Pathogenic Gram-positive Bacteria Research Articles

Bioemulsifier from sponge-associated bacteria reduces staphylococcal biofilm

Biofilm formation is a major health concern and studies have been pursued to find compounds able to prevent biofilm establishment and remove pre-existing biofilms. While biosurfactants (BS) have been well-known for possessing antibiofilm activities, bioemulsifiers (BE) are still scarcely explored for this purpose. The present study aimed to evaluate the bioemulsifying properties of cell-free supernatants produced by Bacillaceae and Vibrio strains isolated from marine sponges and investigate their antiadhesive and antibiofilm activities against different pathogenic Gram-positive and Gram-negative bacteria. The BE production by the marine strains was confirmed by the emulsion test, drop-collapsing, oil-displacement, cell hydrophobicity and hemolysis assays. Notably, Bacillus cereus 64BHI1101 displayed remarkable emulsifying activity and the ultrastructure analysis of its BE extract (BE64-1) revealed the presence of structures typically observed in macromolecules composed of polysaccharides and proteins. BE64-1 showed notable antiadhesive and antibiofilm activities against Staphylococcus aureus, with a reduction of adherence of up to 100 % and a dispersion of biofilm of 80 %, without affecting its growth. BE64-1 also showed inhibition of Staphylococcus epidermidis and Escherichia coli biofilm formation and adhesion. Thus, this study provides a starting point for exploring the antiadhesive and antibiofilm activities of BE from sponge-associated bacteria, which could serve as a valuable tool for future research to combat S. aureus biofilms.

Biogenesis and Functionality of Sortase-Assembled Pili in Gram-Positive Bacteria.

A unique class of multimeric proteins made of covalently linked subunits known as pili, or fimbriae, are assembled and displayed on the gram-positive bacterial cell surface by a conserved transpeptidase enzyme named pilus-specific sortase. Sortase-assembled pili are produced by a wide range of gram-positive commensal and pathogenic bacteria inhabiting diverse niches such as the human oral cavity, gut, urogenital tract, and skin. These surface appendages serve many functions, such as molecular adhesins, immunomodulators, and virulence determinants, that significantly contribute to both the commensal and pathogenic attributes of producer microbes. Intensive genetic, biochemical, physiological, and structural studies have been devoted to unveiling the assembly mechanism and functions, as well as the utility of these proteins in vaccine development and other biotechnological applications. We provide a comprehensive review of these topics and discuss the current status and future prospects of the field.

Metabolomic analysis in Amycolatopsis keratiniphila disrupted the competing ECO0501 pathway for enhancing the accumulation of vancomycin.

Vancomycin is a clinically important glycopeptide antibiotic against Gram-positive pathogenic bacteria, especially methicillin-resistant Staphylococcus aureus. In the mutant strain of Amycolatopsis keratiniphila HCCB10007 Δeco-cds4-27, the production of ECO-0501 was disrupted, but enhanced vancomycin yield by 55% was observed compared with the original strain of A. keratiniphila HCCB10007. To gain insights into the mechanism of the enhanced production of vancomycin in the mutant strain, comparative metabolomics analyses were performed between the mutant strain and the original strain, A. keratiniphila HCCB10007 via GC-TOF-MS and UPLC-HRMS. The results of PCA and OPLS-DA revealed a significant distinction of the intracellular metabolites between the two strains during the fermentation process. 64 intracellular metabolites, which involved in amino acids, fatty acids and central carbon metabolism, were identified as differential metabolites. The high-yield mutant strain maintained high levels of glucose-1-phosphate and glucose-6-phosphate and they declined with the increases of vancomycin production. Particularly, a strong association of fatty acids accumulation as well as 3,5-dihydroxyphenylacetic acid and non-proteinogenic amino acid 3,5-dihydroxyphenylglycine (Dpg) with enhancement of vancomycin production was observed in the high-yield mutant strain, indicating that the consumption of fatty acid pools might be beneficial for giving rise to 3,5-dihydroxyphenylacetic acid and Dpg which further lead to improve vancomycin production. In addition, the lower levels of glyoxylic acid and lactic acid and the higher levels of sulfur amino acids might be beneficial for improving vancomycin production. These findings proposed more advanced elucidation of metabolomic characteristics in the high-yield strain for vancomycin production and could provide potential strategies to enhance the vancomycin production.

