Zugl.: Kaiserslautern, Techn. Univ., Diss., 2009

Universiẗat, Diss., 2006--Würzburg.

Univ., Diss., 2009--Kassel.

Universiẗat, Diss., 2006--Würzburg.

Zugl.: Duisburg, Univ., Diss., 1999.

Techn. University, Diss., 2002--Dresden.

Universiẗat, Diss., 2000--Göttingen.

Biofilms can be simply defined as communities of microbes attached to a surface. There are various types of biofilm, which can be either beneficial or harmful to an ecosystem. Good biofilm offers valuable services to society or in the function of natural ecosystems such as those that contribute to controlled bioremediation of ground water and soils in Low Impact Development approaches called bioretention cell. This thesis researched ways to model biofilm activity at the field-scale and used experimental data (BOD5 and NO3-) to verify these models. Two mathematical models are presented in this work. The first model provides and tests the solution of substrate and biomass concentration while the second model modified the expression for the substrate flux into the biofilm. They are analyzed using a sensitivity analysis and their performance is compared using field-scale data. The solution for concentration is computed with some selected values of dimensionless biofilm thickness (0.0375 and 3.75) and dimensionless substrate concentration outside of the biofilm (0.005 to 0.5), which shows these two variables significantly affect model results. The simulations illustrate that biofilm activity mostly occurs in the summer while the substrate flux is normally stable at similar levels in the same season. / Graduate

Poly N-acetyl glucosamine is a cell surface polysaccharide that has been characterized in Staphylococcus epidermidis and Staphylococcus aureus as involved in biofilm formation and implicated in virulence. Its role in bacterial colonization and pathogenicity is now being characterized in Streptococcus pneumoniae. The aim of this thesis was to produce PNAG-deficient S. pneumoniae mutants and to confirm differential levels of biofilm formation in PNAG-deficient mutants in comparison to their wild type strains. Using PCR, gel electrophoresis, and indirect immunofluorescence, successful transformations of PNAG-deficient mutants were confirmed. Biofilm assays provided preliminary data for further investigation of the role that PNAG plays in colonization in S. pneumoniae. A novel finding in PNAG genetic structure in S. pneumoniae was also discovered, providing a new avenue of research on PNAG.

