Sterile is a term we use a lot in the hospital, and there is a lot of confusion around it when we talk about the difference between sterile and disinfected. When you clean something in the hospital, it is in order to remove as many pathogenic organisms (the bugs that make you sick) as possible. But there are better and worse ways to do this: cleaning is the lowest level, disinfecting is higher, and sterilization is the gold standard that nothing can get any cleaner.
Image Credit: Pixabay
What Does it Mean to Clean?
When you clean something, it just means you get the dirt off. In doing so, you will clean some of the bacteria off in the process, but not all of them. When we take a shower or brush our teeth, we are just getting them clean. Likewise, when you wash dishes by hand, you are just getting them clean.
What Does it Mean to Disinfect?
When you disinfect something, it means that you clean it very very well, and that most of the bugs are gone. Usually, this requires some kind of disinfectant solution. In the case of doing your dishes, you can improve the cleaning of them by soaking them in bleach before you rinse them, or using a dishwasher at high heat. This cleans dishes really really well, but they are still not sterile (1).
Image Credit: Pixneo
For the human body, disinfection is the highest level of clean we can achieve. They do this in the hospital when they prepare a site for surgery and scrub it carefully with a disinfectant like iodine just before the surgery. Living tissue, like humans, animals, and plants can't be sterilized because it would kill the tissue.
Only inanimate objects can be sterilized, but generally only smallish objects, or objects where there is a special machine to sterilize them as it takes intensive cleaning or heat to sterilize. Therefore, things like floors can't be sterilized, or at least not very easily and need very specialized equipment to do so.
What Does it Mean to Be Sterile?
When something is sterile, it means that there is no higher level of something being clean. There are no organisms alive and even the spores and eggs have been killed. We discussed the Culture and Sensitivity Test on the last article, and when something is sterile, it means that nothing at all will grow in the petri dish (2).
And that requires intensive processing. In the hospital, they often use a machine called an autoclave. The autoclave is a machine used to process the instruments they use in surgery and many other equipment used on humans.
The autoclave puts these surgical instruments under high pressure, around 15 psi, and high temperature, around 121°C (249 °F) and maintains that for anywhere between 3 to 15 minutes (3) depending upon the instruments.
Image Credit: Wikimedia Commons
Large Industrial Autoclave
Because of the high temperatures and pressures involved, the types of things that can be autoclaved are limited, and often the lifespan of the instrument is limited too, so it can only be reused and autoclaved so many times before it has to be thrown away.
I hope this clears up the difference between disinfecting and sterilizing, and that anytime someone says they have sterilized something at home, they really just mean they cleaned it really well, or they disinfected it. Sterilizing at home is nearly impossible, but you can get things very clean with high temperature and disinfectant solutions. Dishwashers are excellent for this.
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A very clear and interesting explanation. I've often tried to explain this to the people in the context of body modification...i.e. why you shouldn't get your ears pierced with a plastic device which can't be sterilized (only "disinfected" as it were). Thanks!