Of Mice and Medical Devices – Cleaning, Disinfecting and Sterilization

Imagine that you manufacture medical devices. As a final step, the devices are placed in an autoclave; and sterilized using an approved, validated method. Next, you open the autoclave. What do you see? A mouse on top of the devices!

YUK! The mouse may have been sterilized. The devices may have been sterilized. However, you darn well better physically remove the remains of the mouse from the devices.

Lots of people (even some health care professionals) sort of lump together cleaning and sterilization (or cleaning and disinfection). Cleaning and disinfection are different activities. Both are important. Each has a different purpose. The story about the sterilized mouse illustrates the difference between cleaning and sterilization (or disinfection) and shows that if you don’t clean effectively first, you can’t disinfect or sterilize effectively.

Sterilization and disinfection are processes that kill organisms. Sterilization is generally thought of as a process that kills or eliminates “all” forms of life. I myself tend to take issue with absolutes like “all.” That’s a bit like saying “100% clean” or “100% safe.”

The EPA tests and lists disinfectants, products or chemicals or processes that have killing properties. In terms of surfaces, discussion of disinfection efficacy is related to the amount of contact time of the disinfectant with the surface. It is also related to accessibility of the disinfectant to the surface. If there were a mouse on top of a hard surface, it would be highly unlikely that the disinfectant could access the surface.

We have to remember that a sterilized dead mouse is still dirt; it’s still a source of food. That’s why cleaning prior to disinfection (and prior to sterilization) is essential. Cleaning is physically removing soil or dirt – dead, alive, biobased, synthetic – and doing this whether or not the soil is damaged or killed. That means removing oils, grease, fingerprints, metalworking fluids, lapping compounds, food residue, bacteria, mice – whatever.

Cleaning, disinfection, and sterilization are all processes, not just chemicals. A cleaning process consists of washing, rinsing, and drying steps. Cleaning any surface requires thought and planning. Certainly, removing visible residue prior to disinfection is essential. Is it enough? Disinfection is not forever. If you are a manufacturer, think of it as an ongoing issue – like rust prevention.

Be aware of the process of cleaning all surfaces. We might need to consider how the cleaning process could support life. Living things need water and food. Repeatedly pouring a cleaning chemical onto a surface without rinsing it off may result in a residue buildup that, in some instances, could support the growth of life forms. The residue might not be readily visible; and the residue might not provide food for a mouse. But it could provide food for a microbe.

Here’s another way to think about cleaning and disinfection. If a child plays in the mud and skins her knee, the first thing Dad or Mom ought to do is wash away the mud and debris. Next comes the antibacterial ointment, next the bandage – and maybe finally a lollipop!

References:

Sterilization: Cleaning
https://www.cdc.gov/oralhealth/infectioncontrol/faqs/cleaning.html

Clean Before Sterilization (Disinfection), Alconox TechNotes
http://technotes.alconox.com/industry/healthcare/tattoo-cleaning-clean-before-sterilization/