IS THERE ANY STANDARD REGARDING NUMBER OF BIOLOGICAL INDICATOR ONE MUST USE FOR STEAM AND ETO STERILIZER FOR A GIVEN CAPACITY OR VOLUME AND FREQUENCY OF USE.

MADHAV PAREKH
PHARMACONCEPT

Dear Madhav Parekh,
Per AAMI, for routine steam sterilization sterilization, a biological test must be run at least one time per week, but one time per day is preferred. Every load containing implantable devices (anything intended to be left inside the body for at least 30 days) must be monitored with a Biological Test.
After sterilizer relocation, malfunction, repair, or sterilization process failure, you want a minimum of three consecutive good biological tests before using the sterilizer for routine sterilization. If a sterilizer is used for several types of cycles, for example, High Vacuum, Gravity Displacement, and Liquids, each of the cycle types must be tested.

For EtO, every cycle must be monitored with a Biological Test.

Regards, Pete Bobb

Dear Madhav,

Pete describes the recommendations of the United States. In Europe it's slightly different what steam sterilization concerns.

A. Ethylene oxide sterilization
EN 550 defines the procedures for validation and routine control of ETO sterilization as follows:
6. Process control and monitoring
6.1 Data shall be recorded and retained for EACH sterilization load to demonstrate that the sterilization process specification has been met. These data include different physical parameters and also "the results of testing indicators for ethylene oxide sterilization". These indicators have to comply with EN 866-2: Biological systems for testing ethylene oxide sterilizers.
7. Product release from sterilization
7.1 Conventional release of product
7.1.1. The criteria for designating the sterilization process used for a particular sterilization load as conforming shall be documented. These criteria include:
a. conformity with the specified physical parameters for the sterilization cycle;
b. no growth of the test organism from any of the processed indicators for ETO sterilization following incubation.
7.2 Parametric release of a product (cycle monitoring without the use of biological indicators) is only applicable in industrial sterilization because it requires closely defined and validated sterilization loads and load configurations. The sterilization load and configuration should therefor be regarded as process parameters.

In a hospital setting, each ETO cycle must be monitored with biological indicators. EN 550 says about the number: The number of biological indicators for routine use should provide for sufficient indicators to be distributed throughout the sterilization load. A common qualification practice for routine microbiological monitoring is to use the following numbers of biological indicators:
1. for usable sterilizer chamber volumes of less than 5m³, at least 10
2. ...volumes between 5m³ and 10m³, the number of biological indicators should be increased by one for every additional 1m³;
3. ...volumes greater than 10m³, the number of biological indicators should be increased again by one for every additional 2m³.
The exact number of biological indicators selected for monitoring a defined sterilization process will be dependent upon the validation data obtained. BI should be located in those positions found during qualification to be the most difficult to sterilize, and the balance distributed uniformly throughout the sterilization load. Biological indicators should be placed in the sterilization load prior to preconditioning. BI should, whenever possible, be removed from the sterilization load and cultured as quickly as possible on completion of the cycle and prior to aeration. Any effects of delayed recovery, and in particular exposure to, residual ethylene oxide, should be determined.
Attention is drawn to the existence of national regulations existing in some countries on personnel exposure to ETO.

In hospital practise 1 BI per cycle should be sufficient. I refer also to question Q00027.

B. Steam sterilization
ISO 14161 says that BI may not be required and may provide little value in the routine monitoring of some sterilization processes (e.g. moist heat sterilization - after validation of the sterilization cycle). For processes where parametric release is not achievable BI provide the best available alternative for demonstrating microbial lethality in the sterilization process.

In the latter case I hold with Pete's recommendations (see also under question Q00027).

Kind regards,
Wim Renders