t
INFECTION PREVENTION & CONTROL
well as the disinfection or sterilisation. Documentary evidence of successful validation of the sterilisation process, together with the process monitoring data of each process and load, as well as the outcome of routine equipment checks and tests and evidence of required maintenance activities is also required. This summation of all of this information enables the user to make an informed decision that the load has been processed according to the predetermined process specification and can then release the load as disinfected or sterile. Parametric release is common practice in the medical device industry for the release of product batches sterilised by many processes, providing that the requirements of applicable sterilisation process standards are met. The same can be said of healthcare (hospital- based) practices, however it must also be appreciated that loads may be disinfected as a terminal step, as well, of course, as sterilised. Healthcare facilities may also process devices, such as endoscopes, that are used immediately after processing; this ‘point of use’ processing often dispenses with bacteria-impermeable packaging.
Alternatives to parametric release
If alternative methods of disinfection or sterilisation are used, other means of product release may be required, depending on the type of device, the company or the healthcare establishment practice, or the intended destination of the product – different regulatory agencies have different expectations for process monitoring. When parametric release is not used, the most prevalent method of load release is based on the use of biological indicators, where the load is released by non-growth of the biological indicator i.e. by evidence of non-viable biological indicators. The US Food and Drug Administration
(US FDA), as well as other specific regulatory bodies, will often place significant emphasis on the use of biological indicators; these indicators may be used for load release, as well as for the process validation that supports parametric release.
One of the pragmatic concerns of using
biological indicators to release processed loads is the time taken to incubate the biological indicator in order to attempt to grow any living (viable) microorganisms. Following exposure to the disinfection or sterilisation process, biological indicators must be cultured as soon as possible after the process in suitable media and under appropriate recovery conditions, as specified by the biological indicator manufacturer. The problems of aseptically handling biological indicators can be much mitigated by the use of self-contained biological indicators (SCBIs). These SCBIs consist of a spore-inoculated carrier and a separate sealed container with the microbiological recovery media, all packaged together within an ampoule or container. This packaging also contains a sterilant-permeable filter that allows the SCBI to be used without any disassembly. After processing, the recovery medium is released from its sealed container to allow it to be in contact with the spore- inoculated carrier, and the biological indicator can be incubated as a whole unit. Historically, biological indicators needed to be incubated for up to 7 days to determine viability (growth). This detection of growth of the reference microorganism is typically by the presence of turbidity (or cloudiness in the media); this may be quite difficult to see in a SCBI format, hence commercially available SCBIs typically include a pH indicator within the recovery media. As microorganism germination and subsequent growth occurs, there is an associated drop in pH as the microorganisms digest the recovery media. This drop in pH causes the pH indicator to change colour,
NOVEMBER 2019
hence showing microorganism growth, and a positive (i.e., growth) result. Biological indicators are now available that use the presence of fluorescence to determine microorganism growth; these biological indicators have a significantly shorter incubation time than the reference period, and the fastest biological indicators have reduced the incubation time down to as little as 20 minutes. This is achieved by adding a non-fluorescent alpha-glucosidase substrate to the recovery media; as the microorganisms germinates, the substrate is metabolised by the microorganisms, resulting in formation of a fluorescent compound. This fluorescence can be detected using purpose-made incubators that incorporate fluorescent detection capabilities.
Other load release factors to consider
Regardless of the method of load release, there must be a documented course of action to be taken for both approval and rejection of devices or product. As well as the specific requirements for load release, there must be, for example, obvious means to identify load items that have been appropriately released, from those that have either not been released or have been quarantined due to a processing failure. The most obvious example for identification of released product is by segregation of processed/sterilised products from non-processed/quarantined products. This can be addressed both by the use of pass-through (double-ended) washer- disinfectors and sterilisers, as well as the use of process chemical indicators that indicate that loads have been exposed to a disinfection
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