Virulence modulation and biofilm inhibition of Streptococcus pyogenes by metabolites from endophytic fungi associated with Vanda tessellata.

BACKGROUND

Endophytic fungi represent a valuable source of bioactive metabolites with potential applications in addressing antimicrobial resistance. Biofilm formation by Streptococcus pyogenes contributes to antibiotic tolerance and persistent infections, highlighting the need for alternative anti-virulence strategies.

METHODS AND

RESULTS

In this study, endophytic fungi associated with the medicinal orchid Vanda tessellata were isolated and evaluated for their antimicrobial and antibiofilm activity against S. pyogenes using in vitro assays, microscopy, and viability analysis. Among the isolates, Nodulisporium verrucosum exhibited the strongest antibiofilm activity, achieving 90% inhibition at its minimum biofilm inhibitory concentration (MBIC) of 0.5 mg/mL, without affecting bacterial viability. Bioactivity-guided HR-LCMS analysis of the active extract revealed nine putative metabolites. Further computational ADMET profiling and molecular docking analyses identified tributyrin as a promising anti-virulence candidate, showing favorable pharmacokinetic properties and stable interactions with key biofilm-associated regulatory proteins of S. pyogenes. In addition, tributyrin demonstrated low cytotoxicity in mammalian cells.

CONCLUSION

These findings demonstrate the antibiofilm activity observed at the MBIC, along with the identification of tributyrin as a multi-target interacting compound, highlights the potential of V. tessellata-associated endophytic fungi as a promising source of anti-virulence agents. Together, this work provides a strong foundation for future molecular validation and in vivo evaluation of fungal-derived antibiofilm strategies.