Anti-pathogenic Agents Research Articles

Novel Lactic Acid Bacteria Strains from Regional Peppers with Health-Promoting Potential

This study provides a comprehensive investigation of lactic acid bacteria (LAB) isolated from Argentinean Capsicum annum L. This research covers important aspects, including genotypic characterization, bacterial stress tolerance, adhesion ability, safety evaluation, and functional and technological properties. The predominant isolates were identified as Lactilactobacillus curvatus and Lactiplantibacillus plantarum. A Rep-PCR analysis grouped the isolates into 11 clonal groups. Lp. plantarum LVP 40 and LV 46, Levilactobacillus brevis LVP 41, Pediococcus pentosaceus LV P43, and Lt. curvatus LVP44 displayed both safety and resilience against adverse conditions such as a slow pH, bile, and simulated gastric and intestinal juices. Moreover, the LAB strains exhibited high hydrophobicity and auto-aggregation percentages, NaCl tolerance, and a substantial acidifying capacity. LAB supernatants demonstrated promising surfactant and emulsifying properties. Likewise, they differentially inhibited Staphylococcus aureus and Pseudomonas aeruginosa biofilms, showcasing their potential as antipathogenic agents. Noteworthily, some strains displayed considerable co-aggregation with these pathogens, and several isolates showed an effective antimutagenic and detoxifying power, further emphasizing their multifaceted capabilities. Five pepper bacterial strains showcased beneficial properties, suggesting their potential for gut health enhancement. In summary, these LAB strains hold promise as vegetable fermentation starters, contributing to food safety and versatile applications in food science.

Oral antipathogenic and antiviral properties of Boesenbergia rotunda (L.) Mansf. Extracts with panduratin A as active compound

This study investigated the anti-oral pathogen and anti-human coronavirus properties of Boesenbergia rotunda, a traditional Thai medicinal plant used for treating oral diseases. Boesenbergia rotunda Crude extracts (CBR) and B. rotunda fractionated extracts (FBR) of B. rotunda were obtained and analyzed. Panduratin A, present in both CBR and FBR, was found to play a key role in their antimicrobial efficacy. Both the extracts of B. rotunda exhibited significant antimicrobial activity against Streptococcus mutans, Streptococcus pyogenes, Streptococcus sobrinus, and Candida albicans with minimum inhibitory concentration and minimum bactericidal concentration ratios demonstrating their effectiveness. Furthermore, both extracts showed a potent and direct inhibitory effect against human coronavirus 229E, with nearly 99.99% efficacy and a 4-log reduction in viral activity at a concentration of 1,600 μg/ml within 30 minutes. This study demonstrates the potential of B. rotunda as an antiviral and antipathogenic agent, with panduratin A as a bioactive compound. FBR is more potent than CBR against oral pathogens. These findings suggest that B. rotunda is a promising herbal medicine for treating oral diseases and viral infections.

Developing 3-(2-Isocyano-6-methylbenzyl)-1H-indole Derivatives to Enhance the Susceptibility of Serratia marcescens by Occluding Quorum Sensing.

Quorum sensing (QS) inhibition is recognized as a novel antimicrobial target for infections caused by drug-resistant pathogens and is an attractive strategy for antipathogenic agent development. We designed and synthesized three parts of 3-(2-isocyanobenzyl)-1H-indole derivatives and tested their activity as novel quorum sensing inhibitors (QSIs). 3-(2-Isocyanobenzyl)-1H-indole derivatives demonstrated promising QS, biofilms, and prodigiosin inhibitory activities against Serratia marcescens at subminimum inhibitory concentrations (sub-MICs). In particular, 3-(2-isocyano-6-methylbenzyl)-1H-indole (IMBI, 32) was identified as the best candidate based on several screening assays, including biofilm and prodigiosin inhibition. Further studies demonstrated that exposure to IMBI at 1.56 μg/mL to S.marcescens NJ01 significantly inhibited the formation of biofilms by 42%. The IMBI treatment on S.marcescens NJ01 notably enhanced the susceptibility of the formed biofilms, destroying the architecture of the biofilms by up to 40%, as evidenced by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). For interference of virulence factors in S.marcescens NJ01, IMBI at 3.12 μg/mL inhibited the activity of protease and extracellular polysaccharides (EPS) by 17% and 51%, respectively, which were higher than that of the positive control vanillic acid (VAN). Furthermore, IMBI downregulated the expression of QS- and biofilm-related genes fimA, bsmA, pigP, flhC, rssB, fimC, and rsmA by 1.02- to 2.74-fold. To confirm these findings, molecular docking was performed, which indicated that the binding of IMBI to SmaR, RhlI, RhlR, LasR, and CviR could antagonize the expression of QS-linked traits. In addition, molecular dynamic simulations (MD) and energy calculations indicated that the binding of receptors with IMBI was extremely stable. The biofilms of S.marcescens NJ01 were markedly reduced by 50% when IMBI (0.39 μg/mL) was combined with kanamycin (0.15 μg/mL). In conclusion, this study highlights the potency of IMBI in inhibiting the virulence factors of S.marcescens. IMBI has all the potential to be developed as an effective and efficient QS inhibitor and antibiofilm agent in order to restore or improve antimicrobial drug sensitivity.

