M17 Agar Base, Granulated is recommended for cultivation of lactic Streptococci and plaque assay of lactic bacteriophages.This medium is used for the cultivation and enumeration of lactic Streptococci and their bacteriophages. It is possible to study plaque morphology and lysogeny. it is recommended by the International Dairy Federation for selective enumeration and cultivation of Streptococcus thermophilus from yoghurt.