In this study, the effect of sugars type (glucose, sucrose, fructose and the mixture of glucose and fructose) and best substrate concentration are investigated on biofilm accumulation. Then, the role of this substrate examined on gtfB expression level by real time RT PCR. A total of 40 Streptococci strains isolated from dental caries and plaque of patients. The ability of them to form biofilm measured in the presence of some sugars on micro titer plates. The mean of resulted optical density of formed biofilm in the presence of sucrose was higher than other carbohydrates significantly (p < 0.05). In the next step biofilm formation of best Streptococcus mutans isolates monitored at time intervals and revealed that the number of attached bacteria increased with the increase of sucrose concentration. The results corresponded to a non linear increase of attached bacteria. The line of best fit for the calibration of the attached bacteria versus sucrose concentration required a 3rd-order polynomial (R2=1). The comparison between the mRNA level of gtfB in planktonic, biofilm and unattached cells of S. mutans by real time RT PCR showed that, the level of gtfB gene expression in the biofilm condition was significantly higher than the planktonic condition.
Key words: Biofilm formation, carbohydrate, gene expression, oral streptococci.
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