Displaying publications 81 - 100 of 139 in total

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  1. Synthesis of halogenated azo-aspirin analogues from natural product derivatives as the potential antibacterial agents
    Ngaini Z, Mortadza NA
    Nat Prod Res, 2019 Dec;33(24):3507-3514.
    PMID: 29911437 DOI: 10.1080/14786419.2018.1486310
    Chemical modification of medicines from natural product-based molecules has become of interest in recent years. In this study, a series of halogenated azo derivatives 1a-d were synthesised via coupling reaction, followed by Steglich esterification with aspirin (a natural product derivative) to form azo derivatives 2a-d. While, halogenated azo-aspirin 3a-d were synthesised via direct coupling reaction of aspirin and diazonium salt. Bacteriostatic activity was demonstrated against E. coli and S. aureus via turbidimetric kinetic method. Compound 3a-d showed excellent antibacterial activities against E. coli (MIC 75-94 ppm) and S. aureus (MIC 64-89 ppm) compared to ampicillin (MIC 93 and 124 ppm respectively), followed by 1a-d and 2a-d. The presence of reactive groups of -OH, N=N, C=O and halogens significantly contribute excellent interaction towards E. coli and S. aureus. Molecular dockings analysis of 3a against MIaC protein showed binding free energy of -7.2 kcal/mol (E. coli) and -6.6 kcal/mol (S. aureus).
    Matched MeSH terms: Escherichia coli/drug effects
  2. Antibacterial and wound healing analysis of gelatin/zeolite scaffolds
    Ninan N, Muthiah M, Bt Yahaya NA, Park IK, Elain A, Wong TW, et al.
    Colloids Surf B Biointerfaces, 2014 Mar 1;115:244-52.
    PMID: 24362063 DOI: 10.1016/j.colsurfb.2013.11.048
    In this article, gelatin/copper activated faujasites (CAF) composite scaffolds were fabricated by lyophilisation technique for promoting partial thickness wound healing. The optimised scaffold with 0.5% (w/w) of CAF, G (0.5%), demonstrated pore size in the range of 10-350 μm. Agar disc diffusion tests verified the antibacterial role of G (0.5%) and further supported that bacterial lysis was due to copper released from the core of CAF embedded in the gelatin matrix. The change in morphology of bacteria as a function of CAF content in gelatin scaffold was studied using SEM analysis. The confocal images revealed the increase in mortality rate of bacteria with increase in concentration of incorporated CAF in gelatin matrix. Proficient oxygen supply to needy cells is a continuing hurdle faced by tissue engineering scaffolds. The dissolved oxygen measurements revealed that CAF embedded in the scaffold were capable of increasing oxygen supply and thereby promote cell proliferation. Also, G (0.5%) exhibited highest cell viability on NIH 3T3 fibroblast cells which was mainly attributed to the highly porous architecture and its ability to enhance oxygen supply to cells. In vivo studies conducted on Sprague Dawley rats revealed the ability of G (0.5%) to promote skin regeneration in 20 days. Thus, the obtained data suggest that G (0.5%) is an ideal candidate for wound healing applications.
    Matched MeSH terms: Escherichia coli/drug effects
  3. Fulltext Inactivating pathogenic bacteria in greywater by biosynthesized Cu/Zn nanoparticles from secondary metabolite of Aspergillus iizukae; optimization, mechanism and techno economic analysis
    Noman E, Al-Gheethi A, Talip BA, Mohamed R, Kassim AH
    PLoS One, 2019;14(9):e0221522.
    PMID: 31513594 DOI: 10.1371/journal.pone.0221522
    The inactivation of antibiotic resistant Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive) seeded in greywater by bimetallic bio-nanoparticles was optimized by using response surface methodology (RSM). The bimetallic nanoparticles (Cu/Zn NPs) were synthesized in secondary metabolite of a novel fungal strain identified as Aspergillus iizukae EAN605 grown in pumpkin medium. Cu/Zn NPs were very effective for inhibiting growth of E. coli and S. aureus. The maximum inactivation was optimized with 0.028 mg mL-1 of Cu/Zn NPs, at pH 6 and after 60 min, at which the reduction of E. coli and S. aureus was 5.6 vs. 5.3 and 5.2 vs. 5.4 log reduction for actual and predicted values, respectively. The inactivation mechanism was described based on the analysis of untreated and treated bacterial cells by Field emission scanning electron microscopy (FESEM), Energy Dispersive X-Ray Spectroscopy (EDS), Atomic Force Microscopy (AFM) revealed a damage in the cell wall structure due to the effect of Cu/Zn NPs. Moreover, the Raman Spectroscopy showed that the Cu/Zn NPs led to degradation of carbohydrates and amino structures on the bacteria cell wall. The Fourier transform infrared spectroscopy (FTIR) analysis confirmed that the destruction take place in the C-C bond of the functional groups available in the bacterial cell wall. The techno economic analysis revealed that the biosynthesis Cu/Zn NPs is economically feasible. These findings demonstrated that Cu/Zn NPs can effectively inhibit pathogenic bacteria in the greywater.