Diversity of endophytic bacteria with antimicrobial potential isolated from marine macroalgae from Yacila and Cangrejos beaches, Piura-Peru.

Endophytic bacteria found in marine macroalgae have been studied for their potential antimicrobial activity, consequently, they could serve as a valuable source of bioactive compounds to control pathogenic bacteria, yeasts, and fungi. Algae endophytic bacteria were isolated from Caulerpa sp., Ulva sp., Ahnfeltiopsis sp., and Chondracantus chamissoi from Yacila and Cangrejo Beaches (Piura, Peru). Antimicrobial assays against pathogenic bacteria were evaluated using cross-culture, over-plate, and volatile organic compound tests. Afterward, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of selected crude extracts were determined, also ITS molecular analysis, antifungal activity, and PCR of iturin, fengycin, and surfactin genes were performed for bacteria strains exhibiting better activity. Forty-six algae endophytic bacteria were isolated from algae. Ten strains inhibited gram-positive pathogenic bacteria (Enterococcus faecalis, Staphylococcus epidermidis, S. aureus, and Listeria monocytogenes), and 12 inhibited gram-negative bacteria (Escherichia coli and Salmonella enteric sv typhimurium). Bacteria with better activity belong to Bacillus sp., Kluyvera ascorbata, Pantoea agglomerans, Leclercia adecarboxylata, and Enterobacter sp., which only four showed antifungal activities against Candida albicans, C. tropicalis, Colletotrichium sp., Fusarium sp., Fusarium oxysporum, and Alternaria sp. Furthermore, K. ascorbata YAFE21 and Bacillus sp. YCFE4 exhibited iturin and fengycin genes. The results indicate that the algae endophytic bacteria found in this study, particularly K. ascorbata YAFE21, Bacillus sp. YCFR6, L. adecarboxylata CUFE2, Bacillus sp. YUFE8, Enterobacter sp. YAFL1, and P. agglomerans YAFL6, could be investigated as potential producers of antimicrobial compounds due to their broad activity against various microorganisms.

Vicia ervilia lectin (VEA) has an antibiofilm effect on both Gram-positive and Gram-negative pathogenic bacteria

Bacterial growing resistance to antibiotics poses a critical threat to global health. This study investigates, for the first time, the antibiofilm properties of Vicia ervilia agglutinin (VEA) from six different V. ervilia accessions against pathogenic bacteria, and the yeast Candida albicans. In the absence of antimicrobial properties, purified VEA significantly inhibited biofilm formation, both in Gram-positive and Gram-negative bacteria, but not in C. albicans. With an inhibitory concentration ranging from 100 to 500 µg/ml, the VEA antibiofilm activity was more relevant against the Gram-positive bacteria Streptococcus aureus and Staphylococcus epidermidis, whose biofilm was reduced up to 50% by VEA purified from accessions #5 and #36. VEA antibiofilm variability between accessions was observed, likely due to co-purified small molecules rather than differences in VEA protein sequences. In conclusion, VEA seed extracts from the accessions with the highest antibiofilm activity could represent a valid approach for the development of an effective antibiofilm agent.

Plant-induced bacterial gene silencing: a novel control method for bacterial wilt disease.

Ralstonia pseudosolanacearum, a notorious phytopathogen, is responsible for causing bacterial wilt, leading to significant economic losses globally in many crops within the Solanaceae family. Despite various cultural and chemical control strategies, managing bacterial wilt remains a substantial challenge. This study demonstrates, for the first time, the effective use of plant-induced bacterial gene silencing against R. pseudosolanacearum, facilitated by Tobacco rattle virus-mediated gene silencing, to control bacterial wilt symptoms in Nicotiana benthamiana. The methodology described in this study could be utilized to identify novel phytobacterial virulence factors through both forward and reverse genetic approaches. To validate plant-induced gene silencing, small RNA fractions extracted from plant exudates were employed to silence bacterial gene expression, as indicated by the reduction in the expression of GFP and virulence genes in R. pseudosolanacearum. Furthermore, treatment of human and plant pathogenic Gram-negative and Gram-positive bacteria with plant-generated small RNAs resulted in the silencing of target genes within 48 hours. Taken together, the results suggest that this technology could be applied under field conditions, offering precise, gene-based control of target bacterial pathogens while preserving the indigenous microbiota.