Green synthesis of silver nanoparticles using Moringa oleifera and its efficacy against gram-negative bacteria targeting quorum sensing and biofilms

AbstractGram-negative pathogenic bacteria are the leading cause of high morbidity and mortality in humans globally. The majority of such pathogens has gained the status of multidrug resistance and requires the development of new anti-pathogenic agent. Moringa oleifera is a widely distributed and quickly proliferating medicinal plant, making it an easy source for extracting bioactive components. It is rich in bioactive compounds which can act as stabilizing and reducing agents during the synthesis of silver nanoparticles. It is well-recognized for its several medical benefits, including antibacterial action. As a result, it is an excellent option for synthesizing AgNPs with improved antibacterial characteristics. Considering the above properties, less explored Moringa oleifera was used for the green synthesis of nanoparticles. Targeting biofilms and virulence factors of Gram-negative bacteria by green synthesized metal nanoparticles is an alternative approach to combat antimicrobial resistance. Silver nanoparticles (MO-AgNPs) synthesized using Moringa oleifera leaf (MOL) extract were characterized using Ultraviolet–visible spectroscopy (UV–vis spectroscopy), Fourier-transform infrared spectroscopy (FTIR), Scanning electron microscopy-energy dispersive X-ray analysis (SEM–EDX), Transmission Electron Microscopy (TEM), and X-Ray Diffraction analysis (XRD). The absorption spectra of silver nanoparticles showed a band of absorption near 440 nm, associated with spherical silver nanoparticles. At sub-minimum inhibitory concentrations (sub-MICs), the MO-AgNPs inhibit the Quorum Sensing-mediated virulence factors and biofilm formation against three Gram-negative bacteria (Escherichia fergusonii, Serratia marcescens, and Chromobacterium violaceum). QS-mediated virulence factors in test bacteria were reduced by 80.67% (violacein), prodigiosin production (77.45%), exoprotease activity (76.02%), and swarming motility (86.5%). MO-AgNPs also demonstrated broad-spectrum antibiofilm activity against test bacteria, ranging from 77.95 to 82.4% inhibition. Microscopic analysis of biofilms showed significant structural change and inhibition. Our results demonstrate appreciable in vitro activity of MO-AgNPs against the selected pathogens, which could be used as an alternative therapeutic agent for treating infection caused by drug-resistant bacteria and preventing biofilm development by bacteria on medical devices and other surfaces. Graphical abstract

Star polymer soil delivery nanoplatform for applying biological agents in the field to control plant rhizosphere diseases

