Pathogenomic Studies of Streptococcus sanguinis in Infective Endocarditis

Background: Infective endocarditis (IE) is a type of endovascular infection caused by bacteria in the bloodstream which get adhered to the damaged heart valve. IE has extensively been associated with oral hygiene, as onset of bacteremia has been observed more often in dental patients. Furthermore, few members of oral microbiota including certain strains of Streptococcus sanguinis have also been isolated from IE colonies. Streptococcus sanguinis is a large group of infectious bacteria including human pathogenic strains. S. sanguinis SK36 is a member of microflora of human mouth and is an opportunistic pathogen of dental plaques. Various other strains of S. sanguinis also constitute human mouth microflora, and have the potential to cause dental plaques, therefore, a possibility is there that they too might have a role in the onset of IE. Objective: In this study, we aim to investigate the possible role of all known strains of S. sanguinis in the onset of IE and cluster them accordingly. Method: To achieve this, 31 strains of S. sanguinis were investigated and clustered into two groups i.e. Pathogenic and Non-Pathogenic. We further divided the pathogenic cluster into two sub-clusters; moderate and severe pathogens, based on their distance from the reference strain and degree of significance of the virulence determinants they possess. 22 virulence determinants were enlisted by literature survey and revealed association with IE. Results: Based on our investigations, we clustered 16 out of 31 strains as pathogenic (4 severe and 12 moderate) and rest of 15 as non-pathogenic of IE. Conclusion: It is concluded that not only SK36 and VMC66 but 14 other strains of S. sanguinis also have the potential to cause IE and there is dire need to conduct a comprehensive study to find out their relationship with IE.