Genome assembly, comparative genomics, and identification of genes/pathways underlying plant growth-promoting traits of an actinobacterial strain, Amycolatopsis sp. (BCA-696)

The draft genome sequence of an agriculturally important actinobacterial species Amycolatopsis sp. BCA-696 was developed and characterized in this study. Amycolatopsis BCA-696 is known for its biocontrol properties against charcoal rot and also for plant growth-promotion (PGP) in several crop species. The next-generation sequencing (NGS)-based draft genome of Amycolatopsis sp. BCA-696 comprised of ~ 9.05 Mb linear chromosome with 68.75% GC content. In total, 8716 protein-coding sequences and 61 RNA-coding sequences were predicted in the genome. This newly developed genome sequence has been also characterized for biosynthetic gene clusters (BGCs) and biosynthetic pathways. Furthermore, we have also reported that the Amycolatopsis sp. BCA-696 produces the glycopeptide antibiotic vancomycin that inhibits the growth of pathogenic gram-positive bacteria. A comparative analysis of the BCA-696 genome with publicly available closely related genomes of 14 strains of Amycolatopsis has also been conducted. The comparative analysis has identified a total of 4733 core and 466 unique orthologous genes present in the BCA-696 genome The unique genes present in BCA-696 was enriched with antibiotic biosynthesis and resistance functions. Genome assembly of the BCA-696 has also provided genes involved in key pathways related to PGP and biocontrol traits such as siderophores, chitinase, and cellulase production.

Medical Device-Associated Infections Caused by Biofilm-Forming Microbial Pathogens and Controlling Strategies.

Hospital-acquired infections, also known as nosocomial infections, include bloodstream infections, surgical site infections, skin and soft tissue infections, respiratory tract infections, and urinary tract infections. According to reports, Gram-positive and Gram-negative pathogenic bacteria account for up to 70% of nosocomial infections in intensive care unit (ICU) patients. Biofilm production is a main virulence mechanism and a distinguishing feature of bacterial pathogens. Most bacterial pathogens develop biofilms at the solid-liquid and air-liquid interfaces. An essential requirement for biofilm production is the presence of a conditioning film. A conditioning film provides the first surface on which bacteria can adhere and fosters the growth of biofilms by creating a favorable environment. The conditioning film improves microbial adherence by delivering chemical signals or generating microenvironments. Microorganisms use this coating as a nutrient source. The film gathers both inorganic and organic substances from its surroundings, or these substances are generated by microbes in the film. These nutrients boost the initial growth of the adhering bacteria and facilitate biofilm formation by acting as a food source. Coatings with combined antibacterial efficacy and antifouling properties provide further benefits by preventing dead cells and debris from adhering to the surfaces. In the present review, we address numerous pathogenic microbes that form biofilms on the surfaces of biomedical devices. In addition, we explore several efficient smart antiadhesive coatings on the surfaces of biomedical device-relevant materials that manage nosocomial infections caused by biofilm-forming microbial pathogens.

Dual-recognition colorimetric platform based on porous Au@Pt nanozymes for highly sensitive washing-free detection of Staphylococcus aureus.

Adual-recognition strategy is reportedto construct a one-step washing and highly efficient signal-transduction tag system for high-sensitivity colorimetric detection of Staphylococcus aureus (S. aureus). The porous (gold core)@(platinum shell) nanozymes (Au@PtNEs) as the signal labels show highly efficient peroxidase mimetic activity and arerobust. For the sake of simplicity the detection involved the use of a vancomycin-immobilized magnetic bead (MB) and aptamer-functionalized Au@PtNEs for dual-recognition detection in the presence of S. aureus.In addition, we designed a magnetic plate to fit the 96-well microplate to ensure consistent magnetic properties of each well, which can quickly remove unreacted Au@PtNEs and sample matrix while avoiding tedious washing steps. Subsequently, Au@PtNEs catalyze hydrogen peroxide (H2O2) to oxidize 3,3',5,5'-tetramethylbenzidine (TMB) generating a color signal. Finally, the developed Au@PtNEs-based dual-recognition washing-free colorimetric assay displayed a response in the range of S. aureus of 5 × 101-5 × 105 CFU/mL, and the detection limit was 40 CFU/mL within 1.5 h. In addition, S. aureus-fortified samples were analyzed to further evaluate the performance of the proposed method, which yielded average recoveries ranging from 93.66 to 112.44% and coefficients of variation (CVs) within the range 2.72-9.01%. These results furnish a novel horizon for the exploitation of a different mode of recognition and inexpensive enzyme-free assay platforms as an alternative to traditional enzyme-based immunoassays for the detection of other Gram-positive pathogenic bacteria.

