Potencial cariogenico "in vitro" de estreptococos grupo mutans da cavidade bucal e seu significado em relação a carie dentaria

AUTOR(ES)
DATA DE PUBLICAÇÃO

1998

RESUMO

In order to analyze the cariogenic potential of some group mutans streptococci species, isolated and in association, by formation of "in vitro" bacterial plaque, production of extracellular polysaccharides and acid production capacity, strains of those microorganisms belonging to the microbial collection of Microbiology and Immunology Laboratory, Dental School of Piracicaba - UNICAMP, were isolated from saliva samples of students aged 6-9 years old from different socioeconomic categories and biochemically identified. One hundred fifty strains of S. mutans, 27 of S. sobrinus, 15 of S. rattus, 09 of S. mutans V and just one of S. cricetus, S. ferus and S. Downei totalizing 204 samples, were analyzed. The quantifications of "in vitro" production of bacterial plaque, for the isolated and in association streptococci,nwere done by inoculation of similar accounts of recent cultures from each, sample previously standardized by tube 2 of Mc Farland s scale, in tubes withnBHI medi um supplied with 5% of sucrose and incubated for 48 hours (37 `DEGREE´ C / 10% `CO IND. 2´). In each pre-weighed tube a stick-capillary was added facilitating, by this way, the determination of "in vitro" plaque production. The acid production capacity for the samples of group mutans streptococci - isolated and in association - was demonstrated by continuous mensurations of BHI - 5% sucrose culture medium pH, in increasing intervals of time (6, 12, 24 and 48 hours after inoculation). The production of extracellular polysaccharides was determinated by dosage method of total acid and alkali soluble carbohydrates. The results showed that among the analyzed samples, S. rattus (19.70 mg) followed by S. mutans / S. sobrinus association (10.32 mg) produced larger amounts of "in vitro" bacterial plaque, demonstrating by this parameter, great cariogenic potential. The S. mutans species (6.89 `mu´g/mg) and S. Sobrinus species (5.12 `mu´g/mg), separately, presented the largest production of acid soluble carbohydrates per mg of "in vitro" bacterial plaque. In relation to the production of alkali soluble carbohydrate, the S. mutans (6.62 `mu´g/mg) was statistically superior to the other species, isolated and in association. Those data confirm the high cariogenic potential of this species when considering the important role of those components in the bacterial plaque formation. The determination of acid production by streptococci strains, revealed accentuated pH falls in the intervals of initial and final time, with values of 4.67 (for 6 hours) and 3.86 (for 48 hours) respectively, for the S. Mutans species. For the period of 12 hours, the S. sobrinus species produced the greatest pH fall (4.34), and for 24 hours the smallest value found belonged to S. mutans V species (3.58).This condition favors the prolonged maintenance of pH below the criticaI levels (pH 5.0), corroborating the suggestion that multicolonized individuais present higher indexes of dental decay. The statistical analysis of correlation among the several studied virulence factors demonstrated variable correlations depending on the incubation period and on the group mutans streptococci strains (isolated or in association). Such fact does not indicate, according with the conditions of this research, a constant and uniform correlation among those factors

ASSUNTO(S)

acidos caries dentarias polissacarideos placas dentarias estreptococo

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