Prior to beginning routine sterilization, a product with a sterile claim needs to complete a validation process to ensure the Sterility Assurance Level claimed is met. Normally, A 10-6 SAL, or greater (i.e. 10-6, 10-7, etc.) is used for:
- Products intended to come into contact with breached skin or compromised tissue
- Invasive products that enter normally sterile tissue
- Products with claims of sterile fluid pathways
- Surgically implanted devices
- Components used in aseptic processing
A 10
-3 SAL, or greater (i.e. 10
-4, 10
-5, etc.) is used for:
- Products not intended to come into contact with breached skin or compromised tissue
- Topical products that contact intact skin or mucous membranes
- Products that cannot withstand a 10-6 SAL process
Sterilization validation studies must document that the product attains the re- quired SAL after exposure to the proposed process. In the industry, sterilization validation is generally evaluated by, first, determining the qualitative and quan- titative bioburden (the type and number of viable microorganisms present on the device just prior to sterilization) after the manufacturing process, then, studying the rate of killing using fractional-run sterilization studies and, finally, deducing the time required to achieve a 10-6 SAL. Validation studies must be done on
product samples prepared under actual manufacturing conditions and exposed to
the sterilization process under its final packaging configuration.
Two methods are used in validation:
Bioburden method:
Bioburden: Population of viable microorganisms on a product. In the context of irradiation sterilization, bioburden is determined immediately prior to sterilization. The unit of measurement is CFU: Colony Forming Unit.
Broadly speaking, and validation consists of three steps: Installation Qualification (IQ), Operational Qualification (OQ) and Performance Qualification (PQ). The IQ and OQ portions are often performed ahead of time by the contract facility and provided in the form of a commissioning package to the customer. The performance qualification demonstrates that the sterilization equipment consistently operates in accordance with predetermined criteria and that the process produces product that is sterile.
Over-Kill Method:
The overkill method is the most commonly used method for gas/vapor phase sterilization modalities. This method uses a biological indicator with a population of 106 of the most resistant organism (MRO). A fractional (Sub-lethal) cycle(s) is run to determine the D-Value of the product in a given sterilization process. The D-Value determines the amount of time needed to kill one log of the MRO. The half cycle is determined my multiplying the D-Value determined in the fractional cycle by six, plus a safety factor. The calculated half cycle is then tested to verify that a six log reduction is achieved in all locations within the load. A full cycle is double the time/injection of a half cycle. This provides you with a SAL of 10-6 or 12 log reduction.