    Matched MeSH terms: Escherichia coli/drug effects
  4. Optimal methods for evaluating antimicrobial activities from plant extracts
    Othman M, Loh HS, Wiart C, Khoo TJ, Lim KH, Ting KN
    J Microbiol Methods, 2011 Feb;84(2):161-6.
    PMID: 21094190 DOI: 10.1016/j.mimet.2010.11.008
    The search for antimicrobial agents from plants has been a growing interest in the last few decades. However, results generated from many of these studies cannot be directly compared due to the absence of standardization in particular antimicrobial methods employed. The need for established methods with consistent results for the evaluation of antimicrobial activities from plant extracts has been proposed by many researchers. Nevertheless, there are still many studies reported in the literature describing different methodologies. The aim of this study was to find optimal methods to give consistent quantitative antimicrobial results for studying plant extracts. Three different agar-based assays (pour plate disc diffusion (PPDD), streak plate disc diffusion (SPDD) and well-in agar (WA)) and one broth-based (turbidometric (TB)) assay were used in this study. Extracts from two plant species (Duabanga grandiflora and Acalypha wilkesiana) were tested on two bacterial species, namely Escherichia coli and Staphylococcus aureus. Amongst the agar-based assays, PPDD produced the most reproducible results. TB was able to show the inhibitory effects of the test samples on the growth kinetic of the bacteria including plant extracts with low polarity. We propose that both agar- (i.e PPDD) and broth-based assays should be employed when assessing the antimicrobial activity of plant crude extracts.
    Matched MeSH terms: Escherichia coli/drug effects*
  5. Extended-spectrum beta-lactam resistance due to AmpC hyperproduction and CMY-2 coupled with the loss of OMPK35 in Malaysian strains of Escherichia coli and Klebsiella pneumoniae
    Palasubramaniam S, Subramaniam G, Muniandy S, Parasakthi N
    Microb Drug Resist, 2007;13(3):186-90.
    PMID: 17949305
    In this report, we describe the detection of AmpC and CMY-2 beta-lactamases with the loss of OmpK35 porin among seven sporadic strains of ceftazidime-resistant Klebsiella pneumoniae and ceftazidime-resistant Escherichia coli. Cefoxitin, which was used as a marker of resistance toward 7-alpha-methoxy-cephalosporins, exhibited high minimum inhibitory concentration (MIC) values ranging between 128 microg/ml and >256 microg/ml in all the strains. The presence of hyperproducing AmpC enzymes was indicated by the positive three-dimensional test. Isoelectric focusing (IEF) study confirmed the presence of AmpC enzymes in all the strains. The ampC gene was detected by PCR in all the strains and confirmed by DNA sequencing. Large plasmids in all the strains, ranging from 60 kb to 150 kb in size, most likely encode the ampC gene. Two E. coli strains out of the seven strains showed positive amplification of the bla(CMY-2) gene, an AmpC variant, and was confirmed by DNA sequence analyses. DNA hybridization confirmed the bla(CMY-2) gene to be plasmid-mediated in both of these strains. However, one of these two strains also mediated a chromosomal CMY gene. All the strains showed an absence of OmpK35 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS/PAGE) and was confirmed by western blot analyses using raised polyclonal anti-OmpK35 antiserum. This suggests that, apart from CMY production, absence of OmpK35 porin also contributed to cefoxitin resistance resulting in extended-spectrum beta-lactam resistance among these isolates.
