Betulin inhibits virulence and biofilm of Streptococcus pyogenes by suppressing ropB core regulon, sagA and dltA

Abstract

The present study demonstrates the antivirulence potential of betulin, an abundantly available triterpenoid against Streptococcus pyogenes, a multivirulent and exclusive human pathogen. Crystal violet assay and microscopic examination revealed that betulin (100 μg mL-1) exhibits surface-independent antibiofilm activity and mitigates extracellular polymeric substance production. Betulin treatment enhanced the rate of auto-aggregation in liquid medium. Results of real-time PCR and biochemical assays demonstrated that betulin suppresses the expression of ropB core regulon, sagA and dltA, which correspondingly affects SpeB production, hemolysis and cell surface hydrophobicity for the observed impairment in virulence and biofilm formation. dltA downregulation also affected the production of M protein, making betulin-treated cells more susceptible to phagocytosis. The non-toxic nature of betulin and its antivirulence potential against S. pyogenes were manifested in vivo in Caenorhabditis elegans. This study reveals the prospective role of betulin as therapeutic agent for the prevention and treatment of streptococcal infections.