DECONTAMINATION & STERILISATION
Decontamination test methods –new thinking
David Woods, Operations manager at T.E.S.T. Medical, a specialist in the testing, installation, maintenance, and examination of decontamination and sterilisation equipment, takes a look at some of the latest technologies for testing laboratory samples taken from Endoscopy Decontamination and Sterile Services Departments to minimise the risk of transmission of harmful bacterial pathogens to patients during procedures.
Tests can be critical in detecting failures of the process, and help the user detect things that can’t be seen by eye; proteins, bacteria, and residual process chemicals. For any given test requirement there may be several methods for the user to choose between, and without having knowledge of the science involved, or consulting an AE(D), it can be easy to make the wrong choice. Off-the-shelf test kits are promising faster and easier results, and it can be tempting to move away from the more traditional testing methods that can be carried out in-house, especially when cost is a determining factor.
The current method of testing for Mycobacteria is membrane filtration and 28-day incubation.
Most of the time these advances are positive, and can save vital time and money for the Trust, but how would a user know they are getting the same quality of test? This is a key consideration, as any contamination, be it protein or microbial, needs to be flagged up accurately, and in a way that is compliant with the guidance. Historically, there have been several examples where a method of testing has become popular ‘in the field’ due to ease or cost, only to be found ineffective when guidance changes. The ideal testing method would be performed in situ, low-cost, and would
provide instant and reliable results. Discussed below are some examples of the alternative testing methods that have been employed in the last decade or so. These fulfil many of the above criteria. However, the user should be aware that no test method is perfect, and that they may be sacrificing vital elements of the detection method to save time or money. Understanding the science behind the tests is key to making the right decision for the department or process.
A quicker way to detect bacteria: PCR Traditional microbiology has always been limited by the speed that bacteria, yeasts, or fungi, grow, as the way that they are detected is visual; individual bacteria in a water sample need to grow into a colony of millions that can be seen unaided by the microbiologist’s eye. These microorganisms can have different growth rates dependent on the species, and can take anywhere between 24 hours and 28 days to grow in an incubator. Therefore, if you are looking for species
of Pseudomonas, this may be as quick as 24 hours, but Legionellae are slower and take up to 10 days to grow into colonies. Species of the Mycobacteria genus are slower still, and a 28-day incubation is needed to ensure that each has had enough time to grow. These agar plate- based methods are considered the gold standard of microbiology; they are trusted and well understood.
This article, entitled ‘Alternative test methods for washer disinfectors’, first appeared in April this year in a special Decontamination & Sterilisation supplement published by HEJ’s sister magazine, The Clinical Services Journal. HEJ thanks the magazine’s editor, and the author, for allowing its reproduction here in slightly edited form.
A faster and more direct method would be infinitely more useful for the modern endoscopy or CSSD department. However, the trouble with detecting bacteria is that in trying to directly detect small numbers of bacteria, any ‘signal’ generated is going to be too weak to be picked up by an instrument or detector. Waiting for them to multiply into bigger numbers by themselves is slow, and requires the exact right growth conditions. A way to speed this up is to specifically grow or ‘amplify’ small parts of the bacteria that can be more easily and quickly detected. This is the realm of molecular biology, which is a branch of
October 2019 Health Estate Journal 133
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