Tested Bacteria Strains Research Articles

Synthesis of N-Sulfopropylated Hyperbranched Polyethyleneimine with Enhanced Biocompatibility and Antimicrobial Activity.

Hyperbranched polyethyleneimine having 25,000 Da molecular weight was functionalized by a simple sulfopropylation reaction, affording a novel N-sulfopropylated PEI derivative (PEI-SO3 -). The successful introduction of N-sulfopropyl and sulfobetaine groups to the amino groups of PEI was spectroscopically confirmed. Furthermore, the antibacterial and anti-cyanobacterial activity of PEI-SO3 - in comparison to the parent PEI were investigated on two type heterotrophic bacteria, i. e., Gram (-) Escherichia coli and Gram (+) Staphylococcus Aureus bacteria, and one type of autotrophic cyanobacterium, i. e. Synechococcus sp. PCC 7942. Both PEI-SO3 - and PEI showed an enhanced, concentration-dependent antibacterial and anti-cyanobacterial activity against the tested bacteria strains, with PEI-SO3 - exhibiting higher activity than the parent PEI, signifying that the introduction of the sulfopropyl and sulfobetaine groups to the PEI amino groups enhanced the antibacterial and the anti-cyanobacterial properties of PEI. In the case of cyanobacteria, PEI-SO3 - was found to affect the integrity of the photosynthetic system by the inhibition of Photosystem-II electron transport activity. Cytocompatibility and hemocompatibility studies revealed that PEI-SO3 - exhibits high biocompatibility, suggesting that PEI-SO3 - could be considered as an attractive antibacterial and anti-cyanobacterial candidate for various applications in the disinfection industry and also against the harmful cyanobacterial blooms.

Antibacterial and antifungal activities of Moroccan wild edible plants selected based on ethnobotanical evidence

BackgroundDespite the extensive literature focusing on identifying novel antimicrobials of plant origin, little work has been undertaken to examine the antimicrobial activity of wild edible plants.ObjectiveThe current research aimed to determine the in vitro antimicrobial activity of methanolic extract of some common wild edible plants.Material and MethodsDisc diffusion and broth micro dilution methods were used to evaluate the antimicrobial activity of extracts of <i>Mercurialis annua</i>, <i>Ziziphys lotus</i>, <i>Rubia peregrina</i>, <i>Origanum vulgare</i>, <i>Papaver rhoeas</i>, <i>Foeniculum vulgare</i>, and <i>Dysphania ambrosioides</i> against known human microorganisms’ pathogens.ResultsThe result indicated that most of the extracts exhibited a range of <i>in vitro</i> growth inhibitory action against all bacterial strains and yeasts tested with inhibition zones ranging from 11 mm to 32 mm, MIC value ranging from 0.048 to 50 mg/ml and MBC and MFC values ranging from 0.048 to 100 mg/ml. Among the seven plant extracts tested, <i>O. vulgare</i> was the most effective showing high antimicrobial activity against all tested microbial strains. All plant extracts exhibited bactericidal activities against all the tested bacteria strains except for those of <i>R. peregrina</i>, <i>P. rhoeas</i> and <i>F. vulgare</i> which showed a bacteriostatic activity against <i>E. coli</i> and <i>Pseudomonas</i> sp. Antifungal activity was shown only by<i> O. vulgare</i>, <i>F. vulgare</i> and <i>D. ambrosioides</i> against both <i>C. albicans</i> and <i>C. neoformans</i>.ConclusionsThese findings highlight the potential of wild edible plants to control human pathogenic microbes and demonstrate that these plants could be used as starting points for the development of novel antimicrobial compounds.

Chemical composition, antioxidant, antimicrobial and antibiofilm activities of essential oil from the Moroccan endemic Plant, Calendula maroccana (Ball) B. D. Jacks.

The chemical characterization of the essential oil of the endemic Moroccan species, Calendula maroccana, was achieved by GC and GC-MS methods. The antioxidant, antimicrobial and antibiofilm activities of this essential oil were also studied. Eighty-one compounds were identified in the essential oil, representing 94.82% of the total. Sesquiterpenes predominate in the essential oil; 2-Methoxy-4-vinylphenol (16.13%), δ-amorphene (13.56%), α-cedrene (6.23%), γ-curcumene (5.10%) and α-bisabolol (4.94%) were the main constituents. The antioxidant potential was evaluated by DPPH, FRAP and ABTS assays: the essential oil exhibited antioxidant effectiveness with IC50 values of 0.92, 0.3 and 1.7 mg/mL, respectively. Moreover, the essential oil showed potent antimicrobial activity as revealed by inhibition zone values against selected clinically important pathogenic microorganisms. Inhibition zone values of 15.33 ± 0.19, 23 ± 0.05 and 15.33 ± 0.33 mm were observed against Staphylococcus aureus, Candida albicans and C. tropicalis, respectively. The maximal and minimal inhibition concentration values were in the range of 0.25 ± 0.17 - 4.68 ± 0.10 mg/mL for bacteria and 0.06 ± 0.03 - 0.12 ± 0.14 mg/mL, for Candida. The essential oil showed potent anti-biofilm activity with dual actions, inhibiting (69 - 88%) and eradicating (75 - 92%) the biofilms formed by the three tested bacteria strains. Based on these results, this essential oil can be considered as a natural antioxidant, antibacterial and antibiofilm agent that could be applied in phytotherapy, pharmaceutical and food sectors.

