cont'd

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Obtain a minimum of 300 biological indicators. One hundred (100) biological indicators should be from each of 3 separate lots.

Using the predefined sterilization parameters, expose the biological indicators in 3 partial sterilization cycles (100 per partial cycle). Each of the test cycles will have 30% to 80% of the indicators surviving (i.e., test positive).

A partial cycle is one in which all sterilization parameters, except the time parameter, are met. The exposure time is much shorter than the standard sterilization cycle.

Only the biological indicators from one lot are to be used in each partial cycle. Do not mix biological indicators from different lots.

It is preferable to run biological indicators in a device load. However, the inherent difficulties of achieving a partial cycle kill under such circumstances are understood. Thus, partial cycles can be run without device loads.

NOTE: During all sterilization validation studies, consider the effects of the sterilant in combination with the device material on the indicator organism. If the materials are judged to have a significant effect on organism destruction, the biological indicators should be exposed to the sterilant in conjunction with the devices during the partial cycle studies.

If there are fewer than 30% survivors or more than 80% survivors in any one run, this particular run is invalid and should be rerun to achieve the desired number of survivors.

Three partial cycles are the minimum number of testing cycles to be run. If the results of any one cycle are invalid, another partial cycle should be substituted for it.

After exposure incubate the BIs for a minimum of 7 days. Place the BIs in the growth media no more than 8 hours after removal from the sterilization chamber or removal from the sterilized load of devices. Record the number of positive BIs on either a daily basis or for the particular time interval of interest.

Using the number of Bls that test positive on day 7 as the base of 100% grow out (denominator data), determine from the growth chart if the required number of BIs have grown out (numerator data) in the time interval in question. More than 97% of the base number of BIs should test positive in each partial cycle for the proposed incubation time to be acceptable.

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