In vitro Evaluation of Antimicrobial Activity of Syzigium aromaticum (Clove) against Bacteria Isolated from Different Clinical Specimens in Shendi Town, Sudan

Background: Herbal medicinal products have been documented as a significant source for discovering new pharmaceutical molecules that have been used to treat serious diseases. It has been postulated that the geographical locations of the herbs affect the constituents of their essential oils and thus the degree of their antimicrobial action. Syzigium aromaticum (clove) is a traditional spice used as an antimicrobial agent and an alternative solution to increased antibiotic resistance by bacterial strains. Objective: This study aimed to study the in vitro antimicrobial activity of different clove concentrations against bacteria isolated from clinical specimens. Methods: This is a prospective cross-sectional study conducted in Shendi City, Sudan, from February to March 2023, at the Microbiology Laboratory, Faculty of Medical Laboratory Sciences. 50 samples were collected from urine and wounds, from which eight strains of pathogenic gram-positive and gram-negative bacteria were isolated and identified using gram stain and biochemical tests. Clove was tested using a 100%, 50%, 25%, and 12.5% concentration. Results: Out of 50 clinical specimens, standard strains were confirmed as S. aureus 13 (26%), S. epidermidis 7 (14%), E. faecalis 1 (2%), E. coli 15 (30%), Enterobacter 3 (6%), Citrobacter 2 (4%), K. pneumoniae 4 (8%), and P. aeruginosa 5 (10%). Clove showed remarkable antimicrobial activity against all clinical isolates and standard strains. Conclusion: The findings of this study showed that the aqueous extract of clove can exhibit high antimicrobial activity against all types of tested organisms, both clinical and standard. The findings indicate that, besides being safe and sensorial attractive, Clove has antimicrobial activity, making it an herbal antimicrobial agent.

Photocatalytic, Antimicrobial, and Cytotoxic Efficacy of Biogenic Silver Nanoparticles Fabricated by Bacillus amyloliquefaciens

The biomass filtrate of the endophytic bacterial strain Bacillus amyloliquefaciens Fa.2 was utilized for the eco-friendly production of silver nanoparticles (Ag-NPs). The yellowish-brown color’s optical properties showed a maximum surface plasmon resonance at 415 nm. The morphological and elemental composition analysis reveals the formation of spherical shapes with sizes of 5–40 nm, and the Ag ion comprises the major component of the produced Ag-NPs. X-ray diffraction confirmed the crystalline structure, whereas dynamic light scattering reveals the high stability of synthesized Ag-NPs with a polydispersity index of 0.413 and a negative zeta potential value. The photocatalytic experiment showed the efficacy of Ag-NPs to degrade methylene blue with maximum percentages of 73.9 ± 0.5 and 87.4 ± 0.9% under sunshine and UV irradiation, respectively, compared with 39.8% under dark conditions after 210 min. Additionally, the reusability of Ag-NPs was still more active for the fifth run, with a percentage decrease of 11.6% compared with the first run. Interestingly, the biogenic Ag-NPs showed superior antimicrobial activity against different pathogenic Gram-negative bacteria (MIC = 6.25 µg mL−1), Gram-positive bacteria (MIC = 12.5 µg mL−1), and uni- and multicellular fungi (MIC = 12.5 µg mL−1). Moreover, the biosynthesized Ag-NPs could target cancer cells (Pc3 and Mcf7) at low concentrations compared with normal cell (Vero) lines. The IC50 of normal cells is 383.7 ± 4.1 µg mL−1 compared with IC50 Pc3 (2.5 ± 3.5 µg mL−1) and McF7 (156.1 ± 6.8 µg mL−1). Overall, the bacterially synthesized Ag-NPs showed multifunctional features to be used in environmental catalysis and biomedical applications.

