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Star Republic: Guide for Biologists

Autoclave spore test

Steam autoclaving at 121 C kills all bacteria including spores. To test the temperature, use a standard holding thermometer. Autoclave tapes are heat sensitive chemical indicators that change color after exposure to heat. They may be used to identify materials that have been processed through the heating cycle, but do not ensure adequacy of a sterilization cycle. Proper functioning of sterilization of the autoclave cycle should be verified by the periodic use of biological indicators (i.e., spore test).

1. Place a glass ampoule of Bacillus stearothermophilus spores in the center of a normal load.

2. Autoclave the load under normal operating procedures.

3. Incubate the ampoule according to manufacturer's instructions (usually incubate at 56 C for 48 hours).

4. If there is any change of color/appearance, the sterilization process has failed. If no color change has occurred, the sterilization process is adequate.