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1
Woo, Kei-sheng Gibson, and 吳基昇. "Molecular epidemiology of anaerobic gram-positive bacilli bacteremia and discovery of six novel anaerobic gram-positive bacilli." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B29762984.
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Gally, David Lawrence. "Cell wall assembly in gram positive bacteria." Thesis, University of Newcastle Upon Tyne, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287465.
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Valappil, Sabeel Padinhara. "Production of polyhydroxyalkanoates by gram positive bacteria." Thesis, University of Westminster, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.434414.
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Hayhurst, Emma. "Peptidoglycan structure and dynamics in gram positive bacteria." Thesis, University of Sheffield, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.434615.
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Wang, Lihui. "Sensing of gram positive bacteria in drosophila immunity." Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.670165.
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Johansson, Per. "Genetics of tetrapyrrole synthesis in gram-positive bacteria." Lund : Lund University, 1999. http://catalog.hathitrust.org/api/volumes/oclc/68944808.html.
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Wheeler, Richard. "Peptidoglycan architecture and dynamics in Gram-positive bacteria." Thesis, University of Sheffield, 2012. http://etheses.whiterose.ac.uk/2741/.
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The major structural determinant of most bacterial cells is the peptidoglycan layer, a network (the sacculus) of glycan strands cross-linked by short peptide stems which encompasses the entire bacterium. However the architecture of peptidoglycan, which must accommodate both the structural requirements of the cell and the dynamic processes of growth and division, is poorly understood. Most architectural studies have addressed the peptidoglycan of rod-shaped bacteria. The architecture in Gram-positive cocci and ovococci is largely uncharacterised, In this study, atomic force microscopy (AFM) of purified sacculi of three species of ovococcus was combined with biochemical analysis and super resolution fluorescence microscopy. A model was developed in which incorporation of long glycan strands from a single mid-cell focus results in preferential orientation, parallel to the short axis of the cell. AFM and fluorescence microscopy of the coccoid bacterium Staphylococcus aureus revealed a dynamic peptidoglycan architecture of rings and knobbles, growth by peptidoglycan maturation, and a system of heritable peptidoglycan ribs. Ribs may provide a structural mechanism for coordinating orthogonal division on three planes. We hypothesised cell wall growth occurs via the activity of N-acetyl-β-D-glucosaminidases. Four putative glucosaminidases were identified, with SagB found to have a major role in glycan strand length determination. Hydrolysis of the septal cross-wall by glucosaminidase activity was required for spherical shape, suggesting a novel mechanism of growth by hydrolysis. My work has highlighted diverse and elegant peptidoglycan architectures, adapted to meet the unique mechanical requirements of bacteria with different morphologies and strategies for growth and division.
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Hreggvidsson, Gudmundur Oli. "Cytochromes c and the evolution of Gram positive bacteria." Thesis, University of Edinburgh, 1993. http://hdl.handle.net/1842/14116.
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The content and cellular location of cytochromes in Bacillus azotoformans was examined under aerobic and denitrifying anaerobic conditions. An abundance of cytochromes was expressed. Two cytochromes were induced under aerobic conditions, one of which was only expressed under conditions of high aeration. One cytochrome, a b-type cytochrome, may be induced under denitrifying conditions. Cytochromes common to both pathways appear to be expressed in similar amounts per unit cell weight. Both c- and b-type cytochromes from B. azotoformans appear to be membrane bound, as they were only detected in membrane fractions. Different methods for releasing cytochromes from cell membranes were tried. Only extraction with detergents and mild proteolytic treatment were successful. Four different membrane bound cytochromes from Bacillus azotoformans, designated P1-c552, P2-c551, P3&P4-c555 and P5-c552, were isolated and purified. The bases of classification of Class I cytochromes c are examined and revisions are suggested to the existing classification schemes. The evolutionary implications of the distribution of the proposed cytochrome c groups in the phylogenetic eubacterial tree, based on 16sRNA analyses, are discussed. The past and present ideas about the evolution of the phylum of Gram positive bacteria are presented and discussed in the light of the present sequence information of cytochromes c and other electron transport proteins. The electron transport pathway in the genus Bacillus is compared with its counterparts in distantly related bacteria. The significance of observed similarities and differences, in types of cytochromes and composition, for the elucidation of the evolutionary history of the Gram positive phylum as well as for eubacteria in general, is emphasised.
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Lee, Wan-Jing. "Isolation and characterisation of phages infecting gram positive food bacteria." Thesis, University of Canterbury. School of Biological Sciences, 2008. http://hdl.handle.net/10092/3429.
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Bacteriophage (phage), virus of bacteria, has been proposed as a mean to inactivate bacteria that are pathogens of humans. Applied prophylatically to food, phage might decrease the numbers of potential pathogens we ingest. Much active research on using the phages of bacteria to control Gram negative foodborne pathogens are described in the literatures, but comparatively little research describes the phages of Gram positive bacteria and their use as biocontrol agents on food. In this work, previous undescribed phages, able to infect Bacillus cereus and Listeria monocytogenes, were isolated from soil and ruminants faecal material, respectively. As the first step in assessing their potential as biocontrol agents, the isolated phages were purified, concentrated and characterised (albeit to different degrees). The Bacillus phages had a narrow host range while the Listeria phages had a broad host range. Listeria phages also infected L. monocytogenes 2000/47, a strain which recurs in New Zealand clinical cases. Both Bacillus and Listeria phages appeared to be of the Myoviridae family judging by their structure in electron micrographs. The Bacillus FWLBc1 and FWLBc2 phages were lytic phages with a latent period of 106 and 102 min at 37°C, and an average burst size of 322 and 300 phages per infected cell, respectively. Moreover, they both had genomes of approximately 134 kb. All newly isolated and characterized phages were chloroform resistant and survived storage better at 4°C than at room or freezing temperatures. Bacillus phages significantly reduced the bacterial population in mashed potatoes within 24 h at room temperature, when applied at a phage to host ratio of 1000. Listeria phages rapidly inactivated the host population to a low optical density. The findings of this thesis will add to the current knowledge of phages in the context of various environmental conditions for different bacteria and will demonstrate the potential of phages as food safety biocontrol agents.
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Qazi, Saara N. A. "Development of reporter genes for use in Gram positive bacteria." Thesis, University of Nottingham, 1999. http://eprints.nottingham.ac.uk/13028/.
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Green fluorescent protein (gfp) and bacterial luminescence (lux) reporter genes have been used to construct a variety of reporter plasmids for Gram positive bacteria with the aim of using these for bacterial localisation and gene expression studies. The native gfp and luxCDABE genes were cloned into a shuttle vector and the resulting plasmids used to transform Listeria monocytogenes. However, the bacterial populations were found to be weakly fluorescent or luminescent compared to E. coli harbouring the same plasmids. When L. monocytogenes expressing gfp were examined by fluorescence microscopy, only a small proportion of the population was seen to fluoresce. This phenomenon was observed regardless of the gfp variant used in the cloning procedure. However, when gfp3 was placed downstream of PxylA, slightly more individual fluorescent cells were observed compared to when gfp3 was expressed from Pxyn, but the majority of the population was still non-fluorescent. Northern blot analysis and subsequent analysis by SDS PAGE and immunoblotting lead to the supposition that translation of gfp was limiting in L. monocytogenes. A variety of factors could potentially lead to poor translation of the protein, for example poor codon usage, the presence of a ribosome stall site, or poor initiation of translation by the ribosomes. These were all investigated in tum to determine why translation of gfp3 was limiting. Modification of the translational initiation region of gfp3, resulted in a homogeneously fluorescent L. monocytogenes population when the modified gene was expressed from PxylA. Individual lux genes, luxA, luxC and luxE were also translationally enhanced in a similar way to gfp3, and reorganised into an operon where the luciferase genes were adjacent to, but separate from the aldehyde genes. This engineered luxABCDE operon was also expressed from PxylA and highly luminescent populations of L. monocytogenes and Staphylococcus aureus obtained. Having optimised translation for expression III Gram positive bacteria, these reporters were used to construct a variety of reporter plasmids that were successfully employed to observe the intracellular invasion and to monitor agr expression in S. aureus.