The Role of Bacterial Extracellular Vesicles in the Immune Response to Pathogens, and Therapeutic Opportunities.

Pathogenic bacteria have several mechanisms to evade the host's immune response and achieve an efficient infection. Bacterial extracellular vesicles (EVs) are a relevant cellular communication mechanism, since they can interact with other bacterial cells and with host cells. In this review, we focus on the EVs produced by some World Health Organization (WHO) priority Gram-negative and Gram-positive pathogenic bacteria; by spore-producing bacteria; by Mycobacterium tuberculosis (a bacteria with a complex cell wall); and by Treponema pallidum (a bacteria without lipopolysaccharide). We describe the classification and the general properties of bacterial EVs, their role during bacterial infections and their effects on the host immune response. Bacterial EVs contain pathogen-associated molecular patterns that activate innate immune receptors, which leads to cytokine production and inflammation, but they also contain antigens that induce the activation of B and T cell responses. Understanding the many effects of bacterial EVs on the host's immune response can yield new insights on the pathogenesis of clinically important infections, but it can also lead to the development of EV-based diagnostic and therapeutic strategies. In addition, since EVs are efficient activators of both the innate and the adaptive immune responses, they constitute a promising platform for vaccine development.

Correlation Analysis between STING Promoter Polymorphism and Susceptibility to Infection after Chemotherapy for Multiple Myeloma

To investigate the correlation between the stimulator of interferon genes (STING ) promoter polymorphism and the susceptibility to infection after chemotherapy for multiple myeloma. A total of 102 patients who had undergone chemotherapy for multiple myeloma in our hospital from January 2016 to July 2022 were selected. Depending on the presence or absence of infection after chemotherapy, the enrolled patients were divided into infection group (53 cases) and non-infection group (49 cases). The infection sites and distribution characteristics of pathogenic bacteria of the infection group were analyzed. The genotype distribution of STING gene promoter rs587777609 was compared between the two groups, and the risk factors of infection after chemotherapy for multiple myeloma were analyzed. For infection site, digestive system, respiratory system, urinary system, skin and mucous membranes accounted for 43.40%, 26.42%, 20.75%, and 9.43%, respectively. For pathogenic bacteria, Gram-negative bacteria, Gram-positive bacteria and fungi accounted for 57.14%, 26.98%, and 15.87%, respectively. The CC genotype frequency of STING gene rs587777609 locus in the infection group was lower than that in the non-infection group, while the TT genotype frequency was higher than that in the non-infection group (P < 0.05). The proportions of patients with diabetes, chronic obstructive pulmonary disease, renal insufficiency, serum albumin level< 35 g/L, ISS stage III, mechanical ventilation, and indwelling catheter in the infection group were higher than those in the non-infection group (P < 0.05). Multivariate logistic regression analysis showed that diabetes (OR =1.992), serum albumin level< 35 g/L (OR =2.782), ISS stage III (OR =2.707), mechanical ventilation (OR =3.031), and TT genotype (OR =2.401) were risk factors of infection after chemotherapy for multiple myeloma (P < 0.05). There is a correlation between STING promoter polymorphism and the susceptibility to infection after chemotherapy for multiple myeloma, and patients with TT genotype have a higher risk of infection.

Preparation and Effects of Manganese Oxide Nanoparticles Against Quinolone-Resistant Bacteria Isolated from Hospital Wastewater

