Rhamnus prinoides (gesho) stem extract prevents co-culture biofilm formation by Streptococcus mutans and Candida albicans.

Streptococcus mutans and Candida albicans exhibit a symbiotic relationship to form polymicrobial biofilms that exacerbate oral infections including early-childhood caries, periodontitis and candidiasis. Rhamnus prinoides (gesho) has traditionally been used for the treatment of a variety of illnesses and was recently found to inhibit Gram positive bacterial biofilm formation. We hypothesized that Rhamnus prinoides extracts have anti-biofilm activity against S. mutans and C. albicans mono- and dual-species biofilms. Ethanol extracts were prepared from gesho stems and leaves then anti-biofilm activity was assessed using crystal violet, resazurin and XTT staining. Ethanol extracts significantly inhibited Streptococcus mutans and Candida albicans mono-species biofilm formation up to 97% and 75%, respectively. The stem ethanol extract disrupted S. mutans and C. albicans co-culture synergism with 98% less polymicrobial biofilm formation than the untreated control. Additionally, this extract inhibited planktonic S. mutans cell growth and decreased biofilm polysaccharide production up to 99%. The reduction in polysaccharide production is likely a contributing factor in the anti-biofilm activity of GSE. These findings indicate that gesho or gesho-derived compounds may have potential as additives to oral hygiene products.