Bacteriostatic Activity Research Articles

Study on the bacteriostasis of lemon essential oil and the application of lemon essential oil nanoemulsion on fresh-cut kiwifruit

Fresh-cut fruit has been popularized for use by consumers in recent years, but its shelf life is very short. Plant essential oils have received attention for their bioactive properties, such as antibacterial and antioxidant properties, but their volatile nature limited their application in foods. In this study, the bacteriostasis of lemon essential oil (LEO) was verified, and LEO nanoemulsion was prepared to preserve fresh-cut kiwifruit. Compared with those of gram-negative bacteria, the inhibition zone diameters of LEO against gram-positive bacteria were significantly greater, measuring 12.20 ± 0.67 mm (Staphylococcus aureus) and 14.23 ± 0.61 mm (Listeria monocytogenes), compared to 9.50 ± 1.08 mm (Escherichia coli). At a concentration of 50 mg/mL, LEO exhibited DPPH and ABTS radical scavenging rates of 84.88 and 83.01%, respectively, which were comparable to those of 10 mg/L vitamin C (VC). Konjac glucomannan, whey protein and LEO were used to prepare nanoemulsion. When 2.0% LEO was added, the nanoemulsion exhibited great stability, which resulted in a decrease in particle size to 220.80 nm, a decrease in PDI to 0.238, and an increase in zeta potential to-27.83 mV. The stability of the nanoemulsion with added LEO was superior to that of the nanoemulsion without LEO on the 15th day. Preservation tests on fresh-cut kiwifruit demonstrated that, on the 8th day, compared with no treatment, nanoemulsion containing 2.0% LEO reduced the weight loss rate from 3.20 to 1.16%, increased the firmness from 20.459 to 38.23, and decreased the decay rate from 80.69 to 41.74% compared to untreated kiwifruit. It also effectively maintained the original color of fresh-cut kiwifruit and had positive effects on the soluble solid content, titratable acid content, VC content, and total colony count. LEO has great bacteriostatic and antioxidant activity, and the use of LEO nanoemulsions on fresh-cut kiwifruit can effectively maintain various indicators of fresh kiwifruit after a 8-day storage period.

The Effect of Nanoscale Modification of Nisin by Different Milk-Derived Proteins on Its Physicochemical Properties and Antibacterial Activity.

Nisin is used as a natural food preservative because of its broad-spectrum antimicrobial activity against Gram-positive bacteria. However, free nisin is susceptible to various factors that reduce its antimicrobial activity. Milk protein, a protein derived from milk, has self-assembly properties and is a good carrier of bioactive substances. In this study, lactoferrin-nisin nanoparticles (L-N), bovine serum albumin-nisin nanoparticles (B-N), and casein-nisin nanoparticles (C-N) were successfully prepared by a self-assembly technique, and then their properties were investigated. The studies revealed that lactoferrin (LF) and nisin formed L-N mainly through hydrophobic interactions and hydrogen bonding, and L-N had the best performance. The small particle size (29.83 ± 2.42 nm), dense reticular structure, and good thermal stability, storage stability, and emulsification of L-N laid a certain foundation for its application in food. Further bacteriostatic studies showed that L-N enhanced the bacteriostatic activity of nisin, with prominent inhibitory properties against Listeria monocytogenes, Staphylococcus aureus, and Bacillus cereus, which mainly disrupted the cell membrane of the bacteria. The above results broaden our understanding of milk protein-nisin nanoparticles, while the excellent antibacterial activity of L-N makes it promising for application as a novel food preservative, which will help to improve the bioavailability of nisin in food systems.

Antibacterial and Antibiofilm Potential of Bacterial Cellulose Hydrogel Containing Vancomycin against Multidrug-Resistant Staphylococcus aureus and Staphylococcus epidermidis.