Background: The widespread administration of quinolones may have led to an increase in bacterial resistance development. Objective: To synthesize and characterize manganese oxide nanoparticles (MnO2NPs) and evaluate their effects on the viability and biofilm formation of quinolone-resistant gram-positive and negative pathogenic bacteria. Methods: We prepared MnO2NPs using the photo-irradiation method and recorded their characteristics using XRD, TEM, and SEM. Staphylococcus aureus, Streptococcus pneumonia, Escherichia coli, Klebsiella pneumonia, and Pseudomonas aeruginosa were collected from the wastewater of Baghdad hospitals during the period from July 3rd to July 14th, 2023. We used the VITEK2 system to confirm and identify all of the isolates. We conducted biofilm formation and antibiotic susceptibility tests using nalidixic acid, ciprofloxacin, norfloxacin, aztreonam, levofloxacin, and ofloxacin, and also detected the qnrA and qnrB genes. Finally, we evaluated the effects of the prepared nanoparticles on the viability and biofilm formation of bacterial isolates. Results: MnO2NPs characterizations showed a diffraction peak at 2θ values with 21 nm average sizes; qnrA and qnrB genes were found in three and four isolates, respectively; and significant effects of MnO2NPs against viability and biofilm formation were recorded. Conclusions: The synthesized nanoparticles have antibacterial and anti-biofilm activities against a variety of bacteria possessing qnr genes. Even multi-resistant bacterial isolates have the potential to be strong antimicrobial agents against these pathogens.

Salvia coccinea Buc'hoz ex Etl. Leaf extract mediated synthesis of zinc oxide nanoparticles: Assessment of antimicrobial, antioxidant and anticancer activity

Salvia coccinea, a plant known for its medicinal properties, has been extensively utilized in biomedicine. In a recent study, green synthesizing of zinc oxide nanoparticles (ZnONPs) using the leaf extract of S. coccinea. The synthesized ZnONPs were thoroughly characterized using various techniques such as UV, FTIR, XRD, SEM with EDAX, TEM, particle size and Zeta potential analysis. The UV–vis analysis confirmed the successful synthesis of ZnONPs, as indicated by a distinct peak observed at 377 nm. FTIR spectra confirmed the various functional groups and molecular bonding interactions of the ZnONPs. XRD analysis revealed the crystalline nature of the nanoparticles. SEM imaging confirmed the predominantly spherical structure of the ZnONPs, while EDAX confirmed the presence of Zinc (Z) and Oxygen (O) elements. TEM imaging revealed their rod-like shape with an average size of approximately 5 nm. Particle size analysis indicated a size of 14.2 nm and the high zeta potential value of −17.3mv confirmed their stability. The synthesized ZnONPs exhibited antibacterial activity against both gram-positive and gram-negative pathogenic bacteria inhibitions. The antioxidant activity, as evidenced by DPPH and ABTS was highest inhibitions. Further evaluated the synthesized ZnONPs on human disease cell lines were also investigated from potential of anti-cancer properties in MCF-7 (68.96%) and A431 (64.73%). Overall, the findings of this study highlight the potential of the green synthesized ZnONPs as multifunctional agents with antibacterial, antioxidant and anticancer properties. These nanoparticles hold promise for applications in biomedicine, suggesting sustainable solutions for addressing various health related challenges.

Design, synthesis, and bioevaluation of novel unsaturated cyanoacetamide derivatives: In vitro and in silico exploration

In this study, we synthesized novel α,β-unsaturated 2-cyanoacetamide derivatives (1–5) using microwave-assisted Knoevenagel condensation. Characterization of these compounds was carried out using FTIR and 1H NMR spectroscopy. We then evaluated their in vitro antibacterial activity against both gram-positive and gram-negative pathogenic bacteria. Additionally, we employed in silico methods, including ADMET prediction and density functional theory (DFT) calculations of molecular orbital properties, to investigate these cyanoacetamide derivatives (1–5). Molecular docking was used to assess the binding interactions of these derivatives (1–5) with seven target proteins (5MM8, 4NZZ, 7FEQ, 5NIJ, ITM2, 6SE1, and 5GVZ) and compared them to the reference standard tyrphostin AG99. Notably, derivative 5 exhibited the most favorable binding affinity, with a binding energy of -7.7 kcal mol−1 when interacting with the staphylococcus aureus (PDB:5MM8), while also meeting all drug-likeness criteria. Additionally, molecular dynamics simulations were carried out to evaluate the stability of the interaction between the protein and ligand, utilizing parameters such as Root-Mean-Square Deviation (RMSD), Root-Mean-Square Fluctuation (RMSF), Radius of Gyration (Rg), and Principal Component Analysis (PCA). A 50 nanosecond molecular dynamics (MD) simulation was performed to investigate stability further, incorporating RMSD and RMSF analyses on compound 5 within the active binding site of the modeled protein across different temperatures (300, 305, 310, and 320 K). Among these temperatures, compound 5 exhibited an RMSD value ranging from approximately 0.2 to 0.3 nm at 310 K (body temperature) with the 5MM8 target, which differed from the other temperature conditions. The in silico results suggest that compound 5 maintained significant conformational stability throughout the 50 ns simulation period. It is consistent with its low docking energy and in vitro findings concerning α,β-unsaturated cyanoacetamides.Key insights from this study include:•The creation of innovative α,β-unsaturated 2-cyanoacetamide derivatives (1–5) employing cost-effective, licensed, versatile, and efficient software for both in silico and in vitro assessment of antibacterial activity.•Utilization of FTIR and NMR techniques for characterizing compounds 1–5.

