Comparative thermoresistance of two biological indicators for monitoring steam autoclaves. I. Comparison performed in a gravity BIER/Steam Vessel.

The thermoresistance of two biological indicators (BIs) for steam sterilization control (Swedish spore tablets and Attest No. 1242 BI) was compared at 121 degrees C and at 134 degrees C, saturated steam, in a special test autoclave (a gravity BIER/Steam Vessel). In this autoclave, three lots of Attest No. 1242 BI (ABI) demonstrated longer survival exposure times than did the three lots of the Scandinavian BI (SBI) tested while the survival-kill range was approx. the same. Also, the ABI had higher D121 degrees C- and D134 degrees C- values based on fraction-negative tests. The D121 degrees C-value of approx, 1.5 min as suggested by the European Pharmacopoeia, was met by both BIs. The larger spore population and the package configuration of the ABI units contribute to the higher thermoresistance of the ABI in the gravity BIER/Steam Vessel.