MBC Values Research Articles

Microbial Biosynthesis of Chrysazin Derivatives in Recombinant Escherichia coli and Their Biological Activities.

Anthraquinone and its derivatives show remarkable biological properties such as anticancer, antibacterial, antifungal, and antiviral activities. Hence, anthraquinones derivatives have been of prime interest in drug development. This study developed a recombinant Escherichia coli strain to modify chrysazin to chrysazin-8-O-α-l-rhamnoside (CR) and chrysazin-8-O-α-l-2′-O-methylrhamnoside (CRM) using rhamnosyl transferase and sugar-O-methyltransferase. Biosynthesized CR and CRM were structurally characterized using HPLC, high-resolution mass spectrometry, and various nuclear magnetic resonance analyses. Antimicrobial effects of chrysazin, CR, and CRM against 18 superbugs, including 14 Gram-positive and 4 Gram-negative pathogens, were investigated. CR and CRM exhibited antimicrobial activities against nine pathogens, including methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive Staphylococcus aureus (MSSA) in a disk diffusion assay at a concentration of 40 µg per disk. There were MIC and MBC values of 7.81–31.25 µg/mL for CR and CRM against methicillin-sensitive S. aureus CCARM 0205 (MSSA) for which the parent chrysazin is more than >1000 µg/mL. Furthermore, the anti-proliferative properties of chrysazin, CR, and CRM were assayed using AGS, Huh7, HL60, and HaCaT cell lines. CR and CRM showed higher antibacterial and anticancer properties than chrysazin.

Chemical and antibacterial properties of Baccharis dracunculifolia DC essential oils from different regions of Brazil

ABSTRACT This study aimed to evaluate the chemical and antibacterial properties of the essential oil of B. dracunculifolia from three regions of Brazil: Midwest, Southeast and South region. The major compounds of essential oil from Midwest region were (E)-nerolidol (28.15%) and spathulenol (17.68%), both oxygenated sesquiterpenes. And the major compounds of essential oils from Southeast and South regions were (E)-nerolidol (12.75–13.95%), bicyclogermacrene (10.76–14.21%) and limonene (10.49–19.36%). The three essential oils showed antibacterial activity for both Gram-positive and Gram-negative bacteria tested, with MIC values from 0.03 to 0.15 mg/mL and MBC values from 0.05 to 0.30 mg/mL. The B. dracunculifolia essential oil from the Midwest region of Brazil presented higher values of oxygenated sesquiterpenes and was more effective on all tested bacterial strains, with lower and statistically significant MBC values, compared to the oils from the Southeast and South regions of Brazil

GC-MS Analysis, Antibacterial and Antioxidant Potential of Ethyl Acetate Leaf Extract of Senna singueana (Delile) Grown in Kenya.

Bacterial diseases are a leading cause of mortality and morbidity globally. During bacterial diseases, an elevation of host immune response occurs, which involves the production of free radicals in response to the bacterial infection. The overproduction of free radicals in excess of the antioxidants leads to oxidative stress. Conventional antibiotics are linked to side effects such as hypersensitivity reactions in addition to bacterial pathogens developing resistance against them. Artificial antioxidants are said to be carcinogenic. This study sought to confirm folklore use and validate the antibacterial and antioxidant potential of Senna singueana which has been widely used in the Mbeere community. The in vitro antibacterial potentials of the plant extract were investigated on Bacillus subtilis ATCC 21332, Escherichia coli ATCC 25922, Salmonella typhi ATCC 1408, and Staphylococcus aureus ATCC 25923. Ciprofloxacin (100 µg/ml) drug was used as a standard reference, whereas 5% DMSO was used as a negative reference. The antibacterial tests included disc diffusion and minimum inhibitory and bactericidal concentrations. S. singueana ethyl acetate extract showed broad-spectrum potential against tested bacterial microbes producing mean zones of inhibition (MZI) from 07.67 ± 0.33 to 17.67 ± 0.33 mm. The extract demonstrated a greater effect on Gram-positive than Gram-negative bacterial pathogens. Antibacterial properties of ciprofloxacin were significantly greater in comparison to plant extract in all the dilutions (p < 0.05), while 5% DMSO was inactive against all the tested bacteria. MBC values were greater than MIC values. Antioxidant properties of the extract were determined through scavenging effects of DPPH and hydroxyl radicals (•OH) as well as ferric reducing antioxidant potential (FRAP) assay. S. singueana demonstrated effects against all radicals formed. Additionally, the extract exhibited ferric reducing abilities. The extract also contained various phytocompounds with known antibacterial and antioxidant properties. This study recommends the therapeutic use of S. singueana as an antibacterial as well as an antioxidant agent.

