ISO 11138-7:2019 pdf free download – Sterilization of health care products – Biological indicators – Part 7: Guidance for the selection, use and interpretation of results.
12 Culture conditions
12.1 General
12.1.1 Manufacturers of biological indicators are required by Iso 11138-1 to provide information to the user as to the culturing conditions (i.e. the time from the end of the sterilization process to the beginning of the incubation). If the user employs other culturing conditions, these should be validated by the user.
12.1.2 The procedures should be performed in a laboratory area defined for this purpose, giving proper attention to aseptic technique and good laboratory practice. It is good practice to include negative controls with each assay performed when using general laboratory areas for these assays. If a defined area cannot be found for this purpose, or if there is any risk of cross-contamination, the procedure should be performed in a defined critical zone (e.g. a sterile bench or biosafety cabinet with no air exchange between the critical zone and surrounding areas where biological indicators or microorganisms of the same or similar growth properties are being manufactured, packaged or otherwise handled).
12.1.3 Culture conditions recommended by the manufacturer of the biological indicator should be followed. If culture conditions other than those recommended by the manufacturer are employed, they should be validated to determine their effect on the performance of the biological indicator.
12.2 Incubation temperature
12.2.1 The labelling of the biological indicator should always be consulted with regard to the recommended incubation temperature. Failure to incubate biological indicators at the appropriate incubation temperature can invalidate the test results.
12.2.2 Test organisms that have been exposed to a sterilization process can exhibit increased sensitivity to variations in incubation temperature. Some test organisms can exhibit increased recovery at incubation temperatures below the recommended incubation temperature and decreased recovery at incubation temperatures above the recommended incubation temperature. In general, biological indicators of Geobacillus stearothermophilus can be incubated at temperatures in the range of 55 °C to 60 °C, and biological indicators of Bacillus atrophaeus can be incubated at temperatures in the range of
30 °C to 37 °C or according to the specifications provided by the manufacturer.
12.3 Incubation period
12.31 The incubation period required could vary with the nature of the biological indicator and sterilization process; ISO 11138-1:2017, Annex B recommends a period of 7 d for biological indicators for established processes. The labelling of the biological indicator and other information provided by the manufacturer should be consulted in this regard.
The incubation period information provided by the biological indicator manufacturer is validated using defined exposure and incubation conditions. The exposure conditions can vary from those in the user’s facility. Therefore, the user may consider verification of the biological indicator manufacturer’s recommendations for incubation time, based on the user’s quality policies and procedures.
12.3.2 For non-standard or new sterilization processes not covered by current International Standards, the incubation period should be validated against current national requirements; ISO 11138-1:2017, Annex B recommends an incubation period of 14 d.
12.3.3 A biological indicator manufacturer may validate a design of a spore carrier/recovery medium combination (e.g. a spore strip sold with recovery medium as a kit, or a self-contained biological indicator). The reduced incubation time validation for this product does not have to be repeated by the end user, as long as the end user uses the product with the same sterilizing agent as that used in the validation (e.g. design validated and used in ethylene oxide).