Targeting of Oral Bacterial Taxa Linked to Disease by Flavonols

Networks of different bacterial taxa contribute to oral health. Antibacterials ideally would selectively modulate the subset of bacteria contributing to disease. Plant-derived natural compounds have been shown to inhibit planktonic bacteria or monospecies oral biofilms. However, very few in vivo studies are available to demonstrate the effects of these antimicrobials against native biofilms found in the human oral cavity. The objective of this study was to test putative antibacterials for their ability to affect specific bacterial taxa in complex biofilms.

Oral biofilms from donors were collected from saliva then rapidly prepared for polyphenol testing. They were then incubated with test polyphenols for 4 h. 16S rRNA was measured using NGS cDNA sequencing to determine potential targets of bacterial inhibition.

Two flavonols, kaempferol and quercetin, had small inhibitory effects on total RNA levels while myricetin at the higher concentration tested, 1 mM, showed substantial inhibition. Effects on the overall microbial population structure as evidenced by alpha diversity of the oral biofilm 16S rRNA were minimal. Remarkably, the flavonols specifically lowered rRNA levels of oral bacterial species associated with both periodontal disease and cardiovascular disease while sparing many commensal bacteria taxa.

In sum, plant-derived flavonols are a potential source of selective antimicrobial compounds against oral pathogens and bacteria that may contribute to systemic disease with minimal disruption of overall bacterial activity levels.