    Matched MeSH terms: Escherichia coli/drug effects*
  6. Membrane-lytic actions of sulphonated methyl ester surfactants and implications to bactericidal effect and cytotoxicity
    Pan F, Li Z, Gong H, Petkov JT, Lu JR
    J Colloid Interface Sci, 2018 Dec 01;531:18-27.
    PMID: 30015167 DOI: 10.1016/j.jcis.2018.07.031
    Surfactants are multifunctional molecules widely used in personal care and healthcare formulations to cleanse, help disperse active ingredients (e.g., forming emulsions) and stabilise products. With increasing demands on improving biosafety, there is now mounting pressure to understand how different surfactants elicit toxicities at molecular and cellular levels. This work reports the membrane-lytic behaviour of a group of sulphonated methyl ester (SME) surfactants together with representative conventional surfactants. All surfactants displayed the clear rise of lysis of the model lipid bilayer membranes around their CMCs, but the two ionic surfactants SDS and C12TAB even caused measurable lysis below their CMCs, with membrane-lytic actions increasing with monomer concentration. Furthermore, whilst ionic and nonionic surfactants could achieve full membrane lysis once above their CMCs, this ability was weak from the SME surfactants and decreased with increasing the acyl chain length. In contrast to the conventional anionic surfactants such as SDS and SLES, the protein solubilizing capability of the SME surfactants was also low. On the other hand, MTT assays against 3T3 fibroblast cells and human chondrocyte cells revealed high toxicity from SDS and C12TAB against the other surfactants studied, but the difference between SME and the rest of conventional surfactants was small. Similar behaviour was also observed in their bactericidal effect against E. coli and S. aureus. The trend is broadly consistent with their membrane-lytic behaviour, indicating little selectivity in their cytotoxicity and bactericidal action. These results thus reveal different toxicities implicated from different surfactant head groups. Increase in acyl chain length as observed from SME surfactants could help improve surfactant biocompatibility.
    Matched MeSH terms: Escherichia coli/drug effects*
  7. Fulltext 4'-O-substitutions determine selectivity of aminoglycoside antibiotics
    Perez-Fernandez D, Shcherbakov D, Matt T, Leong NC, Kudyba I, Duscha S, et al.
    Nat Commun, 2014;5:3112.
    PMID: 24473108 DOI: 10.1038/ncomms4112
    Clinical use of 2-deoxystreptamine aminoglycoside antibiotics, which target the bacterial ribosome, is compromised by adverse effects related to limited drug selectivity. Here we present a series of 4',6'-O-acetal and 4'-O-ether modifications on glucopyranosyl ring I of aminoglycosides. Chemical modifications were guided by measuring interactions between the compounds synthesized and ribosomes harbouring single point mutations in the drug-binding site, resulting in aminoglycosides that interact poorly with the drug-binding pocket of eukaryotic mitochondrial or cytosolic ribosomes. Yet, these compounds largely retain their inhibitory activity for bacterial ribosomes and show antibacterial activity. Our data indicate that 4'-O-substituted aminoglycosides possess increased selectivity towards bacterial ribosomes and little activity for any of the human drug-binding pockets.
    Matched MeSH terms: Escherichia coli/drug effects
  8. Isolation and bioactivities of constitutents of the roots of Garcinia atroviridis
    Permana D, Lajis NH, Mackeen MM, Ali AM, Aimi N, Kitajima M, et al.
    J Nat Prod, 2001 Jul;64(7):976-9.
    PMID: 11473441
    Two new prenylated compounds, the benzoquinone atrovirinone (1) and the depsidone atrovirisidone (2), were isolated from the roots of Garcinia atroviridis. Their structures were determined on the basis of the analysis of spectroscopic data. While compound 2 showed some cytotoxicity against HeLa cells, both compounds 1 and 2 were only mildly inhibitory toward Bacillus cereus and Staphylococcus aureus.
    Matched MeSH terms: Escherichia coli/drug effects
  9. Modifications in the pmrB gene are the primary mechanism for the development of chromosomally encoded resistance to polymyxins in uropathogenic Escherichia coli
    Phan MD, Nhu NTK, Achard MES, Forde BM, Hong KW, Chong TM, et al.
    J Antimicrob Chemother, 2017 10 01;72(10):2729-2736.
    PMID: 29091192 DOI: 10.1093/jac/dkx204
    Objectives: Polymyxins remain one of the last-resort drugs to treat infections caused by MDR Gram-negative pathogens. Here, we determined the mechanisms by which chromosomally encoded resistance to colistin and polymyxin B can arise in the MDR uropathogenic Escherichia coli ST131 reference strain EC958.

