Cannabidiol and Cannabigerol Modulate Cariogenic Virulence in Cross-Kingdom Biofilms In Vitro

Introduction and aims The nonpsychoactive phytocannabinoids cannabidiol (CBD) and cannabigerol (CBG) have been increasingly recognized for their antimicrobial properties. However, their effect on Streptococcus mutans – Candida albicans dual-species biofilms, which exhibit enhanced cariogenicity, remains unclear. This study aimed to determine whether CBD and CBG suppress cariogenic traits in S. mutans–C. albicans biofilms and to identify CBD-responsive molecular pathways associated with biofilm virulence. Methods Planktonic assays and in vitro dual-species biofilm models of S. mutans and C. albicans were established. The effects of CBD and CBG on microbial viability, biofilm inhibition, mature biofilm disruption, acid production, and extracellular polysaccharide (EPS) production were assessed. CBD-associated transcriptional responses were analysed by RNA-seq and validated by qRT-PCR. Results Both CBD and CBG significantly inhibited S. mutans growth (minimum inhibitory concentrations, 2.5-5 µg/mL), suppressed dual-species biofilm formation, disrupted mature biofilms, and reduced acidogenesis and EPS production. In CBD-treated biofilms, transcriptomic analysis showed altered expression of S. mutans genes involved in membrane and envelope homeostasis, quorum-sensing-like competence, mutacin production, and metabolic pathways. While CBD had a limited impact on C. albicans viability in dual-species biofilms, it significantly altered the expression of virulence-related genes involved in central carbon metabolism, mannan biosynthesis, and stress responses. Conclusions CBD and CBG modulated the cariogenic traits in S. mutans – C. albicans dual-species biofilms, while CBD induced transcriptomic changes in pathways associated with biofilm fitness and virulence. These findings support further evaluation of phytocannabinoids as modulators of polymicrobial dental biofilm phenotypes and warrant further in vivo validation. Clinical relevance This study identifies nonpsychoactive phytocannabinoid-responsive phenotypes in cross-kingdom cariogenic biofilms and highlights their potential to modulate biofilm virulence. These findings provide a framework for further research into phytocannabinoids as oral biofilm modulators.