Table II.Control specification of Fedegari and Steris resistometers.
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Fraction negative.
In each resistometer, D 121-values were determined (in triplicate) on the spore-strip BIs. In the Fedegari resistometer, D 124 and D 129-values were determined (in triplicate) on the spore-strip BIs.
In each resistometer, D-values were determined (in triplicate) at three temperatures using self-contained and ampul BIs. All fraction-negative data
were collected according to ISO 11138 (2). The fraction-negative method involves subjecting the BIs to a series of incremental
exposure times followed by assay testing for growth or no growth. Using these data, Z-values were calculated. Testing was
as follows:
- BI lot S1—D 121-value determined in triplicate in each of the three resistometers
- BI lot S1—D 124 and D 129-values determined in triplicate in Fedegari resistometer
- BI lot SC1—D 121, D 124, and D 127-values determined in triplicate in each of the three resistometers
- BI lot SC2—D 121, D 124, and D 127-value determined in triplicate in each of the three resistometers
- BI lot SC3—D 121-value determined in Fedegari resistometer
- BI lot SC4—D 121-value determined in Fedegari resistometer
- BI lot A1—D 121, D 124, and D 129-values determined in triplicate in each of the three resistometers.
Figure 6
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Exposures above 129 °C were not performed. Although the resistometers are capable of operation above this temperature, ISO
11138 states that for Z-value calculation, temperatures "in the range of 110 °C to 130 °C" shall be used.
Results
Figure 7
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Parametric analysis of resistometers.
The control accuracy of each resistometer is listed in Table II, along with the ISO specifications. Although there were a
few minor deviations from the standard (e.g., temperature and pressure range), all three resistometers were within specifications.
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