The present study aimed to evaluate the in vitro antibacterial and antibiofilm activity of bacterial cellulose hydrogel produced by Zoogloea sp. (HYDROGEL) containing vancomycin (VAN) against bacterial strains that cause wound infections, such as multidrug-resistant (MDR) Staphylococcus aureus and Staphylococcus epidermidis. Initially, HYDROGEL was obtained from sugar cane molasses, and scanning electron microscopy (SEM) was performed to determine morphological characteristics. Then, VAN was incorporated into HYDROGEL (VAN-HYDROGEL). The antibacterial activity of VAN, HYDROGEL, and VAN-HYDROGEL was assessed using the broth microdilution method to determine the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) against methicillin-sensitive S. aureus (MSSA) ATCC 25923, methicillin-resistant S. aureus (MRSA) ATCC 33591, S. epidermidis INCQS 00016 (ATCC 12228), five clinical isolates of MRSA, and nine clinical isolates of methicillin-resistant S. epidermidis, following the Clinical and Laboratory Standards Institute (CLSI) guidelines. Additionally, the antibacterial activity of VAN, HYDROGEL, and VAN-HYDROGEL was studied using the time-kill assay. Subsequently, the antibiofilm activity of VAN, HYDROGEL, and VAN-HYDROGEL was evaluated using crystal violet and Congo red methods, as well as SEM analysis. VAN and VAN-HYDROGEL showed bacteriostatic and bactericidal activity against MRSA and methicillin-resistant S. epidermidis strains. HYDROGEL did not show any antibacterial activity. Analysis of the time-kill assay indicated that HYDROGEL maintained the antibacterial efficacy of VAN, highlighting its efficiency as a promising carrier. Regarding antibiofilm activity, VAN and HYDROGEL inhibited biofilm formation but did not demonstrate biofilm eradication activity against methicillin-resistant S. aureus and S. epidermidis strains. However, it was observed that the biofilm eradication potential of VAN was enhanced after incorporation into HYDROGEL, a result also proven through images obtained by SEM. From the methods carried out in this study, it was possible to observe that HYDROGEL preserved the antibacterial activity of vancomycin, aside from exhibiting antibiofilm activity and enhancing the antibiofilm effect of VAN. In conclusion, this study demonstrated the potential of HYDROGEL as a candidate and/or vehicle for antibiotics against MDR bacteria that cause wound infections.

Testing of Anti-EMT, Anti-Inflammatory and Antibacterial Activities of 2',4'-Dimethoxychalcone.

Chalcone (1,3-diaryl-2-propen-1-one) is an α, β-unsaturated ketone that serves as an active constituent or precursor of numerous natural substances, exhibiting a broad spectrum of pharmacological effects. In this study, the classical Claisen-Schmidt condensation method was used to synthesize the chalcone derivative 2',4'-dimethoxychalcone (DTC) and evaluate its pharmacological activity. By upregulating the expression of the epithelial cell marker E-cadherin and downregulating the expression of the mesenchymal cell marker vimentin, DTC was found to inhibit transforming growth factor-β1 (TGF-β1)-induced epithelial-mesenchymal transition (EMT) process in A549 cells, maintaining the cells' epithelial-like morphology and reducing the ability of the cells to migrate. Additionally, DTC demonstrated the ability to decrease the expression levels of nitric oxide (NO), tumor necrosis factor (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β) in RAW264.7 cells, suggesting a possible anti-inflammatory effect. Furthermore, DTC was found to exhibit bacteriostatic activity against Staphylococcus aureus (S. aureus), Proteus vulgaris (P. vulgaris), methicillin-resistant Staphylococcus aureus (MRSA), and Candida albicans (C. albicans), indicating that this chemical may possess broad-spectrum antibacterial activity.

Combined effect of SAR-endolysin LysKpV475 with polymyxin B and Salmonella bacteriophage phSE-5.

Endolysins are bacteriophage (or phage)-encoded enzymes that catalyse the peptidoglycan breakdown in the bacterial cell wall. The exogenous action of recombinant phage endolysins against Gram-positive organisms has been extensively studied. However, the outer membrane acts as a physical barrier when considering the use of recombinant endolysins to combat Gram-negative bacteria. This study aimed to evaluate the antimicrobial activity of the SAR-endolysin LysKpV475 against Gram-negative bacteria as single or combined therapies, using an outer membrane permeabilizer (polymyxin B) and a phage, free or immobilized in a pullulan matrix. In the first step, the endolysin LysKpV475 in solution, alone and combined with polymyxin B, was tested in vitro and in vivo against ten Gram-negative bacteria, including highly virulent strains and multidrug-resistant isolates. In the second step, the lyophilized LysKpV475 endolysin was combined with the phage phSE-5 and investigated, free or immobilized in a pullulan matrix, against Salmonella enterica subsp. enterica serovar Typhimurium ATCC 13311. The bacteriostatic action of purified LysKpV475 varied between 8.125 μg ml-1 against Pseudomonas aeruginosa ATCC 27853, 16.25 μg ml-1 against S. enterica Typhimurium ATCC 13311, and 32.50 μg ml-1 against Klebsiella pneumoniae ATCC BAA-2146 and Enterobacter cloacae P2224. LysKpV475 showed bactericidal activity only for P. aeruginosa ATCC 27853 (32.50 μg ml-1) and P. aeruginosa P2307 (65.00 μg ml-1) at the tested concentrations. The effect of the LysKpV475 combined with polymyxin B increased against K. pneumoniae ATCC BAA-2146 [fractional inhibitory concentration index (FICI) 0.34; a value lower than 1.0 indicates an additive/combined effect] and S. enterica Typhimurium ATCC 13311 (FICI 0.93). A synergistic effect against S. enterica Typhimurium was also observed when the lyophilized LysKpV475 at ⅔ MIC was combined with the phage phSE-5 (m.o.i. of 100). The lyophilized LysKpV475 immobilized in a pullulan matrix maintained a significant Salmonella reduction of 2 logs after 6 h of treatment. These results demonstrate the potential of SAR-endolysins, alone or in combination with other treatments, in the free form or immobilized in solid matrices, which paves the way for their application in different areas, such as in biocontrol at the food processing stage, biosanitation of food contact surfaces and biopreservation of processed food in active food packing.

