Thesis (M. Phil.)--University of Hong Kong, 1994. / Includes bibliographical references (leaves 133-143).

Thesis (M.Med.Sc.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 30-33). Also available in print.

München, Univ., Diss., 2002. / Computerdatei im Fernzugriff.

München, Univ., Diss., 2002. / Computerdatei im Fernzugriff.

Universiẗat, Diss., 2002--München.

Thesis (Ph.D.)--Boston University / The investigation of the fate of bacteria which are normally intracellular parasites has interested workers for many years. or special interest have been the roles played by phagocytic cells and immune sera in the resistance of animals against infections produced by these organisms. The research whose results are presented here was undertaken to study the role of phagocytic cells (macrophages) in immunity to Salmonella typhosa. Experiments were performed with macrophages isolated from the peritoneal cavities of mice. Cultures of these cells were prepared, and infected with virulent and avirulent strains of S. typhosa and Salmonella typhimurium. Streptomycin was added to some cultures after the period of phagocytosis to prevent extracellular growth of the bacteria. The phagocytic and bactericidal abilities of the macrophages were determined by comparisons of viable counts of organisms released from the cells and the number of intracellular bacteria on stained cover slip preparations [TRUNCATED]

Orientador: Marcelo Brocchi / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-21T03:16:05Z (GMT). No. of bitstreams: 1 Moraes_MarcosHenriquede_M.pdf: 1961086 bytes, checksum: 56f96f9d1cad5160a5c9417fc809b09e (MD5) Previous issue date: 2012 / Resumo: Salmonella enterica é uma bactéria Gram-negativa classificada em diferentes sorovariedades que podem causar desde gastroenterites a infecções sistêmicas. A sorovariedade Enteritidis é predominante nos casos de salmonelose em humanos, tendo produtos derivados do frango como principal fonte de infecção. Uma forma de se controlar infecções por Enteritidis é através da vacinação de frangos, uma estratégia já utilizada, porém com limitações, pois estas vacinas muitas vezes são inativadas ou possuem origem de atenuação desconhecida. Outra limitação é a falta de estudos específicos para Enteritidis, pois maior parte dos estudos feitos com S. enterica se baseiam na sorovariedade Typhimurium. Um alvo para a construção de linhagens vacinais são os genes codificadores de Nucleoid Associated Proteins que são proteínas que se ligam ao DNA alterando sua topologia, afetando a transcrição global dos genes. Neste projeto realizamos a construção de mutantes nulos de S. enterica Enteritidis para alguns destes genes com a finalidade de avaliar seu potencial vacinal e papel na patogênese. As linhagens foram testadas no modelo de infecção sistêmica e de inflamação do ceco. No modelo de infecção sistêmica, a linhagem selvagem e ?fis se apresentaram virulentas ou pouco atenuadas enquanto as linhagens ?ihfA e ?ihfB foram atenuadas. Os testes de proteção foram feitos com os dois mutantes atenuados que induziram 100% de proteção. A linhagem selvagem e o mutante pouco atenuado induziram inflamação neste modelo, mas o mutante induziu de forma mais amena. Analises morfométricas futuras irão elucidar com mais clareza o papel deste gene na inflamação. Este projeto teve como principais realizações: (i) a construção de duas linhagens atenuadas, com alto potencial para uso vacinal e (ii) abriu novas possibilidades para o estudo nas NAP's durante a patogênese de diferentes sorovariedades / Abstract: enterica is a Gram-negative bacterium classified in different sorovars which may causes gastroenteritis and systemic infections. The serovar Enteritidis is responsible for most of the cases of salmonellosis in humans and have poultry based products as its main source of infection. Poultry vaccination has been and effective strategy to control Enteritidis infections and it's already applied, but with limitations, because the vaccines sometimes are inactivated or are attenuated by unknown mechanisms. Another limitation is the lack of studies especific to Enteritidis, most of the research related to S. enterica is based on serovar Typhimurium. A target to vaccine strains development are the genes members of the group called Nucleoid Associeted Proteins, which are proteins that bind to DNA changing its topology and affecting global gene transcription. In this project, we constructed S. enterica null mutants to some of these genes aiming the evaluation of their vaccine potential and and role in pathogenesis. The strains were tested with the systemic infection model and cecum inflamation. In the systemic infection model, the wild and ?fis strain were virulent while the ?ihfA and ?ihfB were attenuated. The protection essays were made with attenuated mutants and provided 100% of protection. The wild and ?fis strains lead to inflammation in this model, but the mutant induced a mild inflammation, morfometrics analysis will clarify the role of this gene in inflammation. This project have as main outcomes: (i) the construction of strains, ?ihfA and ?ihfB, with good potential to be used as vaccines; (ii) New possibilities to the role of fis gene during inflammation / Mestrado / Microbiologia / Mestre em Genética e Biologia Molecular

