Effect of roselle calyx extract on in vitro viability and biofilm formation ability of oral pathogenic bacteria

Objective: To investigate the effect of the roselle calyx extract(RCE)(Hibiscus sabdariffa L.) on the in vitro viability and biofilm formation ability of oral pathogenic bacteria. Methods:RCE was prepared by soaking roselle calyx powder with ethyl alcohol for 24 h at room temperature. After centrifugation, the extract was lyophilized. Then, the extract was dissolved in phosphate-buffered saline, the p H was adjusted, and the extract was aseptically filtered. We used Streptococcus mutans, Streptococcus sanguinis, Lactobacillus casei, Actinomyces naeslundii, Aggregatibacter actinomycetemcomitans, Fusobacterium nucleatum, Porphyromonas gingivalis and Prevotella intermedia in this study. The antibacterial activity of the RCE was determined by treating the cells of these bacteria with the extract for 10 or 20 min at room temperature. The minimum inhibitory concentration(MIC) and minimum bactericidal concentration was determined using the micro dilution method, and the effect of the RCE on the ability to form biofilm was determined using a polystyrene micro plate assay. In addition, we used the WST-1 assay to determine the cytotoxicity of the RCE on HGF, Ca9-22 and KB cells. Results: The RCE had antibacterial activity against oral bacteria used in this study. In particular, most significant antibacterial activity was observed against Fusobacterium nucleatum, Prevotella intermedia and Porphyromonas gingivalis. The MIC and minimum bactericidal concentration were 7.2 mg/m L–28.8 mg/m L and 14.4 to >57.6 mg/m L. The RCE had an inhibitory effect on biofilm formation at the MIC and sub-MIC levels. In addition, the RCE had low cytotoxic effects on HGF, Ca9-22 and KB cells. Conclusions: Thus, our results indicate that the RCE may be used for preventing oral diseases.

Characterization of the salivary microbiome in healthy Thai children

Objective: To investigate the composition of the salivary microbiome of 50 healthy Thai children. Methods: A total 76 provinces in Thailand are grouped into 5 geographical clusters based on unique economics, foods and lifestyles. Geographical locations and the results of an oral assessment were also considered. Genomic DNA was extracted from stimulated saliva samples. Subsequently, amplicon libraries were prepared by 16 S Metagenomic Sequencing Library Preparation. The amplicons were sequenced using an Illumina Miseq platform followed by bioinformatics and statistical analyses.Results: The correlation between oral hygiene status and caries history varied from r^2=0.887 to r^2=0.999 in the geographical groups, suggesting oral hygiene status a strong association between caries history. Twenty taxonomic groups were found in all subjects and constituted 93.6%-96.5% of the microbiome. Of these, genus Veillonella and Prevotella showed significant differences in their proportions between the geographical groups(P<0.05). Furthermore, the proportion of Veillonella parvula, as well as Rothia aeria and Rothia dentocariosa tended to increase with worse oral hygiene status, which was also related to higher dental caries history.Conclusions: The differences in the salivary microbiome as related to geographic regions suggest that environmental factors, which may include dietary habits, could influence the predominant bacteria found in the mouth of Thai children, especially the genus Veillonella and Prevotella. The ratio of Veillonella parvula, Rothia aeria and Rothia dentocariosa may be indicators of worse oral hygiene status and future caries in this population.