Andrewes & Horder 1906
Streptococcus salivarius is a species of spherical, Gram-positive bacteria which colonize the mouth and upper respiratory tract of humans a few hours after birth, making further exposure to the bacteria harmless. The bacteria is considered an opportunistic pathogen, rarely finding its way into the bloodstream, where it has been implicated in septicemia cases in people with neutropenia. 
Streptococcus thermophilus, a member of the salivarius group, is a streptococcus bacteria used to produce yogurt and some cheeses. It works symbiotically with Lactobacillus delbrueckii subsp. bulgaricus. Both are homofermentative, produce lactic acid quantitatively in addition to carbon dioxide and alcohol. The optimum temperature of growth for S. thermophilus is 42°C while it is 37°C for S. salivarius.