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Gontang, Erin Ann. "Phylogenetic diversity of gram-positive bacteria and their secondary metabolite genes." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2008. http://wwwlib.umi.com/cr/ucsd/fullcit?p3324374.
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Thesis (Ph. D.)--University of California, San Diego, 2008.Title from first page of PDF file (viewed October 3, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
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Meyer, Hanna [Verfasser]. "Applying metabolomics to Gram-positive bacteria: Investigations on pathogenic and biotechnological relevant bacteria / Hanna Meyer." Greifswald : Universitätsbibliothek Greifswald, 2014. http://d-nb.info/1051066409/34.
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Leung, Po-shan. "In silico analysis of 16S ribosomal RNA gene sequencing based methods for identification of medically important Gram-positive cocci /." View the Table of Contents & Abstract, 2007. http://sunzi.lib.hku.hk/hkuto/record/B38348159.
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Leung, Po-shan, and 梁寶珊. "In silico analysis of 16S ribosomal RNA gene sequencing based methods for identification of medically important Gram-positive cocci." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B45011382.
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Skovbjerg, Susann. "Inflammatory mediator response to Gram-positive and Gram-negative bacteria in vitro and in middle ear infections." Göteborg : Clinical Bacteriology Section, Dep. of Infectious Medicine, Sahlgrenska Academy , University of Gothenburg, 2010. http://hdl.handle.net/2077/21533.
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Haston, Rowenna Mitch. "Investigation into the mechanism of the innate recognition of gram-positive bacteria." Thesis, University of Sussex, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436389.
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Sutcliffe, Iain C. "The lipids and lipoglycan of Propionibacterium freudenreichii and other gram-positive bacteria." Thesis, University of Newcastle Upon Tyne, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328137.
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Mashraqi, Mutaib Mosaued. "The role of haptoglobin in the immune response to Gram-positive bacteria." Thesis, University of Leicester, 2017. http://hdl.handle.net/2381/40669.
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Haptoglobin (HP) is a positive acute-phase serum protein. It is upregulated during infection and is a valuable marker for many inflammatory-related diseases. In serum it is present as a disulphide-linked homodimer, with each subunit being composed of two domains, a complement control protein domain (CCP-domain) and a serine-protease-like domain. During biosynthesis the polypeptides are cleaved into α- (the CCP-domain) and β-chains (the SP domain) and both remain linked together by a disulphide bond. A crucial function of HP is to act as a scavenger of free haemoglobin from plasma, since high quantities of free haemoglobin can be deleterious for the host. More recent work indicates that HP also interacts with lipoteichoic acid (LTA) of Gram-positive bacteria, an important virulence factor, and this is the focus of my thesis. The results of this work demonstrate that HP binds to LTA directly as well as to LTA on a wide range of Gram-positive bacteria (including LTA from S. aureus and S. pneumoniae). The IC50 of the interaction is ~40 nM in competition experiments to immobilised S. aureus. My work has shown that the LTA interaction site of HP is located on the β-chain and that LTA competes for binding with haemoglobin indicating that the binding sites for LTA and haemoglobin overlap. Surprisingly, in vivo studies showed that C57BL/6J HP-/- mice show a significant degree of protection from experimental S. pneumoniae infection. Over the course of the experiments, approximately 90% of HP-/- mice were resistance to the pneumococcal infection compared to 40% in strain, age and sex matched control wild-type mice infected in parallel. In line with the infection study, wild-type mice showed significantly higher levels of bacteraemia than HP-/- mice and the bacterial load in the lung, liver, kidney was significantly higher. These findings demonstrate that HP interacts with bacteria and plays an important role during infection. Surprisingly, the presence of HP appears to give S. pneumoniae a so far unknown advantage during infection.
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Organji, Sameer R. A. "Detection of #Beta#-lactam resistant Streptococcus pneumoniae by polymerase chain reaction." Thesis, University of Bristol, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297824.
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Chung, Whasun Oh. "Macrolide resistance and its linkage to tetracycline resistance /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/9279.
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Pöther, Dierk-Christoph [Verfasser]. "Proceedings in the thiolome of low GC, Gram-positive bacteria / Dierk-Christoph Pöther." Greifswald : Universitätsbibliothek Greifswald, 2012. http://d-nb.info/1027381804/34.
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Pinchuk, Tommy. "Optimization of pre-processing variables for hyperspectral analysis of focal plane array Fourier transform infrared images." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=98769.
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A genetic algorithm was employed to select the optimal combination of preprocessing variables, including data pretreatment, data manipulation and feature extraction procedures, for eventual clustering of a data set consisting of hyperspectral images acquired by a focal plane array Fourier transform infrared (FPA-FTIR) spectrometer. The data set consisted of infrared images of bacterial films, and the classification task investigated was the discrimination between Gram-positive and Gram-negative bacteria. The genetic algorithm evaluated combinations of variables pertaining to bacterial film thickness tolerances, baseline correction, pixel co-addition, outlier removal, smoothing, mean centering, normalization, derivatization, integration and principal component selection. Following numerous iterations of unsupervised processing, the genetic algorithm arrived at a sub-optimal solution yielding a clustering accuracy of 97.8% and a data utilization of 28.6%. The results provided insight into the co-dependencies of the pre-processing variables and their consequential effect on the selected data. The robustness of the classification model was evaluated and reinforced by the successful classification of two distinct validation sets. The overall success of the genetic algorithm suggests that it is an effective time saving resource for the optimization of pre-processing variables that does not require operator intervention.
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He, Jing. "Studies towards the total synthesis of tetrodecamycin." Thesis, University of Oxford, 2007. http://ora.ox.ac.uk/objects/uuid:3a2ab5cb-2757-4e53-b8cf-c635aef99455.
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Tetrodecamycin (1) is a novel α-(γ-hydroxyacyl) tetronic acid based polyketide antibiotic isolated from the culture broth of Streptomyces nashvillensis MJ885-mF8 by Takeuchi et al. in 1994. Compound 1 shows potent inhibitory activity against Gram-positive bacteria including Bacillus anthracis and methicillin resistant Staphylococcus aureus (MRSA). It was proposed that an Aldol reaction of trans-decalin core 2 and tetronic acid derivative 3 followed by a face selective epoxidation and a subsequent epoxide-opening reaction would deliver the 6,6,7,5-skeleton of tetrodecamycm (1). To investigate this proposal, the silyl enol ether 5 was prepared from cycloheptene 4 in 7 steps. An unusual domino silyl enol ether reaction sequence was observed when the silyl enol ether 5 was submitted to a Diels-Alder reaction. It afforded cycloadduct 6, which was converted to the key intermediate 2 after another 3 steps (Scheme 1). Concurrently, double functionalisation of simple cyclic silyl enol ethers was investigated. Because of some difficulties in reproducing good overall yields to the cycloadduct 6, a second synthetic route was proposed. It was envisaged that a palladium-catalysed oxidative cyclisation or an organoselenium-mediated cyclisation reaction of compound 8 would construct the 6,6,7,5- skeleton 7, which would be converted to tetrodecamycin (1) via dihydroxylation followed by an introduction of the exo-methylene group. The intramolecular Diels-Alder reaction of trienal 11 afforded trans-decalin 10, which was converted to β-keto ester 9 in 2 steps. A Dieckmann-type cyclisation of 9 afforded compound 8 in good yield. However, so far transformation to compound 7 has not been achieved (Scheme 2).
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胡國良 and Kwok-leung Wu. "In silico analysis of 16S ribosomal RNA gene sequencing based methods for identification of medically important Gram-positive rods." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B40721802.
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Oladele, Agunbiade M. "Studies on bioflocculants produced by three freshwater Actinomycetes (Streptomyces Sp.Gansen, Cellulomonas Sp,Bola and Brachybacterium Sp, UFH) isolated from Tyume river." Thesis, University of Fort Hare, 2011. http://hdl.handle.net/10353/6550.