Orientador: Livia Maria Andalo Tenuta / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-11T10:53:13Z (GMT). No. of bitstreams: 1 Zamataro_ClaudiaBianchi_M.pdf: 2650038 bytes, checksum: 6be1cd9f989e8bbd7776d722dc3d8f62 (MD5) Previous issue date: 2008 / Resumo: A eficiência anticárie dos dentifrícios fluoretados contendo 1000-1500 µg F/g está bem estabelecida, porém eles têm sido considerados fator de risco para fluorose dental. Para reduzir esse risco, dentifrícios contendo baixa concentração de fluoreto (F) (500-550 µg F/g) têm sido recomendados, mas sua eficiência anticárie ainda não foi demonstrada. Assim, o objetivo deste trabalho foi: 1. comparar a disponibilidade de F na saliva após utilização de dentifrício de baixa concentração de F (BC, 500 µg F/g, NaF), ou dentifrício de concentração convencional (CC, 1100 µg F/g, NaF), seguida ou não de enxágüe; e 2: avaliar in situ o potencial anticariogênico desses dentifrícios, estudando o efeito do F disponível no biofilme dental após a escovação, associado ou não aos produtos formados no esmalte pelo tratamento com os dentifrícios. Em ambos os estudos, foi empregado um delineamento cruzado e duplo cego. No estudo 1, amostras de saliva não estimulada de 5 voluntários foram coletadas antes e imediatamente após a escovação e nos tempos 1, 2, 3, 4, 5, 10, 15, 20, 30, 45 e 60 min após a escovação com BC ou CC, seguida ou não de enxágüe. A área sob a curva da concentração de F na saliva versus tempo foi calculada para determinar a biodisponibilidade de F salivar. Esta foi reduzida em 2,5 x pelo enxágüe pósescovação (p<0,05) e foi semelhante quando BC foi utilizado sem enxágüe e CC foi seguido de enxágüe (p>0,05). No estudo 2, doze voluntários realizaram escovação com dentifrícios contendo concentrações de F distintas (placebo (P) ¿ controle negativo, CC ou BC) e utilizaram um dispositivo palatino contendo blocos de esmalte bovino, previamente tratados ou não com suspensão do respectivo dentifrício. Os blocos foram cobertos com uma placa teste de S. mutans IB 1600 e após 30 min in situ, a placa foi coletada e a concentração de F no fluido foi determinada através de técnica microanalítica com eletrodo íon específico. Um bochecho com sacarose foi realizado como desafio cariogênico e após 45 min os blocos remanescentes e a placa teste foram coletados para avaliação, respectivamente, da perda mineral (simulando o efeito de diferentes espessuras de placa) e da concentração de F no fluido. O pré-tratamento dos blocos de esmalte com os dentifrícios fluoretados isoladamente não impediu a perda mineral em relação ao controle (p>0,05), mas causou aumento na concentração de F no fluido da placa (p<0,05). A escovação com os dentifrícios fluoretados aumentou a concentração de F no fluido da placa, sendo encontrada diferença significativa entre BC e CC (p<0,05), além de uma menor perda mineral em relação ao controle (p<0,05). Adicionalmente, embora a perda mineral tenha sido semelhante para BC e CC na simulação de espessura de placa de até 0,5 mm, ela foi maior para BC na placa mais espessa (1 a 1,5 mm) (p<0,05). Os resultados sugerem que o dentifrício de concentração convencional é mais efetivo do que o de baixa concentração na inibição da perda mineral. Adicionalmente, deve-se estimular o enxágüe da boca após o uso do dentifrício de concentração convencional por crianças de pequena idade / Abstract: The anticaries efficiency of fluoride (F) dentifrices containing 1000-1500 µg F/g is well established, but they are considered a risk factor to dental fluorosis. In order to reduce this risk, low-F concentration dentifrices (500-550 µg F/g) have been recommended, but their anticaries efficiency has not been demonstrated. Thus, this study aimed to: 1. compare salivary F availability after brushing with low- F concentration (LC, 500 µg F/g, NaF) or conventional F concentration (CC, 1100 µg F/g, NaF) dentifrices, followed or not by a water rinse and 2: evaluate in situ the anticaries potential of these dentifrices, studying the anticaries effect of F available on the dental biofilm after brushing, associated or not to F products formed on enamel by F dentifrice application was evaluated. In both studies, a crossover, double blind design was used. In study 1, samples of non-stimulated saliva from 5 volunteers were collected before and immediately after brushing with LC or CC, followed or not by a rinse, and after 1, 2, 3, 4, 5, 10, 15, 20, 30, 45 and 60 min. The area under the curve of salivary F concentration versus time was calculated to determine F bioavailability in saliva. F salivary bioavailability was reduced 2.5 X by the post-brushing rinse (p<0.05) and it was similar when LC was used without rinsing and CC was used followed by a rinse (p>0.05). In study 2, twelve volunteers brushed with dentifrices containing distinct F concentrations (placebo (P) ¿ negative control, LC or CC) and used a palatal appliance containing bovine enamel blocks previously treated or not with a slurry of assigned dentifrice. The blocks were covered with a test plaque from S. mutans IB 1600 and after 30 min in situ, F concentration in the fluid of plaque was assessed. A sucrose rinse was performed as a cariogenic challenge and after 45 min the remaining blocks and plaque test were removed to evaluate, respectively, mineral loss (as a function of plaque thickness) and F concentration in plaque fluid. The isolated effect of the pretreatment of enamel blocks with F dentifrices did not reduced mineral loss when compared to the control (p>0.05), but resulted in higher F concentration in the plaque fluid (p<0.05). Brushing with F dentifrices increased F concentration in the plaque fluid, which was significantly different between LC and CC (p<0.05), and resulted in lower mineral loss when compared to the control (p<0.05). Additionally, although LC and CC did not differ when mineral loss was evaluated on a plaque thickness simulation of up to 0.5 mm, CC was more efficient than LC at thicker plaque (1 to 1.5 mm) (p<0.05). The results suggest that conventional F concentration dentifrice is more efficient than the low-F one in the inhibition of mineral loss. Additionally, post-brushing rinse should be recommended after the use of conventional F concentration dentifrices by young children / Mestrado / Cariologia / Mestre em Odontologia