    Methods: Two complementary approaches, saturated transposon mutagenesis and spontaneous mutation induction with high concentrations of colistin and polymyxin B, were employed to select for mutations associated with resistance to polymyxins. Mutants were identified using transposon-directed insertion-site sequencing or Illumina WGS. A resistance phenotype was confirmed by MIC and further investigated using RT-PCR. Competitive growth assays were used to measure fitness cost.

    Results: A transposon insertion at nucleotide 41 of the pmrB gene (EC958pmrB41-Tn5) enhanced its transcript level, resulting in a 64- and 32-fold increased MIC of colistin and polymyxin B, respectively. Three spontaneous mutations, also located within the pmrB gene, conferred resistance to both colistin and polymyxin B with a corresponding increase in transcription of the pmrCAB genes. All three mutations incurred a fitness cost in the absence of colistin and polymyxin B.

    Conclusions: This study identified the pmrB gene as the main chromosomal target for induction of colistin and polymyxin B resistance in E. coli.

    Matched MeSH terms: Uropathogenic Escherichia coli/drug effects
  10. In vitro evaluation of the growth enhancing or cytotoxic effect of Sticophus species (Gamat) on established human fibroblast cell lines and antimicrobial activity
    Philip R, Dinsuhaimi S, Rosdan S, Samsudin AR, Shamsuria O, Mohd Zaki S, et al.
    Med J Malaysia, 2004 May;59 Suppl B:95-6.
    PMID: 15468835
    Matched MeSH terms: Escherichia coli/drug effects
  11. Elastomeric biocomposite of silver-containing mesoporous bioactive glass and poly(1,8-octanediol citrate): Physiochemistry and in vitro antibacterial capacity in tissue engineering applications
    Pourshahrestani S, Zeimaran E, Kadri NA, Gargiulo N, Jindal HM, Hasikin K, et al.
    Mater Sci Eng C Mater Biol Appl, 2019 May;98:1022-1033.
    PMID: 30812986 DOI: 10.1016/j.msec.2019.01.022
    A novel series of silver-doped mesoporous bioactive glass/poly(1,8-octanediol citrate) (AgMBG/POC) elastomeric biocomposite scaffolds were successfully constructed by a salt-leaching technique for the first time and the effect of inclusion of different AgMBG contents (5, 10, and 20 wt%) on physicochemical and biological properties of pure POC elastomer was evaluated. Results indicated that AgMBG particles were uniformly dispersed in the POC matrix and increasing the AgMBG concentration into POC matrix up to 20 wt% enhanced thermal behaviour, mechanical properties and water uptake ability of the composite scaffolds compared to those from POC. The 20%AgMBG/POC additionally showed higher degradation rate in Tris(hydroxymethyl)-aminomethane-HCl (Tris-HCl) compared with pure POC and lost about 26% of its initial weight after soaking for 28 days. The AgMBG phase incorporation also significantly endowed the resulting composite scaffolds with efficient antibacterial properties against Escherichia coli and Staphylococcus aureus bacteria while preserving their favorable biocompatibility with soft tissue cells (i.e., human dermal fibroblast cells). Taken together, our results suggest that the synergistic effect of both AgMBG and POC make these newly designed AgMBG/POC composite scaffold an attractive candidate for soft tissue engineering applications.
    Matched MeSH terms: Escherichia coli/drug effects
  12. Antibacterial activity in vitro of Thymus capitatus from Jordan
    Qaralleh HN, Abboud MM, Khleifat KM, Tarawneh KA, Althunibat OY
    Pak J Pharm Sci, 2009 Jul;22(3):247-51.
    PMID: 19553168
    This study was carried out to evaluate the antibacterial activity of aqueous and organic extracts of Thymus capitatus L. (Lamiaceae) leaves and stems. Dried ground powder leaves and stems were extracted with water (aqueous extracts), ethanol, dichloromethane and hexane (Soxhlet extracts). The antibacterial activity of these extracts was evaluated against bacteria using disc diffusion method. The result obtained showed that the leaves had stronger antibacterial activity than the stems extracts. The ethanolic extract had the highest yield products and the high antibacterial activity than all other solvents. The results suggest that essential oil as non-polar organic compounds could be the main active compounds in this plant. Therefore the antibacterial activity of leaves ethanol extracts (LEE) was compared with essential oils leaves extracts (LEO) of T. capitatus. The LEO showed greater antibacterial activity than LEE. The LEO showed a broad spectrum of antibacterial activity and the Pseudomonas aeruginosa was the most sensitive bacteria.
