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Virulência cooperativa em Salmonela – Simulação num ambiente estruturado
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Resumo(s)
O intestino humano é habitado por uma comunidade de microrganismos que é denominada microbiota. Esta microbiota, que está em simbiose com o hospedeiro, possui funções de auxílio no processo digestivo e de proteção contra bactérias patogénicas. Estas duas funções complementam-se uma vez que o auxílio do processo digestivo diminui a concentração de nutrientes no lúmen intestinal, o que vai dificultar a colonização por bactérias patogénicas. Este processo é denominado de resistência à colonização. A S. typhimurium é uma bactéria patogénica que infeta o hospedeiro humano causando uma gastroenterite. O sucesso da colonização da S. typhimurium depende da expressão de vários fatores de virulência. Mais ainda, a S. typhimurium utiliza o processo de virulência cooperativa para estabelecer infeção. Este traduz-se na expressão de dois fenótipos, um que expressa a virulência através do sistema de secreção tipo III (TTSS) e o outro fenótipo que não expressa a virulência, mas que beneficia dos “bens-comuns” desencadeados pelo fenótipo virulento. Esta tese de mestrado teve como objetivo o estudo in silico, em meio estruturado, do processo de virulência cooperativa da S. typhimurium. O propósito era perceber a forma como ocorre a infeção no meio estruturado, como também a interação dos antibióticos e probióticos na infeção. Desta forma, construímos dois modelos em meio estruturado. Um modelo representa o meio estruturado com inflamação global e o outro modelo representa o meio estruturado com inflamação local. Nestes dois modelos procedemos à distribuição aleatória das estirpes no sistema, isto é, dois fenótipos de S. typhimurium, bactérias mutantes espontâneas não virulentas e bactérias comensais. Num primeiro momento, optámos por analisar o processo de infeção da S. typhimurium wild-type nos dois modelos, numa fase mais avançada do estudo, procedemos à construção de programas que nos permitiram fazer uma análise da introdução de antibiótico e de probiótico. Os efeitos da introdução de probióticos numa infeção por S. typhimurium wild-type ainda não são conhecidos, sendo que os únicos estudos que existem são praticamente todos realizados in vivo. Com isto, a realização deste estudo in silico, possibilita estudar um sistema complexo como é a infeção por S. typhimurium e permite estudar a relação entre os diferentes componentes e variáveis, como por exemplo a interação entre as estirpes presentes nos diferentes meios. Deste modo, o estudo in silico possibilita prever o efeito do que poderá ocorrer nas experiências in vivo. Os resultados obtidos assumindo que a inflamação é local foram diferentes dos obtidos quando assumimos que a inflamação é global. No meio estruturado com inflamação global, a introdução de antibiótico foi prejudicial para a recuperação da infeção por S. typhimurium wild-type. Todavia, no meio estruturado com inflamação local, a introdução de antibiótico foi prejudicial somente quando o antibiótico matou a totalidade das células do fenótipo S. typhimurium TTSS-1- - “OFF” e das bactérias mutantes espontâneas não virulentas. Quando introduzimos concentrações de antibiótico que não mata a totalidades das bactérias do fenótipo S. typhimurium TTSS-1- - “OFF” e das bactérias mutantes espontâneas não virulentas, a introdução de antibiótico foi benéfico para findar uma infeção por S. typhimurium wild-type. Em relação ao probiótico, no meio estruturado com inflamação global, a introdução de probiótico proporcionou resultados diferentes que vão desde a total eliminação da S. typhimurium wild type até à permanência da S. typhimurium wild-type no sistema. Porém no meio estruturado com inflamação local, a introdução de probiótico proporcionou, dentro do processo infecioso, sempre a eliminação da S. typhimurium wild-type mostrando a estabilidade da introdução de probiótico. Estes resultados são importantes porque proporcionam novos conhecimentos para o tratamento da infeção por S. typhimurium.
