[Inhibitory Effects of Nicotinamide on Streptococcus mutans Growth and Biofilm Formation]
Yong-Wang Lin1, Mei-Ling Jing1, Yu-Qing Li1
1State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, China.
Objective:
To explore the effects of nicotinamide (NAM) on the growth, biofilm formation and exopolysaccharides (EPS) production of Streptococcus mutans.
Methods:
The minimum inhibitory concentration (MIC) of NAM on S. mutanswas determined by the planktonic bacterial susceptibility assay. The NAM mass concentrations were set as 1/2 MIC, 1/4 MIC and 1/8 MIC for hree separate treatment groups. Culture medium without NAM was used in the negative control group and culture medium containing 0.1 mg/mL NaF was used for the positive control group (except for the scanning electron microscopy). The growth curves of S. mutans under different NAM concentrations were drawn. Crystal violet assay and anthrone-sulfuric acid method were used to explore the effects of NAM on S. mutans biofilm formation and water-insoluble EPS production, respectively. The morphology and structure of S. mutansplanktons and biofilms after NAM treatment were observed by scanning electron microscopy.
Results:
The MIC of NAM on S. mutans was 32 μg/μL. After 16 μg/μL (1/2 MIC), 8 μg/μL (1/4 MIC) and 4 μg/μL (1/8 MIC) NAM treatments, S. mutans growth and biofilm formation were inhibited, with the 16 μg/μL NAM group displaying the most significant inhibitory effects. The synthesis of EPS decreased significantly in the 16 μg/μL and 8 μg/μL NAM groups in comparison with that of the negative control group (P<0.05). Under scanning electron microscope, the cell length of S. mutans was shortened, the cell width was extended, and the length/width ratio was decreased, showing significant difference when comparing the 16 μg/μL and 8 μg/μL NAM groups with the negative control group (P<0.05).
Conclusion:
Under the influence of NAM at certain concenrations, the growth, biofilm formation, and EPS synthesis of S. mutanswere inhibited.
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