As the main cause of destructive plant diseases, pathogenic oomycete in plant rhizosphere brings about enormous losses to agricultural production. Although chemical pesticides are still one of the most important prevention and control methods for phytopathogens, the usage of chemical pesticides was limited by the 3R (resistance, residue, and rampant) problem. In the early stage of our research, analysis and comparison of the metabolome of resistance to Phytophthora nicotianae and common strain suggested that naringenin might be a highly efficient potential biogenic antimicrobial agent to prevent and control soil rhizosphere diseases. Unfortunately, the bioactivity and absorption capacity of active ingredients in the environment made it unsuitable for field application; thus, for efficient field application of naringenin, the 24 nm-sized naringenin-loaded nano-star-shaped polymerized (NSPs) were prepared with good loading efficiency 37.3% for naringenin. The soil mobility test indicated that NSPs could effectively reduce the adsorption of active ingredients and enhance the mobility of active ingredients in soil. The bacteriostatic test proved that these NSPs had better antimicrobial activity than the naringenin used alone and could efficiently induce the expression of plant resistance phenylpropanoid compounds. Finally, pot and field experiments showed improved control efficiency of NSPs 41% loaded with naringenin. Transcriptome analysis found that a large number of energy-related genes were downregulated in NSPs nematodes, suggesting that disturbed energy-related genes might lead to the disturbance of energy synthesis and metabolism. Naringenin-loaded nano-carriers were used to prevent and control plant disease-causing pathogens in the rhizosphere, which is of great significance to improve the prevention and control effect and reduce the environmental load of these anti-pathogenic agents.

Identification of anti-pathogenic activity among in silico predicted small-molecule inhibitors of Pseudomonas aeruginosa LasR or nitric oxide reductase (NOR).

Antibiotic-resistant Pseudomonas aeruginosa strains cause considerable morbidity and mortality globally. Identification of novel targets in this notorious pathogen is urgently warranted to facilitate discovery of new anti-pathogenic agents against it. This study attempted to identify small-molecule inhibitors of two important proteins LasR and nitric oxide reductase (NOR) in P. aeruginosa. 'Las' system can be said to be the 'master' regulator of quorum sensing in P. aeruginosa, whose receptor protein is LasR. Similarly, NOR is crucial to detoxification of reactive nitrogen species. In silico identification of potential LasR or NOR inhibitors was attempted through a virtual screening platform AtomNet® to obtain a final subset of <100 top scoring compounds. These compounds were evaluated for their in vivo anti-pathogenic activity by challenging the model host Caenorhabditis elegans with P. aeruginosa in the presence or absence of test compounds. Survival of the worm population in 24-well assay plates was monitored over a period of 5 days microscopically. Of the 96 predicted LasR inhibitors, 11 exhibited anti-Pseudomonas activity (23%-96% inhibition of bacterial virulence as per third-day end-point) at 25-50 µg/mL. Of the 85 predicted NOR inhibitors, 8 exhibited anti-Pseudomonas activity (40%-85% inhibition of bacterial virulence as per second-day end-point) at 25-50 µg/mL. Further investigation on molecular mode of action of compounds found active in this study is warranted. Virtual screening can be said to be a useful tool in narrowing down the list of compounds requiring actual wet-lab screening, saving considerable time and efforts for drug discovery.

Green synthesis of copper nanoparticles employing Annona squamosa L extract as antimicrobial and anticancer agents

Due to the potential of nanotechnology in suppressing the increasing burden of pathogenic infections and cancer incidences, researchers are developing nanoparticles that are high in efficacy and economically affordable. Herein, we aimed to synthesize Cu nanoparticles (CuNPs) via a green route by utilizing Annona squamosa L stem barks and evaluate its activities against pathogenic bacteria and fungi (Staphylococcus aureus, Escherichia coli, and Candida albicans). The aqueous extract of Annona squamosa L stem barks was determined for total phenolic content (TPC) and total flavonoid content (TFC). The CuNPs were obtained by adding the CuSO4 0.1 M into the foregoing extract and further characterized using Fourier-transform infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy, transmission electron microscopy, and X-Ray diffraction. The antibacterial and antifungal activities were examined based on Kirby-Bauer method. The anticancer potential of CuNPs were assessed based on 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay using breast cancer MCF-7 cells. The results revealed that the spherical CuNPs had average particle diameter of 13.7 ± 3.3 nm and was observed to interact with the phytoconstituents contained in the A. squamosa extract. Inhibition zones of 15.7, 12.3, and 13.9 mm were achieved by the CuNPs against S. aureus, E. coli, and C. albicans, respectively. As for the anticancer activity (MCF-7), the IC50 of 130.39 mg/L was obtained. In conclusion, the A. squamosa stem barks-mediated CuNPs could act as an anti-pathogenic agent with anticancer activity requiring further investigation using different cancer cells.