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Several bacteria were isolated from the bottom sediments of Tyume River and investigated for bioflocculant production potentials. Kaolin clay suspension (4 g/l) was used to measure the flocculating activity and three of the positive isolates were identified by 16S rRNA gene nucleotide sequence analyses and the sequences deposited in GenBank as Streptomyces sp Gansen (accession number HQ537129), Brachybacterium sp UFH (accession number HQ537131.), and Cellulomonas sp Bola (accession number HQ537132). Streptomyces sp Gansen exhibited its maximum flocculating activity using lactose (85% activity), peptone (76.3% activity), Ca2+ as sole sources of carbon, nitrogen and cations respectively, and at a neutral pH of 7.0, while, the bioflocculant produced by Brachybacterium sp UFH with glucose, urea and Ca2+ as carbon, nitrogen and cations sources yielded 82% and 97% flocculation activity respectively at a neutral pH. Also, glucose (73.2% activity), ammonium chloride (78.2% activity) and Ca2+ resulted in optimal production of bioflocculant by Cellulomonas sp Bola, also at a neutral pH. Chemical analysis confirmed that bioflocculant produced by Streptomyces Gansen is a polysaccharide while Brachybacterium sp UFH and Cellulomonas sp Bola produces a glycoprotein compound. This freshwater actinomycetes appears to have a tremendous potential as sou rces of new bioflocculants.
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Wu, Kwok-leung. "In silico analysis of 16S ribosomal RNA gene sequencing based methods for identification of medically important Gram-positive rods." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B40721802.
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Michalik, Stephan [Verfasser]. "Proteolysis at a proteome-wide scale in low GC, Gram-positive bacteria / Stephan Michalik." Greifswald : Universitätsbibliothek Greifswald, 2012. http://d-nb.info/1021185868/34.
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Elsholz, Alexander [Verfasser]. "Regulation of protein quality control systems in low GC, Gram-positive bacteria / Alexander Elsholz." Greifswald : Universitätsbibliothek Greifswald, 2011. http://d-nb.info/1012034402/34.
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MacDonald, Kelly Lynn. "Bactericidal effect of Pseudomonas aeruginosa PAO1 gentamicin-induced membrane vesicles on gram-positive bacteria." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ61923.pdf.
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Sharkey, Liam Karl Robert. "Functional insights into ABC-F proteins that mediate antibiotic resistance in Gram-positive bacteria." Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/12924/.
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Members of the ABC-F subfamily of ATP-binding cassette (ABC) proteins mediate resistance to a broad array of clinically-important antibiotic classes that target the ribosome of Gram-positive pathogens. The mechanism by which the ABC-F proteins mediate antibiotic resistance is poorly defined, although two hypotheses have been proposed; drug efflux and ribosomal protection. Here, this mechanism of resistance was investigated using a combination of bacteriological and biochemical techniques. Results obtained from the bacteriological assays provided preliminary data in support of ribosomal protection. Subsequently, the heterologous expression and purification of two ABC-F proteins, Vga(A) and Lsa(A), allowed the function of these proteins to be assessed in staphylococcal transcription-translation (T/T) reactions. Addition of Vga(A) and Lsa(A) to T/T assays subject to antibiotic inhibition caused drug specific, dose-dependent, rescue of translation. Several previously described resistance phenotypes attributed to these proteins were successfully recapitulated in T/T assays, corroborating the idea that rescue of translation observed in vitro is representative of the action of these proteins in whole cells. Finally, ribosome binding assays showed Lsa(A) to be capable of displacing antibiotics from staphylococcal ribosomes. Collectively, the experiments described in this thesis provide the first direct evidence to support a mechanism of ARE ABC-F resistance based on ribosomal protection.
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Winzar, Renee. "Synthesis of Modified Analogues of 3-deoxy-D-manno-octulosonic Acid (KDO) as Probes to Investigate the Donor Substrate Specificity of KDO Transferase." Thesis, Griffith University, 2012. http://hdl.handle.net/10072/367860.
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There have always been reported cases of bacteria able to resist antibiotic treatment. Through recent history, infections with bacteria capable of resisting at least one type of drug treatment have become more commonplace [1,2,3]. The dearth of novel-acting antibiotics, combined with the resourcefulness of pathogenic bacteria under selective pressure means that humans are now faced with strains of bacteria that have developed resistance to multiple drugs. Of the few novel acting antibiotics developed in the last 30 years, most are targeted only to Gram positive bacteria, and reports of bacteria demonstrating resistance to these drugs have already surfaced [4,5,6]. The vast difference in the number of drugs available for treatment of Gram positive versus Gram negative bacterial infections is a direct reflection of the difficulty in targeting Gram negative bacteria with drugs. Drugs which treat Gram positive infections are often superfluous against Gram negative bacteria in large part due to the extra outer cell membrane these bacteria possess, which acts as an additional physical barrier and contains drug efflux pumps, ABC transporters and selective porins [7]. The structural integrity of the outer memberane structure has been shown to be essential to the viabililty of pathogenic Gram negative bacteria, which makes it an attractive target for the development of novel acting antibiotics [8].Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Institute for Glycomics
Science, Environment, Engineering and Technology
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Ng, Ho-yin Ricky, and 吳浩然. "Identification of anaerobic, non-sporulating, Gram-positive bacilli from blood cultures by 16S rRNA gene sequencing." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B44670424.
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Winter, Theresa [Verfasser]. "A physiological proteomic approach to address infection-related issues of Gram-positive bacteria / Theresa Winter." Greifswald : Universitätsbibliothek Greifswald, 2012. http://d-nb.info/102157435X/34.
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Nascimento, Maristela da Silva do 1977. "Caracterização da atividade antimicrobiana e tecnologica de tres culturas bacteriocinogenicas e avaliação de sua eficiencia no controle de Listeria monocytogenes, Staphylococcus aureus e Bacillus cereus em queijo Minas frescal." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/255710.
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Orientadores: Arnaldo Yoshiteru Kuaye, Izildinha MorenoTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: A biopreservação é uma técnica utilizada para estender a vida útil e aumentar a segurança dos alimentos por meio do emprego de microbiota protetora e/ou seus peptídeos antimicrobianos. O objetivo deste trabalho foi avaliar a atividade antimicrobiana de culturas produtoras de bacteriocinas sobre alguns patógenos Gram-positivos de ocorrência comum em produtos lácteos. As culturas bacteriocinogênicas Lactococcus lactis subsp. Lactis ATCC 11454, Lactobacillus plantarum ALC 01 e Enterococcus faecium FAIR-E 198 apresentaram comportamento distinto em relação à produção de bacteriocinas quando inoculadas em caldo MRS e em leite desnatado reconstituído (LDR) a 10%. Na avaliação do espectro de ação antimicrobiano pelo método de difusão em ágar por inoculação em poços, as bacteriocinas produzidas por Lb. plantarum ALC 01 e E. faecium FAIR-E 198 apresentaram atividade inibitória apenas sobre as linhagens de Listeria monocytogenes, já a nisina produzida por Lc. lactis subsp. lactis ATCC 11454 demonstrou espectro de ação mais amplo, porém com menor atividade que as demais culturas bacteriocinogênicas. Na avaliação da compatibilidade de desenvolvimento associativo com fermentos lácticos comerciais, somente Lc. lactis subsp. lactis ATCC 11454 apresentou atividade (halo de 6mm) sobre as linhagens constituintes de ambos os fermentos lácticos avaliados. A determinação da atividade acidificante foi