic doxycycline into carrier-free nanobiotics. Upon sonication for 1 h at 10-15 W cm^-3, doxycycline molecules underwent hydroxylation and dimerization processes to ultimately self-assemble into nanoparticles of ∼100-200 nm in size. Micrometer sized particles can be also obtained by increasing the acoustic power to 20 W cm^-3. The nanodrugs exhibited antioxidant properties, along with antimicrobial activity against both Gram-positive (S. aureus) and Gram-negative (E. coli) bacterial strains. Our results highlight the feasibility of the ultrasound-based approach for engineering drug molecules into a nanosized formulation with controlled and multiple bio-functionalities.

Structure Identification and Functional Mechanism of Natural Active Components: A Special Issue

The natural active components derived from plants have attracted widespread attention due to their abundant species and source advantages [...]