Pressure-Spun Fibrous Surgical Sutures for Localized Antibacterial Delivery: Development, Characterization, and In Vitro Evaluation.

Surgical sutures designed to prevent infection are critical in addressing antibiotic-resistant pathogens that cause surgical site infections. Instead of antibiotics, alternative materials such as biocides have been assessed for coating commercially used sutures due to emerging antibiotic resistance concerns worldwide. This study has a new approach to the development of fibrous surgical sutures with the ability to deliver localized antibacterial agents. A new manufacturing process based on pressure spinning was used for the first time in the production of fibrous surgical sutures by physically blending antibacterial triclosan (Tri) agent with poly(lactic-co-glycolic acid) (PLGA) and poly(ethylene oxide) (PEO) polymers. Fibrous surgical sutures with virgin PLGA, virgin PEO, different ratios of PLGA-PEO, and different ratios of Tri-loaded PLGA-PEO fibrous sutures were produced to mimic the FDA- and NICE-approved PLGA-based sutures available in the market and compared for their characteristics. They were also tested simultaneously with commercially available sutures to compare their in vitro biodegradation, antibacterial, drug release, and cytotoxicity properties. After in vitro antibacterial testing for 24 h, sutures having 285 ± 12 μg/mg Tri loading were selected as a model for further testing as they exhibited antibacterial activity against all tested bacteria strains. The selected model of antibacterial fibrous sutures exhibited an initial burst of Tri release within 24 h, followed by a sustained release for the remaining time until the sutures completely degraded within 21 days. The cell viability assay showed that these surgical sutures had no cytotoxic effect on mammalian cells.

Plant growth‐promoting rhizobacteria mediate soil hydro‐physical properties: An investigation with Bacillus subtilis and its mutants

AbstractPlant growth‐promoting rhizobacteria and other soil bacteria have the potential to improve soil hydro‐physical properties and processes through the production of extracellular polymeric substances (EPS). However, the mechanisms by which EPS mediates changes in soil properties and processes remain incompletely understood, partly due to variations in EPS composition produced under different environmental conditions. In this study, we investigated the influence of different bacterial traits on intrinsic soil properties and processes of evaporation and infiltration using sand treated with the wild‐type Bacillus subtilis variant (UD1022) and its two mutant variants, – and srf. The – mutant suppresses EPS production through alterations in the eps and tasA genes, while the srf mutant lacks the gene for surfactin production. Experimental results confirmed that the solution viscosity of the – mutant was the lowest and the solution surface tension of the srf mutant was the highest among the three tested bacteria strains. The distinct intrinsic properties of EPS produced by these bacterial strains resulted in varied hydro‐physical responses in the treated sand. Key influences included modifications in wettability, hydraulic decoupling (or mixed wettability), and aggregation, which collectively led to reduced evaporation rates and heterogeneous water distribution during infiltration in the bacteria‐treated sands. Our findings advance the understanding of the role bacterial EPS play in vadose zone hydrology and offer insights for the development of sustainable strategies for increasing water retention, supporting crop production in arid regions, and facilitating land restoration.

In Vitro Phytochemical, Antioxidant, and Antibacterial Evaluations of Various Extracts of Eleocharis dulcis (Burm.f.) Trin. ex Hensch

Eleocharis dulcis Burm.f. Trin. ex Hensch, has been empirically used in Chinese folk medicine to treat cough, laryngitis, hepatitis, enteritis, hypertension, and pharyngitis. The study is aimed to compare the phytochemical components, antioxidant and antibacterial activity of hexane (H), ethyl acetat (EA), and methanol extracts (MeOH) extracts obtained by Ultrasonic Assisted Extraction (UAE) method. Total Phenolic Content (TPC) was determined by the Folin-Ciocalteu method and Total Flavonoid Content (TFC) by quercetin method. Antioxidants activity using the DPPH, ABTS, and FRAP method. The inhibition zone of antibacterial activity using the disc diffusion method and Minimum Inhibitory Concentration with microdilution method. Results of the extracts’ total phenolic and flavonoid contents showed that EA has a higher content of these phytochemicals. The EA also exhibited a higher zone of inhibition for each concentration against Aeromonas hydrophila (AHA), Aeromonas salmonicida (AS), and Streptococcus agalactiae (SA). The MIC of EA against AHA and AS was 6.25 mg/mL and 3.125 mg/mL, respectively. Allextracts were effective against SA with MIC of 1.5625 mg/mL. Similarly, the EA extract showed better ntibacterial activity against all the tested bacteria strains than the H and MeOH extracts. Also, the EA extract exhibited better antioxidant activity compared to others, with IC50 values of 52.830 ± 0.271 ppm, 16.923 ± 0.047 ppm and 198.504 ± 1.490 µmol/g in the DPPH, ABTS and FRAP assays, respectively. The study concludes that the EA extract of E. dulcis possesses better antibacterial and antioxidant activities.