realizada em LDR 10% após 8 e 24h de incubação a 35ºC; a adição de 0,1% e de 0,5% das culturas bacteriocinogênicas não afetou significativamente a capacidade de acidificação dos fermentos lácticos. Além disso, observou-se que o desenvolvimento associativo dos fermentos lácticos com Lb. Plantarum ALC 01 e E. faecium FAIR-E 198, em ambas as concentrações, proporcionou significativo aumento da atividade das bacteriocinas destas culturas, enquanto que a atividade da nisina de Lc. lactis subsp. lactis ATCC 11454 foi suprimida. A atividade de aminopeptidases foi determinada após desenvolvimento das culturas lácticas em caldo MRS, Lb. Plantarum ALC 01 apresentou as maiores atividades. Também foi analisado o comportamento de patógenos Gram-positivos durante desenvolvimento associativo com as culturas produtoras de bacteriocinas e fermento láctico em LDR 10% a 35ºC por 48h. Lb. plantarum ALC 01 e E. faecium FAIR-E 198 não influenciaram significativamente o desenvolvimento de Bacillus cereus K1-B041 e de Staphylococcus aureus ATCC 27154 durante as primeiras 24h de incubação a 35ºC, contudo apresentaram forte ação inibitória sobre L monocytogenes Scott A. Já Lc. lactis subsp. lactis ATCC 11454 afetou o desenvolvimento de todos os patógenos apenas durante as primeiras 12h de incubação. O fermento láctico demonstrou significativa ação inibitória sobre B. cereus K1-B041 (>7,37 log UFC/ml) e L monocytogenes Scott A (>6,26 log UFC/ml). Em queijo Minas Frescal, não foi observada diferença significativa entre a ação das culturas bacteriocinogênicas e o fermento láctico sobre L. monocytogenes Scott A e S. aureus ATCC 27154. B. cereus K1-B041 demonstrou susceptibilidade a Lb. plantarum ALC 01 e E. faecium FAIR-E 198 após 7 dias. Pelo método de diluição crítica não foi detectada atividade de bacteriocina nos queijos durante os 21 dias de estocagem a 8 ± 1ºC. A adição das culturas produtoras de bacteriocinas como adjuntas ao queijo Minas Frescal não promoveu alteração no pH e na acidez, contudo Lb. plantarum ALC 01 e E. faecium FAIR-E 198 promoveram aumento da proteólise primária e secundária. Embora os resultados obtidos demonstrem que as culturas bacteriocinogênicas avaliadas não possam ser empregadas como único método de conservação, estas podem atuar em sinergia com outros fatores para aumentar a eficiência no controle de patógenos Gram-positivos, especialmente L. monocytogenes, em produtos lácteos fermentados
Abstract: The biopreservation system, such as bacteriocinogenic lactic bacteria cultures and/or their bacteriocins, have received increasing attention and new approaches to control pathogenic and spoilage microorganisms have been developed. The purpose of this study was to evaluate the action of bacteriocin-producing cultures (Lactococcus lactis subsp. lactis ATCC 11454, Lactobacillus plantarum ALC 01 and Enterococcus faecium FAIR-E 198) on some Gram-positive pathogens in different culture media and dairy products. The bacteriocin production was influenced by the media. The antimicrobial activity of these cultures was evaluated by agar-well diffusion assay. The bacteriocins produced by Lb. plantarum ALC 01 and E. faecium FAIR-E 198 presented inhibitory activity on Listeria monocytogenes alone, on the other hand, the nisin produced by Lc. lactis subsp. Lactis ATCC 11454 demonstrated wide action spectrum, albeit with lower activity. In compatibility of associative development evaluation with the commercial starter culture, only Lc. lactis subsp. lactis ATCC 11454 presented activity on the starter culture. The acidifier activity determination was carried out in skimmed milk after 8h and 24h of incubation at 35ºC. The addition of 0.1% and 0.5% of the bacteriocinogenic cultures did not affect the production of lactic acid by the starter culture. The associative development of the starter culture with Lb. plantarum ALC 01 and E. faecium FAIR-E 198 provided significant increase in bacteriocin activity of these cultures, while the activity of Lc. Lactis subsp. lactis ATCC 11454 nisin was suppressed. The aminopeptidase activity was determined after cellular lise of the lactic cultures previously grown in MRS broth. Lb plantarum ALC 01 presented the largest activity. Moreover, the behavior of Gram-positive pathogens was analyzed during co-culture with the bacteriocin-producing bacteria and with the starter culture in skimmed milk. Lb. plantarum ALC 01 and E. faecium FAIR-E 198 did not influence the development of Bacillus cereus K1-B041 and of Staphylococcus aureus ATCC 27154 during the first 24h of incubation at 35ºC. They presented strong inhibition on L. monocytogenes Scott A. Lc. lactis subsp. lactis ATCC 11454 affected the development of the pathogens studied during the first 12h of incubation. The starter culture demonstrated good inhibition of B. cereus K1-B041 (>7.37 log UFC/ml) and L monocytogenes Scott A (>6.26 log UFC/ml). In Minas Frescal cheese, significant difference was not observed between the action of the bacteriocinogenic cultures and the starter culture on L. monocytogenes Scott A and S. aureus ATCC 27154. B. cereus K1- B041 demonstrated susceptibility to Lb. plantarum ALC 01 and E. faecium FAIR-E 198 after 7 days. Bacteriocin activity was not detected in the cheeses during 21 days at 8 ± 1ºC. The addition of the bacteriocin-producing bacteria as an adjunct culture to the Minas Frescal cheese did not promote alteration in the pH and in the acidity, however Lb. plantarum ALC 01 and E. faecium FAIR-E 198 promoted an increase of the cheese proteolysis. Although the obtained results demonstrated that bacteriocinogenic cultures cannot be used as only method of conservation, these can be used as an additional barrier to optimize the control of Gram-positive pathogens, especially L. monocytogenes, in dairy products
Doutorado
Doutor em Tecnologia de Alimentos
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Belcher, Pamela Elizabeth. "Role of toll-like receptors in immune and cardiovascular responses to pattern associated molecular patterns of gram-positive and gram-negative bacteria." Thesis, Imperial College London, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.479166.
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Welgamage, Don Aakash Channa Dharshan. "An investigation into the biodegradation of peptide cyanotoxins (microcystins and nodularin) by novel gram-positive bacteria." Thesis, Robert Gordon University, 2012. http://hdl.handle.net/10059/738.
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Cyanobacterial secondary metabolites, microcystins (MC) and nodularin (NOD) have become common contaminants in most aquatic ecosystems over recent years presenting a hazard to animal and human health. Unfortunately, these chemically diverse peptide hepatotoxins remain a challenge to most conventional water treatments due to their stable cyclic structures. Over recent years, bioremediation of MC and NOD has become one of the most exciting areas that holds promise for a successful and cost effective solution for water treatment process. The current work presents the biodegradation of MCs and NOD by bacterial isolates from three different bacteria genus Arthrobacter, Brevibacterium and Rhodococcus belonging to Actinobacteria. A total of five isolates representing the three genera have demonstrated an overall metabolism of MC-LR, -LF, -LY, -LW, -RR and NOD in a Biolog MT2 assay. Subsequently, these bacteria were reported to degrade the range of toxins in a separate batch experiment. The bacterial degradation rate of the above cyanobacterial peptides were found to decrease with the multiple subculturing of the bacteria. However, a rapid degradation was discovered when the bacteria were re-exposed to MC or other prokaryotic peptides demonstrating an inducible bacterial biodegradation. Utilising latest molecular biology techniques, the gene responsible for production of MC degrading enzymes was successfully elucidated and its activity was evaluated. Analysis of the degradation products of MC-LR revealed a glutathione conjugate detoxification mechanism involved during the degradation of MC-LR by Rhodococcus sp. (C1). A novel MC degradation pathway was proposed. Further studies were suggested to fully characterise the degradation pathway and to evaluate the MC detoxification mechanism in bacteria.
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Van, der Merwe Jacobus Arnoldus. "The identification and characterisation of the arsenic resistance genes of the gram-positive bacterium, Sulfobacillus thermosulfidooxidans VKM B-1269T." Thesis, Stellenbosch : Stellenbosch University, 2007. http://hdl.handle.net/10019.1/19886.