Isolation of secondary metabolite compounds of Coffee Benalu leaves (Loranthus parasiticus (L.) Merr.) and its antibacterial activity test

Coffee parasite leaves (Loranthus parasiticus (L.) Merr) is one of the plants that can be used as a medicinal material commonly obtained in various subtropical regions or tropical regions. This study aims to isolation of secondary metabolite compounds from methanol extract of coffee leaves and antibacterial activity by of disc diffusion and microdilution methods against S. aureus bacteria, S. mutans, and S. viridians. The result of antibacterial activity against S. aureus bacteria, S. mutans, and S. viridians respectively is 7.5 mm; 7.9 mm; and 8 mm which indicates that the ability to inhibit the growth of methanol extract bacteria 1% coffee leaves belongs to the medium category. The results of the microdilution method in determining the value of KHM against bacteria S. Aureus, S. Mutans, and S. Viridians are equal to the KHM value of 5000 μg/mL. Meanwhile, the MBC value for S. aureus was &gt;5000 g/Ml, for S. mutans was &gt;5000 g/mL and for S. viridians it was 5000 g/mL, indicating that the methanol extract of the coffee parasite leaves was only an inhibitor. Isolation of secondary metabolite compounds is carried out by fractionation using Liquid Vacuum Chromatography and Gravitational Column Chromatography which are further characterized using the GC-MS instrument. The results of the isolation of secondary metabolites from the methanol extract of the leaves of the coffee parasite (Loranthus parasiticus (L.) Merr.) showed that the leaves of the coffee parasite contained any 9 compounds.

Variation of Salvia officinalis L. Essential Oil and Hydrolate Composition and Their Antimicrobial Activity

This study aimed to investigate the chemical composition of steam distillate essential oil and corresponding hydrolate obtained from S. officinalis grown in Serbia, as well as the influence of weather conditions (temperature and precipitations) on their chemical profiles. Furthermore, their antimicrobial activity was investigated in vitro. The main compounds in essential oil were cis-thujone, followed by camphor, trans-thujone, and 1,8-cineole, while hydrolate was slightly different from the essential oil, with camphor, cis-thujone, and 1,8-cineole as the main compounds. Among the eight respiratory-associated microorganisms, Klebsiella oxytoca was the most sensitive to the tested EOs (minimum inhibitory concentration (MIC)/minimal bactericidal/fungicidal concentration (MBC/MFC) were 14.20 and 28.4 μL mL−1, respectively). MIC and MBC values of other tested bacteria ranged between 28.40 and 227.25 μL mL−1 while for Candida albicans MIC/MFC ranged from 28.40/56.81 to 56.81–113.63 μL mL−1. Antibiotic susceptibility patterns for the analyzed eight respiratory-associated microorganisms showed an intermediate level of resistance to commonly used antibiotics such as ampicillin, levofloxacin, and ciprofloxacin. As a preliminary approach to the antimicrobial profiling of the tested EO, the obtained results revealed that the tested samples possess remarkable antibacterial activities and could be used to develop pharmaceutical formulations as an alternative to conventional antibiotic therapy.

Chloramine Trihydrate-Mediated Tandem Synthesis of New Pyrrole and/or Arene-Linked Mono- and Bis(1,3,4-Oxadiazole) Hybrids as Potential Bacterial Biofilm and MRSA Inhibitors.

