The growth medium has been developed to incubate Geobacillus stearothermophilus spores (# 7953) to easily monitor growth. After sterilization the spores, e.g. spore strips are aseptically transferred into the growth medium on a sterile bench and incubated at 55 - 60°C afterwards.

The medium contains a pH-indicator that shows bacteria growth quicker than conventional media. If not all spores were inactivated during the sterilization process, the germs replicate and produce acids. The resulting pH changes the colour of the liquid from purple to yellow-green.