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Thesis (MSc)--University of Stellenbosch, 2007.ENGLISH ABSTRACT: The arsenic resistance operon (ars operon) of the Gram-positive, iron-oxidizing, acidophilic, moderately thermophilic bacterium, Sulfobacillus thermosulfidooxidans VKM B-1269T (Sb. t. VKM B-1269T), was isolated and characterised. The ars operon was chromosomally located and consisted of an arsR (codes for a transcriptional regulator) and an arsB (codes for a membrane located arsenic/antimony efflux pump). The arsRB genes were transcribed in the same direction. An arsC (codes for an arsenate reductase), usually associated with ars operons, was absent from this ars operon. PCR and Southern-hybridization experiments revealed that no arsC, representative of either the Grx/GSH or Trx ArsC families was present in the genome of Sb. t. VKM B-1269T. An interesting feature of the ars operon was the presence of a gene encoding a 525 amino acid (60.83 kDa) kumamolisin-As precursor located upstream of the arsRB operon. The intergenic region between the termination end of the kumamolisin-As precursor gene and the transcriptional start of the arsR gene was only 77 bp, suggesting that this ars operon might consist of three genes. RT-PCR analysis showed that the ars operon of Sb. t. VKM B-1269T, was not co-transcribed with the kumamolisin-As precursor gene in its native Sulfobacillus host. The ars operon of Sb. t. VKM B-1269T did not complement an Escherichia coli arsenic sensitive mutant. mRNA transcript analysis and promoter expression studies confirmed that processes involved in the production of functional proteins from the ars operon transcript were likely to be responsible for the inability of the arsRB operon of Sb. t. VKM B-1269T to confer resistance to arsenic in the heterologous E. coli host. Eight Sulfobacillus strains isolated from different geographical areas were subjected to amplified ribosomal DNA restriction enzyme analysis (ARDREA) using the restriction endonuclease Eco1015 (SnaBI) and revealed that they could be divided into the proposed Sulfobacillus spp. subgroup I and subgroup II, respectively (Johnson et al., 2005). The presence, distribution and relatedness of the ars genes among members of genus Sulfobacillus was determined. Phylogenetic sequence comparisons revealed two clearly defined arsB clusters within genus Sulfobacillus and showed that the arsB of a specific Sulfobacillus sub specie is distinctive of that specific Sulfobacillus sub specie. Futhermore, sequence analysis of the isolated arsB homologue fragments from the respective Sulfobacillus spp. showed that four distinctive profiles could be identified based on differences in the location of restriction endonuclease recognition sites.
AFRIKAANSE OPSOMMING: Die arseen weerstandbiedendheidsoperon (ars operon) van die Gram-positiewe, ysteroksiderende, asidofiliese, matige termofiliese bakterium, Sulfobacillus thermosulfidooxidans VKM B-1269T (Sb. t. VKM B-1269T), was geïsoleer en gekarakteriseer. Die ars operon was op die chromosoom geleë en het uit ‘n arsR (kodeer vir ‘n transkripsionele reguleerder) en ‘n arsB (kodeer vir ‘n membraan geleë arseen/timien uitskeidings pomp) bestaan. Die arsRB gene word in dieselfde rigting getranskribeer. ‘n arsC (kodeer vir ‘n arsenaat reductase), wat gewoontlik geassosïeer word met ars operons, was afwesig van hierdie ars operon. PKR en Southern-hibridisasie eksperimente het aangedui dat geen arsC, verteenwoordigend van beide die Grx/GSH of Trx ArsC families, nie teenwoordig was in die genoom van Sb. t. VKM B-1269T, nie. ‘n Interressante eienskap van hierdie ars operon was die teenwoordigheid van ‘n geen wat stroom-op van die arsRB operon geleë is en ‘n 525 amino suur (60.83 kDa) kumamolisin-As voorloper kodeer. Die intergeniese gedeelte tussen die terminerings einde van die kumamolisin-As voorloper en die transkriptionele begin van die arsR geen was slegs 77 bp, wat voorgestel het dat die ars operon moontlik uit drie gene bestaan. RT-PKR analiese het bewys dat die ars operon van Sb. t. VKM B-1269T, nie geko-getranskribeer word met die kumamolisin-As voorloper in sy oorspronklike Sulfobacillus gasheer nie. Die ars operon van Sb. t. VKM B-1269T, het nie ‘n Escherichia coli arseen sensitiewe mutant gekomplimenteer nie. mRNA transkrip-analiese en promoter uitdrukkings eksperimente het bevestig dat prosesse wat betrokke is in die produksie van funksionele proteïene vanaf die ars operon transkrip, moontlik vir die onvermoë van die arsRB operon van Sb t. VKM B-1269T verantwoordelik was om weerstandbiedendheid teen arseen in die heteroloë E. coli gasheer te verleen. Agt Sulfobacillus stamme wat geïsoleer is vanuit verskillende geografiese areas, was onderhewig aan geamplifiseerde ribosomale DNA restriksie-ensiem-analiese (ARDREA) deur gebruik te maak van restriksie endonuklease Eco1015 (SnaBI) en het aangedui dat hulle in die voorgestelde Sulfobacillus spp. subgroup I en subgroup II ingedeel kan word (Johnson et al., 2005). Die aanwesigheid, verspreiding en verwantskappe van die ars gene tussen lede van genus Sulfobacillus was bepaal. Filogenetiese DNA volgorde vergelykings het aangedui dat twee duidelik definïeerbare arsB groepe van mekaar onderskei kan word en dat die arsB van ‘n spesifieke Sulfobacillus sub spesie uniek tot daardie spesifieke Sulfobacillus subspesie is. Bykomend, DNA volgorde analiese van die geïsoleerde arsB homoloog fragmente van die Sulfobacillus spp. het gewys dat vier unieke profiele, op grond van verskille in die ligging van restriksie ensiem herkenning setels, geïdentifiseer kan word.
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Hektor, Harm Jan. "Physiology and biochemistry of primary alcohol oxidation in the gram-positive bacteria "amycolatopsis methanolica" and "bacillus methanolicus"." [S.l. : [Groningen] : s.n.] ; [University Library Groningen] [Host], 1997. http://irs.ub.rug.nl/ppn/158492587.
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Pascual, Ramos Christina. "Molecular taxonomic studies on some high G+C content gram-positive bacteria from human and animal sources." Thesis, University of Reading, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312538.
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Watanabe, Isao. "Dependence of the lethal effect of pore-forming haemolysins of gram-positive bacteria on the cytolytic activity." Kyoto University, 2006. http://hdl.handle.net/2433/143878.
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Witzel, Claudia de Lima [UNESP]. "Isolamento e caracterização de amostras comunitárias Staphylococcus aureus resistente à Meticilina (CA-MRSA) em uma população carcerária no município de Avaré." Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/89939.
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Universidade Estadual Paulista (UNESP)
As Infecções estafilocócicas são grande causa de mortalidade e morbidade. A emergência de isolados de Staphylococcus aureus resistente à meticilina (MRSA) originários da comunidade na década de 1990 trouxe desafios para sua prevenção e abordagem terapêutica. A identificação da prevalência e características de MRSA adquirido em comunidade (CA-MRSA) em populações de alto risco pode fornecer valiosas informações para compreensão de sua epidemiologia. O objetivo deste estudo foi identificar a prevalência, os fatores de risco e as características moleculares de CA-MRSA isolado em nasofaringe de uma população carcerária em Avaré, Brasil. Foram coletados swabs nasais de 302 homens encarcerados no Centro de Ressocialização de Avaré. A caracterização da resistência à meticilina foi feita através de difusão em disco (Oxacilina e Cefoxitina) e identificação do gene mecA (por Reação em Cadeia de Polimerase (PCR). Utilizou-se também PCR para identificação dos genes lukF-PVe lukS-PV que codificam a leucocidina de Panton-Valentine. Fatores de risco para colonização nasal por S. aureus e por MRSA foram avaliados em modelos univariados e multivariados (regressão logística). A prevalência de colonização nasal por S. aureus como um todo foi de 16,5%, e a MRSA (definida como positividade para o gene mecA), de (02) 4,0%. Os testes de difusão com disco de Oxacilina e Cefoxitina identificaram 2 (4%) resistentes simultaneamente a Oxacilina e Cefoxitina. Nenhum dos isolados de S. aureus apresentou genes codificadores da PVL. As amostras positivas para gene mecA apresentaram SCCmec tipo IV, confirmando esta tipagem presente em amostras comunitárias.Uma das amostras positivas para gene mecA apresentou SCCmec IV-d, que pelo método PFGE agrupou em 85,7% com o clone JCSC 4469 de origem japonesa. Os fatores de risco para...
