Rutin reduces the pathogenicity of Streptococcus agalactiae to tilapia by inhibiting the activity of sortase A

Streptococcus agalactiae can cause multiple infections both in human and animals. Treatment failure caused by antibiotic resistance, however, limits the application of antibiotics. Drugs based on novel strategies, therefore, are needed to fight bacterial infections. Sortase A (SrtA) anchoring surface proteins to the cell wall envelope plays a critical role in Gram-positive bacterial pathogenesis, suggesting that SrtA is a promising target for developing anti-virulence drugs. In this paper, we found that rutin without anti- S. agalactiae activity could reduce adhesion of S. agalactiae to fibronectin and biofilm formation by inhibiting SrtA activity in a dose-dependent manner. Moreover, rutin decreased the adhesion and invasion of S. agalactiae to A549 cells. In vivo study demonstrated that rutin could provide a significant protection against S. agalactiae infection in tilapia. The findings in the present study indicated that rutin is a potent anti-virulence agent against S. agalactiae infections via inhibiting SrtA activity.