Autoclaves and Moist Heat Sterilization: Use With Surgical Tools

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  • 0:38 Purpose of an Autoclave
  • 1:55 Bacterial Endospores
  • 3:55 Downside of an Autoclave
  • 5:18 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov
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.

Pressure Cooker

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.

Bacterial Endospores

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.

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