Biofilm reduction, in-vitro cytotoxicity and computational drug-likeness of selected phytochemicals to combat multidrug-resistant bacteria

Multidrug-resistant (MDR) bacteria in biofilms are frequently linked with persistent infections across healthcare settings, due to their virulence factors. Since the post-antibiotic era coerces the quest for novel therapeutics, the use of medicinal plants and their phytochemicals emerges as prospective alternatives for the failing antibiotics. Preliminary screening of untargeted drugs for their drug-likeness and biosafety properties is a necessary step in the advancement of the drug discovery process. Thus, the study aimed to assess the noteworthy phytochemicals with antibacterial potential to reduce the biofilm formation of selected MDR bacteria, evaluate their safe use and drug-likeness properties thereby providing advanced knowledge to contribute to the search for safe, antipathogenic drugs. Three phytochemicals of 1,2,3-benzenetriol, guanosine and phytol revealed significant minimum inhibitory concentrations (MIC) between 0.250 – 0.040 mg/mL against Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus and Streptococcus pyogenes. Guanosine and phytol, both revealed noteworthy MIC values of 0.016 and 0.031 mg/mL for S. pyogenes and S. aureus, respectively. Five MDR bacterial pathogens treated with 1,2,3-benzenetriol, guanosine and phytol at a concentration of 0.250 mg/mL reduced anti-adhesion and biofilm development up to 78.88% and 31.82%, respectively. In situ visualisation by scanning electron microscope (SEM) displayed guanosine to significantly disrupt the biofilm structures of S. aureus, S. pyogenes and P. aeruginosa. Atomic force microscope (AFM) detected differences between the topographies of S. aureus, S. pyogenes and P. aeruginosa biofilms treated with guanosine and phytol. Guanosine and phytol showed approximately 100% of cell viability in a dose-dependent manner (0.25 – 0.001 mg/mL) while causing no cell damage on African monkey kidney Vero (epithelial) cells and showed a cytostatic rather than a cytotoxic effect. Drug-likeness in-silico screening revealed that the compounds obeyed Lipinski's rules and have bioavailable scores of 0.55F. Guanosine and phytol showed antivirulent, biosafety and drug-likeness properties with significant pharmacokinetic predictions. This study highlights the significance of phytotherapeutics for the development of novel antipathogenic agents.

Pathogen resistance in soils associated withbacteriome network reconstruction through reductive soil disinfestation.

Reductive soil disinfestation (RSD) is an effective bioremediation technique to restructure the soil microbial community and eliminate soilborne phytopathogens. Yet we still lack a comprehensive understanding of the keystone taxa involved and their roles in ecosystem functioning in degraded soils treated by RSD. In this study, the bacteriome network structure in RSD-treated soil and the subsequent cultivation process were explored. As a result, bacterial communities in RSD-treated soil developed more complex topologies and stable co-occurrence patterns. The richness and diversity of keystone taxa were higher in the RSD group (module hub: 0.57%; connector: 23.98%) than in the Control group (module hub: 0.16%; connector: 19.34%). The restoration of keystone taxa in RSD-treated soil was significantly (P < 0.01) correlated with soil pH, total organic carbon, and total nitrogen. Moreover, a strong negative correlation (r = -0.712; P < 0.01) was found between keystone taxa richness and Fusarium abundance. Our results suggest that keystone taxa involved in the RSD network structure are capable of maintaining a flexible generalist mode of metabolism, namely with respect to nitrogen fixation, methylotrophy, and methanotrophy. Furthermore, distinct network modules composed by numerous anti-pathogen agents were formed in RSD-treated soil; i.e., the genera Hydrogenispora, Azotobacter, Sphingomonas, and Clostridium_8 under the soil treatment stage, and the genera Anaerolinea and Pseudarthrobacter under the plant cultivation stage. The study provides novel insights into the association between fungistasis and keystone or sensitive taxa in RSD-treated soil, with significant implications for comprehending the mechanisms of RSD. KEY POINTS: • RSD enhanced bacteriome network stability and restored keystone taxa. • Keystone taxa richness was negatively correlated with Fusarium abundance. • Distinct sensitive OTUs and modules were formed in RSD soil.