Magnetic separation, sunlight-driven photocatalytic activity, and antibacterial studies of Sm-doped Co0.33Mg0.33Ni0.33Fe2O4 nanoparticles.

Magnetic nanoparticles have emerged as a promising tool for wastewater treatment due to their unique properties. In this regard, Co0.33Mg0.33Ni0.33SmxFe2-xO4 (0.00 x 0.08) nanoparticles were prepared to examine their magnetic separation efficiency (MSE), photocatalytic, antibacterial, and antibiofilm performances. Pure nanoparticles, having the highest saturation magnetization (Ms = 31.87emu/g), exhibit the highest MSE, where 95.6% of nanoparticles were separated after 20min of applying a magnetic field of 150 mT. The catalytic performance of the prepared samples is examined by the photodegradation of rhodamine B (RhB) dye exposed to direct sunlight radiation. Improved photocatalytic activity is exhibited by Co0.33Mg0.33Ni0.33Sm0.04Fe1.96O4 nanoparticles, labeled as Sm0.04, where the rate of the degradation reaction is enhanced by 4.1 times compared to pure nanoparticles. Rising the pH and reaction temperature improves the rate of the photodegradation reaction of RhB. The incorporation of 15 wt% reduced graphene oxide (rGO) with Sm0.04 enhanced the rate of the reaction by 1.7 and 2.4 times compared with pure Sm0.04 sample and rGO, respectively. The antibacterial and antibiofilm activities against Escherichia coli, Leclercia adecarboxylata, Staphylococcus aureus, and Enterococcus faecium are assessed by the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) broth microdilution, the agar well diffusion, the time-kill assays, the biofilm formation, and destruction assays. The bacteria used in these assessments are isolated from wastewater. The nanoparticles exhibit a bacteriostatic activity, with a better effect against the Gram-positive isolates. Co0.33Mg0.33Ni0.33SmxFe2O4 (x = 0.00) nanoparticles have the best effect. The effect is exerted after 2-3h of incubation. Gram-positive biofilms are more sensitive to nanoparticles.

Exogenous Glucose Interferes with Antimicrobial-Mediated ROS Accumulation and Bacterial Death.

Glucose is widely used in the reconstitution of intravenous medications, which often include antimicrobials. How glucose affects antimicrobial activity has not been comprehensively studied. The present work reports that glucose added to bacteria growing in a rich medium suppresses the bactericidal but not the bacteriostatic activity of several antimicrobial classes, thereby revealing a phenomenon called glucose-mediated antimicrobial tolerance. Glucose, at concentrations corresponding to blood-sugar levels of humans, increased survival of Escherichia coli treated with quinolones, aminoglycosides, and cephalosporins with little effect on minimal inhibitory concentration. Glucose suppressed a ROS surge stimulated by ciprofloxacin. Genes involved in phosphorylated fructose metabolism contributed to glucose-mediated tolerance, since a pfkA deficiency, which blocks the formation of fructose-1,6-bisphosphate, eliminated protection by glucose. Disrupting the pentose phosphate pathway or the TCA cycle failed to alter glucose-mediated tolerance, consistent with an upstream involvement of phosphorylated fructose. Exogenous sodium pyruvate or sodium citrate reversed glucose-mediated antimicrobial tolerance. Both metabolites bypass the effects of fructose-1,6-bisphosphate, a compound known to scavenge hydroxyl radical and chelate iron, activities that suppress ROS accumulation. Treatment with these two compounds constitutes a novel way to mitigate the glucose-mediated antimicrobial tolerance that may exist during intravenous antimicrobial therapy, especially for diabetes patients.

