Effect of Fluoride on Biofilm Formation of Streptococcus Mutans Fluoride-resistant Strains

doi:10.13701/j.cnki.kqyxyj.2019.06.009

Abstract

Abstract: Objective: To observe the in vitro film formation process of Streptococcus mutans fluoride-resistant strains and compare them with parental strains; and to investigate the effect of fluoride on the biofilm formation of fluoride-resistant strains. Methods: Streptococcus mutans fluoride-resistant strain and parental strain were divided into parental group (Streptococcus mutans parental strain grown in fluorine-free BHI medium), fluoride-resistant group (fluorine-resistant strain grown in fluorine-free BHI medium), and fluorine-containing group (the fluoride-resistant strain was grown in BHI medium having a fluorine content of 1 g/L). The biofilm formation of three groups at 6h, 12h, 18h, 24h, 36h, and 48h was observed by crystal violet staining, scanning electron microscopy, and laser confocal microscopy. The statistical analysis was performed by SPSS 21.0 one-way analysis of variance. Results: (1) The biofilm biomass was observed to increase with time by crystal violet staining, which reached the maximum at 24-36 h and was relatively stable. There was no significant difference in biofilm biomass between the parental group and the fluoride-tolerant group (P>0.05). The biomass of the fluoride group was significantly less than the fluoride-resistant group at the six time points (P<0.05). (2) Scanning electron microscopy showed that the structure of biofilm became more complicated with the increase of time, and the fluorine-containing group did not form a complete biofilm during the experimental time. (3) The laser confocal experiment showed that the biofilm showed green fluorescence at 6h-24h through live bacterial death, and the biofilm was mainly composed of 36h-48h biofilm, which was mainly yellow. There were significant statistical differences in bacterial density and viable ratio between the experimental groups at different time points (P<0.01). Conclusion: There is no significant difference in the in vitro formation of fluoride-resistant strains and parental strains of Streptococcus mutans. Fluoride has a significant inhibitory effect on the formation of biofilms resistant to fluoride. This experiment lays the foundation for the research of the follow-up drugs on the prevention and treatment of biofilm and the study of metabolomics.

Key words: Streptococcus mutans, Streptococcus mutans fluoride-resistant strain, Bacterial biofilm

YANG Yao-yao, ZHANG Zhi-min, ZHAO Hong-yan, GUO Xin-wei, LIU Lu, LING Xiao-xu, QU Tian. Effect of Fluoride on Biofilm Formation of Streptococcus Mutans Fluoride-resistant Strains[J]. Journal of Oral Science Research, 2019, 35(6): 546-550.

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