Polymeric Nanoparticles Active against Dual-Species Bacterial Biofilms

Biofilm infections are a global public health threat, necessitating new treatment strategies. Biofilm formation also contributes to the development and spread of multidrug-resistant (MDR) bacterial strains. Biofilm-associated chronic infections typically involve colonization by more than one bacterial species. The co-existence of multiple species of bacteria in biofilms exacerbates therapeutic challenges and can render traditional antibiotics ineffective. Polymeric nanoparticles offer alternative antimicrobial approaches to antibiotics, owing to their tunable physico-chemical properties. Here, we report the efficacy of poly(oxanorborneneimide) (PONI)-based antimicrobial polymeric nanoparticles (PNPs) against multi-species bacterial biofilms. PNPs showed good dual-species biofilm penetration profiles as confirmed by confocal laser scanning microscopy. Broad-spectrum antimicrobial activity was observed, with reduction in both bacterial viability and overall biofilm mass. Further, PNPs displayed minimal fibroblast toxicity and high antimicrobial activity in an in vitro co-culture model comprising fibroblast cells and dual-species biofilms of Escherichia coli and Pseudomonas aeruginosa. This study highlights a potential clinical application of the presented polymeric platform.     

Chitosan-coated silver nanoparticles promoted antibacterial,antibiofilm, wound-healing of murine macrophages and antiproliferation of human breast cancer MCF 7 cells

In the present study, environmentally benign silver nanoparticles were synthesized using commercially purchased shrimp-shell chitosan as a capping agent. The synthesized chitosan-silver nanoparticles (Ch-AgNPs) were physico-chemically characterized by UV–Vis spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), high-resolution transmission electron microscopy (HR-TEM) along with energy dispersive X-ray analysis (EDX), DLS and Zeta potential analysis. Ch-Ag NPs were crystalline, uniformly dispersed, and spherically shaped, with particle size between 8 and 48 nm. The average size of Ch-AgNPs was 21 nm. In-vitro anti-biofilm activity of Ch-AgNPs was tested against wound infection-causing pathogenic bacteria such as Staphylococcus aureus (Gram-positive) and Pseudomonas aeruginosa (Gram-negative). Ch-AgNPs displayed anti-biofilm activity in a dose-dependent manner. Light and confocal-laser scanning microscopy confirmed the significant inhibition of biofilm growth of S. aureus (85%) and P. aeruginosa (95%) at 100 μg mL⁻¹ of Ch-AgNPs. Moreover, Ch-AgNPs promoted wound healing by increasing the migration of RAW 264.7 murine macrophages cells at 75 and 100 μg mL⁻¹after 24 h. In addition, in vitro cytotoxicity of Ch-AgNPs against MCF 7 (human breast cancer) cells, depicted the greater inhibition of proliferation of cells (64%) at 100 μg mL^−1.     

Development of Chitosan-Based Surfaces to Prevent Single- and Dual-Species Biofilms of Staphylococcus aureus and Pseudomonas aeruginosa

Implantable medical devices (IMDs) are susceptible to microbial adhesion and biofilm formation, which lead to several clinical complications, including the occurrence of implant-associated infections. Polylactic acid (PLA) and its composites are currently used for the construction of IMDs. In addition, chitosan (CS) is a natural polymer that has been widely used in the medical field due to its antimicrobial and antibiofilm properties, which can be dependent on molecular weight (Mw). The present study aims to evaluate the performance of CS-based surfaces of different Mw to inhibit bacterial biofilm formation. For this purpose, CS-based surfaces were produced by dip-coating and the presence of CS and its derivatives onto PLA films, as well surface homogeneity were confirmed by contact angle measurements, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The antimicrobial activity of the functionalized surfaces was evaluated against single- and dual-species biofilms of Staphylococcus aureus and Pseudomonas aeruginosa. Chitosan-based surfaces were able to inhibit the development of single- and dual-species biofilms by reducing the number of total, viable, culturable, and viable but nonculturable cells up to 79%, 90%, 81%, and 96%, respectively, being their activity dependent on chitosan Mw. The effect of CS-based surfaces on the inhibition of biofilm formation was corroborated by biofilm structure analysis using confocal laser scanning microscopy (CLSM), which revealed a decrease in the biovolume and thickness of the biofilm formed on CS-based surfaces compared to PLA. Overall, these results support the potential of low Mw CS for coating polymeric devices such as IMDs where the two bacteria tested are common colonizers and reduce their biofilm formation.     