Biomedical,clinical and environmental applications of platinum-based nanohybrids: An updated review

Platinum nanoparticles (Pt NPs) have numerous applications in various sectors, including pharmacology, nanomedicine, cancer therapy, radiotherapy, biotechnology and environment mitigation like removal of toxic metals from wastewater, photocatalytic degradation of toxic compounds, adsorption, and water splitting. The multifaceted applications of Pt NPs because of their ultra-fine structures, large surface area, tuned porosity, coordination-binding, and excellent physiochemical properties. The various types of nanohybrids (NHs) of Pt NPs can be fabricated by doping with different metal/metal oxide/polymer-based materials. There are several methods to synthesize platinum-based NHs, but biological processes are admirable because of green, economical, sustainable, and non-toxic. Due to the robust physicochemical and biological characteristics of platinum NPs, they are widely employed as nanocatalyst, antioxidant, antipathogenic, and anticancer agents. Indeed, Pt-based NHs are the subject of keen interest and substantial research area for biomedical and clinical applications. Hence, this review systematically studies antimicrobial, biological, and environmental applications of platinum and platinum-based NHs, predominantly for treating cancer and photo-thermal therapy. Applications of Pt NPs in nanomedicine and nano-diagnosis are also highlighted. Pt NPs-related nanotoxicity and the potential and opportunity for future nano-therapeutics based on Pt NPs are also discussed.

IN-VITRO ANTI-MICROBIAL AND ANTIOXIDANT PROPERTIES: SAPONINS FRACTION OF SAPINDUS MUKOROSSI AGAINST PREVALENT PATHOGENS

Developing new antibiotics, it is becoming increasingly difcult, with greater time-consuming and more expensive to develop new antibiotics, especially because emerging strains are becoming increasingly resistant to existing antibiotics. Phytochemically, saponins are plant secondary metabolites with powerful therapeutic effects and there are several scientic evidences that plant saponins are potent pharmacological agents. In this study, Effect of Saponins derived from the leaves of Sapindus mukorossi on prevalent bacterial pathogens growth and efux-pump activity were tested on Pseudomonas aeruginosa and Staphylococcus aureus. An antibiotic standard ampicillin was comparable to the inhibitory effects of saponins at 1.80 mg/mL of concentration on bacterial growth. The saponins from Sapindus mukorossi had showed a MIC of 0.0036 mg/mL and an MBC of 0.96 mg/mL, making them the most effective against S. aureus and P. aeruginosa. It was proven that plant saponins had bacteriostatic effects on P. aeruginosa and S. aureus. Sapindus mukorossi saponins inhibited the drug efux pump susceptible in P. aeruginosa, which resulted in a 132% increase in Rhodamine-6G accumulations compared to the control. As a result, Leaf saponins from Sapindus mukorossi exhibited antibacterial activity as well as the ability to inhibit the compounds energy dependent transport across cell membranes, and these saponins can be used as potential principal composites for the development of herbal based anti-pathogenic bacterial agents and their adjunct composites

Bioactivity and molecular docking of lactones isolated from Centaurea pseudosinaica Czerep

Two cytotoxic sesquiterpene lactones, 17-epichlorohyssopifolin A (1) and chlorjanerin (2), and a monoterpene lactone, loliolide (3) were isolated from Centaurea pseudosinaica. The cytotoxicity of the total extract and terpenoids 1–3 were evaluated against three human cancer cells (HepG2, PC-3, and HT-29), along with the human normal primary epidermal keratinocytes (HEKa) cells. With IC50 values ranging between 0.6 ± 0.04 and 5.0 ± 0.61 μg/mL against HepG2; 0.2 ± 0.01 and 11.9 ± 1.31 μg/mL against PC-3, and 0.04 ± 0.013 and 8.9 ± 0.97 μg/mL against HT-29, the total extract, and lactones 1–3 demonstrated cytotoxic effects. Compound 1 displayed the strongest impact on all cancer cells and a slightly safe effect on the normal cells HEKa. Compound 1 caused accumulation of HepG2 and HT-29 cells in G1 phase as displayed cell cycle analysis. On the other hand, the cell distributions were increased in the S phase in PC-3 cells. Furthermore, 1 caused apoptosis in PC-3 and HePG2 cells with 91.50%, and 79.72 %, respectively. A higher fraction of necrotic cells was observed in HT-29 cells amounting to 23.60%. These results suggested that the promising cytotoxicity exhibited by 1 is brought by the apoptosis induction in the cancer cells, which were evaluated. As the compounds showed antiproliferative effect against the HT-29 cells, the docking simulation was performed aiming at determining how they would interact with the EGFR enzyme, whose PDB: 4I23 is considered one of the two distinct wild types of EGFR enzymes. The antibacterial activity results revealed that 3 showed the most remarkable antibacterial effects, especially against the examined Gram-positive bacteria. The total extract exhibited potent activity against all examined bacteria. The total extract showed a potent antifungal effect against two Candida and two Aspergillus pathogens. The antioxidant activity revealed the potency of the total extract and 3 as antioxidant candidates. The obtained results refer to the importance of Centaurea pseudosinaica as a source of potent antiproliferative agents and the whole plant as an antipathogenic and antioxidant agent.