Cytotoxicity and Biological Activities of Geopopolis Extract from the Stingless bee (Melipona scutellaris) in Isolates of Staphylococcus aureus.

Geopropolis resins are produced by stingless bees (Meliponinae), developed from the collection of resinous materials, waxes and exudates, from the flora of the region where stingless bees are present, in addition to the addition of clay or earth in its composition. Several biological activities are attributed to Ethanol Extracts of Geopropolis (EEGP). The bioactive properties are associated with the complex chemical composition that the samples have. This work aims to evaluate the biological activities of the EEGP, in order to contribute with a natural therapeutic alternative, to face infections, mainly those caused by resistant strains of Staphylococcus aureus. The EEGP MIC tests showed antibacterial activity against two strains of S. aureus, both at concentrations of 550 μg/mL. The MBC performed with the inhibition values showed that the EEGP has bacteriostatic activity in both strains. Biofilm inhibition rates exhibited an average value greater than 65 % at the highest concentration. The EEGP antioxidant potential test showed good antioxidant activity (IC50) of 11.05±1.55 μg/mL. In the cytotoxicity test against HaCat cells, after 24 hours, EEGP induced cell viability at the three tested concentrations (550 μg/mL: 81.68±3.79 %; 1100 μg/mL: 67.10±3.76 %; 2200 μg/mL: 67.40±1.86 %). In view of the above, the safe use of EEGP from the brazilian northeast could be proven by the cytotoxicity test, and its use as an antioxidant and antibacterial agent has proven to be effective, as an alternative in combating oxidative stress and microorganisms such as S. aureus, which, through the spread and ongoing evolution of drug resistance, generates an active search for effective solutions.

Identifying and characterization of novel broad-spectrum bacteriocins from the Shanxi aged vinegar microbiome: Machine learning, molecular simulation, and activity validation

Shanxi aged vinegar microbiome encodes a wide variety of bacteriocins. The aim of this study was to mine, screen and characterize novel broad-spectrum bacteriocins from the large-scale microbiome data of Shanxi aged vinegar through machine learning, molecular simulation and activity validation. A total of 158 potential bacteriocins were innovatively mined from 117,552 representative genes based on metatranscriptomic information from the Shanxi aged vinegar microbiome using machine learning techniques and 12 microorganisms were identified to secrete bacteriocins at the genus level. Subsequently, employing AlphaFold2 structure prediction and molecular dynamics simulations, eight bacteriocins with high stability were further screened, and all of them were confirmed to have bacteriostatic activity by the Escherichia coli BL21 expression system. Then, gene_386319 (named LAB-3) and gene_403047 (named LAB-4) with the strongest antibacterial activities were purified by two-step methods and analyzed by mass spectrometry. The two bacteriocins have broad-spectrum antimicrobial activity with minimum inhibitory concentration values of 6.79 μg/mL-15.31 μg/mL against Staphylococcus aureus and Escherichia coli. Furthermore, molecular docking analysis indicated that LAB-3 and LAB-4 could interact with dihydrofolate reductase through hydrogen bonds, salt-bridge forces and hydrophobic forces. These findings suggested that the two bacteriocins could be considered as promising broad-spectrum antimicrobial agents.

Cationic amphiphilic meroterpenoids: synthesis, antibacterial, antifungal and mutagenic activity

In this research, using the thia-Michael reaction, cationic amphiphilic meroterpenoids containing fragments of mono- and sesquiterpenoids were synthesized. The bacteriostatic and fungistatic activity of synthesized meroterpenoids against the fungi Saccharomyces cerevisiae and Candida sp., Gram-positive (Staphylococcus aureus, Staphylococcus epidermidis) and Gram-negative (Salmonella typhimurium, Klebsiella pneumoniae, Pseudomonas aeruginosa) bacteria was studied. The compound containing the farnesyl fragment was most active against Saccharomyces cerevisiae (MIC 0.039 mg/mL), Candida sp. (MIC 0.078 mg/mL), Gram-positive bacteria Staphylococcus epidermidis (MIC 0.02 mg/mL) and Gram-negative Salmonella typhimurium (MIC 0.078 mg/mL). Besides, the Ames test demonstrated the absence of direct mutagenic action in all the studied compounds.

