General Information: The commensal bacterium Streptococcus salivarius is predominant specie of the human oropharyngeal tract and exerts an important role in oral ecology. Streptococcus salivarius is an aerobic, gram-positive coccus. This organism is the most common organism isolated from the human oral cavity. Streptococcus salivarius can also be an opportunistic pathogen causing endocarditis, blood infection, and peritonitis. Streptococci are Gram-positive, nonmotile, nonsporeforming, catalase-negative cocci that occur in pairs or chains. Members of this genus vary widely in pathogenic potential. Most streptococci are facultative anaerobes, and some are obligate anaerobes.