Transformation of sulfur and nitrogen compounds by sulfidogenic and phototrophic bacteria under the influence of sodium fluoride and potassium bromide

Anthropogenically altered media are characterized by complex pollution, which contains a wide range of organic and inorganic pollutants, including halogen compounds. The influence of halides on transformed ecosystems, in particular, on their sulfidogenic and photosynthetic microbiota and its properties, remains insufficiently studied. The influence of sodium fluoride and potassium bromide at concentrations that are equal and 0.5–4.0 times differed from the maximum permissible concentrations (MPC) (MPC of fluorides and bromides are 0.0789 and 0.0025 mM, respectively) on the reduction of sulfate ions or sulfur (3.47 mM) by sulfidogenic bacteria of Desulfovibrio and Desulfuromonas genera, as well as on the use of thiosulfate or nitrite ions (4.167 mM) as electron donors of anoxygenic photosynthesis by phototrophic purple and green sulfur bacteria of Thiocapsa, Lamprocystis and Chlorobium genera, isolated from the Yavorivske Lake, was investigated. The biomass of bacteria was determined by the turbidimetric method, the content of H2S, SO42-, NО2ˉ and NО3ˉ in the cultural liquid – by the spectrophotometric method, the concentration of S2O32- – by the titrometric method. The intracellular glucose and glycogen content was determined enzymatically in cell-free extracts, using the analytical kit “Diagluc-2”. It was found that sodium fluoride and potassium bromide at concentrations 3.0–4.0 times higher than the MPC repress the biomass accumulation by bacteria Desulfovibrio sp. in the medium with sulfates 2.7−5.8 and 2.1−4.2 times, respectively, and inhibit the hydrogen sulfide production by them 1.8−3.4 and 2.0−3.2 times, respectively. NaF and KBr at concentrations that are equal and 2.0–4.0 times higher than the MPC repress the biomass accumulation by bacteria Desulfuromonas sp. in the medium with sulfur 2.2–6.9 and 2.1–5.6 times, respectively, and at concentrations 3.0–4.0 times higher than the MPC inhibit the hydrogen sulfide production by bacteria 1.9−3.7 and 2.0−2.7 times, respectively. Sodium fluoride and potassium bromide at concentration that 4.0 times exceeded the MPC inhibit the biomass accumulation by bacteria of Thiocapsa, Lamprocystis and Chlorobium genera in the medium with thiosulfates 2.0–2.3 and 1.7–2.0 times, respectively, reduce thiosulfate ions oxidation by them by 31.9–38.5 and 27.1–33.7%, respectively, compared to the control, but stimulate glycogen synthesis by cells of green sulfur bacteria by 106.7 and 64.0%, respectively. NaF and KBr at concentration 4.0 times higher than the MPC inhibit the biomass accumulation by phototrophic bacteria in the medium with nitrites 2.1−2.4 and 1.8−1.9 times, respectively, slow down nitrite ions oxidation by bacteria by 23.5–26.1 and 17.1–20.1%, respectively, compared to the control, but stimulate glycogen synthesis by cells of green sulfur bacteria by 134.7 and 115.0%, respectively. Glycogen content in Chlorobium limicola IMV K-8 cells grown in the media with Na2S2O3 or NaNO2 and NaF at concentration that 4.0 times exceeded the MPC was 81.33 and 84.13 mg/g of dry weight of cells, respectively. Fluoride ions showed a greater toxic effect on bacteria than bromide ions. The resistance of all tested bacteria strains to inorganic pollutants at high concentrations indicates their high biotechnological potential.

Phytochemical Analysis and Antibacterial Activity of Achillea coarctata Poir. Essential Oils.

Essential oils obtained from different parts of Achillea coarctata species (inflorescences, stem and leaves and the whole aerial part) collected on four different locations in Serbia have been investigated to evaluate the chemical composition and antibacterial activity of isolated oils. The aim of this study was to determine differences in the chemical composition of essential oils obtained from different plant parts and how different type of substrate as well as different climate conditions affect the chemical composition of essential oils. Oxigenated terpenes were reported to be the major constituents in almost all examinated samples with 1,8-cineole, caryophyllene oxide and cis-cadin-4-en-7-ol identified as dominant compounds. Disk diffusion assay was used to determine antibacterial activity against two Gram-positive (Bacillus subtilis subsp. spizizenii ATCC 6633 and Staphylococcus aureus ATCC 6538) and three Gram-negative bacteria (Escherichia coli ATCC 8739, Pseudomonas aeruginosa ATCC 9027 and Salmonella abony ATCC 6017). The obtained results showed that essential oils obtained from A. coarctata exhibit significant antibacterial activity against tested bacteria strains. The best inhibitory effect was observed against S. aureus, while on the other hand P. aeruginosa showed high level of resistance to almost all examined essential oils.