Small molecule control of bacterial biofilms

Bacterial biofilms are defined as a surface attached community of bacteria embedded in a matrix of extracellular polymeric substances that they have produced. When in the biofilm state, bacteria are more resistant to antibiotics and the host immune response than are their planktonic counterparts. Biofilms are increasingly recognized as being significant in human disease, accounting for 80% of bacterial infections in the body and diseases associated with bacterial biofilms include: lung infections of cystic fibrosis patients, colitis, urethritis, conjunctivitis, otitis, endocarditis and periodontitis. Additionally, biofilm infections of indwelling medical devices are of particular concern, as once the device is colonized infection is virtually impossible to eradicate. Given the prominence of biofilms in infectious diseases, there has been an increased effort toward the development of small molecules that will modulate bacterial biofilm development and maintenance. In this review, we highlight the development of small molecules that inhibit and/or disperse bacterial biofilms through non-microbicidal mechanisms. The review discuses the numerous approaches that have been applied to the discovery of lead small molecules that mediate biofilm development. These approaches are grouped into: (1) the identification and development of small molecules that target one of the bacterial signaling pathways involved in biofilm regulation, (2) chemical library screening for compounds with anti-biofilm activity, and (3) the identification of natural products that possess anti-biofilm activity, and the chemical manipulation of these natural products to obtain analogues with increased activity.     

Preventing biofilm development on DGT devices using metals and antibiotics

The DGT technique has potential as a tool for monitoring reactive phosphorus in freshwater aquaculture effluents. Because those waters have high concentrations of suspended matter and nutrients, biofilms may form on the surface of the DGT devices. Those biofilms may hinder the movement of reactive phosphorus and hence interfere with the DGT measurements. We tested two antibiotics, glutaraldehyde and chloramphenicol, two metal-iodides, copper and silver and also two alternative filter types, nucleopore membrane and silver-based filters, to evaluate their respective potential to prevent the formation of algae. The treatment with silver iodide seems to affect the properties of the diffusive gel and changes the flux measurements of the DGT device. The DGT response observed using the copper iodide and chloramphenicol treatments was not significantly different from the control. Glutaraldehyde changed the macroproperties of the diffusive gel and interfered with the phosphorus detection using spectrophotometric determinations. The effect of the anti-biofilm treatments on the DGT measurements was independent of pH and ionic strength of the water. For the field deployment in fish farms, copper and silver were the best anti-biofilm agents. Copper prevented algal colonisation for 14-days post-deployment and the response was unaffected by the anti-biofilm agent throughout this period. Silver was even better and prevented biofilm formation up to a 21-days post-deployment. Conversely, chloramphenicol did not prevent algal colonisation for the 14- and 21-days deployments. However, for deployments longer than 14 days, it was difficult to obtain consistently good results for all of anti-biofilm agents tested, due to the high concentration of suspended matter in the freshwater effluents of the fish farms tested. This approach suggests a metal pre-treatment of the membrane filters is useful to prevent biofilm formation for DGT deployments aimed at P measurements. DGT deployments for metal measurements would likely require a different approach.     

Antimicrobial Potential of Biosynthesized Silver Nanoparticles by Aaronsohnia factorovskyi Extract

The green biosynthesis of nanoparticles by plant extracts is an attractive and promising technique for medicinal applications. In the current study, we chose one of the daisy plants, Aaronsohnia factorovskyi (which grows in the Najd region, Saudi Arabia), to investigate its anti-microbial efficacy, in combination with silver nanoparticles. The biosynthesized nanoparticles were evaluated for antibacterial activity against Staphylococcus aureus, Bacillus subtilis (Gram-positive), Pseudomonas aeruginosa, and Escherichia coli, (Gram-negative) using the disc diffusion method, while the antifungal activity was assessed against Fusarium oxysporum, Fusarium solani, Helminthosporium rostratum, and Alternaria alternata. The potential phytoconstituents of the plant extracts were identified by Fourier-transform infrared spectroscopy (FT-IR) techniques, the Field emission scanning electron microscopy (FE-SEM), Chromatography/Mass Spectrometry (GC-MS) techniques, and Zeta potential analysis. The current study revealed the ability of the tested plant extract to convert silver ions to silver nanoparticles with an average diameter of 104–140 nm. Biogenic Aaronsohnia factorovskyi-silver nanoparticles (AF-AgNPs) showed significant antibacterial activity against Staphylococcus aureus with inhibition zone diameter to 19.00 ± 2.94 mm, and antifungal activity against Fusarium solani, which reduced the growth of fungal yarn to 1.5 mm. The innovation of the present study is that the green synthesis of NPs, which is simple, cost-effective, provides stable nano-materials, and can be an alternative for the large-scale synthesis of silver nanoparticles.     

