ISO 11138-3: 2017 Sterilization of Health Care Products—Biological Indicators—Part 3: Biological Indicators for Moist Heat Sterilization Processes
This document specifies requirements for test organisms, suspensions, inoculated carriers, biological indicators and test methods intended for use in assessing the performance of sterilization processes employing moist heat as the sterilizing agent.NOTE 1 Requirements for validation and control of moist heat sterilization processes are provided by the ISO 17665 series.
Test Organism
The test organisms shall be spores of Geobacillus stearothermophilus or other strains of microorganism ofdemonstrated equivalent performance as required by this document.NOTE Bacillus stearothermophilus has been reclassified as Geobacillus stearothermophilus.If a test organism other than Geobacillus stearothermophilus or Bacillus subtilis ATCC 35021 (5230) is used, the suitability of the resistance of that test organism shall be determined.NOTE For processes at less than 121 °C, microorganisms such as Bacillus subtilis ATCC 35021 (5230) could be used, particularly in sterilization of heat-sensitive liquids.
Carrier and Primary Packaging
The suitability of the carrier and primary packaging materials for biological indicators for use in moist heatsterilization processes shall be demonstrated in accordance with the requirements of ISO 11138-1:2017.The exposure conditions to determine compliance shall be:- minimum exposure temperature: greater than or equal to 5 °C above the manufacturer's stated maximumexposure temperature- sterilizing agent: dry saturated steam; if the biological indicator is intended for use in a moist heat process notusing dry saturated steam, e.g. an air/steam mixture, the appropriate air steam mixture should be used andnoted as an exception to this document- maximum exposure temperature: as stated by the manufacturer; if not stated by the manufacturer, atemperature of 140 °C shall be used, and- exposure time: greater than or equal to 30 minNOTE These conditions have been selected to represent a realistic challenge to the carrier whileremaining within the practical limits of a moist heat sterilization process.
Population and Resistance
The manufacturer shall state the resistance characteristics in accordance with ISO 11138-1:2017The viable count shall be stated with increments less than or equal to 0,1 × 10n per unit (e.g. per ml ofsuspension, per inoculated carrier or per biological indicator).For inoculated carriers and biological indicators, the viable count shall be greater than or equal to 1,0 × 105.The resistance shall be expressed as the D value in minutes at 121 °C. Additional temperature(s) may beselected by the manufacturer. The D value of each batch/lot of biological indicators or inoculated carriers shall be stated in minutes to one decimal place at 121 °C.Suspensions, inoculated carriers or biological indicators containing Geobacillus stearothermophilus sporesshall have a D121 value of greater than or equal to 1,5 min when tested according to the conditions given in Annex A. Other microorganisms shall have D values supporting the application. The z value of the test organisms in the suspension, on the inoculated carrier or in the biological indicator shall be determined at not less than three temperatures, in the range of 110 °C to 138 °C. These data shall be used to calculate the z value, which shall be greater than or equal to 6 °C.The resistance characteristics specified in this document and any other part of ISO 11138 shall be definedusing the specific critical variables associated with the referenced sterilization process.D values are determined according to methods given in ISO 11138-1:2017Determination of D value and survival-kill response characteristics requires the use of a resistometer applying the reference resistometer process parametersThe survival-kill window can be calculated using the formulae in ISO 11138-1:2017, Annex E.NOTE This information can be of value to the user when comparing different batches from the same manufacturer.EXAMPLE Using the formulae in ISO 11138-1:2017, Annex E with the minimum population and minimum D value requirements specified in this document, the survival-kill response characteristics are:— at 121 °C: survival time greater than or equal to 4,5 min and kill time less than or equal to 13,5 min.
Annex A
Method for Determination of Resistance to Moist Heat Sterilization
Annex A - Principle
This method requires the use of a test apparatus referred to as a resistometer in this document. The specifications of the resistometer process parameters for moist heat sterilization processes are provided in ISO 18472.
Annex A - Procedure
Load the test samples on to suitable sample holders.Pre-heat the resistometer chamber to the required operating temperature, e.g. 121°C ± 0,5 °C.Place the loaded sample holders in the chamber, close the chamber and initiate the test cycle.Carry out the following sequence of operations: — Step 1: Evacuate the chamber to a set point of 4,5 kPa ± 1 kPa within 2 min— Step 2: Admit steam to the chamber to obtain the required temperature and pressure within 10 s. For the 0 minute exposure time, no steam shall be admitted.— Step 3: Maintain these conditions for the required exposure time.— Step 4: At the end of the exposure period, evacuate the chamber; then admit filtered air to ambient pressure. The time taken to achieve 100 kPa shall be 10 s or less.— Step 5: At the end of the above test cycle, remove the samples from the chamber, and cool down rapidly. Transfer the samples to the growth medium and incubate. The transfer period shall be documented and the same time period shall be used for all tests.
Annex B
Calculation of Z Value and Coefficient of Determination, r^2
Annex B - General
Using all the data obtained from either ISO 11138 1:2017, Annex C or ISO 11138-1:2017, Annex D, plot the log10 of the D value against exposure temperature in degrees Celsius. The z value is equal to the negative reciprocal of the slope of the best-fit rectilinear curve as determined by regression analysis.
Annex B - Formula for Slope of the Best-Fit Rectilinear Curve
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Annex B - Examples of Data Collected for Regression Analysis
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Annex B - Examples of Calculations for Slope
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Annex B - Examples of Calculations for Slope Cont.
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Annex B - Examples of Calculations for Slope Cont..
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