Chemical profile of Nepeta cataria L. var. citriodora (Becker) essential oil and in vitro evaluation of biological activities

Essential oil (EO) obtained by hydrodistillation in a Clevenger-type apparatus from aerial parts of Nepeta cataria L. var. citriodora (Becker), cultivated in Serbia was subjected to gas chromatography-mass spectroscopy (GC-MS) to determine the composition. Furthermore, N. cataria var. citriodora essential oil wastested to determine its antimicrobial, antioxidant, antihyperglycemic and anti-inflammatory activities in vitro.The antimicrobial activity was tested by broth microdilution method against 16 bacterial strains from American Type Culture Collection (ATCC). Four common tests for measuring in vitro antioxidant activity were used: 2, 2-diphenyl-1-picrylhydrazyl assay (DPPH), reducing power (RP), 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and β-carotene bleaching assay (BCB). Antihyperglycemic activity was examined by using α-glucosidase inhibitory potential (AHgA), while anti-inflammatory activity (AIA) was determined by protein denaturation bioassay, using egg albumin. In total, 36 compounds were isolated and detected by GC-MS technique in N. cataria var. citriodora EO. The EO is mainly comprised of oxygenated monoterpenes (93.1%), and the main compounds were two monoterpenoid alcohols, nerol (38.5%) and geraniol (24.9%), followed by two aliphatic aldehyde, geranial (14.6%) and neral (11.0%). Antimicrobial activity of this EO shows growth inhibition of all tested bacteria strains, and exhibited good antioxidant, antihyperglycemic and anti-inflammatory activities. The EO obtained from N. cataria var. citriodora grown in Serbia shows valuable biological activity, indicating its potential for use as a supplement in everyday diet and as a natural preservative in food industry.

Chemical Composition, Antioxidant, Antibacterial, and Antibiofilm Activities of Backhousia citriodora Essential Oil.

The essential oil of Backhousia citriodora, commonly known as lemon myrtle oil, possesses various beneficial properties due to its richness in bioactive compounds. This study aimed to characterize the chemical profile of the essential oil isolated from leaves of Backhousia citriodora (BCEO) and its biological properties, including antioxidant, antibacterial, and antibiofilm activities. Using gas chromatography–mass spectrometry, 21 compounds were identified in BCEO, representing 98.50% of the total oil content. The isomers of citral, geranial (52.13%), and neral (37.65%) were detected as the main constituents. The evaluation of DPPH radical scavenging activity and ferric reducing antioxidant power showed that BCEO exhibited strong antioxidant activity at IC50 of 42.57 μg/mL and EC50 of 20.03 μg/mL, respectively. The antibacterial activity results showed that BCEO exhibited stronger antibacterial activity against Gram-positive bacteria (Staphylococcus aureus and Staphylococcus epidermidis) than against Gram-negative bacteria (Escherichia coli and Klebsiella pneumoniae). For the agar disk diffusion method, S. epidermidis was the most sensitive to BCEO with an inhibition zone diameter of 50.17 mm, followed by S. aureus (31.13 mm), E. coli (20.33 mm), and K. pneumoniae (12.67 mm). The results from the microdilution method showed that BCEO exhibited the highest activity against S. epidermidis and S. aureus, with the minimal inhibitory concentration (MIC) value of 6.25 μL/mL. BCEO acts as a potent antibiofilm agent with dual actions, inhibiting (85.10% to 96.44%) and eradicating (70.92% to 90.73%) of the biofilms formed by the four tested bacteria strains, compared with streptomycin (biofilm inhibition, 67.65% to 94.29% and biofilm eradication, 49.97% to 89.73%). This study highlights that BCEO can potentially be a natural antioxidant agent, antibacterial agent, and antibiofilm agent that could be applied in the pharmaceutical and food industries. To the best of the authors’ knowledge, this is the first report, on the antibiofilm activity of BCEO against four common nosocomial pathogens.

Bioassay's Directed Isolation-Structure Elucidation and Molecular Docking of Triterpenes from Persea duthiei against Biologically Important Microbial Proteins.

