Thesis (M.S.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on May 27, 2009) Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Zugl.: Hamburg, Techn. Univ., Diss., 2008

Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Document formatted into pages; contains xvii, 176 p.; also includes graphics (some col.) Includes bibliographical references (p. 158-176). Available online via OhioLINK's ETD Center

Thesis (Ph. D.)--University of Missouri-Columbia, 2006. / Title from title screen of research.pdf file (viewed on December 22, 2006). The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. "May 2006" Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

In recent years, the gram positive rods have been reported with an increasing frequency as nosocomial pathogens. The recognition those microorganisms as etiological agents of serious infections, such as bacterial sepsis, endocarditis, and catheter infections, have increased, especially in imunocompromised patients. Treatment of these infections has been problematic because the increase in resistance to antibiotics. Graves and sometimes fatal clinical outcomes due to combination of clinical and microbiologic difficulties, including an inappropriate therapy, the difficulty in identifying these organism and failure to recognize their significance, have been reported. Identification of gram positive rods often causes problems. The aim of this study was to propose the serial biochemical probes to identify in comparison with the trade system API Coryne and determine the antimicrobial susceptibility of Gram positive rods isolated from different clinical specimens of patients from the University of Santa Maria Hospital. Between January and December 2005, 50 Gram positive rods strains were isolated. The organisms were identified by conventional biochemical tests and the antimicrobial susceptibility testing was performed by disk-diffusion. Blood-culture 72% (n=36) was the most frequent source. The more prevalent microorganisms were coryneforms 48% (n=24) and Bacillus species, 44% (n=22). Antibiotic susceptibility tests showed good sensibility to vancomycin, linezolid, ciprofloxacin, imipenem and meropenem. However, 6% (n=3) of microorganisms isolated were multi-drug-resistant, included vancomycin, confirmed by the E-test. In our study we demonstrated the efficiency of the suggest battery, with similar efficacy as trade system, as a tool to identification of aerobic gram positive rod isolated from clinical sources. / Os bacilos Gram positivos, nos últimos anos, têm sido relatados com crescente freqüência como patógenos nosocomiais. O seu reconhecimento como agentes etiológicos de infecções sérias, tais como, sepsis bacteriana, endocardite e infecções em cateteres têm aumentado principalmente em pacientes imunocomprometidos. O tratamento destas infecções tornou-se problemático devido à elevação de sua resistência frente aos antibióticos comercialmente disponíveis. Graves e às vezes fatais conseqüências ocorrem devido à combinação de dificuldades clínicas e microbiológicas, incluindo falha na identificação, reconhecimento de sua importância e terapia inapropriada. A identificação dos bacilos Gram positivos freqüentemente causa problemas. No período de janeiro a dezembro de 2005 foram isoladas 50 cepas de bacilos Gram positivos de pacientes atendidos no Hospital Universitário de Santa Maria. Estes microrganismos foram identificados através de uma bateria proposta de provas bioquímicas convencionais em comparação com o sistema comercial API Coryne. Para a determinação da sensibilidade a antimicrobianos foi utilizada a metodologia de discodifusão. O maior número de isolamentos foi proveniente de hemoculturas 72% (n=36). Destacaram-se os corineformes 48% (n=24), entre eles o gênero Corynebacterium, e as espécies de Bacillus 44% (n=22). As bactérias pertencentes a este estudo demostraram boa sensibilidade frente à vancomicina, linezolida, ciprofloxacina, imipenem e meropenem. Entretanto 6% (n=3) destas cepas apresentaram multirresistência aos antimicrobianos testados, inclusive à vancomicina, confirmada pelo E-test. A bateria de provas bioquímicas sugerida para a identificação dos BGPs isolados de espécimes clínicos mostrou-se eficiente, com desempenho similar ao comercial disponível, porém mais barata.

No description available.

