[Inhibitory Effects of Nicotinamide on Growth and Biofilm Formation].

Objective: To explore the effects of nicotinamide (NAM) on the growth, biofilm formation and exopolysaccharides (EPS) production of .

Methods: The minimum inhibitory concentration (MIC) of NAM on was 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 under different NAM concentrations were drawn. Crystal violet assay and anthrone-sulfuric acid method were used to explore the effects of NAM on biofilm formation and water-insoluble EPS production, respectively. The morphology and structure of planktons and biofilms after NAM treatment were observed by scanning electron microscopy.

Results: The MIC of NAM on 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, 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 (<0.05). Under scanning electron microscope, the cell length of 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 (<0.05).

Conclusion: Under the influence of NAM at certain concenrations, the growth, biofilm formation, and EPS synthesis of were inhibited.