The research work presented in this study is mainly concerned with the bioactivity-directed phytochemical and biological evaluation of Persea duthiei. Persea duthiei is a typical medicinal plant used to treat a variety of ailments such as asthma, edema, and bronchitis. Ethyl acetate, n-hexane, n-butanol, and compounds that are soluble in water were used to examine the antibacterial as well as antifungal capacities of the plant. The antibacterial activity of the soluble parts of ethyl acetate and n-hexane against Escherichia coli, Staphylococcus aureus, Salmonella typhi, and Bacillus subtilis was high, even though there was no activity against Pseudomonas aeruginosa. Likewise, the n-hexane and ethyl acetate fractions were found to have substantial efficacy against several fungal strains such as Aspergillus flavus, Aspergillus fumigates, Fusarium solani, and Aspergillus niger, but not against Candida glabrata. Among the studied fractions, the ethyl acetate soluble fraction had potent antibacterial activity against all of the tested species. This fraction was submitted to phytochemical analysis utilizing various chromatographic methods for the extraction of various pure components. As a consequence, four compounds were isolated, and their structures were elucidated using various spectroscopic methods such as IR, EIMS, HR-EIMS, 1H-NMR, 13C-NMR, NOESY, COSY, HMBC, and HMQC. Urs-12-en-3β-ol (α-amyrine) (1), Urs-12-ene-2α-3β-diol (chamaedrydiol) (2), 3β-hydroxyurs-12-en-28-aldehyde (ursolic aldehyde) (3), and 12-oleanex-3β-ol (β-amyrine) (4) were extracted. Compounds 1, 2, 3, and 4 were examined for antibacterial and antifungal activity and found to have zones of inhibition ranging from 0 to 11 mm against tested bacteria strains and percent inhibition ranging from 0 to 25 percent against fungus strains. Compounds 1 and 4 showed strong efficacy against the investigated fungal species, with a 25% inhibition rate. In the case of antibacterial activity, compounds 4 and 1 showed potent activity with zones of inhibition of 11 mm and 10 mm, respectively. Compounds 2 and 3 were observed to have nonsignificant antimicrobial activity. However, docking studies reflected the complex formation of compound 1 with beta-hydroxyacyl-ACP dehydratase HadAB and S. aureus tyrosyl-tRNA synthetase and compound 2 with topoisomerase II DNA gyrase complex, and they were reported to have antibacterial properties. Similarly, compound 4 was discovered to be well compatible with the lanosterol 14-demethylase (fungal enzyme) and is thus regarded as having antifungal capabilities. Chimera software was used to identify the binding pockets of these complexes. These results indicated that Persea duthiei is a valuable source of medicinal compounds for medication development.

Bacterial Outer Membrane Permeability Increase Underlies the Bactericidal Effect of Fatty Acids From Hermetia illucens (Black Soldier Fly) Larvae Fat Against Hypermucoviscous Isolates of Klebsiella pneumoniae.

Behind expensive treatments, Klebsiella pneumoniae infections account for extended hospitalization’s high mortality rates. This study aimed to evaluate the activity and mechanism of the antimicrobial action of a fatty acid-containing extract (AWME3) isolated from Hermetia illucens (HI) larvae fat against K. pneumoniae subsp. pneumoniae standard NDM-1 carbapenemase-producing ATCC BAA-2473 strain, along with a wild-type hypermucoviscous clinical isolate, strain K. pneumoniae subsp. pneumoniae KPi1627, and an environmental isolate, strain K. pneumoniae subsp. pneumoniae KPM9. We classified these strains as extensive multidrug-resistant (XDR) or multiple antibiotic-resistant (MDR) demonstrated by a susceptibility assay against 14 antibiotics belonging to ten classes of antibiotics. Antibacterial properties of fatty acids extracted from the HI larvae fat were evaluated using disk diffusion method, microdilution, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), half of the inhibitory concentration (MIC50), and bactericidal assays. In addition, the cytotoxocity of AWME3 was tested on human HEK293 cells, and AWME3 lipid profile was determined by gas chromatography-mass spectrometry (GC-MS) analysis. For the first time, we demonstrated that the inhibition zone diameter (IZD) of fatty acid-containing extract (AWME3) of the HI larvae fat tested at 20 mg/ml was 16.52 ± 0.74 and 14.23 ± 0.35 mm against colistin-resistant KPi1627 and KPM9, respectively. It was 19.72 ± 0.51 mm against the colistin-susceptible K. pneumoniae ATCC BAA-2473 strain. The MIC and MBC were 250 μg/ml for all the tested bacteria strains, indicating the bactericidal effect of AWME3. The MIC50 values were 155.6 ± 0.009 and 160.1 ± 0.008 μg/ml against the KPi1627 and KPM9 isolates, respectively, and 149.5 ± 0.013 μg/ml against the ATCC BAA-2473 strain in the micro-dilution assay. For the first time, we demonstrated that AWME3 dose-dependently increased bacterial cell membrane permeability as determined by the relative electric conductivity (REC) of the K. pneumoniae ATCC BAA-2473 suspension, and that none of the strains did not build up resistance to extended AWME3 treatment using the antibiotic resistance assay. Cytotoxicity assay showed that AWME3 is safe for human HEK293 cells at IC50 266.1 μg/ml, while bactericidal for all the strains of bacteria at the same concentration. Free fatty acids (FFAs) and their derivatives were the significant substances among 33 compounds identified by the GC-MS analysis of AWME3. Cis-oleic and palmitoleic acids represent the most abundant unsaturated FAs (UFAs), while palmitic, lauric, stearic, and myristic acids were the most abundant saturated FAs (SFAs) of the AWME3 content. Bactericidal resistant-free AWM3 mechanism of action provides a rationale interpretations and the utility of HI larvae fat to develop natural biocidal resistance-free formulations that might be promising therapeutic against Gram-negative MDR bacteria causing nosocomial infections.