Inhibition and Mechanism of Citral on Bacillus cereus Vegetative Cells, Spores, and Biofilms.

Bacillus cereus causes food poisoning by producing toxins that cause diarrhea and vomiting and, in severe cases, endocarditis, meningitis, and other diseases. It also tends to form biofilms and spores that lead to contamination of the food production environment. Citral is a potent natural antibacterial agent, but its antibacterial activity against B. cereus has not been extensively studied. In this study, we first determined the minimum inhibitory concentrations and minimum bactericidal concentrations, growth curves, killing effect in different media, membrane potential, intracellular adenosine triphosphate (ATP), reactive oxygen species levels, and morphology of vegetative cells, followed by germination rate, morphology, germination state of spores, and finally biofilm clearance effect. The results showed that the minimum inhibitory concentrations and minimum bactericidal concentrations of citral against bacteria ranged from 100 to 800 μg/mL. The lag phase of bacteria was effectively prolonged by citral, and the growth rate of bacteria was slowed down. Bacteria in Luria-Bertani broth were reduced to below the detection limit by citral at 800 μg/mL within 0.5 h. Bacteria in rice were reduced to 3 log CFU/g by citral at 4000 μg/mL within 0.5 h. After treatment with citral, intracellular ATP concentration was reduced, membrane potential was altered, intracellular reactive oxygen species concentration was increased, and normal cell morphology was altered. After treatment with citral at 400 μg/mL, spore germination rate was reduced to 16.71%, spore morphology was affected, and spore germination state was altered. It also had a good effect on biofilm removal. The present study showed that citral had good bacteriostatic activity against B. cereus vegetative cells and its spores and also had a good clearance effect on its biofilm. Citral has the potential to be used as a bacteriostatic substance for the control of B. cereus in food industry production.

Isolation, identification and quantification of flavonoids from the flowers of <i>Staphylea pinnata</i> L.

Introduction. Search for new plant species containing biologically active substances (hereinafter – BAS) is one of the leading tasks of pharmacognosy as a science. The search for flavonoid glycosides in plant raw materials is especially relevant, since they have anti-inflammatory, antioxidant, immunostimulating, as well as weak fungicidal and bacteriostatic action. Staphylea pinnata L. is an endemic plant of the Caucasus, cultivated not only in Georgia, but also in the Russian Federation in the Northern and Northwestern Caucasus. In foreign literature there are studies of antioxidant, antiproliferative and cytotoxic activity of leaf extracts of several species of S. pinnata L., as well as inhibitory activity of COX-1, COX-2 and LTB4 formation. Meanwhile, no serious Russian-language scientific studies on either the chemical composition or pharmacological action of generative organs of S. pinnata were found in the literature. This work is part of a comprehensive phytochemical study of S. pinnata. The aim of the work is to study the qualitative and quantitative composition of flavonoids in the studied object.Aim. To isolate, identify and quantify flavonoids in flowers and buds of Staphylea pinnata L.Materials and methods. Alcohol-water extracts from dried generative organs of the studied plant were used as analyzed solutions. Solutions were analyzed on a spectrophotometer SF-2000 (LLC "OKB Spectr", Russia) after sample preparation with aluminum chloride and on an HPLC Nexera-i LC-2040 (Shimadzu Corporation, Japan) equipped with a column and sample thermostat, degasser and autosampler using an individually selected elution gradient of the mobile phase (0.1 % orthophosphoric acid/acetonitrile solution). The primary data were processed using LabSolutions Single LC software (Shimadzu Corporation, Japan). Compounds from the flavonoid group were identified by retention times. Detection was carried out using a UV detector with an absorption wavelength of 365 ± 2 nm.Result and discussion. Alcohol-water extracts from flowers and buds of S. pinnata L. were obtained. Quantitative evaluation by spectrophotometry for flavonoid content was carried out. A gradient elution mode for HPLC was selected for simultaneous determination of 7 flavonoid glycosides. These chromatographic conditions allowed the identification and quantification of astragaline, cynaroside, cosmosiin, narcissin and rutin in flowers and buds of Staphylea pinnata L. Flavonoid glycosides: raponticin and kaempferol were not detected.Conclusion. Flavonoid glycosides were isolated from the generative organs of S. pinnata L., a technique for quantitative determination of flavonoid glycosides in alcohol-water extracts was developed, astragalin, cynaroside, cosmosiin, narcissin and rutin were detected and quantified.

