Streptococcus viridans is a large group of generally non-pathogenic Streptococcus that are all alpha hemolytic and produce a green (hence the name) coloration on blood agar. It is actually a misnomer as there is no Streptococcus with the species name of viridans. There are many species names for the viridans Streptococci. The organisms are most abundant in the mouth and one member of the group, S. mutans , is the etiologic agent of dental caries. Others may be involved in other mouth or gum infections. If they are introduced into the bloodstream they have the potential of causing endocarditis, particularly in individuals with damaged heart valves.

Site and Sources:

• Mouth
• Skin
• Nasopharynx
• Heart
• Oropharynx

The diagnosis can be done by letting it grow on blood agar.