The Principles of Medical Device Decontamination

gradient and try to get penetration into the vegetation. This is not always successful and may necessitate surgical intervention, removal of the diseased heart valve and implantation of a prosthetic device.

With implanted medical devices, many have lumens used to hold open natural tubes and are implanted to allow the passage of fluids. Examples include urinary, biliary and arterial stents etc. They will pick up debris from the different body fluids that pass through the natural tube and are also at risk of acquiring bacteria. These can find a niche and establish a colony, which with time can escape and establish new infections at a remote site. The difficulty with any implanted device is the device itself does not have a blood supply and therefore getting antibiotics into the biofilm is difficult and while an infection can be suppressed with antibiotics, killing those embedded deep in the biofilm is essentially impossible and eradication of this source of infection requires removal of the device. This will not be an easy decision and will require the clinical team to risk assess what the best course of action is for the patient and then discuss options. For the decontamination scientist, biofilms can similarly be associated with hinged joints and complicated shapes in surgical instruments and the multiple channels associated with various types of endoscopes. Such biofilms will develop over time if the device is not adequately cleaned. High temperature steam sterilisation is effective at killing bacteria but when present in biofilm matrices, processes can be compromised. Similarly, the presence of biofilm might prevent the denaturation of proteins and prion risk may remain. Where chemical decontamination is undertaken as in endoscopy, if the biofilm cannot be removed by cleaning, then the chemical decontaminant is unlikely to penetrate the biofilm and bacteria will survive and have the potential to be passed to a future patient.

The Challenge for the Decontamination Scientist

There is a variation in the susceptibility of the different infectious agents, which is illustrated in Table 1.2:

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