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Fact Sheet: Overview of Sterility Testing Methods

Posted 11th October 2018 by Wickham Micro

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•    In the British Pharmacopoeia sterility testing was first mandated in 1932 however, before this there were other regulations for specific tests and products specified under the Therapeutic Substances Act.
•    Sterility testing is absolutely essential for safe pharmaceutical & medical devices. The sterility test assesses whether or not the products contain microbiological contamination, which could be harmful in human health.

Sterility Testing Overview:
•    Sterility testing is a vital regulatory requirement that manufacturers of pharmaceutical or medical devices must adhere to in order to assess the safety of their product.
•    Sterility testing can be conducted by several methods including: Steritest®, membrane filtration (MF) or direction inoculation (DI).
•    Steritest® or MF methods are typically used on products that are filterable in some way.
•    Steritest® uses a totally enclosed filtration system giving a very high assurance of integrity of the test environment. This sterility test method minimises the risk of false positives from adventitious contamination as there are no open containers, membrane manipulations, or media transfers.
•    Products that cannot be filtered can alternatively be tested by the DI method. This typically includes products such as medical devices. The DI method involves testing a certain number / percentage of the batch for sterility depending on the type of product and the overall batch size.
•    The test looks for the presence or absence of microbial growth in appropriate test broths (aerobic and anaerobic) after a 14-day incubation at the corresponding incubation temperature. Growth indicates a sterility failure i.e. microbial contamination whereas no growth or a clear broth indicates the product is sterile.

In the Lab / at Wickham Micro Ltd:
•    Sterility testing must be performed aseptically in an isolator or cleanroom environment. Whilst laminar flow cabinets can be used for sterility testing our technicians would normally use an isolator that can be fully decontaminated to prevent cross-contamination from the environment.
•    At WLL, our facilities operate a Grade D (ISO class 7, class 10,000) compliant cleanroom, which houses four large capacity half-suit isolators.
•    We sanitise our isolators using hydrogen peroxide vapour to enhance the integrity of the test environment. This offers a level of test assurance that simply cannot be matched by the use of laminar flow cabinets.
•    We offer Steritest®, MF and DI methods for sterility testing and have significant experience in dealing with various product types such as the following:
o    Medical devices (dressings, catheters and tubing, medical plastics, contact and intraocular lenses, implant devices, etc.)
o    Sterile fluids (irrigation, dialysis solutions, ointments, creams, vaccines antibiotics, total parenteral nutrition solutions, controlled drugs and high potency or cytotoxic preparations, etc.)
•    Method suitability must first be performed on products to determine if they present any antimicrobial properties that could affect the test itself. This may require additional washes, different diluents or methods be used to ensure a compliant test can be performed.
•    We test to both the harmonised pharmacopoeial standards (Ph Eur, ESP and JP) and the ISO series relevant to medical devices (BS EN ISO 11737).

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