Plasmid Profile of Locally Isolated Streptococcus mutans in Relation with Mutacin Production

The present study was aimed to isolate and identify Streptococcus mutans from dental caries, and ability of bacterial isolates for mutacin production and selecting the efficient producer isolate and studying plasmid profile for the selected isolate and its role in mutacin production. In order to isolate Streptococcus mutans, 80 swab samples were collected from dental caries of patients attends Al-Dora health center and Al-Zewiya health center in Baghdad city. From these samples 80 bacterial isolates were obtained. Results of identification depending on morphological, cultural and biochemical tests showed that ten of these isolates were belonged to Streptococcus mutans, then results of identification were confirmed by using VITEK-II identification system. All isolates were screened to examine their ability in mutacin production. Plasmid profile of S. mutans S2 was studied to investigate its role in mutacin production. Results showed that S. mutans S2 has only one plasmid DNA band. This plasmid was not responsible for mutacin production according to the results of curing experiment by using interch alating ethidium bromide dye in a concentration of 800 ug/ml. Cured cells were still have the ability of mutacin production which indicated that this trait is chromosom ally encoded.