    Matched MeSH terms: Escherichia coli/drug effects
  13. Fulltext Aluminosilicate Nanocomposites from Incinerated Chinese Holy Joss Fly Ash: A Potential Nanocarrier for Drug Cargos
    Ramanathan S, Gopinath SCB, Md Arshad MK, Poopalan P, Anbu P, Lakshmipriya T
    Sci Rep, 2020 Feb 25;10(1):3351.
    PMID: 32099019 DOI: 10.1038/s41598-020-60208-x
    An incredible amount of joss fly ash is produced from the burning of Chinese holy joss paper; thus, an excellent method of recycling joss fly ash waste to extract aluminosilicate nanocomposites is explored. The present research aims to introduce a novel method to recycle joss fly ash through a simple and straightforward experimental procedure involving acidic and alkaline treatments. The synthesized aluminosilicate nanocomposite was characterized to justify its structural and physiochemical characteristics. A morphological analysis was performed with field-emission transmission electron microscopy, and scanning electron microscopy revealed the size of the aluminosilicate nanocomposite to be ~25 nm, while also confirming a uniformly spherical-shaped nanostructure. The elemental composition was measured by energy dispersive spectroscopy and revealed the Si to Al ratio to be 13.24 to 7.96, showing the high purity of the extracted nanocomposite. The roughness and particle distribution were analyzed using atomic force microscopy and a zeta analysis. X-ray diffraction patterns showed a synthesis of faceted and cubic aluminosilicate crystals in the nanocomposites. The presence of silica and aluminum was further proven by X-ray photoelectron spectroscopy, and the functional groups were recognized through Fourier transform infrared spectroscopy. The thermal capacity of the nanocomposite was examined by a thermogravimetric analysis. In addition, the research suggested the promising application of aluminosilicate nanocomposites as drug carriers. The above was justified by an enzyme-linked apta-sorbent assay, which claimed that the limit of the aptasensing aluminosilicate-conjugated ampicillin was two-fold higher than that in the absence of the nanocomposite. The drug delivery property was further justified through an antibacterial analysis against Escherichia coli (gram-negative) and Bacillus subtilis (gram-positive).
    Matched MeSH terms: Escherichia coli/drug effects
  14. Fulltext The effect of environmental conditions on biofilm formation of Burkholderia pseudomallei clinical isolates
    Ramli NS, Eng Guan C, Nathan S, Vadivelu J
    PLoS One, 2012;7(9):e44104.
    PMID: 22970167 DOI: 10.1371/journal.pone.0044104
    Burkholderia pseudomallei, a Gram-negative saprophytic bacterium, is the causative agent of the potentially fatal melioidosis disease in humans. In this study, environmental parameters including temperature, nutrient content, pH and the presence of glucose were shown to play a role in in vitro biofilm formation by 28 B. pseudomallei clinical isolates, including four isolates with large colony variants (LCVs) and small colony variants (SCVs) morphotypes. Enhanced biofilm formation was observed when the isolates were tested in LB medium, at 30 °C, at pH 7.2, and in the presence of as little as 2 mM glucose respectively. It was also shown that all SVCs displayed significantly greater capacity to form biofilms than the corresponding LCVs when cultured in LB at 37 °C. In addition, octanoyl-homoserine lactone (C(8)-HSL), a quorum sensing molecule, was identified by mass spectrometry analysis in bacterial isolates referred to as LCV CTH, LCV VIT, SCV TOM, SCV CTH, 1 and 3, and the presence of other AHL's with higher masses; decanoyl-homoserine lactone (C(10)-HSL) and dodecanoyl-homoserine lactone (C(12)-HSL) were also found in all tested strain in this study. Last but not least, we had successfully acquired two Bacillus sp. soil isolates, termed KW and SA respectively, which possessed strong AHLs degradation activity. Biofilm formation of B. pseudomallei isolates was significantly decreased after treated with culture supernatants of KW and SA strains, demonstrating that AHLs may play a role in B. pseudomallei biofilm formation.