Metal Complexes—A Promising Approach to Target Biofilm Associated Infections

Microbial biofilms are represented by sessile microbial communities with modified gene expression and phenotype, adhered to a surface and embedded in a matrix of self-produced extracellular polymeric substances (EPS). Microbial biofilms can develop on both prosthetic devices and tissues, generating chronic and persistent infections that cannot be eradicated with classical organic-based antimicrobials, because of their increased tolerance to antimicrobials and the host immune system. Several complexes based mostly on 3D ions have shown promising potential for fighting biofilm-associated infections, due to their large spectrum antimicrobial and anti-biofilm activity. The literature usually reports species containing Mn(II), Ni(II), Co(II), Cu(II) or Zn(II) and a large variety of multidentate ligands with chelating properties such as antibiotics, Schiff bases, biguanides, N-based macrocyclic and fused rings derivatives. This review presents the progress in the development of such species and their anti-biofilm activity, as well as the contribution of biomaterials science to incorporate these complexes in composite platforms for reducing the negative impact of medical biofilms.     

Design,synthesis, biological evaluation and in silico studies of N-(pyridin-2-yl)-benzamides derivatives as quorum sensing inhibitors

The emergence of bacterial resistance against chemical treatment is a big threat to the efficacy of bacterial infection treatment. One of the major reasons for resistance to antimicrobial agents is growth of microorganisms in biofilm. An alternative treatment by developing novel anti-biofilm agents had led to the concept of quorum sensing (QS) inhibition, which primarily targets QS signaling system by disrupting cell-cell communication. Therefore, this study focuses to develop novel antimicrobial agents which work by QS inhibition and act as anti-biofilm agents against Bacillus Subtilis and Pseudomonas Aeruginosa. In this work, a natural product-like scaffolds from Asinex library were screened and N-pyridin-2-yl-benzamide moiety was chosen to design and synthesize. Synthesized compounds were evaluated for potential anti-biofilm activity for the aforesaid microorganisms and also checked for cell viability assay, where two potent compounds 3a and 3c showed their static biofilm activity to ∼59% and ∼58% at 100 μM, respectively against Bacillus subtilis. These synthesized compounds were investigated for physicochemical parameters and binding mode prediction through molecular modelling tools. The interactions and stability of these compounds showed better affinity towards TasA and LasR proteins from Bacillus subtilis and Pseudomonas aeruginosa, respectively. Furthermore, molecular dynamic simulation for 100 ns was executed in order to appreciate the stability of the protein and ligand complex. The overall results promised that N-pyridin-2-yl-benzamide derivatives can be discovered as a lead in developing potent anti-quorum sensing agents against various bacteria.     

Voice Prosthesis Coated with Sustained Release Varnish Containing Clotrimazole Shows Long-Term Protection against Candida albicans: An In Vitro Study

Fungal biofilm formation on voice prosthesis (VP) is a major health problem that requires repeated replacement of the prosthesis. Candida albicans is one of the pathogens that frequently inhabits the VP. We proposed that coating VPs with sustained-release varnish (SRV) containing clotrimazole (CTZ) might prevent fungal biofilm formation. The long-term antifungal activities of SRV-CTZ- versus SRV-placebo-coated VPs was tested daily by measuring the inhibition zone of C. albicans seeded on agar plates or by measuring the fungal viability of C. albicans in suspension. The extent of biofilm formation on coated VPs was analyzed by confocal microscopy and scanning electron microscopy. We observed that SRV-CTZ-coated VPs formed a significant bacterial inhibition zone around the VPs and prevented the growth of C. albicans in suspension during the entire testing period of 60 days. Fungal biofilms were formed on placebo-coated VPs, while no significant biofilms were observed on SRV-CTZ-coated VPs. HPLC analysis shows that CTZ is continuously released during the whole test period of 60 days at a concentration above the minimal fungistatic concentration. In conclusion, coating VPs with an SRV-CTZ film is a potential effective method for prevention of fungal infections and biofilm formation on VPs.     