A two-step tandem protocol was used to prepare new pyrrole and/or arene-linked bis(1,3,4-oxadiazoles) as well as their mono-analogs. The appropriate aldehydes and benzohydrazides were first condensed in ethanol at 80 °C to yield the corresponding N-benzoylhydrazones. Without isolation, the previous intermediates were subjected to a chloramine trihydrate-mediated oxidative cyclization in DMSO at 180 °C to yield the target molecules. The antibacterial potency of the (pyrrole-arene)-linked hybrids exceeded the arene-linked hybrids, and the bis(1,3,4-oxadiazoles) exceeded their mono-analogs against six different ATCC strains. Furthermore, the antibacterial efficacy of bis(1,3,4-oxadiazoles) 11c, and 11f, which are linked to pyrrole, and (p-tolylthio)methyl units, was highest against S. aureus, E. coli, and P. aeruginosa strains. Their MIC ranged between 3.8 and 3.9 μM, while their MBC values ranged between 7.7 and 15.8 μM. Additionally, they showed promising bacterial biofilm inhibitory activity against the same strains tested, with IC50 values ranging from 4.7 to 5.3 μM. They were also effective against MRSA ATCC : 33591, and ATCC : 43300 strains, with MIC, and MBC values ranging from 3.8-7.9 and 7.7-15.8 μM, respectively. When tested against the MCF-10A cell lines, hybrids 11c, and 11f are cytotoxic at concEntrations that are more than 6 and 13-fold higher than their MIC values against the S. aureus, E. coli, and P. aeruginosa strains, respectively. This lends support to both hybrids' potential as safe antibacterial agents.

Prediction Mechanism of Nevadensin as Antibacterial Agent against S. sanguinis: In vitro and In silico Studies.

Streptococcus sanguinis can contribute to tooth demineralization, which can lead to dental caries. Antibiotics used indefinitely to treat dental caries can lead to bacterial resistance. Discovering new antibacterial agents from natural products, like Ocimum basilicum, will help combat antibiotic resistance. In silico analysis (molecular docking) can help determine the lead compound by studying the molecular interaction between the drug and the target receptor (MurA enzyme and DNA gyrase). It is a potential candidate for antibacterial drug development. The research objective is to isolate the secondary metabolite of O. basilicum extract that exhibits activity against S. sanguinis through in vitro and in silico analysis. n-Hexane extract of O. basilicum was purified by combining column chromatography with bioactivity-guided fractionation. The in vitro antibacterial activity against S. sanguinis was determined using the disc diffusion and microdilution method, while molecular docking simulation of nevadensin (1) with MurA enzyme and DNA gyrase was performed by using PyRx 0.8 program. Nevadensin from O. basilicum was successfully isolated and characterized by spectroscopic methods. This compound showed antibacterial activity against S. sanguinis with MIC and MBC values of 3750 and 15000 μg/mL, respectively. In silico analysis showed that the binding affinity to MurA was -8.5 Kcal/mol, and the binding affinity to DNA gyrase was -6.7 Kcal/mol. The binding of nevadensin-MurA is greater than fosfomycin-MurA. Otherwise, Nevadensin-DNA gyrase has a weaker binding affinity than fluoroquinolone-DNA gyrase and chlorhexidine-DNA gyrase. Nevadensin showed potential as a new natural antibacterial agent by inhibiting the MurA enzyme rather than DNA gyrase.

Antibacterial Activity of Jojoba Seed residue and Its Possible Active Compound

Jojoba (Simmondsia chinensis) (Link) C.K. is a shrub plant widely used in cosmetics, especially jojoba oil. The residue will remain when producing jojoba oil and become waste. This study aimed to determine the antibacterial activity of Jojoba seed residue (JSR) and its possible active antibacterial compounds. JSR was collected from Sudan and extracted by maceration with n-hexane, ethyl acetate, and 70% ethanol. The antibacterial activity was determined with the microdilution method against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The 70% ethanol extract showed the value of MIC and MBC against E. coli, which was 7.8 mg/ml; meanwhile, against S. aureus was 3.9 mg/mL and 7.8 mg/mL, respectively. Fractionation of 70% ethanol extract using silica gel column chromatography with gradient elution produced ten fractions. Fraction 3 showed the MIC and MBC values in E. coli which were 3.1 mg/mL and 12 mg/ml, and in S. aureus, which were 3.1 mg/mL and 6.2 mg/mL. The fractionation continued to Fraction 3 using preparative thin layer chromatography to collect subfraction 3.2 at an Rf value of 0.76, actively based on contact autobiography against E. coli and S. aureus. Embelin was detected in Subfraction 3.2 using liquid chromatography-mass spectrometry (UHPLC-Q-Orbitrap HRMS) and suggested as the active antibacterial component in JSR.

Hydroquinine Possesses Antibacterial Activity, and at Half the MIC, Induces the Overexpression of RND-Type Efflux Pumps Using Multiplex Digital PCR in Pseudomonas aeruginosa.

