Pneumococcus and Viridans streptococci

Viridans streptococci comprise a vast collection of Gram-positive commensal streptococcal bacteria that are hemolytic and produce a green hue on blood plates (hence the name “viridans”, from Latin “viridis”, green). The pseudo-taxonomic name “Streptococcus viridans” is often used to describe this species group, however, those who don’t prefer using the term “pseudotaxonomic” (which refers to a group of species as though they comprised one species) prefer to use the terms viridans streptococci, viridans streptococci group (VGS) or the viridans species of streptococcal. They do not possess Lancefield antigens. In general, the risk of pathogenicity is very low.