Comparison of Cariogenic Characteristics between Fluoride-sensitive and Fluoride-resistant Streptococcus mutans

Abstract

The aim of this study is to compare cariogenic characteristics of fluoride-sensitive <i>Streptococcus mutans</i> [fluoride-sensitive (FS) <i>S. mutans</i> ] and fluoride-resistant <i>Streptococcus mutans</i> [fluoride-resistant (FR) <i>S. mutans</i>] in the presence of sucrose, and to evaluate its effect on cariogenic biofilm formation. <i>S. mutans</i> ATCC 25175 was continuously cultured in trypticase soy broth (TSB) containing NaF (70 ppm) for 40 days to generate FR <i>S. mutans</i> . FS and FR <i>S. mutans</i> were inoculated in TSB with or without 2% sucrose, and optical density and pH were measured every hour. An oral biofilm was formed using saliva bacteria and analyzed through confocal laser scanning microscopy and CFU count. Finally, the expression of glucosyltransferases genes of both <i>S. mutans</i> was investigated through RT-PCR. FR <i>S. mutans</i> exhibited slower growth and lower acidogenicity in the presence of sucrose compared to FS <i>S. mutans</i> . Both cariogenic and single species biofilm formation was lower in the presence of FR <i>S. mutans</i> , along with reduced number of bacteria. FR <i>S. mutans</i> showed significantly low levels of gtfB, gtfC, and gtfD expression compared to FS <i>S. mutans</i> . On the basis of results, FR <i>S. mutans</i> may be less virulent in the induction of dental caries.