Hydroquinine is an organic compound that is closely related to quinine-derivative drugs and contains anti-malarial and anti-arrhythmia activities. It has been also found in abundance in some natural extracts that possess antibacterial properties. However, there is little evidence demonstrating the antibacterial effect of hydroquinine. Therefore, we aimed to investigate the antibacterial properties of hydroquinine using broth microdilution methods. In addition, we evaluated the transcriptional responses of P. aeruginosa to hydroquinine-induced stress using RNA sequencing with transcriptomic analysis and validated the results using PCR-based methods. The MIC and MBC values of hydroquinine against all eight bacterial strains investigated ranged from 650 to 2500 and from 1250 to 5000 µg/mL, respectively. Transcriptomic analysis demonstrated that RND efflux pump transcripts were overexpressed (4.90–9.47 Log2 fold change). Using mRT-dPCR and RT-qPCR, we identified that mRNA levels of mexD and mexY genes were overexpressed in response to just half the MIC of hydroquinine in P. aeruginosa. In conclusion, we uncover the antimicrobial potential of hydroquinine as well as identify changes in gene expression that may contribute to bacterial resistance. Further work will be required to explore the efficacy and potential use of hydroquinine in the clinic.

A comparison study about antibacterial activity of zeolitic imidazolate frameworks (ZIFs) prepared with various metal ions

Herein, the synthesis of zeolitic imidazolate framework particles in water at room temperature using 2-methylimidazole (HmIm) as organic linker, and Co(II), Ni(II), Cu(II), Fe(II), Mg(II), Zn(II), Ce(III), La(III), Fe(III), and Ti(IV) ions is reported. The colors of the prepared ZIF particles varied depending on the metal ions used. The disappearance of NHring-N out of plane bending peak at 1845 cm−1 and weakening of the NH bending peak at 1597 cm−1 in the FT-IR spectrum of HmIm after ZIF synthesis confirmed successful preparation. Higher surface area values were observed for ZIF-Co(II) and ZIF-Zn(II) with values of 1423.4 and 1467.1 m2/g, respectively. The prepared ZIF-Fe(II) particles showed magnetic property. The antibacterial activities of ZIF particles also varied depending on metal ions. The highest antibacterial activities were observed for ZIF-Co(II) and ZIF-Cu(II) particles against P. aeruginosa (gram -, ATCC 10145), S. aureus (gram +, ATCC 6538), and C. albicans (fungi, ATCC 10231). The MIC values of ZIF-Co(II) particles were determined as 0.125, 0.25, and 1.0 mg/mL against P. aeruginosa, S. aureus, and C. albicans, whereas MBC values were determined as 0.25, 1.0, and 5.0 mg/mL, respectively. The inhibition zones for P. aeruginosa, S. aureus, and C. albicans in the presence of 10 mg ZIF-Cu(II) particles were measured as 22.7 ± 1.5, 24.3 ± 1.1, and 25.7 ± 0.6 mm, respectively.

Preliminary Study on Phytochemical Constituents and Biological Activities of Essential Oil from Myriactis nepalensis Less.

In response to the need for novel therapeutic strategies to combat the development of microbial resistance, plant essential oils may represent a promising alternative source. This study set out to characterize the chemical composition and assess the antibacterial potential of Myriactis nepalensis Less. essential oil (MNEO). Essential oil isolated from M. nepalensis by hydrodistillation was analyzed using a GC–MS technique. The antibacterial properties of MNEO alone and combined with antibiotics (chloramphenicol and streptomycin) were tested via the disc diffusion, microbroth dilution, and checkerboard methods. MNEO was represented by oxygenated sesquiterpenes (60.3%) and sesquiterpene hydrocarbons (28.6%), with caryophyllene oxide, spathulenol, humulene epoxide II, β-elemene, neointermedeol, and β-caryophyllene as the main compounds. MNEO exhibited a strong antibacterial effect against Gram-positive bacteria, with MIC and MBC values of 0.039 mg/mL and 0.039–0.156 mg/mL, respectively, and synergistic effects were observed in both combinations with chloramphenicol and streptomycin. Furthermore, the antibiofilm and cytotoxic activities of MNEO were also evaluated. The crystal violet assay was used for quantification of Staphylococcus aureus biofilm formation, and an MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay was conducted to determine cell viability. The results revealed MNEO could dose-dependently inhibit Staphylococcus aureus biofilm formation and possessed potential cytotoxic on both normal and cancer cells (IC50 values from 13.13 ± 1.90 to 35.22 ± 8.36 μg/mL). Overall, the results indicate that MNEO may have promising applications in the field of bacterial infections.