    Matched MeSH terms: Escherichia coli/drug effects
  15. D-glucosamine chitosan base molecule-assisted synthesis of different shape and sized silver nanoparticles by a single pot method: A greener approach for sensor and microbial applications
    Ranjani B, Pandian K, Kumar GA, Gopinath SCB
    Int J Biol Macromol, 2019 Jul 15;133:1280-1287.
    PMID: 31051204 DOI: 10.1016/j.ijbiomac.2019.04.196
    Silver nanoparticle was synthesized using D-glucosamine chitosan base as green reducing agent at elevated temperature in alkaline pH ranges. The excess of D-glucosamine chitosan base was used as it is both stabilizing and reducing agent at different pHs, regulates the shape and size of the silver nanoparticles. The progressive growth of silver nanoparticles was monitored by UV-Visible spectral studies. A sharp peak at 420 nm indicates the formation of spherical silver nanoparticles. The size and shape of silver nanoparticles were observed from Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) methods. The anisotropically grown nanoparticles were used as probe for Surface Enhanced Raman Studies (SERS) using ATP (4-aminothiophenol) as a model system. The catalytic behavior of silver nanoparticles was exploited for 4-nitrophenol reduction and observed that the reduction reaction follows pseudo first order kinetics with a rate constant 0.65 min. The antibacterial activity of silver nanoparticles was also tested for both gram-positive and -negative microorganisms, in which higher zone of inhibition was observed for gram negative microorganism.
    Matched MeSH terms: Escherichia coli/drug effects
  16. Synthesis, spectral analysis and antibacterial activity of some novel 5-substituted-2-((6-bromo-3,4-methylenedioxybenzyl)thio)-1,3,4-oxadiazole derivatives
    Rehman A, Siddiqa A, Abbasi MA, Siddiqui SZ, Khan SG, Rasool S, et al.
    Pak J Pharm Sci, 2018 Sep;31(5):1783-1790.
    PMID: 30150171
    A number of novel 5-substituted-2-((6-bromo-3,4-methylenedioxybenzyl)thio)-1,3,4-Oxadiazole derivatives (6a-l) have been synthesized to evaluate their antibacterial activity. Using aryl/aralkyl carboxylic acids (1a-l) as precursors, 5-substituted-1,3,4-Oxadiazol-2-thiols (4a-l) were yielded in good amounts. The derivatives, 4a-l, were subjected to electrophilic substitution reaction on stirring with 6-bromo-3,4-methylenedioxybenzyl chloride (5) in DMF to synthesize the required compounds. All the synthesized molecules were well characterized by IR, 1H-NMR, 13C-NMR and EIMS spectral data and evaluated for antibacterial activity against some bacterial strains of Gram-bacteria. The molecule, 6d, demonstrated the best activity among all the synthesized molecules exhibiting weak to moderate inhibition potential.
    Matched MeSH terms: Escherichia coli/drug effects
  17. Fulltext Growth profile and SEM analyses of Candida albicans and Escherichia coli with Hymenocallis littoralis (Jacq.) Salisb leaf extract
    Rosli N, Sumathy V, Vikneswaran M, Sreeramanan S
    Trop Biomed, 2014 Dec;31(4):871-9.
    PMID: 25776614 MyJurnal
    Hymenocallis littoralis (Jacq.) Salisb (Melong kecil) commonly known as 'Spider Lily' is an herbaceous plant from the family Amaryllidaceae. Study was carried out to determine the effect of H. littoralis leaf extract on the growth and morphogenesis of two pathogenic microbes, Candida albicans and Escherichia coli. The leaf extract displayed favourable anticandidal and antibacterial activity with a minimum inhibition concentration (MIC) of 6.25 mg/mL. Time kill study showed both microbes were completely killed after treated with leaf extract at 20 h. Both microbes' cell walls were heavily ruptured based on scanning electron microscopy (SEM) analysis. The significant anticandidal and antibacterial activities showed by H. littoralis leaf extract suggested the potential antimicrobial agent against C. albicans and E. coli.
    Matched MeSH terms: Escherichia coli/drug effects*
  18. Role of the cell envelope in the antibacterial activities of polymyxin B and polymyxin B nonapeptide against Escherichia coli
    Sahalan AZ, Dixon RA
    Int J Antimicrob Agents, 2008 Mar;31(3):224-7.
