The Principles of Medical Device Decontamination

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Microbiology

Micro-organisms pervade all parts of our world, including very harsh environments but for decontamination, we are interested in those that live within the environments we occupy, the food and water we ingest and within and on our bodies as well as the bodies of animals we may contact. The human body is home to a staggering number of microorganisms living in us and on us; around 8 trillion more organisms than human cells in the body 1-3 . These include recognised potential pathogens, organisms that are commonly associated with infection as well as organisms that are normally considered harmless. The latter are considered normal flora but even these can be associated with ill-health. What is becoming very evident is that good health is associated with a well-balanced microbiome, a more recently adopted term for normal flora. A foetus in-utero is normally free of any organisms and begins to acquire them from the moment their mother’s uterine sac is breached and they begin their journey down the birth canal or delivery by Caesarean section. The bulk of our normal microbiome is gut-associated and as any new parent discovers, in the initial period of their child’s life the yellow, sweet-smelling faeces is very different to their own. This is related to the initial milk-based feed which the baby has for the first few months of life before being weaned, when the faeces gradually become darker and more like their parents 4 . What this illustrates is how in health, each of us lives in harmony with our microbiota, and the microbiota is subject to change over time as a result of our lifestyles and health status. As noted, the organisms include some that are considered pathogenic. However, in a diseased state, a person who has a disrupted microbiota and may be immunocompromised, can become infected with organisms that are normally considered non-pathogenic. Most infections will be derived from our own microbiota and when associated with interventional procedures, breach the first line of our immune defences.

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