ISO 11138-3:2017

Overview

ISO 11138-3:2017 - "Sterilization of health care products - Biological indicators - Part 3" specifies technical requirements and test methods for biological indicators used to assess moist heat sterilization (defined as dry saturated steam) of health care products. The standard covers production, labeling, test organisms, inoculated carriers, resistance determination and performance criteria used for validation and routine monitoring of steam sterilization processes.

Keywords: ISO 11138-3:2017, biological indicators, moist heat sterilization, steam sterilization, sterilization validation

Key topics and technical requirements

• Test organisms: Spores of Geobacillus stearothermophilus (or other microorganisms of demonstrated equivalent performance). Alternative organisms require demonstrated suitability for resistance.
• Resistance metrics: Resistance is expressed as the D value (minutes at 121 °C). Each batch/lot D value must be reported to one decimal place. Suspensions or indicators containing G. stearothermophilus shall have a D value ≥ 1.5 min (tested per Annex A).
• Thermal resistance characterization: The z value (temperature change for tenfold D change) must be calculated from D values at not less than three temperatures within 110 °C–138 °C; the z value shall be ≥ 6 °C. Annex B describes regression and coefficient of determination (r) calculations.
• Test methods: Annex A specifies a resistometer test procedure (see ISO 18472 for resistometer parameters) including chamber evacuation, steam admission, exposure and recovery steps.
• Carrier & packaging suitability: Manufacturer must demonstrate carrier/primary packaging compatibility under defined exposure conditions (e.g., exposure time ≥ 30 min, maximum temperature default 140 °C if unspecified, minimum exposure temperature ≥ 5 °C above manufacturer’s stated maximum).
• Population reporting: Viable counts and population/resistance characteristics must be stated using specified increments and formats (see Clause 9 and ISO 11138‑1 for general requirements).

Practical applications and users

ISO 11138-3:2017 is intended for:

• Manufacturers of biological indicators and inoculated carriers who need to specify production, labeling and performance claims.
• Sterilization engineers, validation specialists and QC laboratories performing sterilizer validation and routine monitoring of steam sterilization cycles.
• Regulatory and quality assurance professionals in healthcare, medical device manufacturers, hospital sterilization departments, and third‑party test labs.

Practical uses include establishing indicator D/z values, comparing batch-to-batch performance, and ensuring indicators provide a reliable challenge for steam sterilizers during validation and routine control.

Related standards

• ISO 11138-1:2017 - General requirements for biological indicators
• ISO 18472 - Test equipment (resistometer) for biological and chemical indicators
• ISO 17665 series - Validation and control of moist heat sterilization processes
• ISO 14161 - Selection, use and interpretation of biological indicators

This standard forms part of the ISO 11138 series and should be used alongside ISO 11138‑1 and ISO 17665 when planning validation and routine monitoring of moist heat (steam) sterilization processes.