Staphylococci infections are a major cause of morbidity and mortality. The emergence of methicillin-resistant Staphylococcus aureus (MRSA) isolates original from the community in the 1990s brought challenges for prevention and therapeutic approach.Identifying the prevalence and characteristics of community-acquired MRSA (CA-MRSA) in high-risk populations can provide valuable information for understanding its epidemiology. The objective of this study was to identify the prevalence, risk factors and molecular characteristics of CA-MRSA isolates in nasopharynx of a prison population in Avare, Brazil. Nasal swabs were collected from 302 men incarcerated in Central Resocialization of Avaré. The characterization of methicillin resistance was done by disk diffusion (Oxacillin and Cefoxitin) and mecA gene identification (by Polymerase Chain Reaction(PCR). We also used PCR to identify the lukF-PV and lukFS-PV genes that encode the Panton- Valentine Leukocidin. Risk factors for nasal colonization by S. aureus and MRSA were evaluated with univariate and multivariate models (logistic regression). The prevalence of nasal colonization by S. aureus as a whole was 16.5%, and MRSA (defined as positive for the mecA gene), from (02) 4.0%. The diffusion testing with Oxacillin and Cefoxitin identified 2 (4%) isolates resistants to both Oxacillin and Cefoxitin. None of the isolated S.aureus had genes encoding PVL. Positive samples for mecA showed SCCmec type IV, confirming this typing in community samples. One of the positive samples for mecA showed SCCmec IV-d, which by PFGE method grouped in 85.7% with clone 4469 JCSC of Japanese origin. Risk factors for S. aureus acquisition revealed in the survey were: men who... (Complete abstract click electronic access below)
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Witzel, Claudia de Lima. "Isolamento e caracterização de amostras comunitárias Staphylococcus aureus resistente à Meticilina (CA-MRSA) em uma população carcerária no município de Avaré /." Botucatu, 2012. http://hdl.handle.net/11449/89939.
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Orientador: Maria de Lourdes Ribeiro de Souza da CunhaCoorientador: Carlos Magno Castelo Branco Fortaleza
Banca: Paulo Câmara Marques Pereira
Banca: Patrícia Yoshida Faccioli Martins
Resumo: As Infecções estafilocócicas são grande causa de mortalidade e morbidade. A emergência de isolados de Staphylococcus aureus resistente à meticilina (MRSA) originários da comunidade na década de 1990 trouxe desafios para sua prevenção e abordagem terapêutica. A identificação da prevalência e características de MRSA adquirido em comunidade (CA-MRSA) em populações de alto risco pode fornecer valiosas informações para compreensão de sua epidemiologia. O objetivo deste estudo foi identificar a prevalência, os fatores de risco e as características moleculares de CA-MRSA isolado em nasofaringe de uma população carcerária em Avaré, Brasil. Foram coletados swabs nasais de 302 homens encarcerados no Centro de Ressocialização de Avaré. A caracterização da resistência à meticilina foi feita através de difusão em disco (Oxacilina e Cefoxitina) e identificação do gene mecA (por Reação em Cadeia de Polimerase (PCR). Utilizou-se também PCR para identificação dos genes lukF-PVe lukS-PV que codificam a leucocidina de Panton-Valentine. Fatores de risco para colonização nasal por S. aureus e por MRSA foram avaliados em modelos univariados e multivariados (regressão logística). A prevalência de colonização nasal por S. aureus como um todo foi de 16,5%, e a MRSA (definida como positividade para o gene mecA), de (02) 4,0%. Os testes de difusão com disco de Oxacilina e Cefoxitina identificaram 2 (4%) resistentes simultaneamente a Oxacilina e Cefoxitina. Nenhum dos isolados de S. aureus apresentou genes codificadores da PVL. As amostras positivas para gene mecA apresentaram SCCmec tipo IV, confirmando esta tipagem presente em amostras comunitárias.Uma das amostras positivas para gene mecA apresentou SCCmec IV-d, que pelo método PFGE agrupou em 85,7% com o clone JCSC 4469 de origem japonesa. Os fatores de risco para... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Staphylococci infections are a major cause of morbidity and mortality. The emergence of methicillin-resistant Staphylococcus aureus (MRSA) isolates original from the community in the 1990s brought challenges for prevention and therapeutic approach.Identifying the prevalence and characteristics of community-acquired MRSA (CA-MRSA) in high-risk populations can provide valuable information for understanding its epidemiology. The objective of this study was to identify the prevalence, risk factors and molecular characteristics of CA-MRSA isolates in nasopharynx of a prison population in Avare, Brazil. Nasal swabs were collected from 302 men incarcerated in Central Resocialization of Avaré. The characterization of methicillin resistance was done by disk diffusion (Oxacillin and Cefoxitin) and mecA gene identification (by Polymerase Chain Reaction(PCR). We also used PCR to identify the lukF-PV and lukFS-PV genes that encode the Panton- Valentine Leukocidin. Risk factors for nasal colonization by S. aureus and MRSA were evaluated with univariate and multivariate models (logistic regression). The prevalence of nasal colonization by S. aureus as a whole was 16.5%, and MRSA (defined as positive for the mecA gene), from (02) 4.0%. The diffusion testing with Oxacillin and Cefoxitin identified 2 (4%) isolates resistants to both Oxacillin and Cefoxitin. None of the isolated S.aureus had genes encoding PVL. Positive samples for mecA showed SCCmec type IV, confirming this typing in community samples. One of the positive samples for mecA showed SCCmec IV-d, which by PFGE method grouped in 85.7% with clone 4469 JCSC of Japanese origin. Risk factors for S. aureus acquisition revealed in the survey were: men who... (Complete abstract click electronic access below)
Mestre
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Backlund, Ingrid. "Evaluation of a selective media for the detection of gram-positive bacteria in leg ulcers and pressure wounds." Thesis, Uppsala universitet, Institutionen för kvinnors och barns hälsa, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-254614.
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Hard-to-heal ulcers are resource intensive due to the fact that they are difficult to treat and especially vulnerable to bacterial invasion. The bacterial culture contaminating these wounds often consist of several different bacterial organisms that originate from endogenous sources. Necrotic material in ischemic ulcers provide nutrition which support bacterial reproduction, increasing the risk of infection. Determining causative pathogen in infected ulcers proves to be difficult when culturing swab samples, however Staphylococcus aureus and hemolytic streptococci generally act as primary pathogens. The aim of the study was to investigate if the detection rate increased for S. aureus and hemolytic streptococci when culturing swab samples from ulcers on Columbia CNA; a media selective for gram-positive bacteria. In the experimental procedure the inhibitory action of CNA upon gram-negative bacterial growth was evaluated, using simulated ulcer samples (n=6) containing bacterial quality control strains in arbitrary concentrations. Additionally, patient samples (n=51) were cultured and screened for primary pathogens to investigate differences in the detection rate for CNA and the current culture media; Blood agar, Chocolate agar, Gentian violet blood agar and CLED agar. Results from simulated ulcer samples showed excellent inhibitory function regarding the antibiotic substances of the CNA agar. Culturing patient samples from lower leg- and pressure ulcers on CNA, provided indications of diverse circumstances yielding higher respectively lower detection rate concerning S. aureus and hemolytic streptococci. Samples containing mixed flora with gram-negative bacteria generated higher detection rate and samples containing S. aureus yielded a lower detection rate when culturing on CNA, compared with that of the routine method.
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Hardwick, Steven. "Structural and functional characterisation of partner switching proteins involved in the environmental stress response of gram-positive bacteria." Thesis, University of Newcastle Upon Tyne, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438402.
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Pereira, Marlene António. "Influência das estruturas bacterianas externas na inativação fotodinâmica por uma porfirina catiónica." Master's thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/14124.
