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Gram Positive (gram + positive)
Selected AbstractsThe Influence of Tetracycline Loading on the Surface Morphology and Biocompatibility of Films Made from P(3HB) Microspheres,ADVANCED ENGINEERING MATERIALS, Issue 7 2010Lydia Francis Tetracycline, an antibiotic used against a broad range of Gram positive and Gram negative bacteria was encapsulated in microspheres made of poly(3-hydroxybutyric acid) P(3HB), a microbial biodegradable polymer isolated from Bacillus cereus SPV. The drug loaded microspheres were prepared using an oil emulsion technique and compressed uniaxially to produce films. Although the same fabrication conditions were used for preparing the drug loaded and unloaded microspheres, the presence of the drug changed the surface morphology and roughness of the films. The surface morphology of the drug loaded films appeared uneven and coarser and the roughness, with an average root mean square value of 5.89,µm, was significantly higher than that of the unloaded film. The in vitro biocompatibility of the films was investigated using a human keratinocyte cell line (HaCaT) by comparing cell viability on the films to that on conventional tissue culture plastics. Both films appear to support cell growth but cell attachment and percentage cell viability were greater on the drug loaded films (32% of control) compared to the unloaded film (10% of control), possibly as a result of the non-uniform surface morphology and increased roughness of the drug loaded film. Thus, the above results illustrate that the drug loaded films, in addition to being a suitable matrix for drug delivery, represent an improved substrate for keratinocyte cell attachment. [source] Enhanced Antibacterial Activity of Nanocrystalline ZnO Due to Increased ROS-Mediated Cell InjuryADVANCED FUNCTIONAL MATERIALS, Issue 6 2009Guy Applerot Abstract An innovative study aimed at understanding the influence of the particle size of ZnO (from the microscale down to the nanoscale) on its antibacterial effect is reported herein. The antibacterial activity of ZnO has been found to be due to a reaction of the ZnO surface with water. Electron-spin resonance measurements reveal that aqueous suspensions of small nanoparticles of ZnO produce increased levels of reactive oxygen species, namely hydroxyl radicals. Interestingly, a remarkable enhancement of the oxidative stress, beyond the level yielded by the ZnO itself, is detected following the antibacterial treatment. Likewise, an exposure of bacteria to the small ZnO nanoparticles results in an increased cellular internalization of the nanoparticles and bacterial cell damage. An examination of the antibacterial effect is performed on two bacterial species: Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive). The nanocrystalline particles of ZnO are synthesized using ultrasonic irradiation, and the particle sizes are controlled using different solvents during the sonication process. Taken as a whole, it is apparent that the unique properties (i.e., small size and corresponding large specific surface area) of small nanometer-scale ZnO particles impose several effects that govern its antibacterial action. These effects are size dependent and do not exist in the range of microscale particles. [source] Microwave-Assisted Synthesis of Nanocrystalline MgO and Its Use as a BacteriocideADVANCED FUNCTIONAL MATERIALS, Issue 10 2005S. Makhluf Abstract Nanocrystalline particles of MgO were synthesized using microwave radiation in an ethylene glycol solution. The antibacterial activities of the MgO nanoparticles were tested by treating Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive) cultures with 1,mg,mL,1 of the nanoparticles. We have examined the importance of the size effect, pH, and the form of the active MgO species as a bactericidal agent. A clear size dependence of the nanoparticles is observed where the amount of eradicated bacteria was strongly dependent on the particle size. [source] Preparation of antimicrobial sutures by preirradiation grafting onto polypropylene monofilamentPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 12 2008Bhuvanesh Gupta Abstract Antimicrobial sutures were prepared by the radiation grafting of acrylonitrile monomer onto polypropylene (PP) monofilament. The grafted sutures were subsequently hydrolyzed to transform nitrile groups into carboxylic groups for the immobilization of antimicrobial drug, tetracycline hydrochloride (TC). The modified sutures show continuous release of drug for a period of 4,5 days. The antimicrobial activity of the sutures was determined against both Gram positive and Gram negative bacteria by the zone of inhibition technique. Zone of inhibition was observed around the drug-containing sutures in the plate inoculated with Escherichia coli (E. coli), Klebsiella pneumonea (K. pneumonea), and Staphylococcus aureus (S. aureus). The results of infection studies in albino rats against S. aureus showed no infection even after fourth postoperative day of surgery. This is because of the release of the TC drug at the site of injury, which