Cryptotanshinone ameliorates the pathogenicity of Streptococcus suis by targeting suilysin and inflammation

Aims: Streptococcus suis is a highly zoonotic pathogen that is a serious threat to human health and the development of the pig industry worldwide. The virulence factors produced during S. suis infection play an important role, and the pore-forming activity of suilysin is considered an important virulence-related factor, especially in meningitis. Treatment of S. suis infection with traditional antibiotics is becoming increasingly challenging due to bacterial resistance. The purpose of this study is to verify the role of cryptotanshinone in the process of Streptococcus suis infection and provide a new drug precursor for the treatment of S. suis infection.

Methods and results: In this study, we used circular dichroism spectroscopy to demonstrate that cryptotanshinone alters the secondary structure of suilysin. The results of the antibacterial activity and hemolysis assays showed cryptotanshinone could inhibit the pore-forming activity of suilysin without affecting bacterial growth or its expression. We also showed that cryptotanshinone reduces bacterial damage and penetration in vitro, reduce the S. suis-induced inflammatory response and provide protection against bacterial infections in vivo and in vitro.

Conclusions: Cryptotanshinone is a potential compound precursor for treating S. suis infection.

Significance and impact of the study: Cryptotanshinone may be a promising leading compound for S. suis infection and related diseases.

Keywords: Streptococcus suis; anti-infection; bacterial resistance; cryptotanshinone; suilysin.