Design, synthesis, and bioactivity evaluation of clindamycin derivatives against multidrug-resistant bacterial strains.

Our research aims to reduce the bacterial resistance of clindamycin against Gram-positive bacteria and expand its range of bacterial susceptibility. First, we optimized the structure of clindamycin based on its structure-activity relationship. Second, we employed the fractional inhibitory concentration method to detect drugs suitable for combination with clindamycin derivatives. We then used a linker to connect the clindamycin derivatives with the identified combined therapy drugs. Finally, we tested antibacterial susceptibility testing and conducted in vitro bacterial inhibition activity assays to determine the compounds. with the highest efficacy. The results of our study show that we synthesized clindamycin propionate derivatives and clindamycin homo/heterodimer derivatives, which exhibited superior antibacterial activity compared to clindamycin and other antibiotics against both bacteria and fungi. In vitro bacteriostatic activity testing against four types of Gram-negative bacteria and one type of fungi revealed that all synthesized compounds had bacteriostatic effects at least 1000 times better than clindamycin and sulfonamides. The minimum inhibitory concentration (MIC) values for these compounds ranged from 0.25 to 0.0325 mM. Significantly, compound 5a demonstrated the most potent inhibitory activity against three distinct bacterial strains, displaying MIC values spanning from 0.0625 to 0.0325 mM. Furthermore, our calculations indicate that compound 5a is safe for cellular use. In conclusion, the synthesized compounds hold great promise in addressing bacterial antibiotic resistance.

Synthesis and Antimicrobial Evaluation of Some Schiff Base Derivatives

Schiff bases are the nitrogen analogs of ketones or aldehydes, with the carbonyl functional group replaced by an imine or azomethine group. They are formed by the condensation reaction of a primary amine and a carbonyl group, and they are widely employed in industry and have a variety of biological activities. Four Schiff base derivatives were successfully synthesized from benzaldehyde (PC1), anisaldehyde (PC2), 4-nitrobenzaldehyde (PC 2), and cinnamaldehyde (PC4) and tested for their antibacterial capabilities were evaluated against bacteria and fungi. The Schiff base had a high percentage yield of 98.28% (PC1), 95.7% (PC2), 91.6% (PC3), and 98% (PC4), with melting points ranging from 178 -187°C, 183-191°C, 160-164°C, and 195-205°C respectively. All Schiff bases showed activity against Escherichia coli with a Minimum Inhibitory Concentration (MIC) of 62.5ug/ml (PC1, PC4) and 250ug/ml (PC2, PC3). The Minimum Bactericidal Concentrations (MBC) were 125ug/ml, 500ug/ml, and 250ug/ml for PC1, PC2 and PC4 respectively. PC3 showed no bactericidal activity against Escherichia coli. Schiff bases PC1, PC2, and PC3 showed activity against Staphylococcus aureus with MIC of 62.5ug/ml. The MBC obtained was 125ug/ml for PC1 and PC2, while 125ug/ml, and 250ug/ml for PC3. PC4 showed no bacteriostatic and bactericidal activity against Staphylococcus aureus. Schiff bases showed fungistatic activity against Candida albican with MIC of 250ug/ml, 62.5ug/ml, and 125ug/ml for PC1, PC2/PC3, and PC4 respectively. However, none showed fungicidal activity.

Antibacterial activity of closantel against methicillin-resistant Staphylococcus aureus and itsbiofilm.

