Growth medium of modified soybean casein digest broth provides nutrients for the incubation of bacteria spores. A pH indicator provides a distinct color change in the individual, sterilized tubes for easy-to-read indication of microbial growth. STERIS Spordex Culture Media is supplied in individual sterile screw-capped test tubes for easy use. It is intended to be used with Spordex and Spordi? Biological Indicator Strips, Discs, and Suspensions. Spordex Culture Media consists of a modified soybean casein digest broth and contains a pH indicator that provides an easy to read color change from red to yellow in the presence of microbial growth. This media is used to determine the D-value of each lot of STERIS Biological Indicators.