Diclofenac and Meloxicam Exhibited Anti-Virulence Activities Targeting Staphyloxanthin Production in Methicillin-Resistant Staphylococcus aureus

Staphylococcus aureus (S. aureus) is a worldwide leading versatile pathogen that causes a wide range of serious infections. The emergence of antimicrobial resistance against S. aureus resulted in an urgent need to develop new antimicrobials in the new era. The methicillin-resistant S. aureus (MRSA) prevalence in hospital and community settings necessitates the discovery of novel anti-pathogenic agents. Staphyloxanthin (STX) is a key virulence factor for the survival of MRSA against host innate immunity. The current work aimed to demonstrate the anti-virulence properties of meloxicam (MXM) as compared to diclofenac (DC), which was previously reported to mitigate the virulence of multidrug-resistant Staphylococcus aureus and test their activities in STX production. A total of 80 S. aureus clinical isolates were included, wherein a qualitative and quantitative assessment of STX inhibition by diclofenac and meloxicam was performed. The quantitative gene expression of STX biosynthetic genes (crtM, crtN and sigB) and hla (coded for α-hemolysin) as a virulence gene with and without DC and MXM was conducted, followed by molecular docking analysis for further confirmation. DC and MXM potently inhibited the synthesis of STX at 47 and 59 µg/mL to reach 79.3-98% and 80.6-96.7% inhibition, respectively. Treated cells also revealed a significant downregulation of virulence genes responsible for STX synthesis, such as crtM, crtN and global transcriptional regulator sigB along with the hla gene. Furthermore, computational studies unveiled strong interactions between the CrtM binding site and DC/MXM. In conclusion, this study highlights the potential role and repurposing of DC and MXM as adjuvants to conventional antimicrobials and as an anti-virulent to combat MRSA infections.

Tutorial review on the processing and performance of fabrics with antipathogenic inorganic agents.

Tutorial review on the processing and performance of fabrics with antipathogenic inorganic agents.

Visible light-regulated cationic polymer coupled with photodynamic inactivation as an effective tool for pathogen and biofilm elimination

BackgroundPathogenic microorganism pollution has been a challenging public safety issue, attracting considerable scientific interest. A more problematic aspect of this phenomenon is that planktonic bacteria exacerbate biofilm formation. There is an overwhelming demand for developing ultra-efficient, anti-drug resistance, and biocompatibility alternatives to eliminate stubborn pathogenic strains and biofilms.ResultsThe present work aims to construct a visible light-induced anti-pathogen agents to ablate biofilms using the complementary merits of ROS and cationic polymers. The photosensitizer chlorin e6-loaded polyethyleneimine-based micelle (Ce6-TPP-PEI) was constructed by an amphiphilic dendritic polymer (TPP-PEI) and physically loaded with photosensitizer chlorin e6. Cationic polymers can promote the interaction between photosensitizer and Gram-negative bacteria, resulting in enhanced targeting of PS and lethality of photodynamic therapy, and remain active for a longer duration to prevent bacterial re-growth when the light is turned off. As expected, an eminent antibacterial effect was observed on the Gram-negative Escherichia coli, which is usually insensitive to photosensitizers. Surprisingly, the cationic polymer and photodynamic combination also exert significant inhibitory and ablative effects on fungi and biofilms. Subsequently, cell hemolysis assessments suggested its good biocompatibility.ConclusionsGiven the above results, the platform developed in this work is an efficient and safe tool for public healthcare and environmental remediation.