The antimicrobial resistance of Staphylococcus aureus (S. aureus) has become a challenge in the treatment of infectious diseases. It is of great clinical value to discovery effective antimicrobial agents against multi-drug resistant S. aureus and its biofilms. This study aims to explore the antibacterial activity of the antiparasitic drug closantel against methicillin-resistant S. aureus and its biofilms through drug repurposing. The sensitivity of S. aureus to closantel was assessed using microbroth dilution and disk diffusion methods. The bacteriostatic and bactericidal activities of closantel were determined by time-kill curves and colony count. Scanning electron microscopy combined with SYTOX Green and DiSC3(5) fluorescence probes were used to study the bactericidal mechanism of closantel. The influence of resistance was assessed by continuous exposure to sub-inhibitory concentrations of closantel. The anti-biofilm activity was evaluated using 96-well plates and crystal violet staining, and cytotoxicity was measured using the CCK-8 assay. The minimal inhibitory concentration (MIC) of closantel for both methicillin-sensitive and methicillin-resistant S. aureus ranged from 0.125 to 1.000 μg/mL. Disk diffusion tests showed that 80 μg of closantel created an inhibition zone, which increased in diameter with higher drug amounts. Sub-inhibitory concentrations (0.031 μg/mL) of closantel significantly inhibited S. aureus proliferation, reducing bacterial turbidity from 0.26±0.00 to 0.11±0.01 (t=16.06, P<0.001), with stronger inhibition at higher concentrations. Closantel at 0.25×MIC inhibited S. aureus proliferation for 12 hours, while 1×MIC inhibited it for over 24 hours, with the number of viable bacteria decreasing as the drug concentration increased. Mechanistic studies indicated that closantel effectively disrupted the integrity of S. aureus cell membranes, significantly increasing SYTOX Green and DiSC3(5) fluorescence intensity. Even after 25 days of continuous exposure to sub-inhibitory concentrations of closantel, no resistance developed. Closantel at 0.0625 μg/mL significantly inhibited biofilm formation, reducing it from 1.29±0.16 to 0.62±0.04 (t=11.62, P<0.001), showing a clear dose-dependent effect. Closantel at 2 μg/mL also significantly eradicated established biofilms, reducing biofilm mass from 1.62±0.34 to 0.51±0.39 (t=4.84, P<0.01). Additionally, closantel exhibited extremely low cytotoxicity, with half-maximal lethal concentrations for HepG2 liver cancer cells and normal LO2 liver cells both exceeding 64 μg/mL. Closantel exhibits strong antibacterial activity against S. aureus and its biofilm with low cytotoxicity against human cells, making it a promising candidate for new therapeutic strategies against S. aureus-related infections.

Oxidative Stress Response Mechanisms Sustain the Antibacterial and Antioxidant Activity of Quercus ilex.

The development of new natural antibiotics is considered as the heart of several investigations in the nutraceutical field. In this work, leaves of Quercus ilex L. treated by tropospheric ozone (O3) and nitrogen (N) deposition, exhibited a clear antimicrobial efficacy against five multi-drug resistant (MDR) bacterial strains (two gram-positive and three gram-negative). Under controlled conditions, it was studied how simulated N deposition influences the response to O3 and the antibacterial and antioxidant activity, and antioxidant performance. The extraction was performed by ultra-pure acetone using two different steps. A higher antioxidant activity was measured in the presence of interaction between O3 and N treatments on Quercus leaves. At the same time, all organic extracts tested have shown bacteriostatic activity against all the tested strains with a MIC comprised between 9 and 4 micrograms/mL, and a higher antioxidant efficacy shown by spectrophotometric assay. Stronger antimicrobial activity was found in the samples treated with O3, whereas N-treated plants exhibited an intermediate antibacterial performance. This performance is related to the stimulation of the non-enzymatic antioxidant system induced by the oxidative stress, which results in an increase in the production of antimicrobial bioactive compounds.

Ligand-Free Silver Nanoparticles: An Innovative Strategy against Viruses and Bacteria.

The spread of antibiotic-resistant bacteria and the rise of emerging and re-emerging viruses in recent years constitute significant public health problems. Therefore, it is necessary to develop new antimicrobial strategies to overcome these challenges. Herein, we describe an innovative method to synthesize ligand-free silver nanoparticles by Pulsed Laser Ablation in Liquid (PLAL-AgNPs). Thus produced, nanoparticles were characterized by total X-ray fluorescence, zeta potential analysis, transmission electron microscopy (TEM), and nanoparticle tracking analysis (NTA). A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was performed to evaluate the nanoparticles' cytotoxicity. Their potential was evaluated against the enveloped herpes simplex virus type 1 (HSV-1) and the naked poliovirus type 1 (PV-1) by plaque reduction assays and confirmed by real-time PCR and fluorescence microscopy, showing that nanoparticles interfered with the early stage of infection. Their action was also examined against different bacteria. We observed that the PLAL-AgNPs exerted a strong effect against both methicillin-resistant Staphylococcus aureus (S. aureus MRSA) and Escherichia coli (E. coli) producing extended-spectrum β-lactamase (ESBL). In detail, the PLAL-AgNPs exhibited a bacteriostatic action against S. aureus and a bactericidal activity against E. coli. Finally, we proved that the PLAL-AgNPs were able to inhibit/degrade the biofilm of S. aureus and E. coli.

