<prompt> Efficacy of Moist Heat Sterilization is tested by using the Spores ofBacillus stearothermophilusClostridium tetaniBacillus subtilisClostridium botulinum  <response>: A Bacillus stearothermophilus For determining the efficacy of moist heat sterilization, e.g. autoclaving, spores of Bacillus stearothermophilus are used as the test organism. This a thermophilic organism with an optimum growth temp. 55-60degC. Its spores are killed at 121 degC after 12 min exposure. 