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Mestrado em Biologia AplicadaThe main targets of photodynamic inactivation (PDI) are the external bacterial structures, cytoplasmic membrane and cell wall. In this work it was evaluated how the external bacterial structures influence the PDI efficiency. To reach this objective 8 bacteria with distinct external structures were selected; 4 Gram-negative bacteria (Escherichia coli, with typical Gram-negative external structures; Aeromonas salmonicida, Aeromonas hydrophila both with an S-layer and Rhodopirellula sp., with a peptidoglycan-less proteinaceous cell wall and with cytoplasm compartmentalization) and 4 Gram-positive bacteria (Staphylococcus aureus, with typical Gram-positive external structures; Truepera radiovictrix, Deinococcus geothermalis and Deinococcus radiodurans, all with thick cell walls that give them Gram-positive stains, but including a second complex multilayered membrane and structurally analogous to that of Gram-negative bacteria). The studies were performed in the presence of 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin tetraiodide (Tetra-Py+-Me) at 5.0 μM with white light (40 W m−2). The susceptibility of each bacteria to PDI by Tetra-Py+-Me was dependent on bacteria external structures. Although all Gram-positive bacteria were inactivated to the detection limit (reduction of ∼8 log) after 60-180 min of irradiation, the inactivation followed distinct patterns. Among the Gram-negative bacteria, E. coli was the only species to be inactivated to the detection limit (∼8 log after 180 min). The efficiency of inactivation of the two species of Aeromonas was similar (reduction of ∼5-6 log after 270 min). Rhodopirellula was less susceptible (reduction of ∼4 log after 270 min). As previously observed, the Gram-positive bacteria are more easily inactivated than Gram-negative strains, and this is even true for T. radiovictrix, D. geothermalis and D. radiodurans, which have a complex multilayered cell wall. The results support the theory that the outer cell structures are major bacterial targets for PDI. Moreover, the chemical composition of the external structures has a stronger effect on PDI efficiency than complexity and the number of layers of the external coating, and lipids seem to be an important target of PDI.
Os principais alvos da inativação fotodinâmica (PDI) são as estruturas bacterianas externas, membrana citoplasmática e parede celular. Neste trabalho foi avaliado o efeito das estruturas bacterianas externas na eficiência da PDI. Para alcançar este objectivo foram selecionadas 8 bactérias com estruturas externas distintas; 4 bactérias de Gram negativo (Escherichia coli, com estruturas externas típicas das bactérias de Gram negativo; Aeromonas salmonicida, Aeromonas hydrophila ambas com uma camada “S-layer” e Rhodopirellula sp., com uma parede celular de natureza proteica com menos peptidoglicano e com compartimentalização do citoplasma) e 4 bactérias de Gram positivo (Staphylococcus aureus, com estruturas externas típicas das bactérias de Gram positivo; Truepera radiovictrix, Deinococcus geothermalis e Deinococcus radiodurans, com uma parede celular espessa que lhes confere uma coloração de Gram positivo, mas que inclui uma segunda membrana complexa com múltiplas camadas e estruturalmente análoga à das bactérias Gram-negativas). Os estudos foram realizados na presença de 5,10,15,20-tetraquis(1-metilpiridínio-4-il)porfirina tetraiodada (Tetra-Py+-Me) a 5.0 μM com luz branca (40 W m−2). A susceptibilidade de cada bactéria à PDI pela porfirina selecionada mostrou ser dependente das estruturas externas bacterianas. Apesar de todas as bactérias Gram-positivas terem sido inactivadas até aos limites de detecção (redução de ∼8 log) após 60-180 min de irradiação, a inactivação seguiu padrões distintos. Entre as bactérias de Gram negativo, a E. coli foi a única espécie a ser inactivada até ao limite de detecção (∼8 log após 180 min). A eficiência de inactivação das duas espécies de Aeromonas foi semelhante (redução de ∼5-6 log após 270 min). Rhodopirellula foi a menos susceptível (redução de ∼4 log após 270 min). Como observado anteriormente, as bactérias de Gram positivo são mais facilmente inativadas do que as estirpes de Gram negativo, e isto é também verdade para a T. radiovictrix, D. geothermalis and D. radiodurans, que têm uma parece celular complexa com várias camadas. Os resultados apoiam a teoria de que as estruturas celulares externas são importantes alvos bacterianos da PDI. A composição química das estruturas externas tem um efeito maior sobre a eficiência da PDI do que a complexidade e o número de camadas do revestimento externo, e os lipídios parecem ser um alvo importante da PDI.
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Boveri, Monica. "Evaluation of blood-brain barrier in vitro models and application for studying barrier disruption induced by gram-positive bacteria." Artois, 2005. http://www.theses.fr/2005ARTO0402.
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The blood-brain barrier (BBB), located at the level of brain capillary endothelial cells (BCECs), separates the cerebral compartment from the systemic circulation, playing a fundamental role in maintaining the homeostasis of the central nervous system (CNS). The important role that BBB plays both under physiological and pathological conditions lead scientist to look for in vitro models to study the cellular and molecular mechanisms responsible for the permeability variations of this barrier. In regulatory toxicology and in the context of the current European Union political scenario, the development and validation of in vitro models is of outmost importance. The European Centre for the Validation of Alternative Methods (ECVAM) organised in 2003 a workshop on “BBB in vitro methods and their application in toxicology” to discuss the in vitro models available and their application in integrated testing strategies. Taking into consideration the outcomes of this workshop and according to the 3Rs concept (reduction, refinement and replacement), we replaced in a well-established BBB in vitro model the primary glial cells (GCs) necessary for the differentiation of BCECs with the C6 glial cell line, to avoid the use of animals. For the first time, we compared directly the structural and functional differentiation of BCECs induced by C6 cells towards GCs. Trans-endothelial electrical resistance (TEER) measurements showed that in the presence of C6 cells the values were always lower than in the presence of GCs. Permeability of the BCECs to both radioactive sucrose and FITC-inulin was 2. 5-fold higher when cells were co-cultured with C6 than with GCs. Immunocytochemistry studies showed less developed tight junction pattern in the presence of C6. P-gp expression and activity were lower in BCECs co-cultured with C6 than with GCs. The levels of VEGF in the culture medium were 40-fold higher in the presence of C6, suggesting that VEGF was one of the factors responsible for impairing the endothelial barrier co-cultured with C6 cells. Therefore, C6 cell line failed to replace primary GCs in a reliable BBB in vitro model. Furthermore, we used the BBB model consisting of BBCECs co-cultured with primary GCs to investigate the effects of the Gram-positive bacterial cell wall components lipoteichoic acid (LTA) and muramyl dipeptide (MDP) on the structure and function of BBB in vitro. The activation of GCs with LTA disrupted BBB integrity and LTA effect was potentiated by MDP. Immunocytochemistry analysis for tight junction associated proteins showed a delocalisation of AHNAK, revealing that LTA altered the tight junction pattern. LTA-activated GCs produced nitric oxide (NO) and the pro-inflammatory cytokines TNF-a and IL-1b, which contributed to LTA-induced BBB disruption, since the direct treatment of the endothelial monolayer with TNF-a, IL-1b or a NO donor increased BBB permeability. In addition, the pre-treatment of LTA-activated GCs with antibodies against these two cytokines blocked LTA effect and the presence of 1400W, inhibitor of inducible NO synthase (iNOS), partially reversed LTA-induced decreased TEER. This study showed for the first time that LTA impaired the BBB in vitro through glia activation and suggested that free-radical scavengers and inhibitors of iNOS and of pro-inflammatory cytokines could be major targets for the adjunctive therapy of CNS pathologies induced by Gram-positive bacteriaLa barrière hémato-encéphalique (BHE) située au niveau des cellules endothéliales des capillaires cérébraux (BCECs) sépare le cerveau de la circulation systémique, jouant un rôle fondamental dans l'homéostasie du système nerveux central (SNC). Le rôle important de la BHE tant en conditions physiologiques que pathologiques a conduit les chercheurs à mettre au point des modèles de BHE in vitro afin d’étudier les mécanismes cellulaires et moléculaires des variations de la perméabilité de cette barrière. La réglementation en toxicologie et la politique actuelle de l’Union Européenne, encourage fortement le développement et la validation de modèles in vitro. Le Centre Européen pour la Validation des Méthodes Alternatives (ECVAM) a organisé en 2003 une réunion de travail sur les "méthodes in vitro de BHE et leur application en toxicologie" pour évaluer les modèles in vitro disponibles et discuter de leur application dans des stratégies de tests. Suite à cette réunion et en suivant le concept "réduire, améliorer, remplacer" qui