The Principles of Medical Device Decontamination

Micro-biocidal performance of disinfectants

Different microorganisms will have different susceptibility to the various biocides used to formulate disinfectants. For example, the lipopolysaccharide cell wall in some (gram negative) bacteria inhibits the penetration of some biocides, making the microorganism more resistant to that disinfectant.

Many bacteria form associations with surfaces known as biofilms. These biofilms make penetration of biocides much more difficult, even though it can be argued that adequate cleaning prior to disinfection would remove these biofilms.

Over the last few decades, the use of aldehydes as a biocide has been questioned because of aldehyde’s ability to fix proteins and make subsequent removal extremely difficult. Fixed protein can also be more difficult to remove to achieve a clean medical device, however there are generally considered better biocides that avoid the disadvantages of aldehydes. Peracetic acid has been used for many decades for disinfection (and sterilisation) of medical devices. Peracetic acid has excellent biocidal performance, even at comparatively low concentrations, a feature attributed to its strong oxidising potential, and no harmful decomposition products, and excellent water and lipid solubility. Given how potent peracetic acid is as a biocide, it has remarkable material compatibility, especially with stainless steel, anodised aluminium and many polymers.

Disinfectant parameters

Disinfectants will only be effective at destroying microorganisms if used at the correct concentration, temperature and exposure time. In addition, there may be manufacturer instructions regarding interfering substances. Using a disinfectant at a higher concentration, a higher temperature, or a longer contact time will almost certainly increase its biocidal effect, but equally could introduce material compatibility and biocompatibility concerns, too. Material compatibility relates to damage or changes to the materials of construction, such as corrosion, for example, and biocompatibility relates to the compatibility of the device with the patient; a higher disinfectant concentration, for example, could result in unacceptable residual disinfectant on or in the device after processing.

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