Evaluation of phenotypic traits of cariogenicity of Strptococcus Mutans genotypes isolated from dental biofilm / Avaliação de caracteristicas fenotipicas de cariogenicidade de genotipos de Strptococcus Mutans isolados de biofilme dental

AUTOR(ES)
DATA DE PUBLICAÇÃO

2010

RESUMO

Mutans streptococci, mainly Streptococcus mutans, are considered as the main microorganisms related to dental caries. These microorganisms are present in oral cavity as distinct genotypes, which may show distinct phenotypic traits. In this context, it was evaluated the S. mutans genotypic diversity in dental biofilm formed in vivo and in situ during 3 days under controlled exposure to sucrose, the most carigenic carbohydrate, and its monosaccharides constituents (glucose and fructose). Distinct S. mutans genotypes were found under these before mentioned conditions, but no selection of them was found in dental biofilms formed. Moreover, the virulence phenotypic traits of these genotypes were not evaluated. Thus, it would be important to evaluate in these genotypes previously isolated from dental biofilm formed in vivo and in situ in the presence or absence of sucrose, the phenotypic traits of cariogenicity related to aciduricity and acidogenicity in order to investigate the relationship between a high cariogenic challenge (frequent exposure to sucrose and biofilm accumulation) and their virulence. Either in those genotypes isolated from in vivo dental biofilms, or in those isolated from in situ dental biofilms, the acidogenicity trait was evaluated through counts of viable cells in acid conditions and F-ATPase activity, and the acidogenicity trait was evaluated through the ability to lower the pH due to glycolysis. Besides, eight genotypes previously isolated from in situ dental biofilms formed during three days were grown as in vitro biofilms, and these genotypes were evaluated regarding their acidogenicity, cariogenic potential and ability to synthesize extracellular polysaccharides. In relation to genotypes isolated from in vivo biofilms, those isolated from biofilms formed in the presence of sucrose were more acid-tolerant, either at pH 5.0 or at pH 2.8, and more acidogenic, since they showed lower values of final pH during the evaluation of the curve of pH fall and also higher ability to produce acids in the first 15 minutes of glucose fermentation, than genotypes isolated from in vivo biofilms formed in the absence of sucrose. Besides, no expressive differences regarding F-ATPase activity between these two distinct conditions were found. Genotypes found only in the presence of sucrose were more acidogenic than those found only in the absence of this carbohydrate. Similar data were found for genotypes isolated from in situ dental biofilms formed in the presence of sucrose, which were more aciduric and more acidogenic than genotypes isolated from biofilms formed in the absence of this carbohydrate. In in vitro biofilm model, no differences either in the acidogenicity or in the ability of genotypes to synthesize extracellular polyssacharide were found. However, the S. mutans genotypes showed distinct cariogenic potential, independent of the fact that these genotypes had been isolated in the presence or absence of a high cariogenic challenge. The results suggest that frequent pH fall due to sucrose exposure may select more virulent S. mutans genotypes. Besides, distinct S. mutans genotypes may show distinct cariogenic potential.

ASSUNTO(S)

microbiology placa dentaria virulencia virulence microbiologia dental plaque

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