Bioprospecting the Antibiofilm and Antimicrobial Activity of Soil and Insect Gut Bacteria

Antimicrobial resistance is a growing concern in public health and current research shows an important role for bacterial biofilms in recurrent or chronic infections. New strategies, therefore, are necessary to overcome antimicrobial resistance, through the development of new therapies that could alter or inhibit biofilm formation. In this sense, antibiofilm natural products are very promising. In this work, a bioprospection of antimicrobial and antibiofilm extracts from Uruguayan soil bacteria and insect gut bacteria was carried out. Extracts from extracellular broths were tested for their ability to inhibit planktonic cell growth and biofilm formation. Genomic analysis of Bacillus cereus ILBB55 was carried out. All extracts were able to inhibit the growth of, at least, one microorganism and several extracts showed MICs lower than 500 µg mL⁻¹ against microorganisms of clinical relevance (Staphylococcus aureus, Pseudomonas aeruginosa, and Enterobacter cloacae). Among the extracts evaluated for biofilm inhibition only ILBB55, from B. cereus, was able to inhibit, S. aureus (99%) and P. aeruginosa (62%) biofilms. Genomic analysis of this strain showed gene clusters similar to other clusters that code for known antimicrobial compounds. Our study revealed that extracts from soil bacteria and insect gut bacteria, especially from B. cereus ILBB55, could be potential candidates for drug discovery to treat infectious diseases and inhibit S. aureus and P. aeruginosa biofilms.     

Hydrophobic Chitosan Nanoparticles Loaded with Carvacrol against Pseudomonas aeruginosa Biofilms

Pseudomonas aeruginosa infections have become more challenging to treat and eradicate due to their ability to form biofilms. This study aimed to produce hydrophobic nanoparticles by grafting 11-carbon and three-carbon alkyl chains to a chitosan polymer as a platform to carry and deliver carvacrol for improving its antibacterial and antibiofilm properties. Carvacrol–chitosan nanoparticles showed ζ potential values of 10.5–14.4 mV, a size of 140.3–166.6 nm, and an encapsulation efficiency of 25.1–68.8%. Hydrophobic nanoparticles reduced 46–53% of the biomass and viable cells (7–25%) within P. aeruginosa biofilms. Diffusion of nanoparticles through the bacterial biofilm showed a higher penetration of nanoparticles created with 11-carbon chain chitosan than those formulated with unmodified chitosan. The interaction of nanoparticles with a 50:50 w/w phospholipid mixture at the air–water interface was studied, and values suggested that viscoelasticity and fluidity properties were modified. The modified nanoparticles significantly reduced viable P. aeruginosa in biofilms (0.078–2.0 log CFU·cm⁻²) and swarming motility (40–60%). Furthermore, the formulated nanoparticles reduced the quorum sensing in Chromobacterium violaceum. This study revealed that modifying the chitosan polarity to synthesize more hydrophobic nanoparticles could be an effective treatment against P. aeruginosa biofilms to decrease its virulence and pathogenicity, mainly by increasing their ability to interact with the membrane phospholipids and penetrate preformed biofilms.     

An In Vitro Study of the Effect of Viburnum opulus Extracts on Key Processes in the Development of Staphylococcal Infections

Staphylococcus aureus is still one of the leading causes of both hospital- and community-acquired infections. Due to the very high percentage of drug-resistant strains, the participation of drug-tolerant biofilms in pathological changes, and thus the limited number of effective antibiotics, there is an urgent need to search for alternative methods of prevention or treatment for S. aureus infections. In the present study, biochemically characterized (HPLC/UPLC–QTOF–MS) acetonic, ethanolic, and water extracts from fruits and bark of Viburnum opulus L. were tested in vitro as diet additives that potentially prevent staphylococcal infections. The impacts of V. opulus extracts on sortase A (SrtA) activity (Fluorimetric Assay), staphylococcal protein A (SpA) expression (FITC-labelled specific antibodies), the lipid composition of bacterial cell membranes (LC-MS/MS, GC/MS), and biofilm formation (LIVE/DEAD BacLight) were assessed. The cytotoxicity of V. opulus extracts to the human fibroblast line HFF-1 was also tested (MTT reduction). V. opulus extracts strongly inhibited SrtA activity and SpA expression, caused modifications of S. aureus cell membrane, limited biofilm formation by staphylococci, and were non-cytotoxic. Therefore, they have pro-health potential. Nevertheless, their usefulness as diet supplements that are beneficial for the prevention of staphylococcal infections should be confirmed in animal models in the future.     

