Poster Presentation Lancefield International Symposium for Streptococci and Streptococcal Diseases 2025

The stabilization of streptolysin S secreted from β-hemolytic streptococci in the presence of human serum albumin. (#268)

Shuto Yokohata 1 , Kazuto Ohkura 2 , Hideaki Nagamune 3 , Toshifumi Tomoyasu 1 3 , Atsushi Tabata 1 3
  1. Division of Bioresource Science, Graduate School of Sciences and Technology for Innovation, Tokushima University Graduate School, Tokushima, Japan
  2. Division of Clinical Pharmacy and Pharmaceutical Sciences, Graduate School of Pharmaceutical Sciences, Suzuka University of Medical Science, Suzuka, Mie, Japan
  3. Department of Bioengineering, Division of Bioscience and Bioindustry, Graduate School of Technology, Industrial and Social Sciences, Tokushima University Graduate School, Tokushima, Japan

[Background] The strains belonging to anginosus group streptococci except for Streptococcus intermedius produce streptolysin S (SLS) as the sole factor for β-hemolysis, and the SLS plays an important role in damaging host cells. Because oral streptococci could translocate into the bloodstream following such as periodontal disease, the SLS-dependent cytotoxicity of β-hemolytic streptococci was investigated focusing on the cause of ectopic growth such as in the bloodstream.

[Methods] Streptococcus anginosus subsp. anginosus (SAA) strain NCTC10713T and their mutants for sagA gene(s) were cultivated in the presence or absence of the blood component, and both SLS-dependent hemolytic activity and cytotoxicity were investigated using the prepared culture supernatant. The expression of sagA genes in NCTC10713T was also investigated by quantitative RT-PCR.

[Results & Discussion] The hemolytic activity of SLS secreted into their culture supernatants was stabilized in the presence of serum, and the most effective component was human serum albumin (HSA). According to the result of RT-PCR, the transcription of sagA genes was observed even in the condition absent of HSA showing no hemolysis by the culture supernatant. These results strongly suggest that the secreted SLS into the extracellular milieu will be stabilized in the presence of HSA.

[Conclusion] In this study, the stabilized hemolytic activity of the SLS secreted from the SLS‐producing streptococci was observed in the presence of HSA. This result provides the insight into the risk of SLS‐producing streptococci which can translocate into the bloodstream.