Antimicrobial Activity and Phytochemical Characterization of Baccharis concava Pers., a Native Plant of the Central Chilean Coast.

Few sclerophyllous plants from the central coast of Chile have been systematically studied. This work describes the phytochemical composition and antimicrobial properties of Baccharis concava Pers. (sin. B. macraei), a shrub found in the first line and near the Pacific coast. B. concava has been traditionally used by indigenous inhabitants of today's central Chile for its medicinal properties. Few reports exist regarding the phytochemistry characterization and biological activities of B. concava. A hydroalcoholic extract of B. concava was prepared from leaves and small branches. Qualitative phytochemical characterization indicated the presence of alkaloids, steroids, terpenoids, flavonoids, phenolic, and tannin compounds. The antimicrobial activity of this extract was assessed in a panel of microorganisms including Gram-positive bacteria, Gram-negative bacteria, and pathogenic yeasts. The extract displayed an important antimicrobial effect against Gram-positive bacteria, Candida albicans, and Cryptococcus neoformans but not against Gram-negatives, for which an intact Lipopolysaccharide is apparently the determinant of resistance to B. concava extracts. The hydroalcoholic extract was then fractionated through a Sephadex LH-20/methanol-ethyl acetate column. Afterward, the fractions were pooled according to a similar pattern visualized by TLC/UV analysis. Fractions obtained by this criterion were assessed for their antimicrobial activity against Staphylococcus aureus. The fraction presenting the most antimicrobial activity was HPLC-ESI-MS/MS, obtaining molecules related to caffeoylquinic acid, dicaffeoylquinic acid, and quercetin, among others. In conclusion, the extracts of B. concava showed strong antimicrobial activity, probably due to the presence of metabolites derived from phenolic acids, such as caffeoylquinic acid, and flavonoids, such as quercetin, which in turn could be responsible for helping with wound healing. In addition, the development of antimicrobial therapies based on the molecules found in B. concava could help to combat infection caused by pathogenic yeasts and Gram-positive bacteria, without affecting the Gram-negative microbiota.

Wettability and Bactericidal Properties of Bioinspired ZnO Nanopillar Surfaces.

Nanomaterials of zinc oxide (ZnO) exhibit antibacterial activities under ambient illumination that result in cell membrane permeability and disorganization, representing an important opportunity for health-related applications. However, the development of antibiofouling surfaces incorporating ZnO nanomaterials has remained limited. In this work, we fabricate superhydrophobic surfaces based on ZnO nanopillars. Water droplets on these superhydrophobic surfaces exhibit small contact angle hysteresis (within 2-3°) and a minimal tilting angle of 1°. Further, falling droplets bounce off when impacting the superhydrophobic ZnO surfaces with a range of Weber numbers (8-46), demonstrating that the surface facilitates a robust Cassie-Baxter wetting state. In addition, the antibiofouling efficacy of the surfaces has been established against model pathogenic Gram-positive bacteria Staphylococcus aureus (S. aureus) and Gram-negative bacteria Escherichia coli (E. coli). No viable colonies of E. coli were recoverable on the superhydrophobic surfaces of ZnO nanopillars incubated with cultured bacterial solutions for 18 h. Further, our tests demonstrate a substantial reduction in the quantity of S. aureus that attached to the superhydrophobic ZnO nanopillars. Thus, the superhydrophobic ZnO surfaces offer a viable design of antibiofouling materials that do not require additional UV illumination or antimicrobial agents.

