This lesson will discuss what an autoclave is, how it works, and what it’s used for. We’ll also discuss the disadvantages of an autoclave, bacterial endospores, and how sterilization is important in the context of nosocomial infections.
If you had the choice of using a pressure cooker or a simple stovetop pot to cook something really quickly, you would certainly choose the pressure cooker. That’s because a pressure cooker seals your food and water in an airtight container. A source of heat, such as gas or electricity, is applied to the pressure cooker to heat it up.
Because neither air nor liquid can escape the pressure cooker, it heats up very quickly and therefore allows the food to be cooked much more quickly as well.
The Purpose of an Autoclave
This same exact process is used in something known as an autoclave, which is a device that uses moist heat – that is to say steam – under pressure to kill off all living microorganisms on any object or surface contained within it.The reason an autoclave uses steam is because steam is essentially the gaseous form of water. Water is able to transfer heat far more rapidly than dry air alone. I’m sure you know this if you’ve watched some survival show that mentioned the fact that people lose body heat far more rapidly in cold water than cold, dry air.
Well, now you know why.Anyways, the steam in an autoclave is placed under a lot of pressure. This is done because anything under pressure, be it steam or dry air, increases in temperature very quickly. The very high temperature in an autoclave quickly kills off any living organism in it, including bacteria, fungi, viruses, and even hardy bacterial endospores. That’s because extremely high heat will denature, or destroy, the proteins that make up the structure of a pathogen.
The reason an autoclave is so important is because it gets the pesky endospores, which are very tough, long-lasting, dormant forms of bacteria that I mentioned before. These spores are formed when conditions favorable to the bacteria’s survival, such as proper temperature and nutrition, become unfavorable.
You can liken these bacteria to hedgehogs. If everything is fine, the hedgehogs will walk around just minding their business. If they feel threatened, they curl up into a protective ball. That’s what these bacteria do – they curl up into a protective ball when they feel threatened.These endospores are so tough that they can resist common household disinfectants. What’s worse is they can survive being boiled for a very long time.
So, one way to ensure they are killed on something as important as surgical instruments, which will enter your body during an operation, is to put those instruments in an autoclave. That’s because the extremely high heat and pressure generated by the autoclave will be enough to kill even these hardy forms of bacteria.If they are not killed with proper sterilization and they enter your body by way of a contaminated surgical instrument during an operation, you may end up dying from a nosocomial infection, which is an infection acquired in the hospital.As a way to ensure that an autoclave reached a critical temperature high enough to kill these endospores and other microorganisms, test strip indicators are placed within it during an autoclaving procedure. If they change color, they indicate that the autoclave reached a temperature high enough to kill all life forms inside it.
You can liken this color-changing test strip to those cool heat-sensitive pencils. If you hold one for long enough, it will change color due to the heat coming off of your hand. These test strips use the same exact principle.
The Downside of an Autoclave
While an autoclave is an awesome way to get rid of all living microorganisms on an important object such as a surgical instrument, it’s not without its faults. For example, if an instrument isn’t cleaned well enough prior to being placed in an autoclave, the autoclave may fail.Imagine if there was a piece of tissue left attached to the surgical instrument prior to placement in the autoclave.
This would be akin to giving our hedgehog a little house under which it can hide to escape the heat and pressure that is trying to kill it. Likewise, microorganisms can use this macroscopic dirt and debris as a shelter to survive being autoclaved.In addition, you can logically understand that steam under pressure isn’t a great way to sterilize any type of material. Heat, steam, and pressure will do very little to high-quality German steel surgical instruments. However, if you were to put a paper object into an autoclave, it would be destroyed! Imagine taking a piece of paper into the shower with you.
All of that steam would cause it to wrinkle. Other objects, such as plastic, may melt under the intense heat produced by the autoclave. Therefore, other sterilization techniques, such as gas sterilization by way of ethylene oxide, can be used for moisture-sensitive equipment, or cold liquid sterilants can be used for heat-sensitive equipment.
Regardless of which method of sterilization is used, all living organisms, including endospores, which are very tough, long-lasting, dormant forms of bacteria, should be killed during the process of sterilization.
One way to kill these endospores is by using something known as an autoclave, which is a device that uses moist heat – that is to say steam – under pressure to kill off all living microorganisms on any object or surface contained within it.If an autoclave or some other form of sterilization isn’t used in the hospital, then you may acquire a nosocomial infection, which is an infection acquired in the hospital. Sometimes, these nosocomial infections can be deadly.
After this lesson is done, you should be able to:
- Describe what an autoclave is and how it works in sterilization
- Define endospores and understand why they are more difficult to kill than other bacteria
- Recall what a nosocomial infection is
- Summarize the use of test strips to make sure an autoclave is doing its job
- List some of the disadvantages of autoclaves