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ISO 11138-1:2017 – General Requirements for Biological Indicators in Sterilization of Health Care Products
Understanding the Scope, Technical Specifications, and Implementation of the CAN/CSA-ISO 11138‑1‑17 Standard
Scope of ISO 11138-1:2017
ISO 11138-1:2017, adopted in Canada as CAN/CSA-ISO 11138-1-17, establishes the general requirements for biological indicators (BIs) used to assess the performance of sterilization processes for health care products. The standard applies to BIs intended for use with any sterilization modality (steam, ethylene oxide, dry heat, radiation, and others) and defines essential attributes for their design, manufacturing, performance testing, labeling, and storage. It is the foundational document in the ISO 11138 series, providing common specifications that are supplemented by method‑specific parts (e.g., ISO 11138-2 for ethylene oxide, ISO 11138-3 for moist heat). The scope includes BIs with inoculated carriers, as well as self‑contained BIs and BIs with defined culture media. Manufacturers, testing laboratories, and health care facilities use this standard to ensure consistent and reproducible sterility assurance.
Technical Requirements
Design and Construction
The standard mandates that each BI must be constructed with a carrier material that does not inhibit the viability of the test microorganism. The inoculum (typically bacterial spores) must be uniformly applied and demonstrate a known population per carrier (within a declared tolerance). For self‑contained BIs, the culture medium must be shown to support growth from a single viable spore. Primary packaging shall protect the BI from contamination and damage while maintaining stability throughout the labelled shelf life. The design also requires that users can safely handle and incubate the BI without cross‑contamination.
Performance Characteristics
ISO 11138-1 specifies that manufacturers shall determine the resistance characteristics of each BI batch, including the D‑value (time required to reduce the viable microorganism population by 90 % under defined conditions) and, where applicable, the z‑value (temperature dependence of the D‑value). These parameters must be reported per the relevant part of ISO 11138 for the sterilization method. Additionally, the standard defines survival and kill kinetics, stability after long‑term storage, and reproducibility across lots. Table 1 summarizes key performance requirements.
| Requirement | Specification per ISO 11138-1 |
|---|---|
| Microorganism identification | Confirmed to strain level, non‑pathogenic to users |
| Population per carrier | Declared value (e.g., 1.5 × 106 spores), with ≤ ±50 % tolerance |
| D‑value | Determined per method‑specific part; tolerance ≤ ±20 % of labelled value |
| Purity | No contaminating microorganisms detectable |
| Stability | Shall maintain label claim under stated storage conditions (temperature, humidity, light) |
| Growth promotion | Culture medium supports visible growth from ≤1 viable spore within 7 days |
Labeling and Documentation
Each BI unit and its packaging must clearly display: the microorganism species and strain, carrier population, type and batch of culture medium, sterilization method(s) for which the BI is intended, D‑value and z‑value (if applicable), lot number, expiration date, recommended storage conditions, and manufacturing date. The standard also requires accompanying documentation that includes resistance performance curves, detailed instructions for use, and a statement of conformity to ISO 11138-1. Accurate labeling ensures that users can select the correct BI for their process and interpret results reliably.
Implementation Highlights
Tip: Choose BIs that are validated for your specific sterilization cycle parameters. Consult the part of ISO 11138 that matches your modality (e.g., ISO 11138-2 for ethylene oxide) to ensure D‑value determinations align with your process conditions.
When implementing ISO 11138-1 into a sterility assurance program, the following points are critical:
- Qualification of suppliers: procurement should be from manufacturers who demonstrate compliance with ISO 11138-1 and provide certificates of analysis for each lot.
- Handling and storage: follow the manufacturer’s storage conditions (temperature, humidity, light) to preserve BI stability. Record storage area monitoring data.
- Use in validation: BIs are employed for qualification (IQ/OQ/PQ) and routine release testing. The standard recommends using BIs with a defined D‑value that is ≤ the specified sterility assurance level (SAL) margin.
- Training: personnel must be trained on aseptic handling, incubation, and interpretation of growth/no‑growth results according to the standard.
Warning: Do not use BIs that show evidence of physical damage, wetting, or past their expiration date. Such indicators can give false negative results, compromising sterility assurance.
Compliance Notes
Regulatory bodies including Health Canada, the U.S. FDA, and European notified bodies (under EU MDR and IVDR) accept ISO 11138-1 as a harmonized standard. Compliance is demonstrated through a quality management system (e.g., ISO 13485) that integrates BI testing into sterilization validation. Key audit considerations include:
- Traceability from BI lot number to sterilization cycle records.
- Evidence that BIs are stored and used per manufacturer’s specifications.
- Validation records showing D‑value and population meet the requirements of the relevant ISO 11138 part.
- Incident management for unexpected BI growth signals.
Best Practice: Establish a routine BI management program that includes incoming inspection, controlled storage, and periodic review of performance data. This supports robust sterility assurance and simplifies regulatory audits.
Critical: Never use a BI for a sterilization process for which it has not been designed and validated (e.g., using a steam BI in an ethylene oxide cycle). This will produce invalid results and could lead to product release errors.
Frequently Asked Questions
Q: What is the difference between ISO 11138‑1 and ISO 11135? A: ISO 11138‑1 specifies the general requirements for the biological indicators themselves, while ISO 11135 deals with the validation and routine control of ethylene oxide sterilization processes. They are complementary: BIs conforming to ISO 11138‑1 are used to comply with ISO 11135.
Q: How does CAN/CSA‑ISO 11138‑1‑17 differ from ISO 11138‑1:2017? A: CAN/CSA‑ISO 11138‑1‑17 is the identical Canadian adoption of ISO 11138‑1:2017. It includes a bilingual foreword and may reference Canadian regulations but contains no technical deviations.
Q: What is the significance of the D‑value tolerance (±20 %) for routine monitoring? A: The ±20 % tolerance means that the actual D‑value of a BI may be at most 20 % lower than labelled. This ensures the indicator is at least as resistant as declared, preventing over‑estimation of the safety margin. Users must factor this tolerance when setting cycle parameters.
Q: Are there specific requirements for self‑contained biological indicators (SCBIs) in this part? A: Yes, ISO 11138‑1 includes additional provisions for SCBIs, such as the requirement for the ampoule or inner tube to release the medium reliably without causing inhibition, and for the container to be optically clear for reading results.
© 2026 Technical Standards Article. For informational purposes only. Always refer to the official standard for compliance.