Overview
EN ISO 11138-2:2017 (CEN / ISO 11138-2:2017) defines requirements for biological indicators used to assess the performance of ethylene oxide (EO) sterilization processes for health care products. It covers test organisms, suspensions, inoculated carriers, biological indicators and test methods for EO sterilizers operating at sterilizing temperatures in the range 29 °C to 65 °C. This part of the ISO 11138 series is specifically focused on EO sterilization and complements the general requirements in ISO 11138-1.
Key topics and technical requirements
- Scope: Biological indicators and test methods for EO sterilization (pure EO or EO/diluent mixtures) at 29–65 °C.
- Test organisms: Primarily spores of Bacillus atrophaeus, Bacillus subtilis, or equivalent strains with demonstrated performance. (Examples of suitable Bacillus atrophaeus strains are listed in the standard.)
- Population: Inoculated carriers/biological indicators must have a viable count of at least 1.0 × 10^6 spores per unit.
- Resistance (D value):
- Resistance is expressed as the D value (minutes) at 54 °C, stated to one decimal place.
- For Bacillus atrophaeus spores, minimum D values specified:
- ≥ 2.5 min at 54 °C when tested with specified test gas mixtures (see Annex B).
- ≥ 2.0 min at 54 °C when tested with 100% EO test gas.
- Methods for D-value determination are provided in Annex A.
- Carrier and packaging suitability: Exposure conditions to challenge carriers include:
- Minimum exposure temperature ≥ 55 °C
- Ethylene oxide concentration ≥ 800 mg/L in air at ≥ 70% relative humidity
- Exposure time ≥ 6 hours
- Maximum exposure temperature as stated by the manufacturer
- Documentation: Manufacturers must state resistance characteristics and viable counts with specified increments.
Applications and users
- Intended for manufacturers and suppliers of biological indicators and inoculated carriers used for EO sterilization monitoring.
- Used by medical device manufacturers, sterile processing departments, hospital sterilization teams, test laboratories and regulatory bodies to:
- Validate EO sterilization cycles
- Monitor sterilizer performance and routine biological monitoring
- Specify and procure compliant biological indicators
- Supports quality assurance and process control in health care product sterilization using ethylene oxide gas.
Related standards
- ISO 11138-1 - General requirements for biological indicators
- ISO 11135 and ISO 14937 - Requirements for validation and control of EO sterilization processes
- ISO 14161 - Guidance on selection, use and interpretation of biological indicator results
Keywords: EN ISO 11138-2:2017, ethylene oxide sterilization, biological indicators, Bacillus atrophaeus, D value, sterilization validation, EO sterilizer performance.