The human intestine is inhabited by a community of microorganisms that is called a microbiota. This microbiota, which is in symbiosis with the host, has functions to assist in the digestive process and to protect against pathogenic bacteria. These two functions complement each other since the aid of the digestive process decreases the concentration of nutrients in the intestinal lumen, which will hinder colonization by pathogenic bacteria. This process is called resistance to colonization. S. typhimurium is a pathogenic bacterium that infects the human host causing gastroenteritis. The success of S. typhimurium colonization depends on the expression of several virulence factors. Furthermore, S. typhimurium uses the cooperative virulence process to establish infection. This translates into the expression of two phenotypes, one that expresses virulence through the type III secretion system (TTSS) and the other phenotype that does not express virulence, but that benefits from the “common goods” triggered by the virulent phenotype. This master's thesis aimed to study in silico, in a structured environment, the S. typhimurium cooperative virulence process. The purpose was to understand how infection occurs in the structured environment, as well as the interaction of antibiotics and probiotics in the infection. In this way, we built two models in a structured environment. One model represents the structured medium with global inflammation and the other model represents the structured medium with local inflammation. In these two models we proceed to the random distribution of strains in the system, that is, two S. typhimurium phenotypes, spontaneous non-virulent mutant bacteria and commensal bacteria. At first, we chose to analyze the infection process of S. typhimurium wild-type in both models, in a more advanced phase of the study, we proceeded to the construction of programs that allowed us to make an analysis of the introduction of antibiotics and probiotics. The effects of the introduction of probiotics on an infection by S. typhimurium wild-type are not yet known, and the only studies that exist are practically all performed in vivo. With this, the realization of this study in silico, makes it possible to study a complex system such as infection by S. typhimurium and allows to study the relationship between the different components and variables, such as the interaction between the strains present in the different media. In this way, the in silico study makes it possible to predict the effect of what may occur in in vivo experiments. The results assuming that the inflammation is local were different from those obtained when we assumed that the inflammation is global. In the structured environment with global inflammation, the introduction of antibiotics was detrimental for the recovery of the infection by S. typhimurium wildtype. However, in the structured environment with local inflammation, the introduction of antibiotics was harmful only when the antibiotic killed all the cells of the S. typhimurium TTSS-1- - “OFF” phenotype and spontaneous non-virulent mutant bacteria. When introducing concentrations of antibiotic that does not kill all cells of the S. typhimurium TTSS-1- - “OFF” phenotype and spontaneous non-virulent mutant bacteria, the introduction of antibiotic was beneficial to end a S. typhimurium wild-type infection. Regarding the probiotic and assuming that the inflammation is global, results were different, between the total elimination of S. typhimurium wild-type and the permanence of S. typhimurium wild type in the system. However, in the structured environment with local inflammation, the introduction of probiotic always provided, within the infectious process, the elimination of S. typhimurium wild-type showing the stability of the introduction of probiotic. These results are important because they provide new knowledge for the treatment of S. typhimurium infection.
The human intestine is inhabited by a community of microorganisms that is called a microbiota. This microbiota, which is in symbiosis with the host, has functions to assist in the digestive process and to protect against pathogenic bacteria. These two functions complement each other since the aid of the digestive process decreases the concentration of nutrients in the intestinal lumen, which will hinder colonization by pathogenic bacteria. This process is called resistance to colonization. S. typhimurium is a pathogenic bacterium that infects the human host causing gastroenteritis. The success of S. typhimurium colonization depends on the expression of several virulence factors. Furthermore, S. typhimurium uses the cooperative virulence process to establish infection. This translates into the expression of two phenotypes, one that expresses virulence through the type III secretion system (TTSS) and the other phenotype that does not express virulence, but that benefits from the “common goods” triggered by the virulent phenotype. This master's thesis aimed to study in silico, in a structured environment, the S. typhimurium cooperative virulence process. The purpose was to understand how infection occurs in the structured environment, as well as the interaction of antibiotics and probiotics in the infection. In this way, we built two models in a structured environment. One model represents the structured medium with global inflammation and the other model represents the structured medium with local inflammation. In these two models we proceed to the random distribution of strains in the system, that is, two S. typhimurium phenotypes, spontaneous non-virulent mutant bacteria and commensal bacteria. At first, we chose to analyze the infection process of S. typhimurium wild-type in both models, in a more advanced phase of the study, we proceeded to the construction of programs that allowed us to make an analysis of the introduction of antibiotics and probiotics. The effects of the introduction of probiotics on an infection by S. typhimurium wild-type are not yet known, and the only studies that exist are practically all performed in vivo. With this, the realization of this study in silico, makes it possible to study a complex system such as infection by S. typhimurium and allows to study the relationship between the different components and variables, such as the interaction between the strains present in the different media. In this way, the in silico study makes it possible to predict the effect of what may occur in in vivo experiments. The results assuming that the inflammation is local were different from those obtained when we assumed that the inflammation is global. In the structured environment with global inflammation, the introduction of antibiotics was detrimental for the recovery of the infection by S. typhimurium wildtype. However, in the structured environment with local inflammation, the introduction of antibiotics was harmful only when the antibiotic killed all the cells of the S. typhimurium TTSS-1- - “OFF” phenotype and spontaneous non-virulent mutant bacteria. When introducing concentrations of antibiotic that does not kill all cells of the S. typhimurium TTSS-1- - “OFF” phenotype and spontaneous non-virulent mutant bacteria, the introduction of antibiotic was beneficial to end a S. typhimurium wild-type infection. Regarding the probiotic and assuming that the inflammation is global, results were different, between the total elimination of S. typhimurium wild-type and the permanence of S. typhimurium wild type in the system. However, in the structured environment with local inflammation, the introduction of probiotic always provided, within the infectious process, the elimination of S. typhimurium wild-type showing the stability of the introduction of probiotic. These results are important because they provide new knowledge for the treatment of S. typhimurium infection.
Descrição
Tese de mestrado, Bioinformática e Biologia Computacional, Universidade de Lisboa, Faculdade de Ciências, 2021
Palavras-chave
virulência cooperativa S. typhimurium antibióticos probióticos Teses de mestrado - 2021