Phytofabrication of silver nanoparticles from Limonia acidissima leaf extract and their antimicrobial,antioxidant and its anticancer prophecy

Green synthesis of nanoparticles by eco-friendly methods is a recent technique which draws the attention of researchers because of the reward over many conventional chemical methods. The present work focuses on aqueous Limonia acidissima leaf extract in synthesizing silver nanoparticles and its applications in a simple way. The silver nanoparticles formed were characterized by Infrared, Ultra violet-visible, X-ray diffraction, transmission electron microscopic, and atomic force microscopic techniques. The powder X-ray diffraction studies and transmission electron microscopic images reveal that the silver nanoparticles synthesized were approximately 10–40 nm and have a spherical structure. The nanoparticles were assayed for their antibacterial, antifungal and antioxidant activity. The antimicrobial studies for the silver nanoparticles show a maximum zone of inhibition of 8.8 mm for Bacillus subtilis bacteria and 8.5 mm for Candida albicans fungi at 3 and 1 μg/mL respectively. In-silico ADMET studies reveal that the toxicity, bioactivity, pharmacokinetics and drug-likeness properties of Limonia acidissima leaf extract is good. The molecular docking studies show that the microbial activity is high for Bacillus subtilis and Candida albicans showing the coincidence of the in silico and in vitro studies as expected. The free radical scavenging activity of nanoparticles is 80 for 100 μg/mL. The 50% of inhibition of silver nanoparticles against human breast cancer cell lines is 18 μg/mL. It is evident that silver nanoparticles would be helpful in treating cancer cell lines and have great perspectives in the biomedical sector.     

Searching Hit Potential Antimicrobials in Natural Compounds Space against Biofilm Formation

Biofilms are communities of microorganisms that can colonize biotic and abiotic surfaces and thus play a significant role in the persistence of bacterial infection and resistance to antimicrobial. About 65% and 80% of microbial and chronic infections are associated with biofilm formation, respectively. The increase in infections by multi-resistant bacteria instigates the need for the discovery of novel natural-based drugs that act as inhibitory molecules. The inhibition of diguanylate cyclases (DGCs), the enzyme implicated in the synthesis of the second messenger, cyclic diguanylate (c-di-GMP), involved in the biofilm formation, represents a potential approach for preventing the biofilm development. It has been extensively studied using PleD protein as a model of DGC for in silico studies as virtual screening and as a model for in vitro studies in biofilms formation. This study aimed to search for natural products capable of inhibiting the Caulobacter crescentus enzyme PleD. For this purpose, 224,205 molecules from the natural products ZINC15 database, have been evaluated through molecular docking and molecular dynamic simulation. Our results suggest trans-Aconitic acid (TAA) as a possible starting point for hit-to-lead methodologies to obtain new inhibitors of the PleD protein and hence blocking the biofilm formation.     

Green Synthesis and Characterization of Silver Nanoparticles Using Spondias mombin Extract and Their Antimicrobial Activity against Biofilm-Producing Bacteria

Multidrug resistant bacteria create a challenging situation for society to treat infections. Multidrug resistance (MDR) is the reason for biofilm bacteria to cause chronic infection. Plant-based nanoparticles could be an alternative solution as potential drug candidates against these MDR bacteria, as many plants are well known for their antimicrobial activity against pathogenic microorganisms. Spondias mombin is a traditional plant which has already been used for medicinal purposes as every part of this plant has been proven to have its own medicinal values. In this research, the S. mombin extract was used to synthesise AgNPs. The synthesized AgNPs were characterized and further tested for their antibacterial, reactive oxygen species and cytotoxicity properties. The characterization results showed the synthesized AgNPs to be between 8 to 50 nm with -11.52 of zeta potential value. The existence of the silver element in the AgNPs was confirmed with the peaks obtained in the EDX spectrometry. Significant antibacterial activity was observed against selected biofilm-forming pathogenic bacteria. The cytotoxicity study with A. salina revealed the LC50 of synthesized AgNPs was at 0.81 mg/mL. Based on the ROS quantification, it was suggested that the ROS production, due to the interaction of AgNP with different bacterial cells, causes structural changes of the cell. This proves that the synthesized AgNPs could be an effective drug against multidrug resistant bacteria.     