Nanowarriors from Mentha: Unleashing Nature's Antimicrobial Arsenal with Cerium Oxide Nanoparticles.

Medicinal plant-based cerium oxide nanoparticles (CeO2NPs) possessed excellent antimicrobial properties against multiple strains of Gram-positive and Gram-negative bacteria. The CeO2NPs are popular because their electropositive charged surface causes oxidation of plasma membrane and facilitates the penetration of CeO2NPs inside the pathogen body. In the present research work, CeO2NPs stabilized with Mentha leaf extract; as a result, nanoparticles surface-bonded with various functional groups of phytochemicals which enhanced the therapeutic potential of CeO2NPs. The inhibition percentage of CeO2NPs was evaluated against eight pathogenic Gram-positive bacteria Staphylococcus aureus and Streptococcus epidermidis; Gram-negative bacteria Escherichia coli, Stenotrophomonas maltophilia, Comamonas sp., Halobacterium sp., and Klebsiella pneumoniae; and plant bacteria Xanthomonas sp. The antifungal properties of CeO2NPs were evaluated against three pathogenic fungal species Bipolaris sorokiniana, Aspergillus flavus, and Fusarium oxysporum via the streak plate method. The antimicrobial inhibitory activity of CeO2NPs was good to excellent. The current research work clearly shows that three different medicinal plants Mentha royleana, Mentha longifolia, and Mentha arvensis based CeO2NPs, variation in nanoparticle sizes, and surface-to-volume ratio of green CeO2NPs are three factors responsible to generate and provoke antimicrobial activities of CeO2NPs against human pathogenic bacteria and plant infecting fungi. The results show that CeO2NPs possessed good antimicrobial properties and are effective to use for pharmaceutical applications and as a food preservative because of low toxicity, organic coating, and acceptable antimicrobial properties. This study showed a rapid and well-organized method to prepare stable phytochemical-coated CeO2NPs with three different plants M. royleana, M. longifolia, and M. arvensis with remarkable antibacterial and antifungal characteristics.

Immunomodulatory responses of extracellular vesicles released by gram-positive fish pathogen Streptococcus parauberis

Bacterial extracellular vesicles (BEVs) are nanosized structures that play a role in intercellular communication and transport of bioactive molecules. Streptococcus parauberis is a Gram-positive pathogenic bacterium that causes “Streptococcosis” in fish. In this study, we isolated S. parauberis-derived extracellular vesicles (SpEVs), and then physicochemical and immunomodulatory properties were determined to elucidate their biological functions. Initially, the biogenesis of SpEVs was detected using field emission scanning electron microscopy, which revealed that secretory phase SpEVs attached to the outer surface of S. parauberis. SpEVs had an average particle diameter and zeta potential of 168.3 ± 6.5 nm and −17.96 ± 2.11 mV, respectively. Field emission transmission electron microscopy analysis confirmed the presence of round or oval-shaped SpEVs with clear membrane margins. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis results showed three sharp protein bands when SpEVs were stained with Coomassie blue. In vitro toxicity of SpEVs was assayed using the murine macrophage RAW 264.7 cells and we observed no significant (p < 0.05) viability reduction up to 50 μg/mL qRT-PCR results revealed that SpEVs-treated (5 and 10 μg/mL) RAW 264.7 cells significantly (p < 0.05) induced the mRNA of proinflammatory (Il1β, Il6, and Tnfα) and anti-inflammatory (Il10) cytokines in a concentration-dependent manner. In vivo immunomodulatory effects of SpEVs were investigated by injecting SpEVs (5 and 10 μg/fish) into adult zebrafish. Transcriptional analysis based on qRT-PCR indicates significant (p < 0.05) upregulation of proinflammatory (il1β, il6, and tnfα) and anti-inflammatory (il10) genes in a concentration-dependent manner in zebrafish kidney. Further, protein expression results in zebrafish spleen tissue confirmed the immunomodulatory activity of SpEVs. In conclusion, SpEVs display the characteristics of BEVs and immunomodulatory activities, suggesting their potential application as vaccine candidate.