- The research has collected 20 kinds of bacteria belonging 4 species: Streptococcus spp, Veillonella spp, Neisseria spp, Haemophilus spp There are 4 popular species, including: Streptococcus salivarius (40%), Veillonella sp (30%), Streptococcus parasanguinis (23, 33%), Streptococcus oralis (20%).