ANTAGONISTIC ACTIVITY OF IMMOBILIZED PROBIOTICS STORED AT LOW TEMPERATURES

The results presented in this article contribute to the research devoted to the development of technologies for the long-term storage of probiotic cells immobilized in gel carriers. The purpose of this study is to investigate the antagonistic activity of probiotic strains of microorganisms immobilized in alginate gel without additives and with the addition of cryoprotective components after the storage at different low temperatures. Objects and methods. Probiotic strains of Escherichia coli M-17 (E. coli M-17), Lactobacillus acidophilus IMB B-2637 (L. acidophilus), Saccharomyces cerevisiae IMB Y-505 (S. cerevisiae) were immobilized in granules of 1% alginate gel without additives and with the addition of lactose (10%), sucrose (10%), LSM protective medium (final concentration in the gel of lactose was 1%, sucrose 5%, skimmed milk 5% v/v). To temperatures of -20, -40, -75°C, the sample freezing was performed at -20, -40, -75°C in freezing cabinets. The samples kept at -196°C, were first cooled to -40°C at a rate of 1 deg/min, and then transferred into liquid nitrogen. The samples were stored at this temperature regimen for 24 months. The samples were allowed to thaw in a water bath at 30°C. The granules were dissolved in a 4% EDTA solution. Cell viability was determined by the Koch "cup" method according to the ability to colony formation. The antagonistic activity of E. coli M-17 and L. acidophilus against test strains of bacteria was studied by the method of delayed antagonism. The antagonistic activity of S. cerevisiae against all test strains (bacteria and C. albicans) and the antagonistic activity of E. coli M-17 against the test strain C. albicans were studied by a modified method using a two-layer medium with the determination of the minimum inhibitory concentration. It was established that immobilization in alginate gel without additives and with the addition of cryoprotective components and storage for 24 months at temperatures of -20, -40, -75, -196°C did not affect the spectrum and severity of the antagonistic action of probiotics. This indicates that immobilization in a gel and storage at low temperatures do not cause damage in viable cells to genetic structures that determine chemical and biochemical reactions, which products provide the antagonistic probiotic effects.

Design, synthesis and biological evaluation of novel diazaspirodecanone derivatives containing piperidine-4-carboxamide as chitin synthase inhibitors and antifungal agents

A series of novel 2-oxo-(1-oxo-2,8-diazaspiro[4.5]decane-8-yl)ethylpiperidine carboxamide derivatives were designed, synthesized and characterized by 1H NMR, 13C NMR and HRMS spectroscopy. All eighteen newly prepared compounds were evaluated for their inhibition against chitin synthase (CHS) and antifungal activities in vitro. The enzyme assay revealed that compound 5h showed excellent inhibitory activity against CHS with IC50 value of 0.10 mM, and the compounds 5b, 5d and 5q showed good inhibition against chitin synthase with IC50 values of 0.13 mM, 0.18 mM and 0.15 mM, respectively, while IC50 value of ployoxin B was 0.08 mM. Meanwhile, the others of these compounds exhibited moderate inhibition potency against chitin synthase. The antifungal assay showed compound 5h had excellent antifungal activity compared with the control drugs fluconazole and polyoxin B against these tested strains including C. albicans, A. fumigatus, C. neoformans and A. flavus. Its excellent antifungal activity was consistent with its excellent chitin synthase inhibition. Compound 5k and 5l against C. albicans were comparable with fluconazole, and they showed strong antifungal potency against A. flavus with MIC values of 0.07 mmol/L and 0.13 mmol/L respectively. Compound 5m had similar MIC value against A. fumigatus to fluconazole. The phenomenon that compounds 5b, 5d and 5q that showed good enzymatic inhibition didn’t exert good antifungal activity, while compounds 5k, 5l and 5m that showed moderate chitin synthase inhibition exhibited excellent antifungal activity was discussed. Furthermore, the trial of drug combination showed that compounds had synergistic effects or additive effects with fluconazole against tested fungi which also verified that these designed compounds targeted different targets from that of fluconazole. Additionally, the antibacterial trial showed that all synthesized compounds had little potency against tested bacteria strains. These results indicated that the designed compounds were potential chitin synthase inhibitors and had selectively antifungal activities.