Novel Chloro-Substituted Salicylanilide Derivatives and Their β-Cyclodextrin Complexes: Synthesis, Characterization, and Antibacterial Activity.

The goal of this research was to design novel chloro-substituted salicylanilide derivatives and their β-cyclodextrin complexes in order to obtain efficient antibacterial compounds and to demonstrate the beneficial role of complexation on the efficiency of these compounds. Thus, salicylanilide derivatives, esters, and hydrazides were obtained by microwave-assisted synthesis and their structure proven based on FTIR and NMR spectra. In order to improve water solubility, chemical and physical stability, and drug distribution through biological membranes, the inclusion complexes of the ethyl esters in β-cyclodextrin were also obtained using kneading. Inclusion-complex characterization was accomplished by modern analytical methods, X-ray diffraction, SEM, TGA, FTIR, and UV-vis spectroscopy. The newly synthesized compounds were tested against some Gram-positive and Gram-negative bacteria. Antimicrobial tests revealed good activity on Gram-positive bacteria and no inhibition against Gram-negative strains. The MIC and MBC values for compounds derived from N-(2-chlorophenyl)-2-hydroxybenzamide were 0.125–1.0 mg/mL. N-(4-chlorophenyl)-2-hydroxybenzamide derivatives were found to be less active. The inclusion complexes generally behaved similarly to the guest compounds, and antibacterial activity was not been altered by complexation.

Progression-free survival and quality of life in metastatic breast cancer: The patient perspective

IntroductionTreatment advances for metastatic breast cancer (mBC) have improved overall survival (OS) in some mBC subtypes; however, there remains no cure for mBC. Considering the use of progression-free survival (PFS) and other surrogate endpoints in clinical trials, we must understand patient perspectives on measures used to assess treatment efficacy. ObjectiveTo explore global patient perceptions of the concept of PFS and its potential relation to quality of life (QoL). Materials and methodsVirtual roundtables in Europe and the United States and interviews in Japan with breast cancer patients, patient advocates, and thought leaders. Discussions were recorded, transcribed, and analyzed thematically. ResultsLengthened OS combined with no worsening or improvement in QoL remain the most important endpoints for mBC patients. Time when the disease is not progressing is meaningful to patients when coupled with improvements in QoL and no added treatment toxicity. Clinical terminology such as “PFS” is not well understood, and participants underscored the need for patient-friendly terminology to better illustrate the concept. Facets of care that patients with mBC value and that may be related to PFS include relief from cancer-related symptoms and treatment-related toxicities as well as the ability to pursue personal goals. Improved communication between patients and providers on managing treatment-related toxicities and addressing psychosocial challenges to maintain desired QoL is needed. ConclusionWhile OS and QoL are considered the most relevant endpoints, patients also value periods of time without disease progression. Incorporation of these considerations into the design and conduct of future clinical trials in mBC, as well as HTA and reimbursement decision-making, is needed to better capture the potential value of a therapeutic innovation.

An in vitro comparison of antimicrobial efficacy and cytotoxicity between povidone-iodine and chlorhexidine for treating clinical endometritis in dairy cows.

This study aimed to assess the in vitro antimicrobial effects of chlorhexidine (CHX) and povidone-iodine (PI) on clinical isolates of Escherichia coli (E. coli) and Trueperella pyogenes (T. pyogenes) from the vaginal discharge of dairy cows, as well as to compare the cytotoxicity effects of CHX and PI on bovine endometrial epithelial cells (BEnEpC). In Experiment 1, 12 E. coli and 10 T. pyogenes were isolated from the vaginal discharge of cows with a uterine infection. The MIC and MBC against CHX and PI were analyzed in vitro. In Experiment 2, the cytotoxicity effects of CHX and PI on BEnEpC were analyzed using a Viability/Cytotoxicity Kit, wound scratch healing assay, and the expression of pro-inflammatory cytokine genes (IL-6, IL-8, and TNF-α). In Experiment 1, the MIC and MBC values of CHX against E. coli were 0.0002% and 0.0002 to 0.00025%, respectively. The MIC and MBC values of PI were 1.25 to 2.5% and 1.25 to 5%, respectively. For T. pyogenes, the MIC and MBC values of CHX were 0.00002%. The MIC and MBC values of PI were 1.25%. In Experiment 2, the cell viability significantly decreased, and wound closures were significantly inhibited after treatment with ≥ 0.002% CHX and ≥ 0.025% PI. The expression of IL-6, IL-8, and TNF-α significantly increased after treatment with PI. Only IL-6 showed a significant increase after cells were treated with 0.00002% and 0.0002% CHX. The results suggested that both CHX and PI had high antibacterial effects. However, veterinarians and farmers should be aware of their cytotoxicity, which decrease viability of endometrial epithelial cells and inhibit wound healing in vitro.