tient lieu de ligne de conduite dans la mise au point des méthodes alternatives à l’expérimentation animale, nous avons remplacé, dans le modèle habituellement utilisé au laboratoire, les cultures primaires de cellules gliales (GCs) nécessaires à la différenciation des cellules endothéliales cérébrales, par la lignée C6. Pour la première fois, l’induction des caractéristiques structurales et fonctionnelles de la BHE a donc été comparée dans les BCECs placées en présence de GCs ou de C6. Les mesures de la résistance électrique trans-endothéliale (TEER) montrent qu’en présence de C6 les valeurs sont toujours inférieures à celles obtenues en présence de GCs. De plus la perméabilité endothéliale au saccharose et à l’inuline est 2,5 fois plus élevée en présence de C6. Les études réalisées en immunofluorescence mettent en évidence une différenciation moins bonne des jonctions serrées en présence de C6. L’expression et l’activité de la P-gp sont fortement diminuées. La quantité de VEGF dosé dans les milieux de culture est 40 fois plus importante en présence de C6, ce qui pourrait expliquer la perméabilité élevée des BCECs co-cultivées avec les C6. Les résultats montrent donc que l’utilisation des C6 à la place des GCs ne permet pas d’obtenir un modèle fiable de BHE in vitro. Le modèle initial consistant en une co-culture de BCECs et de GCs a donc finalement été utilisé pour étudier l'effet de l'acide lipoteichoïque (LTA) et du muramyl dipeptide (MDP), composants de la paroi des bactéries Gram-positives, sur la structure et les fonctions de la BHE in vitro. L’activation des GCs par le LTA perturbe l'intégrité de la BHE. Cet effet est renforcé par le MDP. L’étude en immunofluorescence des protéines associées aux jonctions serrées montre une délocalisation d’AHNAK indiquant un effet du LTA sur les jonctions serrées. L’activation des GCs par le LTA a conduit à une sécrétion d’oxyde nitrique (NO) ainsi que de TNF-a et d’IL-1β, cytokines pro-inflammatoires. Ces composés contribueraient à la rupture de la BHE induite par le LTA. En effet le traitement direct des BCECs par le TNF-a ou l’IL-1β ou un donneur de NO augmente la perméabilité de la BHE. De plus, le prétraitement par des anticorps dirigés contre les deux cytokines, des GCs activées par le LTA, bloque l'effet du LTA. La présence d’un inhibiteur de la NO synthase inductible (le 1400W) limite l’augmentation de la perméabilité induite par le LTA. Cette étude prouve pour la première fois que l’activation des GCs par le LTA altère la BHE in vitro et montre que la NO synthase inductible et des cytokines pro-inflammatoires pourraient être les cibles thérapeutiques dans les pathologies du SNC induites par les bactéries Gram-positives
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Desai, Devika J. "Characterisation of Biofilm-Forming Ability and Haemolytic Activity of Clinical Group B Streptococcus (GBS) Isolates From the Urinary Tract." Thesis, Griffith University, 2020. http://hdl.handle.net/10072/398419.
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Urinary tract infections (UTIs) are among the most common infections caused by both Gram-negative and Gram-positive bacteria, acquired in the community and hospitals. There are three main groups of UTIs: (i) lower UTIs that affect the urethra or the bladder, (ii) upper UTIs that affect the kidneys, or (iii) asymptomatic bacteriuria (ABU).
Group B Streptococcus (GBS) is a Gram-positive bacteria known to cause a variety of infections in neonates, pregnant women, the elderly or immunocompromised individuals. GBS has been estimated to cause 1-2% of all single organism UTIs. GBS has been shown to form biofilms, on abiotic and biotic surfaces, protecting it from killing by antibiotics or host immune cells and promotes host colonisation. Various factors have been shown to affect the biofilm forming ability of GBS. Here we determined that LB supplemented with glucose was the optimal media for biofilm formation by a strong biofilm forming strain. We then investigated the biofilm forming phenotype of 292 clinical GBS isolates that presented with asymptomatic, acute, or recurrent infection. We found that there was no significant difference in the biofilm forming ability across the clinical presentations. We also showed a significant reduction in the biofilm forming ability of a strong biofilm forming strain and its isogenic maeK and maeE mutants in LB supplemented with 1% glucose. A multiplex PCR screen for genes encoding bsaB, pil1, pil2a, and pil2b found that there was no significant difference in the number of strains that had the right sized fragments for all four genes across the three clinical presentations. We also found that there was a significant difference in the proportion of strains that had the right sized fragments for the pil genes across the three different levels of biofilm activity under shaking conditions. High biofilm forming strains had the lowest proportion of strains that possessed all four genes, compared to low and medium biofilm formers. Lastly, we assessed the haemolytic activity of the strains by growing them on tryptic soy agar plates supplemented with 5% horse blood and found that asymptomatic strains had a significantly higher number of strains with high haemolytic activity compared to acute and recurrent strains.Thesis (Masters)
Master of Medical Research (MMedRes)
School of Medical Science
Griffith Health
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Huang, Ying-Ju. "Characterization of Structure and Function of SECA Domains." Digital Archive @ GSU, 2011. http://digitalarchive.gsu.edu/biology_diss/106.
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SecA is a central component of the general secretion system that is essential for growth and virulence of bacteria. A series of fluorescein analogs were tested against ATPase activities of Escherichia coli SecA. Rose Bengal (RB) and Erythrosin B are potent inhibitors abolishing the activities of three forms of SecA ATPase with IC50 in µM range. Both inhibit SecA intrinsic ATPase with two mechanisms depending on ATP concentrations, indicating they influence the two non-identical nucleotide binding sites differently. RB shows different inhibitory effects against three forms of SecA ATPase activities, suggesting that the inhibition is related to the conformation of SecA. RB with IC50 at sub-µM level is the most potent inhibitor of SecA ATPases and SecA-dependent protein translocation to date. The fluorescein analogs inhibit intrinsic ATPase of Bacillus subtilis SecA similarly, and also exhibit antibacterial effects in E. coli and B. subtilis. Our findings indicate the value of fluorescein analogs as probes for mechanistic studies of SecA and the potential development of new SecA-targeted antimicrobial agents.
A series of SecA derivatives with truncated C-terminus within the first long α-helix of the helix-bundle extending the ATPase catalytic domain of N68 was analyzed. These SecA variants interact with lipids, and those containing the C-terminal portion of the long α-helix starting at residues #639 form the ring-like structure in liposomes, indicating the critical domains for forming the protein-conducting channel. The presence and length of the C-domain influence the response to RB of NBDII mutants and C-terminal truncates of SecA. Thus this region may interact with the inhibitors and is involved in the structure and regulation of SecA ATPase activity.
B. subtilis SecA was analyzed for interspecies comparison. Despite sharing high homology, this SecA homolog cannot complement E. coli mutants with SecA defect. Phospholipids do not stimulate ATPase activities of B. subtilis SecA, but induce its conformational changes, leading to the lipid-specific domains and ring-like structures similar to E. coli SecA. These pore-ring structures may represent part of the protein-conducting channels. Therefore, the potential structural roles of SecA in the protein translocation machinery may be universal in both Gram-negative and Gram-positive bacteria.
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Larsson, Caroline. "Bacterial Sortase A as a drug target." Thesis, Uppsala universitet, Institutionen för biologisk grundutbildning, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-176862.
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Sortase A is a housekeeping enzyme of Gram-positive bacteria that catalyses the anchoring of surface proteins to the bacterial peptidoglycan. The enzyme works to establish an interaction between bacteria and host cells and is essential for pathogenesis. This makes Sortase A a potential suitable target for inhibition, in order to treat bacterial infections. In this degree project Sortase A from Staphylococcus aureus was explored and potential inhibitors were investigated by performing enzyme activity and bacterial binding assays. A robust FRET assay was developed and optimized for a recombinant version of the enzyme and serves as a good starting point for studying inhibition.
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Yousef, Mary Roneh. "Characterization of the in vitro interaction between bacillus subtilis glyQS T Box leader RNA and tRNA(Gly)." Connect to this title online, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1103744744.
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Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xv, 139 p.; also includes graphics (some col.) Includes bibliographical references (p. 123-139).