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

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. SIGNIFICANCE AND IMPACT OF THE STUDY: Oral Streptococcus mutans and Candida albicans biofilms are associated with a variety of illnesses. When occurring together, the resulting infections are especially challenging to treat due to enhanced biofilm formation and antibiotic resistance. More therapeutics that can effectively prevent polymicrobial biofilm formation and disrupt interspecies synergism are needed. Rhamnus prinoides ethanol extracts significantly inhibited dual-species biofilm formation and disrupted interspecies synergism.