Botanicals and phytochemicals from the bark of Hypericum roeperianum (Hypericaceae) had strong antibacterial activity and showed synergistic effects with antibiotics against multidrug-resistant bacteria expressing active efflux pumps

Ethnopharmacological relevanceInfections due to multidrug-resistant (MDR) bacteria constitute a real problem in the public health worldwide. Hypericum roeperianum Schimp. ex A. Rich (Hypericaceae) is used traditionally for treatment of various ailments such as abdominal pains, constipation, diarrhea, indigestion, nausea, and bacterial diseases. Aim of the studyThis study was aimed at investigating the antibacterial and antibiotic-modifying activity of the crude methanol extracts (HRB), ethyl-acetate soluble fraction (HRBa), residual material (HRBb), and 11 compounds from the bark of Hypericum roeperianum against multi-drug resistant (MDR) bacteria expressing active efflux pumps. Materials and methodsThe antibacterial activity, the efflux pump effect using the efflux pump inhibitor (EPI), phenylalanine-arginine-ß-naphthylamide (PAβN), as well as the antibiotic-modifying activity of samples were determined using the broth micro-dilution method. Spectrophotometric methods were used to evaluate the effects of HRB and 8,8-bis(dihydroconiferyl) diferulate (11) on bacterial growth, and bacterial membrane damage, whereas follow-up of the acidification of the bacterial culture was used to study their effects on bacteria proton-ATPase pumps. ResultsThe crude extract (HRB), HRBa, and HRBb had selective antibacterial activity with MICs ranging from 16 to 512 μg/mL. Phytochemical 11 displayed the best antibacterial activity (0.5 ≤ MIC ≤ 2 μg/mL). The activity of HRB and 11 in the presence of EPI significantly increased on the tested bacteria strains (up to 32-fold). The activity of cloxacillin (CLO), doxycycline (DOX), and tetracycline (TET), was considerably improved (up to 64-fold) towards the multidrug-resistant Enterobacter aerogenes EA-CM64 strain. The crude extract (HRB) and 11 induced the leakage of bacterial intracellular components and inhibited the proton-ATPase pumps. ConclusionsThe crude extract (HRB) and 8,8-bis(dihydroconiferyl)diferulate from the bark of Hypericum roeperianum are good antibacterial candidates that deserve further investigations to achieve antibacterial drugs to fight infections involving MDR bacteria.

Cobalt(II) Complexes of (E)-2-(2-Hydroxy-3-methoxybenzalidene)hydrazinecarbo(thio)amides: Synthesis, FT-IR studies and their antimicrobial activity

In this present work, six new Co(II) complexes {1-6, [Co(L3)] (1); [Co(L2)] (2); [Co(L1)] (3); [Co(L2)(L3)] (4); [Co(L1)(L2)] (5); [Co(L1)(L3)] (6)} of (E)-2-(2-hydroxy-3-methoxybenzalidene)-N4-methylhydrazinecarbothioamide (HL1), (E)-2-(2-hydroxy-3-methoxybenzalidene)-hydrazinecarbothioamide (HL2) and (E)-2-(2-hydroxy-3-methoxybenzalidene)-hydrazinecarboamide (HL3), have been synthesized and characterized by elemental analysis, analytical and FT-IR spectral investigations. The FT-IR spectral data advocated the attachment of Co2+ ion to the Schiff's base ligand moiety through the azomethine nitrogen, thioketonic sulfur and phenolic-O atom. The synthesized complexes 1-6 were screened for their antibacterial activities in contradiction of on two gram-positive bacteria (Bacillus subtilis and Escherichia coli) and two gram-negative bacteria (Pseudomonas aeruginosa and Staphylococcus aureus) and also screened for their antifungal in contradiction of Aspergillus Niger and Candida Albicans. Those complexes showed reasonable to substantial inhibitory effect on tested bacteria strains, whereas they exposed an admirable inhibitory effect on tested fungal strains.

Antimicrobial and antimycotic activity of some derivatives of 3-arylpyridin-2-one and 3-arylpyran-2-one