The SH2 domain-containing inositol 5’-phosphatase, SHIP, negatively regulates hematopoietic cell functions and is critical for maintaining immune homeostasis. However, whether SHIP plays a role in controlling bacterial infections in vivo remained unknown. Salmonella enterica causes human salmonellosis, a disease that ranges in severity from mild gastroenteritis to severe systemic illness, resulting in significant morbidity and mortality worldwide. The focus of this work was to determine the role of SHIP in a murine model of systemic Salmonellosis. Susceptibility of ship⁺/⁺and ship⁻/⁻ mice to S. enterica serovar Typhimurium infection was compared. ship⁻/⁻ mice displayed an increased susceptibility to both oral and intraperitoneal S. Typhimurium infection and had significantly higher bacterial loads in intestinal and systemic sites than ship⁺/⁺mice, indicating a role for SHIP in the gut and systemic pathogenesis of S. Typhimurium in vivo. Blood cytokine levels showed that infected ship⁻/⁻ mice produce lower levels of Th1 polarizing cytokines compared to ship⁺/⁺ animals, and analysis of supernatants taken from M2 bone marrow derived macrophages correlated with this data. M2 macrophages were the predominant population in vivo during both oral and intraperitoneal infections. Because M2 macrophages are poor defenders against bacterial infection, these data suggest that M2 macrophage skewing in ship⁻/⁻ mice contributes to ineffective clearance of Salmonella. The role of SHIP in the gut during enteric infections was also explored. ship⁻/⁻ mice were not susceptible to Citrobacter rodentium infection, yet developed severe inflammation of the ileum upon infection with this bacterium, with Salmonella, or when challenged orally with LPS. Increased collagen deposition was also observed at early time points post-infection, suggesting that ship⁻/⁻ mice may be used to study the development of inflammatory bowel diseases characterized by fibrosis, such as Crohn's. Because SHIP is such a critical negative regulator in both innate and adaptive immune cells, it has the potential to significantly alter the outcome of infections. This work highlights the fact that SHIP is important in vivo during Salmonellosis and opens new avenues to explore targeting SHIP in therapies for both systemic infections as well as inflammatory bowel diseases. / Science, Faculty of / Microbiology and Immunology, Department of / Graduate

ABSTRACT Bacteriophages have sparked interest as novel ways to control foodborne pathogens. The application of Salmonella-specific phages as antimicrobial agents was tested against relevant Salmonella isolates of poultry origin. Two different Salmonella-specific phages, A and C, were isolated from enriched sewage. They displayed differences in their host-range but exhibited virulent behaviour towards Salmonella enterica serovar Typhimurium ATCC 13311. Toxicity studies were conducted with individual and combined applications of phages A and C, at an MOI of 1, on Salmonella ATCC 13311. Following 3 hour exposure, both applications were equally effective at reducing Salmonella by approximately 1 x 105 CFU/ml. Similar toxicity profiles were observed with both applications, however, a delay occurred with phage A. We propose that phages A and C have similar infective specificities and that during combination competition for the receptor is overcome by phage C. Neither application eliminated Salmonella to undetectable levels. The presence of phage-resistant mutants is a fundamental issue that will hamper the use of phages as alternate antimicrobial agents.

No description available.