What you will learn
By the end of this topic, you should be able to distinguish cleaning, disinfection and sterilisation, select a compatible sterilisation approach, explain validation and routine control, and connect bioburden, packaging, suppliers and change control.
Begin with the clinical and microbiological need
The required microbial state depends on intended purpose, contact, use pathway and infection risk. Cleaning removes contamination; disinfection reduces viable microorganisms to a defined level; sterilisation uses a validated process to render a product free from viable microorganisms. The applicable claim and method must be explicit.
Sterility is assured by a validated and controlled system. It cannot be demonstrated by testing a few finished units.
Select a method compatible with the whole product
Moist heat
Effective and well understood, but unsuitable for products unable to tolerate heat or moisture.
Ethylene oxide
Useful for complex, temperature-sensitive devices; requires control of process residues and aeration.
Radiation
Gamma, electron-beam or X-ray methods require dose establishment and material compatibility.
Other methods
Dry heat, vapourised hydrogen peroxide and other approaches need method-specific evidence and regulatory acceptance.
Evaluate materials, electronics, drugs, packaging, geometry, lumens, lubricants, functionality, residuals and repeat exposure. A method that achieves microbial inactivation but damages performance is not suitable.
Control contamination before sterilisation
Sterilisation is not a substitute for controlled manufacturing. Product bioburden and, where relevant, bacterial endotoxin depend on materials, suppliers, environment, handling, hold time, water systems and cleaning.
- Define contamination controls from incoming material to sealed packaging.
- Establish representative sampling locations and times.
- Use suitable recovery, enumeration and identification methods.
- Set alert and action levels with justified responses.
- Investigate shifts in count or organism type.
- Control time between production, packaging and sterilisation.
Validate the sterilisation process
Worst cases must represent the factors that make sterilisation or product compatibility most difficult. The product, packaging and load used for validation should be traceable to routine production.
Control every routine cycle or batch
Routine release uses the parameters and monitoring defined by the validated method. This may include physical records, chemical indicators, biological indicators, dosimetry, bioburden or parametric release, depending on the process and applicable standard.
Review cycle completeness, alarms, deviations, load identity and equipment status before release. Maintain calibration, preventive maintenance and requalification. Trend data to detect gradual process change.
Retain control when sterilisation is outsourced
The legal manufacturer remains responsible for requirements and evidence. Agreements should define validated loads, product families, transport and storage, processing windows, release data, deviations, change notification, requalification, records and audit access.
Apply the supplier principles in MTL-125 — Supplier and Outsourced-process Control.
Assess changes across the complete system
Changes to materials, geometry, packaging, suppliers, manufacturing site, bioburden, load pattern, steriliser, cycle parameters or shipping can affect validation. Review cumulative changes as well as individual ones, and define when requalification or new compatibility evidence is required.
Common misconceptions
“Sterility testing proves the batch is sterile.”
Sterility is a process-based assurance; limited end-product sampling cannot prove the absence of viable microorganisms throughout a batch.
“The contract steriliser owns the validation.”
The supplier performs defined activities, but the manufacturer retains accountability for device requirements and evidence.
“A validated cycle never needs review.”
Routine data, product changes, equipment changes and periodic requalification determine whether the validated state remains justified.
Authoritative external references
- FDA — Sterilization for Medical Devices
- ISO 11135:2014 — Ethylene oxide sterilisation
- ISO 17665:2024 — Moist heat sterilisation
- ISO 11607-1:2019 — Packaging for terminally sterilized medical devices
Select the current method-specific standards and regulatory guidance applicable to the device and market.
Sterility is the outcome of a controlled system
Connect product design, contamination control, packaging, validated processing, routine monitoring and change control into one microbial assurance strategy.