2-Pyridones and 2-pyrones are a well-known heterocyclic compounds having significant biological and medical application. The molecular structures and various activities of 2-pyridone derivatives as well as their syntheses and natural occurrence are analyzed and discussed. Previously, we developed an effective method for the synthesis of 3-aryl-substituted derivatives of 2-pyranone. This method consists in the interaction of commercially available starting reagents with comercially available arenediazonium salts via the Meerwein reaction conditions. In this paper, we report on an effective method for the synthesis of 3-arylpyridin-2-ones starting from 3-arylpyranones. Reaction of methyl or ethyl esters of 4,6-dimethyl-3-aryl-2-oxo-2 H -5-pyrancarboxylic acids with ammonium acetate in acetic acid gave methyl or ethyl esters of 2,4-dimethyl-6-oxo-5-aryl-1,6-dihydropyridine-3-carboxylic acids in high yields. For some compounds (ethyl 4,6-dimethyl-3-(2-nitrophenyl)-2-oxo-2 H -pyran-5-carboxylate ( 1c ), ethyl 2,4-dimethyl-5-(4-nitrophenyl)-6-oxo-1,6-dihydropyridine-3-carboxylate ( 2c ), 6-methyl-3-(3-nitrophenyl)-2-oxo-2 H -pyran-5-carboxylic acid ( 5 ), 4-methyl-6-(2-methylprop-1-en-1-yl)-3-(4-nitrophenyl)-2 H -pyran-2-one ( 6 ), methyl 4,6-dimethyl-3-(2-nitrophenyl)-2-oxo-2 H -pyran-5-carboxylate ( 7 )) we investigated antifungal and antimicrobial activity. The antimicrobial activity of the obtained compounds ( 1c , 2c , 5 , 6 , 7 ) was studied by a micromethod using disposable 96-well sterile polystyrene tablets and Takachi microtiters. The test strains of bacteria were grown for 18–20 h on beveled meat-peptone agar (MPA) at a temperature of +37 ºС. The highest activity, especially of compound 6 , was found against "true" fungi ‑ strain № 7 (S. cerevisiae 61). Compounds 5 and 6 act on strain B. subtilis ATCC6633 at a concentration of 31.3 μg/ml. Keywords: pyran-2-one, pyridin-2-one, recyclization, antimicrobial activity, antifungal activity.

Physical, mechanical and microbiological characteristics of the first domestic base material hybrid polymerization

The negative impact of the residual acrylic monomer present in dental polymethyl methacrylates (PMMA), the high cost of monomer-free thermoplastic polymers, contribute to the spread of the domestic base material of light polymerization “Nolatek” (VladMiva, Russia). However, various data on the physical and mechanical properties of the material and the methods of polymerization limit its application. The purpose and objectives of our study was to study the strength characteristics of the material “Nolatek” polymerized in various ways, followed by the study of adhesion of test strains of bacteria and fungi to it. Materials and methods. We have carried out bending tests on samples made of “Nolatek” material polymerized using various technologies, as well as the index of adhesion of microorganisms to “Nolatek” material. Results. Specimens from “Nolatek” material polymerized by hybrid technology during bending tests showed a value equal to 67.289±3.327 MPa. The adhesion index of strains — P. intermedia and C. albicnas is statistically significantly lower for samples polymerized using hybrid technology than when using light polymerization. Conclusion. Hybrid polymerization of the base material Nolatek is able to improve the physical, mechanical and microbiological properties of removable denture constructions.

Phytochemical Profiles, Antioxidant and Antibacterial Activities of Grape (Vitis vinifera L.) Seeds and Skin from Organic and Conventional Vineyards.

The therapeutic benefits of extracts obtained from different red grape fractions were thoroughly studied, however, data regarding the comparison of phytochemical extracts prepared from the same varieties coming from organic versus conventional management systems are rather lacking. The present study aimed at comparing some of the phytochemical characteristics and antimicrobial activity of hydroalcoholic (50% v/v) extracts obtained from four varieties of red grapes cultivated respectively in organic and conventional vineyards. Total flavonoid content, total phenolic compounds, and antioxidant activity were determined by molecular absorption spectroscopy. Antimicrobial activity of the studied extracts was evaluated against common bacterial strains isolated from different habitats according to specific lab procedures. The analyses were performed in solid broths by applying the disk diffusion method, which allowed for the simultaneous determination of the spectrum of the sensitivity of the tested bacteria as well as the values of the minimum inhibition concentration (MIC). It was found that favorable antagonistic activities against the tested bacteria strains were exhibited by the hydroalcoholic extracts from the seeds of the organic varieties, respectively the skin of the conventional varieties.

Design and Preparation of Silver–Copper Nanoalloys for Antibacterial Applications

The search for new more effective nanoparticles based antimicrobial agents has been under way in recent decades. Silver nanoparticles are hydrophobic and have a negative charge. We report on the preparation of Ag–Cu bimetallic nanoparticles with various silver contents synthesized by electric explosion of two twisted wires of the metals in argon atmosphere. The method allows to obtain nanoparticles of a given composition, has high performance and scalability. Nanoparticles were investigated using X-ray diffraction, high-resolution transmission electron microscopy, energy dispersive analysis and microelectrophoresis techniques. We evaluated the antibacterial activity of the nanoparticles against Gram-negative E. coli and Gram-positive methicillin resistance S. aureus MRSA. Our study showed that the synthesized nanoparticles have a positive zeta potential of about 30 mV at pH 7.2 and high antimicrobial activity against the tested bacteria strains, which is close to the activity of silver nanoparticles with a size of 20 nm. The high antimicrobial activity of the nanoparticles is due to the prolonged slow release of silver and copper ions, which makes nanoalloys more effective than Cu and Ag metallic nanoparticles. The synthesized nanoparticles have high antimicrobial activity and demonstrate the potential for their use as promising new generation antibacterial agents effective against resistant microorganisms.