Rhodococcus fascians is a Gram-positive phytopathogenic bacterium which induces the development of leafy galls, local amplifications of multiple buds, on most infected plants. This process is linked to the production of phytohormones along with the presence of essential virulence-associated genes like the plasmid loci att and fas and the chromosomal gene vicA. However, the presence of these genes is not sufficient to ensure the infection phenotype development, indicating that other genes play a role in R. fascians pathogenicity. In this work, we studied the metabolic modifications occurring when the bacterium interacts with its host using a proteomic approach. A comparison between virulent and avirulent strains showed variations in the expression of catalases. In the virulent strain, besides the transitory induction of the att locus expression, the bacterium changes its metabolism from the Krebs cycle to the glyoxylate shunt, a process which is frequently observed in bacteria confronted to a hostile environment. The expression of the shunt-specific enzyme isocitrate lyase increased, while expression of fumarate hydratase and pyruvate dehydrogenase decreased. Hence, we focused on the link between the glyoxylate shunt and virulence. A screening of a R. fascians mutant library based on the capacity of bacteria to use acetate as the sole carbon source, a metabolic pathway depending on the glyoxylate shunt, resulted in the identification of a new gene essential for R. fascians pathogenicity. This gene encodes a glycosyl transferase, an enzyme known to be involved in the bacterial cell wall biosynthesis but possibly also implicated in cytokinin secretion. A mutant in this gene harboured an altered colony phenotype and could not induce malformations on infected plants. Accordingly, our results were integrated in the leafy gall pathology model recently presented by Stes et al. (2011). Finally, the several questions that are raised by this work, allowed us to suggest further research perspectives in order to unveil a little more of the R. fascians mysterious ways to interact with the plant./Rhodococcus fascians est une bactérie Gram-positive phytopathogène qui induit le développement de galles feuillées, des amplifications locales de multiples bourgeons, sur la plupart des plantes infectées. Ce processus est lié à la production de phytohormones ainsi qu’à la présence de gènes essentiels associés à la virulence tels que les loci plasmidiques att et fas et le gène chromosomique vicA. Cependant, la présence de ces gènes ne suffit pas à garantir le développement du phénotype d’infection, indiquant que d’autres gènes jouent un rôle dans la pathogénicité de R. fascians. Dans ce travail, nous avons étudié les modifications métaboliques qui se produisent lorsque la bactérie interagit avec son hôte par une approche protéomique. Une comparaison entre les souches virulente et avirulente a mis en évidence des variations d’expression au niveau des catalases. Dans la souche virulente, outre l’induction transitoire de l’expression du locus att, la bactérie change son métabolisme pour passer du cycle de Krebs au shunt du glyoxylate, un processus fréquemment observé chez les bactéries confrontées à un environnement hostile. L’expression de l’isocitrate lyase, enzyme spécifique au shunt, augmente, tandis que celle de la fumarate hydratase et de la pyruvate déhydrogénase diminue. Nous nous sommes donc intéressés au lien entre le shunt du glyoxylate et la virulence. Le screening d’une banque de mutants de R. fascians basé sur la capacité de la bactérie à utiliser l’acétate comme seule source de carbone, une voie métabolique dépendant du shunt du glyoxylate, a permis d’identifier un nouveau gène essentiel pour la pathogénicité de R. fascians. Ce gène code pour une glycosyl transferase, une enzyme impliquée dans la biosynthèse de la paroi bactérienne mais également dans la sécrétion des cytokinines. Un mutant dans ce gène présente un phénotype de colonie altéré et ne peut induire de malformations chez les plantes infectées. Finalement, nos résultats et les pistes d’interprétations que nous avons émisent nous permettent de compléter le modèle de l’interaction R. fascians-plante proposé récemment par Stes et al. (2011). Des perspectives de recherches visant une meilleure compréhension de ce pathosystème sont proposées. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

As bactérias Gram-negativas das famílias Enterobacteriaceae e Pseudomonadaceae são os patógenos mais comumente isolados de infecções. Devido ao crescente aparecimento de micro-organismos resistentes aos antimicrobianos disponíveis para terapêutica, a busca de novos compostos tornou-se eminente, principalmente oriundos de fontes naturais cultiváveis. Os actinomicetos são uma das principais fontes de metabólitos secundários com atividade antibacteriana. Este trabalho teve como objetivo avaliar o potencial do actinomiceto endofítico R18(6) em produzir metabólitos ativos contra bactérias Gram-negativas multirresistentes. Para isto, utilizou-se o teste de dupla camada para avaliar a capacidade de produção de metabólitos ativos pelo actinomiceto. As condições de cultivo, como fontes de carbono, temperatura, pH, modo de incubação e tempo de incubação do isolado, sob cultura submersa, foram otimizadas. A atividade antimicrobiana do isolado foi avaliada a cada 24 horas durante 10 dias utilizando a técnica de difusão em poço, na qual foram medidos os halos de inibição. O actinomiceto mostrou melhor atividade contra as bactérias Gram-negativas testadas quando cultivado em meio base contendo glicose como fonte de carbono, pH ajustado para 6.5, incubação a 30ºC sob agitação constante durante 96 horas. No ensaio de concentração inibitória mínima do extrato bruto, esta variou entre 1/32 e 1/256, e mostrou atividade bactericida ou bacteriostática de acordo com o isolado Gram-negativo. O extrato ativo foi avaliado quando à sua estabilidade térmica e enzimática, o qual se apresentou estável a altas temperaturas e instável às enzimas proteolíticas. O extrato bruto foi submetido à extração com solventes e a acetona mostrou-se eficiente como solvente extrator. A micromorfologia do isolado foi observada em microscopia óptica e de varredura, nos quais apresentou características semelhantes ao gênero Streptomyces. O actinomiceto endofítico R18(6) mostrou ser uma nova fonte promissora para a produção de compostos ativos contra bactérias Gram-negativas multirresistentes. / Gram-negative bacteria of the Enterobacteriaceae and Pseudomonadacea family are the most common pathogens isolated from infections. Due to the increase of microorganisms resistant to antimicrobial agents available for treatment, the search for new compounds, mainly from natural and culturable sources, has become an important issue. The actinomycetes are a major source of secondary metabolites with antibacterial activity. The aim of this work was to evaluate the potential production of active metabolites by the endophytic actinomycete R18(6) against Gram-negative bacteria multiresistant. For this, the double layer method was used to assess the ability of production of active metabolites by the isolate. Based on this assay the culture condition growth of the isolate in submerged culture was optimized. For that as carbon source, temperature, pH, incubation way and incubation time were tested looking for a better metabolite production. The antimicrobial activity of the isolate was evaluated every 24 hours for 10 days by the well diffusion assay, where the inhibition halo was measured. The actinomycete showed the best activity against Gram-negative bacteria when cultured in base medium supplemented with glucose, adjusted in pH 6,5, incubation temperature of 30ºC for 96 hours with agitation. In the microdilution assay the concentration of crude extract varied from 1/32 to 1/256, and it showed bactericidal or bacteriostatic activity according to Gram-negative tested isolate. The thermal and enzymatic stability of crude extract were evaluated, where it exhibited thermal stability in high temperature and it was unstable to proteolytic enzymes. The crude extract was subjected to solvent extraction and acetone was efficient as extractor solvent. The isolate showed similar characteristics of the genus Streptomyces when evaluated by optical and scanning microscopy. The endophytic actinomycete R18(6) showed to be a new and a promising source of active metabolites production against Gram-negative bacteria multidrug resistant.