BioMOF-Mn: An Antimicrobial Agent and an Efficient Nanocatalyst for Domino One-Pot Preparation of Xanthene Derivatives.

In this paper, a new Mn-based metal-organic framework [UoB-6] was obtained via a one-step ultrasonic irradiation method with the ligand (H2bdda: 4,4'-(1,4-phenylenebis(azaneylylidene))bis(methaneylylidene))dibenzoic acid. The structural integrity of the synthesized BioMOF-Mn was corroborated by FT-IR, EDX, ICP, XRD, TEM, DLS, FESEM, and BET-BJH analyses. The aerobic oxidative domino reaction of benzyl alcohols or aldehydes with dimedone derivatives was performed in the presence of the UoB-6 catalyst to produce xanthene derivatives in good yields. Hot filtration and Hg poisoning tests proved the heterogeneous nature of the catalyst. Novel synthesized xanthene-based bis-aldehydes were introduced as potent HDAC1 inhibitors according to molecular docking calculations. Finally, the inhibitory activities of Mn-MOF nanoparticles were evaluated on Escherichia coli and Candida albicans. The MIC, MBC, and MFC values were determined from 2048 to 4096 μg·mL-1 according to antimicrobial susceptibility testing methods. The inhibitory effects of antimicrobial agents can be exacerbated when loaded on BioMOFs.

AKTIVITAS ANTIMIKROBA EKSTRAK ETANOL BATANG WOLE WOE ASAL HALMAHERA TENGAH TERHADAP BAKTERI GRAM POSITIF Staphylococcus epidermidis DAN Staphylococcus aureus

The wole woe plant is one of the plants empirically used by the Weda community in Central Halmahera district as a traditional medicine to treat various diseases such as breast cancer, cysts, vaginal discharge, diabetes mellitus, wounds, dysentery, cholesterol, and gout. Therefore, a study was conducted on the antimicrobial activity of the ethanolic extract of wole woe stems against gram-positive bacteria S. epidermidis and S. aureus with the aim of determining the concentration that provides antimicrobial activity of the ethanolic extract of wole woe stems by using the agar diffusion method. The results obtained in the screening test gave activity at a concentration of 0.1% and the results of the minimum inhibitory concentration test (MIC) and the minimum killing concentration test (MBC) obtained a MIC value of 1.6% for S. epidermidis bacteria and 0.8% for S. aureus bacteria, while the MBC value is 1.6% for both bacteria. The results of statistical tests on the diameter of the inhibition zone from the antimicrobial activity test against S. epidermidis and S. aureus , showed that there was a difference in the ability to inhibit bacterial growth between the positive control and the test concentration group of 2.5%, 5% and 10%. In the ratio of the inhibitory ability of bacteria at a spesific concentration, the test results showed that S. epidermidis bacteria had different bacterial growth inhibition abilities with S. aureus bacteria. Based on the results obtained, the ethanol extract of wole woe stems has potential as an antimicrobial.

Essential Oils From Citrus unshiu Marc. Effectively Kill Aeromonas hydrophila by Destroying Cell Membrane Integrity, Influencing Cell Potential, and Leaking Intracellular Substances.

Aeromonas hydrophila is one of the important pathogenic bacteria in aquaculture causing serious losses every year. Essential oils are usually used as natural antimicrobial agents to reduce or replace the use of antibiotics. The aim of this study was to evaluate the antibacterial activity and explore the mechanisms of essential oil from satsuma mandarin (Citrus unshiu Marc.) (SMEO) against A. hydrophila. The results of the gas chromatography-mass spectrometer demonstrated that SMEO contains 79 chemical components with the highest proportion of limonene (70.22%). SMEO exhibited strong antibacterial activity against A. hydrophila in vitro, the diameter of the inhibition zone was 31.22 ± 0.46 mm, and the MIC and MBC values were all 1% (v/v). Intracellular material release, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and flow cytometry analysis revealed the dynamic antibacterial process of SMEO, the morphological changes of bacterial cells, and the leakage process of intracellular components. These results demonstrated that SMEO disrupted the extracellular membrane permeability. Our study demonstrated that SEMO has the potential to be used to control and prevent A. hydrophila infections in aquaculture.