Screening Studies of the Antimicrobial Activity of the Pyrimidine Compound 2,2-[6-Bromo-2,4-Dioxoquinazoline-1,3(2H)diyl]bis(N-Carbamimidoylacetamide)

The aim of this study was to screen the antimicrobial activity of a pyrimidine compound under the laboratory code VMA-21-01. Antimicrobial activity was studied in relation to: Staphylococcus aureus, Streptococcus pneumoniae, Escherichia coli, Klebsiella pneumonia, and Proteus mirabilis. The antimicrobial activity of 2,2-[6-Bromo-2,4-dioxoquinazoline- 1,3(2H)diyl]bis(N-carbamimidoylacetamide) was carried out in vitro by serial dilution and determination of its minimum inhibitory concentration. The sensitivity of microorganisms to the test substance was determined in a meat-peptone broth (visual assessment), followed by reinoculation on meat-peptone agar and colony count. DMSO tubes were used as a control. A 4% gentamicin solution was used as a comparison drug. In an in vitro experiment, it was found that the pyrimidine compound 2,2-[6-Bromo-2,4-dioxyquinazoline-1,3(2H)diyl]bis(N-carbamimidoylacetamide) under the laboratory cipher VMA21-01 has bactericidal activity against K. pneumonia comparable to the comparison drug gentamicin, as well as bacteriostatic activity against S. aureus, S. pneumoniae, E. coli, and P. mirabilis.

Evaluation of bacteriostatic and antioxidant activities of various extracts from aerial part of Piper nigrum grown in Gulf countries traditionally used for the treatment of various infectious diseases

AbstractPiper nigrum (P. nigrum) is a tropical medicinal plant widely available in Southeast Asian countries including Oman. In Asian It has a long history of usage in places such as Oman for treating of rheumatism, colds, and various infections. Based on the medicinal uses, the purpose of this research is to create diverse fractions using increasing solvent polarity from the aerial part of the collected plant species and evaluate their antibacterial and antioxidant activities by using established bioassays. The aerial part was collected from the Southern part of Oman and processed using the standard method. The processed materials were recovered using the maceration method using methanol, and the methanol raw extracts was further fractionated with water extraction, butanol, ethyl acetate (ETA), hexane, and dichloromethane are produced using different liquid polarities. Each of the six plant extracts was tested for antioxidant and antibacterial potential at different concentrations against DPPH (1, 1-diphenyl-2-picrylhydrazyl) and agar diffusion methods. All of the fractions at varied concentrations shown promising antioxidant activity with DPPH against the gallic acid. The maximum activity was observed in hexane extract, while the smallest potential was noticed in butanol extract, in the following order: hexane &gt; chloroform &gt; water &gt; methanol &gt; ethyl acetate &gt; butanol extract. The antibacterial efficacy of six different polarities extracts gives moderate activity against two Gram-positive bacteria strains namely S. saprophyticus and S. aureus and three Gram-negative namely P. vulgaris, K. senegalensis and E. coli. Among the six extracts, hexane extract had the most antibacterial activity, whereas butanol extract had the smallest activity. The remaining four extracts, chloroform, ethyl acetate, methanol, and water, all had comparable activity. In conclusion, the extracts with the greatest activity from the chosen plant types might be employed as natural antioxidants to treat infectious disorders.

Activity of Paullinia pinnata leaf fractions on bacterial isolates associated with treatment-failure wounds

The current surge of multidrug resistant infections has led to many cases of treatment failure in clinical practices. This has necessitated the search for new drugs from natural sources which could be used to curb this menace. Paullinia pinnata (Linn.) leaves are deployed traditionally for the treatment of various ailments such as malaria and the treatment of wounds. The essence of this study is to assess the antibacterial potential of P. pinnata leaf fractions on four antibiotic-resistant bacteria isolated from treatment failed wounds. The n-hexane and ethyl acetate fractions were obtained from the methanol extract of the leaves of P. pinnata by the one-solvent system fractionation. The antibacterial capacity of the fractions was determined by the agar well diffusion method and gentamicin (30 µg/mL) was the control. Clinical isolates of two Gram-positive (Staphylococcus aureus and Bacillus cereus) and two Gram-negative (Klebsiella pneumoniae and Proteus vulgaris) bacteria were used. The fractions showed no activity to moderate activity at lower concentrations. The ethyl acetate fraction showed bacteriostatic activity in a dose-dependent manner and was better than that of n-hexane, and could therefore be a good drug target for antimicrobial therapies, especially for wound treatment.