Inhibitory activity and action mode of apple polyphenols against Peronophythora litchii that causes litchi downy blight

Litchi downy blight caused by Peronophythora litchii is one of the most devastating diseases in litchi fruit, and developing safe and effective anti-pathogenic agents is required. This study aimed to investigate the inhibitory effects and related mechanisms of apple polyphenols (AP), naturally occurring products, on P. litchii in vitro and in vivo. The results showed that AP inhibited mycelial growth and sporangia germination of P. litchii in vitro in dose-dependent manner. Moreover, plasma membrane integrity of P. litchii was severely damaged by AP treatment at 5 g L−1, which could account for the leakage of reducing sugar and soluble protein during incubation of pathogen. The destruction of P. litchii due to AP exposure was further confirmed by ultrastructural observation. Microscopic image displayed that AP induced the accumulation of reactive oxygen species (ROS) in P. litchii at early stage of treatment. Proteomic results exhibited that mitochondrion-related proteins in P. litchii were down-regulated by AP, which resulted in decreases in respiration rate and ATP production, consequently contributing to compromised pathogenicity of this pathogen. In vivo test demonstrated that 5 g L−1 AP delayed the disease development of litchi downy blight in P. litchii-inoculated litchi fruit. Suppression of disease in P. litchii-inoculated litchi fruit due to AP treatment was associated with reinforcement of host resistance, as indicated by enhanced activities of phenylalanine ammonia lyase (PAL) and β-1,3-glucanase (GLU), upregulated expressions of LcPAL and LcGLU and more accumulations of total phenolics and flavonoids in AP-treated fruit. The results suggest that AP application could ameliorate the occurrence of litchi downy blight by both the direct inhibition on P. litchii and the elicitation of resistance in litchi fruit.

In vivo, in vitro and molecular docking studies reveal the anti-virulence property of hispidulin against Pseudomonas aeruginosa through the modulation of quorum sensing

Pseudomonas aeruginosa is an audacious infectious agent involved in multiple persistent and incurable diseases in hosts through quorum sensing mediated pathways. Thus, compounds targeting quorum sensing (QS) can reduce the pathogenesis and virulence. The present study attempts to elucidate the QS inhibition properties of hispidulin against P. aeruginosa PAO1. Hispidulin (HPD) at its sub-inhibitory concentration (75 μg/ml) decreased violacein and pyocyanin pigment production of reporter bacteria and test bacteria to 81.92 ± 1.90 and 71.69 ± 3.46%, respectively. HPD supressed the virulence and biofilm development as similar to the positive control, baicalein. The pathogenesis of P. aeruginosa was effectively reduced in the infected worm model. The infected C. elegans showed 80.43% survival on the 6th day in presence of sub-MIC of HPD. In addition, HPD reduced the transcription of genes regulated by Las and Rhl networks including the receptor proteins and autoinducer producing genes which validated the anti-QS potential of the flavonoid. Computational studies revealed competitive binding of HPD with LasR protein and a weak interaction with RhlR. The results suggested the ability of HPD to block QS regulatory networks of P. aeruginosa. The potential lead obtained through this study can be utilized in the near future to design and develop anti-pathogenic agents to treat pseudomonal infections.

