Effect Of Nicotine On Growth And Metabolism Of Streptococcus mutans

Objectives:   Streptococcus mutans is a key contributor to dental caries. Smokers have increased caries, but the association between tobacco, nicotine, caries and S. mutans growth is little investigated.

Methods: Seven S. mutans strains were used in the present study: UA159, UA130, 10449, A32-2, NG8, LM7, and OMZ175. The minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), minimum biofilm inhibitory concentration (MBIC), planktonic cell growth, biofilm formation, and biofilm metabolism of the seven strains treated with different concentrations of nicotine (0-32 mg/ml) were investigated.

Results: The MIC, MBC and MBIC were 16 mg/ml (0.1 M/ml), 32 mg/ml (0.2 M/ml), and 16 mg/ml (0.1 M/ml), respectively, for most of the S. mutans strains. Growth of planktonic S. mutans cells was significantly repressed by high nicotine concentrations (2.0-8.0 mg/ml), only strain A32-2 demonstrated enhancement at low nicotine concentrations (0.25-0.5 mg/ml). Biofilm formation and metabolic activity of S. mutans was increased in a nicotine-dependent manner up to 16.0 mg/ml.

Conclusions: Nicotine enhances S. mutans biofilm formation and biofilm metabolic activity. These results suggest smoking can increase the development of caries by fostering greater S. mutans biofilm formation on tooth surfaces.