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Innovation in Biological Indicator Evaluator Resistometer Vessel Technology
The authors examine advances in the design and the application of biological indicator evaluator resistometer vessels used to measure the resistance of bacterial spores in monitoring sterilization processes.
Fedegari. During the insertion and removal of the BI cassette, a slight temperature drop in the chamber was recorded. The effect is
more pronounced when operating at higher temperatures, but in all cases, the temperature dropped no lower than the set point
minus 0.5 °C. The maximum and minimum temperatures recorded during a 121 °C and a 129 °C cycle are displayed in Figure 6.
Figure 7 displays the same 121 °C data at a higher resolution. These figures represent the typical performance of the resistometer.
Pressure readings in all cycles corresponded with the temperature readings, indicating that saturated steam was present in
the chamber.
Table III. Survivor-curve D-values collected in triplicate on spore strip lot S1.
Figure 9
Steris resistometers. Both Steris resistometers operated as described in the ISO standard. The temperature recording from a 121 °C cycle is shown
in Figure 8. Fedegari data from Figure 3 also are presented for comparison purposes.
Figure 10
Survivor curve: spore strip. Survivor-curve data collected on the spore-strip lot S1 are shown in Table III. In the Fedegari, D-values were calculated to be 2.7 min in all three trials. In the Steris resistometer, D-values ranged from 2.3 min to 2.8 min (see Figures 9 and 10).
Table IV. Fraction negative D-values collected on spore strip BI lot S1 in three resistometers.
Fraction negative: spore strip. Fraction-negative data collected on the spore strip lot S1 are presented in Table IV. In all three resistometers, D 121-values were 1.5 min.
James P. Agalloco is the president of Agalloco & Associates, P.O. Box
899, Belle Mead, NJ 08502, tel. 908.874.7558, jagalloco@aol.com.
Articles by James P. Agalloco
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