Tryptone Yeast Extract Cystine w/ Sucrose and w/o Bacitracin Agar (TYCSB) is recommended for selective isolation of Streptococcus mutans.Tryptone and yeast extract in the medium provide nutrients essential for the growth of Streptococci. Sodium sulphite, sodium acetate, disodium phosphate, and sodium bicarbonate are sources of ions that simulate metabolism.