Sterility | EUROLAB

What Is Sterility?

The sterility test investigates whether viable microorganisms are present in the sterilised product by incubation in culture media. It has an important limitation: the test is performed on a statistical sample and does NOT PROVE sterility; sterility assurance is primarily achieved through validation of the sterilisation process.

Purpose of Sterility

The purpose is to produce supporting evidence of the product's sterility, in sterilisation-process validation studies and in routine monitoring.

Which Products Is Sterility Applied To?

Sterile single-use medical devices
Implants
Surgical sets and drapes
Syringe and infusion sets
Sterile-packaged wound-care products

In Which Sectors Is Sterility Used?

Medical DeviceHealthcarePharmaceuticals

Standards Related to Sterility

ISO 11737-2sterility test in sterilization verification test
ISO 11737-1determination of microbial load in medical devices test
EP 2.6.1
USP <71>
ISO 11135
ISO 11137
ISO 11607end product sterile barrier packaging test

Sterility Conditions

Method: Membrane filtration or direct inoculation; chosen according to the product
Culture media: Media suitable for aerobic and anaerobic growth are used
Incubation: At the temperatures and for the duration defined in the pharmacopoeia (commonly 14 days)
Environment: Aseptic work within a classified cleanroom or isolator

Equipment for Sterility

Isolator or Grade A cleanroom cabinet
Membrane filtration unit
Incubators (at different temperatures)
Autoclave and culture-media preparation infrastructure

Sample Requirements for Sterility

The sterile product together with its final packaging
The number of specimens is determined according to the pharmacopoeia and batch size
The sterilisation method and batch information must be stated
Packaging integrity must be intact

Duration of Sterility

The incubation period is typically 14 days; the duration extends if a method-suitability (bacteriostasis/fungistasis) study is being performed for the first time.

Sterility Procedure

1A method-suitability study is performed, or reference is made to an existing study.
2The specimen is removed from its packaging under aseptic conditions.
3Membrane filtration or direct inoculation is applied.
4Culture media are incubated at the defined temperatures.
5Growth is observed regularly throughout incubation.
6If growth is observed, the microorganism is identified and the source is investigated.
7Results are reported.

Sterility Acceptance Criteria

The acceptance criterion is that no growth is observed in any medium at the end of the incubation period. If growth occurs, it is investigated whether this is genuine contamination or contamination during the test.

Evaluation of Results

The result is interpreted together with sterilisation validation data. A negative test result does not prove sterility; the sterility assurance level (SAL) is demonstrated through process validation.

Sterility Report

Applied pharmacopoeia/standard and method
Specimen description, batch and sterilisation method
Reference to the method-suitability study
Culture media, incubation conditions and duration
Growth observations and result

Accreditation

EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.

Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.

Scope and authorisations

Related Regulations

MDR (EU) 2017/745
ISO 11135 / ISO 11137 sterilisation validation

Medikal Cihaz Testleri — What Does This Testing Field Cover?

The section below describes the field that the Sterility test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.

Medical device testing shows that a device is safe for the patient and the user and maintains its intended performance. In this family safety is not only about avoiding harm; a device failing to perform its expected function is also treated as a risk. A monitor missing an alarm or a pump delivering the wrong dose is directly a patient safety event.

At the centre of the field is RISK MANAGEMENT, and this is what sets medical apart from other sectors. The risk management process run under ISO 14971 also determines which tests are required. The test list is not copied from a table of standards; it is derived and justified from the device's intended use, the nature and duration of patient contact, the use environment and foreseeable misuse.

Assessment consists of several separate bodies of work, each with its own set of standards. Biocompatibility runs through the ISO 10993 series, electrical device safety through the IEC 60601 series, sterilisation through ISO 11135/11137/17665, packaging through ISO 11607, software through IEC 62304 and usability through IEC 62366. The quality system (ISO 13485) is the framework that binds these together.

Which tests are required is determined by the device's CLASS and its MODE OF CONTACT WITH THE BODY. A product in brief contact with skin and an implant entering the bloodstream do not go through the same test set; the scope is set by a biological evaluation plan prepared under ISO 10993-1. That plan justifies in writing which endpoints are required and why the others are not.

Packaging and sterilisation are taken as seriously as the device itself in this field. For a sterile device the packaging is not a transport container but the barrier that maintains sterility; if the barrier is breached, the device is no longer sterile. Packaging processes are therefore validated and shelf life is supported by real-time ageing data.

For devices containing software, assessment shifts from testing towards PROCESS assurance. IEC 62304 defines which development and verification steps must be followed according to the safety class of the software; the evidence is the traceability of the development process. Testing software does not make it safe — the process record does.

The clinical side is a separate column of the technical file. Test reports show that the device is technically safe; clinical evaluation establishes that the device delivers the intended clinical benefit and that the benefit-risk balance is acceptable. Neither replaces the other.

Method groups in this field

Biocompatibility
Cytotoxicity, irritation, skin sensitisation, systemic toxicity, haemocompatibility, genotoxicity and local effects after implantation. The required endpoints are set by the ISO 10993-1 plan.
Electrical device safety
IEC 60601-1 basic safety and essential performance; EMC, alarm, usability and environmental requirements through the collateral standards.
Sterilisation validation
Validation of sterilisation processes by ethylene oxide, radiation or moist heat; bioburden and sterility assurance level studies.
Packaging
Integrity of the sterile barrier system, seal strength, distribution simulation and shelf-life studies.
Microbiological tests
Bioburden determination, sterility testing, bacterial endotoxin and, where required, carrier validation studies.
Software and usability
IEC 62304 life cycle evidence and use-error focused evaluation under IEC 62366.

Commonly confused in this field

Cytotoxicity alone is not evidence of biocompatibility; the required set of endpoints is determined and justified according to ISO 10993-1.
An ISO 13485 certificate does not confer CE marking; classification under the MDR, the technical file and the notified body process run separately.
Accelerated ageing does not replace real-time ageing; a shelf life claim is supported by real-time data.
A change of material (supplier, pigment, sterilisation method) may require the biological evaluation to be repeated; it is not a silent change.
An assessment made without the collateral and particular standards for IEC 60601-1 is incomplete; which -1-x and -2-x standards were applied must appear in the report.
In vitro diagnostic devices fall under the IVDR rather than the MDR, and laboratory equipment is often on the IEC 61010-1 side.

Which decisions these results support

MDR/IVDR technical file and notified body assessment
Completing the biological evaluation plan
Sterilisation and packaging validation
Determining shelf life and storage conditions
Determining the scope of reassessment after a design change

Related Tests

Frequently Asked Questions About Sterility

Does the sterility test prove that my product is sterile?

No. The test is performed on a limited number of specimens and has a low probability of detecting low-level contamination. Sterility assurance is achieved through validation of the sterilisation process under ISO 11135 or ISO 11137; the sterility test is a supporting check.

Why is a method-suitability study necessary?

Antimicrobial substances migrating from the product can suppress growth in the culture medium; in that case, even a contaminated product gives a negative result. The suitability study shows that the product does not inhibit growth, and is a prerequisite for the test's validity.