inhibits the bacterial growth. Copyright © 2008 John Wiley & Sons, Ltd. [source] Photodynamic therapy: a targeted therapy in periodonticsAUSTRALIAN DENTAL JOURNAL, Issue 2009M Raghavendra Abstract The oral cavity is colonized by a large number and highly diversified communities of micro-organisms. Bacterial biofilm present on tooth or root surface is a major cause of gingivitis and periodontitis. Chemical antimicrobial agents are widely used in prophylactic and therapeutic regimens for dental plaque related diseases, which are among the most common human infections. As these agents are difficult to maintain at therapeutic concentrations in the oral cavity and can be rendered ineffective by resistance development in target organisms, there is a need for an alternative antimicrobial approach. A novel approach, photodynamic therapy (PDT), could be a solution to these problems. Lethal photosensitization of many bacteria, both Gram positive and Gram negative was found in many studies. The advantage of this new approach includes rapid bacterial elimination, minimal chance of resistance development and safety of adjacent host tissue and normal microflora. Thus, the available knowledge of photodynamic therapy should encourage a more clinically oriented application of this technique. [source] Characterization of human peritoneal dendritic cell precursors and their involvement in peritonitisCLINICAL & EXPERIMENTAL IMMUNOLOGY, Issue 3 2005M. L. McCully Summary Scattered evidence suggests that the human peritoneal cavity contains cells of the dendritic cell (DC) lineage but their characterization is missing. Here, we report that the peritoneal cavity of normal subjects and of stable patients on peritoneal dialysis (PD) contains a population of CD14+ cells that can differentiate into DCs or macrophages. Within this pool, we characterized a CD14+CD4+ cell subset (2·2% of the peritoneal cells) fulfilling the definition of myeloid DC precursors or pre-DC1 cells. These cells expressed high levels of HLA-DR, CD13, CD33, and CD86, and low levels of CD40, CD80, CD83, CD123, CD209, TLR-2 and TLR-4. These cells retained CD14 expression until late stages of differentiation, despite concomitant up-regulation of DC-SIGN (CD209), CD1a, CD80 and CD40. Peritoneal pre-DC1 cells had endocytic capacity that was down-regulated upon LPS/IFN-, stimulation, were more potent allo-stimulators than peritoneal CD14+CD4,/lo cells and monocyte-derived macrophages, and induced Th1 cytokine responses. More importantly, the number of peritoneal pre-DC1 cells increased during PD-associated peritonitis, with a different profile for Gram positive and Gram negative peritonitis, suggesting that these cells participate in the induction of peritoneal adaptive immune responses, and may be responsible for the bias towards Th1 responses during peritonitis. [source] Carbon and nutrient limitation of soil microorganisms and microbial grazers in a tropical montane rain forestOIKOS, Issue 6 2010Valentyna Krashevska We investigated the role of carbon, nitrogen and phosphorus as limiting factors of microorganisms and microbial grazers (testate amoebae) in a montane tropical rain forest in southern Ecuador. Carbon (as glucose), nitrogen (as NH4NO3) and phosphorus (as NaH2PO4) were added separately and in combination bimonthly to experimental plots for 20 months. By adding glucose and nutrients we expected to increase the growth of microorganisms as the major food resource of testate amoebae. The response of microorganisms to experimental treatments was determined by analysing microbial biomass (SIR), fungal biomass and microbial community composition as measured by phospholipid fatty acids (PLFAs). We hypothesized that the response of testate amoebae is closely linked to that of microorganisms. Carbon addition strongly increased ergosterol concentration and, less pronounced, the amount of linoleic acid as fungal biomarker, suggesting that saprotrophic fungi are limited by carbon. Microbial biomass and ergosterol concentrations reached a maximum in the combined treatment with C, N and P indicating that both N and P also were in short supply. In contrast to saprotrophic fungi and microorganisms in total, testate amoebae suffered from the addition of C and reached maximum density by the addition of N. The results indicate that saprotrophic fungi in tropical montane rain forests are mainly limited by carbon whereas gram positive and negative bacteria benefit from increased availability of P. Testate amoebae suffered from increased dominance of saprotrophic fungi in glucose treatments but benefited from increased supply of N. The results show that testate amoebae of tropical montane rain forests are controlled by bottom,up forces relying on specific food resources rather than the amount of bacterial biomass with saprotrophic fungi functioning as major antagonists. Compared to temperate systems microbial food webs in tropical forests therefore may be much more complex than previously assumed with trophic links being rather specific and antagonistic interactions overriding trophic interactions. [source] | |||||||||||||