    PMID: 18083010
    The role of membrane permeabilisation and disruption in the mechanism of action of some polymyxin analogues against Gram-negative organisms is contentious. The effects of polymyxin B (PMB) and its analogue polymyxin B nonapeptide (PMBN) on Escherichia coli envelopes should correlate, but previous work by other workers suggests that PMBN has a different mode of action. This study has reassessed the biochemical techniques used previously and has shown that, in contrast to previous studies, PMBN (a well-characterised antibacterial synergist) readily releases periplasmic proteins and lipopolysaccharide from treated E. coli at subinhibitory concentrations in normal physiological buffer conditions. We conclude that, when tested with appropriate methodology, PMBN closely correlates with the early effects of PMB on the cell envelope of E. coli and this study shows that it is now consistent with the accepted interactions of membrane-active agents against Gram-negative cells.
    Matched MeSH terms: Escherichia coli/drug effects*
  19. Polydopamine as an intermediate layer for silver and hydroxyapatite immobilisation on metallic biomaterials surface
    Saidin S, Chevallier P, Abdul Kadir MR, Hermawan H, Mantovani D
    Mater Sci Eng C Mater Biol Appl, 2013 Dec 1;33(8):4715-24.
    PMID: 24094179 DOI: 10.1016/j.msec.2013.07.026
    Hydroxyapatite (HA) coated implant is more susceptible to bacterial infection as the micro-structure surface which is beneficial for osseointegration, could also become a reservoir for bacterial colonisation. The aim of this study was to introduce the antibacterial effect of silver (Ag) to the biomineralised HA by utilising a polydopamine film as an intermediate layer for Ag and HA immobilisation. Sufficient catechol groups in polydopamine were required to bind chemically stainless steel 316 L, Ag and HA elements. Different amounts of Ag nanoparticles were metallised on the polydopamine grafted stainless steel by varying the immersion time in silver nitrate solution from 12 to 24 h. Another polydopamine layer was then formed on the metallised film, followed by surface biomineralisation in 1.5 Simulated Body Fluid (SBF) solution for 3 days. Several characterisation techniques including X-Ray Photoelectron Spectroscopy, Atomic Force Microscopy, Scanning Electron Microscopy and Contact Angle showed that Ag nanoparticles and HA agglomerations were successfully immobilised on the polydopamine film through an element reduction process. The Ag metallisation at 24 h has killed the viable bacteria with 97.88% of bactericidal ratio. The Ag was ionised up to 7 days which is crucial to prevent bacterial infection during the first stage of implant restoration. The aged functionalised films were considered stable due to less alteration of its chemical composition, surface roughness and wettability properties. The ability of the functionalised film to coat complex and micro scale metal make it suitable for dental and orthopaedic implants application.
    Matched MeSH terms: Escherichia coli/drug effects
  20. Chemical compositions, antioxidant and antimicrobial activity of the essential oils of Piper officinarum (Piperaceae)
    Salleh WM, Ahmad F, Yen KH, Sirat HM
    Nat Prod Commun, 2012 Dec;7(12):1659-62.
    PMID: 23413576
    This study was designed to investigate the antioxidant and antimicrobial activities of the essential oils from Piper officinarum C. DC. GC and GC/MS analysis of the leaf and stem oils showed forty one components, representing 85.6% and 93.0% of the oil, respectively. The most abundant components in the leaf oil were beta-caryophyllene (11.2%), alpha-pinene (9.3%), sabinene (7.6%), beta-selinene (5.3%) and limonene (4.6%), while beta-caryophyllene (10.9%), alpha-phellandrene (9.3%), linalool (6.9%), limonene (6.7%) and alpha-pinene (5.0%) were the main components of the stem oil. The antioxidant activities were determined by using complementary tests: namely beta-carotene-linoleic acid, DPPH radical scavenging and total phenolic assays. The stems oil showed weak activity (IC50 = 777.4 microg/mL) in the DPPH system, but showed moderate lipid peroxidation inhibition in the beta-carotene-linoleic acid system (88.9 +/- 0.35%) compared with BHT (95.5 +/- 0.30%). Both oils showed weak activity against P. aeruginosa and E. coli with M IC values of 250 microg/mL.
    Matched MeSH terms: Escherichia coli/drug effects
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