Self-polishing antifouling coatings based on benzamide derivatives containing capsaicin

In this study, N-hydroxymethylbenzamide was alkylated with various aromatic compounds to obtain five novel benzamide derivatives containing capsaicin (BDCC), and the BDCC were incorporated into coatings as auxiliary agents. The relationships between properties and structures were discussed based on experimental and theoretical results. The theoretical results showed the optimized configurations of BDCC and confirmed that the benzene ring, phenolic hydroxyl, ester and amide groups were active sites. Experimental results indicated that the antimicrobial and antifouling effects of compounds b1, b2 and b3 were better than those of chlorothalonil, their MIC and MBC values were no more than 64 and 512 μg·mL−1, and their test panels were covered only with small amounts of dirt and biofilms; they worked well as green antifouling additives. The experimental and theoretical results showed that BDCC and BDCC antifouling coatings were effective and eco-friendly.

Crude extracts of an endophytic fungus attenuate the growth of pathogenic bacteria in aquaculture.

Endophytic fungi are believed to possess compounds as antibacterial agents. This study was designed to determine in vivo antibacterial activity of the crude extracts from Lasiodiplodia pseudotheobromae IBRL OS-64 against pathogenic bacteria. The qualitative and quantitative screenings were performed using agar plug and disk diffusion antimicrobial tests, respectively. Besides that, the MIC and MBC value of the extracts were determined using broth microdilution assay and morphological changes of the bacterial cells exposed to the extract were observed under Scanning Electron Microscope (SEM). Agar plug diffusion assay revealed that V. parahaemolyticus ATCC 17802 and Exiguobacterium profundum IBRL MA6 were the most sensitive to the extract with the size of inhibition zones of 11 to ≤ 20 mm. The MIC and MBC values of the extract varied depending on the test bacteria. Observation through SEM revealed that the bacterial cells exposed to the extract experienced severe damage such as irregular shape with crumpled and shrunken cells which led to cell death. The data suggest that the crude extracts of L. pseudotheobromae IBRL OS-64 exert antibacterial activity against test bacteria and principally affect the cell wall in growing pathogenic bacterial cells.

Investigation on characterization, antifouling and cytotoxic properties of zinc oxide nanoparticles biosynthesized by a mangrove-associated actinobacterium Streptomyces olivaceus (MSU3).

The present study was undertaken to biosynthesize zinc oxide nanoparticles (ZnONPs) using a mangrove-associated actinobacterium Streptomyces olivaceus (MSU3) under in vitro conditions. The synthesized ZnONPs were structurally characterized through UV, FT-IR, TG-DTA, XRD, SEM and EDX analysis. Analysis of biosynthesized ZnONPs in UV-Vis spectroscopy showed presence of functional groups between the wavelengths 325 and 380nm. FT-IR analysis showed the functional groups, such as halo bromide (C-Br), alkyne (C≡C), carboxylic acid (O-H), nitro (N-O), fluoro (C-F), alkene (C=C) and aromatic (R-C-H) groups, respectively, within the wave numbers between 614.30 and 3074.41cm-1. The crystalline poly-dispersed quasi spherical nature of ZnONPs expressed the average particle size of 37.9nm with the 2θ values of 11.802-37.885°. Antibacterial activity of ZnONPs showed pronounced inhibitory zone (25mm) and least MIC and MBC values (125 and 250µgml-1) against Escherchia sp. In the antifouling study, ZnONPs strongly inhibited byssal thread formation in mussel Perna indica and recorded LC50 value of 424.47µgml-1. Mollusc foot adherence assay inferred that the ZnONPs effectively inhibited settlement of limpet Patella vulgata and showed minimal fouling (26.43%) at 350µgml-1 and recorded LC50 value of 218.77µgml-1. Results of anticrustacean assay depicted that, ZnONPs had registered LC50 value of 676.08µgml-1 against Artemia salina nauplii. From this study, it could be concluded that an eco-friendly approach could be used to open a new avenue for biosynthesis of ZnONPs from a mangrove associated actinobacterium S. olivaceus (MSU3) in antifouling studies.