Evaluating Tannins and Flavonoids from Traditionally Used Medicinal Plants with Biofilm Inhibitory Effects against MRGN E. coli

In the search for alternative treatment options for infections with multi-resistant germs, traditionally used medicinal plants are currently being examined more intensively. In this study, the antimicrobial and anti-biofilm activities of 14 herbal drugs were investigated. Nine of the tested drugs were traditionally used in Europe for treatment of local infections. For comparison, another five drugs monographed in the European Pharmacopoeia were used. Additionally, the total tannin and flavonoid contents of all tested drugs were analyzed. HPLC fingerprints were recorded to obtain further insights into the components of the extracts. The aim of the study was to identify herbal drugs that might be useable for treatment of infectious diseases, even with multidrug resistant E. coli, and to correlate the antimicrobial activity with the total content of tannins and flavonoids. The agar diffusion test and anti-biofilm assay were used to evaluate the antimicrobial potential of different extracts from the plants. Colorimetric methods (from European Pharmacopeia) were used for determination of total tannins and flavonoids. The direct antimicrobial activity of most of the tested extracts was low to moderate. The anti-biofilm activity was found to be down to 10 µg mL⁻¹ for some extracts. Tannin contents between 2.2% and 10.4% of dry weight and total flavonoid contents between 0.1% and 1.6% were found. Correlation analysis indicates that the antimicrobial and the anti-biofilm activity is significantly (p < 0.05) dependent on tannin content, but not on flavonoid content. The data analysis revealed that tannin-rich herbal drugs inhibit pathogens in different ways. Thus, some of the tested herbal drugs might be useable for local infections with multi-resistant biofilm-forming pathogens. For some of the tested drugs, this is the first report about anti-biofilm activity, as well as total tannin and flavonoid content.     

Synthesis of indole-based oxadiazoles and their interaction with bacterial peptidoglycan and SARS-CoV-2 main protease: In vitro,molecular docking and in silico ADME/Tox study

In the present study, Indole-based-oxadiazole (1A-17A) compounds were successfully synthesized. The structures of all synthesized compounds were fully characterized by different sophisticated spectroscopic techniques such 1H NMR, 13C NMR, and HREI-MS. Further, the synthesized compounds were explored to investigate their broad-spectrum antibacterial and antibiofilm potential against multidrug resistant Pseudomonas aeruginosa (MDR-PA) and methicillin resistant Staphylococcus aureus (MRSA). The compounds possessed a broad spectrum of antibacterial activity having MIC values of values 1–8 mg/ml against the tested microorganisms. Compound A6 and A7 shows maximum antibacterial activity against MDR-PA, whereas A6, A7 and A11 shows highest activity against MRSA. Furthermore, antibiofilm assay shows that A6, A7 and A11 showed maximum inhibition of biofilm formation and it was found that at 4 mg/ml; A6, A7 and A11 inhibit MRSA biofilm formation by 81.1, 77.5 and 75.9%, respectively; whereas in case of P. aeruginosa; A6 and A7 showed maximum biofilm inhibition and inhibit biofilm formation by 81.5 and 73.7%, respectively. Molecular docking study showed that compounds A6, A7, A8, A10, and A11 had high binding affinity to bacterial peptidoglycan, indicating their potential inhibitory activity against tested bacteria, whereas A6 and A11 were found to be the most effective inhibitors of SARS CoV-2 main protease (3CLpro), with a binding affinity of ? 7.78 kcal/mol. Furthermore, SwissADME and pkCSM-pharmacokinetics online tools was applied to calculate the ADME/Tox profile of the synthesized compounds and the toxicity of these chemicals was found to be low. The Lipinski, Veber, Ghose, and Consensus LogP criteria were also used to predict drug-likeness levels of the compounds. Our findings imply that the synthesized compounds could be a useful for the preventing and treating biofilm-related microbial infection as well as SARS-CoV2 infections.     