A Novel Antipathogenic Agent for Nonwoven Fabric

Medical-grade masks and N95 respirators containing non-woven fibers are designed to prevent the spread of airborne diseases. While they effectively trap respiratory droplets and aerosols, they cannot lyse entrapped pathogens. Embedded antimicrobial agents such as silver, copper, zinc, iodine, peptides, quaternary ammonium salts, or nanoparticles have been used to overcome this limitation. However, their effectiveness remains debatable because these materials can be toxins, allergens, irritants, and environmental hazards. Recently, silicon nitride (Si3N4) was found to be a potent antipathogenic compound, and it may be an ideal agent for masks. In powder or solid form, it is highly effective in inactivating bacteria, fungi, and viruses while leaving mammalian tissue unaffected. The purpose of this study was to serially assess the antiviral efficacy of Si3N4 against SARS-CoV-2 using powders, solids, and embedded nonwoven fabrics. Si3N4 powders and solids were prepared using conventional ceramic processing. The “pad-dry-cure” method was used to embed Si3N4 particles into polypropylene fibers. Fabric testing was subsequently conducted using industrial standards—ISO 18184 for antiviral effectiveness, ASTM F2299 and EN 13274-7 for filtration efficiency, EN 14683 for differential pressure drop, and ISO 18562-2 for particle shedding. A modification of ISO 18562-3 was also employed to detect ammonia release from the fabric. Antiviral effectiveness for Si3N4 powders, solids, and embedded fabrics were 99.99% at ≤ 5 min, ~ 93% in 24 h, and 87% to 92% in 120 min, respectively. Results of the standard mask tests were generally within prescribed safety limits. Further process optimization may lead to commercial Si3N4-based masks that not only “catch” but also “kill” pathogenic microbes.

Plant-virus-abiotic stress interactions: A complex interplay

Under field conditions, plants are subjected to a wide array of biotic and abiotic stresses. These are detrimental to the survival of plants and adversely affects global crop productivity. Changing climate has led to elevated temperatures and unpredicted whether patterns across the world leading to suboptimal crop performance. This is coupled by the emergence of novel pathogen strains which are resistant to anti-pathogenic agents. The situation is even worse in case of viruses where antiviral agents for controlling viral diseases in plants is lacking. The explosion of international trade has helped in the sharing of surplus resources from one location to the other and benefitted the economy of most countries however, this has also resulted in the spread of viruses and other pathogens. Recent years have seen a paradigm shift in the research methodology with combined stress gaining major attention instead of solitary stress. Viruses influence a plant’s response to various abiotic stresses, similarly, abiotic stress imposition has a great effect on viral disease progression. The recent developments associated with plant-virus-abiotic stress interactions along with the way forward to tackle such stresses has been discussed in the present review. • The interaction between plant, virus and abiotic stresses is less understood. • Viruses tend to show enhanced virulence during higher temperatures. • Plants infected with certain viruses are more tolerant to drought and cold stress. • The global spread of plant viruses along with the rapid climate change demands robust research in this area.

Celastrol mitigates staphyloxanthin biosynthesis and biofilm formation in Staphylococcus aureus via targeting key regulators of virulence; in vitro and in vivo approach

BackgroundStaphylococcus aureus is a leading cause of human infections. The spread of antibiotic-resistant staphylococci has driven the search for novel strategies to supersede antibiotics use. Thus, targeting bacterial virulence rather than viability could be a possible alternative.ResultsThe influence of celastrol on staphyloxanthin (STX) biosynthesis, biofilm formation, antibiotic susceptibility and host pathogenesis in S. aureus has been investigated. Celastrol efficiently reduced STX biosynthesis in S. aureus. Liquid chromatography-mass spectrometry (LC–MS) and molecular docking revealed that celastrol inhibits STX biosynthesis through its effect on CrtM. Quantitative measurement of STX intermediates showed a significant pigment inhibition via interference of celastrol with CrtM and accumulation of its substrate, farnesyl diphosphate. Importantly, celastrol-treated S. aureus was more sensitive to environmental stresses and human blood killing than untreated bacteria. Similarly, inhibition of STX upon celastrol treatment rendered S. aureus more susceptible to membrane targeting antibiotics. In addition to its anti-pigment capability, celastrol exhibits significant anti-biofilm activity against S. aureus as indicated by crystal violet assay and microscopy. Celastrol-treated cells showed deficient exopolysaccharide production and cell hydrophobicity. Moreover, celastrol markedly synergized the action of conventional antibiotics against S. aureus and reduced bacterial pathogenesis in vivo using mice infection model. These findings were further validated using qRT-PCR, demonstrating that celastrol could alter the expression of STX biosynthesis genes as well as biofilm formation related genes and bacterial virulence.ConclusionsCelastrol is a novel anti-virulent agent against S. aureus suggesting, a prospective therapeutic role for celastrol as a multi-targeted anti-pathogenic agent.