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  • Title: Thermal resistance of Bacillus stearothermophilus spores on strips previously treated with calcium.
    Author: Penna TC, Machoshvili IA, Taqueda ME.
    Journal: PDA J Pharm Sci Technol; 1996; 50(4):227-37. PubMed ID: 8810838.
    Abstract:
    Moist thermal resistance parameters of spores of B. stearothermophilus ATCC 7953, inoculated in aqueous suspensions and on strips, were evaluated at 118 degrees C and 121 degrees C, by the proposed serum-bottle-mini-autoclave method. The present work studied the effect of alkaline calcium exchange-inducing storage treatments on the viability and moist heat-resistance of B. stearothermophilus spores, stored at -18 degrees C, following impregnation into filter paper strips which had been previously treated by immersion in alkaline 0.02 M calcium acetate. The thermal resistance of B. stearothermophilus spores on strip at set work conditions as biological indicator exhibited an average medium D (121 degrees C) of 1.92 min for concentrations of 10(5)-10(6) spores per strip over 360 days of storage in a freezer. The serum-bottle-mini-autoclave measuring system resulted in reasonably accurate and reproducible BIs calibration, before using them in an equipment validation program. The calcium acetate-strip system demonstrated a very high stability (Ea = 49.95 kcal/mol) to keep the spore viability and thermoresistance over steam cycles and storage. The heat activation kinetics of spores were also studied.
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