Antimicrobial evaluation of selected naturally occurring oxyprenylated secondary metabolites

This study tested the antimicrobial activity of eight selected naturally occurring oxyprenylated secondary metabolites against Staphylococcus aureus ATCC 29213, S. epidermidis ATCC 35984, Escherichia coli ATCC 8739, Pseudomonas aeruginosa ATCC 9027 and Candida albicans ATCC 10231. Results showed a moderate antimicrobial activity. The most active compounds were 3-(4-geranyloxyphenyl)-1-ethanol (4) and 3-(4-isopentenyloxyphenyl)-1-propanol (5) that were tested on mature and in-formation biofilms of all micro-organisms, moreover the cytotoxic activity was evaluated. Except for S. epidermidis, both compounds reduced significantly (p < 0.05) the microbial biofilm formation at 1/2 MIC and 1/4 MIC, in particular, compounds 4 and 5 at each concentration, inhibited E. coli biofilm formation to a greater extent, the biofilm formation was never more than 44% in respect to the control, moreover both compounds showed a low cytotoxic effect. Oxyprenylated derivatives may be of great interest for the development of novel antimicrobial therapeutic strategies and the synthesis of semi-synthetic analogues with anti-biofilm efficacy.     

Analysis of <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> PAO1 Biofilm Protein Profile After Exposure to <Emphasis Type="Italic">n</Emphasis>-Butanolic <Emphasis Type="Italic">Cyclamen coum</Emphasis> Extract Alone and in Combination with Ciprofloxacin

Pseudomonas aeruginosa biofilm-related infections are the major cause of premature death in cystic fibrosis patients. Strategies to induce biofilm dispersal are of interest, because of their potential in preventing biofilm-related infections. Our previous work demonstrated that n-butanolic Cyclamen coum extract with ciprofloxacin could eliminate 1- and 3-day-old P. aeruginosa PAO1 biofilms. To gain new insights into the role of C. coum extract and its synergistic effect with ciprofloxacin in eliminating P. aeruginosa PAO1 biofilms, two-dimensional gel electrophoresis (2-DE) in combination with mass spectrometry-based protein identification were used. Changes in the bacterial protein expression were analyzed when 3-day-old biofilm cells were exposed to the C. coum extract alone and in combination with ciprofloxacin. Proteins involved in alginate biosynthesis, quorum sensing, adaptation/protection, carbohydrate and amino acid metabolism showed a weaker expression in the C. coum extract-ciprofloxacin-treated biofilm cells compared to those in the untreated cells. Interestingly, the proteome of C. coum extract-ciprofloxacin-treated biofilm revealed more resemblance to the planktonic phenotype than to the biofilm phenotype. It appears that saponin extract in combination with ciprofloxacin causes biofilm disruption due to several mechanisms such as motility induction, cell envelope integrity perturbation, stress protein expression reduction, and more importantly, signal transduction perturbation. In conclusion, exposure to a combination of biofilm dispersal such as saponin extract and antimicrobial agents may offer a novel strategy to control preestablished, persistent P. aeruginosa biofilms and biofilm-related infections.     

Anti-Biofilm and Anti-Hemolysis Activities of 10-Hydroxy-2-decenoic Acid against Staphylococcus aureus

Persistent infections caused by Staphylococcus aureus biofilms pose a major threat to global public health. 10-Hydroxy-2-decenoic acid (10-HDA), a main fatty acid in royal jelly, has been shown to possess various biological activities. The purpose of this study was to explore the effects of 10-HDA on the biofilms and virulence of S. aureus and its potential molecular mechanism. Quantitative crystal violet staining indicated that 10-HDA significantly reduced the biofilm biomass at sub-minimum inhibitory concentration (MIC) levels (1/32MIC to 1/2MIC). Scanning electron microscope (SEM) observations demonstrated that 10-HDA inhibited the secretion of extracellular polymeric substances, decreased bacterial adhesion and aggregation, and disrupted biofilm architecture. Moreover, 10-HDA could significantly decrease the biofilm viability and effectively eradicated the mature biofilms. It was also found that the hemolytic activity of S. aureus was significantly inhibited by 10-HDA. qRT-PCR analyses revealed that the expressions of global regulators sarA, agrA, and α-hemolysin gene hla were downregulated by 10-HDA. These results indicate that 10-HDA could be used as a potential natural antimicrobial agent to control the biofilm formation and virulence of S. aureus.